Application Of H_∞ Robust Control In Improving The Response Characteristic Of Dfb Semiconductor Lasers

Distributed Feedback Laser Diodes (DFB-LD) relatively are inexpensive and have good frequency response and direct modulation characteristics, so DFB-LD become an irreplaceable source in the optical fiber communications and CATV. Although the DFB-LD shows the relatively good frequency response characteristics, the presence of relaxation oscillation peak limits the wide application of DFB-LD. In this paper, we have designed laser control system with robust control theory and the control system can improve the lasers in the time domain and frequency domain responses.Firstly, this paper describes the significance meaning of improving DFB-LD and introduces the research status and the development trend. We put forward some problems in the current research and establish the starting point of this study.Secondly the structural characteristic of DFB-LD is introduced by a brief. We analyse the rate equation and establish the SIMULINK model of rate equations. These are considered as a basis for the simulation. This paper descripts the problem of DFB-LD intensity modulation and establishs the transfer function model. The necessity and rationality of the DFB-LD robust control theory are described in the base of establishment of a good model. We choose the appropriate robust control model in the base of the DFB-LD analysis of the design requirements and focuse on the selection of weighting function studied and analyzed.Because the choosing of weighted function has the contradictory options in the problem of mixed sensitivity, the genetic algorithm has an efficient way in multi-objective optimization problem, and it is also able to find a best solution. Therefore the paper describes the genetic algorithm optimization mechanism, analyzes the requirements and targets of the DFB-LD controller, and optimizes the weighting function by the use of genetic algorithm. This can make the performance of the robust controller better.Finally, we simulate the laser control system by MATLAB and analysis and comparison the response and time domain frequency response curve with and without control in the standard model and the model parameters and under disturbance occurred. The simulation results show that the designed laser control system can improve response characteristics of DFB-LD and also improve the laser system Robust Stability.