Another interesting project was proposed by the Cuban arti(vi)st Tania Bruguera. The "School of Integration", realised during the festival "Home" (2019), was conceived as a temporary school to experience other types of knowledge, history, skills, beliefs and customs, as well as unexpected connections between them and those of the hosting country. Through music, oral poetry, culinary exchanges, artisan workshops, etc., during the 10 days of the festival, the "School of Integration" activated a two-way model for teaching, in which the "foreigner guests" introduced the 'local hosts' to their traditions. Therefore, the role reversal between those who usually have to adapt to the host culture and those who are part of the host society was among the most interesting and innovative aspects of this project, challenging the usual political understandings – those of unidirectional "integration". The lessons were all very different from each other: the Eritrean poetess, Ribka Sibhatu, gave a lesson about contemporary Eritrea, Larysa taught the Ukrainian rite of drawing and painting Easter eggs, while another association transformed the DAMSLab's classroom – an artistic space managed by the University of Bologna – into an African tailoring shop, guiding the audience to experience the sewing machines and beautiful textiles with colourful designs. In so doing, the "School" encouraged a dialogue between ethnic minorities and inhabitants who met daily for an hour, with the aim of sharing their stories and producing "practices of difference" (Semi et al., 2009), suggesting that cultures are not coherent systems but are fuid and infuence each other. Therefore, the "School" attempted to deconstruct "all social assertions of difference, highlighting its fortuitous, open-ended, unstable nature as it appears" (2009, p. 67). As a consequence, this project intervened in terms of audience development at a dual level. The frst refers to "Extended Marketing", as it involved those audiences who are usually excluded from cultural activities. The second refers to "Outreach" by bringing participatory artistic experiences within an academic space, thus contributing to its temporary re-signifcation. As Tania Bruguera explained:

School of Integration works on the intersection between art and pedagogy. Here, again, the project takes possession of a structure of power. Through my artistic work I always strive to activate processes from which local communities can beneft, so that they can become selfsustainable after passing the torch.

These two projects showed, therefore, how arts and culture can become an alternative form of participation (Merli, 2002). By selecting the stage venue outside the traditional places where culture is produced, involving the centre as well as the periphery, institutional places but also streets and reception centres – and encouraging the participation of different people – the project included and amplifed the voice of those who are usually not heard. This was an experiment which showed how the performing arts can have both an aesthetic and a political value (Martiniello, 2016; Paltrinieri et al., 2020).

#### **12.6 Conclusions**

The project "Atlas of Transitions" displayed the transformative power of cultural production. It aimed to deconstruct Eurocentric narratives, promoting mutual recognition (Camozzi, 2016) and spaces of collective participation. Hence, the artistic interventions represented physical spaces and processes of knowledge that developed plural and various forms of conviviality.

First, the methodology of action research adopted in the project sustained continuous forms of social relations that gradually transform into learning relationships (Eikeland, 2006). Thus, the artistic workshops and events were able to promote forms of encounter and dialogue, supporting intercultural and intergenerational diversity as an inescapable source for the creative process. By creating plural and fexible structures, they involved various accounts and critiques, rather than a single

authoritative interpretation (Zapata-Barrero et al., 2017). From this perspective, the knowledge of both the inquirer and the inquired was not excluded from an understanding of how knowledge was generated (Susman & Evered, 1978, p. 586).

In this sense, action research was concerned with change, not only at an individual but also at a collective level (Brydon-Miller et al., 2003). As the examples presented in this contribution have shown, a collective refection on the modalities of deconstructing distorted imaginaries of migration through unconventional language and practices was the primary means to promote a change in these imaginaries (Foster, 1972; Moralli et al., 2020). In so doing, the project "Atlas of Transitions" has challenged the social conventions and power relationships that lay behind the ways in which different people were represented. Hence, the cultural activities were not only characterised by an aesthetic value but also by a strong political meaning. In this sense, they promoted a "narrative of change" (Wittmayer et al., 2019) capable of fghting "against pre-existing cultural and institutional narratives and the structures of meaning and power that they transmit" (Davis, 2002, p. 25).

Secondly, thanks to a collective effort in audience development, regarded not only as a possibility to broaden the audience of cultural productions but also as a form of direct participation of migrants, the project amplifed their voices as individual subjects (Papastergiadis, 2012). As a result, the project became a space of dialogue, resistance and activism.

Drawing on these results, new research paths emerge. First, further studies are needed in order to understand the access to cultural production and consumption by migrant communities in the Italian context. While the number of artistic and cultural projects developed by migrants is increasing, artists encounter various diffculties in putting into action processes of counter-racialisation in contemporary Italian society (see Chap. 6 in this volume). Moreover, it would be useful to further investigate the transformative power of culture in terms of political participation and citizenship.

**Acknowledgments** This chapter was based on the project "Atlas of Transitions. New Geographies for a Cross-Cultural Europe", co-fnanced by the European programme "Creative Europe" (2017–2020). For more information about the activities, the partners and the stakeholders involved, please visit: http://www.atlasoftransitions.eu/.

#### **References**

Ahmed, S. (2004). *The cultural politics of emotion*. Routledge.

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

## **Chapter 13 Youth in the City: Fostering Transcultural Leadership for Social Change**

**Matteo Dutto, Francesco Ricatti, Luca Simeone, and Rita Wilson**

#### **13.1 Introduction**

*Youth in the City* (YITC) is an international, multidisciplinary research initiative that promotes digital participatory action research (PAR) with multicultural and migrant youth as an effective response to the xenophobic content that readily spreads on social media and in public discourse. We work with young people across the world to reclaim urban space and imagine shared transcultural futures through participatory mapping, co-designed creative interventions and digital storytelling. In 2019, we conducted the frst project in Prato, Italy. Home to over 120 different nationalities (Uffcio di Statistica, Comune di Prato, 2020), the city is one of the most studied cases of multiculturalism in Italy and has become, over the years, "a European 'hotspot' for migration and integration issues" (Baldassar et al., 2015, p. 8). It is also a place where we witness frst-hand how migration fows generate "transcultural edges" – that is, new and innovative spaces – "where unevenly

M. Dutto (\*)

F. Ricatti College of Arts and Social Sciences, The Australian National University, Canberra, ACT, Australia e-mail<EMAIL_ADDRESS>
L. Simeone Department of Architecture, Design and Media Technology, Aalborg Universitet, Aalborg, Denmark e-mail<EMAIL_ADDRESS>
R. Wilson School of Languages, Literatures, Cultures and Linguistics, Monash University, Melbourne, VIC, Australia e-mail<EMAIL_ADDRESS>
Monash University European Research Foundation, Prato, Italy e-mail<EMAIL_ADDRESS>
distributed different cultural systems, representations, imaginaries converge and give rise to new transcultural practices" (Vanni, 2016, p. 7). Against this background, we collaborated with local high schools to conduct a participatory action project with 48 high-school students, many of whom had migrant backgrounds. Entitled *La Nostra Prato* (Youth in the City, 2021)*,* the project applied the YITC methodology to develop creative processes that could foster leadership skills and an enthusiasm for social change among this culturally diverse group of young people, who have the potential to play a vital role in bringing together their communities, fostering social cohesion and building socio-economic resilience. Their lived experiences across different cultures, languages and social contexts provide the potential for great leadership within increasingly complex, transcultural and multilingual societies. Recognising that such potential is often hindered by a combination of factors, including a lack of confdence and different forms of discrimination at the intersection of class, ethnicity, race, gender, sexual orientations and physical abilities, we sought to redress this imbalance by providing an opportunity for multiethnic youth to engage in a range of digital creative interventions that would enable them to have a say on issues that matter to them.

Using the *La Nostra Prato* pilot project as an example, we suggest an alternative model for understanding and engendering social and cultural change; one that focuses on the transdisciplinary and transcultural creative practices and processes through which young people in superdiverse urban contexts develop leadership skills. In empowering youth through participatory-action workshops and digital creative interventions and in giving their perspectives enhanced visibility at the local, national and global levels, YITC fosters an understanding of leadership as a purposeful, collaborative, values-based process that results in positive social change. Our approach is founded on three pillars: it is transcultural, transdisciplinary and participatory. *Transcultural*, as we focus on the creative potential of different languages and cultures coming together and infuencing each other, in turn fostering social cohesion within superdiverse communities. The term transcultural emphasises the productive nature of cultural encounters and exchanges in developing new cultural formations (see Franzenburg, 2020; Welsch, 1999). *Transdisciplinary*, as we aim to bridge the gaps between research, creative practices, entrepreneurship, education and civic engagement. *Participatory*, as transcultural processes need to be led by local communities and to nurture local leadership, especially amongst young people.

