, Video (Video) and other telecommunications services, broadband technology, so that the trunk (Backbone) network of transmission capacity must also increase as a result. Currently, commercial SDHSTM-16 (2.5Gb / s) system, shortage of capacity in the future will be in danger, so many manufacturers trying to enhance the capacity of SDH transmission systems to 10Gb / s (STM-64), to the SDH transmission system further increase the capacity of 40Gb / s (STM-256), remains to be the breakthrough semiconductor technology. In recent years, the semiconductor lasers, optical amplifiers, optical filters and other optical components technology matures, making DWDM technology boom, DWDM in addition to high-speed TDM transmission to avoid problems caused by the lack of the phenomenon is also to improve the existing fiber and provide a large capacity, diversification of broadband services, network operators can cost-effectively, will enhance the transmission bandwidth to 16,32,64 or even 128 times. Development of these technologies will lead the future trend of the trunk network infrastructure.
High-density WDM (DenseWavelengthDivisionMultiplexing, DWDM) of the indicated structure shown in Figure 1, the transmitter can be combined with n wavelengths of the light signal in the same fiber transmission network of the transmission capacity can be increased substantially.
Figure 1 indicate high-density multi chart
2.DWDM benefits 2.1 Evolution of Power Road to the Optical Network
DWDM technology laid the evolution from the power grid to the optical networks based on the traditional power grid (ElectronicNetworking) can not be directly in the optical layer (OpticalLayer) for multiple (multiplexing), switch (switching), or the routing of grafting ( routing) and other actions, the network node will need to use photoelectric conversion devices convert light signals to electronic signals then signals back to optical signals, this way the overall transmission rate of the use of photoelectric conversion device may be limited, unable to fiber and born with good potential to play an unlimited bandwidth.
To DWDM optical networks as the mechanism of direct signal in the optical layer for the operation to solve the above problem, so to overcome the traditional transmission bottlenecks brought "Virtualfibre" concept, will both make the most efficient fiber use.
2.2 Internet service diversification DWDM and transfer rate (BiteRate) and the Statute (Protocols) nothing to do with that type of service available and nothing to do with the transmission network, for example: a study of transfer rate and the statute completely transparently (Transparent) for DWDM networks can and ATM, IP, SDH and other signals mediated access, providing a variety of services online.
2.3 reduce costs, improve service quality
Optical layer due to the assignment or scheduling signal, compared to traditional scheduling in bandwidth-layer to the more simple and efficient, to reduce expenses. Also in the fiber network was cut off (cablecut) or optical signal failure, the signal in the optical layer protection switch or network routing reply (Restoration) movement, as opposed to traditional in-layer action for recovery of its switching time than short, so that networks availability (availability) increase and improve service quality.
2.4 to enhance the transmission distance and increase the network capacity
Speed of STM-64TDM (TimeDivisionMultiplexing) The biggest problem is the transmission fiber dispersion (Dispersion) is serious, for the transmission of optical signal degradation will have effect, therefore, if using electronic recycling, or other compensation techniques, theoretical STM-64 signal can be transmitted within the G.652 fiber is about 60 km. If eight wavelengths DWDM technology transfer, each wavelength of 2.5Gb / s of the signal, its transmission capacity for 20Gb / s, the transmission distance up to 600 kilometers without electronic regeneration, the need for optical amplifiers .
STM-64 of multiple signals for the tributary (Tributary) in the frequency and format, usually have some restrictions, while DWDM multiplexed virtually unlimited, PDH, ATM, SDH, and IP so that any signal format Jieke input, increasing the flexibility of network transmission. If the next light Drop Multiplexers (OpticalAdd-DropMultiplexer, OADM) and optical transfer machine (OpticalCross-Connect, OXC) in the advent of direct transfer of units of wavelength of light, remove the O / E / O conversion steps, can improve network scheduling efficiency. Users in addressing the growing bandwidth demand and improve network capacity of the program, DWDM technology to provide in a different choice.
3.DWDM related equipment Current DWDM related equipment are the following:
(1) optical amplifiers, (2) DWDM terminals, (3) Light Drop Multiplexers machine (4) optical transfer machines.
Hereby will be the main function of DWDM related equipment described as follows:
3.1 Optical Amplifiers With the optical signal format and bit rate of transparency, operation at 1550nm region were significantly high-gain, high optical output power and low noise figure, optical amplifiers based on different applications of the following three:
Optical amplifier (BoosterAmplifier, BA) Optical pre-amplifier (Pre-Amplifier, PA) Optical line amplifier (LineAmplifier, LA) Present multi-wavelength DWDM systems used in optical amplifiers are erbium-doped fiber amplifier most (Erbium-DopedFiberAmplifier, EDFA) whose main components include a erbium-doped fiber, pump laser (PumpLaser) and DWDM components (for hybrid transmission of optical signal and pump light output). EDFA 1550nm region directly amplified without the use of electronic regenerator can be quite large to provide flat gain wavelength range, which is a single EDFA can provide multiple wavelength channels of gain, has replaced most of the regenerator applications, a long-distance optical fiber Networks components.
3.2DWDM terminal DWDM terminals with optical amplifiers can be used in optical transmission network, the transmitter wavelength light more than acceptable signal input and convert it to meet the ITU-TG.692 fixed-wavelength optical signal by multiple mixed transmitted light amplification optical transmission network, the receiver can receive the signal from the optical transport network, by the optical preamplifier, demultiplexing, and optical filter after the output.
The following two types of DWDM terminals :
(1) open system (OpenSystem): often referred to as switch-frequency (transponder-based) DWDM, SDH and DWDM equipment in there to switch between the frequency, which can be mediated access SDH equipment of different manufacturers.
(2) integrated system (IntegratedSystem): often referred to as passive (passived) DWDM, SDH equipment has an interface with ITU-TG.692 function.
Open systems and integrated systems Comparison of advantages and disadvantages I am a professional editor from China Product, and my work is to promote a free online trade platform. http://www.himfr.com/ contain a great deal of information about rfid transponder , sony wall bracket welcome to visit!
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