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	Wavelength-division multiplexing - Wikipedia, the free encyclopedia
		WDM, DWDM and CWDM are based on the same concept of using multiple wavelengths of light on a single fibre, but differ in the spacing of the wavelengths, number of channels, and the ability to amplify the multiplexed signals in the optical space.
		Dense Wavelength Division Multiplexing, or DWDM for short, refers originally to optical signals multiplexed within the 1550-nm band so as to leverage the capabilities (and cost) of erbium doped fibre amplifiers (EDFAs), which are effective for wavelengths between approximately 1530 nm and 1560 nm.
		In addition, since DWDM provides greater maximum capacity it tends to be used at a higher level in the communications hierarchy than CWDM, for example on the Internet backbone and is therefore associated with higher modulation rates, thus creating a smaller market for DWDM devices with very high performance levels.
	en.wikipedia.org /wiki/DWDM (2669 words)

	Fundamentals of DWDM Technology
		The emergence of DWDM is one of the most recent and important phenomena in the development of fiber optic transmission technology.
		DWDM systems using optical signals of 2.5 Gbps or less are not subject to these nonlinear effects at short distances.
		DWDM wavelengths from the transponder are multiplexed into a single optical signal and launched into the fiber.
	www.cisco.com /univercd/cc/td/doc/product/mels/dwdm/dwdm_ovr.htm (6177 words)

	DWDM (Dense Wavelength Division Multiplexing) : Teledatacom Glossary
		Dense wavelength division multiplexing (DWDM) is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength.
		DWDM is also sometimes called wave division multiplexing (WDM).
		DWDM promises to solve the "fiber exhaust" problem and is expected to be the central technology in the all-optical networks of the future.
	www.artesyncp.com /resources/glossary/dwdm.html (217 words)

	DWDM no longer too costly for hub interconnects - 2/1/1998 - CED - CA6261041 (Site not responding. Last check: 2007-10-12)
		The DWDM approach for the model is expected to reach cost parity to the cost of dedicated fiber for a single headend-to-hub link at just over 30 route miles, or at the initial hub location.
		By postponing the DWDM installation, present fiber capacity may be saturated and the upgrade may require the replacement of costly laser transmitters, not to mention the delay while the new electronics are ordered and installed, and the service disruption during the upgrade.
		Installing DWDM in current applications is also expected to be less expensive, because the operator only pays a small initial premium for the transmitters, which should not have to be replaced in the future.
	www.cedmagazine.com /article/CA6261041.html (1580 words)

	DWDM
		Furthermore, since DWDM can transmit several signals on a single wavelength, instead of having to use several fibers, the cost of regenerators is drastically reduced (only need to amplify a single fiber instead of many).
		DWDM optical networking systems have revolutionized the transport of information by effectively removing the limits of bandwidth and speed (of course as speed increases however, other limitations have a greater influence and must be accounted for).
		In the future, one could envision a fully optical DWDM network in which the transmission, regeneration, routing, and receiving are all conducted in the optical domain.
	www.disp.duke.edu /~esmiley/opticalnet_dwdm.htm (3090 words)

	Dense Wavelength-division Multiplexing
		The first DWDM coupler design is based on fiber Bragg grating (FBG) filters illustrated in Figure 2.
		Bragg gratings are comprised of a length of optical fiber with the index of the core permanently modified periodically usually when exposed to an ultraviolet interference pattern.
		In a DWDM coupler, a second dichroic filter would be placed where the fiber 2 is located, and additional dichronic filters would be cascaded until all wavelengths have been combined or separated.
	www.fiber-optics.info /articles/dwdm.htm (1427 words)

	IPG Photonics: DWDM
		DWDM solution has proved to be a major advantage and preferred solution to the majority of service providers.
		DWDM solution also provides the mechanism to integrate seamlessly and transport TDM and SONET/SDH signals with Gigabit Ethernet and SAN extension.
		The UWDM Pusk system is an all optical layer DWDM solution optimized for up to 8 channels ultra-long-haul fiber network that can reach over 300km without the need for expensive line amplifiers or repeaters.
	www.ipgphotonics.com /products_telecom_dwdm.htm (118 words)

