**5. Conclusion**

This chapter aims to show that there is no scientific reason for the use of the called monovision surgical technique, as well as to show that there are at least two scientific surgical alternatives. Two ways of ocular dominance are described, natural and pathological. Natural ocular dominance occurs according to the ocular system neurophysiological anatomy. Pathological ocular dominance is described in two forms, acquired and dichotomous. Acquired ocular dominance is known as ocular dominance and dichotomous ocular dominance, as referred to in this chapter, is characterized by surgical imposition. The three ocular dominances are described by their main functional characteristics and their consequences.

1.**Etiology of natural ocular dominance** - This ocular dominance is alternated between the eyes, so the dominate eye is the contralateral to the direction of the eye movement in relation to the head, its fixation, to reach an objective or to remain focused on a known objective, right after that, the dominant eye will be its contralateral one. This alternation of domination stimulates mainly the

**83**

**Figure 6.**

*Specular microscopy before and after surgery.*

*Visual Impairment Caused by Monovision Surgical Design*

physiological process characteristic of the action of the two superior oblique muscles. The superior oblique muscle action changes the corneal cylindrical dioptric power and sustains the sclera in opposition to the consequent variation in intraocular pressure. Then, the cornea shape change is part of the mass movement forced convection mechanism in the cornea and retina, in addition to moving the trabecular meshwork, to avoid obstructing the passage of aqueous humor. Forced convection in the cornea and retina prevents the accumulation of metabolic residue that causes refractive error in the cornea and stiffens the retina. The ocular domain alternation is a fast process and makes small changes in the natural lens dioptric power that is part of its own forced convection mechanism to prevents the metabolic residues accumulation that cause

2.**Etiopathogenesis of ocular dominance** - This ocular dominance is the result of habits that are harmful to the intraocular forced convection mechanism. Then, the refractive error caused by the dehydrated metabolic residues accumulated in the cornea, retina and lens resist the natural movement of the eyes and create vicious pathological movements, such as the saccadic movement

refractive error and consequent opacity.

*DOI: http://dx.doi.org/10.5772/intechopen.95770*

*Visual Impairment Caused by Monovision Surgical Design DOI: http://dx.doi.org/10.5772/intechopen.95770*

#### **Figure 6.**

*Current Cataract Surgical Techniques*

**82**

**Figure 5.**

*Biometry before and after surgery.*

before and after operative conditions.

**5. Conclusion**

than before the surgery and also in relation to the contralateral eye. The anterior surface of the cornea became more regular, As already explained in several studies [12, 14–16], the intraocular metabolic residue is dehydrated and stored, making a volume with high viscosity. To eliminate this viscous volume, it is necessary, first, to rehydrate it in order to reduce the viscosity and homogenize its concentration in the mobile mass, however, the only intraocular natural rehydration process available is the agitation performed through corneal flexion [14] using images fusion. In the 69-year-old patient case, the surgery made impossible for her to fuse the images, so there is no way to eliminate the metabolic residues from the cornea significantly. **Figure 5** shows the ocular biometry before and after surgery and **Figure 6** shows the specular microscopy before and after surgery, to better understand the patient's

This chapter aims to show that there is no scientific reason for the use of the called monovision surgical technique, as well as to show that there are at least two scientific surgical alternatives. Two ways of ocular dominance are described, natural and pathological. Natural ocular dominance occurs according to the ocular system neurophysiological anatomy. Pathological ocular dominance is described in two forms, acquired and dichotomous. Acquired ocular dominance is known as ocular dominance and dichotomous ocular dominance, as referred to in this chapter, is characterized by surgical imposition. The three ocular dominances are described by their main functional characteristics and their consequences.

1.**Etiology of natural ocular dominance** - This ocular dominance is alternated between the eyes, so the dominate eye is the contralateral to the direction of the eye movement in relation to the head, its fixation, to reach an objective or to remain focused on a known objective, right after that, the dominant eye will be its contralateral one. This alternation of domination stimulates mainly the

physiological process characteristic of the action of the two superior oblique muscles. The superior oblique muscle action changes the corneal cylindrical dioptric power and sustains the sclera in opposition to the consequent variation in intraocular pressure. Then, the cornea shape change is part of the mass movement forced convection mechanism in the cornea and retina, in addition to moving the trabecular meshwork, to avoid obstructing the passage of aqueous humor. Forced convection in the cornea and retina prevents the accumulation of metabolic residue that causes refractive error in the cornea and stiffens the retina. The ocular domain alternation is a fast process and makes small changes in the natural lens dioptric power that is part of its own forced convection mechanism to prevents the metabolic residues accumulation that cause refractive error and consequent opacity.

2.**Etiopathogenesis of ocular dominance** - This ocular dominance is the result of habits that are harmful to the intraocular forced convection mechanism. Then, the refractive error caused by the dehydrated metabolic residues accumulated in the cornea, retina and lens resist the natural movement of the eyes and create vicious pathological movements, such as the saccadic movement

[17] and the cyclotorsion movement mentioned in [18]. Dominance may not be full, as mentioned in [9], dominance depends on the evaluation criteria and usually for a specific activity.

