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LVL 4 ELEC > J2LT4 Fiber-Optic > Flashcards

J2LT4 Fiber-Optic Flashcards

1
Q

What are the 4 main components of a basic fiber-optic system?

A

Transmitter
Fiber-optic cable
Optical Connectors
Receiver

LT4 PG.85

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2
Q

What is the purpose of fiber-optic?

A

To transmit data from one location to another using light.

LT4 PG.85

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3
Q

What is the purpose of the transmitter?

A

To convert an electrical signal in to a light signal.

LT4 PG.85

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4
Q

How does the transmitter convert an electrical signal to a light signal?

A

By using a drive circuit to convert the input signal in to a form that will operate the optical source, the optical source then converts that to light.

LT4 PG.85

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5
Q

What would be an optical source in a transmitter?

A

A light-emitting diode (LED) or laser

LT4 PG.85

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6
Q

What is the basic construction of optical fiber?

A

Inner core - carries the light
Cladding - reflective covering placed over the core
Buffer - protective coating for the cable

LT4 PG.85

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7
Q

The most widely used fibers are constructed of _____.

A

Glass

LT4 PG.85

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8
Q

When losses are not a concern in short communication runs, fibers may be constructed from ____.

A

Plastic

LT4 PG.85

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9
Q

The purpose of optical connectors is?

A

To terminate the fiber at the transmitter / receiver with as few power losses as possible.

LT4 PG.85

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10
Q

The purpose of the receiver is to?

A

To accept the light signal and convert it back in to an electrical signal.

LT4 PG.86

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11
Q

What components does a receiver consist of?

A

An optical detector to convert light signals in to electrical signals and the electronic circuitry needed to amplify the output signal.

LT4 PG.86

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12
Q

Light is commonly expressed as a wavelength in _____.

A

Nanometers.

LT4 PG.86

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13
Q

What is the range in nanometers of visible light?

A

380 nm to 780 nm.

LT4 PG.86

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14
Q

Most fiber-optic systems use infrared light, what is the wavelength range of infrared light?

A

800 nm to 1500 nm.

LT4 PG.86

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15
Q

Refraction plays an important part in the design of fiber-optic cables. What is it and how does it happen?

A

The bending of light. As light travels from one material to another, it changes velocity which results in the light changing its direction/angle of travel.

LT4 PG.86

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16
Q

What is a photon?

A

A light particle, similar to an electron.
It represents a certain amount of energy and is used to determine the wavelength of light.

LT4 PG.86

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17
Q

A high range of transmission frequencies is called….

A

Wide bandwidth.

LT4 PG.87

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18
Q

What is multiplexing?

A

Putting two or more signals into a single channel.

LT4 PG.87

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19
Q

What is attenuation?

A

Power loss.
A loss in strength as a signal travels along a transmission path.

LT4 PG.87

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20
Q

Optical fiber is dielectric meaning it is not affected by….

A

Ordinary electromagnetic fields.

LT4 PG.87

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21
Q

What are the advantages of fiber-optics?

A 
Wide bandwidth
Low loss
Electro-magnetic immunity 
Light weight 
Small size 
Safety and electrical isolation

LT4 PG.87

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22
Q

What are some factors that the characteristics of light propagation through a fiber depend on?

A

Size of fiber
Composition of fiber
Light injected into the fiber

LT4 PG.88

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23
Q

Glass used for fibers is ultra pure, transparent silicon dioxide or fused quartz. Why would impurities purposefully be added?

A

To achieve desired index of refraction.

LT4 PG.88

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24
Q

What is Plastic-clad silica?

A

PCS fiber is a compromise between glass and plastic fibers by using a high quality glass core and an inexpensive plastic cladding.

LT4 PG.88

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25
Q

Which fiber is the least expensive and works best in a range of visible light?

A

Plastic Fibers.

LT4 PG.88

26
Q

Optical fiber size is made up of 2 numbers, what would 50/125 tell you?

A

Core is first, 50 micrometers
Cladding is second, 125 micrometer diameter

LT4 PG.88

27
Q

A micrometer is sometimes referred to as?

A

Micron

LT4 PG.89

28
Q

What are the 4 most common size of optical fibers?

A

8 / 125
50 / 125
62.5 / 125
100 / 140

LT4 PG.89

29
Q

What are the fundamental parts fiber-optic cable?

A 
Outer Jacket 
Strength members
Buffer 
Primary coating
Cladding
Core

LT4 PG.89 Fig 6.

30
Q

What are the two types of buffer that may be used?

