It is easy to set up: simply hook up infra-red laser transceivers on top of two buildings and then align them.

An upgraded bomb, when falling, USES data from the global-positioning system in combination with laser and infra-red sensors to adjust a set of fins that work like aeroplane flaps.

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.