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提出并建立了一种新型的基于光纤四波混频效应和压控光脉冲源的光锁相环路(OPLL),用于光时分复用系统(OTDM)中的时钟恢复过程。从理论上分析了其工作原理,及各模块结构和功能。利用高非线性光纤中的四波混频效应实现全光鉴相器,有效缩短了光纤长度,减小了光纤色散引起的脉冲走离,鉴相器消光比超过30 dB。采用再生锁模光纤激光器实现压控光脉冲源,在保证脉冲质量的前提下,重复频率调节范围达到380 kHz。在40 Gb/s时钟恢复实验中,获得脉宽为7.2 ps、接近变换极限的时钟脉冲,时间抖动(RMS)为152 fs,超模抑制比大于60 dB。实验证明,输入信号幅度波动和码型效应对环路影响很小。
A new type of optical phase locked loop (OPLL) based on optical four-wave mixing effect and voltage-controlled optical pulse source is proposed and established for the clock recovery process in optical time division multiplexed system (OTDM). From the theoretical analysis of its working principle, and the structure and function of each module. The use of four-wave mixing effect in high-nonlinearity optical fiber to realize the all-optical phase discriminator effectively shortens the optical fiber length and reduces the pulse departure caused by the optical fiber dispersion. The extinction ratio of the phase discriminator exceeds 30 dB. The regenerative mode-locked fiber laser is used to control the voltage pulse source. Under the condition of ensuring the pulse quality, the repetitive frequency adjustment range reaches 380 kHz. In a 40 Gb / s clock recovery experiment, a clock pulse with a pulse width of 7.2 ps approaching the conversion limit was obtained with a time-jitter (RMS) of 152 fs and an over-mode rejection ratio of greater than 60 dB. Experiments show that the input signal amplitude fluctuations and pattern effects have little effect on the loop.