Non-Uniform Sampling Theory applied to Optical Feedback Interferometry for Displacement Sensors

In this paper, a method based on the non-uniform sampling theory is proposed to recover remote target’s displacement from laser optical feedback interferometry (OFI) signals. The laser diode is operated in moderate optical feedback regime and is modulated with a sinusoidal dithering signal via laser diode current drive modulation. This dithering signal allows the recovery of sub-λ/2 displacements. The proposed method relies only on OFI’s fringe detection to recover the target’s displacement. The results are compared with mechanical dithering of the target. Using a laser diode emitting at 1550 nm, the measured white noise power spectral density is approximately$3.4{\text{nm}}/\sqrt {{\text{Hz}}} $.