Research On Polarization Division Multiplexing And Polarization Control Technologies In Optical Fiber Communication

With the rapid development of High-speed Optical Communication system, thepolarization effect in optical fiber becomes increasingly important. First of all, polarizationmultiplexing technique by loading modulated signals in both orthogonal polarization statescan double channel capacity, compared to the scenario of single polarization. Secondly,polarization mode dispersion will affect the performance of high-speed transmission system.Finally, with the development of coherent detection, the polarization tracking is particularlyimportant.This thesis mainly includes two contents：Firstly, research on the realization of highspeed polarization multiplexing system. By multiplexing the25Gbit/s output signal of IQmodulator50Gbit/s output polarization multiplexed signal can be generated. Theperformance of20km transmission has been tested. Secondly, the driving circuit of LiNbO3polarization controller is designed with the Cyclone IV series FPGA chip of Altera companyas the main control chip. High-speed DAC and ADC and the corresponding matching circuitis designed to meet system requirement. This work has completed the schematic and PCBdesign of hardware circuit and has completed the preparation of related software code andhas completed the test job. The effective resolution of the system is more than11bits and theresolution of polarization is larger than0.1rad. Since the operation frequency is relativelyhigh, DAC need to use operational amplifier with current feedback. When the amplificationof the input signal is greater than10MHz, the output one can obtain the gain more than13dB.When it amplifies low frequency signal,33dB gain can be realized. This output signal can befully capable of driving control work of polarization controller.This work analyzes several common methods to realize polarization control. In addition,on this basis of designing the software program, the experimental results are showed that thepolarization control time is less than6ms and the effective tracking speed of polarization ismore than600rad/s.