Optical homodyne PSK demonstration of 1.5 photons per bit at 156 Mbps with rate-(1/2) turbo coding

We report the first demonstration of a near quantum-limited optical homodyne PSK receiver combined with powerful forward-error-correction coding, achieving 1.5 photons/bit sensitivity, within 4.5 dB of the Shannon limit. Phase-locking was achieved at 1.55 microm using an analog dither-based optical phase-locked loop with an external phase modulator. Analysis for this configuration with arbitrary loop damping is given showing a performance advantage for the overdamped case.