Temperature dependence of the stress response of fibre Bragg gratings

Fibre Bragg gratings, used as stress sensing elements, show a temperature dependence of their stress response, which is mainly characterized by Young's modulus of the fibre material. The temperature dependence of the stress response of a fibre Bragg grating over a range from −38 °C to +110 °C has been measured. The stress sensitivity decreases linearly by 1.22 × 10−4 K−1 over this range which is nearly identical to the increase of Young's modulus of fused silica over this range implying that it is predominantly Young's modulus which defines and characterizes this thermal dependence. Significantly, bare and re-coated fibres show a markedly different behaviour below 0 °C due to the glass transition temperature of the jacket material.