The study of temperature measurement based on the transmission of fixed wavelengths for helical long-period grating

This research involves a fixed wavelength and dual-wavelength ratio temperature measurement for helical long-period grating. There are two resonant dips near 1475 and 1520 nm, with the pitch length 782 μm. The temperature sensitivity of resonance wavelengths is about 0.06 nm/°C. Both theoretical simulation and experiment results show that the transmission of a fixed wavelength linearly changes with the temperature. It has a high application value for measuring temperature. Besides, the dual-wavelength ratio is studied to eliminate the influence of light source. The temperature sensitivity of transmission intensity ratio of I1469.6nm/I0 and I1469.6nm/I1526.5nm are about 1.0076/°C and 0.0155/°C, respectively, so the dual-wavelength ratio is more practical. And the 0.0155 times intensity change could be much more easily measured than the 0.06 nm wavelength change for each degree Celsius. So the dual-wavelength ratio of the helical long-period gratings is very suitable for temperature sensors.