FUNCTIONAL SPECIFICATIONS AND EVALUATION OF COMMERCIALLY AVAILABLE LASER-DIODES FOR OPTICAL SPACE LINKS

Commercially available GaAlAs laser diodes have been tested to predict their behavior in intersatellite communications. Three types of device with various structures have been investigated: Sharp lasers, Hitachi lasers (single longitudinal mode emission in cw operation and Ortel lasers (multi-longitudinal modes). Two modulation schemes were applied to devices (NRZ and 4-PPM), corresponding to the two possible modulation formats selected for ISL experiments. Each laser had an average power output of 30 mW, whatever the modulation mode. The output signal, emission spectrum and beam divergence were measured. A reduction in peak power was found with some devices. Multimode spectra were detected under 4-PPM modulation.