Phase modulated self-mixing interferometer of a fiber laser system

• We model a novel structure for self-mixing interferometer based on a fiber laser.
• Error sources induced by nonlinearity and distortion of the signal are evaluated.
• The system achieves high measurement accuracy.
• The system provides a solution for displacement measurement on fiber sensing.

In this paper, self-mixing interference measurement based on phase modulation is demonstrated using a fiber laser system. The measurement setup is built by an erbium-doped fiber laser and an integrated-optic phase modulator. Optical feedback and phase modulated interference is theoretically analyzed, and the phase demodulation algorithm of the interference signal is implemented by Fourier analysis. Error sources induced by the distortion of the interference signal in the presence of optical feedback and the imperfect alignment between the polarization of the light and the electro-optically active axis are evaluated in detail. The system is experimentally applied to reconstruct the motion of a high-precision commercial PZT and a displacement measurement accuracy of λ/20 is obtained, providing a practically feasible solution for displacement measurement based on all optical-fiber sensing applications with high precision.