WDM

- Oct 05, 2020-

1. DWDM is the abbreviation of Dense Wavelength Division Multiplexing, which is a laser technology used to increase bandwidth on existing fiber optic backbone networks. More precisely, the technology is to multiplex the tight spectral spacing of a single fiber carrier in a specified optical fiber in order to utilize the achievable transmission performance (for example, to achieve the minimum degree of dispersion or attenuation). Given the information transmission capacity, the total number of optical fibers required can be reduced.

Two, Win32 device driver architecture

3. Locomotive term: WDM: Wire Digram Manual, line construction manual. The manual stipulates the connection and layout of aircraft lines.

Wavelength Division Multiplexing (Wavelength Division Multiplexing) is a technology that uses multiple lasers to simultaneously send multiple lasers of different wavelengths on a single fiber. Each signal is transmitted in its unique color band after data (text, voice, video, etc.) is modulated. WDM can greatly increase the capacity of the existing optical fiber infrastructure of telephone companies and other operators. Manufacturers have introduced WDM systems, also called DWDM (Dense Wavelength Division Multiplexing) systems. DWDM

It can support the simultaneous transmission of more than 150 light waves of different wavelengths, and each light wave can reach a data transmission rate of up to 10Gb/s. This system can provide a data transmission rate of more than 1Tb/s on an optical cable thinner than a hair.

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

Two wavelengths
This multiplexing technology only used two wavelengths in the early 1970s: one wavelength in the 1310 nm window and one wavelength in the 1550 nm window. WDM technology was used to achieve single-fiber dual-window transmission. This was the initial use of wavelength division multiplexing. .

Coarse Wavelength Division Multiplexing
Following the application in backbone networks and long-distance networks, wavelength division multiplexing technology has also begun to be used in metropolitan area networks, mainly referring to coarse wavelength division multiplexing technology. CWDM uses a wide window of 1 200 to 1 700 nm, and is mainly used in systems with a wavelength of 1550 nm. Of course, a wavelength division multiplexer with a wavelength of 1 310 nm is also under development. The distance between adjacent channels of the coarse wavelength division multiplexing (large wavelength interval) device is generally ≥20 nm, and the number of wavelengths is generally 4 or 8 waves, up to 16 waves. When the number of multiplexed channels is 16 or less, because the DFB laser used in the CWDM system does not require cooling, the CWDM system has more advantages than the DWDM system in terms of cost, power consumption requirements and equipment size. CWDM is more and more widely used. Accepted by the industry. CWDM does not need to choose expensive dense wavelength division multiplexers and "optical amplifier" EDFAs, and only needs to use cheap multi-channel laser transceivers as relays, so the cost is greatly reduced. Nowadays, many manufacturers have been able to provide commercial CWDM systems with 2 to 8 wavelengths, which are suitable for use in cities where the geographic area is not particularly large and the development of data services is not very fast.

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

techinque level
As far as the test level of the transmission capacity of the existing WDM system is concerned, the 1.6Tbit/s (160 (10Gbit/s) WDM system of Nortel and other companies has been successful. At a later exhibition, Nortel launched the 80 (80Gbit/s) WDM system. The system has a total capacity of 6.4Tbit/s. In addition, Lucent has created a world record of 1022 wavelengths with an optical amplifier with a spectrum width of 80nm. At the same time, we have learned about the various indicators of the existing WDM systems of some world-renowned companies.

In China, the research and development of WDM technology is not only active, but also progresses very rapidly. The five institutes of Wuhan Research Institute of Posts and Telecommunications (WRI), Peking University, Tsinghua University, and the Ministry of Posts and Telecommunications have successively carried out transmission experiments or construction test projects. For example: Wuhan Research Institute of Posts and Telecommunications successfully carried out a 16(2.5Gbit/s600km unidirectional transmission system in October 1997, and demonstrated a 32(2.5Gbit/s WDM) at the Beijing '98 International Communication Exhibition in October 1998. Transmission system, and a WDM system with a capacity of 40 (10Gbit/s) has also been tested for transmission, and a higher-tech WDM system is being tested.

