A Novel Phase-Locking-Free Phase Sensitive Amplifier based Regenerator

We propose a scheme for phase regeneration of optical binary phase-shift keying (BPSK) data signals based on phase sensitive amplification without active phase-locking. A delay interferometer (DI) is used to convert a BPSK signal impaired by noise to an amplitude modulated signal followed by cross-phase modulation (XPM) in a highly nonlinear fiber (HNLF) which transfers the data modulation from the amplitude modulated signal to the phase of a locally generated carrier. By placing the HNLF in a loop a stable phase relation is maintained relative to a set of counter propagating locally generated phase-locked pumps. As a result, active phase-stabilization is avoided. A proof-of-principle experiment is carried out with a dual-pump degenerate phase sensitive amplifier (PSA), demonstrating regeneration for a 10 Gb/s non-return-to-zero differential BPSK (NRZ-DPSK) data signal degraded by a sinusoidal phase-noise tone. Receiver sensitivity improvements of 3.5 dB are achieved at a bit-error-rate (BER) of 10-9. Additionally, numerical simulations are performed comparing the idealized regenerator performance in the presence of sinusoidal phase modulation as well as Gaussian phase-noise.