Shedding light on rogue waves

Physics World points us to an article from the most respected journal in science; Nature. They tell us;

Every so often mariners report the sighting of a huge wave towering up to 30 m above the regular swells of the ocean surface. No-one is sure why these rogue waves form, but now physicists in the US and Germany have managed to produce equivalent optical rogue waves by launching laser pulses into photonic-crystal fibres. Having performed computer simulations of the optical system, the researchers suggest that optical rogue waves, and therefore oceanic rogue waves, are seeded by noise.

A photonic-crystal fibre is a transparent strand containing hundreds of regularly-spaced air holes running throughout its length. The alternating refractive index produced by this structure has a non-linear effect on light waves, shifting their frequency depending on the wave intensity.

When a wave pulse — which comprises many waves with a bell-shaped distribution of frequencies — enters a photonic crystal fibre, its frequency spectrum is broadened. Rogue waves are examples of wave pulses, but their short, sharp nature requires too broad a frequency spectrum to be produced by this process alone.