	Practical Guide to DWDM Testing
		This opens up DWDM transmission in the metropolitan areas where connectivity is a key issue compared to long-haul transmissions where cost per managed bit-kilometer is crucial.
		DWDM systems have established the path for a successful response to the continuous demand for more services, capacity, and bandwidth.
		However, the present growth in DWDM component, subsystem, and system technical development is a clear indication that the race for an all-optical network is wide open.
	www.evaluationengineering.com /archive/articles/1099dwdm.htm (1521 words)

	A review of DWDM
		DWDM technology was made possible with the realization of several optical components.
		As DWDM technology evolves, existing standards are updated or new ones are introduced to address emerging issues.
		DWDM finds applications in ultra-high bandwidth long haul as well as in ultrahigh-speed metropolitan or inner-city networks and, at the edge of other networks (SONET, Internet protocol [IP], and asynchronous transfer mode [ATM]).
	home.comcast.net /~dwdm2/dwdmreview.html (535 words)

	Introducing DWDM
		DWDM spaces the wavelengths more closely than does WDM, and therefore has a greater overall capacity.The limits of this spacing are not precisely known, and have probably not been reached, though systems are available in mid-year 2000 with a capacity of 128 lambdas on one fiber.
		DWDM has a number of other notable features, which are discussed in greater detail in the following chapters.
		Transparency—Because DWDM is a physical layer architecture, it can transparently support both TDM and data formats such as ATM, Gigabit Ethernet, ESCON, and Fibre Channel with open interfaces over a common physical layer.
	www.cisco.com /univercd/cc/td/doc/product/mels/dwdm/dwdm_fns.htm (4874 words)

	DWDM
		Dense wavelength division multiplexing works by putting data from different sources together on an optical fiber, each signal is carried at the same time on its own separate light wavelength.
		Using DWDM, up to 80 wavelengths at OC -48, a total of 200 Gbps (and theoretically more) of data can be multiplexed into a light stream transmitted on a single fiber.
		DWDM networking is optical networking which exploits wavelength routing elements and many wavelength technology.
	ntrg.cs.tcd.ie /undergrad/4ba2.02/optnet/pages/present/dwdm.htm (175 words)

	IP over DWDM
		DWDM performed on an optical fiber serves as the underlying carrier for the optical network.
		DWDM systems are capable of performing switching in the optical domain without having to convert the signal onto the electrical domain.
		The increase in the bandwidth capability of the fiber is the foremost influence of DWDM.
	www-static.cc.gatech.edu /~srini/optical/ip_dwdm (6492 words)

	DWDM: The Big Bang of Optical Networking - Broadband Week 04/02/2001 (Site not responding. Last check: 2007-10-12)
		DWDM allows providers like Level 3 to add more capacity to their networks without lighting or activating "dark" or unlit fiber, thus adding more value to their fiber assets.
		"DWDM is very much the enabling technology for the high bandwidth delivery in the intelligent optical network." He adds that because DWDM systems have become commoditized, vendors have to develop value-added features, such as dynamic light path management to quickly establish circuits for customers.
		While DWDM is being integrated into other network boxes and may disappear as a standalone technology, it is this magical splitting of light that's the heart of next-generation optical products.
	www.broadbandweek.com /news/010402/010402_supp_dwdm.htm (1290 words)

	BaySpec.com
		A single signal channel consists of a frequency band that has a finite pass bandwidth and is centered at a given frequency such as one specified by the ITU Grid.
		DWDM MUX/DEMUX devices in BaySpec have their channel spacing of 50, 100 and 200 GHz.
		In a DWDM device, PMD measures the average time difference of two orthogonal polarization states elapsed when the two corresponding pulses pass through the device.
	www.bayspec.com /Definition-DWDM.htm (1081 words)

