MilliKelvin resolution in cryogenic temperature distributed fibre sensing based on coherent Rayleigh scattering

The response of a distributed temperature sensor based on coherent Rayleigh scattering is experimentally studied in the temperature range from 77 K up to 300 K, using fibres with standard and ORMOCER coating. A precise and absolute frequency scan is performed to obtain the best temperature resolution that turns out to be in the mK range. Experimental results point out that heating and cooling processes, at cryogenic temperatures, exhibit different temperature sensitivities when standard single-mode fibres are used; however, specially coated fibres exhibit better repeatability.