Simultaneous measurement of refractive index and temperature using a single ultralong-period fiber grating

Novel ultralong-period fiber gratings (ULPFGs) with periods of up to several millimeters are reported here, which are fabricated by the high-frequency CO₂ laser pulses exposure method. The experimental results show that the different resonant peaks of the ULPFG have different temperature and refractive index sensitivities. In addition, it is found that different resonant peaks of the ULPFG have quite different sensitivities to refractive index. Hence, this offers the potential for realizing simultaneous measurement of refractive index and temperature.