Demonstration of 42.7-Gb/s DPSK receiver with 45 photons/bit sensitivity

A record sensitivity of -36.2 dBm at 1552.5-nm wavelength (45 photons/bit) is reported for an optically preamplified receiver operating at 42.7 Gb/s. The transmission format is return-to-zero differential phase-shift keying. The receiver employs a delay-interferometer demodulator followed by balanced-photodiode detection and electronic demultiplexing to 10.7 Gb/s.