-Caveat Lector-
> WSWS : News & Analysis : Science & Technology : The Internet and
> Computers
>
> New techniques to boost the Internet's capacities
>
> By Luciano Fernandez
> 16 July 1999
>
> Back to screen version
>
> The rapidly increasing demands being placed on international
> communications networks are fueling some remarkable technical
> developments in the field of fibre optics.
>
> The main impetus has been the tremendous expansion in the use of
> the Internet—both in the number of users and in its extension to
> areas such as graphics, sound, video and potentially other areas
> of communications such as voice and video conferencing.
>
> The growth in the number of people on line is staggering. In June
> 1997 it was estimated that 82 million people were using the
> Internet, with forecasts that by 2002 up to 329 million people
> would be going on line each day. Up to 16.6 million people across
> Europe use the Internet. In Britain it was estimated that 25
> percent of the population would be on-line by the middle of 1999.
> In Australia up to 30 percent of households are already online.
> In countries like India and Indonesia, Internet usage is low per
> head of population but still numbers in the millions, especially
> among younger, educated layers.
>
> The establishment of the World Wide Web in 1993 made possible the
> extensive use of graphics, sound and video and has led to more
> and more complex designs for web pages and sites. Each of these
> new applications has led to greater demand for carrying capacity,
> technically known as bandwidth, to ensure ease and speed of
> access to Internet sites.
>
> Over the past 20 years, the use of fibre optic cables by major
> communications companies has allowed them to stay ahead of demand
> and substantially improve telecommunications internationally. But
> the rapidity of the growth of the Internet and telecommunication
> usage has created pressures on existing fibre optic systems. They
> are in danger of becoming overloaded and unable to cope with
> demand.
>
> To lay more cable using the same technology is a very expensive
> exercise. The other option is to develop new technologies that
> will enhance the capacities of existing cables. It is the latter
> to which most attention has been given. Major firms have spent
> millions to develop the technology needed to expand bandwidth,
> and there have been some remarkable results.
>
> Information is carried along a fibre optic cable by a laser beam
> of light at a certain frequency (or colour). In the past, a
> single fibre optic thread has had the capacity to transmit a
> single frequency. Now, however, scientists have developed the
> technical means to enable a number of frequencies to pass along a
> single fibre.
>
> Two technical breakthroughs were necessary. Firstly, tiny optical
> filters, called in-fibre Bragg gratings, were developed that
> create light of a number of slightly different, but distinct
> frequencies. Bragg gratings are manufactured by irradiating the
> fibre core with UV light, a process that permanently changes the
> glass's refractive properties, according to a definite pattern.
> Secondly, a means of amplifying the signal was developing by
> “doping” or adding minute quantities of rare-earth ions to the
> core of the optical fibre.
>
> These components are very effective and also inexpensive to
> produce, and have rapidly replaced the outdated and cumbersome
> optical devices that were used previously. The outcome has been a
> system known as Dense Wavelength Division Multiplexing (DWDM)
> that has dramatically increased bandwidth.
>
> In the past when one frequency was able to pass through an optic
> cable, the fibre's capacity was around 2.5 gigabits per second
> (Gbps). In 1996, Bell Laboratories developed a multiplexer able
> to pass eight frequencies along an optic cable, boosting the
> bandwidth to 20 Gbps. Present DWDM technology allows as many as
> 400 frequencies to be transmitted simultaneously or about 1,000
> Gbps—roughly equivalent to the transfer of the information
> contained in 20,000 novels each second.
>
> So quickly is this technology developing that by the end of the
> year scientists are preparing to pass up to 1,000 frequencies
> along an optic fibre, which has the thickness of a human hair.
> Experiments are now being prepared to test the possibility of
> transmitting at a trillion bits (terabit) of information per
> second—more than was being passed through the entire Internet a
> year ago.
>
> DWDM will reduce costs significantly. In an ordinary fibre optic
> cable, the signal requires boosting after 40 kilometres, but with
> the DWDM system the signal only needs to be boosted after 100
> kilometres. DWDM also uses fewer components and is more reliable,
> which means a saving in installation and maintenance costs. It
> has being calculated that as DWDM technology is introduced more
> widely its costs will drop by a further 30 percent each year. It
> can also be used in inter-office and metropolitan networks and by
> smaller operators such as universities that require large data
> handling.
>
> Despite these astonishing developments there are still drawbacks
> to be overcome. The main problem is now not the bandwidth of the
> optic fibre but rather the processing of the huge amount of data
> at either end. Information travels at the speed of light along
> the optic fibre, but at either end the complex switching
> processes use much slower electronic technology.
>
> To overcome these deficiencies, researchers and scientists are
> turning to the field of photonics. Just as electronics involves
> the manipulation of signals imprinted on streams of electrons, so
> photonics aims to directly manipulate the information in the
> laser beams in optical fibres. Corporations are now seizing upon
> what appeared to be a somewhat abstruse area of research in the
> 1970s and 1980s.
>
> Large amounts of money are being poured into photonic research
> because huge profits appear likely. The growth in demand for
> photonic devices including DWDM systems has expanded in the US
> from almost zero in 1994 to $1.5 billion in 1997, and is expected
> to grow to $4 billion by 2001.
>
> The present drive is to develop a photonic switching device that
> can redirect the enormous amount of information without having to
> carry out the slow and time-consuming process of changing from
> optical signals to electronic signals and back again. The next
> generation of DWDM technology will seek to incorporate optical
> cross-connectors able to switch individual frequencies of light
> between fibres.
>
> Astarte Fibre Networks already supplies optical cross-connect
> switches, which use a piezoelectric material to switch light from
> 72 incoming fibres to another set of outgoing fibres. The device
> could be used to restore services instantaneously if a fibre is
> cut. At present, however, their use remains limited and they are
> not suitable for long distance operations.
>
> The race is also on to develop the optical equivalent of a
> router—a device which reads the incoming stream of information
> and switches individual “packets” in the appropriate direction. A
> European consortium, ACTS, has demonstrated a rudimentary optical
> device which performs this function, but prospects for an optical
> router still remain rather distant.
>
> These latest developments provide a glimpse of the enormous
> potential for further leaps forward in telecommunications and the
> expansion of the Internet to include facilities such as
> video-on-line and video conferencing that are beyond the
> capabilities of the present technology.
>
>
>
>
>
> -----------------------------------------------------------------
> -------
>
> Copyright 1998-99
> World Socialist Web Site
> All rights reserved
>
>
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