Use of the time windowing on the chirped-pulsed frequency modulation (C-PFM) technique to improve the multiplexing performance of a fiber optic Bragg sensor array

In this paper, we present a novel approach to increase the multiplexing capability of a multipoint fiber Bragg grating (FBG) sensor network. Our approach is based on the possibility of exploiting the chirped-pulsed frequency modulation technique (C-PFM) to the optical pulses used to read a FBG sensor network. This technique, extensively used in radar applications, in the case of optical sensors is based on the amplitude modulation of the emitted signal (pulsed) by a chirped frequency signal and on the demodulation of the reflected signal by means of adaptive filter. The main parameters for a multiplexing systems are the minimum distance between two adjacent sensors and the cross-talk achievable. We show that the use of a well designed time shaping windowing of the transmitted pulse can improve both such parameters.