Simultaneous Measurement of Curvature and Temperature Based on Mach–Zehnder Interferometer Comprising Core-Offset and Spherical-Shape Structures

Abstract

A novel sensor for simultaneous measurement of curvature and temperature based on the Mach-Zehnder interferometer (MZI) is presented. The sensor consists of slight core-offset and spherical-shape structures. The core offset excites cladding modes, and the spherical shape couples the cladding modes back into the core and interferes with the core mode. Two dips of the interference fringe shift with the variation of curvature or temperature, and simultaneous measurement of curvature and temperature can be realized by means of a sensitivity coefficient matrix. Two MZIs with different lengths are fabricated. For sensor 1 with the length of 20 mm, the curvature sensitivity is as high as -22.227 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the range of 4.66-5.50 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , and the temperature sensitivity is 0.0847 nm/°C in the range of 60 °C-100 °C. For sensor 2 with the length of 16 mm, the curvature sensitivity is -20.128 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the range from 5.66 to 6.53 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , and the temperature sensitivity is 0.0737 nm/°C in the range from 40 °C to 100 °C.