Analysis of a multipoint sensor based on two Fabry-Perot cavities employing fiber Bragg gratings

A theoretical analysis of a multipoint sensor conformed by two Fabry-Perot cavities, both constructed with two fiber Bragg gratings (FBG) is presented. Each cavity uses one FGB as reference and the other one as a sensing element. The signals of the sensors were identified through their fundamental beating frequency (FBF), which is the result of the interaction of two consecutive modes inside the cavity and its value depends upon the cavity length. The sensor response was analyzed when there are two or more cavities in the system. In this work there is shown that is possible to determine the magnitude of several variables from each sensor measuring the FBF signal intensity in the frequency domain using FFT algorithm. The general conditions of the system operation are discussed. Some preliminary experimental results about the optimal conditions to be able to distinguish the two sensor signals are presented.