In this chapter, we frst explore how digital storytelling (DST) and participatoryaction research (PAR) can be used to engage with students across all levels of education to challenge mainstream narratives of national cultural homogeneity. We then discuss the model of participatory storytelling that we developed alongside participants over the course of the workshops we ran for the *La Nostra Prato* project. We analyse in detail how participatory mapping, DST and photovoice activities, codesigning an exhibition and processes of divergent and convergent thinking were all deployed to help students to reclaim a creative and productive space for selfrepresentation and to gain confdence in their own voices. Finally, we conclude by refecting on the interactive storytelling experience and set of educational guidelines that we produced as part of the project, discussing the critical role that replicability,

accessibility and open-access all play for cultural and research activities that aim to promote the active participation of transcultural youth in research and policy development.

#### **13.2 Transcultural Leadership, Participatory Action Research and Digital Storytelling Methodologies**

Scientists almost unanimously point out that our societies operate way beyond the regenerative capacity of our planet (Friedman, 2018; Rockström et al., 2009). The world, in the coming decades, will be one of huge regional and class differences, increased polarisation and social strife (Randers, 2012). At the same time, globalisation will continue to produce both challenges and opportunities at the local, national and international levels. More than ever before, younger generations will need leaders able to operate within superdiverse societies and their ever-changing constellations of objects, spaces, people, ideas and information. Such leaders will have the diffcult task of bridging social and cultural differences, bringing people together and directing their joint efforts towards leverage points that can make our society more sustainable and equitable (Meadows, 2008). When operating in an environment that is volatile, uncertain, complex and ambiguous, leaders need an approach that differs from the traditional top-down hierarchical chains of command, in which a single person has a clear idea of how to tackle the problems at hand (Chia & Holt, 2009; Mintzberg, 2000; Simeone, 2020). Nowadays, successful and innovative organisations function through more agile and horizontally structured networks. Their leaders strive to bring together individuals and groups of people, especially those who think and behave in ways that nurture relationships of respect and trust and foster a sense of community (Simeone et al., 2020). Leaders realise that it is precisely from the standpoint of this rich assemblage of divergent perspectives that complex problems can be better understood and elaborated on.

When refecting on how transcultural leadership for social change may develop effectively within specifc local contexts, a few key considerations may help to frame the issue. The spaces and places within which we live, work, meet, and perform our identities and ideologies contribute signifcantly to our sense of social responsibility, civic engagement, social inclusion and psychological well-being or, conversely, our sense of isolation and exclusion (Casinader et al., 2020). Thus, a process that encourages transcultural leadership must facilitate a creative engagement with complex social geographies – that is, a transcultural understanding of space and place and of how we can explore, experience, understand and transform specifc localities. In facilitating such a process, we must, on the one hand, recognise the centrality of language – for instance, through multilingual and translanguaging processes that value and employ linguistic and cultural differences (Pennycook & Otsuji, 2014). On the other hand, we should also employ multisensorial approaches that facilitate a complex experience and understanding of transcultural locations, while developing forms of visual and aural communication that overcome the limitations of language (see, for instance, Schratz, 2009). This becomes particularly apparent when looking at the creative practices developed by young people of migrant background in large multiethnic urban contexts, from innovative everyday language practices to highly successful hip-hop performances (see Angelucci, 2021; Tetreault, 2015).

Our approach to the development of transcultural leadership skills is specifcally structured around participatory action research (PAR) and collaboratively designed participatory events (see Bjögvinsson et al., 2012; Chevalier & Buckles, 2019; Delgado, 2015 and Chaps. 10, 11 and 12 in this volume). We understand participatory action as an activist intervention driven by research practices that attempt to involve migrants as co-creators of creative and research outputs that generate public impact. Our methodology is thus based on two fundamental pillars. First, traditional models of interaction between communities and scholars must be challenged, in order to develop more authentic and productive modes of non-linear co-creation between community members and academics. Second, open-source, engaging and interactive access to the data should be provided through digital visualisations and storytelling, to the beneft of policymakers, administrators, community organisations and the broader society (see De Götzen et al., 2018). The importance of the involvement of young people in decision-making processes is often acknowledged when discussing human rights; however, their active participation in research and policy development remains limited (Gal, 2017). The effective promotion of social inclusion and cohesion requires the development of close collaboration and coproduction with young migrants, their classmates and other stakeholders (Matras & Robertson, 2017). PAR is thus particularly indicated to gather the perspective of young people (Shamrova & Cummings, 2017).

In order to develop a multifaceted analysis that can better capture, represent and engage with the "heterogeneity, complexity and fuidity" of superdiverse environments (Goodson & Grzymala-Kazlowska, 2017), transcultural methodologies need to be informed by participatory and digital research practices. This requires the development of models of participatory storytelling and visualisation that challenge the divide between the university and the community (Glick Schiller, 2011). It further requires a new focus on migrants' urban emplacement, understood as the relationship between the constant changes that affect an urban context, the complex transcultural and intersectional networks that develop within that context, and migrants' ability to acquire and accumulate social, cultural and fnancial capital within the constraints of that specifc locality as well as through complex transnational, translocal and global networks (Glick Schiller & Çağlar, 2013).

The use of storytelling practices that weave personal stories with digital media, including videos, images, sounds, texts, geolocalized data and other elements, is particularly effective when engaging with multiethnic youth, since it provides participants with engaging and interactive ways of expressing themselves and reclaiming their presence in the city. DST approaches are increasingly common in research that seeks to engage with marginalised and disadvantaged communities, "with the recognition that process can be as important as product" (Gifford & Wilding, 2013, p. 562). DST has, indeed, emerged as an effective research method for researchers

with an interest in democratising research practices (Ansley & Gaventa, 1997; Gaventa, 1993), challenging power relations between participants and researchers (Flicker, 2008) and recognising participants as co-constructors of knowledge, empowering them with a greater sense of agency (Alexandra, 2008; Lenette, 2017). In the feld of migration studies, DST approaches have become increasingly popular in projects that seek to work alongside migrant, refugee and multicultural youth (Chan, 2019; Collie et al., 2010; Lenette et al., 2019; Pienimäki, 2020; Rubesin, 2016; Vecchio et al., 2017). These methods can enable young adults to play a more important role in the research and creative process thanks to their focus on imagery and digital technologies (Johnson, 2009). As Hull (2003) notes, DST methodologies allow young participants to imagine alternative modes of belonging and possible futures, beyond racialised and material contexts. These projects can also increase young people's participation in civic life by giving voice to their concerns and hopes (Mirra et al., 2013; Morrell et al., 2015). DST methodologies have been successfully used to foster leadership skills, building opportunities for young adults to engage with local communities and policymakers and reclaiming space for selfexpression and empowerment (Derr et al., 2013).

#### **13.3** *La Nostra Prato***: One Place, Many Cultures**

Since the mid-1980s, research on the impact of transnational migration fows on Prato has concentrated mostly on the economic and social impact of the large infux of Chinese migrants (Baldassar et al., 2015; Bracci, 2015; Ceccagno, 2017; Dei Ottati, 2013). The public conceptualisation of Prato as a city shaped mostly by industrial and business practices also contributed to the lack of attention to the city's rich history of creative processes of transculturation and exchange (Dutto & Del Bono, 2020). Engaging with the complexity of such a diverse city thus requires the adoption of transcultural frameworks that move beyond binary and essentialised understandings of ethnicity to engage, instead, with the permeability between different linguistic and cultural groups (Ricatti et al., 2019) and the importance of informal processes of transculturation (Ricatti et al., 2021).

