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Distributed strain and temperature change detection using optical frequency domain reflectometry
(2017)
We propose the optical frequency Domain reflectometry (OFDR) technique based on intensity modulation frequency sweep measurement for coherent distributed sensing applications. By evaluating interferometric Rayleigh scattering changes along the fibre, strain and temperature changes can be detected with a sensitivity in the ne-range and 10 mK temperature resolution. Low Vibration frequencies and vibrations up to the kHz-range can be detected by differential power change evaluation in the spatial domain. This OFDR approach is a low-cost alternative to distributed vibration sensing based on C-OTDR up to distances of several kilometres.
We introduce the optical frequency domain reflectometry (OFDR) technique based on intensity modulation frequency sweep measurement for distributed disturbance measurement in optical fibres. By evaluating interferometric Rayleigh scattering changes along the fibre, strain and temperature changes are detected with 100 n(epsilon) sensitivity and 10 mK resolution. The vibration frequencies for low frequencies and up to the kHz-range can be obtained from power change evaluation in the spatial domain. This novel OFDR approach is a low-cost alternative for distributed disturbance measurement up to distances of several kilometres.
A dynamic and quasi-distributed sensor principle for simultaneous measurement of length changes and optical power changes between reflection points in an optical fiber is presented. The technique is based on the incoherent optical frequency domain reflectometry (I-OFDR). The calculation of phase and amplitude changes from few measurement points in the frequency domain yields precise and dynamic length and optical power change results up to 2 kHz and μm-resolution. Test results showing the deformation of a masonry building under seismic load are presented. Promising fields of application for this technique are the structural health monitoring sector and chemical process control.