Short-pulse optical communications experiments

Experiments in short-pulse optical communications have been performed at high data rates (10⁷bit/s) with M-ary modulation formats and, using a subnanosecond internally gated receiver, at very high data rates (2 × 10⁸bit/s) with binary modulation formats to experimentally verify the potential of short-pulse low-duty-cycle direct-detection formats. High resolution TV pictures and error rate data are given for two M-ary formats, pulse interval modulation and pulse position modulation, and error rate data and gated optical receiver characteristics are given for the 200-Mbit/s pulsed gated binary modulation. Results demonstrate the capability of short-pulse laser-communication systems to discriminate against background light and to efficiently convey information. Subnanosecond gating of the receiver was achieved in the 200-Mbit/s experiments. In the M-ary experiments, as many as 12 bit/pulses were transmitted, using 4095 digitally selected 1 -ns time slots. High-quality TV pictures were transmitted at average detected signal to background ratios of less than 0.01.