Fibre Optics Overview and Applications

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Questions and Answers

What is the primary purpose of a fibre optic splice?

To join fibres without altering their structure

To reduce the size of the fibre bundle

To establish an optical connection between two fibres (correct)

To repair physical damage without changing performance

Which of the following describes an essential safety precaution when terminating optical fibres?

Wearing safety glasses to protect eyes from debris (correct)

Wearing gloves to prevent cuts from glass

Using basic hand tools for fibre alignment

Eating and drinking near the work area to stay energized

What kind of splicing technique uses localised heat to join optical fibres?

Thermal splicing

Laser splicing

Mechanical splicing

Fusion splicing (correct)

What is a key requirement for performing optical fibre termination tasks?

Approval and performance by qualified personnel Signup and view all the answers

What characterizes low-loss fibre splicing?

Efficient jointing methods and proper end preparation Signup and view all the answers

Which of the following is NOT a danger associated with cleaved optical fibres?

Electrical shock from exposed wires Signup and view all the answers

What is the primary goal of reducing fibre mismatches during fibre optic connections?

To minimize coupling losses Signup and view all the answers

What type of splice relies on mechanical fixtures for fibre alignment?

Mechanical splice Signup and view all the answers

What is a consequence of not observing the minimum bend radius for optical fibres?

Reduced system performance Signup and view all the answers

Which practice is essential before mating fibre optic connectors?

Clean the connectors Signup and view all the answers

What should never be done with fibre optic cables during installation?

Pull them tight Signup and view all the answers

Which of the following properties does NOT affect fibre optic system performance?

Connective heat Signup and view all the answers

Who should be allowed to install or repair fibre optic systems?

Only trained, authorised personnel Signup and view all the answers

What can result from placing heavy items on fibre optic cables?

Cable breakage or increased loss Signup and view all the answers

What is the effect of improper fibre optic connections on system performance?

Higher connection loss and potential damage Signup and view all the answers

What is the main purpose of fibre optic splices in a system?

To permit the transfer of optical power between components Signup and view all the answers

What is the primary function of the cladding in a fibre optic cable?

To create total internal reflection for minimizing light loss Signup and view all the answers

What method is used to send data through a fibre optic cable?

Turning a laser on and off to represent data Signup and view all the answers

What limits the distance that modern fibre optic cables can effectively transmit signals?

Signal attenuation over long distances Signup and view all the answers

What type of connectors do not rely on physical contact between optical fibres?

Expanded-beam connectors Signup and view all the answers

Which characteristic of fibre optic cables allows them to carry multiple signals simultaneously?

Implementation of multiplexing with lasers of different colors Signup and view all the answers

What is the primary purpose of fibre optic connectors?

To allow for repeated disconnects and reconnects without significant loss of light transmission Signup and view all the answers

What is the purpose of the equipment huts located along long-distance fibre optic lines?

To re-amplify and retransmit the signal at full strength Signup and view all the answers

How does the construction of a fibre optic cable minimize light losses?

By utilizing total internal reflection provided by the cladding Signup and view all the answers

What is the role of an alignment sleeve in ferrule connectors?

To align the ferrules for proper fibre contact Signup and view all the answers

What material is primarily used to construct a fibre optic cable?

Glass that is highly pure Signup and view all the answers

What material is typically used to bond fibres within ferrules?

Epoxy resin Signup and view all the answers

Which type of connector aligns and brings the ends of two fibres into contact?

Butt-jointed connectors Signup and view all the answers

Which factor plays a crucial role in the performance of a fibre optic system?

The number of lasers involved in sending data Signup and view all the answers

What feature is crucial for maintaining fibre alignment in ferrule connectors?

Precision holes within the ferrules Signup and view all the answers

What type of connection is achieved through ferrule connectors?

Low-loss optical connection Signup and view all the answers

What mechanism typically locks ferrules into the alignment sleeve?

Threaded outer shell or similar mechanism Signup and view all the answers

What component is responsible for converting the optical signal back to an electrical signal in a fiber optic receiver?

Optical detector Signup and view all the answers

What undesirable characteristic results from variations of the signal at the receiver end in fiber optic communication?

Distortion Signup and view all the answers

Which device in a fiber optic receiver is typically responsible for amplifying the electrical signal?

Post amplifier Signup and view all the answers

What is the primary function of a semiconductor photodiode in fiber optic systems?

To convert photons into electrical current Signup and view all the answers

What is the output signal suitability issue associated with simple fiber optic receivers?

Not in suitable form for interfacing Signup and view all the answers

What does the term 'photocurrent' refer to in the context of an optical detector?

An electrical current proportional to optical intensity Signup and view all the answers

What additional components are generally included in a fiber optic receiver to enhance the output signal?

Amplifiers and additional circuitry Signup and view all the answers

Which process in fiber optics leads to the weakening and distortion of signals during propagation?

