This paper presents a novel fiber optic ultrasonic sensing system to measure high temperature in the air. Traveling velocity of sound in a medium is proportional to medium’s temperature. The fiber optic ultrasonic sensing system was applied to measure the change of sound velocity. A fiber optic ultrasonic generator and a Fabry-Perot fiber sensor were used as the signal generator and receiver, respectively. A carbon black- Polydimethylsiloxane (PDMS) material was utilized as the photoacoustic material for the fiber optic ultrasonic generator. A water cooling system was applied to cool down the photoacoustic material. A test was performed at lab furnace environment (up to 700 ℃). The sensing system survived 700℃. It successfully detect the ultrasonic signal and got the temperature measurements. The test results agreed with the reference sensor data. The paper validated the high temperature measurement capability of the novel fiber optic ultrasonic sensing system. The fiber optic ultrasonic sensing system could have broad applications. One example is that it could serve as acoustic pyrometers for 3D temperature distribution reconstruction in an industrial combustion facility

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Jingcheng Zhou, Xu Guo, Cong Du, Nan Wu, Tong Ma, Yuqian Liu, Chengyu Cao, and Xingwei Wang, "High temperature monitoring using a novel fiber optic ultrasonic sensing system," Proc. SPIE 10639, Micro- and Nanotechnology Sensors, Systems, and Applications X, 1063910 (Presented at SPIE Defense + Security: April 16, 2018; Published: 8 May 2018); https://doi.org/10.1117/12.2305631.