	- **Precision**: In [8] it is written that the patient may still need a pair of glasses to read small print for a few hours or to thread the needle. In the binocular view, each cerebral hemisphere receives the image projected on the temporal retina of the ipsilateral eye and simultaneously receives the image projected on the nasal retina of the contralateral eye, that is, for the more precise region of the retina, both eyes transmit neural signals twice as much to the brain, then, binocular vision is more than twice as accurate as monocular vision, with occlusion of one eye, since, in addition to having twice as many points, they are adjusted together, by the action of the superior oblique muscles, **Figure 1c**. This description combines with human perception, two eyes see better than one eye. The lack of precision is analogous to the sportsman using the sight out of alignment. The use of bilateral monofocal lenses maintains visual accuracy before surgery however one may need glasses for some activities.
	- **Sharpness**: In [8] it is written that the patient may still need a pair of glasses for nighttime driving. Analyzing **Figure 1c**, the monovision, without occlusion of the contralateral eye, is less clear, because a cerebral hemisphere receives the focused image projected on the temporal retina of the ipsilateral eye adding, as noise, without focusing, the image projected on the nasal retina of the contralateral eye and the contralateral cerebral hemisphere, receives, in focus, the image projected on the nasal retina of the contralateral eye to this cerebral hemisphere, without the region projected on its optic disc, adding, as noise, without focusing, the image projected on the temporal retina of the ipsilateral eye, that is, the patient's brain starts to receive the image focused by one eye with the addition of the defocused image of the contralateral eye. This is a form of stimulus for night blindness. The lack of sharpness is analogous to the sportsman who uses the target in smoke.

The use of bilateral monofocal lenses can superimpose images with the same dimensions increasing the neural energy transmitted to the brain however one may need glasses for some activities.

**85**

activities.

of the wall.

adaptive power to stay alive.

must use two distinct optical powers of lenses.

*Visual Impairment Caused by Monovision Surgical Design*

• **Agility**: It is misleading to admit that the depth is given by binocular vision. If the depth depended on the simultaneous vision of the two eyes, the chicken would not be able to choose the grain of corn it eats. Animals that see their goal simultaneously with both eyes have greater agility of depth distance. The perception of distance depends on movement so astronomers are able to observe and analyze the universe with a telescope because there are movements. Those who have a natural binocular vision cannot visualize movements in static images nor can they view the stereoscopic image from photographs taken at two different points, they see two planes of images. When fixing an observation point, the alternation speed of the domain between the eyes produces dioptric powers changes in the crystallines for the rapid perception of depth but this visualization of depth is only possible up to a certain distance, from which, the brain makes use of the corneas diopter variation and for greater distances the person makes use of the head movement. After the monocular surgery there is no adjustment movement between the eyes and this may have been one of the causes of the 69 year patient's suffering. The substitution of the corneal movements for the movement of the head for depth perception the patient loses in agility because the corneas are more agile that the head, so the patient can be deprived of practicing activities that depend on agility and in transit may even cause an accident [19]. With dichotomous ocular dominance the patient may have difficulty to drive a motor vehicle, ride a bicycle and practice many sports such as tennis, ping pong, since in addition to the loss of agility, the brain receives the blurred image [20] of the contralateral eye. The lack of agility is analogous to that of sportsman with heavier equipment. An easy way to perceive the severity of the distance change problem is to use the basic principle observed by Scheinerque, in 1619, apud [1] through the using of pinhole glass [21] playing ping pong. One must be very careful when testing. The use of bilateral monofocal lenses maintains the mechanism of forced convection in the cornea, in the retina and the movement of the trabecular meshwork, fundamental for eye health, in addition to contributing to the perception of depth and has a much better result than that obtained with monovision surgery, however it may be necessary to wear glasses for some

• **Dimension**: The monocular visual field has less visual space than the visual field with both eyes. No explanation is necessary but the monocular visual field blinds part of the contralateral eye's temporal visual field. The reduction of visual space is analogous to the sportsman located on the side

To enable alternating ocular dominance if the surgery is bilateral bifocal the patient does not need corrective lenses and if the surgery is bilateral monofocal the patient must use near corrective lenses and if the surgery is monovision the patient

The vision has many secrets as nobody knows how the other sees besides nobody can compare alternatives to intraocular lenses therefore if the patient is in a very adverse situation in his vision many of the basic movements he has already lost then any improvement is profit. This was not the 69 years old patient's situation before surgery. Monovision surgery only serves to prove the human being's

The use of bilateral monofocal lenses maintains the same dimensions of the visual field before surgery, however, one may need glasses for some activities.

*DOI: http://dx.doi.org/10.5772/intechopen.95770*

*Visual Impairment Caused by Monovision Surgical Design DOI: http://dx.doi.org/10.5772/intechopen.95770*

*Current Cataract Surgical Techniques*

usually for a specific activity.

