Simultaneous demodulation and clock-recovery of 40-Gb/s NRZ-DPSK signals using a multiwavelength Gaussian filter

Abstract—We demonstrate a novel optical circuit that has the potential of simultaneous demodulation and all-optical clock-recovery of 40-Gb/s wavelength-division-multiplexing nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) signals. A key device of the circuit is an ad hoc periodic fiber Bragg grating filter that simultaneously demodulates the input signals and seeds a series of clock recovery circuits. We report the complete characterization of the proposed scheme in the whole -band using a tunable transmitter. The DPSK demodulated signals show enhanced resilience to chromatic dispersion with respect to the usual NRZ ON–OFF keying format. On the other hand, the recovered clock signals are very stable and have around 200-fs root-mean-square time jitter. Index Terms—All-optical clock recovery, phase modulated format, semiconductor optical amplifier (SOA). I