Abstract
We report on the use of a multi-core fibre (MCF) comprising strongly-coupled cores for accurate strain sensing. Our MCF is designed to mode match a standard single mode optical fibre. This allows us to fabricate simple MCF interferometers whose interrogation is carried out with light sources, detectors and fibre components readily available from the optical communications tool box. Our MCF interferometers were used for sensing strain. The sensor calibration was carried out in a high-fidelity aerospace test laboratory. In addition, a packaged MCF interferometer was transferred into field trials to validate its performance under deployment conditions, specifically the sensors were installed in a historical iron bridge. Our results suggest that the MCF strain sensors here proposed are likely to reach the readiness level to compete with other mature sensor technologies, hence to find commercial application. An important advantage of our MCF interferometers is their capability to operate at very high temperatures.
Highlights
Optical fibre sensing is a viable technology to monitor strain, an important physical parameter in many application fields
We have reported on strain sensing based on interference of two supermodes in a precisely designed multi-core fibre (MCF) with strongly coupled cores
The interferometers reported here consist of a short segment of MCF, inserted, via standard fusion splicing, between two single mode fibres
Summary
The calibration of our devices was carried out at constant temperature (25 °C) in a fatigue test bench of the Aerospace Technology Centre (Miñano, Spain). The capability of our interferometer to operate in a field environment was investigated For such purpose, we fabricated an interferometer with a 5.4 cm of MCF and packaged it with a rugged strain gage made of 302 stainless steel (model os3155, provided by MicronOptics, Atlanta, USA). In a pilot test we welded our packaged MCF interferometer and the commercial FBG strain sensor at a point located 63 m from the towers in the Getxo side (see Fig. 5b). Note that our device provides essentially the same information than a well-calibrated commercial FBG strain sensor This clearly demonstrates the potential of MCF sensors to work in real-world environments
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