E-Book Content
Optical Communications Wolfgang Freude* High-Frequency and Quantum Electronics Laboratory (Institut fur Hochfrequenztechnik und Quantenelektronik) University of Karlsruhe International Department SS 2000 24th April 2001 *Not to be published. All rights reserved. No part of this compuscript may be reproduced or utilized in any form or by any means without permission in writing from the author. Contents 1 Introduction 1 2 Light Waveguides 2.1 Fundamentals of wave propagation 2.1.1 Medium properties 2.1.2 Wave equation 2.1.3 Homogeneous medium 2.1.4 Properties of silica glass 2.1.5 Plane boundary 2.2 Principles of waveguiding 2.3 Slab waveguide 2.3.1 Eigenvalues in pictures 2.3.2 Eigenvalue equation 2.3.3 Vector solution 2.3.4 Scalar solution 2.3.5 Group delay dispersion 2.4 Strip waveguide 2.5 Fibre waveguide 2.5.1 Modal fields in a fibre 2.5.2 Weakly guiding fibre in scalar approximation 2.5.3 Step-index fibre 2.5.4 Parabolic-index fibre 2.5.5 Orthogonality and coupling efficiency 2.6 Intensity modulation 2.6.1 Gaussian impulse 2.6.2 Light source 2.6.3 Impulse response and transfer function 2.6.4 Noiseless light source 2.6.5 Noisy light source 2.6.6 Sinusoidal modulation 2.6.7 Multimode waveguide 3 3 3 5 6 10 14 16 17 18 19 21 22 24 25 25 26 28 30 35 37 37 38 38 39 41 47 49 50 3 Ligtht sources 3.1 Number of modes 3.2 Luminescence and laser radiation 3.2.1 Lifetime and linewidth 3.2.2 Laser action 3.2.3 Modulation 3.2.4 Amplification 3.2.5 Coupling efficiency 3.2.6 Noise 3.2.7 Laser active materials 53 54 55 57 57 58 58 58 58 58 3.3 3.4 3.5 3.6 Semiconductor light source 3.3.1 Energy bands and density of states 3.3.2 Filling of electronic states 3.3.3 Impurities and doping 3.3.4 Compound semiconductors and heterojunctions Emission and absorption of light 3.4.1 Induce