22 April 2006 High-sensitivity cryogenic temperature sensors using pressurized fiber Bragg gratings
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Cryogenic temperature sensing was studied using a pressurized fiber Bragg grating (PFBG). The PFBG was obtained by simply applying a small diametric load to a regular fiber Bragg grating (FBG), which was coated with polyimide of a thickness of 11 micrometers. The Bragg wavelength of the PFBG was measured at temperatures from 295 K to 4.2 K. A pressure-induced transition occurred at 200 K during the cooling cycle. As a result, the temperature sensitivity of the PFBG was found to be nonlinear and reach 24 pm/K below 200 K, more than three times the regular FBG. For the temperature change from 80 K to 10 K, the PFBG has a total Bragg wavelength shift of about 470 pm, 10 times more than the regular FBG. From room temperature to liquid helium temperature the PFBG gives a total wavelength shift of 3.78 nm, compared to the FBG of 1.51 nm. The effect of the coating thickness on the temperature sensitivity of the gratings is also discussed.
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Meng-Chou Wu, Meng-Chou Wu, Stanton L. DeHaven, Stanton L. DeHaven, } "High-sensitivity cryogenic temperature sensors using pressurized fiber Bragg gratings", Proc. SPIE 6189, Optical Sensing II, 61890O (22 April 2006); doi: 10.1117/12.673851; https://doi.org/10.1117/12.673851

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