Review on phase preserving amplitude regeneration for phase-coded signals exploiting FWM in a saturated SOA

All-optical phase-preserving amplitude regeneration is an effective method to reduce nonlinear phase noise in long-haul transmission of phase-modulated signals. Here we review the latest results on a proposed differential phase shift keying (DPSK) regeneration scheme exploiting a compact architecture based on a saturated semiconductor optical amplifier. The scheme allows for amplitude-only signal regeneration with limited excess phase-noise contribution. Both the pass-through (PT) and the four wave mixing (FWM) signals exhibit enhanced Q-factor and margin improvement in bit error rate vs receiver threshold measurements, making the configuration suitable for both wavelength-preserving optical regeneration and wavelength regenerative conversion. The regeneration through FWM has an higher resilience to noise than the PT and its polarization dependency can be eliminated with the implementation of a dual co-polarized pump scheme. Preliminary experiments of simultaneous regeneration of two DPSK data streams are also provided.