A team from the Hong Kong Polytechnic University is to release details of a seven-year program to monitor a 36-km stretch of high-speed rail line using a series of special fiber optic sensors . According to a press release put out by the Optical Society, the system has detected "anomalous vibrations" on 30 occasions, allowing the early rectification of emerging problems that could conceivably have gone on to cause rail accidents.

The system uses fiber Bragg gratings (FBGs), which are special reflectors built within fiber optic cables that reflect only certain wavelengths of light at any given time. When embedded into either the track or mechanical components of trains, those wavelengths change measurably according to stresses, strains and temperature changes. By monitoring these measurements, the FBGs can be used to identify anomalous and potentially dangerous conditions such as excessive vibrations and mechanical faults.

In the seven years since its installation, the system has taken over 10 million measurements along the high-speed commuter line joining Hong Kong and China. Of the 10 million, only 30 are thought to have been out of the ordinary. However, according to the Hong Kong Polytechnic University's Hwa-yaw Tam, in a handful of cases these were early warnings of emerging dangers. Because the system is optical, electromagnetic interference from the rail power lines isn't an issue.

Tam claims that the system is a third of the price of other warning systems which require the integration of data from numerous sources. It's also claimed that the system saves the rail operator US$250,000 per year in maintenance. According to the press release, the system is now being installed along all of Hong Kong's commuter routes with certain rail lines in Singapore and Australia to follow.

The Hong Kong team is to present its findings to the Optical Society's annual meeting next week.

Source: The Optical Society