A New Parallel Carrier Recovery Architecture for Intradyne Coherent Optical Receivers in the Presence of Laser Frequency Fluctuations
In this paper, the authors introduce a new parallel carrier recovery architecture suitable for ultra-high speed intradyne coherent optical receivers (e.g., 40Gb/s). The proposed scheme combines a novel low-latency parallel Digital Phase Locked Loop (DPLL) with a feed-forward Carrier Phase Recovery (CPR) algorithm. The new low-latency parallel DPLL is designed to compensate not only frequency offset, but also frequency fluctuations such as those induced by mechanical vibrations. It is well-known that nonzero frequency offset leads to higher phase error variance in a feed-forward CPR. Furthermore, it has been recently shown that laser frequency instability caused by mechanical vibrations significantly degrades the performance of CPR. Other effects such as power supply noise may also introduce laser frequency fluctuations.