Development and Prospect of the hottest optical fi

Development and Prospect of optical fiber communication system technology

Abstract: This paper briefly summarizes and prospects the development trend of some hot technical fields of optical fiber communication system. The main conclusions are as follows: SDH will transform to an integrated low-cost multi service platform; Some new optical Ethernet solutions are gradually having the necessary functions and performance required by public telecommunications, and have become optional technologies for metropolitan multi services, but a series of problems still need to be solved; 40gibt/s system technology has matured, but it will take time for large-scale application; The technology and market of ultra long distance WDM transmission system are mature; Coarse wave division system has a good development prospect in China's metropolitan area; Point to point WDM transmission will move towards automatic switching optical network; EPON and GPON will become the dominant FTTH technology. However, large-scale application still needs to solve the problems of cost, supporting technology and application

key words: optical fiber communication wdmepongpon

1. Introduction

at the beginning of the century, due to the introduction of Luo foam and optical fiber polyurea technology by Professor Huang microwave of Qingdao University of technology, the bursting of China's foam and 3G foam has plunged the world's telecommunications industry into unprecedented difficulties, and optical fiber communication is the first to be hit. Fortunately, the internal demand of telecommunications has not fundamentally changed, people have not played less, nor have they played less. The SMS business is in full swing, the IPTV business is ready to go, the telecommunications business market continues to grow, the annual growth rate of the world's network bandwidth demand is still as high as 50% - 100%, while the annual growth rate of China's trunk line business volume and bandwidth demand in the past few years has exceeded 200%. However, the dilemma caused by the foam has only slowed down the speed of development, and it will never and cannot stop the development process of telecommunications technology and business. After several years of adjustment, the telecommunications industry is beginning to enter the normal track of rational development. The following is a brief summary and outlook of the development trend of optical fiber communication system technology

2. The transformation of SDH to the next-generation integrated low-cost multi service platform

sdh is still the dominant transmission system of telecommunications. However, due to the emergence and development of WDM, the role and role of SDH have changed greatly. On the long-distance trunk line, the role of SDH has been reduced to the client layer of WDM layer, and its role is beginning to shift to the network edge. In view of the complex customer layer signal characteristics at the network edge, SDH must be transformed from pure transmission to a multi service platform integrating transmission and service, that is, a converged multi service node. Its starting point is to make full use of the trusted SDH technology, especially its protection and recovery ability and guaranteed delay performance, and transform it to adapt to multi service applications, support the data intelligence of layer 2 and even layer 3, and form a multi service transmission platform (MSTP) integrating the service layer and transmission layer

in recent years, with the continuous increase of the weight of data services in the network, the SDH multi service platform is gradually evolving and developing from simply supporting the fixed packaging and transparent transmission of data services to the next generation SDH system that more flexibly and effectively supports data services. The latest development is to support the integration of general framing program (GFP), link capacity adjustment scheme (LCAS) and automatic switched optical network (ASON) standards

gfp is a general standard signal adaptation mapping technology that can transparently package various data signals into the existing network. It is simple, flexible, low overhead and high efficiency, which is conducive to the interconnection of equipment from multiple manufacturers, can implement statistical multiplexing of user data, and has QoS mechanism. In addition, by simplifying the processing of any byte block each time, GFP reduces the processing requirements of data link mapping and de mapping. Taking advantage of the low bit error characteristics of modern optical communication, GFP further reduces the implementation complexity, equipment size and cost of the receiver, making GFP particularly suitable for high-speed transmission link applications, such as point-to-point SDH links, wavelength paths in otns, and dark fiber applications

lcas defines a method that can smoothly change the virtual cascade signal bandwidth in transmission, so as to automatically adapt to the effective service bandwidth. Signaling transmission is completed by ordinary SDH element and management system. The biggest advantage of using LCAS is that the effective net load can be automatically mapped to the available VC, which means that the adjustment of bandwidth is continuous, which not only improves the speed of bandwidth allocation and does no harm to the business, but also when the system fails, it can dynamically adjust the system bandwidth without manual intervention, and can significantly improve the network utilization on the premise of ensuring the quality of service

ason can dynamically implement connection establishment and management, so that the network has the function of automatic routing and assignment. If the next generation SDH multi service platform can integrate the above VC cascade, GFP, LCAS and ASON standard functions, and then cooperate with the automatic routing and assignment function of the core intelligent optical network, it can not only greatly enhance its ability to flexibly and effectively support data services, but also expand the intelligence of the core intelligent optical network to the edge of the network, and enhance the intelligent range and efficiency of the network

finally, due to the competitive pressure of optical Ethernet in the metropolitan area, MSTP is forced to continue to improve in reducing equipment costs and improving the flexibility of business provision. One of the important trends is to combine MPLS, so that MSTP and MPLS can rely on each other and expand to the edge of the network together, so as to make full use of a series of advantages of MPLS' flexible cross domain support for data connection

