All-Fiber Self-Mixing Interferometer Based on DFB Laser and Phase Modulating Technique

All-fiber self-mixing interferometer (SMI) based on distributed-feedback (DFB) semiconductor lasers and phase modulating technique is introduced to measure the displacement of a vibrational target. Self-mixing interference occurs in a DFB laser by reflecting the light from a mirror-like or a rough target in front of the laser, and the phase is modulated by a fiber electrooptic modulator (EOM) in the external cavity. The sinusoidal phase modulating and demodulating technique is used to analyze the interference signal. The experimental results indicate that the movement of the target can be reconstructed by this method. Combining the optical fiber with self-mixing interference technique, the flexible structure and high-accuracy self-mixing interferometer can be obtained.