SMALL SIGNAL ANALYSES OF SEMICONDUCTOR LASER DIODES FOR HIGH SPEED OPTICAL FIBER TRANSMISSION SYSTEMS

摘要

This paper concentrates on the small signal analyses of directly intensity modulated semiconductor laser diode which is of great importance in high speed optical fiber transmission systems. A cascade two port circuit model is established to describe the electrical parasitics and intrinsic laser separately. The modulation responses are discussed using this model.With the rapid growth of solid state electronics and optical fiber technologies, optical fiber communication has progressed into gigabit/s digital and microwave analog systems. In the design and analysis of optical fiber transmission system with the bit rate up to Gbit/s or the bandwidth up to GHz using directly intensity modulated laser diode, it is often necessary to determine the dynamic response of the laser for a given electrical input signal. This response is influenced by a number of factors, such as electrooptical resonance, package parasitics, substrate parasitics and space charge capacitance.This paper presents the small signal analyses of the directly intensity modulated semiconductor laser diode for microwave frequency applications. The laser diode small signal circuit model, which is the cascade of package model, chip parasitic model and intrinsic laser diode model, is established. The model parameters are obtained from the measurement of reflection coefficients of laser diode and calculation of laser structure parameters. The circuit model can be easily incorporated in conventional circuit analysis programs, and should find application in the analysis and design of optical and microwave circuits. A significant feature of the circuit model is that it enables the influence of package and substrate parasitics to be evaluated.The small signal frequency response of laser diode is simulated based on the established circuit model. The resulting modulation response has the transfer characteristic of a two order low pass network. A resonance in the response, which will limit the high frequency performance of laser diode, is described. The modified responses by parasities are addressed, and the substrate parasitics have the most significant effect on the roll-off characteristic of the response of the intrinsic laser.The analyses are given for a 1.3μm single mode InGaAsP/InP buried heterostructure semiconductor laser diode.