Luna’s Fiber Optic Sensing Used in Railway Test in France

Luna Technologies’ fiber optic sensing system, the Optical Backscatter Reflectometer (OBR) 4400 device with distributed Rayleigh sensing, was used in an experiment by the French Public Works Research Laboratory in conjunction with the French National Railway for the possible use as a cavity detection or sink hole warning system on railway track beds and tunnels.

Embedded cavities, or sink holes that may induce soil collapse present a major risk to the French railway system. Current technologies such as ground penetrating radar, seismic analysis or infrared thermography are increasing in use to locate cavities, but do not offer continuous embedded cavity monitoring, a major concern for rail companies and a key benefit of Luna’s solution.

The experiment conducted a full-scale laboratory investigation of Luna’s OBR, which uses optical frequency-domain reflectometry, together with a competing technology that uses Brillouin scattering. The instruments were tested for spatial and strain sensitivity, parameters that are key in determining the size and location of cavities or sink holes. The technologies were benchmarked against a Finite Element Analysis (FEA) model to check for device accuracy and sensitivity. The study concluded that Luna’s OBR was the better option for use in a cavity detection system due to its superior performance. The OBR technique was more viable due to higher spatial and strain resolution, resulting in better detection and size determination of the embedded cavities.

In the test, the OBR identified a 5 mm embedded cavity located 2 meters away from the sensing cable.

These findings were published in Measurement Science and Technology in an article titled “Soil-embedded optical fiber sensing cable interrogated by Brillouin optical time-domain reflectometry (B-OTDR) and optical frequency-domain reflectometry (OFDR) for embedded cavity detection and sinkhole warning system.” Measurement Science and Technology is an international journal published by the Institute of Physics that is devoted to the theory, practice and application of measurement in physics, chemistry, engineering and the environmental and life sciences from inception to commercial exploitation. To access the article, visit http://is.gd/u90z.