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

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 related to relative wavelength shift of the LPG and the corresponding FBG, one can determine the measurand. Experimental results agreed with the theoretical analyses. The demodulation technique is immune to light source fluctuation and the cross-sensitivity between measurand and enviromental temperature, and also the dynamic range is large.