Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Abbreviations
- 1 Introduction: The fiber optics revolution
- 2 Basic optics
- 3 Basic characteristics of the optical fiber
- 4 Ray paths and pulse dispersion in planar optical waveguides
- 5 Pulse dispersion in graded index optical fibers
- 6 Material dispersion
- 7 Modes in planar waveguides
- 8 Propagation characteristics of a step index fiber
- 9 Propagation characteristics of graded index fibers
- 10 Waveguide dispersion and design considerations
- 11 Sources for optical fiber communication
- 12 Detectors for optical fiber communication
- 13 Design considerations of a fiber optic communication system
- 14 Optical fiber amplifiers
- 15 Dispersion compensation and chirping phenomenon
- 16 Optical solitons
- 17 Single-mode fiber optic components
- 18 Single-mode optical fiber sensors
- 19 Measurement methods in optical fibers: I
- 20 Measurement methods in optical fibers: II
- 21 Periodic interactions in waveguides
- 22 The ray equation in cartesian coordinates and its solutions
- 23 Ray paths and their classification in optical fibers
- 24 Leaky modes
- Appendix A Solution of the scalar wave equation for an infinite square law medium
- Appendix B The far-field pattern
- Appendix C WKB analysis of multimode fibers
- Appendix D Gaussian envelope approximation
- Appendix E Coupled-mode equations
- Appendix F Derivation of coupled-mode equation for periodic coupling
- Appendix G Leakage loss in optical waveguides
- References
- Index
12 - Detectors for optical fiber communication
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Abbreviations
- 1 Introduction: The fiber optics revolution
- 2 Basic optics
- 3 Basic characteristics of the optical fiber
- 4 Ray paths and pulse dispersion in planar optical waveguides
- 5 Pulse dispersion in graded index optical fibers
- 6 Material dispersion
- 7 Modes in planar waveguides
- 8 Propagation characteristics of a step index fiber
- 9 Propagation characteristics of graded index fibers
- 10 Waveguide dispersion and design considerations
- 11 Sources for optical fiber communication
- 12 Detectors for optical fiber communication
- 13 Design considerations of a fiber optic communication system
- 14 Optical fiber amplifiers
- 15 Dispersion compensation and chirping phenomenon
- 16 Optical solitons
- 17 Single-mode fiber optic components
- 18 Single-mode optical fiber sensors
- 19 Measurement methods in optical fibers: I
- 20 Measurement methods in optical fibers: II
- 21 Periodic interactions in waveguides
- 22 The ray equation in cartesian coordinates and its solutions
- 23 Ray paths and their classification in optical fibers
- 24 Leaky modes
- Appendix A Solution of the scalar wave equation for an infinite square law medium
- Appendix B The far-field pattern
- Appendix C WKB analysis of multimode fibers
- Appendix D Gaussian envelope approximation
- Appendix E Coupled-mode equations
- Appendix F Derivation of coupled-mode equation for periodic coupling
- Appendix G Leakage loss in optical waveguides
- References
- Index
Summary
Introduction
An optital detector is a device that converts light signals into electrical signals, which can then be amplified and processed. Such detectors are one of the most important components of an optical fiber communcation system and dictate the performance of a fiber optic communication link.
There are many different types of photodetectors such as photomultiplier tubes, vacuum photodiodes, pyroelectric detectors, and semiconductor photodiodes. Semiconductor photodiodes are the most commonly used detectors in optical fiber systems since they provide good performance, are compatible with optical fibers (being small in size), and are of relatively low cost. These photodiodes are made generally from semiconductors such as silicon or germanium or from compound semiconductors such as GaAs, InGaAs, etc.
In this chapter we briefly discuss the basic principle of operation of two commonly used photodiodes – namely, PIN (p-doped, intrinsic, and n-doped layers) diode and avalanche photodiodes (APD) – and study their important characteristics that are of particular relevance to optical fiber communication systems.
Principle of optical detection
The basic principle behind photodetection using semiconductors is optical absorption. When light is incident on a semiconductor, the light may or may not get absorbed depending on its wavelength. If the energy hv of a photon of the incident light beam is greater than the bandgap of the semiconductor, then it can be absorbed, leading to generation of e–h pairs (see Section 11.4.2). When an electric field is applied across the semiconducting material, the photogenerated e–h pairs are swept away, leading to a photo current in the external circuit.
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- An Introduction to Fiber Optics , pp. 238 - 248Publisher: Cambridge University PressPrint publication year: 1998
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