Temperature-insensitive optical fiber two-dimensional micrometric displacement sensor based on an in-line Mach–Zehnder interferometer

An in-line Mach–Zehnder-interferometer-based two-dimensional (2-D) micrometric displacement sensor was fabricated by inserting a polarization maintaining fiber (PMF) with a length of 1 cm between two conventional single-mode fibers (SMFs). The left end of the PMF was mismatch fusion spliced with an SMF. The right end of the PMF was connected to another SMF without fusion splicing. Two independent interference patterns corresponding to the two orthogonal polarization modes in the PMF were obtained. The visibility of the interference patterns depends on the 2-D micrometric displacement of the SMF along the right end of the PMF on the slow axis and fast axis directions. Experimental results show that the 2-D micrometric displacement sensor with sensitivity of −0.669 dB/μm on the slow axis direction and −0.301 dB/μm on the fast axis direction was obtained. With the use of the intensity demodulation method, the proposed sensor can overcome temperature and displacement cross-sensitivity effects.