Fiber optic grating sensors for structural health monitoring at cryogenic temperatures

Abstract

While conventional resistance strain gages show increasing cross-sensitivities to temperature and magnetic field with decreasing temperature down to liquid helium, it has been found that fiber optic Bragg grating strain sensors show negligible thermo-optic and magneto-optic effects in cryogenic environment and allow, therefore, reliable strain measurements. These specific application advantages of optical fiber Bragg grating sensors at low temperatures, together with the electrical isolation and low electro-magnetic interference, low thermal conductivity to a large number of multiplexed sensors, make them attractive for structural health monitoring of super-conductive magnets, e.g., for super-conductive motors, magnetic levitation transport, nuclear fusion reactors, or for measurement of material parameters at low temperature, and, if using special sensor substrates, also for temperature measurements and hot spot detection on superconductors.