Temperature dependence of fiber optic Bragg gratings at low temperatures

Cryogenic Temperature Measurement Using Rayleigh Backscattering Spectra Shift by OFDR

“…Consequently, RES is mainly influenced by thermo-optic coefficient ξ . Because ξ is gradually decreasing with the temperature [2], RES is decreasing and nonlinear at cryogenic temperature. As the temperature variation T is measured by detecting RBS shift δν, the minimal measurable temperature variation or the temperature measurement sensitivity T min is depend on minimal measurable optical frequency variation of system or the optical frequency resolution in the system δν min .…”

“…FBGs are often limited by the number of gratings that can be multiplexed in a single fiber. In a worse case, as the low and nonlinear response of FBGs in a cryogenic environment [2], to achieve tiny temperature variation measurement in cryogenic environment, FBGs need to be packaged with special substrates, adhesive and other sensitivities enhancement process, which are complex, expensive and difficult to make them stable [1], [5], [6]. The spectral shift of Rayleigh backscattering can be used to achieve short range (several ten meters) distributed strain or temperature measurements with high sensitivity and high spatial resolution based on optical frequency-domain reflectometry (OFDR).…”

“…aerospace applications) that require a better sensing spatial resolution. FBGs have been extended to the applications of cryogenic temperature measurements [1], [2], [5], [6], which can achieve high temperature sensitivity but they are not distributed measurements, actually, they are only sensing available on the FBG points, not every point on fiber. FBGs are often limited by the number of gratings that can be multiplexed in a single fiber.…”

“…C RYOGENIC temperature measurements are becoming more and more important in many fields, such as the energy industry, transportation, medical technology [1], aerospace [2] and so on. Due to the many advantages of an optical fiber sensor, such as intrinsic electrical isolation, immunity to electromagnetic interference, high sensitivity and accuracy, compactness, and wide bandwidth and multiplexing capabilities [1], it is becoming an attractive means for the measurement of the temperature distribution in harsh environments.…”

Spectra profile expansion of Bragg wavelength on nano-particle embedded fiber-Bragg-grating

“…As we know, by fixing FBG on a substrate with a large thermal expansion coefficient, the sensitivity of temperature FBG sensor can be enhanced to 1.5-15 times that of pure FBG [5,[7][8][9]. But, Reid and Ozcan [10] demonstrated that an FBG embedded in composite material at 4.2-300 K showed the same temperature dependence as that of non-embedded FBG sensors, because the composite materials had small thermal expansion * Corresponding author at: National Key Laboratory for Electronic Materials coefficients. Suresh and Tjin had been developed the embedded FBG with two layers from carbon composite and deformable materials for shear force sensors with a linear variation of the wavelength shift [11].…”