High sensitivity direct detection receiver with a 1.5micron optical pre-amplifier.

A 1.5micron optical pre-amplifier was used to improve the sensitivity of a PIN-FET receiver by 12 dB. The resonant optical amplifier provided 17 dB of fiber to fiber gain including coupling losses in an isolator and a narrowband optical filter. The achieved sensitivity, -45.6 dBm at 500 Mbit/s, or 420 photons/bit is the best reported for any direct detection receiver and a factor of two better than previous results using optical amplifiers. However, the results are virtually identical to the best APD receiver results.