In order to optimize the self-mixing interference,a theoretical analysis on the self-mixing interference is presented by using a three-mirror cavity model to optimize the self-mixing vibration measurement system.Combining with the experimental results of the self-mixing vibration measurement system,the time domain characteristics of self-mixing signal are obtained corresponding to the external cavity coupling efficient ζ parameter from 0.25×10-4 to 1.75×10-4 and the linewidth enhancement factor ...