Optical Fiber Polarization Control System Based On The Electro-Optic Crystals

Automatic endless polarization controller is a very important component in high-speed optical communication systems. For 40G/s and above high-speed fiber communication, the polarization dependent loss (PDL) will become more and more sensitive and seriously affects the quality of the communications; it has become a bottleneck in the optical fiber transmission rate increase. High-speed polarization controllers can quickly compensate signal injury caused by PDL and gain any state of polarization at the fiber output; it can significantly improve communication system performance, now it is one of the important issues in the field of high-speed optical fiber communication.In this thesis, the research progress of polarization controller is reviewed, the basic theory of polarized light is introduced, the electro-optic and the effects of electro-optic crystals is discussed, and the polarization controllers, which are based on electro-optic crystal, are investigated. We analyzes the currently feedback control algorithms used in the polarization controller, and on this basis propose a new method of polarization control feedback algorithm based on Particle Swarm Optimization (PSO) to solve the defects of the original algorithm, such as poor convergence and long time consuming search. It can reduce convergence time and improve the response speed of the polarization controllers.In this work, a hardware system design for polarization control was completed. It is based on TI's TMS320F2812DSP chip, combines with in-line polarization detection module. The PolaDetect module outputs four analog voltages which contains the information of the state of polarization, then the system uses the ADC module built in DSP chip to complete four analog voltage acquisition. The main work of DSP module is completing the polarization control algorithm processing and output four voltages to drive the electro-optic crystal by DA module, all parts of above form a closed loop control system of the optical polarization. We used existing equipment to build a platform for polarization control experimental, this experimental system validate the hardware circuit and the polarization control algorithm, the results show that it can complete real-time control of the state of polarization. Although the stability and accuracy of this experimental system needs to be improved, but the whole design idea are of important reference value to the research and development of novel polarization controllers.