Specific sensor for structural health monitoring

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IDIL Fibres Optiques has collaborated with the French institute of science and technology for transport, development and networks (IFSTTAR) in order to integrate optical fiber sensors into concrete within the framework of civil engineering applications.

Thus, IDIL Fibres Optiques developed a braid shape composite made of fiber glass and epoxy resin with the support of IFSTTAR. The braid shape was designed thanks to the finite elements simulation method. This particular shape enables to ensure a continuous and efficient fixation into concrete. Otherwise, this specific coating which consists of a semi-stiff cable allows a perfect information transfer from the concrete as far as the optical fiber without any change in the deformation field. What is more, coating components were especially studied in order to stand up to concrete attacks.

In fact, those optical fibers were designed to withstand alkaline metal while resins with a special reticulation process were used. Consequently, the manufactured cable is flexible enough to be packaged in strand and to follow the geometry of the structure that must be monitored.

The optical fiber which is situated at the input and the output of our specific sensor is protected thanks to a big diameter stainless jacket. Otherwise, the cable is available in different lengths, from a few centimeters to several tens meters.

The interrogation of such a specific optical sensor can be realized by Optical Time Domain Reflectometry (OTDR) or by Optical Frequency Domain Reflectometry (OFDR). As an example, Brillouin or Raman frequency interval measurements can be done. IDIL Fibres Optiques established a partnership with Omnisenscompany in order to offer complete solutions including sensors and Brillouin interrogators.

Furthermore, the cable can be used in the context of numerous applications dealing with composite health monitoring. As an example, this specific sensor was inserted in the third generation nuclear reactor called “EPR’ (European Pressurized Reactor) which is situated in Flamanville (France).

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Composition Glass fiber; epoxy resin
Optical fiber Single mode 1.5 µm SMF 28 (G 652 standard)
Length 10 cm ≤ L ≤ 50 m
Outer diameter 4 mm (typical)
Connectors FC, LC, SC, SMA, ST, MU, E2000, other
Color Colorless
Metallic jacket diameter 4.6 mm. The length must be specified.
Transfer coefficient (2) 0.94
Thermal expansion coefficient 2.2 10-6 °C
Strength resistance (3) 480 MPa
Elastic elongation (3) 3%
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  • Civil engineering
  • Aerospace engineering
  • Offshore environment
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