Strain-independent high-temperature sensor with a suspended-core fiber based Mach–Zehnder interferometer

• A compact and low-cost fiber-optic high-temperature sensor is proposed.
• The device is based on Mach–Zehnder interferometer with a suspended-core fiber.
• The sensor head can avoid strain crosstalk in temperature measurement.
• High-temperature sensing up to 1000 °C is realized with high sensitivity of 53.87 pm/°C.

A simple Mach–Zehnder interferometer (MZI) was presented for high temperature measurement. The device was composed of a short segment of suspended-core fiber (SCF) sandwiched between two standard single mode fibers (SMFs) with a misaligned splicing joint. Lower temperature measurements were firstly carried out from room temperature to 190 °C, and the obtained sensitivity at the wavelength of 1465 nm was 25.82 pm/°C. However, a nonlinear response was further achieved for high-temperature sensing up to 1000 °C. Between 20 and 200 °C, the sensitivity was just 24.24 pm/°C at the wavelength of 1457 nm, whereas a higher sensitivity of 53.87 pm/°C was acquired in the range of 200–1000 °C. In addition, the strain cross-sensitivity was extremely low. As a result, the device can be developed as a strain-independent temperature sensor and become an excellent candidate for high temperature measurement.