[17] and the cyclotorsion movement mentioned in [18]. Dominance may not be full, as mentioned in [9], dominance depends on the evaluation criteria and

3.**Etiopathogenesis of dichotomous ocular dominance** - This ocular dominance is the surgical result of imposing a lens set to far distances is implanted in your dominant eye, while a lens set to near distances is implanted in your non-dominant eye [8]. Thus, the patient is obliged to use corrective lenses in order to take advantage of his precarious intraocular force convection mechanism, before operative, however, upon waking up or when opening the eye during sleep, it causes an important impact, as it is not common to sleep with glasses, that is, the patient's brain spent 69 years adopting the direction of eye movement in relation to the head as a criterion for alternating ocular dominance and, due to the imposition of monovision surgery, in a "magic step", the focusing distance became the criterion for alternating ocular dominance without causing any disturbance for the patient. It is an alternative that should only be adopted with the permission given by the patient, after all, it is the patient who will be responsible for the administration of the after operative problems. In the case of the patient in focus, ocular dominance was imposed by the professional without the patient's knowledge, causing visual

losses in precision, sharpness, agility, expansion, among others.

• **Precision**: In [8] it is written that the patient may still need a pair of glasses to read small print for a few hours or to thread the needle. In the binocular view, each cerebral hemisphere receives the image projected on the temporal retina of the ipsilateral eye and simultaneously receives the image projected on the nasal retina of the contralateral eye, that is, for the more precise region of the retina, both eyes transmit neural signals twice as much to the brain, then, binocular vision is more than twice as accurate as monocular vision, with occlusion of one eye, since, in addition to having twice as many points, they are adjusted together, by the action of the superior oblique muscles, **Figure 1c**. This description combines with human perception, two eyes see better than one eye. The lack of precision

is analogous to the sportsman using the sight out of alignment.

surgery however one may need glasses for some activities.

The use of bilateral monofocal lenses maintains visual accuracy before

The use of bilateral monofocal lenses can superimpose images with the same dimensions increasing the neural energy transmitted to the brain

however one may need glasses for some activities.

• **Sharpness**: In [8] it is written that the patient may still need a pair of glasses for nighttime driving. Analyzing **Figure 1c**, the monovision, without occlusion of the contralateral eye, is less clear, because a cerebral hemisphere receives the focused image projected on the temporal retina of the ipsilateral eye adding, as noise, without focusing, the image projected on the nasal retina of the contralateral eye and the contralateral cerebral hemisphere, receives, in focus, the image projected on the nasal retina of the contralateral eye to this cerebral hemisphere, without the region projected on its optic disc, adding, as noise, without focusing, the image projected on the temporal retina of the ipsilateral eye, that is, the patient's brain starts to receive the image focused by one eye with the addition of the defocused image of the contralateral eye. This is a form of stimulus for night blindness. The lack of sharpness is analogous to the sportsman who

**84**

uses the target in smoke.

The use of bilateral monofocal lenses maintains the same dimensions of the visual field before surgery, however, one may need glasses for some activities.

To enable alternating ocular dominance if the surgery is bilateral bifocal the patient does not need corrective lenses and if the surgery is bilateral monofocal the patient must use near corrective lenses and if the surgery is monovision the patient must use two distinct optical powers of lenses.

The vision has many secrets as nobody knows how the other sees besides nobody can compare alternatives to intraocular lenses therefore if the patient is in a very adverse situation in his vision many of the basic movements he has already lost then any improvement is profit. This was not the 69 years old patient's situation before surgery. Monovision surgery only serves to prove the human being's adaptive power to stay alive.

After monofocal surgery, the patient cannot, without the use of corrective lenses, drive her vehicle or walk on the street safely [19, 20], in addition to losing the image fusion, blurred image [20] and, consequently, exposing herself to macular degeneration [15, 16], the increase in intraocular pressure (glaucoma) [2, 5, 10, 12] and, with corrective lenses, the 69-year-old patient suffers discomfort for read and headaches, today she prefers to abstain of read because of the great visual discomforts.

Monovision surgery and bilateral monofocus surgery do not interfere in the surgeon's fees or in the surgical costs of the clinic or health plan, in addition to not interfering in the values negotiated by the implanted lenses, so monovision surgery does not bring any financial advantage and can bring unrecoverable damage to the patient, why, in secret for the patient, use monovision surgery without any scientific basis?


**5. Bioaccumulation and bacteria resistance genes**

Antibiotics like amoxicillin are used not only for treating human health issues; they are also wide used in livestock farming and fish farming for treating diseases. The improper admin‐ istration of theses pharmaceutical compounds may lead to the occurrence of these drugs in food supplies [4, 78, 94]. Over the last decades, the occurrence of antibiotics in tissues of aquatic organisms has raised the interest of different organisations around the globe, particularly the FDA in USA. It has been reported that continuous exposure to these pharmaceutical com‐ pounds may result in accumulation of the parent compound, their metabolites or both in tissues of aquatic organisms [95].

Due to the risk associated with direct and indirect effects on human health due to both passive and active consumption of antibiotics has lead to set regulations on the use of some antibiotics and the establishment of maximum residue limits. The US official limit tolerance for amoxi‐ cillin residues is 0.01ppm (10 ppb o 10ng/g) in milk and uncooked cattle tissue; however, no tolerance has been established for amoxicillin residues in fish tissues at the present time [78, 95, 96].