This is of particular importance when considering how young migrants and children of migrants, whose own sense of belonging is "not easily captured by either immigrant identity approaches or frameworks of hybridity" (Raffaetà et al., 2016, p. 435), can lead creative processes of transculturation and shape new and more complex understandings of superdiverse urban ecosystems. The city of Prato is also a key case study in this aspect if we consider that the number of students who do not hold Italian citizenship enrolled across all levels of education is almost three times that of the national average across Italy, which was 9.7% in the school year 2017/2018 (MIUR – Uffcio Statistica e Studi, 2019, p. 8). Like the main focus of research on Prato, studies on migrant youth and the children of migrants in Prato have, thus far, focused mostly on students of Chinese heritage (Baldassar & Raffaetà, 2018; Ceccagno, 2004; Paciocco, 2018), stressing how, despite the acts of racism,

xenophobia and classism displayed by Italians in Prato, forms of transculturation have still developed among the youth and new generations, leading to the emergence of hybrid and hyphenated senses of belonging (Paciocco & Baldassar, 2017). What these studies have *not* addressed is how acts of transculturation led by migrant youth may have affected peers without migrant backgrounds and the social fabric of the city itself.

*La Nostra Prato* was designed to address this gap by working with multicultural youth of both migrant and non-migrant heritage, their teachers and migrant and local community organisations. Our aim was to develop a new approach that could empower youth to reimagine, remap and reclaim urban space as their own. Our intention was thus that of challenging traditional models of interaction between scholars and communities in order to develop nonlinear, more authentic and productive modes of cooperation and co-creation between academics and community members (Glick Schiller, 2011). To achieve these objectives, we designed a DST process that consisted of three basic steps:

To select participants for the workshops, we liaised with the Intercultural Working Group of the Network of Secondary Schools of the Province of Prato (*Tavolo Intercultura della Rete degli Istituti Secondari di Secondo Grado della Provincia di Prato*), a local network of highly involved and motivated high-school teachers who, in recent years, have run several successful initiatives with the multicultural youth of Prato (Rete Scuola Integra Culture, n.d.). The 48 students – aged between 16 and 18 – who took part in the workshops were thus selected by teachers from eight public high schools. Our criteria for the selection was to be inclusive and transformative. Among the participants, 30 were female and 18 male. Nine different lingua-cultural groups were represented, with participants speaking Italian, Mandarin, Arabic, Albanian, Romanian, Urdu, Panjabi, English and Spanish. Participation in the workshops was entirely voluntary and participants were free to opt-in and out, without undue pressure from teachers, parents or adults. Aside from the new skills and experiences gained, participation in the YITC workshops also awarded students with credits for the work-integrated learning programmes in the Italian education system (*Percorsi trasversali per l'orientamento)*. This allowed us to work with participants every day for a full week and to ensure that they were rewarded for their work.

#### *13.3.1 Participatory Mapping and Digital Storytelling with Multicultural Youth*

The activities of the creative workshops revolved around the collaborative creation of digital storytelling in the form of participatory maps, digital storytelling, photovoice, interactive installations and a pop-up exhibition. This approach engages with the diverse skills that each co-creator brought to the workshops, with the aim of mapping, highlighting and appreciating diversity in the daily life and encounters of young people. Our focus on diversity was also refected in the transdisciplinary and transnational composition of the research team, which brought together researchers, artists, graphic designers and professional consultants to expose participants to different perspectives, different ways of seeing things, different ways of saying things and different ways of facilitating. The young co-creators who joined us thus had to learn how to adapt and react to this diversity and how to tune their way of expressing themselves in relation to it. During the workshops, participants were systematically exposed to cycles that alternatively fuel convergent and divergent thinking (Frich et al., 2021). Techniques for divergent thinking pushed participants to produce multiple ideas and to explore different directions. Techniques for convergent thinking invited them, instead, to come back together on the same creative trajectory. Going through multiple cycles of divergent and convergent thinking over the 5 days of the workshops made the participants realise that they can welcome different ideas and creative outputs, working with them to produce rich and satisfactory outcomes. This co-creative process emerged by combining the contributions of all the participants into a fnal pop-up exhibition and a digital storytelling experience.

A week before the start of the workshop we conducted introductory sessions with smaller groups of participants in their own high schools. Spending time with the students before the start of the intensive workshops was a crucial component of our methodology, allowing us to better understand each participant's skills, aims and hopes and to incorporate them into the fnal experience. In order to do so, we organised a participatory mapping exercise with each group, to learn more about their stories and how they experience the city at a day-to-day level. This was followed by a media training session, where students were introduced to the technical aspects of DST. Questionnaires prepared by the research team were then distributed to collect initial data on the languages spoken by each participant, on their skills and on their own aims for the workshops.

Day 1 of the workshops was dedicated to participatory mapping activities, with the objective of working with students to learn more about how they experience the city through their senses, how they relate to its multicultural landscape and what they would like to see changed. For this exercise, participants were divided into fve groups of around 10 members each. Using printed maps of Prato, we frst worked together to identify patterns of movement across the city, exploring personal relations to specifc areas of it and discussing how participants move across transcultural areas and whether or not they perceive differences between various parts of Prato. The second part of the exercise was conducted collaboratively on larger maps

of the city and focused on building sensorial maps of Prato's multilingual and multicultural landscape (see Fig. 13.1). The discussion unfolded in free form and was driven by questions such as "Where do you hear music in other languages?" or "Where do you hear/see different languages?". Finally, we focused on the connections that participants might feel with places outside their own city, their desires to add to or remove elements from it and the fascination that they might have for other countries, regions and cities. In doing so we explored dimensions of belonging, transculturality and the reclamation of space that are linked to aspects like memories, aspirations, desires and cultural infuences through various media forms.

The next 2 days were dedicated to the creative missions of the workshops and saw participants working in smaller groups – designed to ensure a good range of diversity of heritage, language and gender – to explore the city and to capture images, stories and short videos. The frst mission was dedicated to a sensorial exploration of Prato's multicultural landscape and encouraged participants to experiment with new ways of moving, feeling, reading and interpreting Prato. Different parts of the city were assigned to each group and they were asked to focus on aspects such as signs and billboards in different languages, food that they never eat, sounds that make them happy and smells which take them elsewhere or which, instead, bring them back home. The mobile app developed for the project allowed them to quickly record images, videos and sound clips in each location of their choosing. Through this sensorial exploration of the city, the students discovered unexpected

**Fig. 13.1** One of the maps produced by participants during the workshops in which they discussed and mapped the sounds of their city

places such as a Buddhist temple or an Arabic cultural centre. At times they were welcomed, other times looked upon with suspicion. They tasted new food and drinks, became excited about traditional wedding dresses and refected on the rise of a global culture within their own town. An interesting aspect that emerged from this mission is how, within each group, participants led their peers to the discovery of places that were familiar to them but not to others, fostering a process of transcultural leadership and exchange that greatly increased their confdence (see Fig. 13.2).

The second mission was dedicated to the creation of an emotional map of the city (see Fig. 13.3). We asked students to work on rage, disgust, sadness, joy, surprise and fear and to refect on which places in Prato made them feel this way, whether they felt like they belonged to each place selected and if they felt that they could transform them through their own intervention. Each group was asked to create a brief story for each emotion, based on a personal memory. Creating a storyboard, they started to visualise their emotions. They then set out to capture pictures or videos to represent the place and the emotion they associate with it. The personal memories were recorded as separate audio fles, transcribed as a text fle and geo-localised using the software we developed for the workshops. What emerged from this mission was a complex, rich and, at times contradictory, representation of Prato. Locations like the Serraglio train station and its adjoining basketball pitch elicited contrasting emotions of disgust – for its state of decay – and surprise. As one participant put it: "The playground of the Serraglio train station surprised me because kids

**Fig. 13.2** Participants explore the city through their senses during the frst mission

**Fig. 13.3** Surprise, joy and fear in three digital stories produced by participants

and adults, all different from each other, meet, play and chat together. All different, all welcome".1

By exploring the city together, students were able to share personal memories and emotions, refecting on their relationship with the city, their own role as part of the community and their ability to bring about social change. In one instance, a group of young girls chose to take a group picture in a location that elicited fear for one of them, accompanying it with the tag "The strength of women removes fear". In another, participants approached the city's most famous landmark – the Emperor's castle– but focused their attention on the long queue in front of Caritas, a local relief organisation located behind it. As one of the participants wrote:

At the back of the castle, one fnds Caritas – a relief organisation – and needy people of all ages, religions and ethnicities queue up for a hot meal and clothes. Some people sleep on dank grass, covered only by a threadbare blanket. For all things there's two sides of the coin and it's disgusting to choose to see only one.2

All their contributions manifested a profound desire to be part of the community, to embrace its cultural and linguistic complexity, and to have an impact on the future of their city.

