Optimization of Mach-Zehnder interferometer with cascaded up-tapers and application for curvature sensing

Experimental results show that a high curvature sensitivity of −35.41 nm/m−1 is obtained in the range of 0.6846 m−1- 1.0606 m−1, which is 2.4 times higher than that of the interferometer with single-mode-multimode-single-mode (SMS) structure. The two up-tapers, featured by great mechanical strength, are fabricated by only fusion pushing together a whole SMF without cleaving procedure, contributing to excellent repeatability and consistency in the sensor fabrication process. Such an all-fiber sensor exhibits advantages of simple configuration, ease of fabrication, excellent mechanical strength, low cost, and high curvature sensitivity.