Distributed strain sensing using frequency-modulated continuous-wave reflectometric optical technique |
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Authors: | Leong Keey Seah Pei Chin Won |
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Institution: | (1) School of Mechanical and Production Engineering, Nanyang Technological University, Singapore |
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Abstract: | This paper presents an analysis describing the feasibility of a distributed optical fiber strain sensor whose principle of
operation is based on the frequency-modulated continuous-wave (FMCW) reflectometry technique. The system consists of a frequency-swept
laser diode and an unbalanced two-beam interferometer. In this system, the test arm comprises a number of single-mode fibers,
which act as the sensing fibers, with a mirror at the far end and mechanical splices as the connectors, as well as the reflectors.
Theoretical analysis shows that the measuring resolution of the strain is inversely proportional to the length of the sensing
fiber. The strain variation of the sensing fiber is measured by demodulating the phase shift of the beat signal using a heterodyne
signal processing system, and therefore the requirement of a high precision temperature control of the light source can be
eliminated in this way. The comparison between the theoretical and experimental values of the strain resolution showed excellent
agreement. |
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Keywords: | FMCW reflectometry optical fiber distributed strain sensor phase shift demodulation heterodyne signal processing system |
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