3. Challenges and new development of optical Ethernet

optical Ethernet is a new type of Ethernet technology running on optical fiber, which originates from local area. Structurally, Ethernet is an end-to-end solution that deals with layer 2 switching, traffic engineering and service configuration in all parts of the network, eliminating the format transformation at the network boundary. Secondly, Ethernet has good scalability. By changing the traffic policy parameters at the edge of the network, you can quickly and gradually provide the required bandwidth with 1mbit/s bandwidth particles, from 10mbit/s, 100mbit/s, 1gbit/s to 10gbit/s. In terms of management, because the same system can be applied to all levels of the network, network management can be greatly simplified and new businesses can be expanded faster

in general, Ethernet multi service platform is most suitable for network applications where ip/Ethernet traffic is absolutely dominant. It can also be used as an independent IP Metro application in small and medium-sized cities with large ip/Ethernet traffic, or as an IP Metro convergence and access layer application in large and medium-sized cities with large ip/Ethernet traffic. The core is high-end routers. Some improved new optical ethers are gradually applied to metropolitan multi service platforms

however, historically, Ethernet originated from the local area, so there is no need to consider QoS issues. When trying to extend its application to public telecommunications, it needs to provide user specific QoS and service level contract (SLA) mechanisms. At present, traditional Ethernet has no reliable mechanism to ensure end-to-end jitter and delay performance, and it is difficult to provide the full range of standard QoS assignment capabilities required by real-time services and the billing and statistical capabilities necessary for multi-user shared nodes and networks. Secondly, Ethernet was originally designed for internal applications of local users, lacking security mechanisms. When it is extended to man and WAN, new and more reliable security mechanisms need to be developed. Third, the oam&p capability of Ethernet from local environment is very weak. In public telecommunications, it is necessary to effectively operate and maintain large-scale geographically dispersed networks, which requires strong oam&p capabilities, network level management capabilities and vision, and even business profit models. Fourth, the optical port of the traditional Ethernet switch is directly connected in a point-to-point manner, eliminating the transmission equipment, and does not have the built-in strong fault location ability and complete performance monitoring ability, making it difficult to diagnose and repair the faults in the Ethernet, especially the complex ones. Traditional Ethernet is mainly protected by spanning tree (STP) or fast spanning tree (RSTP), which takes at least a few seconds to converge, and it is difficult to transmit carrier level voice data services. Fifthly, the cost of optical fiber line in Ethernet increases rapidly with the expansion of network scale and the increase of the number of nodes. Whether its network cost is cost-effective for complex large-scale carrier grade networks is still unknown. In short, only after the above major problems are properly solved, can Ethernet be used as a real multi service platform in large-scale public telecommunications environment to provide all kinds of services at the carrier level

recently, optical Ethernet has developed rapidly. Some of the latest technical solutions have solved or partially solved some of the above problems. The traditional Ethernet technology has been greatly improved. It has been able to provide a variety of services, has certain QoS capabilities and management capabilities, and has high survivability. Many technologies have been able to provide 50ms of fast protection switching time, and some technologies also use digital wrappers, Forward error correction (FEC) and synchronization technology are used to improve the system performance and extend the transmission distance. In short, some new optical Ethernet technologies are gradually having the necessary functions and performance required by public telecommunications. In addition to the familiar expansion and enhancement technologies of traditional Ethernet technology, such as Q in Q (svlan), various standardization organizations and manufacturers have developed many new optical Ethernet technologies and their quality improvement and assurance standards, such as elastic packet ring (RPR), multi service ring (MSR), MAC in MAC packaging, virtual private local area service (VPLS), etc., which have their own characteristics. The following is a brief introduction to the two most typical new optical Ethernet technologies, MAC in MAC package and VPLS

the so-called MAC in MAC encapsulation is to encapsulate the user's Ethernet data frame into an operator's Ethernet frame header to form two MAC addresses. Among them, the user's MAC address is stored in the operator's Ethernet frame. The core does not know the user's MAC address, and only forwards traffic according to the operator's MAC address. It can be seen that the MAC in MAC encapsulation method completely shields the user side information (including MAC address, user VLAN and spanning tree), isolates the core, and reduces the pressure of user MAC address on the core forwarding; It improves network scalability, network security and business scalability. Secondly, because MAC in MAC adopts two-layer packaging technology, there is no need for complex signaling mechanism, and the equipment cost, construction cost and operation and maintenance cost are low. Finally, the MAC in MAC encapsulation method is adopted, which allows the lower part to access VLAN or svlan, and the upper part to interweave with VPLS or other VPN services, with strong flexibility

vpls is a multi-point interconnected layer-2 VPN technology further developed on the basis of point-to-point MPLS. From the perspective of users, it seems that all sites are connected to a private LAN. From the perspective of service providers, ip/mpls infrastructure can be reused to provide a variety of services. This technology is based on MPLS and independent of the specific physical topology. It can use the traffic engineering of MPLS to optimize the resource allocation; VPLS uses FRR to replace STP and RSTP protection of Ethernet, and can realize 50ms protection switching; VPLS also supports 2/3/4 layers of Extensible Access Control List (ACL) capabilities and per user ACL control, providing a more secure control and policy mechanism; VPLS has good layer-2 convergence capability, and the number of users supported breaks through the limit of 4096 vlanids of traditional Ethernet; VPLS provides hierarchical VPLS (h-vpls), which improves scalability; VPLS can distinguish and ensure different service flows in each user, with simple network service configuration and fast service provision; VPLS also has a clear boundary between business providers and user sites, which is easy to manage. Of course, the acquisition of the above features is not free. Because VPLS uses three-layer protocol to establish signaling, the equipment cost is high and the operation and maintenance is complex, which partially offsets the low-cost advantage of Ethernet

it can be expected that with the increasing volume of ip/Ethernet services in the network and the continuous emergence of new solutions based on Ethernet technology, optical Ethernet multi service platform will expand, challenge and apply in the metropolitan area