Twisted Pair Technology Overview

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Questions and Answers

What is the primary material used in ultrapure fibers to achieve low losses?

Composite materials

Plastic

Multicomponent glass

Ultrapure fused silica (correct)

What characteristic of optical fibers allows them to achieve much higher data rates compared to coaxial cables?

Their larger core diameter

Their immense potential bandwidth (correct)

Their cylindrical shape

Their plastic construction

Which section of an optical fiber cable is responsible for confining light within the cable?

The jacket

The core

The cladding (correct)

The outer sheath

Why is plastic fiber considered more economical compared to other types of optical fibers?

It is easier to manufacture. Signup and view all the answers

What is one of the advantages of optical fibers over twisted pair cables in terms of physical characteristics?

Smaller size and lighter weight Signup and view all the answers

What protects the optical fiber from environmental hazards such as moisture and abrasion?

The jacket Signup and view all the answers

How does the diameter of the core in optical fibers typically range?

8 to 50 µm Signup and view all the answers

What property differentiates the cladding from the core in an optical fiber?

Optical properties Signup and view all the answers

What is the primary structure of a coaxial cable?

A hollow outer conductor surrounding a single inner wire conductor Signup and view all the answers

Which application is NOT typically associated with coaxial cable?

High-frequency optical data transmission Signup and view all the answers

What is a significant advantage of coaxial cable over twisted pair cables?

Lower attenuation at higher frequencies Signup and view all the answers

What component is necessary for long-distance transmission of analog signals over coaxial cable?

Amplifiers every few kilometers Signup and view all the answers

What is the diameter range of a single coaxial cable?

1 to 2.5 cm Signup and view all the answers

What type of signals can coaxial cable transmit?

Both analog and digital signals Signup and view all the answers

Which of the following is a disadvantage of using coaxial cables?

The need for amplifiers or repeaters for long distances Signup and view all the answers

What materials can be used to construct optical fibers?

Various glasses and plastics Signup and view all the answers

What phenomenon allows optical fiber to transmit signals effectively?

Total internal reflection Signup and view all the answers

Which type of optical fiber transmission allows for only a single mode to pass?

Single-mode transmission Signup and view all the answers

What is a characteristic feature of graded-index multimode transmission?

It has a higher refractive index at the center than at the edges. Signup and view all the answers

Which type of optical fiber is typically used for long distance applications?

Single-mode Signup and view all the answers

What happens to light rays that enter the optical fiber at shallow angles?

They are reflected and propagated along the fiber. Signup and view all the answers

What is the primary role of the optical fiber core?

To serve as a waveguide for light signals Signup and view all the answers

How does the graded-index multimode transmission reduce travel distance for light?

By slowing axial rays compared to those near the cladding Signup and view all the answers

What is a primary advantage of optical fibers over coaxial cables?

Electromagnetic isolation Signup and view all the answers

What distinguishes single-mode transmission from multimode transmission?

It can avoid distortion due to having a single transmission path. Signup and view all the answers

What is commonly true about the repeater spacing in optical fiber systems?

Tens of kilometers are typically standard Signup and view all the answers

Which application of optical fiber typically has the longest average length?

Long-haul trunks Signup and view all the answers

What characteristic of optical fiber provides a high degree of security from interception?

Inherent difficulty to tap Signup and view all the answers

How many voice channels can metropolitan trunking circuits support on average?

100,000 Signup and view all the answers

Which statement about fiber optic networks is accurate regarding data capacity?

They can support thousands of stations simultaneously Signup and view all the answers

What does lower attenuation in optical fibers mean compared to other cable types?

More consistent performance over distance Signup and view all the answers

What is a notable feature of optical fibers in terms of energy?

They do not radiate energy Signup and view all the answers

Which of the following data rates is commonly associated with twisted pair connections to a digital PBX within a building?

64 kbps Signup and view all the answers

What type of noise is easily picked up by twisted pair cabling due to its physical characteristics?

Impulsive noise Signup and view all the answers

What is a primary drawback of twisted pair compared to other transmission media like coaxial cable and optical fiber?

Limited distance Signup and view all the answers

What is one advantage of using unshielded twisted pair (UTP) for local area networks?

It is the least expensive transmission medium. Signup and view all the answers

Repeaters are required every 2 or 3 km for which type of transmission on twisted pair?

Both analog and digital transmission Signup and view all the answers

What type of twisted pair is subject to external electromagnetic interference?

