Lecture 7b Fiber-optic Types & Termination

Transceivers AUI connectors Media converters

Thin Net Coax

(Coaxial Cable) Used for 10Base 2 Ethernet. Coax is primarily used for its self shielding properties, low attenuation at LAN frequencies, and installation expense. The construction of the cable greatly reduces susceptibility to outside interfering signals and noise, as well as minimizing the radiated emissions from the cable.

Category 3


Category 4


Category 5


Enhanced Category 5 and Category 6


UTP Cable Termination Tools
Punch Blocks Crimp Tools

UTP Connectors




Communications equipment operates by detecting signal variations (which becomes more difficult as the signal becomes weaker). In a Category 5 system TIA/EIA 568A limits attenuation to 24 dB for 100 MHz signal. 20 db of attenuation means that only 1/100 th of the original signal reaches its destination. the lower the dB means the stronger the signal Distance, higher frequencies and high temperatures increase attenuation.

plugs jacks patch Panels patch cables labels
TIA/EIA 568 Standard
UTP Cable Certification and Testing

Attenuation and Near End Cross Talk (NEXT) are the two most crucial electrical perameters that distinguish performance characteristics of twisted pair cable. Attenuation Attenuation is the loss of communication signal energy. Represented in dB or decibels. Decibels Attenuation and NEXT are reported in negative (- dB). Attenuation and NEXT dB are relative measures of changes in voltage. dB loss has a logarithmic progression.
Pair Scanners



Pair Scanners CAT 5 Pair Scanner (Cable Tester) CAT 5 Pair Scanners Differ from normal Pair Scanners in that they test all pairs of the cables at various frequencies up to 100 MHz. Measures each pair for Distance (Including Twist Pitch)

Too much signal "noise" prevents the receiver from distinguishing transmit form receive signals and results in garbled transmission and poor network performance.

Characteristics

Four Pair, 24 Gauge 100 Ohm copper cable Unbalanced PVC or Plenum Jacket Types of UTP Cable: Category 3, 4, 5, and "Enhanced Category 5" or Category 6 Transmission Frequencies up to 16 MHz intended for low speed data, telephone, 4 Mbps Token Ring, and 10 Mbps Ethernet applications. Transmission Frequencies up to 20 MHz Suitable for all category 3 applications as well as 16 Mbps Token Ring Transmission Frequencies up to 100 Mhz Most popular for high speed applications Suitable for all Category 3 and 4 applications as well as any copper based voice, video, or data application such as: 100 Mbps "Fast Ethernet", CDDI (FDDI over Copper), and ATM. High frequency applications such as Gigabit Ethernet and certainly ATM will require better and higher bandwidth cables than originally specified by the Category 5 standard. While Gigabit Ethernet should be compatible with Category 5 cabling, it is suggested that cabling for high speed applications including Fast Ethernet should exceed Category 5 standards. New standards for such cabling is underway.



Jacket- (sheath) The outer protective covering of a cable. Center Conductor Inner part of a Thin- net (coaxial cable). Center conductor or wire on which the LAN signal is carried. See Thin-net, shield, braided wire shield, foil shield, 10Base 2." Insulation A material which is nonconductive to the flow of electric current. The coating (usually plastic) of a conductor which insulates it from other conductors. Shield A metallic foil or multi-wire screen mesh that is used to prevent electromagnetic fields from penetrating or exiting a transmission cable.
Lecture 7b Fiber-optic Types & Termination:

Cable Distribution
• Cable Distribution Equipment
UTP (Unshielded Twisted Pair)
• UTP Cable Termination Tools • UTP Connectors, plugs, jacks, and patch Panels • UTP Cable Certification and Testing
Attenuation to Cross Talk margin
•


Attenuation per 100m

NEXT Peak Frequency
Category 3 13.1 dB 23 dB 16 MHz
Category 4 8.9 dB 38 dB 20 MHz
Category 5 8.2 dB 44 dB 100 MHz
Optical Fiber

Multi-Mode fiber most commonly used in LANs and MANs. A fiber wave guide which supports the propagation of multiple modes. Multi-mode fiber may have a typical core diameter of 50 to 100 um with a refractive index that is graded or stepped. It allows the use of inexpensive LED light sources and connector alignment and coupling is less critical than with single mode fiber. Distances of transmission and transmission bandwidth are less than single mode fiber due to dispersion of the light signal.
Shielded Twisted Pair Thin-Net Coaxial Cable Optical Fiber
• Multi-Mode fiber • Single Mode Fiber • Fiberoptic Connectors
UTP (Unshielded Twisted Pair)
• • • • • • • 3 dB = 2X 10 dB = 10X 20 dB = 100X 30 dB = 1,000X 40 dB = 10,000X 50 dB = 100,000X 60 dB = 1,000,000X

Attenuation
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Attenuation refers to the power loss an electrical signal experiences as it travels through a cable.
Near End Cross Talk (NEXT)

NEXT occurs when a portion of the signal energy jumps from one pair in a cable to another.





Cables are most susceptible to cross talk near their ends, or close to devices. In a UTP cable one or two pairs are used to transmit signals while the other pair or pairs receive. Close proximity of the transmit pairs increases NEXT. The first 50 or 60 ft of a cable run are the most susceptible to NEXT. Cross connects are especially susceptible to NEXT.