Fiber Optics [MITRC refresher]

1.        A transparent material along which we can transmit light is called

a.        Fiber optics

b.        Flashlight

c.        An optic fiber

d.        Xenon bulb

2.        A simple fiber optic system would consist of

a.        A light source, an optic fiber and a photoelectric cell

b.        A laser, an optic fiber and an LED

c.        A copper coaxial cable, a laser and a photoelectric cell

d.        An LED, a CRT and a light source

3.        Optic fiber is normally made from

a.        Coherent glass and xenon

b.        Copper

c.        Water

d.       Silica glass or plastic

4.        The following are the advantages of optical fiber system except

a.        Greater capacity

b.        Crosstalk immunity

c.        Safer to handle

d.       Lower initial cost of installation

5.        Plastic fibers have the following advantages over glass fibers except

a.        Flexibility

b.        Ease of installation

c.        Ruggedness

d.       Low attenuation

6.        This explains how a light may react when it meets the interface of two transmission materials that have different indices of refraction.

a.        Huygens' Law

b.        Nyquist's Theorem

c.        Snell's Law

d.        Quantum Theory

7.        In Optical fibers,

a.        The core and cladding have the same index of refraction

b.        The core and cladding have the same area

c.        The core surrounds the cladding

d.       The cladding surrounds the core

8.        A type of fiber whereby light rays take many paths between the source and the receiver.

a.        Monomode

b.       Multimode

c.        Single mode

d.        Step index

9.        A figure of merit used to measure the light gathering or light collection ability of the optical fiber.

a.        Acceptance angle

b.       Numerical aperture

c.        Acceptance cone

d.        Critical angle

10.     The basic optical fiber communications system consists of the following except

a.        Optical source

b.        Photodetector

c.        Transmission medium

d.       48 v power supply

11.     Optical fibers can be made out of

a.        Glass

b.        Plastic

c.        Combination of both

d.       Any of these

12.     In ________, the core has an index of refraction that changes continuously from the center to the outside.

a.        Step index

b.       Graded index

c.        Monomode

d.        Multimode

13.     The following are causes of attenuation and loss of optical power within the fiber except

a.        Microbending loss

b.        Connector loss

c.        Splicing loss

d.       Ohmic loss

14.     For a signal to be propagated through the optical fiber, the angle of incidence should be________ the critical angle.

a.        Greater than

b.        Less than

c.        Equal to

d.        None of these

15.     A ray of light in a transparent material of refractive index 1.5 is approaching a material with a refractive index of 1.48. At the boundary, the critical angle is

a.        90 degrees

b.        9.4 degrees

c.        75.2 degrees

d.       80.6 degrees

16.     The first material has a refractive index of 1.51 and the angle of incidence is 38 degrees and the second material has a refractive index of 1.46. What is the angle of refraction?

a.        30.55 degrees

b.       39.55 degrees

c.        75.2 degrees

d.        40.55 degrees

17.     If the refractive index of the core of an optic fiber was 1.47 and that of the cladding was 1.44,the cone of acceptance would have an angle of approximately

a.        17.19 degrees

b.        72.82 degrees

c.        78.4 degrees

d.       34.36 degrees

18.     In free space, light travels at approximately

a.        186000 m/sec

b.        3 x 10exp9 m/sec

c.        300 m/sec

d.       0.3m/nsec

19.     Scattering loss is caused by

a.        Insufficient stirring of the ingredients during manufacture

b.        Changes in the density of the fiber due to uneven rates of cooling

c.        Microscopic cracks in the cladding which allow leakage of the vacuum in the core

d.       Impurities in the fiber

20.     Cleaving is the process of

a.        Removing the cladding before connecting fibers together

b.       Cutting the end of the fiber in preparation for connecting two fibers

c.        Cleaning the surface of optic fibers

d.        Inspecting fibers for flaws

21.     A typical value of insertion loss for a mechanical splice

a.        -50 dB

b.       0.2 dB

c.        12 mm

d.        3 dB

22.     The speed of light in a transparent material

a.        Is always the same regardless of the material chosen

b.       Is never greater than the speed of light in free space

c.        Increases if the light enters a material with a higher refractive index

d.        Is slowed down by a factor of 1 million within the first 60 meters

23.     The following are light detectors in fiber optic communications system except

a.        ILD

b.        PIN diode

c.        APD

d.        None of these

24.     The following are three distinct regions of an optical fiber except

a.        Core

b.        Cladding

c.        Jacket

d.        Coating

25.     The maximum angle in which external light rays may strike the air fiber interface and still propagate down the fiber

a.        Critical angle

b.       Acceptance angle

c.        Numerical aperture

d.        Beamwidth

26.     Which of the following combinations is impossible for optical fibers?

a.        Plastic core and cladding

b.        Glass core and cladding

c.        Plastic core and glass cladding

d.        Glass core and plastic cladding

27.     The scientist who coined the term "Fiber Optics"

a.        Hopkins

b.        Hansel

c.        Kapany

d.        Van Heel

28.     A technology for carrying many signals of different capacities through a synchronous, flexible optical hierarchy.

a.        PDH

b.        SDH

c.        SONET

d.        ATM

29.     Two digital signals whose transmission occur at almost the same rate are

a.        Plesiochronous

b.        Synchronous

c.        Asyncronous

d.        Mesochronous

30.     SONET systems are

a.        Twisted pair copper based technology

b.       Fiber optic technology

c.        Hybrid fiber coax technology

d.        Wireless technology

31.     The band of light wavelengths that are too long to be seen by the human eye.

a.        Amber

b.        Visible

c.        Infrared

d.        Ultraviolet

32.     Which color has the shortest wavelength of light?

a.        Red

b.        Yellow

c.        Blue

d.        Green

33.     The loss of signal power as it travels down the fiber is called

a.        Dispersion

b.        Scattering

c.        Absorption

d.       Attenuation

34.     What is a specific path the light takes in an optical fiber, corresponding to a certain angle and number of reflections?

