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Dense Wavelength Division Multiplexing Definition And Feature

I. DWDM is the abbreviation of Dense Wavelength Division Multiplexing, a laser technology used to increase the bandwidth on existing fiber backbone networks. Rather, the technique is to multiplex the tight spectral spacing of individual fiber carriers in a given fiber to take advantage of the achievable transmission performance (eg, to achieve minimal dispersion or attenuation) so that With a given information transmission capacity, the total number of fibers required can be reduced.

Second, Win32 device driver architecture

Third, the machine term: WDM: Wire Digram Manual, line construction manual. This manual specifies the connection and layout of aircraft lines.

(Wavelength Division Multiplexing) is a technology that simultaneously transmits multiple laser beams of different wavelengths on a single fiber using multiple lasers. Each signal is modulated by its data (text, voice, video, etc.) and transmitted within its unique ribbon. WDM can increase the capacity of existing fiber infrastructure of telephone companies and other operators. Manufacturers have introduced WDM systems, also known as DWDM (Dense Wavelength Division Multiplexing) systems. DWDM

It can support more than 150 different wavelengths of light waves for simultaneous transmission, and each beam of light can reach a data transmission rate of up to 10Gb/s. This system can provide data transmission rates of more than 1 Tb/s on a fiber optic cable that is thinner than the hair.

Optical communication is a way in which light carries signals for transmission. In the field of optical communications, people are accustomed to naming by wavelength rather than by frequency. Therefore, the so-called Wavelength Division Multiplexing (WDM) is essentially frequency division multiplexing. WDM carries multiple wavelength (channel) systems on one fiber, and converts one fiber into multiple "virtual" fibers. Of course, each virtual fiber works independently at different wavelengths, which greatly increases the transmission capacity of the fiber. . Due to the economics and effectiveness of WDM system technology, it has become the main means of expanding the current fiber-optic communication network. As a system concept, WDM technology usually has three multiplexing modes, namely wavelength division multiplexing at 1 310 nm and 1 550 nm wavelength, Coarse Wavelength Division Multiplexing (CWDM) and dense wave. DWDM, Dense Wavelength Division Multiplexing.

Two wavelengths

This multiplexing technique used only two wavelengths in the early 1970s: a wavelength of 1310 nm window, a wavelength of 1550 nm window, and single-fiber dual-window transmission using WDM technology, which is the initial use of wavelength division multiplexing. .

Coarse wavelength division multiplexing

After being applied in backbone networks and long-haul networks, WDM technology has also begun to be used in metropolitan area networks, mainly referring to coarse wavelength division multiplexing. CWDM uses a wide window of 1 200~1 700 nm, mainly used in systems with a wavelength of 1 550 nm. Of course, a wavelength division multiplexer with a wavelength of 1 310 nm is also under development. The spacing of adjacent channels of coarse wavelength division multiplexing (large wavelength interval) is generally ≥ 20 nm, and its wavelength is generally 4 waves or 8 waves, and up to 16 waves. When the number of multiplexed channels is 16 or less, since the DFB laser used in the CWDM system does not require cooling, the CWDM system has an advantage over the DWDM system in terms of cost, power consumption requirements, and device size, and the CWDM is more and more widely used. Accepted by the industry. CWDM does not need to choose expensive DWDM multiplexers and "light-emitting" EDFAs, and only requires an inexpensive multi-channel laser transceiver as a relay, so the cost is greatly reduced. Today, many manufacturers have been able to offer commercial CWDM systems with 2 to 8 wavelengths, which are suitable for use in cities where geographic coverage is not particularly large and data services are not very fast.