It is important to remark that the presence of these drugs in animal tissues can have undesirable effects on consumer health such as allergies; however, the main problem related with the presence of this antimicrobial compounds in fish tissues is the non-controlled ingestion of antibiotics, possibly inducing resistance in bacterial strains [4, 66, 94, 95].

It has been recently shown an exchange of genes for resistance to antibiotics between bacteria in the aquaculture environment and bacteria in the terrestrial environment, including bacteria of animals and human pathogens [4, 97–99]. Therefore, the presence of antibiotics in the aquatic environment can result in the appearances of resistance among human pathogens forming part of its microbiota [4, 100–102].

To sum up the unrestricted use of antibiotics like amoxicillin for any purpose in any country has the potential to affect human and animal health on a global scale; hence, this problem should be dealt through unified local and global preventive approaches [4, 103, 104].


**Abstract**

Nowadays, high security levels are required to transmit critical information for government, private and personal sectors. As a countermeasure, the Quantum Key Distribution systems are the best option in order to protect this information because it provides unconditional security. In addition, increasing the transmission distance is a highlight. Therefore, the Free-Space Optical Quantum Key Distribution systems (FSO-QKD) present an innovative way for sharing secure information between two parties located at ground stations, spacecraft or aircraft. However, these scenarios present several challenges regarding the hardware, protocols and techniques used that must be solved in order to enhance the performance parameters (security level, distance link, final secret key rate, among others) for any QKD system; although, in particular, a high transmission performance is required for both the classical and quantum channels. These issues impose the roadmap and trends in the research, academic and manufacturing sectors around the world.

**Keywords:** performance parameters, secret key, challenges, trends, Quantum Key Distribution

## **1. Introduction**

Currently, crucial information is shared between two parties located either near or far, in the quantum cryptographic context, the transmitter and receiver side are called Alice and Bob, respectively. Therefore, Alice transmits to Bob important information that requires a high secrecy level based on different kind of cryptography systems against a spy system called Eve. In particular, the most secure systems in the practice and theoretically secure are the Quantum Key Distribution (QKD) systems implemented on fiber optical networks and/or Free Space Optics (FSO) links using both Continuous-Variable (CV) and Discrete-Variable (DV) due to they are based on the physics laws [1]. In general, any QKD system requires on the Alice side different "subsystems" such as optical source, quantum state preparation (QSP), modulation scheme (Mod-Sch) and a Digital Processor & Communication (DP&Comm), among other possible subsystems that can improve the overall performance (**Figure 1**). In particular, the optical source has some important physical and technical

requirements that affects the security level; these parameters are the linewidth, quantum optical state generated by the source, wavelength stability, among others. The QSP subsystem is probably the most important subsystem because it intends to prepare a true and well-knowledge quantum state that will be used for encoding the key, that is, to ensure the generation and fidelity features of the quantum state, although some QKD systems impose these requirements to an optimum optical source selection. Regarding the DP&Comm subsystem, many classical technologies are used for digital processing (e.g. central processing unit (CPU), graphical processing unit (GPU), field programmable gate array (FPGA)) in order to implement the algorithm for controlling Mod-Sch subsystem and perform a distillation algorithm for each particular protocol used in QKD systems. On the other hand, the DP&Comm also uses classical telecommunication techniques (e.g. Radio frequency, fiber optics link, FSO links, copper transmission lines) based on a classical and public transmission channel. In addition, the Mod-Sch subsystem uses the output signal of the QSP in order to modify some characteristics (e.g. polarization, amplitude, phase, among others) according to the driving output signal of the DP&Comm. After that, the quantum state that carries information is transmitted through a quantum private channel (fiber optics or free space). At the Bob's side, an optical receiver with support of many optical passive devices receives the quantum optical state and, thus, generates an electrical output signal that will be fed to a demodulation scheme (Demod-Sch). In this case, Bob also has a DP&Comm subsystem with the same characteristics and similar tasks in comparison with the used in Alice.

In addition, Quantum State Determination/Performance Parameters (QSP/PP) subsystem is used for: (a) determining the optical quantum state received by Bob based on optical tomography or calculating the density matrix, or, (b) measuring some important performance parameters of the quantum state received, such as amplitude, phase, polarization, among others, without reconstructing the phase representation state or the density matrix. There exist many subsystems that can improve the performance of QKD systems according to specific conditions, however, this chapter only mentions the most important ones based on authors opinion. On the other hand, Eve system also needs different subsystems in order to "listen" the information from Alice and Bob systems. Therefore, in order to reach the secure level imposed by the physical laws, highend technology is required in each subsystem mentioned concerning hardware (i.e. subsystems mentioned), protocols, novel materials among others highlight topics [2].

