Lecture 8 Cable Certification &

Testing:

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

Shielded Twisted Pair Thin-Net Coaxial Cable Optical Fiber

• Multi-Mode fiber

• Single Mode Fiber

• Fiberoptic Connectors

UTP (Unshielded Twisted Pair) 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

Category 3 Transmission Frequencies up to 16 MHz intended for low speed data, telephone, 4 Mbps Token Ring, and 10 Mbps Ethernet applications.

Category 4 Transmission Frequencies up to 20 MHz Suitable for all category 3 applications as well as 16 Mbps Token Ring

Category 5 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.

Enhanced Category 5 and Category 6 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.

TIA/EIA 568 Standard

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. 

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.

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.

Single Mode Fiber A fiber wave guide in which only one mode will

propagate. Single mode fiber has a very small core diameter, in some fibers aprox. 8 micron. It allows signal transmission for long fiber distances with relatively high bandwidth and is generally driven with a laser diode."

Fiber-optic Components Core – inner fiber (62.5mic.) Cladding – encases core (125mic.) Jacket- surrounds core and cladding Strength & environmental members

Indoor Fiber-optic Cables

Fiber-optic Connectors ST SC FSD

Fiber Termination Techniques

Breakout Cable Epoxy Crimp UV Cure Epoxy Air Blown Fiber

Transceivers AUI connectors Media converters

Testing & Certification UTP Cable Certification and Testing

Attenuation & Next Pair Scanners

Standards TSB-67 “Transmission Performance

Specifications for Field Testing of Unshielded Twisted-Pair Cabling Systems”

568-A

UTP Properties Attenuation Next

Attenuation and Near End Cross Talk (NEXT) are the two most crucial electrical parameters that distinguish performance characteristics of twisted pair cable.

Attenuation

Attenuation refers to the power loss an electrical signal experiences as it travels through a cable.

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.

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.

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

 

Attenuation to Cross Talk margin

• Category 3 Category 4 Category 5

Attenuation per 100m 13.1 dB 8.9 dB 8.2 dB NEXT 23 dB 38 dB 44 dB Peak Frequency 16 MHz 20 MHz 100 MHz

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)

http://www.humboldt.edu/~mdh3/network/netlab/cabletests/lb121-1.html