A novel multi-functional fiber grating sensor with self-demodulation and discrimination capabilities

A low-cost but multi-functional fiber grating sensor with self-demodulation and discrimination capabilities is presented. The sensor can measure strain, vibration, normal temperature (-10-100°C), high temperature (100-800°C) and pressure. There are three fiber Bragg gratings (FBGs) and one fiber long period grating (LPG) in the sensor system. The measurands of normal temperature, strain, vibration and pressure, arbitrary two of them can be measured simultaneously, by using FBG1 and FBG2 as sensing head. The LPG is used as a linear response edge filter to convert wavelength into intensity-encoded information for demodulation. On the othre hand, when high temperature (100-800°C) is measured, the LPG will be used as sensing head and FBG1 (or FBG2) will be used as demodulation element. FBG3 is used as reference element to eliminate the errors resulted from light source fluctuation and the cross-sensitivity between measurands and environmental temperature. According to the output of the photodiode (PD), which ...