Research On Channelized Tunable Optical Dispersion Compensator Based On Liquid Crystal On Silicon

With the development of optical communication, especially the wide applications ofhigh speed dense wavelength division multiplexing (DWDM) systems, chromatic dispersion(CD) compensation technology is attracting more and more attention. Furthermore theoptical system has been shifting from a point-to-point to a dynamic ring/mesh networks. Insuch an optical network the residue CD may vary channel by channel because of differentrouting paths. Channelized tunable optical dispersion compensator (CTODC) which cancompensate the dispersion dynamically and independently for every single channel thus isconsidered as the enabling device in the future high speed dynamic optical communicationnetworks.In this thesis the development of the CTODCs based on free-space optical structurewere introduced and their mechanism, configurations and key performance parameters areanalyzed and compared. The kind of CTODCs based on liquid crystal on silicon (LCOS) arestudied in detail. In such CTODCs a transmitting diffraction grating and an LCOS chip areemployed as the wavelength dispersing component and spatial light modulator (SLM),respectively, these two elements are located on the front and rear focal plane of a Fourierlens, which constructs a2f system.In this thesis the parameters of the optical collimator, the polarization diversity optics,the Fourier lens and the beam expanding prisms are designed based on the geometrical opticstheory. The angular dispersion of the phase grating and the spectrum of the system wereanalyzed. The relationship between the key performance parameters of the CTODC such asdispersion compensating range, bandwidth and insert loss are analyzed. Furthermore theformula of the coupling loss between the input and output Gaussian field which modulatedby the SLM are deduced by using the wave optics theory. On that basis the integration ofwavelength selective switch (WSS) and CTODC is also discussed. The "rabbit ear"phenomenon in micro electro-mechanical system (MEMS) based CTODC and the way toreduce it are analyzed and presented. The characteristics of LCOS using for a SLM wereanalyzed, the cause of ripples in the transmission spectra, and the method to reduce ripplesare developed.