### **Figure 1.**

*General block diagram of QKD system emphasizing in the subsystems required for both quantum and classical channel.*

**27**

*Free-Space-Optical Quantum Key Distribution Systems: Challenges and Trends*

Therefore, this chapter explains the state-of-art and actual challenges of each

As mentioned above, although QKD systems are unconditionally secure based on laws of quantum mechanics, it is necessary to understand the technological limit of high-end hardware to increase the research, innovation and development activities in order to reach the theoretical performance of a QKD system step by step. In fact, technical limitations and imperfections in the hardware used gives Eve the opportunity to implement some Side-Channel-Attacks (among other attack kinds)

The most desired optical source for the technical and scientific sector is the single-photon source or on-demand optical source which emit photons at any arbitrary time related to the transmission rate in a deterministic way (not probabilistic), that is, in an ideal case, 100% for emitted a certain photon and 0% for multiple-photons emitted, among others desired features. Thus, many optical sources intend to be a practical single-photon source based on faint laser pulse concept, however, it is not possible to ensure the amount of photons because the probabilistic analysis was made based on the Poisson distribution of the optical signal. On the other hand, there are other type of sources that try the same, but the difference relies in the theory and experiments used in order to generate a single photon. For example: (a) isolated quantum dot systems based on different material such as GaN, CdSe/ZnS, among others. However, these systems are not suitable for C-optical band (i.e. working from ≈340 nm to ≈950 nm) where the conventional telecommunication systems (and QKD systems) work and present a low emission efficiency (from ≈0.02 to ≈0.1) [3, 4]. Although it presents an important feature in single-photon sources, that is the deterministic resolving manner; (b) probabilistic single-photon sources based on Parametric Down-Conversion (PDC) and Four-Wave Mixing implemented in bulk crystals/waveguides and optical fiber, respectively. However, the principal issue is the reduced emission efficiency (from ≈ 0.1 to ≈ 0.85) although they are higher than the systems mentioned in (a). Obviously, this technical option is different compared to the ideal concept of a single-photon source that expects a perfect emission probability for a unique photon; and (c) faint laser is the most useful technique because it relaxes the design and complexity of the implementation of an experiment in both real and laboratory scenarios. This technique presents an emission efficiency of ≈1 and a wide inherent bandwidth suitable for

the immersion of QKD systems in the real optical networks [4].

Thus, for all the optical sources mentioned, the efficiency and non-linear optical elements are an important issue for design and manufacturing. It is also important

subsystem and devices used in QKD systems for both classical and quantum communications involved in this kind of secure systems. The aforementioned information can help to the reader to visualize and establish a general roadmap of the technologies used in QKD systems in order to focus institutional activities to research, development and innovation to contribute to the scientific and technical sector around the world. This chapter are organized as follows: Sections 2.1, 2.2 and 2.3 show the state-of-art regarding optical sources, optical detector and digital processing systems, respectively. Sections 2.1.1, 2.2.1 and 2.3.1 describe the actual challenges in each particular subsystem and the scientific and technological trends,

*DOI: http://dx.doi.org/10.5772/intechopen.81032*

emphasizing the FSO applications.

based on the non-idealities.

**2.1 Optical sources**

**2. High-end hardware: challenges and trends**

*Free-Space-Optical Quantum Key Distribution Systems: Challenges and Trends DOI: http://dx.doi.org/10.5772/intechopen.81032*

Therefore, this chapter explains the state-of-art and actual challenges of each subsystem and devices used in QKD systems for both classical and quantum communications involved in this kind of secure systems. The aforementioned information can help to the reader to visualize and establish a general roadmap of the technologies used in QKD systems in order to focus institutional activities to research, development and innovation to contribute to the scientific and technical sector around the world. This chapter are organized as follows: Sections 2.1, 2.2 and 2.3 show the state-of-art regarding optical sources, optical detector and digital processing systems, respectively. Sections 2.1.1, 2.2.1 and 2.3.1 describe the actual challenges in each particular subsystem and the scientific and technological trends, emphasizing the FSO applications.

## **2. High-end hardware: challenges and trends**

As mentioned above, although QKD systems are unconditionally secure based on laws of quantum mechanics, it is necessary to understand the technological limit of high-end hardware to increase the research, innovation and development activities in order to reach the theoretical performance of a QKD system step by step. In fact, technical limitations and imperfections in the hardware used gives Eve the opportunity to implement some Side-Channel-Attacks (among other attack kinds) based on the non-idealities.

### **2.1 Optical sources**

*Quantum Cryptography in Advanced Networks*

requirements that affects the security level; these parameters are the linewidth, quantum optical state generated by the source, wavelength stability, among others. The QSP subsystem is probably the most important subsystem because it intends to prepare a true and well-knowledge quantum state that will be used for encoding the key, that is, to ensure the generation and fidelity features of the quantum state, although some QKD systems impose these requirements to an optimum optical source selection. Regarding the DP&Comm subsystem, many classical technologies are used for digital processing (e.g. central processing unit (CPU), graphical processing unit (GPU), field programmable gate array (FPGA)) in order to implement the algorithm for controlling Mod-Sch subsystem and perform a distillation algorithm for each particular protocol used in QKD systems. On the other hand, the DP&Comm also uses classical telecommunication techniques (e.g. Radio frequency, fiber optics link, FSO links, copper transmission lines) based on a classical and public transmission channel. In addition, the Mod-Sch subsystem uses the output signal of the QSP in order to modify some characteristics (e.g. polarization, amplitude, phase, among others) according to the driving output signal of the DP&Comm. After that, the quantum state that carries information is transmitted through a quantum private channel (fiber optics or free space). At the Bob's side, an optical receiver with support of many optical passive devices receives the quantum optical state and, thus, generates an electrical output signal that will be fed to a demodulation scheme (Demod-Sch). In this case, Bob also has a DP&Comm subsystem with the same

characteristics and similar tasks in comparison with the used in Alice.

