Network Infrastructure and Architecture: Designing High-Availability Networks

3

WAVELENGTH-DIVISION MULTIPLEXING

3.1 Introduction

3.2 WDM Technology

3.2.1 WDM Basics

3.2.2 WDM Bandwidth Capacity

3.2.3 Coarse vs. Dense WDM Systems

3.2.4 Future Extensions of DWDM Capacity

3.3 Networking Equipment for WDM

3.3.1 WDM Regenerators

3.3.2 Optical Cross-Connects and Switches

3.3.3 Optical Add–Drop Multiplexers

3.4 WDM Networks

3.4.1 WDM Network Provisioning

3.4.2 Wavelength Blocking

3.4.3 O-E-O Conversion in WDM Networks

3.4.4 WDM Network Protection

3.5 Case Study: WDM Link Design

Key Points

References

3.1 INTRODUCTION

The goal of this chapter is to introduce a powerful optical networking technology, wavelength-division multiplexing (WDM). The basic principle of WDM is simple and was explained briefly in Chapter 1. WDM is a technology that maker it possible to send multiple optical signals, each on a different wavelength, along a single piece of optical fiber. This property caused WDM technology to revolutionize optical networking when it was introduced in the 1990s.

This chapter is structured as follows. First, we discuss the WDM principle of operation, followed by calculations of optical fiber capacity using WDM. Two classes of WDM technology are introduced: dense WDM (DWDM) and coarse WDM (CWDM). DWDM uses several optical wavelengths, requires tight control of optical properties but results in powerful bandwidth capacity. CWDM uses only a few channels. This means that it is much easier to build but has less bandwidth capacity than DWDM.

In the second part of the ...