Twin-grating fiber optic sensor demodulation

• Published in: Optics communications 2001-05, Vol.191 (3), p.253-262
• Main Authors: Miridonov, S.V., Shlyagin, M.G., Tentori, D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bragg gratings; Circuit properties; Computers in experimental physics; Data analysis: algorithms and implementation; data management; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fiber optic sensor; Fundamental areas of phenomenology (including applications); Gratings; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Integrated optics. Optical fibers and wave guides; Interferometric sensors; Optical and optoelectronic circuits; Optical elements, devices, and systems; Optics; Physics; Sensor demodulation; Sensors, gyros; Signal processing; Thermal instruments, apparatus and techniques; Thermometry
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/S0030-4018(01)01160-9

We present a demodulation algorithm for sensors consisting of two Bragg gratings separated by a short distance. This sensor works as an unbalanced interferometer sensitive to temperature or axial strain variations. The sensor demodulation procedure here presented is based on the evaluation of the phase of the interference pattern produced by light reflected from both gratings and on the determination of the Bragg wavelength shift. This information can be extracted from the phase distribution of the optical spectrum image in the Fourier domain. The demodulation method here presented has been thoroughly analyzed theoretically and tested experimentally. Experimental tests were performed with temperature sensors. The proposed demodulation procedure provides high accuracy and absolute measurements.