Chapter 10 - Raman Fiber Amplifiers

10.1  INTRODUCTION

In Chapter 9 we discussed erbium-doped fiber amplifiers, which are the most important
optical amplifiers. Since the EDFAs work on the principle of population inversion
between energy levels of the erbium ion, the band ofwavelengths that can be amplified
by an EDFA is restricted. Current EDFAs operating in the C-band (1530 to 1565 nm)
and the L-band (1565 to 1625 nm) are available commercially. Some EDFA designs
operating in the S-band (1460 to 1530 nm) are also becoming available. At other
bands, EDFAs cannot operate and one has to look for other amplifiers based on other
dopants (instead of erbium), other materials (semiconductor optical amplifiers), or
other effects. Raman fiber amplifiers (RFAs) are amplifiers falling in the last category.
In these amplifiers one uses the phenomenon of Raman scattering to amplify optical
signals. The attractive features of RFAs are that they can be made to work in any
wavelength band simply by choosing appropriate pump wavelengths, and they have
a large bandwidth. Apart from this, the link fiber can itself be used as the amplifier,
and thus the signal gets amplified as it covers the distance along the communication
link itself. Such amplifiers are also referred to as distributed amplifiers. RFAs have
attracted considerable attention, and in this chapter we deal with the basic operating
characteristics of RFAs.

Buy this book on Amazon.com

<< Previous Excerpt | View Book Details | Next Excerpt >>