激光器频偏和相位噪声是限制COOFDM（相干光正交频分复用）系统性能的重要因素。文章提出了COOFDM系统中基于差分预编码和MCDD (多载波差分检测)算法的激光器相位噪声和频偏联合补偿方案。对COOFDM系统中的频偏和激光器相位噪声作用机理和基于MCDD的补偿方案机制进行了理论推导，并在不同的光信噪比、激光器频偏和线宽条件下进行了系统仿真。仿真结果表明，基于差分预编码和MCDD的联合补偿方法对COOFDM系统中的激光器频偏和相位噪声有较好的补偿效果和较大的补偿范围，在不引入系统开销的同时，可有效改善COOFDM系统性能。

Laser frequency offset and phase noise are important factors that limit the Coherent Optical Orthogonal Frequency Division Multiplexing (COOFDM) system performances. This paper proposes a novel scheme based on differential precoding and MultiCarrier Differential Detection (MCDD) algorithm, which can jointly compensate the laser phase noise and frequency offset, theoretically derives the principle of the frequency offset and laser phase noise in COOFDM systems and the working mechanism of the MCDDbased compensation scheme, and conducts system simulations in different OSNRs, laser frequency offsets and linewidths. The simulation results indicate that this scheme has good compensation effects and large compensation scope and effectively improves the COOFDM system performances even without introducing extra system overhead.