Multi-span transmission using phase and amplitude regeneration in PPLN-based PSA

We demonstrated multi-span transmission using a periodically poled LiNbO(3) (PPLN) based phase sensitive amplifier (PSA). An in-line PSA with a carrier recovery and phase locking system is implemented as a repeater amplifier in a recirculating loop. We achieved a PSA gain as high as + 18 dB and a high external gain of + 12 dB for the in-line PSA as a black box. The impairments caused by phase noise resulting from fiber nonlinearity and intensity noise caused by the amplified spontaneous emission (ASE) of an optical amplifier are largely suppressed using the phase and amplitude regeneration capabilities of the PSA. The ultra long-haul transmission of a 28-Gb/s binary phase shift keying (BPSK) signal over 5400 km was achieved with phase and amplitude regeneration.