Unshielded twisted pair Signup and view all the answers

Which method is effective in reducing crosstalk in twisted pair cables?

Employing different twist lengths in adjacent pairs Signup and view all the answers

Twisted pair is the most common medium used for which type of signaling?

Both analog and digital signaling Signup and view all the answers

Study Notes

Twisted Pair

Common uses:
- Digital signaling
- Connections to digital data switches and PBXs within buildings (data rate: 64 kbps)
- Local area networks supporting personal computers within buildings (data rate: 100 Mbps)
Cost: Less expensive than coaxial cable and optical fiber.
Transmission characteristics:
- Can transmit both analog and digital signals.
- Analog signals require amplifiers every 5-6 km.
- Digital signals require repeaters every 2-3 km.
- Limited in distance, bandwidth, and data rate compared to coaxial cable and optical fiber.
- Strong attenuation with frequency.
- Susceptible to interference and noise due to easy coupling with electromagnetic fields (e.g., 60 Hz energy from power lines).
- Impulse noise easily intrudes.
Measures to reduce impairments:
- Shielding with metallic braid or sheathing reduces interference.
- Twisting wire reduces low-frequency interference.
- Different twist lengths for adjacent pairs reduce crosstalk.

Coaxial Cable

Applications:
- Television distribution
- Long-distance telephone transmission
- Short-run computer system links
- Local area networks
Transmission characteristics:
- Transmits both analog and digital signals.
- Superior frequency characteristics compared to twisted pair, enabling higher frequencies and data rates.
- Less susceptible to interference and crosstalk than twisted pair due to shielded, concentric construction.
- Principal constraints on performance: attenuation, thermal noise, and intermodulation noise.
- Analog signal transmission requires amplifiers every few kilometers, with closer spacing for higher frequencies.
- Digital signaling requires repeaters every kilometer or so, with closer spacing for higher data rates.

Optical Fiber

Physical description:
- Thin and flexible medium, guiding an optical ray.
- Made of glass or plastic.
- Ultrapure fused silica offers lowest losses, but is difficult to manufacture.
- Multicomponent glass fibers are more economical and provide good performance.
- Plastic fiber is even less expensive and suitable for short-haul links.
Components:
- Core: Inner section, consisting of glass or plastic fibers (8-50µm diameter).
- Cladding: Surrounds the core, has different optical properties to reflect light back into the core (125µm diameter).
- Jacket: Outermost layer, protects against moisture, abrasion, crushing, and other environmental factors.
Applications:
- Advantages over twisted pair and coaxial cable:
  - Greater capacity: High bandwidth and data rates (hundreds of Gbps over tens of kilometers demonstrated), compared to coaxial cable (hundreds of Mbps over 1 km) and twisted pair (few Mbps over 1 km or up to 100 Mbps to 10 Gbps over few tens of meters).
  - Smaller size and lighter weight: More compact and easier to install in confined spaces.
  - Lower attenuation: Less signal degradation over long distances.
  - Electromagnetic isolation: Not affected by external electromagnetic fields, making it resistant to interference, impulse noise, and crosstalk; also secures against eavesdropping.
  - Greater repeater spacing: Longer distances between repeaters, reducing cost and errors.
Application Categories:
- Long-haul trunks: High capacity routes (20,000-60,000 voice channels) averaging 1500 km in length.
- Metropolitan trunks: Shorter routes (12 km average) with high capacity (up to 100,000 voice channels).
- Rural exchange trunks: Connect towns and villages (40-160 km length).
- Subscriber loops: Connect central exchange directly to subscribers.
- Local area networks: Support hundreds to thousands of stations in buildings, with total capacity of 100 Mbps to 10 Gbps.
Transmission characteristics:
- Transmits signal-encoded beam of light through total internal reflection.
- Acts as a waveguide for frequencies in the infrared and visible spectra.
- Types of transmission:
  - Step-index multimode: Multiple angles of light rays, resulting in distortion.
  - Single-mode: Only one angle of light ray (axial ray), eliminating distortion, ideal for long distances (e.g., telephone, cable television).
  - Graded-index multimode: Varying refractive index in the core, light rays helically curve, reducing travel distance.

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Description

Explore the characteristics and uses of twisted pair cables in networking. This quiz covers aspects such as digital signaling, cost comparisons, transmission limitations, and measures to reduce impairments. Test your understanding of this fundamental technology in local area networks.