Abstract
A restoration method for reflection spectra in a serial FBG sensor array with spectral shadowing is proposed and experimentally demonstrated in a WDM/TDM combined multiplexing system. The SNR of each FBG sensor is formulated and analyzed as a function of the number and reflectivities of serial FBG sensors. The maximum number of FBG sensors in a single fiber line can be determined by the approximate formula. In the test using two FBG sensors, the restored reflection spectrum of second FBG sensor is shown to be very well matched with the original reflection spectrum. Using the proposed restoration method, the maximum peak detection error in a strain experiment is suppressed drastically by almost seven-fold, from 0.074 nm to 0.011 nm.
Highlights
Fiber Bragg gratings (FBGs) have many advantages like immunity to electromagnetic interference, integration into composite materials without degradation of the strength of the host material, capacity for multiplexing many sensors in a single fiber lead, and capacity for mass production with goodSensors 2012, 12 repeatability, making them potentially competitive against conventional electrical strain sensors.Many researchers have studied the use of FBG sensors to measure various parameters, such as strain [1,2,3], acceleration [4,5], temperature [6], humidity [7], etc
With their wavelength-encoded nature and the capacity for wavelength division multiplexing (WDM), FBGs have been demonstrated for a number of sensing applications, especially for strain measurements for monitoring structural health status in smart structures [8]
In the WDM technique, it is important to detect the accurate Bragg wavelengths of the FBGs within the sensor network because the Bragg wavelengths are directly related with the measuring parameters such as strain or temperature
Summary
Fiber Bragg gratings (FBGs) have many advantages like immunity to electromagnetic interference, integration into composite materials without degradation of the strength of the host material, capacity for multiplexing many sensors in a single fiber lead, and capacity for mass production with good. Maximizing the number of sensors is very important for large-scale structural health monitoring which requires a huge number of sensor heads Because these hybrid techniques basically restore the spectra of FBGs, these techniques don’t use numerical techniques for the accurate Bragg wavelength detection except for noise rejection schemes such as noise filtering, curve fitting, etc. The WDM/TDM hybrid approach has been demonstrated using a 3 × 3 grating array with time-gating at the detector combined with wavelength detection using the scanning Fabry Perot (FP) filter [13]. This scheme has two problems: multiple-reflection [14] and spectral-shadowing [8]. We will propose and experimentally demonstrate a new spectrum restoration method that reduces the peak detection error due to the shadowing effect in WDM/TDM serial sensor arrays
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