Chirped-pulsed frequency modulation (C-PFM) for fiber Bragg grating sensors multiplexing

In this paper, we present experimental demonstration of using chirped-pulsed frequency modulation technique (C-PFM) in order to increase the multiplexing capability of a multipoint fiber Bragg grating (FBG) sensor network without increasing the hardware complexity of the acquisition system. This technique, extensively used in radar applications, is based on the amplitude modulation of the emitted signal (pulsed) by a chirped frequency signal and on the use of an adaptive filter for the demodulation of the reflected signals. Here, the same principle has been used to develop a FBG multisensor interrogation system by employing a proper frequency chirped modulation. The optical signals reflected from the FBG sensors are first interrogated by using an in-fiber edge filter and discriminated by a novel adaptive numerical filtering. The potentiality and limitation of such technique are discussed. Preliminary experimental results are presented.