Chromatic Dispersion Induced PM-AM Conversion and Its Application in the All-Optical Clock Recovery of NRZ-DPSK Signals

摘要

We investigated the property of conversion between phase modulation (PM) and amplitude modulation (AM) in optical fiber transmission link due to chromatic dispersion (CD) for the purpose of clock information generation. As a result, a novel all-optical clock recovery (CR) scheme from 10 Gbps non-return-to-zero differential phase-shift-keying (NRZ-DPSK) signal has been demonstrated experimentally. We introduce a chromatic dispersion induced clock tone from the NRZ-DPSK signal and feed it into a free-running semiconductor optical amplifier (SOA) based fiber ring laser to achieve an injection mode-locking. The generated mode-locked pulse is the corresponding regenerated clock of the original signal. Since no special component is required for NRZ-DPSK demodulation, our proposed method is very promising because of its simple configuration and higher stability. In experiments, 20km standard single mode fiber is employed to accumulate CD and generate PM-AM conversion hence regenerate clock tone of the NRZ-DPSK signal. The recovered clock signal with the extinction ratio over 15 dB and the root-mean-square timing jitter of 720 fs is achieved under 2~(31)-1 pseudorandom binary sequence NRZ-DPSK signals measurement. We also demonstrated a similar CR system by using a chirped fiber Bragg grating (CFBG) as the dispersion device. With the same operation principle, it is quite convenient and promising to extend our configuration to implement all-optical CR for NRZ-DPSK signal with data rate up to 40Gbps.