Application of WDM Technology in Metropolitan Area Network
Due to the rapid development of informatization, the demand for large-capacity and long-distance bandwidth has increased rapidly, resulting in a rapid increase in traffic in the backbone network, metropolitan area layer and access layer. Therefore, relying on direct fiber connection and bandwidth leasing has begun to fail to meet the needs of industry customers.
By introducing DWDM and CWDM wavelength division technology into the metropolitan area network and access network, the entire network will become a seamless whole, providing support and connection for all different services. The wavelength division technology in the metropolitan area network has great advantages and development potential, and has become an inevitable evolution of the entire communication network to an all-optical network.
Based on existing business needs and facing the future network development, a new type of optical transmission network system is introduced. CWDM and DWDM technologies can make full use of the huge bandwidth resources of optical fiber, greatly increase the system transmission capacity, and reduce transmission costs. Therefore, this technology has been widely used in long-distance and ultra-large capacity transmission of backbone networks.
WDM Technology Principles
WDM is a technology that multiplexes optical signals of different wavelengths into the same optical fiber for transmission. Its basic principle is to use the difference in optical wavelengths to multiplex multiple optical signals at the transmitting end, and then separate these optical signals through a demultiplexer at the receiving end, thereby realizing the parallel transmission of multiple signals.
In the WDM system, the optical signal generated by the light source is first modulated by a modulator, and then multiple optical signals of different wavelengths are combined into one through a multiplexer and sent to the optical fiber for transmission. At the receiving end, the optical signal is separated into optical signals of each wavelength by a demultiplexer, and then restored to the original signal by a demodulator.
Currently, there are two main WDM technologies used in metropolitan area networks: DWDM and CWDM (Coarse Wavelength Division Multiplexing) technology.
Metro DWDM partially inherits the technical characteristics of long-distance backbone network DWDM in terms of system structure, adopts a 16/32 (40) wavelength optical add/drop multiplexing (OADM) system, and has made a lot of improvements in the types of service access and networking flexibility, making it suitable for ring network applications in metropolitan area networks.
CWDM technology takes into account the short transmission distance of the metropolitan area network. It does not need to choose expensive lasers with high wavelength stability and high dispersion tolerance. It generally provides 4/8/16 waves, which has the characteristics of low overall cost and convenient installation.
Typical Applications of WDM Technology in Metropolitan Area Networks
Due to the characteristics of the two technologies, their applications in metropolitan area networks have their own advantages.
The biggest feature of DWDM is that it can provide large-capacity data access and transmission, and the technology is very mature and has been widely used in long-distance backbone networks.
Due to its low cost, simple structure, and flexible and diverse characteristics, CWDM technology is suitable for the construction of metropolitan area networks in some areas. It can be used in the core network of districts in coastal cities and has the opportunity to find its place in the construction of metropolitan area networks in small and medium-sized cities.
At present, metropolitan area network construction tends to adopt DWDM systems, and the WDM equipment in the backbone layer of large urban metropolitan area networks adopts 32 (40) wave metropolitan wavelength division multiplexing (WDM) optical add-drop multiplexing (OADM) equipment.
WDM not only solves the capacity problem, but also stimulates the emergence of a large number of new businesses. In recent years, major technological breakthroughs and market-driven developments have led to the rapid development of wavelength division multiplexing systems. It can be said that the development of multiplexing systems with more than 100 optical wavelengths in WDM systems, especially ultra-large capacity DWDM systems, is another epoch-making milestone in the history of optical fiber communication development.