Demonstration of 2.1 photon-per-bit sensitivity for BPSK at 9.94-Gb/s with rate-½ FEC

Combining optical-phase-locked loop based coherent detection, interleaving, and powerful rate-½ FEC enabled the error-free transmission of BPSK waveforms at information rates of 9.94-Gb/s and 19.88-Gb/s with sensitivities of 2.1 photons-per-bit and 3.9 photons-per-bit, respectively.