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Proceedings Paper

A distributed optical fiber sensing system for dynamic strain measurement based on artificial reflector
Author(s): Zhenhong Sun; Yuanyuan Shan; Yanting Li; Yixin Zhang; Xuping Zhang
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Paper Abstract

Phase sensitive optical time domain reflectometry (Φ-OTDR) has been widely used in many applications for its distributed sensing ability on weak disturbance all along the sensing fiber. However, traditional Φ-OTDR cannot make quantitative measurement on the external disturbance due to the randomly distributed position and reflectivity of scatters within the optical fiber. Recently, some methods have been proposed to realize quantitative measurement of dynamic strain. In these literatures, the fiber with or without FBGs in practice was easily damaged and with difficulty of maintenance. PZT is employed to generate strain event in the fiber. There is a large gap compared with the real detecting environment, which will not reveal the full performance of the sensing system. In this paper, a distributed optical fiber sensing (DOFS) system for dynamic strain measurement based on artificial reflector is proposed and demonstrated experimentally. The fiber under test (FUT) is composed by four 20-meter long single mode optical fiber patch cords (OFPCs), which are cascaded with ferrule contactor/physical contact (FC/PC) connectors via fiber flanges. The fiber facet of FC/PC connector forms an artificial reflector. When the interval between the two reflectors is changed, the phase of the interference signal will also be changed. A symmetric 3×3 coupler with table-look-up scheme is introduced to discriminate the phase change through interference intensity. In our experiment, the center 10m section of the second OFPC is attached to the bottom of an aluminum alloy plate. An ordinary loudspeaker box was located on the top of the aluminum alloy plate. The dynamic strain generated by the loudspeaker box is transmitted from the aluminum alloy plate to the OFPC. Experimental results show that the proposed method has a good frequency response characteristic up to 3.2 kHz and a linear intensity response of R2=0.9986 while the optical probe pulse width and repetition rate were 100ns and 10 kHz respectively. Meanwhile, triangle and cosine amplitude-modulated (AM) dynamic strain applied on the fiber are successfully discriminated. The artificial reflectors based on FC/PCs were easily assembled and maintained, and the method of vibration transmission closely resembled the real circumstance than PZT. Therefore, these advantages will extend the potential of this Φ-OTDR technology in structure health monitoring.

Paper Details

Date Published: 31 October 2016
PDF: 8 pages
Proc. SPIE 10019, Optoelectronic Devices and Integration VI, 100190R (31 October 2016); doi: 10.1117/12.2245811
Show Author Affiliations
Zhenhong Sun, Nanjing Univ. (China)
Yuanyuan Shan, Nanjing Univ. (China)
Yanting Li, Nanjing Univ. (China)
Yixin Zhang, Nanjing Univ. (China)
Xuping Zhang, Nanjing Univ. (China)

Published in SPIE Proceedings Vol. 10019:
Optoelectronic Devices and Integration VI
Xuping Zhang; Baojun Li; Changyuan Yu, Editor(s)

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