Temperature sensitivity enhancement in a standard optical fiber with double coatings at low temperature

The thermomechanical behavior of a standard optical fiber with double coating is theoretically analyzed at room temperature and ~ 220 K. As the primary coating becomes stiffer at low temperature, the impact of the thermal expansion of the coatings is no longer negligible and contributes to the thermal response of the fiber sensor. The temperature sensitivity enhancement is validated by distributed fiber sensors based on Brillouin scattering and coherent Rayleigh scattering at 220 K; the experimental results agree well with the theoretical analysis.