Dense wavelength division multiplexing

Dense Wavelength Division Multiplexing (DWDM) can carry 8 to 160 wavelengths. With the continuous development of DWDM technology, the upper limit of the wavenumber is still increasing continuously. The interval is generally ≤1.6 nm, which is mainly used for long Distance transmission system. Dispersion compensation techniques are needed in all DWDM systems (overcoming nonlinear distortion in multi-wavelength systems - four-wave mixing). In a 16-wave DWDM system, a conventional dispersion-compensating fiber is generally used for compensation, and in a 40-wave DWDM system, dispersion slope compensation fiber compensation must be used. DWDM can combine and transmit different wavelengths simultaneously in the same fiber. To ensure efficient transmission, one fiber is converted into multiple virtual fibers. With DWDM technology, a single fiber can transmit up to 400 Gbit/s of data traffic. As manufacturers add more channels to each fiber, the transmission speed of terabits per second is just around the corner.

techinque level

In terms of the test level of the transmission capacity of the existing WDM system, the 1.6Tbit/s (160 (10Gbit/s) WDM system of Nortel and other companies has been successful. In the subsequent exhibition, Nortel launched 80 (80Gbit/s WDM) The system has a total capacity of 6.4 Tbit/s. In addition, Lucent has created a world record with a wavelength of up to 1022 using an optical amplifier with an 80 nm spectral width. At the same time, we learned about the indicators of some of the world's leading WDM systems.

At home, the research and development of WDM technology is not only active, but also progresses very rapidly. The Wuhan Institute of Posts and Telecommunications (WRI), Peking University, Tsinghua University, and the Ministry of Posts and Telecommunications conducted transmission experiments or construction test projects. For example, Wuhan Institute of Posts and Telecommunications successfully carried out 16 (2.5 Gbit/s 600 km one-way transmission system in October 1997, and 32 (2.5 Gbit/s WDM) at the '98 International Communication Exhibition in Beijing in October 1998. The transmission system, and a capacity of 40 (10 Gbit / s WDM system also carried out transmission experiments, higher-tech WDM systems are in the process of experimentation.

Huawei, Ericsson, ZTE, and Bonfire have WDM-related layouts. Huawei's WDM global market share has jumped to the top. 100G WDM products have been officially commercialized, and 400G technical verification and experiments have been tested in the laboratory.

Prospects

WDM is a multiplexing technology in the optical domain. The network that forms an optical layer is the "all-optical network" and will be the highest stage of optical communication. Establishing an optical network layer based on WDM and OXC (optical cross-connect) to achieve end-to-end all-optical network connection, and eliminating the bottleneck of photoelectric conversion with a pure "all-optical network" will be the future trend. WDM technology is still based on point-to-point, but point-to-point WDM technology is the first and most important step in all-optical network communication. Its application and practice are for the development of all-optical networks. [1] 

use

DWDM is capable of combining and transmitting different wavelengths simultaneously in the same fiber. To be effective, one fiber is converted into multiple virtual fibers. So, if you plan to reuse eight fiber-optic carriers (OCs), that is, eight signals in one fiber, the transmission capacity will increase from 2.5 Gb/s to 20 Gb/s. Thanks to the DWDM technology, a single fiber can transmit data up to 40Gb/s. As vendors add more channels to each fiber, terabits per second is just around the corner.

technology

Wavelength division multiplexing (WDM) combines two or more optical carrier signals of different wavelengths (carrying various kinds of information) at a transmitting end via a multiplexer (also called a multiplexer) and couples them to light. a technique for transmitting in the same fiber of a line; at the receiving end, a demultiplexer (also called a demultiplexer or demultiplexer) separates optical carriers of various wavelengths, and then is made by an optical receiver. Further processing to restore the original signal. This technique of simultaneously transmitting two or many different wavelength optical signals in the same fiber is called wavelength division multiplexing.

Wave division system

Wave division system

WDM is essentially a frequency division multiplexing FDM technology in the optical domain. Each wavelength path is implemented by frequency domain segmentation, and each wavelength channel occupies a bandwidth of a length of fiber. WDM systems use different wavelengths, that is, specific standard wavelengths. In order to distinguish them from ordinary wavelengths of SDH systems, they are sometimes called color optical interfaces. Optical interfaces called ordinary optical systems are "white optical ports" or "white optical ports." ".

The design of the communication system is different, and the width of the interval between each wavelength is also different. According to the channel spacing, WDM can be subdivided into CWDM (Sparse Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing). The channel spacing of CWDM is 20 nm, and the channel spacing of DWDM is from 0.2 nm to 1.2 nm, so CWDM is called sparse wavelength division multiplexing technology with respect to DWDM.


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