Demodulation System Intensity Coded for Fiber Bragg Grating Sensors

Rodrigo Ricetti, Marianna S. Buschle, Fabiano Kuller, Marcia Muller, José Luí­s Fabris


We report an optical system to be used for the interrogation of fiber Bragg grating based sensors. The demodulation system is intensity coded and its low cost is the main advantage when compared with the traditional wavelength coded systems. Eventual changes in the source intensity are compensated by splitting the interrogating beam in two components and taking the ratio between them. The splitting is accomplished with the combined use of a high-birefringence fiber Bragg grating with two bands centered at 1549.7 and 1550.2 nm and a polarizing cube beamsplitter, besides photo-detectors are used as transducers devices. The system performance was tested by the analysis of a fiber Bragg grating response mounted in a sensing head subjected to a mechanical stress. A linear response of the sensing head was observed, with a sensitivity of 0.36 nm per screw turn that corresponds to a FBG sensitivity of 0.8 pm/ï­ï¥Â a maximum sensitivity of 0.02/ï­ï¥was measured to the applied stress ranging from 225 to 452 ï­ï¥

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