High-sensitivity FSK signal detection with an erbium-doped fiber preamplifier and Fabry-Perot etalon demodulation

A report is presented on a 622-Mb/s optical transmission system with demodulation of alternate mark invert (AMI) encoded frequency shift keying (FSK) signals by a Fabry-Perot etalon. A 25-dB gain erbium-doped fiber preamplifier gave a receiver sensitivity of -40 dBm at 10/sup -9/ BER, which was improved to -44 dBm with the addition of a narrowband optical filter. The theoretical sensitivity of the preamplified receiver and the effect of the etalon on the amplified spontaneous emission beat noise are discussed and related to experiment.>