fiber optic blake

8/3/2019 Fiber Optic Blake

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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: T5. 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 m.

ANS: F

14. Single-mode fiber is free of all dispersion effects.

ANS: F

15. Dispersion can be expressed in units of time.

ANS: T16. 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: F25. Like copper cables, it is possible to make an optical directional coupler.

ANS: T


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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: T30. 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 antennac. 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


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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. SMAb. 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. W per amp d. sec per W

ANS: A


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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: sine6. 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: infrared9. 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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