Format Conversion From 120-Gb/s RZ-D8PSK to 80-Gb/s RZ-DQPSK Through FWM-Based Optical Phase Erasure

An optical format conversion scheme from 120-Gb/s return-to-zero differential 8-ary phase-shift keying (RZ-D8PSK) to 80-Gb/s RZ differential quadrature phase-shift keying (RZ-DQPSK) is demonstrated by optically removing one tributary through optical phase erasure. It is achieved through four-wave mixing in a highly nonlinear fiber. An 8-dB sensitivity improvement is obtained for the converted DQPSK signal relative to that of the input D8PSK signal. This is potentially useful to enable the interconnection among neighboring networks where different formats are deployed.