	DWDM Training: Telecommunications Training
		DWDM is the key technology at the heart of new systems and networks that offers more bandwidth at less cost.
		DWDM is the technology that allows multiple streams of data to flow in one optical fiber of optical communication networks
		This course provides an advanced technical overview of DWDM and optical networking concepts One of the major issues in the networking industry today is tremendous demand for more and more bandwidth.
	www.eno.com /government/advanced_dwdm4040_training.html (249 words)

	DWDM - EnterpriseNetworkingPlanet - News, trends and advice for network managers
		DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber.
		So, if you were to multiplex eight OC -48 signals into one fiber, you would increase the carrying capacity of that fiber from 2.5 Gb/s to 20 Gb/s.
		A key advantage to DWDM is that it's protocol- and bit-rate-independent.
	networking.webopedia.com /TERM/D/DWDM.html (202 words)

	Implementing DWDM-based networks - 9/1/1998 - CED - CA6261369 (Site not responding. Last check: 2007-10-12)
		DWDM technology deployment requires consideration of system and market issues as well as technical issues.
		In some cases, DWDM couplers at the headend can be replaced with standard optical couplers to achieve the same objective.
		DWDM signal transport from the headend to the hub is not an issue, as broadcast and narrowcast fibers remain separate.
	www.cedmagazine.com /article/CA6261369.html (2931 words)

	DWDM Introduction
		DWDM provides the greatest capacity per fiber -- potentially hundreds of individual fiber-optic signals (i.e.
		DWDM is a proven technology, which offers flat channel bandwidth, flexible channel configuration, low insertion loss and high isolation.
		Modules are available on the C &: L bands, ITU 100GHz grid at channel spacing of 100GHz or 200GHz.
	www.fiberdyne.com /products/dwdmintro.html (261 words)

	DWDM RISING
		As carriers add DWDM capabilities to their fiber networks to equip them to carry higher volumes of data traffic, the functions that Sonet technology previously performed for voice transmission are becoming obsolete.
		DWDM casts its shadow You don't have to look very hard to find evidence of DWDM's increasing penetration-or its effect on the Sonet layer.
		While acknowledging that DWDM is penetrating the metro market as a replacement for Sonet, he says that any wholesale changeover will be a long time coming.
	telephonyonline.com /mag/telecom_dwdm_rising/index.html (2873 words)

	Automate DWDM card tests - Test & Measurement World (Site not responding. Last check: 2007-10-12)
		In these networks, DWDM transmit cards convert electrical signals to optical signals, then amplifiers boost the signals along the network.
		Finding a way to automate DWDM tests can be challenging because of the large number of tests that you must perform.
		When the tests pass, the DWDM channels have enough optical power and the correct wavelength and the network will show minimal crosstalk between adjacent channels, which allows for successful decoding.
	www.reed-electronics.com /tmworld/article/CA189183.html (2129 words)

	Market Report - DWDM Systems Market Study
		DWDM (Dense Wave Division Multiplexing) technology is making headlines in 1997 as telecommunications carriers look for ways to increase their network capacities beyond the limits of today’s TDM fiber optic systems.
		DWDM technology has been in use by long distance companies in recent years to expand the capacity of their trunks by allowing a greater number of signals to be carried on a single fiber.
		The DWDM market is also growing quite rapidly in Europe and Asia and is already being deployed into the next generation of international submarine fiber optic systems to provide gigabit rates across the world’s oceans.
	www.igigroup.com /st/pages/dwdmsys.html (721 words)

	DWDM MSA (Site not responding. Last check: 2007-10-12)
		The DWDM Pluggable Transceiver Multisource Agreement (MSA), initiated by Agilent Technologies, Nortel Networks and Agere Systems establishes a standard that specifies uniformity for DWDM transceiver package outlines, pin function definitions, optical and electrical interfaces and characteristics.
		A standard DWDM transceiver is essential to provide a focal point for the component and system industry to allow development of dense DWDM products and therefore the wide adoption of the DWDM technology.
		Announced in June 2002, the DWDM Pluggable Transceiver MSA specifies all the physical media dependent requirements for implementation in Metro DWDM optical networking systems equipment.
	www.hotplugdwdm.org (213 words)

