Impact of 1.5 mu m quantum well lasers on intensity noise in analogue communication systems

Then the increasing interest in analogue optical communications, semiconductor laser diode parameters such as linearity, modulation bandwidth and noise need to be optimised. In all these aspects, quantum well lasers are potentially better than bulk devices, due to their higher intrinsic resonance frequencies for a given optical power. This paper is concerned specifically with laser intensity noise and how it may be reduced through the use of quantum wells. Ideally the laser intensity noise level should be less than the combined thermal and shot noise in the receiver. Measurements, taken from D.C. to 12 GHz, show that relative intensity noise (RIN) below a frequency of 2 GHz in 1.5 mu m quantum wells is 10 dB lower than in conventional (bulk) lasers, being less than -150 dB/Hz at output powers of only 1.8 mW/facet. hence, the signal to noise ratio in quantum wells is improved making them attractive candidates for future analogue microwave systems.