The beam itself will be produced by a device called a fibre laser.

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In the case of Dr Sweeney's fibre laser, the beam will have a wavelength of 1.5 microns, making it part of the infra-red spectrum.

ECONOMIST: Solar power from space

Moreover, engineers have worked out how to make laser beams more intense by using short lengths of optical fibre to narrow the beam.

ECONOMIST: Monitor

This generates the coherent light of a laser beam in the core of a long, thin optical fibre.

ECONOMIST: Solar power from space

So when Mr Blum travels to the tiny Cornish village of Porthcurno, he is able to see the landing stations for many of the great transatlantic fibre-optic cables that carry traffic in the form of beams of pulsating laser light between Europe and the Americas.

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