Huawei, Ericsson, ZTE, Fiberhome and other manufacturers have WDM related layouts, and Huawei's WDM global market share has leapt to the first place. 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 formation of an optical layer network, the "all-optical network", will be the highest stage of optical communication. Establishing an optical network layer based on WDM and OXC (optical cross-connection), realizing the end-to-end all-optical network connection of users, and eliminating the bottleneck of photoelectric conversion with a pure "all-optical network" will be the future trend. WDM technology is still based on a point-to-point approach, but point-to-point WDM technology is the first and most important step of all-optical network communication. Its application and practice contribute to the development of all-optical networks.

use
DWDM can combine and transmit different wavelengths at the same time in the same fiber. To ensure effectiveness, one fiber is converted to multiple virtual fibers. Therefore, if you plan to multiplex 8 optical fiber carriers (OC), that is, transmit 8 signals in a single fiber, the transmission capacity will increase from 2.5 Gb/s to 20 Gb/s. Due to the use of DWDM technology, the data flow that can be transmitted by a single optical fiber is up to 40Gb/s. As manufacturers add more channels to each fiber, the transmission speed of terabits per second is just around the corner.

technology
Wavelength division multiplexing (WDM) is to combine two or more optical carrier signals of different wavelengths (carrying various information) at the transmitting end through a multiplexer (also known as a multiplexer) and couple them to the optical The technology of transmission in the same optical fiber of the line; at the receiving end, the optical carriers of various wavelengths are separated by a demultiplexer (also known as a demultiplexer or demultiplexer), and then the optical receiver performs Further processing to restore the original signal. This technology of simultaneously transmitting two or many optical signals of different wavelengths in the same optical fiber is called wavelength division multiplexing.

WDM is essentially a frequency division multiplexing FDM technology in the optical domain. Each wavelength channel is realized by frequency domain division, and each wavelength channel occupies the bandwidth of a section of fiber. The wavelengths used by the WDM system are all different, that is, the specific standard wavelength. In order to distinguish it from the ordinary wavelength of the SDH system, it is sometimes called the colored optical interface, and the optical interface of the ordinary optical system is called "white optical port" or "white optical port" ".

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

Features
(1) Ultra-large capacity transmission.

Since the multiplexed optical channel rate of the WDM system can be 2.5Gbit/s, 10Gbit/s, etc., and the number of multiplexed optical channels can be 4, 8, 16, 32, or even more, the transmission capacity of the system can reach 300 -400Gbit/s, or even greater.

(2) Save fiber resources.

For a single-wavelength system, one SDH system requires a pair of optical fibers; for a WDM system, no matter how many SDH sub-systems there are, the entire multiplexing system only needs a pair of optical fibers. For example, for 16 2.5Gbit/s systems, a single-wavelength system requires 32 optical fibers, while a WDM system only requires two optical fibers.

(3) Transparent transmission of each channel, smooth upgrade and expansion.

As long as the number of multiplexed channels and equipment is increased, the transmission capacity of the system can be increased to achieve expansion. The multiplexed channels of the WDM system are independent of each other, so each channel can transparently transmit different service signals, such as voice, data and Images, etc., do not interfere with each other, which brings great convenience to users.

(4) Use EDFA to realize ultra-long distance transmission.

EDFA has the advantages of high gain, wide bandwidth, low noise, etc., and its optical amplification range is 1530 (1565nm, but the relatively flat part of its gain curve is 1540 (1560nm), which can almost cover the 1550nm working wavelength range of the WDM system. So. A wide bandwidth EDFA can amplify the multiplexed optical channel signals of the WDM system at the same time to realize the ultra-long distance transmission of the system and avoid the situation that each optical transmission system needs an optical amplifier. WDM system The ultra-long transmission distance can reach hundreds of kilometers while saving a lot of relay equipment and reducing costs.

(5) Improve the reliability of the system.

Since most WDM systems are optoelectronic devices, and the reliability of optoelectronic devices is high, the reliability of the system can also be guaranteed.

(6) It can form an all-optical network.

All-optical network is the development direction of optical fiber transmission network in the future. In the all-optical network, the up and down and cross-connection of various services are realized by scheduling optical signals on the optical path, thus eliminating the bottleneck of electronic devices in E/O conversion. The WDM system can be mixed with OADM and OXC to form an all-optical network with high flexibility, high reliability, and high survivability to meet the development needs of bandwidth transmission networks.

Advantage
A key advantage of DWDM is that its protocol and transmission speed are irrelevant. DWDM-based networks can use IP protocols, ATM, SONET/SDH, and Ethernet protocols to transmit data. The processed data flow is between 100 Mb/s and 2.5 Gb/s. In this way, DWDM-based networks can be in a laser channel. It transmits different types of data traffic at different speeds. From the point of view of QoS (Quality of Service), DWDM-based networks quickly respond to customer bandwidth requirements and protocol changes in a low-cost manner. Science and technology are being updated day by day, and 1600G, 800G and 400G are widely used in national trunk lines, provincial trunk lines and municipal trunk lines. Take 1600G as an example: In theory, if the optical cable is fully equipped, one optical fiber can carry 160 10G services. Greatly improve the optical fiber utilization. Of course, the requirements for optical cables are also very high. The theoretical value and the actual value are different. In actual applications, in order to avoid the failure rate, it is rare to use a hundred-channel service on the same optical fiber.

