A 42.7-Gb/s integrated balanced optical front end with record sensitivity

We have demonstrated a record sensitivity of -36.9 dBm (39 photons/bit) for a BER of 10/sup -9/ at 42.7-Gb/s using an integrated balanced optical front end. Results were obtained using optical preamplification of RZ-DPSK modulation and an external delay-interferometer. The OSNR requirement was measured to be 17.0 dB in a 0.1 nm bandwidth.