Simulation studies of nearly single-mode semiconductor lasers

• Main Authors: Li,Chien-Cherng, 李建成
• Other Authors: Chang,Hung-Chiun
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/37478910936401740466

碩士 === 國立臺灣大學 === 光電(科學)研究所 === 82 === A numerical model of semiconductor lasers is developed in this report. It is used to study important characteristics for the applications in optical transmission systems. Monte Carlo time- domain simulations are employed to evaluate the noise behaviors in the model. Mode partition noise (MPN) and timing jitter, which are strongly related to the noise behaviors, are discussed in the case of high-speed pulse modulation. The effects of external reflection on semiconductor lasers have also been included by adding the time-delayed terms to the model. When the laser diode is modulated with the pattern of pesudorandom words in the multi- gigabit-per-second range, the MPN is enhanced and the dependence on the bias level is weaker. The MPN can be effectively reduced by increasing the mode discrimination of laser diodes. Timing jitter is also increased due to the pattern effect. It can be minimized with an appropriate choice of the bias level at which the pattern effect is absent. The feedback-induced noise can enhance the MPN and timing jitter. The level of feedback should be sufficiently suppressed to avoid large power penalty or bit- error-rate (BER) in an optical transmission system. The and noise behaviors of laser diodes can be closely related to the modal characteristics. We analyze the mode behaviors of distri- buted feedback (DFB) lasers at and above threshold by using the effective-index matrix method. The effect of the axial carrier- density nonuniformity, i.e., the longitudinal spatial burning of .lambda./4-shifted DFB lasers operated above threshold can change the mode discrimination. It can result in the instability of dynamic single-mode operation in the strongly coupled case.