In addition, Quantum State Determination/Performance Parameters (QSP/PP) subsystem is used for: (a) determining the optical quantum state received by Bob based on optical tomography or calculating the density matrix, or, (b) measuring some important performance parameters of the quantum state received, such as amplitude, phase, polarization, among others, without reconstructing the phase representation state or the density matrix. There exist many subsystems that can improve the performance of QKD systems according to specific conditions, however, this chapter only mentions the most important ones based on authors opinion. On the other hand, Eve system also needs different subsystems in order to "listen" the information from Alice and Bob systems. Therefore, in order to reach the secure level imposed by the physical laws, highend technology is required in each subsystem mentioned concerning hardware (i.e. subsystems mentioned), protocols, novel materials among others highlight topics [2].

*General block diagram of QKD system emphasizing in the subsystems required for both quantum and classical*

**26**

**Figure 1.**

*channel.*

The most desired optical source for the technical and scientific sector is the single-photon source or on-demand optical source which emit photons at any arbitrary time related to the transmission rate in a deterministic way (not probabilistic), that is, in an ideal case, 100% for emitted a certain photon and 0% for multiple-photons emitted, among others desired features. Thus, many optical sources intend to be a practical single-photon source based on faint laser pulse concept, however, it is not possible to ensure the amount of photons because the probabilistic analysis was made based on the Poisson distribution of the optical signal. On the other hand, there are other type of sources that try the same, but the difference relies in the theory and experiments used in order to generate a single photon. For example: (a) isolated quantum dot systems based on different material such as GaN, CdSe/ZnS, among others. However, these systems are not suitable for C-optical band (i.e. working from ≈340 nm to ≈950 nm) where the conventional telecommunication systems (and QKD systems) work and present a low emission efficiency (from ≈0.02 to ≈0.1) [3, 4]. Although it presents an important feature in single-photon sources, that is the deterministic resolving manner; (b) probabilistic single-photon sources based on Parametric Down-Conversion (PDC) and Four-Wave Mixing implemented in bulk crystals/waveguides and optical fiber, respectively. However, the principal issue is the reduced emission efficiency (from ≈ 0.1 to ≈ 0.85) although they are higher than the systems mentioned in (a). Obviously, this technical option is different compared to the ideal concept of a single-photon source that expects a perfect emission probability for a unique photon; and (c) faint laser is the most useful technique because it relaxes the design and complexity of the implementation of an experiment in both real and laboratory scenarios. This technique presents an emission efficiency of ≈1 and a wide inherent bandwidth suitable for the immersion of QKD systems in the real optical networks [4].

Thus, for all the optical sources mentioned, the efficiency and non-linear optical elements are an important issue for design and manufacturing. It is also important

to remember that the optical sources described have to be suitable for FSO links where a complete QKD system is implemented, that is, the restriction of singlephoton is crucial for support the secure aspect inherent in QKD systems, however, the FSO links imposes trade-off that have to be analyzed. For this reason, the faint pulse is the common technique for FSO applications. Until now, the single-photon source information presented has been analyzed based on certain particular characteristics. However, an important aspect is the quantum state of the single photon generated by the optical source, that is, a photon can be generated with a particular quantum state (related to a quasi-probabilistic density functions) such as coherent, Fock, entanglement, among others. In fact, an ideal single-photon deterministic source should be generating a single photon with Fock distribution. On the other hand, an entanglement "single-photon" (probabilistic way) can be used in some short-distance-FSO-QKD systems and laboratory considering a high efficiency channel and finally, a single-photon source with coherent state (faint laser) is the most useful source and distribution used for long distance free space links.

### *2.1.1 Challenges and trends*

In general, the challenges in the actual optical sources are regarding the band telecommunication of the device, inherent bandwidth, emission efficiency and output spatial mode. Therefore, the important advance imposes a clear trend based on efficient optical sources at common telecom wavelengths (i.e. C-band) [5]. Although sources at O-band are available [6]. Basically, the improved performance of the optical sources is based on the use of novel materials, structures and quantum devices that permits the near-ideal quantum state generation [7].

