Performance evaluation of a time-division multiplexed fiber Bragg grating sensor based on heterodyne detection.

Using a technique to observe reflection spectra, the signal-to-noise ratio can be improved for time-division multiplexed interrogation of three fiber Bragg gratings (FBGs) based on heterodyne detection methods. To calculate peak reflection wavelengths of the FBG reflections, absorption lines of are used as wavelength markers, and temperature dependence of the peak wavelength is measured for one FBG. Positioning the FBGs at a distance of 20 km from the control port demonstrates the applicability of this method to a long sensor network.