Laser transmitters for 70-MHz entrance links

Lightwave transmitters providing an amplitude-modulated light output from injection lasers have been designed and tested. Six transmitters were assembled using GaAlAs double-heterostructure lasers and displaying (i) third-order intermodulation products >26 dB below the fundamental at 80-percent modulation index and 0.6 to 0.8 m W average optical output, (ii) excess noise ratios <1.5 dB; and (iii) frequency response within ±0.6 dB from 0.1 to 100 MHz. These transmitters were burned-in at room temperature for 300 h and used with entrance links in a satellite experiment.