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We present a novel technique for dynamic and simultaneous measurement of displacement and refractive indices at multiple reflection points in optical fibers. This quasi-distributed sensor is based on the incoherent optical frequency domain reflectometry (I-OFDR) technique and allows for m-resolution length change measurement and precise refractive index measurement. We show that the dynamic measurement ability and the simple sensor design allows for new applications in the field of structural health monitoring and chemical process control.
We present a novel technique based on the incoherent optical frequency domain reflectometry (l-OFDR) technique for dynamic (2 kHz) and quasi-distributed length change measurement in polymer optical fibers (POF). The extreme strain sensing capabilities (> 125 %) and cyclic load behaviour of perfluorinated POF are investigated using this technique.
Distributed strain and length change measurement in POF using optical frequency domain reflectometry
(2010)
We show that the incoherent optical frequency domain (l-OFDR) technique provides superior performance compared to standard OTDR techniques in terms of spatial resolution and measurement time. The distributed strain measurement capabilities of perfluorinated POF up 100 % strain are shown and distributed length change measurement using correlation techniques and OFDR are presented.
In this document a new distributed sensor based on Rayleigh scattering in polymer optical fibers (POF) is proposed and first measurement results of the proposed sensor are shown. Different from Silica glas optical fibers POF absorb high quantities of water resulting in a change of their molecular structure and thereby reducing the present small scattering centers in areas of high humidity. The interdependence between scattering intensity and relative humidity is being investigated in case of steady cycles as well as stepwise changes of humidity and in the presence of moisture. A quantitative measure of humidity and scattering is presented.
The potential of the use of POF as distributed sensors in several application fields has been successfully demonstrated. The distributed POF sensors have moved from the laboratory to the field. The paper presents the recent progress in the development of distributed POF sensors and addresses the main challenges to this innovative technology.
We propose focused femtosecond laser irradiation to create stable and permanent scattering damage in large-core polymer optical fibers. Possible sensing applications using optical time domain reflectometry are discussed and presented. Experiments show that quasi-distributed fiber bend sensors and absolute temperature sensors can be realized by evaluating backscatter intensities.
This article reports on recent advancements in the field of distributed optical fiber sensing with a focus on the monitoring of geotechnical structures and buildings. While the classical time-domain approach to distributed sensing is widely known, this article provides an introduction into the frequency-domain analysis technique for both distributed Brillouin measurements (as commonly used for strain and temperature monitoring) and for linear backscattering measurements. The article also addresses an issue which arises when truly distributed measurements are compared among each other; a new approach to calculate differential curves from a measurement and a base-line which avoids misleading large amplitudes at physical events with strong gradients is proposed. Finally, a field test of a new read-out technology, the OFDR (optical frequency domain reflectometry) technique providing dynamic readings of length changes between discrete fiber positions, is presented.
We propose to use focused femtosecond laser pulses to inscribe Scattering damage in the core of polymer optical fibers for interrogation as quasi-distributed sensor points by optical time domain reflectometry.
Fiber bend measurement is demonstrated on off-center inscribed sensor points and absolute temperature measurement is presented by evaluation of the constant backscatter intensities from the inscribed structures relative to temperature-dependent Rayleigh Scattering. Application possibilities and limitations of this new approach are discussed.
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 nε 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.