<sup>1</sup> In Italian: "Il playground del Serraglio mi suscita sorpresa. Perché grandi e piccini, tutti diversi tra loro, si incontrano, giocano e parlano. Tutti diversi, tutti benvenuti". All translations into English are ours.

<sup>2</sup>Sul retro è presente la Caritas e si vedono persone di tutte le età, religioni ed. etnie, in fla per un pasto caldo e un vestito. Persone che si mettono a dormire sull'erba bagnata, coperti da una misera coperta logorata. Per ogni cosa ci sono due facce della medaglia ed. è disgustoso decidere di vederne una sola.

#### *13.3.2 Reclaiming Transcultural Space Through a Temporary Exhibition*

The fnal 2 days of the workshop were dedicated to the organisation of a one-night pop-up exhibition, featuring a selection of the works which the students had produced in the previous days. Public exhibitions of creative work produced during participatory-action research are a critical component in reclaiming a public space of self-expression, allowing participants to engage with policymakers, families, friends, teachers and the general public (Halsall & Forneris, 2016). The event was entirely organised and run by the workshop participants, who divided themselves into different groups according to their interests and skills. The communication team worked with one member of the research group to set up the social media communication strategy, write and disseminate the offcial media release and reach out to local media and radio stations to advertise the exhibition. The press release which they produced highlights how they framed the organisation of the exhibition as an activist reclamation of space, staking an ownership claim on the transcultural urban environment they live in and on its futures:

The reasons why we decided to join the project are numerous. With this work, we wanted to take back Prato, not just in a physical sense but also in a moral sense, through our own perspectives and imagination. We are the youth and Prato will be ours in the future, so we have a right to express ourselves because we exist. Often no one asks for our opinions, except in instances like the "Fridays for Future" rallies. This is why we worked together and on equal ground, learning not to be strangers in our own city.3

The design team led the visual creation of postcards, fyers, promotional materials and multilingual information plaques in Italian, English and Mandarin for the exhibition (see Fig. 13.4). Teams of curators were then put in charge of selecting the creative outputs for the exhibition. One was tasked with selecting images and stories and decided to showcase them in sections by topics, creating titles and descriptions for each. It was in this instance that participants decided to add self-portraits into the exhibition space, including them in a section which they named "Us". Another was in charge of transforming the videos and audio recordings into a multi-screen video installation, for which they selected materials, edited them alongside one member of the research team and took care of the technical installation. The mapping team decided to exhibit the participatory maps produced during the workshops, accompanying them with data visualisations that could guide visitors through each of the questions explored. Another team focused on producing interactive installations where the public could actively engage in a process of participatory mapping using

<sup>3</sup> I motivi per cui abbiamo deciso – spiegano i ragazzi – di prendere parte a questo progetto sono molti, tra cui cercare di riprenderci la città di Prato, non fsicamente ma moralmente: attraverso il nostro sguardo e la nostra immaginazione. Noi siamo i giovani e Prato sarà nostra in futuro, quindi il diritto di esprimerci ce lo abbiamo perché esistiamo. Spesso nessuno ci chiede il nostro parere, tranne in alcuni casi come le manifestazioni di "Friday For Future". Per questo abbiamo lavorato insieme e alla pari imparando a non essere estranei nella nostra città.

**Fig. 13.4** Postcard produced by participants to represent the many languages of Prato and advertise the exhibition

a selection of the topics explored in the workshops. Visitors were invited to defne what Prato is for them by adding words to a multilingual word-cloud that was posted on a wall and to share what they wish to add to and remove from their city on two large-scale printed maps. Finally, a group of participants organised a performance in multiple languages that opened the exhibition and welcomed everyone into the space that they set up together.

The exhibition launched on 5 October 2019, with a group of young creators flling the exhibition space with voices in different languages, all speaking at the same time and over each other, as three of them took centre stage to welcome visitors to their reclaimed space. This polylingual performance dramatically attracted the audience's attention and, at the same time, served to demonstrate that individuals can and do "inhabit" more than one linguistic home. Perhaps more importantly and in line with Welsch's (1999) understanding of transculturality, this opening performance showcased how the choice of the linguistic home people wish to inhabit at any given moment supports individual decisions regarding multiple forms of belonging. In this instance, the plurality and choice of languages represent constitutive elements in the narrative practices of these youths, acting as markers of the composite and complex nature of both individual and cultural identities.

**Fig. 13.5** Students involved in the *La Nostra Prato* project launch of the pop-up exhibition at Offcina Giovani, Prato, Italy, 5 October 2019

As a creative intervention where the private reimagining of Prato performed by each participant was made public, the exhibition itself created a space where the daily transcultural exchange across the different cultures and languages that characterise Prato was made visible and tangible (see Fig. 13.5). For a few hours, 200 people, including families and friends, teachers, city councillors, the mayor and members of the general public became part of a city re-imagined by its transcultural youth. It was in this instance that we frst noticed the impact of the work conducted over the course of a week, as the workshop participants spontaneously organised guided tours of the exhibition, leading groups of people across the different sections and explaining their own work. As we observed, the attendees were quick to engage with the new space of transculturation created by the students. The evaluation board that people were invited to fll in at the end of the exhibition indicated a very high level of appreciation for all works exhibited – and the interactive creative works, in particular, were the most appreciated. "Prato is…" – the interactive installation where the public was invited to add a single word on a wall to express what the city represents for them – saw a total of over 70 interactions in nine different languages. Many people used words that connect with the transcultural space of interaction created by the workshop participants. Prato was described in the words of the public as a space of "entanglement", "contamination", "voices", "entropy" and "hospitality". Many people also chose to contrast negative connotations such as "dirt", "fear" and "bad smell" by overlaying them with words such as "future", "home", and "hope". Besides the interaction with the work exhibited, we also noticed how the exhibition space was quickly transformed into a space for transcultural socialisation thanks to the active role played by workshop participants in bringing friends, families and the general public together and in introducing people from different societal groups to each other.

The feedback gathered from students confrms that *La Nostra Prato* was, for many, a transformative experience: allowing them not only to discover new parts of their city and form friendships with peers from different cultural and linguistic backgrounds but also to reclaim a creative and productive space for selfrepresentation and to gain confdence in their own voices and transcultural leadership skills. As they put it:

I have learned that, even if you are young, you can have your voice heard if you believe in it.

This experience enriched me because I encountered many other cultures. I have learned to observe my city from other points of view and I discovered new places in areas that I cross daily.

I have learned that we take many things for granted. We often stop at the surface and do not truly engage with what surrounds us.

Thanks to this project, I worked with other young people and shared my emotions with them. I am proud of the work we did. It was worth it.

I have learned to observe more carefully the places that surround me and to pay attention to details that I often miss in my daily life. I have also learned that unity is strength.4

The organisation of the exhibition and the creative missions were the most valued components of the whole experience for most of the participants involved. The leadership skills that students developed over the course of the workshop facilitated the dissemination of project results in the weeks and months following the end of the project. A group of participants was invited to discuss the project and its outcomes on a local radio programme and three of them joined the research team for the online public launch of the project's website in March 2021.

<sup>4</sup>Ho imparato che se vuoi farti sentire anche se sei piccola, devi crederci.

Questa esperienza mi ha arricchita perché sono entrata a contatto con diverse culture, ho imparato ad osservare la mia città da diversi punti di vista e ho scoperto luoghi che non conoscevo anche se facevano parte di zone in cui passavo quotidianamente.

Ho imparato che spesso diamo per scontato certe cose,che spesso ci fermiamo all'apparenza e che in realtà non conosciamo a fondo ciò che ci circonda.

Grazie a questo progetto ho lavorato con ragazzi con i quali ho condiviso le mie emozioni e sono contento del lavoro che abbiamo creato, ne è valsa la pena.

Ho imparato a guardare più attentamente i luoghi di Prato e a fare attenzione ai dettagli ai quali nella vita di tutti i giorni non faccio caso. Inoltre ho imparato che l'unione fa la forza.

#### **13.4 Transcultural Futures: Transforming a Participatory-Action Workshop into an Interactive Storytelling Experience**

One of the cornerstones of our methodology is the combination of digital and interaction design, informed by the disciplines of the humanities, to produce striking digital outputs that are highly original and potentially impactful. To achieve broader visibility for the participants' creative work at a national and international level, we transformed the geo-localised stories, photographs, videos and testimonies produced during the workshops into an interactive digital storytelling experience that provides an original interpretation of Prato from the many perspectives of its multicultural youth. The *La Nostra Prato* online experience is available in English and in Italian and was designed to allow users to step through the multicultural history of Prato across the years, to experience the city through the senses, emotions and hopes of the 48 young creators who joined us during the workshops and to engage with the urban reality they live in, learning how they imagine a different and better future for their city (see Fig. 13.6).

