Network Infrastructure and Architecture: Designing High-Availability Networks

2

FIBER-OPTIC TRANSMISSION

2.1 Introduction

2.2 Fiber Optic Communication

2.2.1 Why Optical Fiber?

2.2.2 Propagation: Single- and Multimode Fibers

2.3 Light Emission and Detection

2.3.1 Light Sources

2.3.2 Photodetectors

2.4 Optical Modulation

2.4.1 Direct Modulation

2.4.2 External Modulation

2.5 Optical Amplification

2.5.1 Erbium - Doped Fiber Amplifiers

2.5.2 Raman Amplifiers

2.5.3 EDFA vs. Raman Amplifier

2.6 Fiber Transmission Impairments

2.6.1 Chromatic Dispersion

2.6.2 Dispersion Management Techniques

2.6.3 Polarization Mode Dispersion

2.6.4 Nonlinear Effects

Key Points

Acknowledgments

References

2.1 INTRODUCTION

Consider the task of transmitting data over a great distance, say from the east to west coasts in North America or from New York to London. If a reach of hundreds or even thousands of kilometers is required, the question arises: What is the best physical medium to use to send information rapidly? It turns out that sending pulses of light down an optical fiber is the fastest and most cost-effective means for high-capacity data transmission over large distances. Light can travel in glass fibers with significantly lower attenuation levels than high-frequency electrical signals can be transported using conductors. Optical signals can thus travel much farther before any need for amplification or regeneration is required.

Propagation of light over great distances has been made possible by the development of low-loss single-mode fiber which has achieved a phenomenal loss ...