Self-Test
& Supply the missing word(s) in each statement.
Choose the letter that best answers each question.
1. Fiber-optic cables carry _____ rather than electrical signals.
2. The three main types of information carried by fiber optic-cables are _____, _____, and _____.
3. The major use of fiber-optic cables is in _____.
4. Fiber-optic cables are made of _____ or _____.
5. The main benefit of fiber-optic cable over electric cable is its _____.
6. True or false. Fiber-optic cable has more loss than electric cable over long distances.
7. True or false. Fiber-optic cable is smaller, lighter, and stronger than electric cable.
8. List the two main disadvantages of fiber optic cable.
9. The two most commonly used light sources in fiber-optic systems are _____.
10. Voice and video signals are converted into before being transmitted by a light beam.
11. The device that converts the light pulses into an electrical signal is a(n) _____.
12. Regenerative units called _____ are often used to compensate for signal attenuation over long distances.
13. Light is a type of _____ radiation.
14. A fiber-optic cable can be viewed as a light _____.
15. Light travels in a
a. Circle
b. Straight line
c. Curve
d. Random way
16. The wavelength of light is usually expressed in _____ or _____.
17. The lowest-frequency visible light is
a. Red
b. Violet
18. A micrometer, or micron, is a length of _____ of a _____.
19. The wavelength range of visible light is _____ to _____ nm.
20. Infrared light has a wavelength that is
a. Less than 400 nm
b. More than 700 nm
c. Less than 700 nm
21. The optical spectrum is made up of what three parts?
22. The speed of light in air is _____ m/s or _____ mi/s.
23. True or false. The speed of light is slower in glass or water than it is in air.
24. The number that tells how fast light travels in a medium compared to air is the _____ of _____.
25. Light beams can be bounced or their direction can be changed by _____ with a(n) _____.
26. The bending of light rays due to speed changes when moving from one medium to another is called _____.
27. If a light ray strikes a mirror at an angle of 30° from the normal, it is reflected at an angle of _____ ° from the normal.
28. When the angle of refraction is 90° to the normal, the ray travels along the _____ between the two media. Therefore, the incident ray strikes the surface at the _____ angle.
29. When the incident ray strikes the interface at an angle greater than the critical angle, _____ occurs.
30. The critical angle depends upon the value of the _____ of _____.
31. Which material has the best optical characteristics and lowest loss?
a. Plastic
b. Glass
c. they are equal
32. The core is protected by the _____.
33. In PCS cable, the core is _____ and the cladding is _____.
34. The index of refraction is highest in the
a. Core
b. Cladding
35. List the three main types of fiber-optic cable.
36. Stretching of the light pulse is called _____.
37. List the two types of cable in which light pulse stretching occurs.
38. High-frequency pulses can be best transmitted over _____ cable.
39. Pulse stretching causes the information capacity of a cable to
a. Increase
b. Decrease
40. Graded index means that the _____ of _____ of the core varies over its cross section
41. Single-mode step-index cable has a Core diameter in the range of
a. 100 to 1000 mm
b. 50 to 100 mm
c. 2 to 15 mm
42. A _____ is applied over the cladding to protect against moisture, damage, etc.
43. A common protective layer in a cable is made of _____ mesh.
44. Fiber-optic cables are available with the following number of cores: _____.
45. Light loss in a cable is called _____.
46. Light loss is caused by _____.
47. Light loss is measured in _____ per_____.
48. A cable with a loss of 5 dB will have _____ percent of the input appear at the output (see Fig. 13-19). (page 365-Frenzel)
49. True or false. A kilometer is longer than a mile.
50. Which cable length will have the least attenuation?
a. 40 ft
b. 120 ft
c. 1780 ft
d. 1 km
51. Three cables with attenuations of 9, 22, and 45 dB are spliced together. The total attenuation is _____ dB.
52. True or false. Fiber-optic cables may be spliced.
53. To conveniently link and attach fiber-optic cables to one another and related equipment, _____ are used.
54. The two most common light sources used in fiber-optic transmitters are _____.
55. The most popular light wavelength is _____ mm because fiber-optic cable attenuation is lowest at that wavelength.
56. True or false. The light from a 1.55mm LED is visible.
57. Usually LEDs are made of _____.
58. Single frequency light is called _____.
59. The condition of all emitted light waves being in phase is known as _____.
60. A single-frequency intense light source is known as a(n) _____.
61. The reflective surfaces on a laser diode structure form a(n) _____ that produces in-phase light waves.
62. For normal operation, LED and ILDs are _____ (reverse, forward)-biased.
63. Which is faster, an LED or ILD?
64. Which produces the brightest light, an LED or ILD?
65. During normal operation, all photodiodes are _____ (reverse, forward)-biased.
66. Light falling on the PN junction of a photodiode causes the diode's _____ current to increase.
67. The most sensitive and fastest light detector is the _____.
68. 68-.The two main circuits in a fiber-optic receiver are _____.
69. The product of the bit rate and distance of a system is 90 Mbits·km/s. The rating at 3 km is _____ Mbits/s.
In today's systems, the average maximum distance between repeaters is between _____ and _____ mi.
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