Research on Polarization and Phase Fading Compensation in Michelson Interferometer Based on 3 × 3 Coupler and Novel Probe with Built-in Faraday Rotator

Abstract

A self-designed probe and a feedback control scheme based on the Michelson interferometer with a 3 × 3 fiber coupler are proposed. A 45° Faraday rotator is built into the self-designed probe, and a feedback control scheme is used to judge the direction of increase or decrease for the phase compensation, so as to solve the problems of polarization and phase fading. In addition, a result-normalized method is applied in a micro-vibration measurement experiment. The experimental interferometer system achieves a high frequency of 1 MHz micro-vibration. The normalized results keep stable with a maximum deviation from the mean of 1.9% when the power of light reflected back into the self-designed probe is altered. Applied research is carried out by detecting the displacement due to a photoacoustic wave. Therefore, the experimental interferometer system is available for the practical application of micro-displacement measurements, noncontact high-frequency detection, and point-by-point image scanning in biological tissue.

Analysis and Design of Fiber Microprobe Displacement Sensors Including Collimated Type and Convergent Type for Ultra-Precision Displacement Measurement

“…This makes it difficult to simulate the transmission path of the Gaussian beam. As shown in Figure 5, the symmetric equivalent fiber receiving probe is established with the reflector as the axis following a method borrowed from the literature [18]. The beam interference can be equated to the signal light coupling from the original probe and the intrinsic reference light from the equivalent probe at the end-face of the equivalent probe.…”

“…Some researchers processed the fiber structure to achieve a tapered core structure in order to reduce the outflow light beam dispersion angle, increase the fiber optic microprobe detection distance, and ultimately achieve an 80 mm working distance [14]. In order to further increase the micro-sensing probes' measurement distance, a method was proposed to match the single-mode optical fiber parameters using convex and variable refractive index lenses, which ultimately resulted in better beam collimation and increased the detection distance to 30-40 cm [15][16][17][18]. However, the above structure approximates the multi-beam interference into a two-beam interference, an approximation that is acceptable in some sensing fields where high precision is not required.…”