Polarization-insensitive all-optical time-division demultiplexing using a fiber four-wave mixer with a peak-holding optical phase-locked loop

We demonstrate a simple scheme for the all-optical time-division demultiplexer, featuring a polarization-independent optical gate and a peak-holding optical phase-locked loop (PLL) for clock recovery. A fiber four-wave mixer (FWM) is employed as an optical gate. The polarization insensitive operation is achieved by the polarization diversity scheme, where only a short piece of polarization-maintaining fiber is attached to the input port of a conventional fiber FWM. By using the peak-holding optical PLL, the clock pulse is locked to the peak position of the incoming signal pulse. In such a case, a single optical gate acts as the gate switch for time-division demultiplexing as well as the phase detector for phase locking; therefore, the system configuration is greatly simplified. The all-optical time-division demultiplexer we develop enables us to demultiplex a 160-Gb/s signal into 10-Gb/s tributary channels with polarization sensitivity less than 0.5 dB.