05-11-2012, 01:06 PM
Dense Wavelength Division Multiplexing (DWDM)
Dense Wavelength.docx (Size: 109.37 KB / Downloads: 26)
Introduction of DWDM
The following discussion provides some background on why dense wavelength division multiplexing (DWDM) is an important innovation in optical networks and what benefits it can provide. We begin with a high-level view of the segments of the global network and the economic forces driving the revolution in fiber optic networks. We then examine the differences between traditional time-division multiplexing (TDM) and wavelength division multiplexing (WDM). Finally, we explore the advantages of this new technology.
Over the last decade, fiber optic cables have been installed by carriers as the backbone of their interoffice networks, becoming the mainstay of the telecommunications infrastructure. Using time division multiplexing (TDM) technology, carriers now routinely transmit information at 2.4 Gbit/s on a single fiber, with some deploying equipment that quadruples that rate to 10 Gbit/sec. The revolution in high bandwidth applications and the explosive growth of the Internet, however, have created capacity demands that exceed traditional TDM limits. As a result, the once seemingly inexhaustible bandwidth promised by the deployment of optical fiber in the 1980s is being exhausted. To meet growing demands for bandwidth, a technology called Dense Wavelength Division Multiplexing (DWDM) has been developed that multiplies the capacity of a single fiber. DWDM systems being deployed today can increase a single fiber’s capacity sixteen fold, to a throughput of 40 Gbit/s. This cutting edge technology when combined with network management systems and add-drop multiplexers enables carriers to adopt optically-based transmission optical networks that will meet the next generation of transmitted bandwidth demand at a significantly lower cost than installing new fiber .
Why DWDM
The today’s life is very fast life for which we have the fast equipment with us for example internet to stimulate the speed of internet we need the different type of technology like TDM and FDM but now we need the most speed hence we have introduced the DWDM which will give us an tremendous speed hence the our objective is to make an brief introduction about the DWDM
From both technical and economic perspectives, the ability to provide potentially unlimited transmission capacity is the most obvious advantage of DWDM technology. The current investment in fiber plant can not only be preserved, but optimized by a factor of at least 32. As demands change, more capacity can
be added, either by simple equipment upgrades or by increasing the number of lambdas on the fiber, without expensive upgrades. Capacity can be obtained for the cost of the equipment, and existing fiber plant investment is retained. Bandwidth aside, DWDM’s most compelling technical advantages can be summarized as follows:
• 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.
Evolution of DWDM
Time-Division Multiplexing
Time-division multiplexing (TDM) was invented as a way of maximizing the amount of voice traffic that could be carried over a medium. In the telephone network before multiplexing was invented, each telephone call required its own physical link. This proved to be an expensive and unsalable solution. Using multiplexing, more than one telephone call could be put on a single link.TDM can be explained by an analogy to highway traffic. To transport all the traffic from four tributaries to another city, you can send all the traffic on one lane, providing the feeding tributaries are fairly serviced and the traffic is synchronized. So, if each of the four feeds puts a car onto the trunk highway every four seconds, then the trunk highway would get a car at the rate of one each second. As long as the speed of all the cars is synchronized, there would be no collision. At the destination the cars can be taken off the highway and fed to the local tributaries by the same synchronous mechanism, in reverse. This is the principle used in synchronous TDM when sending bits over a link. TDM increases the capacity of the transmission link by slicing time into smaller intervals so that the bits from multiple input sources can be carried on the link, effectively increasing the number of bits transmitted per second (see Figure 3.1).
Wavelength Division Multiplexing
WDM increases the carrying capacity of the physical medium (fiber) using a completely different method from TDM. WDM assigns incoming optical signals to specific frequencies of light (wavelengths, or lambdas) within a certain frequency band. This multiplexing closely resembles the way radio stations broadcast on different wavelengths without interfering with each other (see Figure 1-7). Because each channel is transmitted at a different frequency, we can select from them using a tuner. Another way to think about WDM is that each channel is a different color of light; several channels then make up a “rainbow.”
