Optical fiber temperature sensor using a pair of nonidentical long-period fiber gratings for intensity-based sensing

We propose and demonstrate a new technique for intensity-based fiber temperature sensing based on long-period fiber grating pairs having different temperature coefficients and an absorptive core mode blocker placed between the two gratings. The constructed fiber sensor exhibits a bandpass filter response that varies with the temperature. A light-emitting diode is used as the input light source to convert the wavelength shift into an optical intensity change. A photodetector is used to measure the output intensity as a temperature-encoded signal.