The way of using light to transmit information can be said to have a long history.
The modern “Beacon Tower” has allowed people to experience the convenience of transmitting information through light. However, this primitive optical communication method is relatively backward, limited by the transmission distance visible to the naked eye, and the reliability is not high. With the development needs of social information transmission, the birth of modern optical communication has been further promoted.
Start modern optical communication technology
In 1800, Alexander Graham Bell invented the “optical telephone.”
In 1966, the British-Chinese Gao Kun proposed the theory of optical fiber transmission, but at that time the optical fiber loss was as high as 1000dB/km.
In 1970, the research and development of quartz fiber and semiconductor laser technology reduced the fiber loss to20dB/km, and the laser intensity is high, the reliability is strong.
In 1976, the continued development of optical fiber technology reduced the loss by 0.47dB/km, which meant that the loss of the transmission medium had been solved, which promoted the vigorous development of optical transmission technology.
Review the development history of the transmission network
The transmission network has gone through more than forty years. In summary, it has experienced PDH, SDH/MSTP,
The technological development and generational innovation of WDM/OTN and PeOTN.
The first generation of wired networks to provide voice services adopted PDH (Plesiochronous Digital Hierarchy) technology.
The second generation provides Web access services and TDM dedicated lines, using SD (Synchronous Digital Hierarchy)/MSTP (Multi-Service Transport Platform) technology.
The third generation started to support the interconnection of video services and data centers, using WDM (Wavelength Division Multiplexing, Wavelength Division Multiplexing)/OTN (Optical Transmission Network, Optical Transmission Network) technology.
The fourth generation guarantees 4K high-definition video and quality private line experience, using PeOTN (Packet enhancedOTN, packet enhanced OTN) technology.
In the early development stage of the first two generations, for voice services, Web Internet access and TDM private line services, represented by SDH/MSTP synchronous digital system technology, it supports multiple interfaces such as Ethernet, ATM/IMA, etc., and can connect different CBR/VBR. Encapsulate services into SDH frames, physically isolate hard pipes, and focus on low-speed and small-particle services
After entering the third-generation development stage, with the rapid growth of communication service capacity, especially the video and data center interconnection services, the network bandwidth has been accelerated. The optical layer technology represented by WDM technology makes it possible for one fiber to carry more services. In particular, DWDM (Dense Wavelength Division Multiplexing) technology has been widely used in major domestic operating transmission networks, completely solving the problem of transmission. The issue of distance and bandwidth capacity. Looking at the scale of network construction, 80x100G has become the mainstream on long-distance trunk lines, and 80x200G local networks and metropolitan area networks have developed rapidly.
For the carrying of integrated services such as video and dedicated lines, the underlying transport network requires more flexibility and intelligence. Therefore, OTN technology gradually emerges. OTN is a brand-new optical transmission technology system defined by ITU-T G.872, G.798, G.709 and other protocols. It includes a complete system structure of optical layer and electrical layer, and has corresponding networks for each layer. Management monitoring mechanism and network survivability mechanism. Judging from the current domestic network construction trends, OTN has become the standard for transmission networks, especially in the construction of operators’ local networks and metropolitan area networks. OTN technology based on electrical layer crossover is basically adopted, and the branch line separation architecture is used. , To achieve the decoupling of the network side and the line side, greatly improving the flexibility of networking and the ability to quickly open and deploy services.
Business-oriented bearer network transformation
The further acceleration of digital transformation in all areas of the social economy has brought about the parallel development of the entire ICT industry and the digital economy, and has promoted and triggered profound changes in the industry. With the influx of a large number of innovative enterprises in vertical industries, traditional industries and operating models and business models are constantly being reconstructed, including: finance, government affairs, medical care, education, industry and other fields. Facing the increasing demand for high-quality and differentiated business connections, PeOTN technology has gradually begun to be widely used.
·The L0 and L1 layers provide rigid “hard” pipes represented by wavelength λ and sub-channel ODUk. Large bandwidth and low delay are its main advantages.
·The L2 layer can provide a flexible “soft” pipe. The bandwidth of the pipe is fully matched with the service and changes with the change of service traffic. Flexibility and on-demand are its main advantages.
Integrating the advantages of SDH/MSTP/MPLS-TP for carrying small-particle services, forming a L0+L1+L2 transport network solution, building a multi-service transport platform PeOTN, creating a comprehensive carrying capacity with multiple capabilities in one network. In 2009, ITU-T expanded the transmission capabilities of OTN to support diversified services and officially included PeOTN into the standard.
In recent years, global operators have made efforts in the government-enterprise private line market. The three major domestic operators are actively developing OTN government-enterprise private network construction. Provincial companies have also invested heavily. So far, more than 30 provincial company operators have opened OTN. High-quality private network, and released high-value private line products based on PeOTN, to promote the optical transport network from “basic resource network” to “business bearer network.”
Post time: Nov-04-2021