偏振调制微波光子信号处理

Polarization Modulated Microwave Photonic Signal Processing

微波光子信号处理具有带宽大、调谐性好、对电磁干扰不敏感、易于实现并行系统等优点,在过去数十年中受到了学术界的重视。相比于传统的电光相位调制和电光强度调制,偏振调制将待调制信息转换到光的一个二维参量(偏振)上,从而在实现信号处理时可提供更多的自由度和灵活性。在偏振调制器后连接一个检偏器,通过调节检偏器的检偏角去掉偏振调制的一个维度,即可实现相位调制和强度调制,因而任何基于相位调制和强度调制的微波光子信号处理都能基于偏振调制实现。同时,将偏振调制器的输出分成多路,每一个支路上都插入一个检偏器,则基于一个偏振调制器就可同时实现多个调制方式,从而进一步实现并行信号处理或多功能一体信号处理。此外基于单边带偏振调制,可利用非常简单的装置实现幅相无耦合的微波移相器,进而实现相位编码、复抽头系数滤波器、光控相控阵等信号产生或处理功能。本文建立了偏振调制的基本数学模型,并对基于偏振调制的多种微波光子信号处理功能进行了原理分析。

Microwave photonic signal processing has drawn a lot of attentions in the past decades due to the distinct advantages brought by the photonic technology,such as broad bandwidth,large tunability,immunity to electromagnetic interference and capability to perform parallel processing.As compared with the conventional electro-optical phase modulation and intensity modulation,polarization modulation converts（Ratio frequency）RF signal to be processed to an optical parameter with two degrees of freedom（i.e.polarization）.By connecting a polarizer to the polarization modulator,to remove one degree of freedom,the phase modulation and intensity modulation can be easily obtained.As a result,any microwave photonic signal processing based on phase modulation and intensity modulation can be realized based on the polarization modulation.If the output of a polarization modulator is split into several branches and in each branch a polarizer is incorporated,multiple modulation schemes can be implemented simultaneously,which can be used to achieve multichannel or multifunction signal processing.In addition,based on the single sideband polarization modulation,a high performance photonic microwave phase shifter can be realized,which can be further applied to implement phase coding,microwave filtering and beamforming network.This paper will establish a theoretical model of the polarization modulation and describe the principle of the polarization-modulation-based signal processing systems.