*La Nostra Prato* is structured in three modules: Past, 2019 and Futures. The frst section of the experience takes users on a journey from the Middle Ages to the present, showcasing how the city of Prato has become what it is today through seven centuries of exchange of ideas, goods, entrepreneurs and workers. It combines historical, quantitative, demographic and qualitative data collected in preparation for the workshops using interactive maps that visualise the complex transnational network that connects Prato to the rest of the world, showcasing how encounters between different peoples, cultures and languages increase people's ability to create, produce, communicate and share. The second module is meant to introduce users to Prato through the senses and emotions of its multicultural youth, showcasing how their stories, perspectives and creativity can provide an even richer portrait

**Fig. 13.6** The landing page of the digital storytelling experience

of the city. A selection of the videos produced by participants is used to introduce the process and methodology that guided their urban exploration. The experience then moves to an interactive media grid that features a selection of the stories and images produced during the workshops, delving deeper into the sensorial and emotional landscapes of Prato's multicultural youth and celebrating the agency and leadership of participants in reclaiming urban space as their own (see Fig. 13.7).

The last section of *La Nostra Prato* is dedicated to how multicultural youth can have an impact on their city, working together to have their voices heard and to imagine new futures. It presents the vision for the future of Prato of participants across four postcards (for an example, see Fig. 13.8). Each one introduces different aspects of their plans for the city, outlining the different futures of 'their Prato'. Through their work, Prato was re-imagined as an international creative hub, with participants advocating – amongst other things – for a new public library near the

**Fig. 13.7** The Media Grid featuring the images and stories created by workshop participants

**Fig. 13.8** Prato's castle is reimagined as a summer club in one of the postcards designed by the students

Buddhist temple, an International House of Comics in the Macrolotto Zero district and a polyfunctional centre where they could share knowledge about nature, culture, the arts and sport. Sustainability and connectedness were also of pivotal importance for participants, with requests for a conservation area for fora and fauna accompanying demands for a high-speed tram line connecting Prato to nearby airports. Access to new countries was accompanied by requests for more exchange between the different cultures and languages that call Prato home. Participants would love to create *tajine* restaurants where they could share the food they eat at home with the rest of the city, karaoke bars in the city centre and gyms where they can learn to become cheerleaders. Interestingly enough, these requests for further processes of transculturation went hand in hand with others that advocated for a more globalised city, where international fast-food chains and shopping centres coexist with local businesses. Finally, their city was re-imagined as a space that fosters co-creative processes of exchange and growth, with numerous requests for more spaces and cultural centres where newcomers to Prato can get together and know each other, music clubs, discotheques, queer bars, a stadium for live music, theatres and a museum of cinema, as well as empty public spaces to be re-invented together. This last point is perhaps one of the most interesting ones, showcasing how the transcultural leadership skills that participants fostered over the course of the week are geared towards a future in which they see themselves working alongside others to change the space they live in.

We believe that bridging the gaps between research, creative practices, entrepreneurship, education and civic engagement requires producing results that can be used for educational purposes and a methodology that can freely and easily be adopted and adapted by different stakeholders. For this reason, we produced a short documentary that follows us during the week of workshops and two different sets of educational guidelines that accompany the interactive storytelling experience. The frst is a teacher's guide that presents guidelines on how to use the digital storytelling experience through a series of in-class activities tailored for students from the age of 14 onwards (Dutto et al., 2020a). In order to facilitate the replication of the workshops across schools, other educational contexts and other cities, we have also developed a set of guidelines that reconstruct the 5 days of workshops, refecting on what we learned as a research team and on the co-creative exploration of Prato that we experienced together with the participants (Dutto et al., 2020b).

#### **13.5 Conclusions**

We invited three of the participants from the *La Nostra Prato* project to the website launch event in March 2021 to discuss their passion for social change and share how participating in the project was, for them, a transformative experience. Maria, who is of Albanian heritage, noted how she felt an increased sense of self-confdence, fostered by the processes of transcultural exchange with other participants and by a recognition of her own sense of agency in reclaiming what she identifes as 'new spaces of respect', where difference and diversity can be experienced together. Bilal, whose family is originally from Pakistan, stressed how experiencing the city through the eyes and emotions of fellow young people from other cultural and linguistic backgrounds has allowed him to notice new details and recognise the richness and complexity of his hometown. The biggest satisfaction for Elisa, who is of Egyptian heritage, was getting out of her comfort zone, challenging herself, interacting freely with the research team and with her peers and working together to reclaim a space of her own through the exhibition. Beyond their individual experiences, they all noted that there were many lessons to be learnt from this kind of participatory action project that would beneft other young people seeking to make a positive impact in their communities. Not least that the process of creating their own multilayered narratives enhanced their respect for and valuing of diversity.

Active participation, dialogue and openness to change were all critical components of our approach. The methodology discussed in this chapter was fne-tuned and adjusted as the intensive workshop progressed, thanks to the contributions of the 48 co-creators who joined us. An adaptability to different settings and an interest in developing localised creative interventions based on each co-creator's skill set and interests are critical components of the strategy that we are aiming to pursue with *Youth in the City* in the future. Our objective is to continue testing, adapting and fne-tuning the model of participatory creative interventions for social change by developing new projects in superdiverse cities across the world. Some key questions may only be answered once a few more projects have been developed, including the extent to which this kind of project can effectively infuence dominant narratives around migration and social cohesion and how the different local and national contexts in which the projects take place might infuence actual outcomes. Nevertheless, this particular experience has shown that there is value in the process itself and that the impact of such a project may be diffcult to quantify without considering it as just one iteration of the broader research initiative – and, perhaps more importantly, as just one expression of a constellation of cultural and educational projects which, over time and across different geographical and social spaces, may encourage young people to become leaders for social change. They will be the real and impactful agents of any meaningful social and cultural transformation.

**Acknowledgments** The authors wish to note the fundamental role that Salvatore Iaconesi and Oriana Persico, who were part of the research team, played in every aspect of the project, with their creativity, integrity, and extraordinary ability to work with and guide the young participants. We also thank the design team Pieter Overgoor, Sven Ebens and Yu-Chun Li for their important contribution to the project. Our warmest thanks also go to the 48 young creators who joined us in this project (Alesjo Arapi, Greta Barontini, Hafsa Boutriq, Sara Bocci, Miriam Boccia, Mattia Borselo, Pietro Brunori, Martina Carbone, Arianna Carleo, Filippo Carlesi, Darla Dervishi, Amine Ejjammaa, Elisa El Tayyeb, Aisosa Erimiatoe, Alessandra Errichiello, Matteo Francioso, Jennifer Frau, Elisabetta Gaito, Michela Giuliana Giurgica, Filippo Giusti, Elena Grassi, Melissa Gurra, Anna Kastano, Bilal Khan Burki, Leila Lach Hab, Luigi Liu, Bohua Liu, Gerard Manrique, Claudia Muka, Gabriele Para, Alessia Paradiso, Ilaria Pezzica, Maria Angela Popa, Riccardo Puccetti, Sofa Rinaldini, Matilde Ruperto, Edona Sabani, Lorenzo Saraceno, Gerard Selboja, Joana Sinani, Vita Singh Kang, Noemi Spadaro, Alex Tognocchi, Valentina Vene, Mayra Alessia Viola, Chiara Weng, Edoardo Zekatrinaj and Simone Zhou).

*Youth in the City: La Nostra Prato* was funded by the National Geographic Society (NGS-56467E-19), the Scanlon Foundation and Prato's City Council.

#### **References**

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.


**3.1 Process basics and physics**

Fusion splicing involves localized melting of two fibre butts pressed together, with fibre coating removed. Surface tension forces cause glass to flow when viscosity is low enough, forming a joint with continuous structure and smooth, round external surface (Figure 1).

While smoothing of edges improves splice strength, self-centring of fibres shown in Figure 2 is undesirable when lateral shift is needed to align non-concentric fibre cores.

