Research Of Wavelength Selective Switch Based On LCOS

The key component of reconfigurable optical mesh networks now is the 1×N Wavelength Selective Switch(WSS), which manages the routing of the wavelength channels within the network. A novel compact N×M wavelength selective cross-connect(WXC) based on a single liquid crystal on silicon(LCOS) array has been previously reported by Nicolas K. Fontaine et al., but this WXC has some disadvantages which include its large size, its complication to achieve and its needs of single-mode WSS. Thus, it's obvious that the WSS is of great significance for the optical switching field.The techniques to realize WSS include Micro-Electro-Mechanical system(MEMS), liquid crystal(LC), planar light-wave Circuit(PLC) and liquid crystal on silicon(LCOS). For next-generation optical networks, LCOS-based WSS is a very attractive solution. Each pixel of LCOS can be controlled independently by electrode, which can be made full use of by adjusting to parameters of spectrum for WSS, such as programmable characteristics for center wavelength and bandwidth. Because the pixel pitch of the LCOS was limited, and the steering angle cannot meet the need of WSS in the past years, few people studied the WSS with two dimensional beams steering.Compared with other WSS, characters and the development at home and abroad of LCOS-based WSS is researched. Two-dimensional beam steering in LCOS Spatial light modulator(SLM) is also conduct researched in the paper. Phenomenon of two dimensional beam steering in liquid crystal on silicon(LCOS) is demonstrated. The technology can improve the flexibility of WSS. The structure of WSS designed in the paper is simple, and it has the advantage of high flexibility. The system only needs a half-wave plate to realize the polarization conversion. It uses a transmitted blazed grating to separate input wavelength in space. The optical path switching function is achieved by the LCOS spatial light modulator. The transmitted blazed grating has characteristic of polarization-independence, and the system does not need the device which is used to eliminate the polarization dependent for the grating. So, the system structure is simplified.According the optical design, a 1×4 LCOS-based WSS was assembled. The device specifications were tested. The insertion loss is < 6dB. Center wavelength and bandwidth can be programmable. The working wavelength range is 1525nm-1565 nm. Polarization dependent loss is lower than 0.3dB. It can be employed as the key part in a reconfigurable optical add-drop multiplexer(ROADM) and optical cross-connect(OXC).