[ESAT] FIBER OPTICS

1. Refraction is the

A. Bending of light waves

B. Reflection of light waves

C. Distortion of light waves

D. Diffusion of light waves

A

2. Losses in optical fibers can be

caused by (indicate the false

statement)

A. impurities

B. microbending

C. attenuation in the glass

D. stepped index operation

D

3. Single mode step index cable has a

core diameter in the range of

A. 100 to 1000 micrometer

B. 50 to 100 micrometer

C. 2 to 15 micrometer

D. 5 to 20 micrometer

C

4. The operation of a fiber-optic cable

is based on the principle of

A. Refraction

B. Reflection

C. Dispersion

D. Absorption

B

5. Which of the following refers to the

bandwidth of optical fiber?

A. 1 Hz - 30,000 Hz

B. 1kHz - 300 kHz

C. IMHz - 300 MHz

D. 1 MHz - 500 MHz

D

6. Too much overfeed whilst splicing

will cause

A. Waisting

B. A bubble being formed due to air

being trapped inside the fiber

C. A bulge in the fiber

D. Runback

A

7. The speed of light in plastic

compared to the speed of light in air is

A. Less

B. More

C. The same

D. Zero

A

8. In

propagation, the core is

varying densities.

A. Multimode step-index

B. Multimode graded-index

C. Multimode single-index

D. Single-mode

B

9. The loss in single-mode fiber-optic

cable due to a connector is about:

A. 0.02 dB

B. 0.2 dB

C. 1 dB

D. 3 dB

B

10. In

propagation, the beam of

propagated light is almost horizontal,

and the low-density core has a small

diameter compared to the cores of the

other propagation modes.

A. Multimode step-index

B. Multiple graded-index

C. Multimode single-index

D. Single-mode

D

11. Which cable length has the highest

attenuation?

A. 1 km

B. 2 km

C. 95 ft

D. 500 ft

B

12. This determines the maximum data

rate capability of the detector

A. Responsivity

B. Dark current

C. Response speed

D. Spectral response

C

13. Fibers are single mode at a

particular wavelength only when

V<2.405. Under what condition, if

any, will the fiber cease to be single

mode?

A. When the wavelength of the light is

greater than the cutoff wavelength

B. When the wavelength of the light is

less than the cutoff wavelength

C. When the core diameter is

extremely small

D. Both B and C

B

14. As light is coupled in a multipoint

reflective device, the power is reduced

by

A. 1.5 dB

B. 0.1 dB

C. 0.5 dB

D. 0.001 dB

C

15. One of the following is referred to

as a major component of an optical

time domain reflectometer.

A. Pulse generator and vertical plate

B. Laser and horizontal plate

C. Pulse generator laser

D. Vertical and horizontal plate

C

16. A function of an optic isolator

A. Cancels reflected waves

B. Amplifies signal transmitted

C. Filters unnecessary signals

D. All of these

A

17. The term power budgeting refers to

A. the cost of cables, connectors,

equipment, and installation

B. the loss of power due to defective

components

C. the total power available minus the

attenuation losses

D. the comparative costs of fiber and

copper installations

C

18. Which of the following is the

fastest light sensor?

A. PIN diode

B. Photovoltaic diode

C. Phototransistor

D. Avalanche photodiode

D

19.

is the propagation method

subject to the greatest distortion.

A. Multimode step-index

B. Multimode Graded-index

C. Multiple single-index

D. Single-mode

A

20. Laser light is very bright because i

is

A. Pure

B. White

C. Coherent

D. Monochromatic

C

21. Loss comparisons between fusion

splices and mechanical splices are

A. 1:10

B. 10:1

C. 20:1

D. 1:20

A

22. Dispersion

A. Causes the core to spread out and

get wider as the pulse is transmitted

along the fiber

B. Results in the wavelength of the

light increasing along the fiber

C. Is the lengthening of light pulses as

they travel down the fiber

D. Cannot occur with a laser light

Source

C

23. What does the elastic store refer to

in the time division multiplex system

used in fiber optic?

A. Amplifier

B. Detector

C. Holding memory

D. Synchronous Timer

B

24. A single fiber can handle as many

voice channel as

A. a pair of copper conductors

B. a 1500-pair cable

C. a 500-pair cable

D. a 1000-pair cable

B

it

25. Which of the following refers to

the relative refractive index difference

of single mode fibers?

A. 0.3 - 5 %

B. 0.4- -1.5 %

C. 0.8 - 3 %

D. 0.1 0.3 %

D

26. When light falls on a piece of

black paper, what happens to most of

the light?

