With the construction and development of Reconfigurable Optical add-drop Multiplexing(ROADM)optical networks,Wavelength Selective Switch(WSS),as the core optical module of ROADM optical node equipment,is highly valued in the field of optical communication.The current ROADM nodes are generally built based on the more mature 1×N port WSS technology.As the scale and capacity of optical networks continue to increase,the problems of numerous components required for this solution,high construction costs,and high-power consumption are becoming increasingly evident.It has become a consensus in the industry to develop M×N port WSS to build a new generation of ROADM nodes.However,the M×N port wavelength selection switch needs to exchange any wavelength signal from the M input ports to the N output ports as needed,requiring two deflections of the incident beam inside the WSS.As a result,the reported M×N port WSS generally face the problems of complex structure,high insertion loss,low spectral manipulation accuracy and no multiplex signal broadcast function,and so far there are no more mature commercialized products.In this paper,we study an M×N port WSS design scheme without lens in the port direction to simplify the optical system in view of the above problems faced by M×N port WSS.The study of the phase gray map generation algorithm loaded by Liquid Crystal on Silicon(LCOS),the realization of the beam control in the port direction,and the proof-of-principle verification of the WSS multiplex broadcast function of the M×N port.A 3×3 port wavelength selection switch experimental system was built,and its performance was tested.The main work accomplished in the thesis is as follows:1.Based on the analysis of the basic structure and working principle of the lensfree wavelength-selective switching system in the port direction,the relationship between the intensity distribution of the optical field on the first pointing plane and the second pointing plane of the liquid crystal is derived based on the Fresnel diffraction theory,which lays the foundation for the subsequent work.2.An LCOS phase gray map with both shine grating and column mirror functions is designed to achieve beam quality control of WSS in the port direction while completing the port switching function of the wavelength selection switch.This method effectively shortens the overall length of the M×N port wavelength selection switch system and reduces the system complexity and insertion loss.3.A phase gray map generation algorithm based on Symmetric Iterative Fourier Transform Algorithm(SIFTA-2)and Genetic Algorithm(GA),including phase and amplitude degrees of freedom,is proposed to implement the LCOS phase gray map generation for wavelength selective switching system signal multicast function,and its effectiveness is verified in principle experiments.4.The experimental system of 3×3 port WSS without lens in the port direction was built to achieve arbitrary wavelength switching between 3 input ports and 3 output ports with a maximum inter-port interpolation loss of 13.2 dB,a minimum channel bandwidth of 16.25 GHz,and a spectral tuning accuracy of 1 GHz. |