Architecture
Win32 device driver architecture

status quo
The need to support new businesses and new types of PC peripherals poses new challenges to driver development. The new bus increases the number of devices and the demand for device drivers. The continuous increase of various functions on the device makes the development of the driver more and more complicated. At the same time, fast-response interactive applications require close integration of software and hardware. In 1997, there was further development in the unified Win32 driver model (WDM) for Windows 95 and Windows NT, taking all these factors into consideration. WDM allows the use of a single driver source (x86 binary) to simultaneously support new buses and new devices in Windows 95 and Windows NT.

aims
The key goal of WDM is to simplify the development of drivers by providing a flexible way to reduce and reduce the number and complexity of drivers that must be developed on the basis of realizing support for new hardware. WDM must also provide a common framework for plug-and-play and device power management. WDM is a key component to realize simple support and convenient use of new equipment.

In order to achieve these goals, WDM can only be based on a set of common services provided by the Windows NT I/O subsystem. WDM has improved the functions composed of a set of core extensions to support plug and play, device power management, and rapid response I/O flow. In addition to common platform services and extensions, WDM also implements a modular, hierarchical type of micro-driver structure. The type driver implements the functional interfaces required to support the universal bus, protocol, or device class. The general characteristic of the class driver is to provide the necessary conditions for the standardization of the logical device command settings, protocols, and bus interfaces required for code reuse. WDM's support for standard interfaces reduces the number and complexity of device drivers required by Windows 95 and Windows NT.

Hardware support
The mini-driver allows the extension of the generic class driver to realize the support for a specific device protocol or physical programming interface. For example, a mini-driver can be used to implement an extension to the IEEE 1394 bus-type driver to support a specific host controller programming interface. Mini-drivers are very easy to develop, because they can be implemented by simply extending the general class driver interface functions. Although the mini-driver is easy to design, the advantages of reusing the mini-driver module can also be realized by supporting the standard device programming interface. The USB host controller interface (OpenHCI or UHCI) is an example of this.

The modular WDM system structure and the flexible and unified interface enable the operating system to dynamically configure different device driver modules to support specific devices. The modular WDM system structure and the flexible and unified interface enable the operating system to dynamically configure different driver modules to support specific devices. A typical driver stack is composed of general-purpose devices, protocols, and bus-type drivers connected with a specific protocol and a specific bus mini-driver. For example, the operating system can configure a driver stack to support such a camera, its commands are defined by the image class, and it is issued according to the function control protocol (FCP) class from the IEEE 1394 bus class. This flexibility also makes it easy to support a multi-function device by simply implementing a mini-driver to connect the multi-function hardware with the interfaces of several device classes. Dynamically constructing WDM driver stack is the key to realize plug and play device support.

system applications
WDM services make it possible to implement a fast response model for Windows NT and Windows 95. WDM provides multiple execution priorities including core and non-core threads, IRQ levels, and deferred program calls (DPC). All WDM classes and mini-drivers are executed as privileged threads in the core state (layer 0) (not interrupted by the CPU scheduler). 32 IRQ levels can be used to distinguish the priority of hardware interrupt services. For each interrupt, the DPC is queued to wait until the interrupt-enabled IRQ service routine is completed before execution. DPCs have greatly improved the system's response to interrupts by effectively reducing the time that interrupts are prohibited. For x86-based PC systems using multiprocessors, the interrupt support under Windows NT is based on Intel's multiprocessor specification version 1.4.

software application
For applications that require active multimedia, WDM provides a fast-responsive interface in the core state to process I/O streams. The WDM stream interface is provided through a standard WDM interface. For WDM, a multimedia stream can be processed by one or more software filters and device drivers. In order to accelerate the processing of the I/O stream, the WDM stream can directly access the hardware, avoiding the delay caused by the conversion between the non-core state and the core state, and also saves the intermediate I/O buffer need.

To take full advantage of the advantages provided by WDM, it is recommended that you use plug-and-play compatible power management input, sound, graphics, and storage peripherals using USB and IEEE 1394.

The WDM driver can coexist with the existing Windows NT driver on Windows NT, or it can coexist with the existing Windows 95 driver on Windows 95. Existing Windows NT and Windows 95 drivers will continue to be supported, but the advanced advantages of WDM cannot be used. The extensible WDM class driver provided by Microsoft is the best choice to support new devices. Before starting to develop a new WDM class driver, hardware developers should consult Microsoft to obtain support information for a particular device class. Once possible, use the method of writing the class driver only once, and then using the WDM mini-driver to expand it into a driver for a specific hardware interface.

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