Analysis On Structure And Performance Of Q-Modulated DFB Laser

In this paper, we firstly analyzed the necessity of a modulation device with low cost and good high-speed performance in the next generation of optical communication. We discussed the different performance of three kind of modulation device:direct modulated laser (DML), electro-absorption modulated laser (EML) and Mach-Zehnder modulator. DML has a simple structure but its high speed performance is poor; EML can reach a relatively high extinction ratio at high speed and achieve a low chirp, yet it typically has a long modulation section which lead to high RC limitation. Mach-Zehnder modulator also has great high-speed performance. But its disadvantage lies in its high cost and poor ability of integration.Then, three modeling methods used in our model, which are Rate Equation Model. Travelling Matrix Model and Travelling Wave Model, are introduced. Their differences in modeling and Scope of application are also discussed. We highlighted the Travelling Wave Model and further discussed several method of finite difference expression in this model, including FT-BS,BT-BS,BT-FS,Crank-Nicholson and Box scheme expression. Their consistence,stability and accuracy are also discussed.Then, we analyzed the dynamic performance of theory of Q-modulation using Rate Equation Model. We reached a conclusion that Q-modulation theoretically has a good frequency response and low chirp by comparison with DML.Furthermore, a static analysis of Q-modulation laser based on rear reflector is given. We discussed the function of gap filler in the deep drench and threshold condition of the laser.At last, we analyzed the dynamic performance of Q-modulation laser based on rear reflector. Parameters such as phase shift of phase region, effective reflectivity of rear reflector, pump current and length of active region are scanned in our analysis. As a conclusion, we discussed the function of phase region and rear reflector and corrected the condition under which Q-modulation happens. Furthermore, we analyzed the limitation of active region length on optimum extinction ratio.