Contents 1. Introduction
In recent years, a reconfigurable optical add/drop multiplexing (ROADM) system that is colorless, directionless and contentionless (CDC) has attracted particular attention as regards the flexible operation of optical networks [1]. In addition, a flexible grid wavelength channel plan is becoming important in terms of the allocation of different bit rate signals with different modulation formats [2]. In such a system, it is preferable to deploy a high port-count wavelength-selective switch (HPC-WSS), because it makes it possible to handle a large number of wavelength channels as well as providing a simple system configuration with fewer WSS stages. There have already been several reports on HPC-WSSs that employ, for instance, a 2-dimensional micro-lens-array-based fiber frontend and micro electro-mechanical system (MEMS) mirrors [3], and a Bragg reflector waveguide (BRW) frontend with a liquid crystal on silicon (LCOS) [4]. However, these approaches have certain disadvantages. For example, the MEMS-based WSS cannot deal with a flexible grid channel plan. Although a BRW-based WSS with a LCOS device appears to be an interesting approach since it has a small and simple optics configuration with flexible grid operation, the switching performance still needs to be improved. Our aim of this report is to provide a practical HPC-WSS.
