Chapter 24: Fiber Optics
TRUE/FALSE
1. An optical fiber is a waveguide for light.
ANS: T
2. Fiber has greater bandwidth than copper cable.
ANS: T
3. Optical fiber has greater loss per kilometer than copper cable.
ANS: F
4. Fiber is immune to crosstalk.
ANS: T
5. Optical fiber carries a very small amount of current.
ANS: F
6. Optical fiber is easy to "tap".
ANS: F
7. Optical fiber is easy to splice.
ANS: F
8. Optical fiber can be used safely in an atmosphere of explosive gas.
ANS: T
9. Optical fiber can be used to connect a radio transmitter to an antenna.
ANS: F
10. The core has a higher index of refraction than does the cladding.
ANS: T
11. Single-mode fiber causes less dispersion than does multimode fiber.
ANS: T
12. Single-mode fiber is always made from glass.
ANS: T
13. The core of a single mode fiber is on the order of 1000 mm.
ANS: F
14. Single-mode fiber is free of all dispersion effects.
ANS: F
15. Dispersion can be expressed in units of time.
ANS: T
16. The terms "linewidth" and "bandwidth" are equivalent for fiber.
ANS: T
17. Dispersion increases with cable length.
ANS: T
18. Glass fiber-optic cables have a loss of about 3dB per km.
ANS: F
19. Plastic fiber-optic cables have a loss of several hundred dB per km.
ANS: T
20. The losses due to splicing can be greater than the losses due to the cable itself.
ANS: T
21. The purpose of the cladding is to add strength to the fiber-optic cable.
ANS: F
22. The terms "splice" and "connector" are equivalent for fiber.
ANS: F
23. A typical splice has a loss of 0.2 dB or less.
ANS: T
24. Unlike copper cables, it is not possible to make an optical power splitter.
ANS: F
25. Like copper cables, it is possible to make an optical directional coupler.
ANS: T
26. It is possible to make an optical switch.
ANS: T
27. Energy can be expressed in electron-volts.
ANS: T
28. LEDs are commonly used to drive single-mode fiber cables in communications systems.
ANS: F
29. PIN diodes are used as receivers on single-mode fiber cables in communications systems.
ANS: T
30. A LASER diode can be turned on and off at a rate of 10 GHz.
ANS: T
MULTIPLE CHOICE
1. Compared to the core, the index of refraction of the cladding must be:
a. | the same | c. | less |
b. | greater | d. | doesn't have an index of refraction |
ANS: C
2. Fiber-optic cables do not:
a. | carry current | c. | generate EMI |
b. | cause crosstalk | d. | all of the above |
ANS: D
3. Single-mode fiber is made from:
a. | glass | c. | both a and b |
b. | plastic | d. | none of the above |
ANS: A
4. Fiber-optic cable cannot be used:
a. | in an explosive environment |
b. | to connect a transmitter to an antenna |
c. | to isolate a medical patient from a shock hazard |
d. | none of the above |
ANS: B
5. A single-mode cable does not suffer from:
a. | modal dispersion | c. | waveguide dispersion |
b. | chromatic dispersion | d. | all of the above |
ANS: A
6. Scattering causes:
a. | loss | c. | intersymbol interference |
b. | dispersion | d. | all of the above |
ANS: A
7. The loss in single-mode fiber-optic cable due to the glass is about:
a. | 40 dB per km | c. | 0.4 dB per km |
b. | 4 db per km | d. | zero loss |
ANS: C
8. The loss in single-mode fiber-optic cable due to a splice is about:
a. | 0.02 dB | c. | 1 dB |
b. | 0.2 db | d. | 3 dB |
ANS: A
9. The loss in single-mode fiber-optic cable due to a connector is about:
a. | 0.02 dB | c. | 1 dB |
b. | 0.2 db | d. | 3 dB |
ANS: B
10. Which of the following is a type of fiber connector:
a. | ST | c. | SMA |
b. | SC | d. | all of the above |
ANS: D
11. The quantum of light is called:
a. | an erg | c. | a photon |
b. | an e-v | d. | a phonon |
ANS: C
12. LASER stands for:
a. | Light Amplification by Simulated Emission of Radiation |
b. | Light Amplification by Stimulated Emission of Radiation |
c. | Light Amplification by Simulated Emitted Rays |
d. | Light Amplification by Stimulated Emitted Rays |
ANS: B
13. APD stands for:
a. | Avalanche Photodiode | c. | Avalanche Photo Detector |
b. | Advanced Photodiode | d. | Advanced Photo Detector |
ANS: A
14. In a PIN diode, leakage current in the absence of light is called:
a. | baseline current | c. | dark current |
b. | zero-point current | d. | E-H current |
ANS: C
15. For a light detector, responsivity is measured in:
a. | amps per watt | c. | mA per joule |
b. | mW per amp | d. | msec per mW |
ANS: A
COMPLETION
1. In the core, the angle of incidence equals the angle of ____________________.
ANS: reflection
2. The core is surrounded by the ____________________.
ANS: cladding
3. The ____________________ angle is where refraction changes to reflection.
ANS: critical
4. An electron-volt is a measure of ____________________.
ANS: energy
5. The numerical aperture is the ____________________ of the angle of acceptance.
ANS: sine
6. Optical fiber relies on total ____________________ reflection.
ANS: internal
7. Chromatic dispersion is also called ____________________ dispersion.
ANS: intramodal
8. With optical fiber, ____________________ light is more common than visible light.
ANS: infrared
9. In multimode fiber, ____________________ index has less dispersion than step index.
ANS: graded
10. For laser diodes, the term ____________________ is used instead of bandwidth.
ANS: linewidth
11. Dispersion can be expressed in units of ____________________ rather than bandwidth.
ANS: time
12. ____________________ interference is when one pulse merges with the next pulse.
ANS: Intersymbol
13. The optical fiber is free to move around in a ____________________ cable.
ANS: loose-tube
14. The optical fiber is not free to move around in a ____________________ cable.
ANS: tight-buffer
15. A ____________________ is a short length of fiber that carries the light away from the source.
ANS: pigtail
16. Good connections are more critical with ____________________-mode fiber.
ANS: single
17. A ____________________ diode is the usual light source for single-mode cable.
ANS: laser
18. The quantum of light is called the ____________________.
ANS: photon
19. A ____________________ diode is the usual light detector for single-mode cable.
ANS: PIN
20. For safety, you should never ____________________ at the end of an optical fiber unless you know it is not connected to a light source.
ANS: look
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