An SOI based polarization insensitive filter for all-optical clock recovery.

We fabricate and demonstrate a compact polarization insensitive filter for all-optical clock recovery (CR) based on silicon-on-insulator (SOI), which consists of a microring resonator (MRR) and two modified two-dimensional (2D) grating couplers. The distributed Bragg reflectors (DBRs) are introduced to improve the coupling efficiency of the 2D grating coupler. The MRR works as a comb filter for CR, while the 2D grating couplers serve as the polarization diversity unit to achieve a polarization insensitive operation. A subsequent semiconductor optical amplifier (SOA) performs the amplitude equalization. Based on this scheme, a good clock signal with 970 fs timing jitter can be achieved at 44 Gb/s from input signals with arbitrary polarization states.