A. It is absorbed

B. It is scattered

C. It is reflected

D. It is refracted

A

27. The terms single mode and

multimode are best describes as

A. the number of fibers placed into a

fiber-optic cable

B. the number of voice channels each

fiber can support

C. the number of wavelengths each

fiber can support

D. the index number

C

28. Which type of fiber-optic cable is

the most widely used?

A. Single - mode step - index

B. Multimode step-index

C. Single - mode graded - index

D. Multimode graded - index

B

29. Which of the following is not a

common detector?

A. PIN diode

B. Photovoltaic diode

C. Photodiode

D. Avalanche photodiode

B

30. The ratio of the speed of light in

air to the speed of light in another

substance is called the

A. Speed factor

B. Index of reflection

C. Index of refraction

D. Speed gain

C

31. Which of the following terms

describes the reason that light is

refracted at different angles?

A. Photon energy changes with

wavelength

B. Light is refracted as a function of

surface smoothness

C. The angle is determined partly by a

and b

D. The angle is determined by the

index of the materials

D

32. At what power levels does fiber

optic have when used in electronic

communications?

A. Range of over 100 watts

B. Range of micro to milliwatts

C. Range of over 50 watts

D. Range of milliwatt to watts

B

33. In SONET, OC-1 stands for:

A. Optical Carrier level one

B. Optical Coupler unidirectional

C. Optical Channel one

D. Optical Cable type 1

A

34. The loss (attenuation) of signal in

optical fiber is due to

A. Scattering

B. Absorption

C. Microbending

D. All the above

D

35. Power above the minimum

required by an optical receiver is

called:

A. gain margin

B. system margin

C. excess gain

D. overdrive

B

36. What is the device used in fiber

optic communication which consist of

a receiver transmitter use to clean up

and amplify digital data moving in one

direction and another in possible

direction?

A. Optics compressor

B. Optic retarder

C. Optic isolator

D. Optic regenerator

D

37. The following consideration is

important when deciding between

using a diode laser or an LED

A. Response time

B. Power levels

C. Temperature sensitivity

D. Failure characteristics

A

38. The core of a fiber-optic cable is

surrounded by

A. Wire braid shield

B. Kevlar

C. Cladding

D. Plastic insulation

C

39. A popular light wavelength in

fiber-optic cable is

A. 0.7 um

B. 1.3 um

C. 1.5 um

D. 1.8 um

B

40. The upper pulse rate and

information-carrying capacity of a

cable is limited by

A. Pulse shortening

B. Attenuation

C. Light leakage

D. Modal dispersion

B

41. Fiber optic connections suffer high

loss due

A. Air gaps

B. Rough surfaces

C. Axial misalignment

D. All the above

D

42. Loss due to the diffraction of light

when it strikes on the irregularities

formed during the manufacturing

process of the fiber optics.

A. Absorption loss

B. Attenuation

C. Bending loss

D. Rayleigh scattering loss

D

43. For a light detector, responsivity is

measured in:

A. amps per watt

B. UW per amp

C. mA per joule

D. usec per uw

A

44. Infrared range for fiber optics

A. 400 - 700 nm

B. 700 - 1200 nm

C. 300 2000 nm

D. 400 7000 nm

B

45. APD stands for:

A. Avalanche Photodiode

B. Advanced Photodiode

C. Avalanche Photo Detector

D. Advanced Photo Detector

A

46. Which type of fiber optic cable has

the least modal dispersion?

A. Single mode step index

B. Multimode step index

C. Single mode graded index

D. Multimode graded index

A

47. In the telecommunications

industry, the most comm monly used

fiber(s) are

A. 50 micron

B. 62.5 micron

C. 50 and 62.5 micron

D. 125 micron

C

48. Which of the following cables will

have the highest launch power

capability?

A. 50/125/0.2

B. 85/125/0.275

C. 62.5/125/0.275

D. 100/140/0.3

D

49. The core of a fiber-optic cable is

made of

A. Air

B. Glass

C. Diamond

D. Quartz

B

50. The mechanical splice is best

suited for

A. quicker installation under ideal

conditions

B. minimum attenuation losses

C. field service conditions

D. situations in which cost of

equipment is not a factor

C

51. The 1.55 um "window" is not yet

in use with fiber optic systems because

A. the attenuation is higher than at

0.85

B. the attenuation is higher that at 1.3

im

C. suitable laser devices have not yet

been developed

D. it does not lend itself to wave

D

52. Insertion loss is

A. Caused by thermal noise that

intermodulates with the signal

travelling on the same medium

B. A momentary disruption of signal

due to power interruption

C. A low level high frequency signal

inserted into the original signal caused

by thermal noise

D. None of the preceding choices

D

53. A single-mode cable does not

suffer from:

