A Temperature and Strain Dual-Parameter Sensor Based on Conical Four-Core Fiber Combined With a Multimode Fiber

A temperature and strain dual-parameter sensor based on conical four-core fiber (FCF) combined with multimode fiber (MMF) is presented. A sensor based on Mach–Zehnder interferometry is prepared by using single-mode fiber (SMF)–MMF–FCF–SMF and tapering at the fusion point between FCF and SMF. When the temperature and strain change, the length and refractive index of the fiber change due to thermal and elastic effects. Based on the corresponding function relationship and coefficient matrix method, the temperature and strain dual-parameter matrix equation of the sensor can be obtained. The results show that the red shift of the transmission spectrum occurs with the increase of temperature in the range of 40 °C–90 °C, and the maximum temperature sensitivity is 85.45 pm/°C. At the strain range of 0–<inline-formula> <tex-math notation="LaTeX">$800~\mu \varepsilon $ </tex-math></inline-formula>, the blue shift occurs in the transmission spectrum with the increase of the strain, and the maximum strain sensitivity is −6.76 pm/<inline-formula> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula>. Finally, the matrix equation of the dual-parameter sensor is obtained based on the experimental results. The sensor is simple to make and has high sensitivity. It can measure the temperature and strain parameters in the environment of the micro-magnetic field and micro-electric field.