Fiber Optics Quiz

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Questions and Answers

How does a light signal travel down a fiber optic cable?

By traveling through the air inside the cable.

By being conducted as electricity along the cable.

By being absorbed and re-emitted by the cable's material.

By reflecting off the side walls of the cable. (correct)

What happens when light travels from one medium to another of a different density?

It is reflected back to the original medium.

It changes direction. (correct)

It is absorbed by the new medium.

Its speed remains constant.

What is the primary factor determining the angle of refraction of a light wave?

The thickness of the fiber optic cable.

The wavelength of the light. (correct)

The distance travelled by the light.

The intensity of the light source.

What is the typical wavelength range of light used in fiber optic cables?

600-1600 nm (A) Signup and view all the answers

What is the purpose of using different frequencies of light for different signals in fiber optic cables?

To allow multiple signals to be transmitted simultaneously. (A) Signup and view all the answers

What is the role of a fiber optic receiver in the transmission of signals?

It converts the light signal back into an electrical signal (C) Signup and view all the answers

What are the two main modes of light propagation in fiber optic cables?

Single-mode and multimode. (B) Signup and view all the answers

What is the primary feature that distinguishes single-mode fiber from graded-index (multimode) fiber?

The size of the core (C) Signup and view all the answers

What is the key advantage of using fiber optic cables over traditional copper cables for data transmission?

Higher bandwidth and data transmission speeds. (D) Signup and view all the answers

When light travels through a fibre optic cable, what causes a reduction in the light's power?

Attenuation (D) Signup and view all the answers

Which of the following is a measure of the light-gathering ability of a fibre optic cable?

Numerical Aperture (D) Signup and view all the answers

What is the phenomenon that causes light to spread as it propagates through an optical fibre?

Dispersion (A) Signup and view all the answers

How is attenuation in fibre optic cables typically measured?

Decibels per kilometre (A) Signup and view all the answers

Which type of fibre optic cable experiences the lowest attenuation?

Single-mode fibre (B) Signup and view all the answers

Which of the following is NOT a common fibre optic technology term?

Modulation (A) Signup and view all the answers

Which of the following best describes the principle behind a fibre optic cable sending information?

Light pulses are reflected along the inner surface of the cable. (C) Signup and view all the answers

What is radiance in the context of optical sources?

The amount of optical power emitted in a specific direction per unit time by a unit area. (C) Signup and view all the answers

Which term can be used as an alternative for a fibre optic transmitter?

Control Terminal (A) Signup and view all the answers

Which of the following is a benefit of using optical fibre cables instead of copper wires in aircraft systems?

Reduction of crosstalk (B) Signup and view all the answers

How does optical fibre communication compare to traditional methods in terms of electromagnetic interference?

Optical fibres are less affected by EMI. (D) Signup and view all the answers

What is a fibre pigtail?

A short length of optical fibre permanently fixed to a source or detector. (C) Signup and view all the answers

What is the primary structural difference between single-mode and multimode fibres?

The diameter of the core (D) Signup and view all the answers

Which of the following statements about single-mode fibres is true?

They have a diameter of 9 μm. (D) Signup and view all the answers

What advantage do multimode fibres have over single-mode fibres?

Easier core-to-core alignment during splicing (A) Signup and view all the answers

Which light source is typically used with single-mode fibres?

Laser diodes (D) Signup and view all the answers

What is modal dispersion in multimode fibres?

The varying arrival times of modes at the fibre end (A) Signup and view all the answers

What causes attenuation in optical fibres?

Scattering, absorption, and bending losses (D) Signup and view all the answers

Which characteristic of single-mode fibres contributes to their higher information capacity?

Reduced core diameter (C) Signup and view all the answers

What is a common disadvantage of multimode fibres?

They experience greater modal dispersion. (D) Signup and view all the answers

What defines the number of modes that can propagate in multimode fibres?

Core size and Numerical Aperture (NA) (C) Signup and view all the answers

Why are LEDs often preferred for multimode fibres?

They are cheaper, less complex, and more durable. (D) Signup and view all the answers

What is the primary function of ferrule connectors?

They lock ferrules into the alignment sleeve using a threaded outer shell. (C) Signup and view all the answers

In expanded-beam coupling, how does fibre separation and lateral misalignment compare to butt-jointing?

They produce lower coupling loss than in butt-jointing. (C) Signup and view all the answers

What aspect of alignment is more critical in expanded-beam connectors compared to butt-jointing?

Angular misalignment (A) Signup and view all the answers

Which of the following applications is NOT commonly associated with expanded-beam connectors?

Point-to-point fibre links (C) Signup and view all the answers

What characteristic makes expanded-beam connectors more challenging to produce?