A. modal dispersion

B. chromatic dispersion

C. waveguide dispersion

D. all of the above

A

54. It is a science of measuring light

throughout the entire electromagnetic

spectrum

A. Radiometry

B. Photometry

C. Ophthalmology

D. Optometry

A

55. Single-mode fiber is made from:

A. glass

B. plastic

C. both a and b

D. none of the above

A

56. One of the following is considered

the largest source of signal power loss

in the use of fiber optic as

communications medium such as due

to misalignment.

A. Bending

B. Scattering

C. Connection

D. Absorption

C

57. Bend loss is

A. A form of increased attenuation

caused by bends radiating from the

side of the fiber

B. An intermittent decrease of

transmitter power caused by the

curvature of the earth's surface

C. A decrease of signal strength at the

receiver caused by the bends of a

folded dipole in a yagi antenna

D. None of the preceding choices

A

58. The reflective index number is

A. a number which compares the

transparency of a material with that of

air

B. a number assigned by the

manufacturer to the fiber in question

C. a number which determines the cor

diameter

D. a term for describing core elasticity

A

59. EMD is best describe by which

statement?

A. 70 percent of the core diameter and

B. 70 percent of the fiber diameter and

70% of the cone of acceptance should

be filled with light

C. 70 percent of input light should be

measured at the output

D. 70 percent of the unwanted

wavelengths should be attenuated by

the fiber

A

60. The term critical angle describes

A. the point at which light is refracted

B. the point at which light becomes

invisible

C. the point at which light has gone

from the refractive mode to the

reflective mode

D. the point at which light has crossed

the boundary layers from one index to

another

C

61. Modal dispersion is caused by the

A. Dependence of wavelength on

index of refraction

B. Dependence of propagation

constant on index of refraction

C. Dependence of the propagation

constant on the wavelength

D. Dependence of the propagation

constant on the mode number

D

62. The effect of multimode

propagation caused the rays leaving

the fiber to interfere constructively and

destructively as they leave the end of

the fiber, this effect is called

A. Multimode interference

B. Modal delay spreading

C. Multimode effect

D. Single modal effect

B

63. Optical fibers, unlike wire media,

are highly resistant to

A. High-frequency transmission

B. Low-frequency transmission

C. Electromagnetic interference

D. Refraction

C

64. Referred to as a limit in reducing

further the loss of signal passing

through a fiber optic caused by

scattering

A. Rayleigh effect

B. Manufacturing effect

C. Natural effect

D. Material effect

A

65. In an optical fiber, the inner core is

the cladding

A. Denser than

B. Less dense than

C. The same density as

D. Another name for

A

66. An absorption loss caused by

valence electrons in the silica material

from which fibers are manufactured.

A. Modal dispersion

B. Infrared absorption

C. Ion resonance absorption

D. Ultraviolet absorption

D

67. The time it takes a light induced

carrier travel across the depletion

region of the semiconductor

A. Dispersion

B. Response time

C. Irradiance

D. Transit time

D

68. Recent laser developments for

fiber optic communication include

A. Distributed feedback (DFB)

B. Heterojunction

C. Vertical cavity surface emitting

(VCSEL)

D. a and c above

D

69. The cladding which surrounds the

fiber core

A. is used to reduce optical

interference

B. is used to protect the fiber

C. acts to help guide the light in the

core

s

D. ensures that the refractive index

remains constant

C

70. Fiber optic technology is used in

applications of

A. Local area networks (LANS)

B. Cable TV (CATV) systems

C. Telephone networks

D. All the above

D

4

.

71. Optical fibers for

telecommunications are typically

about

mils thick and consist of a

glass core, a glass cladding of lower

index of refraction, and a protective

coating.

A. 5

B. 6

C. 7

D. 8

A

72. The effect of multimode

propagation caused the rays leaving

the fiber to interfere constructively

and

destructively as they leave the end of

the fiber, this effect is called

A. Multimode interference

B. Light dispersion

C. Modal delay spreading

D. Single modal effect

C

73. Most fiber-optic light sources emit

light in which spectrum?

A. Visible

B. Infrared

C. Ultraviolet

D. X- ray

A

74. One of the following is among the

types of fiber optics used in electronics

communication

A. Step - index multimode

B. Graded - index multimode

C. Semi - graded multimode

D. Single mode

C

75. Which of the following is not a

factor in cable light loss?

