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Distributed high-temperature sensing (DHTS) system with single crystal fiber (SCF) has been proved to be an efficient method for ultra-high temperature sensing where traditional silica fiber can't survive. The performance enhancement of the system has been a long desire to better support various applications. In this paper, the upgraded DHTS system used 532 nm laser to avoid thermo-noise at ultra-high temperature and detected the backscattered Raman Stokes and Anti-Stokes signals in a sapphire fiber. The measurands indicated a 7 cm spatial resolution and a 2.2 ℃ temperature resolution with only 30 s average time. The system is expected to be applicable for important applications such as aircraft engine and energy monitoring with further improvements.

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High temperature monitoring is critical to the health and performance of vital pieces of infrastructure such as jet engine, fuel cells, coal gasifiers, and nuclear reactor core. However, it remains a big challenge to realize reliable distributed high temperature sensing system with high speed, high spatial and temperature resolution simultaneously. In this work, a Raman distributed high temperature sensing system with high temperature resolution and high spatial resolution was realized in a single-crystal YAG fiber. The sensing system demonstrated operation from room temperature up to 1400°C with a spatial resolution of 7 cm and response time of 1 millisecond in a 1m long YAG fiber. The average temperature sensitivity of the system is about 7.95 × 10−4/°C. To the best of our knowledge, this is the best spatial resolution and response time reported in literature. In this system, a 2D image restoration was used to boost the signal to noise ratio of sensor. Empowered by the algorithm, the average temperature standard deviation along the sensing fiber of 7.89 °C was obtained based on a single frame data in 1 millisecond. A new record of temperature resolution of 0.62 °C was demonstrated in only 1 second frame data traces, which enables a fast response capacity.

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