Optical Feedback Self-mixing Interference System Parameter Measurement

Optical feedback self-mixing interference(OFSMI) is a precise measuring technique,with the feature of simple, compact, and self-aligning. Based on the characteristic of high sensitiveness, high accuracy and un-touchment operation, the technology has been widly studied and applied in many fields,with its mainly application in geometry sensing parameters measurement and semiconductor laser parameters measurement.The linewidth enhancement factor(LEF), also known asα-factor, has a great importance for semiconductor lasers(SLs). And it characterizes several aspects of SLs, such as the linewidth, the lineshape, the mode stability, the injection-locking range, and so on.Theα-factor is measured by OFSMI technology in this paper. The moderate optical feedback self-mixing system is studied when the external cavity of semiconductor laser suffers a harmonic vibration. The following tasks are accomplished.Firstly, the mode of OFSMI measurement system is studied in detail. Subsequently, the characteristic of OFSMI signal is studied at moderate feedback regime. The basic measuring theory of the semiconductor laser parameters based on OFSMI technique is illustrated at moderate feedback regime.Secondly, the de-nosing problem and the normalization processing problem of the OFSMI signal are studied, according to the specific requirement for the signal at moderate optical feedback level.Finally, an optimized measurement rule is given at moderate optical feedback regime. Based on the rule, an automatic measurement algorithm is developed used for measuring LEF. The feasibility and accuracy of the automatic measurement approach has been verified through simulation and experimentation. The simulation results show the algorithm is precise in measurement. The relative error ofαis less than 4.96%. In addition, the coherence and accuracy is proved by measured datum. The results show the relative standard deviation ofαis about 3.26%.