POF - The new Fibre is about to jump to light speed

A new breed of optical switch 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 – the last mile, where connections running over copper wires persist.

A cheaper alternative is to use plastic optical fibre (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.

Femtosecond switch
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.

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