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How Laser Communication Works

        Science | Optics

Laser Communication Applications: From Outer Space to Wall Street

Laser communications may be a boon for space exploration, but far more earthly pursuits will determine its fate as a commercial technology.

Take, for example, Wall Street's emerging breed of high-speed traders who leverage the power of quantitative analysis, the speed of premium broadband and a multiplicity of microtransactions to pile up earnings one fractional penny at a time. For a business built on "robo-traders," computer algorithms making millisecond trades according to a set of rules, transmission time is money, and lasers are the fastest game in town [sources: Adler; CBS News; Strasburg].

To squeeze the most out of each trade, companies like Spread Networks invested in the best available fiber and cut every kink and curve they could from the data hoses connecting trade capitals like Chicago, New York, London and Tokyo (each extra mile adds about eight microseconds to data round-trips). When that wasn't fast enough, others groups, like McKay Brothers and Tradeworx, cast fiber optics aside in favor of microwaves beamed through the air. Though only a step above radio in terms of power and speed, microwaves travel faster through air than light passes through fiber optics [sources: Adler; Strasburg].

Lasers would potentially post the fastest speeds of all; the speed of light through air is nearly as fast as in a vacuum, and could traverse the 720 miles (1,160 kilometers) separating New York and Chicago in about 3.9 milliseconds -- a round-trip (aka latency) of 7.8 milliseconds, compared to 13.0-14.5 milliseconds for new fiber optic systems and 8.5-9.0 milliseconds for microwave transmitters [source: Adler].

In the security sphere, lasers and other optical communications systems offer more secure communications -- and the means to eavesdrop on them. Quantum cryptography takes advantage of a property of quantum physics -- namely, that a third party cannot detect the quantum state of the photonic encryption key without altering it and, therefore, being detected -- to establish highly secure communications using beams of photons created by attenuated lasers [sources: Grant; Waks et al.]. In fall of 2008, researchers in Vienna began experimenting with a quantum Internet based in part on this principle [source: Castelvecchi]. Unfortunately, lasers have also been used to intercept and spoof such signals in a non-quantum way, thereby circumventing detection. Quantum encryption companies are working to address the problem [sources: Dillow; Lydersen et al.].

In fact, the main drawbacks to laser communications within the atmosphere have to do with interference by rain, fog or pollutants, but given the technology's advantages, these issues are unlikely to stop the forward progress of the technology. So, literally or figuratively, the sky is the limit for laser communications technologies.