Principles Of Transmission Flashcards
Transmission Rates
b/s = 1 bit per sec
kb/s= 1000 b/s
Mb/s= 1,000,000 b/s
Gb/s= 1,000,000,000 b/s
Tb/s= 1,000,000,000,0000 b/s
Megahertz
Quantifies the bandwidth of a cabling system in a frequency range of interest
Megabits (Mb)
Refers to the number of bits of information that can be transported over the media
What happens with a gauge change of three number across a conductor?
Change of six numbers?
Doubles or halves the conductors cross-sectional area
Doubles or halves the conductors resistance
Six numbers doubles or halves the conductors diameter
What is resistance?
The property of a conductor to resist the flow of electricity through it. Expressed in Ohms.
Ohms law
Voltage= Current x Resistance
V=I x R
What is Inductance?
The property to oppose any change in current flow due to electromagnetic field set up around a conductor.
Basic unit of inductance is a Henry (H)
Inductive reactance
XL= 2 x pie x frequency x inductance
What is Capacitance?
Property of conductors that allows storage of electric charges when potential differences exist between conductors.
Measured in farads (F)
What is Impedance?
Total opposition to current flow
What is the characteristic impedance of most balanced twisted-pair cabling used for ICT
100 ohms plus or minus 15% at 1 MHz at a temperature of 68*F
What is Insertion loss (Attenuation)
The measure of signal loss resulting from insertion of a component, link, or channel between a transmitter and receiver.
Measured in dB per unit length
As frequency or length increases, attenuation increases
What is return loss?
The ratio of the power of the outgoing signal to the power of the reflected signal and is expressed in dB
Components that cause return loss include:
Media, connectors, receiver, and transmitter
Nominal Velocity of Propagation (NVP)
The speed of a signal along a cable relative to the speed of light in a vacuum
Speed of transmission/Speed of light
What are the most important transmission parameters of a balance twisted pair?
Signal attenuation as a function of frequency
Signal reflections at terminations
Amount of noise relative to the to the received signal (signal to noise ratio)
What minimizes detrimental crosstalk and noise?
Proper cable design and twisting of the pairs
What are the TIA categories and performance frequencies?
Cat 3- 16MHz
Cat 5e- 100MHz
Cat6- 250MHz
Cat6A- 500MHz
Cat8- 2000MHz
What are the three basic types of Crosstalk?
Near end crosstalk (NEXT)
Attenuation to crosstalk ratio, far end (ACR-F)
Alien Crosstalk (AXT)
What is NEXT?
Measure of the unwanted signal coupling from a transmitter at the near end into another pair measured at the near end of the
What is ACR-F?
The measure of the unwanted signal transfer that is assessed be applying a signal on pair at the near end and measuring the signal transfer level on any disturbed pair at the receiving end of the cable.
What is AXT?
Unwanted signal coupling from a disturbing pair of a 4-pair cable channel, permanent link, or component to another pair in a different 4-pair channel, permanent link or component.
Three predominant types of coaxial cable and their commonality?
Series-6 (RG-6)
Series-11 (RG-11)
Series 59 (RG-59)
Should have impedance of 75 ohms
Coated foil shield over the dielectric to shield against high frequency
Braided shield over the coated foil to shield to shield against low frequency
What are the two types of fiber optic cable?
Singlemode and Multimode
What grades of multimode are there?
OM2- not recommended for new install
OM3 laser optimized- higher bandwidth
OM4- highest multimode bandwidth optimized for 850 microns VCSEL
OM5- 850, 880, 910, 940 micron VSCEL for CWDM
Multimode has a 50 micron core and 125 micron cladding diameter.
What are the characteristics of singlemode fiber?
Has a core diameter between 8 and 10.5 micron,
Commonly installed is OS2 - OSP, typically loose tube construction.
Wavelengths for OS1 and OS2 are 1310, 1383 and 1550 nanometers
Optical fiber marking and its type
OFNP- Non-conductive optical fiber plenum
OFCP- Conductive optical fiber plenum
OFNR- Non-conductive optical fiber riser
OFCR- Conductive optic fiber riser
OFNG- Non-conductive optic fiber general-purpose
OFCG Conductive optic fiber general-purpose
OFN same as OFNG
OFC same as OFCG
