Phase Regeneration of a BPSK Data Signal Using a Lithium Niobate Phase Modulator

We propose a scheme for phase regeneration of an optical binary phase shift keying (BPSK) data signal using a Lithium Niobate (LiNbO₃) phase modulator. The scheme is based on heterodyne detection of the BPSK data signal with a continuous wave local oscillator (CW-LO). Carrier recovery is then achieved in the electrical domain using a ×2 frequency-multiplier and a narrow-band filtering scheme. Subsequently, a superposition of the recovered carrier and the heterodyne detected data signal is used to modulate the CW-LO in a LiNbO3 phase modulator. The result is a parametric mixing process in the optical domain, leading to a phase-regenerated BPSK data signal by the coherent superposition with a phase-inverted copy. The proposed scheme constitutes a compact and stable setup, where active phase-stabilization of the electrical data- and carrier-paths can potentially be avoided. An analytical derivation of the working principle is provided, using Jacobi-Anger expansions to describe the phase-modulation. A proof-of-principle experiment is carried out, demonstrating regeneration of a 10 Gb/s NRZ-BPSK data signal degraded by a 5-GHz sinusoidal phase-noise tone. In the proof-of-principle demonstration, the decorrelated data- and LO-carriers are derived from the same CW source. A preliminary test with separate CW sources for data and LO, but without the required electrical narrow-band carrier filtering, is also included. Finally, numerical simulations of the regenerator performance in the presence of wideband phase- and amplitude-noise are performed.