Hollow core fiber based interferometer for high temperature (1000 °C) measurement

Abstract—A simple, cost effective high temperature sensor (up to 1000 °C) based on a hollow core fiber (HCF) structure is reported. It is configured by fusion splicing a short section of HCF with a length of few millimeters between two standard single mode fibers (SMF-28). Due to multiple beam interference introduced by the cladding of the HCF, periodic transmission dips with high spectral extinction ratio and high quality (Q) factor are excited. However, theoretical analysis shows that minor variations of the HCF cladding diameter may result in a significant decrease in the Q factor. Experimental results demonstrate that the position of periodic transmission dips are independent of the HCF length, but spectral Q factors and transmission power varies with different HCF lengths. A maximum Q factor of 3.3×104 has been demonstrated with large free spectral range of 23 nm and extinction ratio of 26 dB. Furthermore, the structure is proved to be an excellent high temperature sensor with advantages of high sensitivity (up to 33.4 pm/°C), wide working temperature range (from room temperature to 1000°C), high resolution, good stability, repeatability, relatively low strain sensitivity (0.46 pm/με), low cost and a simple and flexible fabrication process that offers a great potential for practical applications. A thorough theoretic analysis of the HCF based fiber structure has been proposed. The experimental results are demonstrated to be well matched with our simulation results.