HIGH-SENSITIVITY SEMICONDUCTOR OPTICALLY PREAMPLIFIED Q-PPM RECEIVER

An optically preamplified receiver for 980-nm laser intersatellite com munications Is reported. A record sensitivity of 330 photons/bit for a semiconductor optically preamplified receiver is obtained at 50 Mb/s with quaternary pulse-position-modulation (Q-PPM). The experimental re sults are shown to be in excellent agreement with a novel exact calcul ation of the optically preamplified receiver Q-PPM bit-error rate (BER ). Calculated performance based on these results shows that with an im proved optical transmitter the receiver attains 1.5 dB higher sensitiv ity than previously achieved at this wavelength.