Optical Networks: A Practical Perspective, Second Edition
The authoritative source for information on optical networking technologies and techniques.
TABLE OF CONTENTS Optical Networks: A Practical Perspective, Second Edition
Chapter 8: WDM Network Design
Overview
In the previous chapter, we Learned that the optical layer provides high-speed circuit-switched connections, or lightpaths, between pairs of higher-layer equipment such as SONET/SDH muxes, IP routers, and ATM switches. The optical layer realizes these lightpaths over the physical fiber using elements such as optical line terminals (OLTs), optical add/drop multiplexers (OADMs), and optical crossconnects (OXCs). We called a network using such lightpaths a wavelength-routing network. In this chapter, our goal is to study how to design a wavelength-routing network. This involves studying not only how to design the optical layer but also how the higher-layer SONET or IP network is to be designed because the design of the two layers is closely coupled. We illustrate with an example.
In Figure 8.1(a), there are three nodes labeled A, B, and C, connected by WDM fiber links. For simplicity, assume the traffic generated is in the form of IP packets from routers located at these nodes. Similar examples hold if the higher layer consists of SONET/SDH muxes or ATM switches. For concreteness, also assume that all router interfaces operate at 10 Gb/s, which is also the transmission capacity on each wavelength on the WDM links. Now suppose, based on estimates of the IP packet traffic, 50 Gb/s of capacity is required between all three pairs of routers: A-B, B-C, and A-C. The network can be designed to handle this traffic in two ways.
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No optical add/drop: In the first method, we set up 10 wavelengths on...
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