Transmission Media Flashcards
1
Q
Design Factors
A
- bandwidth
- transmission impairments
- number of receivers
2
Q
Twisted Pair
basic
A
- two metallic copper wires, twisted after a given step
- separately insulated
- often bundled into cables
- usually installed in building during construction
3
Q
Twisted Pair
kinds
A
- STP (Shield Twisted Pair) - protective shield for each pair and global shield for whole cable - reduces interference but increased weight
- FTP (Foiled Twisted Pair) or ScTP (Screened TP) - unique global shield
- UTP (Unshielded Twisted Pair) - non-shielded, only separate pair insulation
4
Q
UTP
basic
A
- used in telephone network, company’s buildings, LAN
- advantages: cheap, easy to install
- disadvantages: susceptible to EM interference and noise, need for amplification, near end crosstalk
5
Q
UTP
categories
A
- Telecommunication
- Low Speed Data
- High Speed Data
- Low Loss, High Performance Data
- Low Loss, Extended Frequency
6 & 7. Low attenuation and higher noise immunity
6
Q
Coaxial Cable
A
- base-band cable
- broad-band cable
- advantages: goes up to 500MHz, repeaters every 1-2 km
- drawbacks: shared broadcast medium
7
Q
Fiber Optic
A
- inner glass core, covered by a glass cladding with different refractive and density properties for protection and easier cabling
- advantages: low attenuation, total immunity to EM field effects, transmission data rates in the order of Giga bps, easy for cabling
- quality of the fiber given by ratio between cladding diameter and whole fiber diameter
8
Q
Light Propagation Modes
fiber optic cable
A
-
Step-Index Multimode
* refraction index constant for the fiber core
* implies different path lengths for light rays, making reception difficult
* present a thicker core - cheaper fiber -
Graded-Index Multimode
* refraction index decreasing from the core centre to edges
* offer a better focusing of the rays - lower attenuation and easier reception -
Single Mode/Mono-mode
* core diameter ~ light ray wavelength - direct path for light ray, no loss, no attenuation, but more expensive
9
Q
Multimode Fiber
A
- used in communications over short distances (hundreds of meters)
10
Q
Single-mode fiber
A
- used in communications over long distances
- advantages:
- longer transmission distance
- greater bandwidth capacity
- increased transmission speed
- limited data dispersion & external interference
- less signal attenuation
11
Q
Transmission Devices
A
- LEDs (light emitting diodes) or laser (diodes) - for single mode transmission
- reception of light and conversion into electrical signal using photodiodes
12
Q
Structured Cabling Systems
A
Standard specification concern:
* min. requirements for cabling a building with a given number of offices
* cabling topology and the allowed distances
* components of the cabling system
* transmission media and their characteristics
* vertical/horizontal cabling
* cable identification manner
* necessary documentation of the project
13
Q
Constitutive Cabling Components
A
- main crossconnect (MC) - star center, a distribution center of main cables for other buildings or other cabling levels
- intermediate crossconnect (IC) - local to each building, a ‘one by floor’ distribution closet
- telecommunication closet (TC) - cabling towards workstations, more on a floor; contains patch pannels
- intrabuilding backbone - cabling between ICs and local TCs
- interbuilding backbone - cabling between MC and other buildings
- equipment room - local to a cabling level - contains passive and active equipment
- interbuilding entrance facility - interface between outside cabling and inside backbone, especially grounding facilities
- work area - identifies workstations, associated patch + drop cables, adapters
- patch panels - switching pannels for coax or UTP or barrel panels for fiber optic
- telecommunication outlets - connect workstations to the cabling system
- cabling adapters - passive/active
