The new generation of live tracking
Technology of the future: Distributed Acoustic Sensing (DAS) transforms fibre optic cables into virtual microphones. What emerges from that is a fascinating potential for monitoring train operations as well as railway infrastructure.
Over the last five years it has become clear that fibre optic acoustic sensing, based on technologies such as Fibre Bragg Grating (FBG) or Distributed Acoustic Sensing (DAS), is attracting increasing interest among railway operators and signalling experts. Together with various suppliers and operators, Frauscher has carried out a number of real-life tests relating to various fields of application and operational availability.
After these comprehensive evaluation exercises, our experts involved in the process stated that DAS would have the greatest potential to become a base technology for numerous railway-specific applications. This conclusion was reached against a massive background of knowledge about signalling technologies.
Future network: Using DAS, glass fibres become sensors and communication media at once for tomorrow’s train tracking
DAS for railway operation: Possibilities and potentials
Considering the factors relevant to this industry, trains, maintenance vehicles, personnel, trespassers, environmental events and more can be detected. From this emerge applications for railway operations, including the monitoring of components on tracks and trains as well as the securing of infrastructure.
From a technical point of view, it is already possible to track events and components on and near the track over a distance of 40 kilometres using just one DAS based monitoring unit, with whole networks being monitored by multiple connected units.
Innovative algorithms allow for individual categorization of tracked events. On that basis, specific alarms and reports can be generated.
Limitations of DAS for railway operations
However, the railway industry has its very own requirements and standards, so a comprehensive development of existing approaches is essential. The needs of continuous train tracking in particular will present new challenges to already known DAS based solutions. Looking at the most important factors, the main limitations of using DAS on railways can be described as the following:
- Track ID: Current DAS systems cannot identify whether the indications detected are actually on the track or close to it. It is also difficult to define on which track a train is moving within multi-track areas and nearly impossible in more complex track layouts.
- Accuracy: With the current status of technology, DAS does not yet have the proven capability to detect individual axles in a robust or failsafe manner, which is required for safetyrelevant application, such as train integrity along long stretches of network.
- CENELEC compliance: Until now, basic developments and processes have not generally been fulfilled to create a solid foundation for SIL applications based on DAS. Also, the existing limitations regarding the accuracy and location of the occurrence will need to be resolved at least to a certain degree in order to achieve CENELEC compliance.
DAS as a base technology for railway applications
However, these limitations can be overcome. Innovative solutions and intelligent combination of various approaches allows for a use of DAS as a base technology for railway applications. Within this issue of Ultimate Rail you can learn more about how Frauscher is managing these hurdles.
Let us tell you about how DAS will surely revolutionise the nature of railway operations and about how to benefit from undreamed-of possibilities without the need to install additional components on your tracks.
DAS solutions are able to monitor 40 kilometres of track using only one fibre optic cable
How does DAS work?
The principle of Distributed Acoustic Sensing is based on changes in the intensity of light reflections caused by sound waves radiating against a singlemode fibre optic cable. These changes can be detected. Using specially developed algorithms it is possible to transform measurable signatures into valuable information about train movements, people on and near the tracks and additional activities such as manual and machine digging. These DAS capabilities are in use in the oil, gas and border protection businesses. Any single-mode fibre can quickly be turned into a series of listening devices using DAS with minimal fibre work at either end of the monitored fibre section. Using spare capacity on the existing fibre cables next to a track makes it possible for similar and related applications to be realised for railway-specific requirements.
Functional principle: Laser impulses transform fibre optic cables into virtual microphones that can detect ambient noises
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