This is the summary notes of the important terms and concepts in Chapter 13 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
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CHAPTER 13 |
OPTICAL FIBER TRANSMISSION MEDIA |
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Items |
Definitions |
Terms |
|
1 |
Uses light as a carrier of information. |
Optical communications System |
|
2 |
Electronic communications system is directly proportional to bandwidth. |
Information-carrying capacity |
|
3 |
Bandwidth of an analog communications system as a percentage of its carrier frequency. |
bandwidth utilization ratio |
|
4 |
Device constructed from mirrors and selenium detectors that transmitted sound waves over a beam of light. |
Photophone |
|
5 |
Experimented with an apparatus called photophone. |
Alexander Graham Bell |
|
6 |
Used extensively in medical field. |
Flexible fiberscope |
|
7 |
Invented in 1960. |
Laser (light amplification by stimulated emission of radiation) |
|
8 |
Advantages of Optical Fiber cables. |
1. wider bandwidth and greater information Capacity 2.immunity to crosstalk 3. immunity to statistic Interference 4. environmental Immunity 5. safety and convenience 6. lower transmission loss 7. security 8. durability and reliability 9. economics |
|
9 |
Disadvantages of Optical Fiber cables. |
1. interfacing cost 2. strength 3. remote electrical Power 4. optical fiber cables are more susceptible to losses introduced by bending the cable 5. specialized tools, equipment, and training |
|
10 |
Reduces the possibility of the occurrence of a detrimental phenomenon. |
Stress corrosion |
|
11 |
One wire is at the ground potential, whereas the other is at signal potential. |
Single-ended or unbalanced |
|
12 |
Protective coating. |
Buffer jacket |
|
13 |
Increases the tensile strength of the overall cable assembly. |
Strength member |
|
14 |
Process of decaying from one energy level to another energy level. |
Spontaneous decay or spontaneous emission |
|
15 |
Science of measuring only light waves that are visible to human eye. |
Photometry |
|
16 |
Measures the rate at which electromagnetic waves transfer light energy. |
Optical power |
|
17 |
Spectral separation of white light. |
Prismatic refraction |
|
18 |
Simply the ratio of velocity of propagation of a light ray in free space to the velocity of propagation of a light ray in a given material. |
Refractive index |
|
19 |
Angle at which the propagating ray strikes the interface with respect to the normal. |
Angle of incidence |
|
20 |
Angle formed between the propagating ray and the normal after the ray has entered the second medium. |
Angle of refraction |
|
21 |
Closely related to acceptance angle and is the figure of merit commonly used to measure the magnitude of the acceptance angle. |
Numerical aperture |
|
22 |
Simply means path. |
Mode |
|
23 |
More than one path. |
Multimode |
|
24 |
Probably the most important characteristic of the cable. |
Power loss |
|
25 |
Three factors that contribute to the absorption losses in optical fibers: |
1. ultra violet absorption 2. infrared absorption 3. ion resonance absorption |
|
26 |
Caused mainly by small bends and kinks in the fiber. |
Radiation losses |
|
27 |
Caused by excessive pressure and tension and generally occur when fibers are bent during handling or installation. |
Contants-radius bends |
|
28 |
Caused by the difference in the propagation times of light rays that take different path down a fiber. |
Modal dispersion |
|
29 |
A p-n junction made from two different mixtures of the same types of atom. |
Mojunction structure |
|
30 |
Generally constructed of silicon-doped gallium-arsenide. |
Epitaxially grown |
|
31 |
Homojunction LED’s output approximately 500 µ at a wavelength of 900 nm. |
Planar diffused |
|
32 |
Advantages of heterojunction devices over homojunction devices; |
1. increase in current density generates a more brilliant light spot. 2. smaller emitting area makes it easier to couple its emitted light into a fiber. 3. small effective area has a smaller capacitance, which allows the planar heterojunction LED to be used at a higher speed. |
|
33 |
Depletion-layer photo diode and is probably the most common device used as a light detector in fiber optic communications system. |
PIN diode |
|
34 |
Characteristic of a light detector. |
1. responsivity 2. dark currents 3. transit time spectral response 5. light sensitivity |
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