9 December 1999 Sensitive element and quasi-distributed fiber optic sensor for bending deformations
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Systems of multiplexed Bragg grating fiber-optic sensors are currently used for the mechanical strain measurements in abutments and bays of bridges, in hulls of buildings, vessels and aircraft. In many cases, however, the control of constructions elements elongation is inadequate for prevention of their mechanical damages, as far as other sorts of deformations (a bending, for example) can be important breaking factor. Hence special fibers sensitive element owning advantages of easy fabrication, absence of moved details, high sensitivity and ability to be combined in one quasi distributed sensor is developed in present work. The suggested sensitive element (SA) presents a place of optical fiber diameter local decreasing which is fabricated by elongation of heated section of fiber. When guided light propagates through this drag mark zone both insitivity of transmitted and backward Rayleigh scattered beams are strongly depends on the fiber curvature in zone of drag mark's neck. The drag mark optimal size and shape providing maximal efficiency and linearity of transformation of bending into intensity of optical signals modulation are defined. In mentioned optimum condition the bending angle sensitivity of SA reaches 2 dB/degree, which exceeds the bending sensitivity of original fiber having no irregularities onto 60 dB. It is demonstrated that by sequential arrangement of drag marks along fiber one can fabricate quasi distributed sensor. Hereby one can use the time domain reflectometry for dividing of signals of seven sensitive elements. Extreme simplicity and high sensitivity of suggested quasi-distributed sensor opens a perspective of its application in systems of monitoring of deformational processes in various objects.
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Yuri N. Kulchin, Yuri N. Kulchin, Oleg B. Vitrik, Oleg B. Vitrik, V. G. Perfilyev, V. G. Perfilyev, } "Sensitive element and quasi-distributed fiber optic sensor for bending deformations", Proc. SPIE 3860, Fiber Optic Sensor Technology and Applications, (9 December 1999); doi: 10.1117/12.372977; https://doi.org/10.1117/12.372977

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