isation-Channel-Interleaved CS-RZ Transmission at 40 Gbit/s with 0.8 bit- 7 s-7 Hz Spectral Efficiency, Electron. Lett. 38(8):381-382. Zimmerman, D., and Spiekman, L. H. (2004) Amplifiers for the Masses: EDFA, EDWA and SOA Amplets for Metro and Access Applications, IEEE J. Lightw. Technol. 22(1):63-70. This page intentionally left blank Electromagnetic Waves J. H. Causebrook Telecommunications Consultant R. V. Goodman Broadcasting and Telecommunications Engineering Consultant Fundamental Laws of Electromagnetism Many engineering aspects of propagation do not need a knowledge of historically derived principles, but these do provide a good background. The following are the fundamental laws of electromagnetism. Gauss's electrostatic theorem: The normal component of electric displacement (flux), D, inte- grated over any closed surface equals the total charge, p, within the surface. Gauss's magnetic theorem: The normal component of magnetic induction, B, integrated over any closed surface is 0. Faraday's law of electromagnetic induction: The parallel component of an electric field, E, integrated around a closed path is proportional to the rate of change of the flux of magnetic induction enclosed by the path (Lenz's law: the constant of proportional- ity is -1). Ampere's law for magnetomotive force: The parallel component of a magnetic field, H, inte- grated round any loop equals the total current, J, flowing through the loop. Maxwell's Equations and Wave Equations Maxwell combined these laws and added the concept of displacement current to give a set of equations. These are expressed below in differential form, using the rationalized M.K.S. units as in equations 7.1 to 7.4. VD = P (7.1) Chapter 7 Electromagnetic Waves (7.2) (7.3) VAH=1+ (7.4) For an infinite homogeneous medium, with no free charges, p, and zero conductivity, O, these equations become as in equations 7.5 to 7.8, where E is the permittivity (dielectric constant), which equals Er E0, the relative permittivity multiplied by the permittivity of free space,