High performance Fiber Bragg Grating systems for Smart Structures: Application to Overhead Contact Line monitoring in the railway industry
Résumé
Enhancing train transportation remains a key issue since transportation means are gradually becoming saturated in capacity in modern countries. Therefore, the European Union (EU) develops initiatives to enhance the rail grid competitiveness, by means of deregulation and interoperability, and supports this process with an existing rail network planned upgrade. In such a context, the 6thEuropean Framework Program (FP6) CATIEMON project (CATenary InterfacE MONitoring; 2005-2009), has been specifically devoted to the development of instrumentations and sensors able to 'control' any train entering a railway network. This was achieved by monitoring the interaction between the train pantograph and its Overhead Contact Line (OCL) at a standing location: a control gate, equipped with permanently controlled sensors. Several solutions have been simultaneously evaluated, including different kinds of sensors and measurement systems. The electromagnetic-immune Optical Fibre Bragg Grating (FBG) sensing technology developed by CEA List has demonstrated, within this project, fully relevant, reproducible, and exploitable measurements for the infrastructure manager. To do so, we have been working on the entire FBG instrumentation, including the development of innovative sensors, as well as the set-up of two proprietary measurements units. The first one, lightweight, small-form factor one: BraggLight, proved on field to be very handy to work in 'acrobatic' and bad weather conditions for FBG sensor lines control during their installation on the OCL. The second one, BraggFit3, with high-end performances, devoted to high-speed and very accurate Bragg wavelength measurements (resolution and precision better than 1 pm at 1 kHz full speed in parallel on 6 optical lines) for permanent monitoring purposes. Such developments enable today the infrastructure managers to control the rolling stock operators' compliance with their specific regulation procedures (e.g.: authorized maximum wear on the OCL), and allow them to stop any train identified by the control gate to potentially damage their infrastructure. More generally, the FBG sensors and systems developed at CEA list can be used in many industrial sectors, including transportation (railway, marine, aeronautics) but also civil infrastructures (bridges, buildings, power plants, underground...), as well as oil & gas industry, for structure monitoring and smart structure purposes, and are particularly well-suited in harsh environments where non-intrusive high-speed sub-picometric (~ 0.5 µm/m or 5/100°C at 1 kHz) Bragg wavelength accuracy and resolution are required.
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