Optical fibres may make for ultrafast home networks

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Washington, Jan 25 : A new ultrafast technology that transmits TV, telephone and Internet signals via a separate group of light rays through optical fibre cable has been developed.

A Dutch-sponsored researcher Christos Tsekrekos has analysed the Mode Group Diversity Multiplexing (MGDM) technique of the Eindhoven University of Technology and examined how a small network for home or company can function optimally.

Though this technology has not yet been marketed, in the ideal situation it could be applied in a glass or polymer fibre. It also has the potential of being cheap, and transmits all information without disruption.

Currently, the systems for small networks at home or in a company make use of multimode glass fibres or multimode polymer optical fibres (POF) that are relatively thick cables. Multimode fibre cables can conduct many light rays and can operate without any disruption and with a greater bandwidth than a wireless connection.

However, a signal transmitted by all of these rays becomes spread out owing to a slight variation in the speed of the light rays through the multimode fibre. As a result, the signals become broader and thus fewer signals fit in the fibre, restricting the transmission capacity.

Tsekrekos investigated how the MGDM technique can increase the capacity of a multimode fibre network. For this he created independent channels by dividing the total group of light rays into groups of closely related light rays (or modes).

By utilising special optical and electrical techniques, he examined how the crosstalk between these groups could be eliminated so as to render these groups independent of each other.

This step facilitated several groups to be used in parallel, thereby increasing the fibre's capacity. Also, each group can transport its own type of signal, which means that TV, telephone and Internet signals can be transmitted though the same fibre.

The researcher constructed a simple yet stable MGDM system by using this approach. This system works well up to distances of 1 km of multimode glass fibre with a core diameter of 62.5 m.

In order to make the system reliable and to allow a large number of channels to be realised, Tsekrekos invented a new mode-selective spatial filter (MSSF), based on lenses with specific characteristics.

This can lead to a stable and transparent five-channel MGDM system.

This MGDM technology combined with thick multimode glass or polymer fibres will soon enable consumers to simply install a universal and high capacity broadband network at home.


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