They involve intricate lens systems for light manipulation. (B) Signup and view all the answers

What is the function of a fibre optic coupler?

To redistribute optical signals among fibres. (A) Signup and view all the answers

What type of coupling mechanism is used by ferrule connectors?

Threaded outer shell or a different coupling mechanism (C) Signup and view all the answers

Which of the following statements about fibre optic couplers is accurate?

They can redistribute signals among multiple fibres. (B) Signup and view all the answers

Why is angular misalignment a concern in expanded-beam connectors?

It results in higher coupling loss. (C) Signup and view all the answers

What is a significant advantage of using expanded-beam connectors over butt-jointing?

They allow for greater variability in fibre separation without significant loss. (D) Signup and view all the answers

Study Notes

Fibre Optics (5.10) Learning Objectives

List fibre optic handling and installation precautions
Recall the advantages and disadvantages of fibre optic data transmission over electrical wire propagation (Level 1)
Identify a fibre optic data bus (Level 1)
Recall fibre optic related terms (Level 1)
Identify fibre optic connectors, mechanical and fusion splice terminations (Level 1)
Identify fibre optic couplers, control terminals, and remote terminals (Level 1)
Recall applications of fibre optics in aircraft systems (Level 1)

Common Fibre Optic Technology Terms

Numerical Aperture (NA) defines which light will be propagated and which will not.
Attenuation is the loss of power during transit, measured in decibels per kilometre (dB/km).
Dispersion refers to phenomena that cause a broadening or spreading of light as it propagates.

Optical Fibre Cables

Imagine a flexible plastic pipe with a mirrored interior; light reflects off the sides, allowing communication.

Fibre Optic Technology

Fibre optics is a glass cable enabling light transmission, comparable in thickness to human hair.
Coating the glass in plastic creates a mirror effect, minimizing light loss.

Optical Fibre Communications System

Fibre optic data links convert electrical signals into optical signals, send them through fibre, and convert them back to electrical signals.
Components include transmitter, optical fibre, and receiver.
Transmitter converts electrical to optical, receiver converts optical to electrical (usually using LEDs or laser diodes).

Basic Structure of an Optical Fibre

Consists of core, cladding, and coating.
Coating protects from damage; cladding has a lower refractive index than the core (critical for total internal reflection).
Light propagates within the core by continual reflection.

Fibre Optic Cable Losses

Attenuation is the loss of optical power as light travels through the fibre. This can result from absorption (conversion to other energy forms like heat), scattering (light interaction with density fluctuations) and bending (micro/macro bends causing light leakage).

Bending Losses

Microbends: microscopic bends, often caused by cabling issues, increasing loss.
Macrobends: sharp bends causing light loss to higher-order modes.

Dispersion

Dispersion is when the optical pulse spreads, reducing system bandwidth (information carrying capacity).
Various propagation modes and refractive index variations cause this spreading.

Fibre Optic Cable Handling Precautions

Never look directly into a fibre optic cable or connector.
Don't place heavy items on the cable.
Keep protective caps on unplugged connectors.
Avoid tight bends or sharp corners.
Ensure connections are clean.
Avoid crushing and kinking the cable.
Only trained personnel should handle the installation/repair of fibre optic systems.

Fibre Optic Terminations (Splices and Connectors)

Fibre optic splices are permanent connections between fibres (mechanical or fusion).
Mechanical splices use alignment fixtures and materials; are stable and less expensive.
Fusion splices melt fibre ends together - more complex but usually more efficient.
Fibre optic connectors allow disconnection of fibres without significant light loss.

Fibre Optic Couplers and Remote Terminals

Fibre optic couplers combine or divide optical signals among multiple fibres. This enables signal redistribution.
Couplers can be either passive (physical joining) or active (electrical conversion).
Optical splitters/combiners/X-couplers divide/combine optical signals.
Terminals have fibre pigtails (short lengths of fibre) and usually have connectors.

Aircraft Applications of Optical Fibre

Fibre optic data buses have advantages over coaxial cable such as, weight and space savings, immunity to electromagnetic interference, lower attenuation, wider bandwidths, lower costs, and better safety features.
Used in aircraft for systems such as flight control, fuel monitoring, and data recording.
Fibre optic gyroscopes are a vital part of aircraft navigation systems by measuring the aircraft's orientation and movement.

Disadvantages of Fibre Optic Data Communication

Stringent coupling requirements (precise connections are needed for efficient signal transfer).
Need for special techniques and equipment.
Need for specialised clean and precise work environments to avoid pollution from particle interference.

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Description

Test your knowledge on how light signals travel through fiber optic cables. This quiz covers key concepts such as light propagation, refraction, and advantages of fiber optics over traditional cables. Dive deep into the specifics of single-mode vs multimode fibers and their applications.