Self-mixing interference measurement system of a fiber ring laser with ultra-narrow linewidth.

A novel device for self-mixing interference measurement based on the fiber ring laser with ultra-narrow linewidth was investigated for the first time. In order to achieve requirement of our measurement system, a saturable-absorber which consists of a segment un-pumped erbium-doped fiber and a fiber Bragg grating is employed to provide a fine mode selection and guarantee the ultra-narrow linewidth operation. Results demonstrate that the signal-to-noise ratio of the self-mixing interference signal could be enhanced from 18.01 dB to 38.35 dB by inserting a saturable-absorber in the laser cavity. It is in good agreement with the theoretical analysis and proved potential using in self-mixing interference measurement system for high sensitivity and remote measurement.