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by Michael Kenward
Originally Published: July 16 2001 10:25GMT
By: The Financial Times
Even in these days of market gloom for telecoms, there are
some bright spots. Indeed, some see the downturn as good
news for the spread of optical wireless, or free-space
lasers. In this technology, a laser beam sends a signal
through the air, rather than along a glass fibre, to a
receiver a short distance away.
More than 90 per cent of large buildings in North America
are not connected to the optical telecoms network. A frenzy
of fibre-laying at the peak of the boom also means that more
than 90 per cent of the installed capacity in that fibre
optic "backbone" lies idle. However, an
inexpensive and easily installed way of bringing the two
together could give operators an easy way to add customers
quickly.
Free-space lasers are one option. They do not even need a
licence to operate, reducing the cost and time it takes to
bring a system online. A growing number of companies are
developing and supplying systems to plug this gap in the
chain. There are already hundreds of laser links in various
applications around the world.
The attributes of free-space lasers, also known as optical
wireless, are such that the technology can also work inside
buildings, connecting users to a local network. Lasers can
also operate between buildings on a campus, where the aim is
to join the two in a local network rather than to plug into
the long-distance backbone. Optical wireless is also making
inroads into mobile networks, where it connects base
stations to the fibre backbone, in what is known as the
"back-haul link".
Optical wireless is simplicity itself. It is the modern
equivalent of the beacon bonfire or a signal lamp. Connect a
laser transceiver (transmitter-receiver) to a network, aim
the device at a transceiver in another building. The
transceiver at either end just plugs into the local network
hardware. Radio links can achieve the same effect, but they
often require a licence for the requisite frequency and are
more susceptible to determined eavesdroppers and
electromagnetic interference. Some of the preliminary
R&D on free-space lasers happened at the Martlesham
Laboratory of British Telecommunications in the early 1990s.
David Heatley, head of research for the emerging
technologies laboratory at BTexact Technologies, the
telecoms company's R&D operation, says BT decided to
look at free-space links partly because it wanted a solution
to the problem of "digger man". If an excavator
slices through an optical cable, the operator could install
a laser link as a temporary replacement.
Off-the-shelf technology
Dr Heatley and his team at Martlesham in Suffolk decided to
work at the same wavelength as conventional fibre optic
links - 1,550 nanometres (nm) in the near-infrared region of
the spectrum. This wavelength did put up the cost of the
lasers in comparison with those available for the visible
part of the optical spectrum, but - on the benefit side -
the research team could control lasers with off-the-shelf
technology developed for processing the signals carried
along fibre links. Another advantage of working at 1,550nm
is that it is safer on the eye. Lasers are allowed to
operate at higher power in that part of the spectrum. This
makes it easier to produce transmitters that can deliver
enough power over longer distances. The BT research team put
together a system that came very close to the performance of
an optical fibre system. But while a fibre can carry light
for 100km or more before the signal starts to fade away, in
air you are doing well to communicate across much more than
a few kilometres.
Experts in atmospherics
Atmospheric conditions played a larger part than the BT team
had anticipated. "It did surprise us at the time how
much influence atmospherics do have," says Dr
Heatley.
As a part of the project, BT, together with Imperial College
and University College, two parts of London University, set
up a 4km link between the two colleges.
The academic research team became experts in atmospherics,
says Dr Heatley. At the end of the project they were in a
position to relate weather data to the performance of the
optical links.
This research data was invaluable a few years later when
Theresa Carbonneau approached Martlesham for a licence to
exploit BT's work on free-space laser links. Ms Carbonneau
went on to set up fSONA (see separate report on the web:
www.ft.com/fttelecoms), one of a dozen or so companies that
are competing to supply optical wireless systems.
Of all the unlicensed wireless technologies, free-space
lasers offer the greatest speed, up to 155 megabits per
second (Mbps), albeit over shorter distances than some
options. Currently, lasers work over ranges of up to around
2km.
Ms Carbonneau is confident that free-space links can offer
99.9 per cent reliability. This is perfectly acceptable, she
insists, "particularly to people who have no
alternative". Dr Heatley of BTexact may have started
his research in search of a system that could plug temporary
gaps in an optical network, but he now sees this as a minor
application. On the other hand, there is a market for
optical links that can be put in place quickly to create
temporary connections.
Indeed, as a part of BT's experiments, the researchers
installed a laser link at the Silverstone racing circuit.
This allowed Jackie Stewart's Formula 1 team to communicate
between its various locations on the race track.
The Benetton Formula 1 team is a more recent recruit to
laser wireless. The team makes use of a SkyNet 100Mbps
system supplied by the British company PAV Data Systems.
PAV, based in Windermere, has also supplied systems for
mobile operators to connect base stations to backbone
telecommunications networks.
Richard Redgrave, marketing director of PAV, is most
enthusiastic about the rapid rise in laser links in the
mobile sector. "PAV has the largest installed base
worldwide in the cellular area," he boasts, with
systems in more than 40 countries. The award-winning company
exports more than 75 per cent of its output.
In Cairo alone, says Mr Redgrave, more than 500 of PAV's
systems connect cellular base stations to the network.
Lasers, he adds, "really have become core to the
network roll-out strategy".
The ability to install laser links without a licence allows
rapid deployment of base stations. Mr Redgrave cites the
example of an operator that envisaged buying a small number
of lasers to connect new base stations to the network. It
would then replace the lasers with a landline or a microwave
connection. When it saw the low cost and reliability of the
laser link -a laser can pay for itself within six weeks -
the operator abandoned this strategy. Lasers are now a
permanent part of its networks.
Last month, PAV announced new products aimed at operators of
3G networks in metropolitan areas. "We have developed a
solution to match the requirement for increased bandwidth
(34Mbps) across distances of up to 2km," says Mr
Redgrave. "This is ideal for metropolitan and urban
environments, where cell sizes are relatively small and
radio-based solutions can cause interference and pollution
problems."
The growing demand for bandwidth, and the need to find users
for all those fibres and cellular networks, explains why
some people are relatively upbeat in these days of gloom in
telecoms. Ms Carbonneau, for example, believes that the
slowdown in the sector could benefit optical wireless as
network operators look for inexpensive ways to increase
their customer base.
Jim Slaby, an analyst with Giga Information Group, a market
research company, agrees that optical wireless could be
"a little less susceptible to the downturn". He
points out that these systems are usually deployed where
there are few alternatives. "They are doing it because
they just don't have many choices," he adds.
Small companies could be particularly open to the
technology, says Mr Slaby. Large businesses will always be
able to find someone to wire them up. Small companies, on
the other hand "are pretty much ignored". Mr Slaby
expects the business to grow rapidly. He estimates that
sales could reach several hundred million dollars this year,
rising by an order of magnitude within five years.
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