偏振正交法抑制双向传输系统瑞利干涉噪声

Reducing coherent Rayleigh noise using orthogonal polarizationin bidirectional fiber communication system

瑞利后向散射引起的干涉噪声是双向光纤传输系统的主要噪声来源。本文对单模光纤双向传输系统中瑞利后向散射的一般理论和偏振特性进行了分析,并提出了采用偏振正交法减小干涉噪声的方法。建立了10 GHz模拟RF信号单波长双向传输系统,并采用偏振旋转器件实现正、反向传输光的偏振近似正交传输。通过数值模拟,分析了本系统瑞利后向散射偏振状态与入射光偏振状态、反向光偏振旋转角的关系,进一步分析了系统干涉噪声抑制水平。模拟分析结果表明,在80°～90°范围内旋转偏振态,能够使瑞利后向散射降低至少一个数量级;系统信噪比提高了近15倍。利用偏振正交法减小双向传输系统的干涉噪声,有对偏振旋转的精度要求不高、容易操作的优点。

The coherent Rayleigh noise （CRN） induced by Rayleigh backscattered （RB） light and backward trans- ferred light in the fiber is a main noise source in bidirectional communication systems. In this paper,the bidirectional communication system with a single mode fiber for 10 GHz analog radio frequency （RF） signal is set up,and the or- thogonal polarization method for reducing CRN is proposed. Orthogonal polarization communication is achieved by a polarization rotator. The system performance is analyzed by simulation. The simulation results show that CRN of the bi- directional communication system can be diminished by using the method and RB light would decrease by an order of magnitude. Signal to noise ratio （SNR） of the system would increase by 15-fold. The orthogonal polarization method has the advantage of easily adjusting for polarization rotation angle.