Fibre optics help detect rail damageSteve Bush
Researchers 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.