A novel demodulation technique for identical weak fiber Bragg grating array sensing with improved performance

A novel demodulation method for the sensing system based on an identical weak fiber Bragg grating (IWFBG) array is proposed in this paper. With the help of a wavelength-swept laser, the reflection spectrum and transmission spectrum of an FBG can be mapped into two pulse signals with opposite polarity in time domain, both of which contain the wavelength information of the FBG. Therefore, improved signal intensity and sensing performance can be obtained when the reflection and transmission spectra of the FBG are both adopted for demodulation. A simulation has been done to a quasi-distributed sensing system based on the IWFBG array. The results show that the improvement of the signal intensity is related to the number of the FBGs with the same center Bragg wavelength. The location of the event is realized through the intensity comparison of the pulse signals, and the wavelength change of the FBG can be directly obtained by monitoring the time delay difference between the reference pulse and the sensing pulse.