A

Loose buffer
Tight buffer

LT4 PG.89

31
Q

Construction of loose buffer

A

Fiber is contained inside hard plastic tube
One or more fibers may be within the same tube
Tube is often filled with gel

LT4 PG.90

32
Q

construction of tight buffer

A

Plastic jacket is bonded directly to the fiber

LT4 PG.90

33
Q

What does the gel within the loose buffer do?

A

Keeps moisture out
Cushions glass fibers against mechanical forces
Fiber is less effected by the expanding and contracting of the cable during severe temperature changes

LT4 PG.90

34
Q

Where is a tight buffer limited to in its use, and why?

A

Generally limited to indoor use.
During temperature variation, the plastic and the fibers expand and contract at different rates. this can result in microbends.

LT4 PG.90

35
Q

Materials added to the cable to increase tensile strength are called?

A

Strength members.

LT4 PG.91

36
Q

Common strength members are?

A

Kevlar
Steel
Fiberglass

LT4 PG.91

37
Q

Strength members may also serve as what?

A

load bearing members for optical cable.

LT4 PG.91

38
Q

What does the jacket do?

A 
Provides protection to the cable against: 
abrasion 
acids
oil
water

LT4 PG.91

39
Q

What are common jacket materials?

A

PVC
Polypropylene
Nylon
Teflon

LT4 PG.91

40
Q

These cables contain no metal and no other electrical conductive members.

A

Nonconductive cables.

LT4 PG.91

41
Q

These cables contain non current carrying conductive parts

A

Conductive cables

LT4 PG.91

42
Q

These cables contain both optical fiber cables and current carrying electrical conductors.

A

Hybrid cables

LT4 PG.91

43
Q

Common applications for outdoor cables include

A

Overhead cables
Direct burial cables
Indirect burial cables
Submarine cables

LT4 PG.93

44
Q

steps for installing fiber-optic cables

A 
1- survey run and choose best path 
2- test cable before and after pulling
3- treat cable with care
4- do not exceed minimum bend radius
5- do not exceed maximum allowable tensile load
6- leave extra at beginning and end
7- document installation

LT4 PG.95-96

45
Q

General rule for bending optic cable?

A

Do not bend tighter than:

  • 20 times outer cable diameter during pull
  • 10 times outer cable diameter after installation

LT4 PG.95

46
Q

What is the general pull strength rating of most cables designed for outdoor use?

A

600 lb

LT4 PG.96

47
Q

What section of the CEC deals with optical fiber installation?

A

Section 56

LT4 PG.96

48
Q

We can group optical fiber cables in to three types, what are they?

A

Non-conductive
Conductive
Hybrid

Rule 56-102
LT4 PG.97

49
Q

What is the purpose of a connector?

A

To join one fiber source, a detector, or another fiber.

LT4 PG.98

50
Q

What convenience does a connector offer?

A

It allows repeated connection and disconnection of devices.

LT4 PG.98

51
Q

What are the two basic types of splices?

A

Fusion
Mechanical

LT4 PG.98

52
Q

Fusion splices are made by…

A

Positioning two properly prepared fiber ends and applying an electric arc to fuse the ends together.

LT4 PG.98

53
Q

Mechanical splices are made by…

A

Using sleeve type connectors placed over prepared fiber ends. gels and adhesives provide continuous optical path between the two fibers.

LT4 PG.100

54
Q

Which splice provides extremely low losses?

A

Fusion splices

LT4 PG.98

55
Q

Which splice has higher losses?

A

Mechanical splice.

LT4 PG.100

56
Q

Which type of splice is often used to make temporary fiber connections?

A

Mechanical splices.

LT4 PG.100

57
Q

As the frequency of a waveform increases does the wavelength increase or decrease?

A

Decrease

Self-Test 4

58
Q

What does the term attenuation mean?

A

A power loss that occurs as a signal travels over a distance.

Self-Test 4

59
Q

What is an important safety precaution to observe when working with fiber-optic systems?

A

Never look directly into a light source or into the end of a fiber.

Self-Test 4

60
Q

Which 2 layers cannot be separated in the fundamental layers of an optical fiber?

A

The core and cladding.

Self-Test 4

61
Q

What are three hazards of working with optical-fiber cables?

A

Loose fiber - fiber can penetrate skin and eyes, transported through body by blood
Solvents and cleaners - often inflammable or noxious
Laser Operation - UV light can cause eye damage

Self-Test 4

62
Q

What must be done to fiber after you glue it into a connector with epoxy?

A

Grind and polish it.

Self-Test 4

LVL 4 ELEC (8 decks)

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