BRINGING optical data links into people鈥檚 homes could be made much cheaper
by a British chip that joins optical fibres to each other. This could make it
economic to do away with the copper cables that are still the final link for
most consumers, and would be a big boost for digital consumer services.
Existing chips for connecting optical fibres typically cost more than
拢1000. Bookham Technology, the company based near Oxford that has
developed the new chip, says it can make one for a tenth of that price.
The technology for fabricating the chip was developed by Bookham at the
Rutherford Appleton Laboratory, and uses a combination of silicon processing
and micromachining.
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鈥淚t鈥檚 a combination of established techniques,鈥� says Mette Tholstrup,
Bookham鈥檚 marketing manager. 鈥淏ut we have used silicon, which is reliable and
low cost. Other companies making chips for this sort of work use lithium
niobate, which is much more expensive.
The new fabrication method makes connecting optical fibres much easier as
well as cheaper. Optical systems are extremely sensitive to any misalignment
of the fibres, which can lead to signal losses. This adds to the cost of
existing links, because it takes a lot of testing to check that the fibres are
aligned correctly.
Bookham鈥檚 system shapes the chip at a microscopic level so that when the
fibres are plugged into the ends of a chip they are automatically aligned to
less than 1 micrometre. The chip takes incoming light signals and transmits
them directly to another fibre or converts them into electrical impulses.
These electrical signals can, if necessary, be distributed to a number of
other points where they are converted back into laser light by a semiconductor
diode, for transmission down separate optical fibres.
鈥淭he cost advantage is tremendous,鈥� says Tholstrup, 鈥渁nd by integrating all
these things onto one chip we simplify the packaging.鈥�
At present, most optical cables terminate at a single 鈥渉ead end鈥� that
handles the signals for a whole street. Just one expensive fibre optic
connection is needed, and the multiple connections at the other side of the
junction are through cheap copper wire.
But the copper links are information bottlenecks, and services such as
video-on-demand would ideally use optical fibres all the way. To pass through
copper wires, video signals have to be heavily compressed, and this can lead
to a loss of picture quality.
Bookham developed its chip in collaboration with the Danish national
telephone company. 鈥淲e were going to collaborate with British Telecom, but we
got a better deal from the Danish company,鈥� says Andrew Rickman, Bookham鈥檚
managing director.
The company says that the same technology could one day be used in
applications such as industrial measurement equipment, environmental and
automotive sensors, and medical diagnostic systems.
