Highly Sensitive Strain and Temperature Sensors Based on Vernier Effect in Cascaded Mach-Zehnder Interferometer and Sagnac Interferometer

In this article, vernier effect (VE), which is an effective method to enhance the measurement sensitivity of strain and temperature, was experimentally studied through cascading a Mach-Zehnder interferometer (MZI) with a Sagnac interferometer (SI). The MZI consisted of a tapered single-mode fiber (SMF), while the SI was formed using a panda-shaped polarization-maintained fiber (PMF). Free spectral ranges (FSRs) of the two interferometers were slightly different from each other, and as a result, the VE was successfully excited. The experimental results demonstrated that the measurement sensitivity of strain was improved from 26.7 to −110.92 pm/ \mu \varepsilon at the temperature of 24~^{\circ } C, while the measurement sensitivity of temperature was improved from −2978 to 7934 pm/°C at the strain of 0~\varepsilon . The sensitivity was amplified about four times. The cross-sensitivity of temperature and strain measurements is 71.53~\mu \varepsilon /°C. The proposed sensor exhibits in advantages of simple in construction, high sensitivity, and multiparameter measurements making it a superior contender for strain and temperature monitoring in engineering.