本科毕业论文---opticalnetworkofsdhgraduatethesiss论文正文.doc

本科生毕业设计（论文）
Abstract
In recent years, with the development of the information society, the global Internet business showed an explosive growth trend. The implementation of the fiber optical network of SDH is on the basis of the transmission platform of ZTE MP320, it can provide a simulation environment for the entire optic transmission network.
This paper studies the technique of SDH network, describes the basic principle of SDH mapping multiplexing, structure of frame, categories of topology, and researches the methods of protection of the optic network. According to the instruction requirement, an optic transmission network with 9 nodes is set up, the services between two nodes are configured through the network with the costs or minimum resources of the network. The system time clock is configured and choose node D as primary clock. Office wire is completed and choose node D as controller of the network. Multiplexing section protection and path protection is finished. After careful design, realized simulations, performance tests show that the synchronous digital hierarchy network is reasonable, it can be used for practical engineering.

Key words: SDH; networks; optical transmission; STM-N; networking; multiplexing; optical interface

Table of Contents
Chapter 1 Introduction 1
1.1 Background 1
1.2 Characteristics of SDH network 1
1.3 Research objectives and significance 2
Chapter 2 SDH Principles 4
2.1 SDH signal frame structure and multiplexing steps 4
2.1.1 SDH signal frame structure 4
2.1.2 SDH multiplexing step 6
2.2 SDH equipment logic function blocks 5
2.3 The basic network topology 6
2.4 Self-healing network 8
Chapter 3 SDH Network Architectures 10
3.1 A point-to-point SDH link 10
3.2 A SDH Ring Network 11
3.3 Multi-Ring SDH Topology 12
3.4 SDH Ring Protection Mechanisms 13
3.5 The Ring Protection Architectures 13
Chapter 4 Realization of Optic Transmission Network 18
4.1 Network topology 18
4.2 Networking realization 18
4.2.1 Set up the network nodes 19
4.2.2 Installation of the boards in nodes 20
4.3 System Clock configurations 23
4.4 Office wire configurations 26
4.6 Service configuration 27
4.6.1 A to I 2mb/s*10 service configuration 27
4.6.2 The results of services of network 30
4.7 Service protection configuration 32
4.7.1 Service protection from A to B 32
4.7.1 Service protection results 35
4.8 Multiplexing section protection 35
References 39
Acknowledgements 40
Appendix I 41

