Optical
Networking and Dense Wavelength Division Multiplexing
This
paper deals with the twin concepts of optical networking and dense wavelength
division multiplexing. The paper talks about the various optical network architectures
and the various components of an all-optical network like Optical Amplifiers,
Optical Add/Drop Multiplexers, Optical Splitters etc. Important optical networking
concepts like wavelength routing and wavelength conversion are explained in detail.
Finally this paper deals with industry related issues like the gap between research
and the industry, current and projected market for optical networking & DWDM
equipment and future direction of research in this field.
INTRODUCTION
One of the major issues in the networking industry today is tremendous demand
for more and more bandwidth. Before the introduction of optical networks, the
reduced availability of fibers became a big problem for the network providers.
However, with the development of optical networks and the use of Dense Wavelength
Division Multiplexing (DWDM) technology, a new and probably, a very crucial milestone
is being reached in network evolution. The existing SONET/SDH network architecture
is best suited for voice traffic rather than today's high-speed data traffic.
To upgrade the system to handle this kind of traffic is very expensive and hence
the need for the development of an intelligent all-optical network. Such a network
will bring intelligence and scalability to the optical domain by combining the
intelligence and functional capability of SONET/SDH, the tremendous bandwidth
of DWDM and innovative networking software to spawn a variety of optical transport,
switching and management related products.
Optical
Networking Optical networks are high-capacity telecommunications networks
based on optical technologies and component that provide routing, grooming, and
restoration at the wavelength level as well as wavelength-based services. The
origin of optical networks is linked to Wavelength Division Multiplexing (WDM)
which arose to provide additional capacity on existing fibers. The optical layer,
whose standards are being developed, will ideally be transparent to the SONET
layer, providing restoration, performance monitoring, and provisioning of individual
wavelengths instead of electrical SONET signals. So in essence a lot of network
elements will be eliminated and there will be a reduction of electrical equipment.
It is possible to classify networks into three
generations depending on the physical-level technology employed. First generation
networks use copper-based or microwave technologies e.g Ethernet, satellites etc.
In second generation networks, these copper links or microwave links with optical
fibers. However, these networks still perform the switching of data in the electronic
domain though the transmission of data is done in the optical domain. Finally
we have the third generation networks that employ Wavelength Division Multiplexing
technology. They do both the transmission and the switching of data in the optical
domain. This has resulted in the onset of tremendous amount of bandwidth availability.
Further the use of non-overlapping channels allows each channel to operate at
peak speeds. 1.2 Dense Wavelength Division Multiplexing (DWDM)
Dense
Wavelength Division Multiplexing (DWDM) is a fiber-optic transmission technique.
It involves the process of multiplexing many different wavelength signals onto
a single fiber. So each fiber has a set of parallel optical channels each using
slightly different light wavelengths. It employs light wavelengths to transmit
data parallel-by-bit or serial-by-character. DWDM is a very crucial component
of optical networks that will allow the transmission of data: voice, video-IP,
ATM and SONET/SDH respectively, over the optical layer.
Hence
with the development of WDM technology, optical layer provides the only means
for carriers to integrate the diverse technologies of their existing networks
into one physical infrastructure. For example, though a carrier might be operating
both ATM and SONET networks, with the use of DWDM it is not necessary for the
ATM signal to be multiplexed up to the SONET rate to be carried on the DWDM network.
Hence carriers can quickly introduce ATM or IP without having to deploy an overlay
network for multiplexing.