Saturable-Absorber-Based Phase-Preserving Amplitude Regeneration of RZ DPSK Signals

We experimentally investigate a new generation of multiple-quantum-well semiconductor saturable absorber for all-optical phase-shift-keying signal regeneration. The device under study exhibits a reflectivity which decreases when the input signal power increases. This characteristic can be seen as a power limiting function which could be used for phase-preserving amplitude noise reduction, hence preventing from nonlinear phase noise accumulation along a transmission link. The device efficiency is demonstrated at 42.7 Gb/s; a fiber launched power margin of 2 dB and receiver sensitivity improvement up to 5.5 dB are obtained.