Explosive information demand in the internet world is creating enormous needs
for capacity expansion in next generation telecommunication networks. It is expected
that the data- oriented network traffic will double every year.
Optical networks are widely regarded as the ultimate solution
to the bandwidth needs of future communication systems. Optical fiber links deployed
between nodes are capable to carry terabits of information but the electronic
switching at the nodes limit the bandwidth of a network. Optical switches at the
nodes will overcome this limitation. With their improved efficiency and lower
costs, Optical switches provide the key to both manage the new capacity Dense
Wavelength Division Multiplexing (DWDM) links as well as gain a competitive advantage
for provision of new band width hungry services. However, in an optically switched
network the challenge lies in overcoming signal impairment and network related
parameters. Let us discuss the present status, advantages and challenges and future
trends in optical switches.
A fiber consists
of a glass core and a surrounding layer called the cladding. The core and cladding
have carefully chosen indices of refraction to ensure that the photos propagating
in the core are always reflected at the interface of the cladding. The only way
the light can enter and escape is through the ends of the fiber. A transmitter
either alight emitting diode or a laser sends electronic data that have been converted
to photons over the fiber at a wavelength of between 1,200 and 1,600 nanometers.
Today fibers are pure enough that a light signal can travel for about 80 kilometers
without the need for amplification. But at some point the signal still needs to
be boosted. Electronics for amplitude signal were replaced by stretches of fiber
infused with ions of the rare-earth erbium. When these erbium-doped fibers were
zapped by a pump laser, the excited ions could revive a fading signal. They restore
a signal without any optical to electronic conversion and can do so for very high
speed signals sending tens of gigabits a second. Most importantly they can boost
the power of many wavelengths simultaneously.
to increase information rate, as many wavelengths as possible are jammed down
a fiber, with a wavelength carrying as much data as possible. The technology that
does this has a name-dense wavelength division multiplexing (DWDM ) - that is
a paragon of technospeak.Switches are needed to route
the digital flow to its ultimate destination.
The enormous bit conduits will flounder
if the light streams are routed using conventional electronic switches, which
require a multi-terabit signal to be converted into hundreds of lower-speed electronic
signals. Finally, switched signals would have to be reconverted to photons and
reaggregated into light channels that are then sent out through a designated output
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