III
Chapter 1 Introduction
1.1 Background
The SDH is an international standard that is highly popular and used for its high speed data transfer of the telecommunication and digital signals. This synchronous system has been specially designed in order to provide a simple and flexible network infrastructure. This system has brought a considerable amount of change in the telecommunication networks that were based on the optical fibers as far as performance and cost were concerned.
1.2 Characteristics of SDH network
SDH has been able to rapidly develop and this is its own characteristics are inseparable, and its specific features are as follows:
(1) SDH transmission systems in the world to have a unified frame structure, digital transmission standard rate and standard optical interface is network interworking system, and therefore has good lateral compatibility, it is fully compatible with the existing PDH, and accommodates a variety of new traffic signals, the formation of a global unified standard digital transmission system and improve the reliability of the network; (different levels of the code arrangement)
(2) SDH access system flow structure of the payload area of the frame is very regular, and the payload is synchronized with the network , which uses software, a direct high-speed signal can drop out of the low-speed tributary signals to achieve the characteristics of a multiplex overcome PDH plesiochronous multiplexed manner for all the high-speed signal multiplexing gradual decomposition and regeneration process is greatly simplified because the DXC, reducing the back- interface multiplex equipment , improved the service delivery network transparency ;
(3) As a result of the more advanced add-drop multiplexer (ADM), digital cross-connect (DXC), self-healing capabilities and reassembly branch network becomes stronger, with a strong survival. Because SDH frame structure arranged a 5 percent overhead bit signal, it is particularly powerful network management functions , and can be unified into a network management system for automation networks , intelligent, channel utilization and reduce network costs and vascular viability played a positive role;
(4) Due to a variety of SDH network topology, the network that it consists of very flexible, it can enhance network monitoring, operation management and auto-configuration capabilities, optimize network performance, but also to network operation and flexible, safe and reliable, so the network is very complete and diverse;
(5) SDH transmission and switching performance has free combination of function blocks composed through its family of devices, to achieve a variety of different levels and network topology is very flexible;
(6) SDH does not belong to a transmission medium which can be used for twisted pair, coaxial cable, but for the transmission of SDH.
You need to use high data rate optical fiber. This feature indicates, SDH trunk channels suitable for both, but also for regional channels. For example, China's national and provincial trunk cable network is using SDH, and it is also easy to mix compatible with fiber-optic cable network (HFC).
(7) SDH is strictly synchronized to ensure that the entire network is stable and reliable, less error, and easy adjustment and multiplexing.
1.3 Research objectives and significance
Over the years, intelligent optical transmission technology has been of concern for the industry, it hopes to build intelligent optical transmission network to solve the problem several aspects of the existing transmission network exist: first, the traditional fast-growing online network is difficult to adapt the data service with unpredictability, dynamic allocation of network bandwidth. Second, the traditional optical transmission network mainly rely on manual configuration of network connections, time-consuming and difficult to adapt to the modern network expansion needs new business. Third, in order to improve the reliability of bearer services, the traditional optical transport networks need to set aside a large amount of spare capacity, reducing the efficiency of the transport network bandwidth usage.
In addition, the traditional way to protect business networks is relatively simple, the lack of advanced protection, restoration and routing functions. Synchronous Digital Hierarchy (SDH) is widely used worldwide metro backbone network, telecommunication network and WAN.
SDH transmission system is a combination of high-speed large-capacity optical transmission technology and intelligent network technology. It provides convenient and effective data multiplexing and de multiplexing functions, and can reliably transmit data.
Chapter 2 SDH Principles
2.1 SDH signal frame structure and multiplexing steps
2.1.1 SDH signal frame structure
The STM-N (Synchronous Transport Module level-1) is the fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s .Higher levels go up by a factor of 4 at a time: the other currently supported levels are STM-4, STM-16, STM-64 and STM-256. Beyond this we have wavelength-division multiplexing (WDM) commonly used in submarine cabling.
Frame structure
The STM-1 frame is the basic transmission format for SDH (Synchronous Digital Hierarchy). A STM-1 frame has a byte-oriented structure with 9 rows and 270 columns of bytes, for a total of 2,430 bytes (9 rows * 270 columns = 2430 bytes). Each byte corresponds to a 64kbit/s channel.
TOH: Transport Overhead (RSOH + AU4P + MSOH)
MSOH: Multiplex Section Overhead
RSOH: Regeneration Section Overhead
AU4P: AU-4 Pointers
VC4: Virtual Container-4 payload (POH + VC-4 Data)
POH: Path Overhead
Frame characteristics
The STM-1 base frame is structured with the following characteristics:
Length: 270 column × 9 row = 2430 bytes
Byte: 1-byte = 64kbit/s speech channel
Duration (Frame repetition time): 125 μs i.e. 8000 frame/s
Rate (Frame capacity): 2430 × 8 × 8000 = 155.520 Mbit/s
Payload = 2349bytes × 8bits × 8000frames/sec = 150.336 Mbit/s

Fig. 2.1 Structure of SDH frame

SDH frame structure used to carry a block of information , each frame is composed of longitudinal and transverse rows 9 columns 270 × N bytes , each byte containing 8bit, the frame structure is divided into a section overhead (Section Overhead, SOH) area , STM- N payload area and snap- pointer (AU PTR) three regional district.
The above method can be obtained when N is an arbitrary value when the rate 14, 16, 64, 256. As can be seen from Figure 1, the entire frame structure is divided into three regions: the section overhead (SOH) to the information payload area and snap pointer. Section overhead (SOH) is the SDH frame structure in order to ensure the normal transmission of information and additional bytes for network operation, management and maintenance of use, its location in the STM-N frame structure is the first 1 ~ 9 × N columns the first.
The figure describes basic SDH frame consisting of 9 rows and 90 columns. SDH frame is composed of 810 octets (bytes). Transmission is carried out row wise from left to right and from top to bottom. Bits are transmitted serially.
The STS-1 frame of SDH is composed of section overhead, transport overhead, payload overhead and data part. The frame starts with fixed A1/A2 bit pattern of 0xf628 used for bit/octet synchronization. SDH is referred as octet synchronous. The first three columns of SDH frame is referred as transport overhead. The next 87 columns of the frame are referred as Synchronous payload envelope (SPE). Payload overhead is part of SPE.

