Transmission Media Flashcards
What does bandwidth mean in reference to a data cable?
The bandwidth of a transmission channel is the frequency interval over which the signal does not experience line loss greater than 3 decibels.
How can a periodic waveform be approximated?
Addition of harmonically related sine waves
What properties of a copper cable limit it’s bandwidth?
1) Resistance
2) Inductance
3) Capacitance (negligible)
What is characteristic impedance?
Cable’s impedance to high frequency signals
The LRC model shows that all copper cables act as _________________. This causes signals to _______, especially in the __________________ components of wave forms.
1) Low pass filters
2) Degrade
3) High frequency
What is the purpose of a terminating resistor in data cabling?
The resistor prevents the signal from being reflected back onto the wire which saves it from being distorted.
What is the main characteristic of the copper cable that causes signal attenuation?
Resistance
What is the purpose of the shield conductor?
The shield is used in noisy industrial environments to prevent noise interference and data leaks onto other wires.
What are the 3 types of copper cables and what are their uses?
1) Unshielded Twisted pair: used in residential and commercial
2) Shield Twisted Pair: used in industrial fieldbus networks
3) Co-axial: backbone of DCS systems
What is the difference between how a signal is transmitted using twisted pairs or fiber optic cable?
Twisted pair cables use electricity to carry the signal but fiber optic cable uses light
What are the 3 advantages of fiber optic cable?
1) No noise as you’re dealing with light and not electrical current
2) Lower signal losses over a long distance
3) Higher bandwidth (data rates)
What are the disadvantages of using fiber optic cable?
1) Installation, splicing, setup is more difficult
2) More expensive than Copper cable
How is full duplex communication achieved using Fiber optic cable?
1) The transmitter picks up a signal and an LED converts the signal into light pulses
2) Light pulse signal goes to the receiver via fiber optic cable
3) The detector at the receiver end pick up on the light pulses and converts them back to an electrical signal
What are the 3 main parts of a fiber optic cable?
1) Core: carries the light pulses
2) Cladding: a reflective coating confines the light signal in the core to prevent light from coming out. Can also be made of plastic or glass
3) Buffer or Jacket: outer cable covering that provides mechanical strength
What are the 2 types of fiber optic cables?
1) Single mode: have thinner cores than multimode (core/cladding: 8.25/125),light travels along a single path which allows for higher data rates than multimode, more expensive than multimode
2) Multimode: thicker cores than single mode (core/cladding: 62.5/125), easier to install than single mode, higher attenuation/distortion as light travels in many paths, more limited in data rates due to the light dispersion
