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Abstract-We present an improved theoretical model to analyze dynamics and operation of semiconductor lasers under optical feedback (OFB). The model is applicable for arbitrary strength of OFB ranging from weak to very strong. The model has been applied to investigate the dynamics and operation of lasers over wide ranges of OFB and injection current. An improved set of modified rate equations of lasers operating under OFB were proposed. We introduced a theoretical model to determine the power emitted from both the laser back facet and external reflector. The results showed that the operation of semiconductor lasers is classified into continuous wave, chaotic, and pulsing operations, depending on the operating conditions. The light versus current characteristics were examined in the operating regions of the classified operations. Under strong OFB, we predicted for the first time pulsing operation of lasers at injection currents well above the threshold. We observed the pulsing operation in experiments in good correspondence with the simulated results.

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A theoretical study of the dynamics of semiconductor lasers subjected to pseudorandom digital modulation at gigabit rates is presented. The eye diagram, turn-on jitter ͑TOJ͒, and power fluctuations in the modulated laser wave form are analyzed. The study is based on numerical large-signal analysis of the laser rate equations. Influences of the biasing and modulation currents on the eye diagram and TOJ are examined. The degree of eye opening is measured in terms of a Q factor of the laser signal analogous to the Q factor determining the bit-error rate in transmission systems. Influence of optimizing both the sampling and decision times on the signal Q factor is modeled. We show that the most eye opening corresponds to shortening the sampling time associated with lengthening the decision time. We also assess the relative contributions of the laser intrinsic noise and pseudorandom bit pattern to the TOJ. The results show that the bit pattern is the major contributor to the TOJ when the setting time of the relaxation oscillation is longer than the bit slot.