Scattering, absorption, and dispersion Signup and view all the answers

What is the primary role of a fibre optic transmitter in communication systems?

To convert electrical signals into optical signals and launch them into fibre Signup and view all the answers

Which type of light source is primarily used in fibre optic systems?

Semiconductor LEDs and Laser Diodes Signup and view all the answers

How can lenses improve the coupling of light from the source to the optical connector?

By focusing and directing the light more efficiently Signup and view all the answers

What aspect of fibre optic data link performance is crucial for effective communication?

The optical power (light) launched into the optical fibre Signup and view all the answers

What packaging forms are typically used for the simplest fibre optic transmitters?

Transistor Outline (TO) cans or Dual Inline Packages (DIPs) Signup and view all the answers

What is the main function of optical pigtails in fibre optic systems?

To attach the transmitter optical source to the output connectors Signup and view all the answers

What distinguishes semiconductor lasers from LEDs in fibre optic applications?

They have higher efficiency and output power Signup and view all the answers

What possible connection method can be used between the optical source and the optical connector?

Coupling via an intermediate optical fibre Signup and view all the answers

Study Notes

Fibre Optics (5.10) Learning Objectives

List fibre optic handling and installation precautions
Describe advantages and disadvantages of fibre optic data transmission over electrical wire propagation (Level 2)
Describe the fibre optic data bus (Level 2)
Describe fibre optic related terms (Level 2)
Describe fibre optic connectors and terminations (mechanical and fusion splice) (Level 2)
Describe fibre optic couplers, control terminals, and remote terminals (Level 2)
Describe the application of fibre optics in aircraft systems (Level 2)

Common Fibre Optic Technology Terms

Numerical Aperture (NA): Defines which light will be propagated by total internal reflection; light entering from outside the cone will not be propagated. High NA gathers more light, but lowers the bandwidth, while a small NA tends to give the fibre a higher bandwidth.
Attenuation: Loss of power during transit, measured in decibels per kilometre (dB/km).
Dispersion: General term for phenomena causing broadening or spreading of light.

Optical Fibre Cables

Imagine a pipe coated with a perfect mirror inside. Light reflects off the sides, allowing communication. This is the essence of a fibre optic cable.
Optic fibre is a glass cable with comparable thickness to a human hair.

Fibre Optic Cables

Made of glass, incredibly pure for transmission.
Extremely thin.
Coated with plastic for mirror-like effect.
Light enters and bounces off, remaining inside.

Optical Fibre Communications System

Converts electrical signals to optical signals.
Transmits optical signals through fibre.
Converts optical signals back to electrical signals.
Components include transmitter, optical fibre, and receiver.
Transmitter (converts electrical to optical—uses LEDs/lasers)
Receiver (converts optical to electrical—uses an optical detector.)

Basic Structure of an Optical Fibre

Core: Cylindrical dielectric material (no electricity).
Cladding: Layer around the core, made of dielectric material (lower refractive index than core).
Coating/Buffer: Outer layer, protective.

Fibre Optic Cable Losses

Attenuation: Loss of optical power (due to absorption, scattering, bending).
Absorption: Conversion of optical power to energy form; caused by imperfections or impurities.
Scattering: Light interacting with density fluctuations.
Bending losses: Micro-bend (small dents) and macro-bend (sharp changes in direction).

Fibre Optic Couplers and Remote Terminals

Fibre Optic Couplers: Combine/distribute optical signals between fibres.
Types: optical splitter (splits input into multiple outputs), optical combiner (combines multiple inputs into a single), and an X-coupler (combines splitting and combining functions).

Optical Sources and Fibre Optic Transmitters

Converts electrical to optical signals.
Uses LEDs (less expensive) or lasers (more expensive but higher bandwidth) as light sources.

Optical Detectors and Fibre Optic Receivers

Converts optical signals to electrical form.
Semiconductor photodiodes are commonly used in receivers.

Optical Fibre Data Bus for Aircraft Systems

Advantages: Lighter, smaller, less attenuation, immunity to EMI, wide bandwidth, lower cost, corrosion resistance
Disadvantages: Stringent coupling, special techniques/equipment required, ultra-clean environment needed.

Aircraft Applications of Optical Fibre

Replacing coaxial cables in avionics.
Facilitating simultaneous transmission of multiple signals over one fibre.
Offering higher bandwidth and immunity to EMI.
Being featured in new fuel measurement systems (and others).

Fibre Optics Gyroscopes

Detects aircraft movement in pitch, roll, and yaw axes.
Uses fibre optic cable and sensors.
Provides very accurate navigation data. No moving parts.

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Description

This quiz covers key concepts of fibre optics, including handling precautions, advantages over electrical wires, and essential terminology. It also explores fibre optic connectors, couplers, and their applications in aircraft systems. Enhance your understanding of fibre optic technology and its significance in modern applications.