FOUR WAVE MIXING IN DISTRIBUTED FEEDBACK SEMICONDUCTOR LASERS FOR COHERENT OPTICAL COMMUNICATION

摘要

Distributed feedback (DFB) lasers are particularly attractive in four wave mixing (FWM) since they oscillate in single mode which can act as a pump in FWM. In this configuration the probe signal slightly detuned with respect to the oscillating mode (pump) gives rise to a conjugate signal. The amplification of the probe and the conjugate waves in lasers above threshold is symmetric with respect to the zero probe. Pump detuning and effective detuning FWM bandwidth is mainly dependent on the relaxation oscillation frequency of the pump laser. The effective FWM bandwidth is only determined by the carrier's spontaneous lifetime. Injection locking properties of the DFB lasers give rise to a symmetric stable locking band which allows a relative phase detuning approaching π radians. This opens the possibility to use the injection locked DFB semiconductor lasers for optical coherent phase shift keying (PSK) modulation. This provides for multi-gigabit optical communication links using semiconductor lasers for application in Wide Area Networks (WANs).