high accuracy positioning relative to an absolute reference position is provided for a plurality of cores constituting a polymer waveguide array for connection to ferrules at ends of a plurality of these assemblies to form a single - mode polymer waveguide array assembly . a method for forming a single - mode polymer waveguide array assembly enables a plurality of cores constituting a polymer waveguide array to be positioned with high accuracy . also provided is a combination of process molds used in the processes unique to the present methods .