The OTN optical transmission network is a transport network organized at the optical layer, based on wavelength division multiplexing technology, and is the next generation backbone transport network. OTN relies on suggestions made by ITU-T for a new generation of “digital transmission system” and “optical transmission system”, such as G.872, G.709, G.798, among others. OTN addresses issues of traditional WDM networks such as weak wavelength/sub-wavelength scheduling capability, networking capability, and protection ability.
The optical transport network provides solutions from multiple perspectives and in many ways. Based on the existing technology compatibility, due to the extensive application of SDH equipment, MSTP equipment has been developed on the basis of SDH technology to address the processing and transmission of data services, and has been extensively applied in the network, effectively compatible with existing technology, and also meeting the transmission functions of data services. However, as the granularity of data services increases and the demand for more fine-grained processing capabilities, there are two demands for the transport network: one is to provide larger pipelines, the general OTN technology provides a new solution, which solves the problem that the SDH-based VC-12/VC4 cross-particle is too small, the scheduling is complex, and there is no demand to transmit large-granularity service. The other is that business puts forward more detailed processing requirements for the optical transport network, and the industry has also proposed packet transport network solutions.
As the demand for network bandwidth continues to grow, operators and system manufacturers have been continuously considering the improvement of business transmission technology. The evolution of digital transport networks has also progressed from the initial first-generation digital transport network to the present third-generation digital transport network based on OTN products. The first and second generations of transport networks were initially designed to support voice services, although they can also be used to transmit data and image services, the transmission efficiency is not high. In contrast, the third-generation transport network technology supports voice, data, and image services from the design perspective, and can support bandwidth-on-demand allocation, scalable quality of service (QoS), and optical virtual transfer network (OVPN) functions when combined with other protocols.
The optical signal is characterized by wavelength or center wavelength, and the processing of the optical signal can be based on a single wavelength or a wavelength-division multiplexing group. (OTN based on other optical multiplexing technologies such as time-division multiplexing, optical time-division multiplexing, or optical code-division multiplexing remains to be researched.) OTN products can achieve the transmission, multiplexing, routing selection, monitoring, and performance and survival of business signals in the optical domain. OTN can support multiple upper-layer protocols, such as SONET/SDH, ATM, Ethernet, IP, PDH, FibreChannel, GFP, MPLS, OTN virtual interconnect, ODU multiplexing, among others, and is an ideal foundation for future network evolution. An increasing number of operators worldwide are constructing the next-generation transport network based on OTN, and system manufacturers are introducing products with more OTN functions to support the construction of next-generation transport networks.