This chapter focuses on procedures and experiences with fusion splicing using equipment and tools intended for standard single mode and multimode telecom fibres, which gave acceptable results for most, but not all PCFs the authors encountered. Before this matter is presented in section 4, overview of "holey" fibres and their properties is made in section 2,

Their common feature is substantial modification of optical characteristics by presence of multitude of longitudinal holes or concentric layer(s) of solid micro- or nano-particles

b. PCFs with doped core surrounded by layers of holes, like HAF and nonlinear fibres.

d. Fibres with single central hole surrounded by dielectric mirror (hollow fibers and

Bending-tolerant Hole-Assisted Fibres (HAF) and fibres with solid nanostructured barrier found use in optical access networks (FTTH) and are covered by ITU-T G.657 recommendation, specifying their properties - but not designs. Corning ClearCurve fibre with layer of embedded solid particles around core is fusion spliced as SMF, while HAF is converted to SMF by collapse of holes on fusion splicer (Nakajima et al., 2003); both are not covered here. Properties differ: while fibres (b) and (c) are "splicing friendly", work with suspended-core PCFs and other fibres from group (a) is more difficult. Large-core "dielectric mirror" fibres for delivery of high-power laser radiation (d) are used in short lengths and not spliced. Experience of authors applies to first two groups, but recommendations are applicable to most other microstructured fibres. Key properties for

This section will introduce reader to arc fusion splicing of conventional, solid fibres and

Fusion splicing involves localized melting of two fibre butts pressed together, with fibre coating removed. Surface tension forces cause glass to flow when viscosity is low enough, forming a joint with continuous structure and smooth, round external surface

While smoothing of edges improves splice strength, self-centring of fibres shown in Figure 2

is undesirable when lateral shift is needed to align non-concentric fibre cores.

a. PCFs without doped core, e.g. suspended-core and highly birefringent fibres.

and arc fusion physics and technology are summarized in section 3.

around the light guiding core. There are several variants, including:

c. Fibres with solid nanostructured barrier around doped core.

The core is capable of guiding light on its own.

**3. Physics and technology of arc fusion splicing**

techniques adopted for splicing fibres in communication networks.

**3.1 Process basics and physics**

(Figure 1).

**2. Microstructured optical fibres**

Photonic Bandgap Fibres).

fusion splicing include:

Fig. 1. Two identical 125 μm silica fibres before (top) and after (bottom) arc fusion. Electrode tip is visible as a black spot at the bottom of upper image.

Fig. 2. Two 125 μm single-mode fibres spliced with 10 μm perpendicular offset. Top to bottom: fibres before fusion and after 0.5 s, 1 s and 2 s long fusion with 17 mA current.

Glass evaporating from the hot zone is partly deposited on fibres in the vicinity - degrading surface quality and strength, and on parts of splicing machine - contaminating them. Evaporation is compensated for by fibre overlap: a reduced volume of glass is accommodated in shorter length of fibre without change in diameter. As no air, gel, glue etc. separates fibres after fusion, strength close to one of pristine fibre, no reflection and low insertion loss are possible. The heat for fusion is provided by either:

Arc Fusion Splicing of Photonic Crystal Fibres 179

Material CTE (10-6/K-1) Heat conductivity (W/m•K)

Table 1. Comparison of thermal properties of fused silica and selected other materials.

which the glass is transparent, and conduction along the fibre (Yablon, 2005), and:

required.

**3.3 Fusion procedure**

Heat transfer during fusion is mostly through bulk radiation at wavelengths of 0.6-2 μm, to

Doping with germania (GeO2) or titania (TiO2) considerably reduces silica viscosity, and fusing multimode fibres with 50-62.5 μm core taking 20-25% of cross-section requires lower temperature than single-mode fibres, where core is small (4-10 μm) and contains less GeO2. In a hot fibre, diffusion of dopant(s) is observed, changing refractive profile and core size. The problem is acute during splicing of "depressed cladding" or "pure silica core" singlemode fibres, where core is surrounded by a layer doped with fluorine (F), a light element easily diffusing at high temperatures; careful control of arc power and short fusion time are

Out-gassing of boron, phosphorus, germanium or fluorine compounds from melted glass may cause problems as well, in particular during splicing of highly-doped specialty fibres. Silica does not burn, decompose or oxidise when heated in the air. However, exposure to humidity, alkalis or sharp objects produces surface flaws; damaged fibre breaks easily. All lengths of fibre stripped of coating must be promptly protected against humidity, abrasion, etc. Only splices intended for short-term use in laboratory conditions may be exempted.

Fusion of fibres with different dopants or doping levels can produce significant internal stress due to uneven thermal contraction after fusion, potentially affecting splice strength.

Arc fusion splicing of two single, polymer-coated, multimode or single-mode silica fibres of

3. fibre cleaving by scoring with a blade and applying controlled strain till it breaks

125 μm cladding diameter usually includes steps listed below:

("scribe and load"); cleave angle shall be less than 1,

4. clamping of fibres in supports with V-grooves,

1. removal of coating from fibres, usually by mechanical stripping,

2. fibre cleaning with solvent: isopropyl alcohol, acetone, etc. or dry wiping,

Fused silica 0.55 1.38 Tungsten 4.3 173 Steel 13-18 12-45 Copper 16.6 401 Aluminium 22.2 237 PVC (hard) 50-80 0.13-0.29 PET 60-70 0.17-0.24 PMMA 50-90 0.17-0.25

The first method is preferred due to compact equipment, fast operation and flexible control. Filament splicing is used for specialty fibres and when high splice strength is required. Other techniques are rarely used. Descriptions below cover arc fusion splicing only.

### **3.2 Fused silica properties and fusion splicing**

Fused silica is a glassy form of silicon dioxide (SiO2). In comparison to most multicomponent glasses, fused silica exhibits relatively slow decrease of viscosity with temperature (Figure 3). For fusion splicing, this property is desirable, as larger variations in temperature can be tolerated.

Fig. 3. Viscosity of pure fused silica as function of temperature. Approximate data compiled from sources not in full agreement (Shand, 1968, Yablon, 2005, Schott, 2007).

To ensure fusion in 0.5-2 s, glass viscosity must be reduced to about 104 Pa-s. Temperatures during different stages of fusion splicing range approximately from 1500°C (softening of fibres) to 2100°C (fusion), and electric power required to fuse two 125 μm solid silica fibres is about 8-10 W. As voltage drop between electrodes is almost constant, 500-600 V for 1 mm gap, discharge power is essentially proportional to arc current. The range for work with 125 μm fibres is approximately 7-20 mA.

Glass melting during fusion of 125 μm fibres takes place in zone 0.5-1 mm long, including effects of distribution of energy inside arc column, which is approx. 0.2 mm wide for 1 mm electrode gap. Because fused silica has exceptionally low linear thermal expansion coefficient and heat conductivity, as shown in Table 1, fibre strain during post-fusion cooling from the annealing temperature of approx. 1100C to room temperature is negligible: only 0.0099% for a 1 mm hot zone and 6 mm fibre length between clamps.

The first method is preferred due to compact equipment, fast operation and flexible control. Filament splicing is used for specialty fibres and when high splice strength is required.

Fused silica is a glassy form of silicon dioxide (SiO2). In comparison to most multicomponent glasses, fused silica exhibits relatively slow decrease of viscosity with temperature (Figure 3). For fusion splicing, this property is desirable, as larger variations in

Fig. 3. Viscosity of pure fused silica as function of temperature. Approximate data compiled

To ensure fusion in 0.5-2 s, glass viscosity must be reduced to about 104 Pa-s. Temperatures during different stages of fusion splicing range approximately from 1500°C (softening of fibres) to 2100°C (fusion), and electric power required to fuse two 125 μm solid silica fibres is about 8-10 W. As voltage drop between electrodes is almost constant, 500-600 V for 1 mm gap, discharge power is essentially proportional to arc current. The range for work with

Glass melting during fusion of 125 μm fibres takes place in zone 0.5-1 mm long, including effects of distribution of energy inside arc column, which is approx. 0.2 mm wide for 1 mm electrode gap. Because fused silica has exceptionally low linear thermal expansion coefficient and heat conductivity, as shown in Table 1, fibre strain during post-fusion cooling from the annealing temperature of approx. 1100C to room temperature is

negligible: only 0.0099% for a 1 mm hot zone and 6 mm fibre length between clamps.

from sources not in full agreement (Shand, 1968, Yablon, 2005, Schott, 2007).

125 μm fibres is approximately 7-20 mA.