a.        Mode

b.        Grade

c.        Numerical aperture

d.        Dispersion

35.     The width of the range of wavelengths emitted by light source.

a.        Bandwidth

b.        Chromatic dispersion

c.        Spectral width

d.        Beamwidth

36.     Which theory states that light wave behaves as if it consists of many tiny particles?

a.        Huygens'

b.        Nyquist's

c.        Doppler's

d.       Quantum

37.     Fiber optic cables operate at frequencies near

a.        20 MHz

b.        200 MHz

c.        2 GHz

d.       800 THz

38.     When a beam of light enters one medium from another, which quantity will not change?

a.        Direction

b.        Speed

c.        Frequency

d.        None of these

39.     Dispersion caused by the difference in the propagation times of light rays that take different paths down the fiber.

a.        Material

b.        Wavelength

c.        Modal

d.        Delay

40.     A non-coherent light source for optical communications system.

a.        ILD

b.        LED

c.        APD

d.        PIN diode

41.     The numerical aperture of a fiber if the angle of acceptance is 15 degrees is

a.        0.17

b.       0.26

c.        0.50

d.        0.75

42.     Single frequency light is called

a.        Pure

b.        Intense

c.        Coherent

d.       Monochromatic

43.     What is the unit of light wavelength?

a.        Micron

b.       Angstrom

c.        Mils

d.        Fathom

44.     A high speed LAN defined by ANSI using fiber optic cables

a.        NTSC

b.        SDH

c.        FDDI

d.        SONET

45.     What is the process of using two or more light sources at different wavelengths each separately modulated with the same fiber?

a.        SDH

b.        FDM

c.        TDM

d.       WDM

46.     The European standard for synchronous transmission over fiber optic networks.

a.        NTSC

b.       SDH

c.        FDDI

d.        SONET

47.     What is the light source typically used in single mode optical fiber?

a.        Phototransistor

b.       Laser

c.        Photoresistor

d.        LED

48.     An OTDR is used for

a.        Fault location

b.        Splice and connector evaluation

c.        Loss per unit length measurement

d.       All of these

49.     The coupling loss due to angular deviation from the optimum alignment of source to the fiber optic cable

a.        Lateral misalignment

b.        Gap misalignment

c.        Angular misalignment

d.        Numerical aperture loss

50.     Which of the following is used to protect the core and the cladding of the fiber?

a.        Insulation

b.        Plastic

c.        Glass

d.       Kevlar strength members

51.     Determine the acceptance angle of light passing to a glass having a refractive index of 1.56 to ethyl having a refractive index of 1.51.

a.        17.7 degrees

b.        21.3 degrees

c.        23 degrees

d.        25 degrees

52.     Calculate the energy of the photon of infrared light energy at 1.55 um.

a.        1.28 x 10exp-19 J

b.        1.6 x 10exp19 J

c.        1.22 x 10exp-16 J

d.        1.9 x 10exp-14 J

53.     The amount of power per unit area in optical fiber is called

a.        Irradiance

b.        Radiance

c.        Reflectance

d.        Permeance

54.     Light at 1.55 um in air has what energy in eV?

a.        1.2 eV

b.        1 eV

c.        0.6 eV

d.       0.8 eV

55.     An object farther from a converging lens than its focal point always has an ____ image.

a.        Virtual

b.        The same in size

c.        Inverted

d.        Smaller size

56.     What parts of the body are most sensitive to laser damage?

a.        Hair

b.        Nails

c.        Eye and skin

d.        Teeth

57.     Who was the first person who actually produced laser light?

a.        Maiman

b.        Edison

c.        Einstein

d.        Volta

58.     One of the advantages of fiber optics which is referred to the volume of capacity of signals it can carry.

a.        Security

b.        Weight

c.        Bandwidth

d.        Physical size

59.     1 micron is equal to _____ meters.

a.        10exp-6

b.        10exp-12

c.        10exp-15

d.        10exp-18

60.     The small proportion of light scattered by Rayleigh scattering which is returned towards the source.

a.        Optoscatter

b.        Standing waves

c.        Return loss

d.       Backscatter

61.     Dispersion caused by different wavelengths contained in the transmitted light.

a.        Intermodal

b.       Chromatic

c.        Optical

d.        Any of these

62.     A ray that always passes through the core axis as it is propagated

a.        Axial

b.       Meridional

c.        Skew

d.        Direct

63.     The typical cladding diameter of an optical fiber

a.        8 um

b.        10 to 100 um

c.        125 um

d.        800 to 1550 um

64.     The typical core diameter of an optical fiber is

a.        8 um

b.       62.5 um

c.        125 um

d.        800 to 1550 um

65.     A reflection that occurs from a surface whenever there is a sudden change in the refractive index at the end of the fiber.

a.        Total internal

b.        Reflection loss

c.        Fresnel reflection

d.        Backscatter

66.     The first device used to transmit voice using light as a carrier

a.        Edison bulb

b.        Phonograph

c.        Photophone

d.        Lincompex

67.     An elementary quantity of radiant energy which can be considered as particles of light.

a.        Photons

b.        Lumens

c.        Electrons

d.        Optimons

68.     What is the wave or pulse that does not disperse or lose it’s shape as it propagates through a medium?

a.        Photon

b.        Coherent source

c.        Optimon

d.       Soliton

69.     Where can one found a fiber to detector connector?

a.        Transmitter

b.       Receiver

c.        LED circuit block

d.        Analog transmitter block

70.     What skin damage occurs when exposed to laser radiation?

a.        Erythema

b.        Hematoma

c.        Gout

d.        Eczema