Development of DWDM Technology
Early WDM began in the late 1980s using the two widely spaced wavelengths in the 1310 nm and 1550 nm (or 850 nm and 1310 nm) regions, sometimes called wideband WDM. Figure 2-2 shows an example of this simple form of WDM. Notice that one of the fiber pair is used to transmit and one is used to receive. This is the most efficient arrangement and the one most found in DWDM systems.
The early 1990s saw a second generation of WDM, sometimes called narrowband WDM, in which two to eight channels were used. These channels were now spaced at an interval of about 400 GHz in the 1550-nm window. By the mid-1990s, dense WDM (DWDM) systems were emerging with 16 to 40 channels and spacing from 100 to 200 GHz. By the late 1990s DWDM systems had evolved to the point where they were capable of 64 to 160 parallel channels, densely packed at 50 or even 25 GHz intervals. As Figure 2-3 shows, the progression of the technology can be seen as an increase in the number of wavelengths accompanied by a decrease in the spacing of the wavelengths. Along with increased density of wavelengths, systems also advanced in their flexibility of configuration, through add-drop functions, and management capabilities. Increases in channel density resulting from DWDM technology have had a dramatic impact on the carrying capacity of fiber. In 1995, when the first 10 Gbps systems were demonstrated, the rate of increase in capacity went from a linear multiple of four every four years to fourevery year
The challenges of today’s telecommunication network
To understand the importations of DWDM and optical networking, these capabilities must be discussed in the context of the challenges faced by the telecommunications industry, and in particular, service provider. The forecasts of the presumption that a given individual would only use network band width six month of each hour . these formulas did not factor in the amount of traffic generated by internet access ,faxes , multiple phone lines ,modems’ ,teleconferencing and data and voice transmission . in fact , today many people use the band width equivalent of 180 minutes or more each hour .
Therefore, an enormous amount of band width capacity is required to provide the services demands by consumer .at the transmission speed of one Gbps , one thousand books can be transmitted per second .however today , if one million families decide they want to see video on web site and sample the new emerging video application ,then network transmission rate of terabits are required . with a transmission rate of one Tbps , it is possible to transmit 20 million simultaneous 2-way phone calls or transmit the text form 300 years- worth of daily newspapers per second .
Dense Wavelength.docx (Size: 109.37 KB / Downloads: 26)
Introduction of DWDM
The following discussion provides some background on why dense wavelength division multiplexing (DWDM) is an important innovation in optical networks and what benefits it can provide. We begin with a high-level view of the segments of the global network and the economic forces driving the revolution in fiber optic networks. We then examine the differences between traditional time-division multiplexing (TDM) and wavelength division multiplexing (WDM). Finally, we explore the advantages of this new technology.
Over the last decade, fiber optic cables have been installed by carriers as the backbone of their interoffice networks, becoming the mainstay of the telecommunications infrastructure. Using time division multiplexing (TDM) technology, carriers now routinely transmit information at 2.4 Gbit/s on a single fiber, with some deploying equipment that quadruples that rate to 10 Gbit/sec. The revolution in high bandwidth applications and the explosive growth of the Internet, however, have created capacity demands that exceed traditional TDM limits. As a result, the once seemingly inexhaustible bandwidth promised by the deployment of optical fiber in the 1980s is being exhausted. To meet growing demands for bandwidth, a technology called Dense Wavelength Division Multiplexing (DWDM) has been developed that multiplies the capacity of a single fiber. DWDM systems being deployed today can increase a single fiber’s capacity sixteen fold, to a throughput of 40 Gbit/s. This cutting edge technology when combined with network management systems and add-drop multiplexers enables carriers to adopt optically-based transmission optical networks that will meet the next generation of transmitted bandwidth demand at a significantly lower cost than installing new fiber .
Why DWDM
The today’s life is very fast life for which we have the fast equipment with us for example internet to stimulate the speed of internet we need the different type of technology like TDM and FDM but now we need the most speed hence we have introduced the DWDM which will give us an tremendous speed hence the our objective is to make an brief introduction about the DWDM
From both technical and economic perspectives, the ability to provide potentially unlimited transmission capacity is the most obvious advantage of DWDM technology. The current investment in fiber plant can not only be preserved, but optimized by a factor of at least 32. As demands change, more capacity can
be added, either by simple equipment upgrades or by increasing the number of lambdas on the fiber, without expensive upgrades. Capacity can be obtained for the cost of the equipment, and existing fiber plant investment is retained. Bandwidth aside, DWDM’s most compelling technical advantages can be summarized as follows:
• 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.
