Airport security: blanket of light? (see details)?

Some time ago, i've seen a documentary on National Geographic Channel about an airport security system: a blanket of (invisible) light across the whole perimeter. When broken, one would know something's up. If I remember correct the airport was located on a Japanese artificial island. Does anyone knows how this system works exactly? Or its name? Or perhaps the name of the airport?

I don't know about the blanket of light, but the airport you are referring to is probably Osaka's Kansai International Airport, which is built on a man made island.