Engineers test US-Mexico border-monitoring system

The border-monitoring system − known as Helios − consists of fibre-optic cables, lasers and detectors. More accurately described as a distributed acoustic sensor, it relies on the phenomenon of optical backscattering for its operation and is made by British company Fotech Solutions.

In use, the system transmits laser pulses through fibre-optic cables buried in the ground. The small vibrations caused by a moving object on the surface above hit the fibre-optic cables, slightly distorting them. The distortion creates a unique signature change in the laser pulses, which can be detected by a Helios detector at one, or both, ends of the cable.

Helios is sensitive enough to detect a dog and can discriminate between people, horses and trucks. The system can be set to avoid being triggered by small animals and can also tell if people are running, walking or digging and in which direction.

The resolution of the cable can be set to one-metre intervals, which means that people, or vehicles, can be pinpointed instantly to within one metre along a section of cable that can be up to 50km long.