Packaged Multi-Core Fiber Interferometer for High-Temperature Sensing

A small size and compactly packaged optical sensor for high-temperature measurements is reported. The sensor consists of a short piece of multi-core fiber (MCF) spliced to the distal end of a single-mode fiber. The packaging consists of an inner ceramic shield that prevents bending, curvature, and vibration effects on the MCF, and an outer metallic shield that protects the device against impacts. The interaction between specific supermodes excited in the MCF creates an interference pattern that shifts linearly with the temperature. The sensor was calibrated in the range from 200 to 1000 °C and a K-type thermocouple was used as a reference. The average temperature sensitivity was found to be 24.8 pm/°C with a response time of 15 s. Our results indicate that our MCF interferometric thermometer is as accurate as an electronic one with the advantage that it is passive. Therefore, we believe that the proposed sensor is suitable for industrial applications.