### **2.2 Optical detector**

An ideal single-photon detector is useful in QKD systems in order to detect and resolve (determinate) an amount of photons per observation time (related to bit), that is, the detector is enabled to detect a single-photon and determine the exact quantity of a single-photon. However, this definition is based on the assumption of an ideal single-photon source. Obviously, ideal single-photon source and detector permits directly assure specific security levels based on the detection of an Eve system that disturbs the amount of photons transmitted by Alice. However, due to physical characteristics of the materials used on the manufacturing, there are deviations between the idealistic and realistic performance parameters. Thus, many realistic single-photon detectors have the ability of distinguish between zero photons per bit and more than zero photons, but they do not resolve the amount of photon. Based on the above, the most common used single-photon detectors are the nonphoton-number-resolving detectors, that is, they have the ability of detecting photon but do not resolving the exact amount of photons. However, there are different modes of operation based on multiple detectors that allow improving the resolving process. Some examples about single-photon detector proposals are: (a) the Photo-Multiplier Tube (PMT) which is a classical single-photon detector that operates from the visible region to the infrared. However, the detection efficiency is considerably reduced, for example, at 500 nm the efficiency is 0.4, while for 1550 nm is 0.02; meaning a major problem for its application in some real optical networks; (b) Single-Photon Avalanche Photodiode (SPAP) category has a wide variety of technical options for detection process, having minimum and maximum efficiencies from 0.40 to 0.74 for 450–780 nm band, respectively (based on Silice). In both cases (i.e. a and b options), the wavelength range is not completely suitable for FSO communications systems, although some beacon systems can use these detectors with previous analysis.

**29**

*2.3.1 Challenges and trends*

*Free-Space-Optical Quantum Key Distribution Systems: Challenges and Trends*

Therefore, SPAP based on InGaAs material is suitable for 1060–1550 nm range with maximum efficiency of ≈0.33 for 1060 nm and ≈0.10 at 1550 nm. Regarding the high-end technology, the superconducting Transition Edge Sensor (TES) is the best option for detecting in FSO-QKD system context based on the detection efficiencywavelength relationship, that is, efficiency of ≈0.95 at 1556 nm. However, the operation temperature is extremely low, ≈0.1°K, whereas the last mentioned detectors work commonly from 240 to 300°K, although there are some exceptions [4].

The principal challenges are related to minimizing the electronic noise and maximizing the gain of the detector maintaining high transmission rates [8, 9]. To do the aforementioned, novel materials and electrical designs are required. In particular, reducing the Noise Equivalent Power (NEP) parameter permits the detection of low optical power with different electrical bandwidth [10]. However, although novel optical detectors have been developed, coherent detection techniques have been helps at Bob side, relaxing the detector selection due to inherent

The DP&Comm subsystem implemented in conventional QKD systems performs particular basic tasks such as: driver for different devices (e.g. phase and amplitude modulators, true random number generator (TRNG), etc.), quantum key data base, perform the algorithm need to distillation, reconciliation and privacy amplification processes between Alice and Bob. In particular, this algorithm requires access to both quantum and classical channels. Therefore, the DP&Comm requires some important technical specifications so as not to degrade the secure level and secrete key rate of the QKD systems. In particular, Field Programmable Gate Arrays (FPGA) have been used in a real-time QKD systems reaching secret key rate at 17 kb/s in an optical fiber link of 20 Km [11]. It is clear that, the FPGA specifications impact the performance of a QKD systems, therefore, improved synchronization and jitter methods based on high speed and precision devices can reduce the Quantum Bit Error Rate (QBER) and increase the final secret key rate [12].

In addition, the secret key rate has an important relation with the performance of the TRNG subsystems, thus, FPGAs have been used for generation and acquisition of true random digital sequences reaching 1.25 Gb/s [13]. An important issue in DP&Comm subsystems is the ability to adapt and generate countermeasures to maintain or improve the specific performance against external dynamic factors such as atmospheric turbulence in FSO links, resizing and adaptive parameters based on an optimization process [14, 15]. In addition, some QKD systems use a Graphics Processing Unit (GPU) as a DP&Comm (although some considerations have to be analyzed to complete all the task of the DP&Comm) because it provides some important technical features such as parallel computing and processing floatingpoint information allowing rates of 1.35 Gb/s [16]. The novel standalone modules for particular stages of the protocol used (e.g. sifting, error correction, and privacy amplification modules) also support the performance of QKD systems, which are based on high-end electronic design. These particular technical innovations in

specific modules permits reaching secret key rate of ≈13.72 Mb/s [17].

Thus, the DP&Comm subsystem depends on the electronic development regarding the high performance related to speed processing and the novel design

amplification and spectrum filtering of the coherent technique.

*DOI: http://dx.doi.org/10.5772/intechopen.81032*

*2.2.1 Challenges and trends*

**2.3 Digital processing systems**

### *Free-Space-Optical Quantum Key Distribution Systems: Challenges and Trends DOI: http://dx.doi.org/10.5772/intechopen.81032*

Therefore, SPAP based on InGaAs material is suitable for 1060–1550 nm range with maximum efficiency of ≈0.33 for 1060 nm and ≈0.10 at 1550 nm. Regarding the high-end technology, the superconducting Transition Edge Sensor (TES) is the best option for detecting in FSO-QKD system context based on the detection efficiencywavelength relationship, that is, efficiency of ≈0.95 at 1556 nm. However, the operation temperature is extremely low, ≈0.1°K, whereas the last mentioned detectors work commonly from 240 to 300°K, although there are some exceptions [4].


