郑国立， 马健新^*， 张岩松

（  北京邮电大学电子工程学院，北京，100876；  ）

摘要： 相干光正交频分复用(CO-OFDM)系统对相位噪声(PN)敏感，后者会引起同相位误差(CPE)和载波间干扰(ICI)。导频可以用于进行相位补偿。然而在实际系统中，梳状导频子载波也会受到相邻的数据子载波ICI影响。针对这种情况，本文提出一种在CO-OFDM系统中的低复杂度的梳状导频设计方案，即在导频子载波两边添加空子载波(也即保护子载波GSs)，用以减小相邻子载波对导频的ICI影响。增加导频周边的GSs数量，可以减小导频所受的ICI，从而使系统得到更好的相位补偿。本文将带有GSs的新型导频设计方案用于20Gbit/s QPSK CO-OFDM的仿真系统，仿真结果显示，在典型情况下经过50km的标准单模光纤传输(SSMF)，该方案可以将接收信号的误矢量幅度(EVM)减小3%。
关键词： 相干光正交频分复用；相位补偿；载波间干扰；相位噪声

ZHENG Guoli， MA Jianxin^*， ZHANG Yansong

（  School of Electronic Engineering,Beijing University of Posts and Telecommunications,100876；  ）

Abstract： CO-OFDM is sensitive to phase noise (PN), which will cause common phase error (CPE) and intercarrier interference (ICI). Pilots are used to compensate for the PN. However, the phase of the comb-type pilot subcarriers (PSs) also suffers the ICI from the adjacent data-bearing subcarriers in real systems. In terms of this issue, a low-complexity comb-type pilot scheme is proposed in CO-OFDM system for testing the impact of the ICI by adding blank subcarriers (also guard subcarriers or GSs) at both sides of PSs. By increasing the number of GSs, the ICI on PSs can be reduced and a better performance of the phase compensation is achieved. The proposed pilot scheme with GSs is employed in a typical 20Gbit/s QPSK CO-OFDM system, and the simulation results show that after 50km standard single-mode fiber (SSMF) transmission in conventional conditions, our scheme can reduce the error vector magnitude (EVM) by about 3%.

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