Sensitivity improvement of a 2 Gb/s quadrature phase shift keyedsubcarrier multiplexed system by use of an optical preamplifier

A traveling wave semiconductor optical amplifier is used as a receiver preamplifier in a quadrature-phase-shift-keyed subcarrier multiplexed system. The intensity-modulated signal from a 1509-m distributed feedback laser bears two 1-Gb/s data signals on a 5-GHz subcarrier. The receiver preamplifier yields a 9.2-dB sensitivity improvement to -29.2 dBm. The system noise sources are measured. Theoretical and measured bit error rates versus received power are presented