India Installs 'Laser Walls' At Border With Pakistan (nbcnews.com)
schwit1 writes: After experimenting with barbed wire, surveillance cameras and even cowbells and camels, India has now reportedly introduced "laser walls" at its border with archenemy Pakistan. Both New Delhi and Islamabad deploy more than half of their 1 million and 600,000-strong armies, respectively, on the border. India is setting up the laser walls to "plug the porous riverine and treacherous terrain and keep an effective vigil against intruders and terrorists" in Punjab state, the state-run Press Trust of India reported. According to the PTI report, around 45 laser walls will be installed in Punjab state. Lasers beamed over rivers and hills will set off an alarm and alert the Indian Border Security Force if someone attempts to pass by, it added.
It's a detection system
You use modulated beams encoded with a non-repeating data stream so that any variance in latency resulting from deflection of the beam can be detected.
Oh, say does that Star-Spangled Banner entwine / The myrtle of Venus with Bacchus's vine?