42
Fig. 2.2 Section overhead

STS-1 data rate is about 51.84 Mbps. Let us examine how this has been achieved. Every SDH frame repeats once every 125 micro-sec. 90 columns in 9 rows and 8000 times per second and 8 bits per octet give us data rate of 51.84 Mbps. STS is the abbreviation of Synchronous Transport Signal. STS-1 is referred as OC-1(Optical Carrier) after scrambling is done on STS-1.
2.1.2 SDH multiplexing step
The multiplexing principles of SDH follow:
Mapping - A process used when tributaries are adapted into Virtual Containers (VCs) by adding justification bits and Path Overhead (POH) information.
Aligning - This process takes place when a pointer is included in a Tributary Unit (TU) or an Administrative Unit (AU), to allow the first byte of the Virtual Container to be located.
Multiplexing - This process is used when multiple lower-order path layer signals are adapted into a higher-order path signal, or when the higher-order path signals are adapted into a Multiplex Section.
Stuffing - SDH has the ability to handle various input tributary rates from PDH. As the tributary signals are multiplexed and aligned, some spare capacity has been designed into the SDH frame to provide enough space for all these various tributary rates. Therefore, at certain points in the multiplexing hierarchy, this space capacity is filled with "fixed stuffing" bits that carry no information, but are required to fill up the particular frame.
Functions to achieve include; reuse the is a low-cost channel layer multiple signals through the code to make it into the high-speed adjustment channel or multiple high-speed channel layer code signals through the process of adjustment to make it into the multiplex layer. Among them, reuse is reuse roadmap, roadmap ITU-T has a variety of provisions, but a national and regional use only one. China's use of SDH signals are multiplexed with the line 10 shown in Figure 2.3.

Fig. 2.3. SDH mapping multiplexing principle

The figure on the previous page illustrates the ITU-T SDH multiplexing structure. The notations in the boxes, such as C-1, VC-3, and AU-4, are explained in the table after the figure.
At the lowest level, containers (C) are input to virtual containers (VC). The purpose of this function is to create a uniform VC payload by using bit-stuffing to bring all inputs to a common bit-rate ready for synchronous multiplexing. Various containers (ranging from VC-11 at 1.728 Mbit/s to VC-4 at 139.264 Mbit/s) are covered by the SDH hierarchy. Next, VCs are aligned into tributary units (TUs), where pointer processing operations are implemented.
These initial functions allow the payload to be multiplexed into TU groups (TUGs). As the figure illustrates, the xN label indicates the multiplexing integer used to multiplex the TUs to the TUGs. The next step is the multiplexing of the TUGs to higher level VCs, and TUG-2 and TUG-3 are multiplexed into VC-3 (ANSI mappings) and VC-4. These VCs are multiplexed with fixed byte-stuffing to form administration units (AUs) which are finally multiplexed into the AU group (AUG). This payload then is multiplexed into the Synchronous Transport Module (STM).
The information structure level SDH multiplexing step is called Synchronous Transport Module using STM-N (Synchronous Transport, N = 14, 16, 64), in fourfold module, the basic module STM-1. Four STM-1 synchronous multiplexing constitute STM-4, 16 个 four STM-1 or STM-4 synchronous multiplexing constitute STM-16, the structure shown in Figure 2.4.

Fig. 2.4 Structure of SDH synchronous multiplexing

SDH transmission network is composed of different types of network elements connected via fiber-optic cables composed of different network element SDH network to complete the transfer function: up / down operations, cross-connect services, such as self-healing network failure.
TM - Terminal Multiplexer Terminal: terminal multiplexer used on the site of the network, such as the two endpoints of a chain which is a dual-port device, shown in Fig. 2.5.

Fig. 2.5 Terminal Multiplexer

ADM - Add / Drop Multiplexer: add / drop multiplexer for SDH transmission network adapter at the site, such as the chain of intermediate nodes, or SDH node on the ring is the most used online, the most important one network element, which is a three-port device, as shown in Figure 2.6.

Fig.2.6 Add/drop multiplexer

REG - regenerative repeater: optical transmission network, there are two regenerative repeater, and a purely optical regenerative repeater, the main power amplifier to extend the optical distance of the optical transmission; other is for pulse regeneration shaping the electric regenerative repeater, mainly through the optical / electrical conversion, sampling the electrical signal, reproduction judgment plastic, electrical / optical conversion, line noise does not ac