Evolution of DWDM
Time-Division Multiplexing
Time-division multiplexing (TDM) was invented as a way of maximizing the amount of voice traffic that could be carried over a medium. In the telephone network before multiplexing was invented, each telephone call required its own physical link. This proved to be an expensive and unsalable solution. Using multiplexing, more than one telephone call could be put on a single link.TDM can be explained by an analogy to highway traffic. To transport all the traffic from four tributaries to another city, you can send all the traffic on one lane, providing the feeding tributaries are fairly serviced and the traffic is synchronized. So, if each of the four feeds puts a car onto the trunk highway every four seconds, then the trunk highway would get a car at the rate of one each second. As long as the speed of all the cars is synchronized, there would be no collision. At the destination the cars can be taken off the highway and fed to the local tributaries by the same synchronous mechanism, in reverse. This is the principle used in synchronous TDM when sending bits over a link. TDM increases the capacity of the transmission link by slicing time into smaller intervals so that the bits from multiple input sources can be carried on the link, effectively increasing the number of bits transmitted per second (see Figure 3.1).
Wavelength Division Multiplexing
WDM increases the carrying capacity of the physical medium (fiber) using a completely different method from TDM. WDM assigns incoming optical signals to specific frequencies of light (wavelengths, or lambdas) within a certain frequency band. This multiplexing closely resembles the way radio stations broadcast on different wavelengths without interfering with each other (see Figure 1-7). Because each channel is transmitted at a different frequency, we can select from them using a tuner. Another way to think about WDM is that each channel is a different color of light; several channels then make up a “rainbow.”
Development of DWDM Technology
Early WDM began in the late 1980s using the two widely spaced wavelengths in the 1310 nm and 1550 nm (or 850 nm and 1310 nm) regions, sometimes called wideband WDM. Figure 2-2 shows an example of this simple form of WDM. Notice that one of the fiber pair is used to transmit and one is used to receive. This is the most efficient arrangement and the one most found in DWDM systems.
The early 1990s saw a second generation of WDM, sometimes called narrowband WDM, in which two to eight channels were used. These channels were now spaced at an interval of about 400 GHz in the 1550-nm window. By the mid-1990s, dense WDM (DWDM) systems were emerging with 16 to 40 channels and spacing from 100 to 200 GHz. By the late 1990s DWDM systems had evolved to the point where they were capable of 64 to 160 parallel channels, densely packed at 50 or even 25 GHz intervals. As Figure 2-3 shows, the progression of the technology can be seen as an increase in the number of wavelengths accompanied by a decrease in the spacing of the wavelengths. Along with increased density of wavelengths, systems also advanced in their flexibility of configuration, through add-drop functions, and management capabilities. Increases in channel density resulting from DWDM technology have had a dramatic impact on the carrying capacity of fiber. In 1995, when the first 10 Gbps systems were demonstrated, the rate of increase in capacity went from a linear multiple of four every four years to fourevery year
The challenges of today’s telecommunication network
To understand the importations of DWDM and optical networking, these capabilities must be discussed in the context of the challenges faced by the telecommunications industry, and in particular, service provider. The forecasts of the presumption that a given individual would only use network band width six month of each hour . these formulas did not factor in the amount of traffic generated by internet access ,faxes , multiple phone lines ,modems’ ,teleconferencing and data and voice transmission . in fact , today many people use the band width equivalent of 180 minutes or more each hour .
Therefore, an enormous amount of band width capacity is required to provide the services demands by consumer .at the transmission speed of one Gbps , one thousand books can be transmitted per second .however today , if one million families decide they want to see video on web site and sample the new emerging video application ,then network transmission rate of terabits are required . with a transmission rate of one Tbps , it is possible to transmit 20 million simultaneous 2-way phone calls or transmit the text form 300 years- worth of daily newspapers per second .