Sensitivity Modal Analysis of Long Reflective Multimode Interferometer for Small Angle Detection and Temperature

Abstract

This work presents the sensitive modal analysis of a long reflective multimode optical fiber device for angle and temperature. The reflective multimode interference optical fiber device was fabricated by splicing ~40 cm of multimode optical fiber (50/125). This structure provides a random interference reflection spectrum; the wavelength sensitivity analysis indicates that estimating the angle detection is impossible due to the several modes involved. However, by the phase analysis of the Fourier components, it was possible to detect slight angle deflection. Here, three spectral Fourier components were analyzed, and the maximal sensitivity achieved was 1.52 rad/°; the maximal angle variation of the multimode fiber was 3.4°. In addition, the thermal analysis indicates minimal temperature affectation (0.0065 rad/°C). Moreover, it was demonstrated that there is a strong dependence between the sensitivity and the m-order of the modes involved. Considering the fiber optic sensor dimensions and signal analysis, this device is attractive for numerous applications where slight angle detection is needed.