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This paper describes an optical‐frequency pulse‐position‐modulation experiment using a GaAs luminescent diode as the source and either a pin or an avalanche photodiode as the detector. The experimental system transmits an audio band from 300 Hz to 3.4 kHz at an 8‐kb/s repetition rate. Timing synchronization between the transmitter and receiver has been accomplished by two methods: by transmitting a separate clock signal and by recovering the timing from the ppm signal itself. Data show, with each scheme, peak‐signal‐to‐rms‐noise ratios of 70 dB can be achieved with the required average optical power at the receiver being −73 dBm with a pin detector and −88 dBm with an avalanche detector.