Fibre optics help detect rail damageSteve BushResearchers in the US are using optical fibres to detect damaged rails and train wheels.
"Our sensors are based on optical signal transmission through sensitive optical fibres that are firmly attached to the rails with epoxy and tape," said Shun-Lien Chuang, a University of Illinois professor of electrical and computer engineering. "We use fibre optics to sense an environmental change, such as the weight of a passing train or the strain created by a cracked, broken or buckled rail."
One sensor design uses an optical time domain reflectometry system. The weight of a passing train causes strain in the rail, which is transferred to the attached fibre. This sensor can also be used for detecting a train's position and speed.
Another sensor is based on total internal reflection changes due to micro-bending. "We can calibrate the intensity of the optical transmission as a function of the applied bending pressure," Chuang said.
By wiring a short length of track, damaged wheels can be detected.
A palm-sized sensor also offers a fast and cost-effective method to detect deformities - particularly flat spots - in rail-car wheels through dynamic loading on the rail, said the university.