Design Of The Line-width Enhancement Factor Measurement Algorithm Based On Optical Feedback

Because semiconductor laser has many characteristics, such as, concentrated direction and good coherence, an optical feedback self-mixing interferometry (OFSMI) measuring technique used of semiconductor laser as light has been gradually formed. OFSMI measurement technique is a measurement technology mainly using self-mixing interferometry signal including of external reflector moving information and semiconductor laser's parameter information, which has been used in geometric quantities, mechanical quantities and semiconductor laser's parameter measurement, etc.The line-width enhancement factor(LEF) is an important parameter of semiconductor lasers(SLs). On the one hand, LEF characterizes many properties of semiconductor lasers such as spectrum line width, mode stability. On the other hand, it affects OFSMI signal. So the measurement of LEF to the laser application system has theoretical and practical significance.In the paper, LEF of the same semiconductor laser application system was measured,and the measurement results were compared. The main tasks are as follows:The influence of system parameter on OFSMI signal is analyzed based on the OFSMI theoretical model. The Classifications of OFSMI signal under moderate feedback mechanism were studied,According to OFSMI effects, two kinds of LEF measurement algorithms were studied in this paper, which are mapping point measurement algorithm and characteristic point algorithm. Mapping point measurement algorithm is applicable to the moderate and strong optical feedback mechanism, the model of which is complex and difficult to achieve; Characteristic point algorithm is applicable to the mid-moderate optical feedback mechanism, the algorithm is simple and the measurement system is easy to be implemented.A new modeling tool SystemGenerator was introduced. Under the circumstance of Matlab/Simulink, the design of characteristic point measurement algorithm and the algorithm hardware co-simulation module were studied; The soft simulation result of the characteristic point algorithm was compared with the measurement result of hardware co-simulation; The measurement results of the two measurement algorithms were compared.At last, conclusions are drawn from the whole paper and the further research issues are pointed out.