Professional Knowledge

Dense Wavelength Division Multiplexing

2021-09-06
DWDM: Dense Wavelength Division Multiplexing is the ability to combine a group of optical wavelengths and use a single optical fiber for transmission. This 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 fiber in order to utilize the achievable transmission performance (for example, to achieve the minimum degree of dispersion or attenuation). In this way, under a given information transmission capacity, the total number of optical fibers required can be reduced.

The relationship between the communication transmission network and the business has become increasingly complex in the context of a substantial increase in business volume. The original TDM (optical fiber single-wave transmission and time division multiplexing) cannot meet the needs of new technologies. The highest rate of optical fiber single-wave transmission for commercial applications is 40Gbits/s, and it is expensive. TDM technology is difficult to adapt to complex networks and business relationships. The optical fiber multi-wave transmission technology that uses pure optical devices for long-wave dispatch has broken the limit of the processing speed of electronic devices. Based on the SDH technology, the optical fiber transmission capacity has been greatly improved. The current commercial application rate of Dense Lightwave Multiplexing (DWDM) technology (DWDM) technology (also known as OTN technology) has reached 3.2 Tbits/s, which means that the communication network can be smoothly upgraded and evolved.
The first proponent of DWDM technology is Lucent Company, where the text translation is intensive light-wave multiplexing. DWDM technology was proposed in 1991. Specifically, it refers to the ability to combine a group of optical wavelengths with a single optical fiber for transmission. This is a laser technology used to increase the bandwidth on the existing optical fiber backbone network. It can also refer to the tight spectral spacing of multiplexing a single optical fiber carrier in a specific optical fiber to achieve the required performance during transmission. And under certain information transmission, you can also try to reduce the number of optical fibers needed. In recent years, the development of DWDM technology has received extensive attention, and the application of DWDM technology in communications will be more extensive in the future.

The DWDM that the major domestic operators are currently running on the network? Almost all open DWDM systems are used extensively. In fact, integrated DWDM systems have many advantages of their own:
1. The multiplexer and demultiplexer of the integrated DWDM system are used separately at the transmitting end and the receiving end, that is: there is only a multiplexer at the transmitting end, and only a splitter at the receiving end, and at the same time, both the receiving end and the transmitting end are removed. OTU conversion equipment (this part is more expensive)? Therefore, the investment of DWDM system equipment can be saved by more than 60%.
2. The integrated DWDM system uses only passive components (such as multiplexers or demultiplexers) at the receiving and transmitting ends. Telecom operators can place orders directly from device manufacturers, reducing supply links and lower costs, thereby saving equipment costs .
3. The open DWDM network management system is responsible for: OTM (mainly OTU), OADM, OXC, EDFA monitoring, and its equipment investment accounts for about 20% of the total investment of the DWDM system; and the integrated DWDM system does not require OTM equipment. The network management is only responsible for the monitoring of OADM, OXC, and EDFA, and more manufacturers can be introduced to compete, and the network management cost can be reduced by about half compared with the open DWDM network management.
4. Since the multiplexing/demultiplexing equipment of the integrated DWDM system is a passive device, it is convenient to provide multiple services and multi-rate interfaces, as long as the wavelength of the optical transceiver of the business end equipment meets G. 692 standard, which can access any service such as PDH, SDH, POS (IP), ATM, etc., and supports PDH, SDH of various rates such as 8M, 10M, 34M, 100M, 155M, 622M, 1G, 2.5G, 10G, etc. , ATM and IP Ethernet? Avoid the open DWDM system due to OTU, but can only use the purchased DWDM system has determined the optical wavelength (1310nm, 1550nm) and transmission rate SDH, ATM or IP Ethernet equipment? It is impossible to use other interfaces at all.
5. If the laser device modules of optical transmission equipment such as SDH and IP routers are uniformly designed with standard geometric size pins, standardized interfaces, easy maintenance and insertion, and reliable connection. In this way, maintenance personnel can freely replace the laser head with a specific color wavelength according to the wavelength needs of the integrated DWDM system, which provides convenient conditions for the failure maintenance of the laser head, and avoids the drawback of having to replace the entire board by the manufacturer in the past. High maintenance costs.
6. The color wavelength light source is currently only slightly more expensive than the ordinary 1310nm and 1550nm wavelength light sources. For example, the 2.5G rate color wavelength light source is currently more than 3,000 yuan more expensive, but when it is connected to the integrated DWDM system, it can be used The cost of the system is reduced by nearly 10 times, and with the large-scale application of color wavelength light sources, its price will be close to that of ordinary light sources.
7. The integrated DWDM equipment is simple in structure and smaller in size, only about one-fifth of the space occupied by the open DWDM, saving computer room resources.
In summary, the integrated DWDM system should be widely used in a large number of DWDM transmission systems, and gradually replace the dominant position of the open DWDM system. Considering that a large number of optical transmission equipment with common light sources are currently in use on the network, it is recommended to adopt an integrated and open compatible hybrid DWDM to protect the initial investment.
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