High-sensitivity receiver optical preamplifiers

High-receiver sensitivities of -40.9, -44.3, -46.2, -49.0, and -51.3 dBm are reported at 2.4, 1.8, 1.2, 0.62, and 0.14 Gb/s, respectively, using a low-noise, 980-nm diode-pumped, erbium fiber amplifier in the receiver preamplifier configuration with all field usable components. This corresponds to a best sensitivity of 156 photons/bit at the input of the optical amplifier (96 photons/bit at the input of the erbium-doped fiber). Selection of a low-chirp laser-diode transmitter, an optical filter with a bandwidth appropriate for filtering the signal, and a low-noise electrical amplifier with appropriate bandwidth in the post detection stage are all critical to achieve very high-receiver sensitivities