1、 OTNIn recent years,the services carried by communication networks have undergone tremendous changes.Data services developed rapidly,especially broadband services,such as IPTV and video development.The data service puts forward new requirements to the transmission network.undergo v.经历，经受tremendous a
2、.极大的，巨大的，惊人的video n.视频，录像put forward 提出，拿出Transmission networks must provide high bandwidth to accommodate this growth.More importantly,it requires a transport network that can be quickly and flexibly scheduled to meet the needs of the service.Currently the main transmission network is using SDH and
3、 WDM technology,but they both have some limitations.accommodate v.容纳，适应flexible a.灵活的，有弹性的schedule v.安排，预定，调度complete v.完成，使完满maintenance n.维护，维修limitation n.限制，极限SDH technology emphasis on electrical-layer service,it has flexible scheduling,management and protection mechanism and perfect OAM functi
4、on.The traditional SDH transmission network has the service scheduling capability of small particle and limited transmission capacity.It cannot transmit efficiently broadband service of large particle.WDM technology based on optical layer has the advantage to provide high capacity of transmission du
5、e to its transmission characteristics of multi-wavelength channel.emphasis n.重点，强调mechanism n.机制，原理particle n.颗粒，粒子multi-wavelength 多波长However,the current WDM networks mainly are applied in point to point mode,lacking of effective network maintenance and management tool.Optical scheduling system(suc
6、h as ROADM)can achieve the scheduling and protection ability similar to SDH,but it is difficult to be applied to a wide range of networks due to the limitation of physical layer and wavelength.effective a.有效的achieve v.取得，获得OTN technology has both of the advantages of traditional SDH and WDM.OTN adop
7、ts WDM technology in optical layer,which can realize the transmission of large particles.OTN uses asynchronous mapping and multiplexing at the electrical layer to support ODUk(k=1,2,3,4,flex)crossing-connection particles.Compared with SDH VC-12/VC-4 scheduling particles,the transmission particles of
8、 OTN multiplexing,crossover and configuration are significantly larger,which can significantly improve the adaptability and transmission efficiency of high-bandwidth data customer services.adopt v.采取，接受asynchronous a.异步的，不同时的mapping n.映射，映像multiplexing 多路复用，多工configuration n.配置，结构adaptability n.适应性，
9、适应力The OTN technology includes a complete system structure of optical layer and electrical layer,each layer has a corresponding mechanism of network management,monitoring and survival.The OTN technology can provide powerful OAM capabilities,and enables up to six tandem connection monitoring(TCM)capa
10、bilities,providing advanced performance and fault monitoring.structure n.结构，构造corresponding a.相当的，相应的tandem a.串联的fault n.故障，缺点The OTN equipments based on cross-functional ODUk can complete circuit switching particles from the SDH-155M to 2.5G/10G/40G,realizing flexible scheduling and protection to l
11、arge-particles services.The OTN equipments can also introduce ASON-based intelligent control plane,improving the flexibility and survivability of network configuration.cross-functional a.交叉功能的intelligent a.智能的，聪明的survivability n.生存性，生存能力The OTN equipment shall have the functions of customer interfac
12、e,interface adapter and line interface processing.There are several forms of OTN equipment,such as OTN terminal multiplexer,OTN electrical-crossing equipment,and OTN photoelectric hybrid-crossing equipment.adapter n.适配器，接合器photoelectric a.光电的hybrid a.混合的，杂种的OTN Terminal Multiplexer is the WDM equipm
13、ent that supports the interfaces of OTN,which include the line interface and tributary interface(also called services interface or inter-domain network interface).Performance and fault monitoring of end-to-end wavelength path can be realized.The current mainstream manufacturers of WDM system have ba
14、sically adopted OTN structure,and support OTN interface in G.709 standard,so they are all OTN terminal multiplexers.tributary a.附属的，辅助的mainstream n.主流，主要倾向Similar to the existing SDH cross-connection equipment,OTN electric-crossing equipment improves the crossing function of circuit ODUk level,provi
15、ding flexible circuit scheduling and protection for OTN network.OTN electric-cross devices can exist independently,similar to the SDH DXC equipments,providing a variety of external interfaces and OTUk interfaces.They can also be integrated with the OTN terminal multiplexer to provide optical multipl
16、exing and optical transmission section function supporting WDM transmission.external a.外部的，外用的flexible a.灵活的protection n.保护Electrical-crossing equipment of OTN can combine with OCh crossing equipment(ROADM or PXC)to provide scheduling function of ODUk electrical layer and OCh optical layer.Wave-leve
17、l services span OCh directly,and other services that need to be scheduled must cross over ODUk.The combination of both can complement each other,but also avoid their weaknesses.This large-capacity scheduling equipment is photoelectric hybrid cross of OTN equipment.span v.跨越，持续complement v.补充，补足Typic
18、al equipment of this type is OSN6800 produced by Huawei,which supports OCh-crossing based on ROADM and ODU1/GE crossing.ODU1 crossing capacity is 320G and supports ASON control plane.Other manufacturers,such as ZTE,are developing similar products.According to the different existence forms of OTN equ
19、ipments,there are also different application methods of OTN in network construction,such as the whole OTN of WDM systems,OTN crossing-device applications in Long-distance backbone and OTN crossing-device applications in MAN.The introduction of OTN interfaces in WDM system can complete performance an
20、d fault monitoring for end to end wavelength path.OTN can realize the transparent transmission of all kinds of client signals,which is the prerequisite for the router to use the 10GE interface.The OTN interface is introduced gradually into WDM system,preparing for the introduction of large-capacity
21、equipment of OTN in the future.transparent a.透明的，显然的prerequisite n.先决条件With the development of long-distance IP network,IP traffic surges greatly,and the long-distance backbone core node is facing increasing volume of services.And in order to make more effective use of IP network resources,improve t
22、he utilization rate of relay circuit or network operation quality,it is necessary to use large capacity OTN crossover equipment in the long-distance backbone network.surge v.汹涌，起大浪utilization n.利用，使用complicated a.难懂的，复杂的The use of large-capacity OTN equipment can realize the rapid opening of the wav
23、elength path of large particles and improve the service response capability.After the ASON control plane loaded,a variety of protection and recovery methods based on ASON can be provided to improve the reliability of the backbone transmission network.The application of OTN in MAN is more complicated
24、,and the corresponding technology is more competitive.In order to improve fiber utilization,OADM/ROADM based on wavelength level particle scheduling is an inevitable choice for WDM system construction in MAN construction.At present,the main domestic and foreign runners are very concerned about the development and application of OTN technology,and most of them have realized the OTN transmission interface function in WDM.competitive a.竞争的，比赛的inevitable a.必然的，不可避免的
