光纤传输系统中基于相位预调制的信号整型

利用相位预调制技术解决高速长距离光纤传输系统中面临的接收灵敏度降低和色散容限问题。通过在发射端对非归零(NRZ)的光信号进行比特同步相位预调制,使非归零码在传输过程中得到波形重整,演变为归零(RZ)的波形,从而提高眼图开启度。实验观测了普通非归零码和相位预调制的非归零码在不同相位调制深度和色散下的光谱、眼图和功率代价。10Gb/s的传输结果表明,链路色散绝对值小于1000ps/nm时,施加相位预调制的非归零信号功率代价小于1dB,比普通非归零信号具有更高的接收灵敏度和更低的色散功率代价。因此,基于相位预调制的信号整型技术可减轻系统对光信噪比和色散管理的要求,延长传输距离。

Signal Shaping Based on Phase Pre-Modulation in Fiber Transmission Systems

Phase pre-modulation is investigated to overcome the impacts of sensitivity reduction and chromatic dispersion in high-speed and long-distance fiber transmission systems. The bit-synchronous phase pre-modulation imposed on non-return-to-zero (NRZ) signals at the transmitter can reshape the NRZ pulse to return-to-zero (RZ) waveform and hence improve the eye opening. Experiments are performed to measure the spectra, eye diagrams and power penalties of conventional NRZ signals and phase-pre-modulated NRZ signals under different modulation depth and dispersion. Results of 10 Gb/s transmission show that the phase-pre-modulated NRZ signals have a power penalty lower than 1 dB with the absolute value of link dispersion less than 1000 ps/nm, exhibiting higher sensitivity and lower dispersion-induced penalty than conventional NRZ signals. This modulation scheme relaxes the requirements to optical signal-to-noise ratio and dispersion management, extends the transmission distance and is easy to implement.