New optical switch could vastly increase Internet data speeds

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Washington, October 22 (ANI): Researchers have produced an all-optical switch within a plastic optical fibre (POF), which could vastly increase Internet data speeds.

The high-speed backbone of the Internet is based on networks of glass optical fibres. But this is too fragile and expensive to install in the small distances between local exchanges and the home.

A cheaper alternative is to use POF, but this has been unable to transmit data with the kind of speeds that would make it worth replacing copper.

That may soon change. In recent years, POF with a bandwidth of 1 gigabit per second over 100 metres has been demonstrated.

Now, Polycom, a European Union-funded collaboration between researchers across Europe, has shown how to squeeze more data into a POF, bringing it a step closer to the market.

Polycom has produced an all-optical switch within a POF that can turn an optical signal on and off on in a matter of femtoseconds.

Using an array of these switches it is possible to introduce a technique called time division multiplexing, in which two or more data streams are divided into small chunks of short duration before the various segments are interleaved together and sent down the same fibre.

The new optical switch can be turned on and off so precisely that it could help separate out the time chunks belonging to a specific data stream, and recombine them.

The POFs used by the Polycom team are composed of a transparent plastic, PMMA, doped with around 0.02 per cent by weight of a polyfluorene.

The fibres demonstrate good gain properties, which means a data signal passing through them can be amplified.

That is necessary to maintain signal quality at optical-fibre splitters, where the signal is divided and sent along several fibres.

The boosting is achieved by first exposing the doped polymer to a short laser pulse, which excites an electron in the polyfluorene.

In a typical inorganic semiconductor, the excited electron is free to move around, leaving behind a hole.

But in the polyfluorene the electron and hole remain tightly bound, creating a quasiparticle called an exciton.

"If a data signal comes through the fibre now it gets amplified by stimulated emission through interaction with the exciton," said Jenny Clark of the University of Cambridge, a member of the Polycom team.

"We found that if you physically isolate the polymer chains, you can isolate the charge to one dimension along each polymer chain. The charges are confined, with nowhere to go, so they recombine quickly," she added. (ANI)

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