*<IP_ADDRESS> Cultural methods*

Field sanitation is most effective method in melon fruit fly management. It should be done for minimising pest intensity and to break reproduction cycle by removal and destruction of infested fruits daily from the field and bury the damaged fruits 0.46 m deep into the soil [8]. Akhtaruzzaman et al. [9] recommended bagging of cucumber fruits after 3 days of anthesis and bag should be kept for 5 days for effective control. Bagging of 3–4 cm long fruits with two layers of paper bags reduces fruit fly infestation and enhances the net returns by 40–58% [10]. 2–3 rows of maize as a trap crop can be grown between the cucurbits, which can be used as a resting site by the adult fruit fly. Spraying of any contact insecticides can be done on maize during the evening hours to kill adult fruit flies.


*Supporting open minds since 2005*

The Burden of Respiratory Syncytial Virus Infection in the Young http://dx.doi.org/10.5772/intechopen.78206 Edited by Bernhard Resch

#### Contributors

Muhammad Shafique, Muhammad Zahoor, Muhammad Imran Arshad, Bilal Aslam, Abu Baker Siddique, Muhammad Hidayat Rasool, Muhammad Usman Qamar, Muhammad Usman, Bosco Paes, Xavier Carbonell-Estrany, Barry Rodgers-Gray, Fariba Rezaee, Debra Linfield, Maja Daurach, Julian Legg

#### © The Editor(s) and the Author(s) 2019

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Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book.

First published in London, United Kingdom, 2019 by IntechOpen IntechOpen is the global imprint of INTECHOPEN LIMITED, registered in England and Wales, registration number: 11086078, 7th floor, 10 Lower Thames Street, London, EC3R 6AF, United Kingdom Printed in Croatia

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**Abstract**

Saline-affected rice (*Oryza sativa* L.) production environments in Sri Lanka can be divided into three categories including: late-season salinity in irrigated mega-cultivation environments during the minor cultivation season where soil EC ≥7 dSm1 , late season salinity in rain-fed farming systems in the west, southwest, and eastern coastal line during the minor cultivation season where soil EC ≥20 dSm1 , and early season salinity in selected irrigated and rain fed sites during major and minor cultivation seasons as a result of residual overload of salts that was not washed off due to inadequate rain. In the west and southern coast early season salinity salinity can exceed EC ≥12 dSm1 . The proposed zones of saline-afflicted production environments permit designing of target ideotypes and locally adapted rice varieties. Accordingly, high yielding, 3 to 3.5 months duration varieties that are tolerant at >7 dSm1 are recommended for intensive irrigated farming systems affected due to late season salinity (panicle initiation stage of the crop, PI); high yielding, 2.5 to 3 months duration varieties can avoid late season salinity in intensive irrigated farming, and varieties tolerant up to EC = 12 to 20 dSm1 throughout the crop life including seedling and PI stages can target saline affected, semi-subsistence rice cultivation in rain-fed systems. In fact, secondary salinization in local rice farming environments is resulting from interaction among multiple factors; therefore, systemlevel interventions are necessary to manage the impacts.

**Keywords:** secondary salinization, rice (*Oryza sativa* L.), rice cultivation seasons, saline tolerant germplasm, system interventions


Preface

As a simple interpretation, sustainability can be described as either a process or a state that can be maintained at a certain level for as long as it is wanted. The term is associated with that proposed by the Bruntland Commission as "Sustainable Development," which is defined as development that "meets the needs of the present without compromising the ability of future generations to meet their own needs." Thus, "sustainability" is the study of how natural systems function, remain diverse, and produce everything they need for the ecology to remain in balance. However, in addition to natural resources, we also need social and economic resources; sustainability is not just environmentalism. Maintaining sustainability in any economic system is very important, and even more so in the context of developing countries. This book presents some case studies and methodological issues with a focus on developing countries. Part 1 includes studies on conceptual frameworks related to sustainability as well as methodologies relevant to its investigation. Part 2 includes case studies dealing with sustainability applications. Chapter 1 is a description of the people-centered social totality approach, which was applied to low-income housing policy. Since sustainability has three pillars (economic, social, and environmental), use of a multi-criteria decision-making tool is very appropriate. Chapter 2 examines such a tool. Chapter 3 presents an integration of the water-food-energy nexus, since natural resources are used for more than one purpose in an economic system requiring their integration. Chapter 4 examines the use of natural resources in rural areas, using herbicides as a case study. Part 2 begins with Chapter 5, which describes the issue of governance. Chapter 6 describes some of the activities that might lead to sustainability, and finally, Chapter 7 provides a description of sustainability status. The editor hopes that contributions would be of some interest not only for professional in developing countries but also in developed countries.

**II**

**Chapter 7 99**

An Empirical Study on Environmental Sustainability in Melaka City

*by Noor Mohammad*

**Dr. Surendra N. Kulshreshtha** University of Saskatchewan, College of Agriculture and Bioresources, Department of Agricultural and Resource Economics, Saskatoon, Canada

**1**

Section 1

Concepts and Methods

Section 1