Other techniques are rarely used. Descriptions below cover arc fusion splicing only.

**3.2 Fused silica properties and fusion splicing**

temperature can be tolerated.

Table 1. Comparison of thermal properties of fused silica and selected other materials.

Heat transfer during fusion is mostly through bulk radiation at wavelengths of 0.6-2 μm, to which the glass is transparent, and conduction along the fibre (Yablon, 2005), and:

Doping with germania (GeO2) or titania (TiO2) considerably reduces silica viscosity, and fusing multimode fibres with 50-62.5 μm core taking 20-25% of cross-section requires lower temperature than single-mode fibres, where core is small (4-10 μm) and contains less GeO2.

In a hot fibre, diffusion of dopant(s) is observed, changing refractive profile and core size. The problem is acute during splicing of "depressed cladding" or "pure silica core" singlemode fibres, where core is surrounded by a layer doped with fluorine (F), a light element easily diffusing at high temperatures; careful control of arc power and short fusion time are required.

Out-gassing of boron, phosphorus, germanium or fluorine compounds from melted glass may cause problems as well, in particular during splicing of highly-doped specialty fibres.

Silica does not burn, decompose or oxidise when heated in the air. However, exposure to humidity, alkalis or sharp objects produces surface flaws; damaged fibre breaks easily. All lengths of fibre stripped of coating must be promptly protected against humidity, abrasion, etc. Only splices intended for short-term use in laboratory conditions may be exempted.

Fusion of fibres with different dopants or doping levels can produce significant internal stress due to uneven thermal contraction after fusion, potentially affecting splice strength.

## **3.3 Fusion procedure**

Arc fusion splicing of two single, polymer-coated, multimode or single-mode silica fibres of 125 μm cladding diameter usually includes steps listed below:

Arc Fusion Splicing of Photonic Crystal Fibres 181

Fibre core guiding radiation is small, with effective diameter usually in the 2-15 μm range in single-mode fibres, with extreme values often encountered in PCFs, and accurate alignment of fibre cores during splicing is essential. Main factors introducing splice loss include:

For splice between single mode fibres, insertion loss Γ resulting from core offset, MFD difference and angular misalignment is given by the following formula (Yablon, 2005),

2 2 2 2 2 1 2 1 2

*g g g g*

*w w w w*

where wg1 and wg2 are Gaussian radii of spliced fibres, δ is lateral offset between fibre cores, θ is the angular misalignment, n is refractive index of fibre material and the operating wavelength. Characteristics of loss due to each factor are shown in Figures 5, 6 and 7. Loss

The mode field diameter (MFD) of fibre included in technical specifications, usually measured in accordance with Petermann II definition is roughly twice its Gaussian mode

For fibres with smaller MFD, splice loss rises faster with lateral offset, but slower with angular misalignment; the resultant loss is approximately proportional to square of given misalignment. While lateral offset between fibre claddings is easy to detect visually through splicer microscope, even large angular misalignment, most often due to debris in V-grooves holding fibres may be overlooked when field of view is small or the optical system produces image distortion. This is critical in splicing large-MFD fibres for high power applications. Accuracy of fibre alignment depends on core size and accepted loss. For splicing singlemode fibres (wg = 2.5-5 μm) with loss below 0.2 dB, lateral core offset must be reduced to 0.5-1 μm (Figure 6). If the alignment requires cladding offset, increase of it is needed to compensate for self-centring of fibres during fusion. Splice loss can be estimated from MFD mismatch, core misalignments and deformations measured by automated analysis of splice image. True value is obtained from bi-directional measurements with optical time domain reflectometer (OTDR), as differences between backscattering intensity in fibres can produce

2 2 2 2 22 2 2 1 2 1 2

4 4 2/ sin

*g g g g*

*w w nw w*

(1)

mode fibres and physical core diameter in multimode fibres,

values calculated this way are only approximate because:

radius, but definitions of both parameters are not directly comparable.

aligned with lateral offset (Figure 2),

10log exp 2

assuming a Gaussian approximation of mode fields:

**3.4 Fibre alignment and splice loss**

Figure 4 shows typical sequence of arc current and fibre movement.

Fig. 4. Example of fibre-fibre gap and arc current variations during fusion splicing of SMF. Negative value of gap means an overlap of fibres pressed into each other.

Arc current and duration of heating in steps 9-11 and fibre overlap in step 9 depend on fibres spliced. 10% deviation from optimum arc current is usually enough to significantly rise splice loss or reduce splice strength, if current and temperature are too low. To reduce self-centring, fusion time is shorter for single mode than multimode fibres: 0.5-1 s vs. 1-2 s.

Some coatings require thermal stripping, softening with chemicals or burning for removal. When high splice strength is required, acrylate, epoxy-acrylate or polyimide coatings can be dissolved during 20-30 s immersion in hot (180-200C) sulphuric acid (H2SO4) - either pure (95%) or with addition of approx. 5% nitric acid (HNO3). Residual acid is removed by rinsing the fibre with water and later acetone (Matthewson et al., 1997).

### **3.4 Fibre alignment and splice loss**

180 Photonic Crystals – Introduction, Applications and Theory

8. alignment of fibres for lowest transmission loss; this may involve application of perpendicular offset with monitoring of loss or observation of cladding or cores, 9. softening of fibres by low power discharge: 6-9 mA current, 0.5-3 s duration, than

Fig. 4. Example of fibre-fibre gap and arc current variations during fusion splicing of SMF.

0 2 4 6 8 10

**Time [s]**

Arc current and duration of heating in steps 9-11 and fibre overlap in step 9 depend on fibres spliced. 10% deviation from optimum arc current is usually enough to significantly rise splice loss or reduce splice strength, if current and temperature are too low. To reduce self-centring, fusion time is shorter for single mode than multimode

Some coatings require thermal stripping, softening with chemicals or burning for removal. When high splice strength is required, acrylate, epoxy-acrylate or polyimide coatings can be dissolved during 20-30 s immersion in hot (180-200C) sulphuric acid (H2SO4) - either pure (95%) or with addition of approx. 5% nitric acid (HNO3). Residual acid is removed by

Negative value of gap means an overlap of fibres pressed into each other.

rinsing the fibre with water and later acetone (Matthewson et al., 1997).

5. cleaning of fibres by short (0.2-0.5 s), low power electric arc, 6. visual inspection of fibre tips for proper cleave and cleanliness,

15. splice protection by heat-shrinkable sleeve, re-coating, etc.

Figure 4 shows typical sequence of arc current and fibre movement.

pressing together with 6-15 μm overlap,

13. insertion loss measurement (optional),

14. tensile strength test (optional),

fibres: 0.5-1 s vs. 1-2 s.

0

10

**Arc Current [mA]**

20

7. placing fibre tips between electrodes with 10-20 μm gap (butt coupling),

10. fusion of fibres by high power electric arc: 12-20 mA current, 0.5-2 s duration,

Prefusion

Cleaning Annealing

Fusion

**Gap [μm]**

0

10

20

11. annealing / polishing of fibres with low power electric arc (optional), 12. visual inspection of splice: no distortions, slits or bubbles allowed,

Fibre core guiding radiation is small, with effective diameter usually in the 2-15 μm range in single-mode fibres, with extreme values often encountered in PCFs, and accurate alignment of fibre cores during splicing is essential. Main factors introducing splice loss include:

For splice between single mode fibres, insertion loss Γ resulting from core offset, MFD difference and angular misalignment is given by the following formula (Yablon, 2005), assuming a Gaussian approximation of mode fields:

$$\Gamma = -10\log\left[\frac{4w\_{\text{g1}}^2 w\_{\text{g2}}^2}{\left(w\_{\text{g1}}^2 + w\_{\text{g2}}^2\right)^2} \exp\left(-\frac{4\delta^2 + \left(2\pi/\lambda\right)^2 n^2 w\_{\text{g1}}^2 w\_{\text{g2}}^2 \sin^2\theta}{2\left(w\_{\text{g1}}^2 + w\_{\text{g2}}^2\right)}\right)\right] \tag{1}$$

where wg1 and wg2 are Gaussian radii of spliced fibres, δ is lateral offset between fibre cores, θ is the angular misalignment, n is refractive index of fibre material and the operating wavelength. Characteristics of loss due to each factor are shown in Figures 5, 6 and 7. Loss values calculated this way are only approximate because:

The mode field diameter (MFD) of fibre included in technical specifications, usually measured in accordance with Petermann II definition is roughly twice its Gaussian mode radius, but definitions of both parameters are not directly comparable.