A. Reflection

B. Absorption

C. Scattering

D. Dispersion

A

76. Chromatic dispersion can be

eliminated by

A. Using a monochromatic light

Source

1

B. Using a very small numerical

aperture fiber

C. Using a graded index fiber

D. Using a very sensitive

photodetector

A

77. A quarter wavelength device made

of crystalline calcite that changes

polarization in the optic fiber

communication.

A. Isolator

B. Retarder

C. Polarizer

D. Filters

B

78. The optical band designation(s)

include

A. S

B. C

C. L

D. All the above

D

79. The dispersion of light in fiber-

optic cable caused by a portion of the

light energy traveling in the cladding

is called

A. Modal dispersion

B. Material dispersion

C. Waveguide dispersion

D. Cable dispersion

C

80. Which is an advantage of optical

communication links over using

transmission lines or waveguides?

A. Small size

B. Extremely wide bandwidths

C. Immunity to electromagnetic

interference (EMI)

D. All the above

D

81. In fiber optics, higher mode refers

to

A. Cladding boundary at high angle

B. Backscattering electromagnetic

signals

C. Diffracting signals

D. All of these

A

a

82. An optic fiber regenerator which is

used in communication is consisting of

to clean up and

amplify digital data moving in one

direction and a similar system for the

opposite direction.

A. Filter and power

B. Transmitter and receiver

C. Receiver and power

D. Transmitter and power

B

83. The wavelength of visible light

extends from

A. 0.8 to 1.6 um

B. 400 to 750 nm

C. 200 to 600 nm

D. 700 to 1200 nm

B

84. What is the wavelength for deep

violet light?

A. 500 nm

B. 100 nm

C. 200 nm

D. 700 nm

A

85. The main benefit of light-wave

communications over microwaves or

any other communications media are

A. Lower cost

B. Better security

C. Wider bandwidth

D. Freedom from interference

C

86. The most common device used as

a light detector in fiber optic

communication system.

A. LED

B. Darlington phototransistor

C. APDs

D. PIN diode

C

87. An advantage of fiber optic over

coaxial cable as a result of coupling

signals from one to the other due to

changing magnetic field on one or

both.

A. Feedback

B. Crosstalk

C. Electrical hazard

D. Shielding

B

88.

is the oscillation produced

when the ILD are operated above a

certain threshold current.

A. Lasing

B. Photons

C. P se spreading

D. Dark current

A

89. The most common light used in

fiber-optic links is

A. Infra-red

B. Red

c. Violet

D. Ultraviolet

A

90. The

of a detector is

the fraction of incident photons that

produce a photoelectron or electron-

hole pair.

A. Responsivity

B. Photon efficiency

C. Aperture

D. Quantum efficiency

D

91. The core of the optical fiber has

A. A medium index of refraction

B. A lower index of refraction than the

cladding

C. A lower index of refraction than air

D. A higher index of refraction than

the cladding

D

92. A parameter of light beam that do

not change quantity when it enters one

medium from another

A. Intensity

B. Penetration

C. Frequency

D. Wavelength

C

93. Which of the following is not a

common type of fiber-optic cable?

A. Single - mode step index

B. Multimode graded - index

C. Single - mode grade - index

D. Multimode step index

C

94. One of the major limitations of a

plastic fiber optic used in

communication.

A. Due to its noise

B. Due to its bandwidth

C. Due to its high losses

D. Due to its weight

C

95. Total internal reflection takes place

if the light ray strikes the interface at

an angle with what relationship to the

critical angle?

A. Less than

B. Greater than

C. Equal to

D. Zero

B

96. Light goes from medium A to

medium B at angle of incidence of 40

degrees. The angle of refraction is 30

degrees. The speed of light in B

A. Is the same as that in A

B. Is greater that in A

C. Is less that in A

D. May be any of these, depending on

the specific medium

D

97. The upper pulse rate and

information carrying capacity of a

cable is limited by

A. Pulse shortening

B. Attenuation

C. Light leakage

D. Modal dispersion

D

98. Type of bend that occurs as a result

of differences in thermal contraction

rates between the core and the

cladding material

A. Macrobending

B. Microbending

C. Quad bending

D. Constant K bending

B

99. Between silicon and gallium

arsenide, which has the greatest index

of refraction?

A. Gallium Arsenide

B. Neither of silicon nor gallium

arsenide

C. Silicon

D. They are equal

A

100. It is a graphical representation of

the magnitude of the refractive index

across the fiber.

A. Mode

B. Index profile

C. Numerical aperture

D. Refractive index

B