High sensitivity long-period grating-based temperature monitoring using a wide wavelength range to 2.2 μm

Temperature effects on the various cladding modes of a long-period grating (LPG) fabricated in B-Ge co-doped fibre have been investigated to create a high sensitivity measurement device. The temperature sensitivities of the attenuation bands of the LPG over the wavelength region 1.2–2.2 μm, for a grating with a 330 μm period, were obtained by monitoring the wavelength shift of each attenuation band, with a temperature increment of 20 °C, over the range from 23 °C to 140 °C. The attenuation band appearing over the 1.8–2.0 μm wavelength range has shown a nearly five times higher temperature sensitivity than that of lower order modes, and thus it shows significant promise for fibre optic temperature sensor applications.