The temperature and strain response of fibre Bragg grating sensors in a cryogenic environment has been evaluated. The fibre Bragg grating temperature response was found to be nonlinear, decreasing to approximately zero for temperatures less than 100 K. The response to strain was found to be temperature independent.

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The thermal response of the attenuation bands of an optical fibre long period grating was monitored over a temperature range 4.2K to 280K. A linear dependence of the central wavelength of the band, of gradient 0.2 nm/K was observed over the range 77K to 280K. A measurable wavelength shift was observed at temperatures as low as 20K.

The commissioning of superconducting magnet coils was monitored using embedded optical fibre Bragg grating sensors (FBG) fabricated in highly linearly birefringent (HiBi) fibre. The HiBi FBG sensors monitored the internal strain developed in the coils during the energisation of the coils. The development of multiple components of strain in the coils when the magnet was energised and quenched was monitored, revealing phenomena that it had not been previously possible to measure using other sensor technologies.

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