Optical code division multiplexing in the design of encoded fiber Bragg grating sensors

Abstract

[EN] The design of spectrally encoded fiber Bragg grating (FBG) sensors is proposed in order to incorporate more information in the optical measurement system. This information can provide full distinction between sensors operating at the same wavelength range. The encoded sensors are inspired by Optical Code Division Multiplexing (OCDM) techniques, specifically, we used Optical Orthogonal Codes (OOC) in order to define the spectral shape of the FBG sensors, providing them with a unique spectral signature. As a result we demonstrated the detection and tracking of the proposed sensors which allows effective measurement of temperature or strain even under overlapping conditions. The interrogation of the proposed encoded sensors could be performed easily and in real time through the autocorrelation product between the reflected spectrum and each sensor codeword. A simple addition to this identification method is implemented in order to remove any error in the interrogation process. Furthermore, a simulation of the proposed sensors under overlapping conditions is performed in order to test the distinction capability of the system. Finally the manufacturing and measurement of the sensors is described.