A handful of start-up companies have begun offering new systems that make use of the light in fiber optic cables while shucking both the fiber and the cable. The systems send infrared laser beams, carrying data at rates up to a billion bits per second, from one building to another through the air.

The beams can travel from one laser transceiver mounted behind a high-rise window, say, to another laser perched behind a window many blocks away, and then on to other buildings, leapfrogging until the data reaches a site with a direct connection to the fiber backbone.
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