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For more information about Wiley products, visit our web site at www. ISBN alk. Optical communications. K To connect to the outside world, these applications typically used the public switched telephone network PSTN , which consists of twisted-pair cop- per wire links that run from customer premises to local telecommunication switch- ing distribution centers.
In this scenario, telephone companies concentrated on building high-capacity networks up to a local distribution point. This situation changed with the advent of powerful personal computers, which cre- ated a demand for new bandwidth-hungry applications and services, each of which could consume several megabits per second. In addition to large usage demands, the corresponding traffic patterns tend to be bursty and unpredictable in nature, and the connection times became much longer than in a PSTN.
This required a new look at the capabilities of the access network, which encompasses the connections that extend from a local switching facility to individual businesses, organizations, and homes. This book presents fundamental passive optical network PON concepts needed to understand, design, and build high-capacity links for access networks.
This book provides the basic material for an introductory senior-level course on the principles and applications of passive optical network technology. It also will serve well as a working reference for practicing engineers and managers dealing with FTTP network design, implementation, installation, testing, and maintenance. Since modern communication networks make extensive use of acronyms, a list of the most common ones is given at the end of the book. A number of the homework problems can be expanded to serve as student projects.
Simulation tools are being used extensively for modeling the behavior of local, metro, and long-haul networks. These tools also can be useful in the physical-layer design of FTTP networks. The book Web site gives an example application note of such a tool and related applications from RSoft Design Group. In addition, there is a link to the company Web site www.
In addition, I am greatly indebted to the numerous people with whom I had many discussions and who supplied me with photos and other material. It was truly a pleasure to work with them. Telephone companies have spent large sums of money to build out such networks up to a local distribution point.
The cable system that interconnects the user sites and the huge network beyond a local telecommunication distribution point such as a telephone switching station is called the access network. The cost of the large-capacity long-haul networks, which requires the installation of expensive sophisticated switching equipment, is spread out over a large number of users, so the relative cost per service subscriber is low.
Initially, end customers used only telephones, fax machines, or dial-up modems, for which inexpensive copper-based twisted-wire links from their premises to the out- side distribution networks were sufficient. This scenario changed with the advent of powerful personal computers, which created a demand for new bandwidth-hungry applications and services, each running at rates of several megabits per second Mbps.
Among these high-rate applications are video on demand, streaming media, virtual private circuits, high-resolution image transfers, and online entertainment in addition to traditional phone, data, and fax services.
These new demands drove the need to replace low-capacity copper access links with higher-capacity connections.
Several competing broadband wireline and wireless telecommunication technologies are addressing the demand for faster access links. In this chapter we give an overview of access network concepts, terms, and in- terfaces in Section 1. Next, in Section 1. Section 1. In subse- quent chapters we describe the fundamental concepts and applications of various PON types that are being used and considered for access networks.
An architecture is basically a set of rules and conventions by which something is built. Thus, in telecommunication systems the network architecture describes the general physical arrangement and operational characteristics of communicating equipment together with a common set of com- munication protocols.
A protocol is a set of rules and conventions that governs the generation, formatting, control, exchange, and interpretation of information that is transmitted through a telecommunication network or that is stored in a database. A traditional approach to setting up a protocol is to subdivide it into a number of individual pieces of manageable and comprehensible size. The result is a layered structure of services, which is referred to as a protocol stack. In this scheme each layer is responsible for providing a set of functions or capabilities to the layer above it by using the functions or capabilities of the layer below.
As shown in Figure 1. An increasingly larger number of functions are provided when moving up the protocol stack, and the level of functional abstraction increases. The lower layers govern the communication facilities, which deal with the physical connections, data-link con- trol, and routing and relaying functions that support the actual transmission of data.
The upper layers support user applications by structuring and organizing data for the needs of the user. In actual applications some of the layers may be omitted and other layers can be subdivided into further sublayers. Thus, the layering mechanism should be viewed as a framework for discussions of implementation, not as an absolute authority.
For PON discussions we are concerned primarily with the lower three levels. General structure and functions of the seven-layer OSI reference model. A wide area network WAN spans a large geographical area. The links can range from connections between switching facilities in neighboring cities to long- haul terrestrial or undersea transmission lines running across a country or between countries.
WANs are owned and operated by either private enterprises or by telecom- munication service providers. Invariably, many companies own the various segments of a WAN link from one distant point to another. This could range from interconnections between buildings covering sev- eral blocks within a city or could encompass an entire city and the metropolitan area surrounding it. There is also some means of interconnecting the MAN resources with communication entities located in both WANs and local area networks.
MANs are owned and operated by many organizations. They commonly are referred to as metro networks. A local area network LAN interconnects users in a localized area such as a room, a department, a building, an office or factory complex, or a campus. Here the word campus refers to any group of buildings that are within reasonable walking dis- tance of each other.
For example, it could be the collocated buildings of a corpora- tion, a large medical facility, or a university complex. LANs usually are owned, used, and operated privately by a single organization.
An access network encompasses connections that extend from a central com- munication switching facility called the central office; see Section 1. In the other transmission direction, access networks allow carriers to provide voice, data, video, and other services to subscribers.
Such access networks typically are owned by service providers. Access networks thus enable users in homes, businesses, and other enterprises to have connections to global information transport networks. The main drive behind new access technology devel- opments is to transition from slow traditional telephone lines to large-capacity links to allow users to have high-speed connections to outside networks.
When a network is owned and deployed by a private enterprise, it is referred to as an enterprise network. For a monthly fee, the networks owned by the telecom- munication carriers provide services such as leased lines or real-time telephone con- nections to other users and to enterprises at large. Such networks are referred to as public networks. A communication switching facility in a public network is called a central office CO or a point of presence POP. A CO may be located on a metro ring or on a link running to the core metro network.
It houses a series of large complex switches that establish temporary connections for the duration of a requested connection time between subscriber lines which terminate at the switch.
The CO can serve on the order of thousands of subscribers. A long-haul network interconnects various cities or geo- graphical regions and spans hundreds to thousands of kilometers between cen- tral offices.
Definitions of some terms used in describing a public network. Thus, a backbone handles internetwork traffic, that is, traffic that originates in one segment and is trans- mitted to another segment.
A metropolitan typically abbreviated metro net- work connects groups of central offices within a city or geographical region. The distances between central offices for this type of network range from a few to several tens of kilometers.
The access network is the topic of interest for PON applications. The following are some terms used to describe equipment locations and cable types within this network segment, as illustrated in Figure 1.
Some terms used to describe equipment locations and cable types within a PON. The term local convergence point LCP refers to access telecommunication assets located in a neighborhood or business park. These assets serve many subscribers and usually consist of an indoor or outdoor cabinet or enclosure that houses optical devices or electronic equipment.
The network access point NAP or access terminal is located close to subscribers in a neighborhood, business park, or other campus. The distribution cables originate at the LCP and connect to many network access points. A network interface unit NIU located at the customer site enables the user to connect to the network.
As shown in later chapters, this unit may have various names, depending on the technology used for the access network. Simplified access network. Note that the term mile is used merely to denote a relatively short distance and does not mean exactly 1 mile.
FTTX concepts and applications
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FTTX Concepts and Applications