Chapter 3 - Distributed Raman Amplifiers

Abstract

One of the capabilities of Raman amplification is to provide distributed amplification, another is the possibility to provide gain at any wavelength by selecting appropriate pump wavelengths, and the third is the fact that the amplification bandwidth may be broadened simply by adding more pump wavelengths. This chapter describes in detail these applications, as a means to achieve distributed amplification. The term distributed amplification refers to the method of cancellation of the intrinsic fiber loss. This chapter discusses the benefits, challenges, and fundamental designs of distributed Raman amplifiers. The benefits of distributed Raman amplification are highlighted with emphasis on some of the first experimental demonstrations of the advantages including improved noise performance as compared to discrete amplification, upgradeability of existing discretely amplified systems, amplification at any wavelength controlled simply by selecting the appropriate pump wavelength, extended bandwidth achieved by using multiple pumps when compared to amplification using erbium-doped fiber amplifiers (EDFAs), and control of the spectral shape of the gain and the noise figure. The chapter also describes advanced distributed Raman amplifiers that represent solutions to some of the challenges in using distributed Raman amplifiers.