	DWDM for everyone
		In DWDM installations today, a technician must physically remove the failed card and insert a spare plug-in unit that is pre-set to the required frequency.
		As DWDM channel spacing drops to 50 GHz, the tunable transmitters on those first four-channel cards will begin to support eight wavelength frequencies because the same card can then cover a larger number of wavelengths in its frequency range.
		Consequently, service providers will find DWDM much more affordable and will be able to better cost-justify the expansions of their bandwidth capacity that they so desperately need.
	telephonyonline.com /mag/telecom_dwdm_everyone/index.html (1993 words)

	Wave Division Multiplexing: Dense Wave Division Multiplexing (DWDM)
		Dense Wave Division Multiplexing (DWDM) combines up to 64 wavelengths onto a single fiber.
		DWDM technology uses an ITU standard 100GHz or 200GHz spacing between the wavelengths, arranged in several bands at ~1500-1600nm.
		With DWDM technology, the wavelengths are close together (compared to CWDM), meaning that transponders are generally more complex and expensive than CWDM.
	www.mrv.com /wdm/tech_dwdm.php (99 words)

	IEC: Dense Wavelength Division Multiplexing (DWDM)
		Dense wavelength division multiplexing (DWDM) is a fiber-optic transmission technique that employs light wavelengths to transmit data parallel-by-bit or serial-by-character.
		This tutorial addresses the importance of scalable DWDM systems in enabling service providers to accommodate consumer demand for ever-increasing amounts of bandwidth.
		DWDM is discussed as a crucial component of optical networks that allows the transmission of e-mail, video, multimedia, data, and voice—carried in Internet protocol (IP), asynchronous transfer mode (ATM), and synchronous optical network/synchronous digital hierarchy (SONET/SDH), respectively, over the optical layer.
	www.iec.org /online/tutorials/dwdm (127 words)

	DWDM
		The distances are incredibly long, and DWDM actually simplifies the physics involved in transporting data, such that the optics involved do not need as much amplification and regeneration, and there is less ancillary equipment required for supporting the optical connections over the longer distances.
		As a result, companies are beginning to look at bringing DWDM down to the MAN. Unfortunately, with its relatively short distances, hubbed and meshed traffic patterns, and less need for regeneration or amplification than the long-haul networks, the metropolitan environment does not present a very good business case for DWDM.
		“Rather than turning on DWDM in every single one of their places, which is the traditional long-haul approach, they can turn it up on a site-by-site basis, depending on where the greatest demand is,” said Martinage.
	www.washingtontechnology.com /news/15_9/tech_features/1609-2.html (527 words)

	Guidelines on DWDM Links for Network and Data
		Since DWDM converters are typically designed to be fault tolerant, it is acceptable to use only one DWDM box (in each data center) for the links between each data center.
		However, for the highest availability, it is recommended to use two separate DWDM boxes (in each data center) for the links between each data center.
		If using a single DWDM box for the links between each data center the redundant standby fibre link feature of the DWDM box must be configured.
	docs.hp.com /en/B7660-90014/ch02s05.html (322 words)

	Verizon Business Wholesale : International Partner Solutions : Data : Bandwidth Services : DWDM Services (Site not responding. Last check: 2007-10-12)
		With DWDM (Dense Wave Division Multiplexing) technology, multiple data-streams are transmitted over a fibre-optic medium via a spectrum of colours (or waves) rather than just the single on/off (binary/digital) signalling of fibre-optic transmitters (FOTs).
		These 2.5 and 10 Gbps data streams function much like a virtual dark fibre in that telephony switching equipment of various speeds can be attached to the ends to create a SONET, SDH, or other telephony network.
		If you are an ISP and you are looking for cost-efficient solutions to your capacity crunch, Verizon's DWDM Services give you a virtual fibre network with quick time to market; it may be just the service you are looking for.
	www.verizonbusiness.com /wholesale/ips/data/bandwidth/dwdm (284 words)

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