A laser network, in trading, is a communications link that sends market data and orders between data centres as beams of infrared light through open air, a technology known as free-space optics. Light travels through air at close to its speed in a vacuum, about half as fast again as it travels through the glass of an optical fiber, and the beam can follow a nearly straight line between rooftops or towers. Both properties reduce delay, which is the aim of low latency infrastructure used in high-frequency trading.
Laser links carry more data than a microwave network but work over shorter hops, so they are used mainly for metropolitan routes, such as those connecting the exchange data centres around New York. Fog and haze weaken a laser beam, while heavy rain mainly affects radio, so operators often pair lasers with millimetre-wave radio and switch between them as conditions change. Firms using colocation buy capacity from specialist providers.