Study On Demuliplexing Scheme And Polarization Dependent Loss In Polarization Division Muliplexing System

The demands for large capacities and high spectral efficiency communication systems are increasing due to the development of Internet and the appearance of multimedia data service. Polarization Division Multiplexing (PDM) Technology, which can double the spectral efficiency of the transmission system without increasing the system structure complexity, has attracted much attention. Polarization Division Multiplexing combining with High-Order Modulation is applied in most experiments on 100Gb/s transmission system.Except for its great advantage, there are still some drawbacks for PDM Technology. As the SOP of an optical signal changes randomly with wavelength and time and cannot be maintained in a transmission link, an adaptive demultiplexing module is applied in receiver with proper design. It can detect the SOPs of the optical signals in the fiber link and adjust the SOPs to eliminate crosstalk between the two polarization channels. Polarization Dependent Loss (PDL) is also a main factor in 100Gb/s and higher speed PDM systems and the tolerance to PDL is discussible.A theoretic model of the crosstalk in polarization division multiplexing system (PDM) is induced. An adaptive crosstalk elimination scheme is proposed, in which the radio frequency (RF) power of the optical signal related with the crosstalk is used as feedback signal and particle swarm optimization (PSO) algorithm is applied in the control unit to adjust the polarization controller and eliminate the crosstalk. The effectiveness is demonstrated in 2×50Gb/s PDM-DQPSK system. The results show that with the crosstalk elimination scheme the performance of the system is improved remarkably and the BER is reduced greatly. The thesis mainly consists of following work:1) Study on the SOPs of orthogonal optical signals in fiber link, using Jones vector and Stokes vector. A transmission matrix of the crosstalk in the fiber link is induced.2) Study on demultiplexing scheme based on power difference. Propose demultiplexing scheme based on RF power detection, using optical signals mixing theory. Discuss the demuliplexing module in details, including polarization controller, demuliplexing algorithm and the performance of the module.3) Set up 2x50Gb/s PDM-DQPSK transmission system with matlab and Optisystem. Demonstrate the performance of the demultplexing scheme.4) Study on PDL in PDM system and induce the theoretic model. Demonstrate the performance of the optical transmission system with PDL.