After more than 40 years, the transmission network has experienced PDH, SDH/MSTP, WDM/OTN, PeOTN technology development and generational innovation.
PDH (Plesiochronous Digital Hierarchy) technology is adopted in the first generation of wired network providing voice services.
The second generation provides Web surfing services and TDM dedicated line, using SDH/MSTP (Multi-Service Transport Platform) technology.
The third generation began to support video services and data center connectivity, using WDM (Wavelength Division Multiplexing)/OTN (Optical Transmission Network) technology.
The fourth-generation 4K HD video and quality dedicated line experience was guaranteed by the PeOTN (Packet Enhanced OTN) technology.
In the early stage of development of the first two generations, voice service, Web access and TDM dedicated line services were represented by SDH/MSTP synchronous digital system technology, supporting Ethernet, ATM/IMA and other interface access. CBR/VBR and other different services could be encapsulated into SDH frames, physically isolating hard pipes and focusing on the bearing of low-speed small particles.
After entering the third generation development stage, with the rapid growth of communication service capacity, especially the video and data center interconnection service, the network bandwidth is accelerated. The optical layer technology represented by WDM technology makes it possible for a single fiber to carry more business. Especially, DWDM (dense wavelength division multiplexing) technology has been widely used in various domestic operational transmission networks, completely solving the problems of transmission distance and bandwidth capacity. Looking at the scale of network construction, 100G has become the mainstream in long-distance trunk lines, while 200G local network and man are developing rapidly.
For video, dedicated line and other integrated services, the underlying transmission network needs to have more flexibility and intelligence, therefore, OTN technology gradually surfaced. OTN is a brand new optical transmission technology system defined by ITU-T G. 872, G. 798, G. 709 and other protocols. It includes the complete architecture of optical layer and electrical layer, and has corresponding management and monitoring mechanism and network survivability mechanism for each layer of network. From the current trend, the domestic OTN has become a standard of transport network, especially in the carrier in the construction of local networks, metropolitan area network, basic is adopted based on cross layer of OTN technology, using the line separating the architecture, the network side and line side, decoupling, improved the flexibility of networking and business ability of rapid opening and deployed.