For fibres with smaller MFD, splice loss rises faster with lateral offset, but slower with angular misalignment; the resultant loss is approximately proportional to square of given misalignment. While lateral offset between fibre claddings is easy to detect visually through splicer microscope, even large angular misalignment, most often due to debris in V-grooves holding fibres may be overlooked when field of view is small or the optical system produces image distortion. This is critical in splicing large-MFD fibres for high power applications.

Accuracy of fibre alignment depends on core size and accepted loss. For splicing singlemode fibres (wg = 2.5-5 μm) with loss below 0.2 dB, lateral core offset must be reduced to 0.5-1 μm (Figure 6). If the alignment requires cladding offset, increase of it is needed to compensate for self-centring of fibres during fusion. Splice loss can be estimated from MFD mismatch, core misalignments and deformations measured by automated analysis of splice image. True value is obtained from bi-directional measurements with optical time domain reflectometer (OTDR), as differences between backscattering intensity in fibres can produce

Arc Fusion Splicing of Photonic Crystal Fibres 183

As all single-mode and multimode telecom fibres exhibit radial symmetry of core and

Properly made splice of identical fibres has insertion loss of around 0.05 dB and return loss in excess of 70 dB. Butt-coupling with 10-15 μm gap, e.g. before fusion (Fig. 1) introduces insertion loss of approx. 0.40 dB and 15 dB return loss due to Fresnel reflection from a pair of glass/air interfaces. If a transmission loss is monitored during splicing, this difference helps to estimate splice quality. Because loss measured with laser source varies periodically with gap width due to interferometric effects (Yablon, 2005), incoherent source like LED is best. Hot fibre is a strong source of broadband thermal radiation, with emission peak close

Fig. 7. Calculated loss caused by angular misalignment of identical single mode fibres.

Loss of splice between single-mode fibres usually shows weak wavelength dependence, because MFD increases with wavelength, typically by 10-20% between 1310 and 1550 nm (Corning, 2008). If the main source of loss is core offset, it falls with wavelength, while angular misalignment produce loss rising with wavelength, in both cases in proportion to square of MFD. For multimode fibres, splice loss is essentially wavelength-independent.

Strong increase of splice loss with wavelength shown in Figure 8 indicates excessive fibre

For example, while single splice between fibres having 1:2 MFD ratio has best-case loss of 1.94 dB, two splices with 1 : 1.41 : 2 MFD ratio have combined loss 2 x 0.51 = 1.02 dB. This approach was adopted for splicing a small-core DCF with MFD of 2-4 μm to typical SMF having 8-11 μm MFD (Edvold & Gruner-Nielsen, 1996), and later to splice dissimilar PCFs (Xiao et al., 2007). Extra intermediate fibres can reduce loss further, e.g. to 0.56 dB for 4 splices and 1:2 MFD ratio, but difficulty with finding necessary fibres, losses due to other

bending due to improper handling, tight coiling or squeeze in the vicinity of splice.

factors and additional labour usually make such efforts impractical.

= 1.55 μm, n = 1.5. Blue: wg = 7.5 μm, green: wg = 5 μm, red: wg = 2.5 μm.

cladding, rotational alignment of fibres is not required.

to 780 nm at 2000C, preventing loss measurements during discharge.

relative shift of fibre traces and error in OTDR measurement of splice loss in one direction, often exceeding 1 dB.

Fig. 5. Calculated loss caused by mismatch in mode field diameters of single mode fibres.

Fig. 6. Calculated loss caused by lateral offset between cores of identical single mode fibres.

relative shift of fibre traces and error in OTDR measurement of splice loss in one direction,

Fig. 5. Calculated loss caused by mismatch in mode field diameters of single mode fibres.

Fig. 6. Calculated loss caused by lateral offset between cores of identical single mode fibres.

often exceeding 1 dB.

As all single-mode and multimode telecom fibres exhibit radial symmetry of core and cladding, rotational alignment of fibres is not required.

Properly made splice of identical fibres has insertion loss of around 0.05 dB and return loss in excess of 70 dB. Butt-coupling with 10-15 μm gap, e.g. before fusion (Fig. 1) introduces insertion loss of approx. 0.40 dB and 15 dB return loss due to Fresnel reflection from a pair of glass/air interfaces. If a transmission loss is monitored during splicing, this difference helps to estimate splice quality. Because loss measured with laser source varies periodically with gap width due to interferometric effects (Yablon, 2005), incoherent source like LED is best. Hot fibre is a strong source of broadband thermal radiation, with emission peak close to 780 nm at 2000C, preventing loss measurements during discharge.

Fig. 7. Calculated loss caused by angular misalignment of identical single mode fibres. = 1.55 μm, n = 1.5. Blue: wg = 7.5 μm, green: wg = 5 μm, red: wg = 2.5 μm.

Loss of splice between single-mode fibres usually shows weak wavelength dependence, because MFD increases with wavelength, typically by 10-20% between 1310 and 1550 nm (Corning, 2008). If the main source of loss is core offset, it falls with wavelength, while angular misalignment produce loss rising with wavelength, in both cases in proportion to square of MFD. For multimode fibres, splice loss is essentially wavelength-independent.

Strong increase of splice loss with wavelength shown in Figure 8 indicates excessive fibre bending due to improper handling, tight coiling or squeeze in the vicinity of splice.

For example, while single splice between fibres having 1:2 MFD ratio has best-case loss of 1.94 dB, two splices with 1 : 1.41 : 2 MFD ratio have combined loss 2 x 0.51 = 1.02 dB. This approach was adopted for splicing a small-core DCF with MFD of 2-4 μm to typical SMF having 8-11 μm MFD (Edvold & Gruner-Nielsen, 1996), and later to splice dissimilar PCFs (Xiao et al., 2007). Extra intermediate fibres can reduce loss further, e.g. to 0.56 dB for 4 splices and 1:2 MFD ratio, but difficulty with finding necessary fibres, losses due to other factors and additional labour usually make such efforts impractical.

Arc Fusion Splicing of Photonic Crystal Fibres 185

Fig. 10. Deformation of fibre tips by heat of electric arc: DTU MIK125/0.5 made of PMMA (left) and Corning SMF-28 made of fused silica (right). Top: cleaved fibres, middle: after 1st

Handling and splicing of thin mPOF with standard equipment is difficult due to softness of polymers in comparison to fused silica. In experiments at NIT, mPOF of 125 μm diameter exhibited unacceptable sag and curl when clamped 4 mm away from tip, while standard

This section presents some issues specific to fusion splicing of silica "holey" fibres, primarily of single mode PCF to SMF. Due to large variety of designs, actual procedure, power, time

Finished splice must be protected to have adequate mechanical strength, as holes and flaws on their surfaces make PCFs inherently weaker than solid fibres. In all experiments at NIT, fusion splices were protected with commercial 60 mm heat shrinkable sleeves reinforced with stainless steel rod. Protected splices performed well during temperature cycling between -40°C and +80C, with loss stability better than 0.05 dB, and as grips for

Fusion splices are hermetic, keeping external contaminants out, but trapping whatever entered earlier. Exceptions include helium and hydrogen, diffusing through 60 μm thick fused silica cladding in few hours. Short suspended core PCF infiltrated with acetylene (C2H2) or hydrogen cyanide (HCN) and fusion spliced to SMF pigtails is used as optical frequency reference, e.g. for calibration of optical spectrum analyzers (Thapa et al., 2006).

Out-gassing of cleaved PCF is fast, but removal of liquid or dust is essentially impossible due

Infiltration of holes with gas or liquid allows to make fibre sensors for chemical analysis, detection of pollutants or poison gas, medical diagnostics, etc. through spectral absorption

to high pneumatic resistance of thin holes and adsorption to the surface of their walls.

heating, bottom: after 2nd heating.

**4. Fusion splicing of PCFs**

V-groove clamps usually damaged the fibre.

and geometry settings must be individually tailored.

application of twist and tensile forces in mechanical tests (Figure 11).

Fig. 8. Sharp bend of SMF observed with OTDR at 1310 nm (left) and 1550 nm (right).

If fibres having substantially different MFD must be spliced, loss can be reduced by introduction of short fibre with intermediate MFD, as shown in Figure 9.

Fig. 9. Principle of splicing through intermediate fibre.