Multimode Suppression and Performance Study of the High-Temperature SFBG Sensor Based on Biconical Fusion Splicing Technology

In order to further suppress higher-order modes of the sapphire fiber Bragg grating (SFBG), thus alleviating the peak-finding difficulty of demodulation and improving the performance of high-temperature SFBG sensor. In this paper, a biconical fusion splicing technique is reported, which makes SFBG have better single-mode field matching with single mode fiber, suppressing a large number of higher-order modes within SFBG. After this process, the SFBG bandwidth can decrease to 0.45 nm and the signal-to-noise ratio (SNR) is improved to 8.29 dB. In addition, SFBG can be subjected to a heating up and cooling up process for 60 hours from 0 °C to 1700 °C in a high-temperature tube furnace, and the reflection peak of SFBG exhibits a stable dynamic shift, and has a maximum sensitivity of 37.1 pm/°C@1400 °C. Finally, SFBG is subjected to high temperature of 1230 °C for 10h and 1515 °C for 10h in a high-temperature tube furnace, which proves the good stability of the proposed SFBG.