Design and Temperature Sensing Performance of a Modal Interference Sensor with the Core Mismatch-Offset Structure

We design high-sensitive fiber-optic sensor based on modal interference for temperature measurements. The core mismatch-offset sensor is fabricated by splicing a section of multimode fiber (MMF) between two single-mode fiber (SMF) and offset splicing of SMF. We use the finite-difference beam propagation method to numerically analyze the mode and intensity distributions of the light field in the sensor. We optimize the structure parameters such as the length of MMF, the length of sensing SMF, and the offset of sensor; the optimum parameters of proposed sensor are 4.0 mm, 1.73 cm, and 3.5 μm, respectively. Experimental results show that the proposed sensor is successfully used to monitor the variation of ambient temperature, and it possesses a high temperature sensitivity of 167.2 pm/°C with good linearity. The core mismatch-offset sensor with high sensitivity and compact structure provides a new method for designing fiber-optic sensor and temperature sensing.