Output power stability of GaAlAs laser transmitters using an optical tap for feedback control

Several laser transmitters assembled for 44.736-Mb/sec lightwave field experiments exhibited large, unexpected changes in output power. This problem is now identified with laser front-to-back mirror mistracking and its effect on the back-mirror-monitoring scheme used for feedback control of the laser. To correct this problem, an optical-fiber tap was developed to monitor the actual output power for feedback control. This paper describes the output power stability of five GaAIAs laser transmitters operated using this optical tap for feedback control. Results show that tap-controlled transmitters have output-power stability within +/-2% (+/-0.1 dB) over a 1000-h test period, this being an order of magnitude improvement compared with the earlier scheme of control.