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May 2008

Cables-Engl - 1 © P. Nicoletti: see note pag. 2

Copper and Fiber Optic Cables

Pietro Nicolettipiero[at]studioreti.it



May 2008


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May 2008


Copper cables main characteristics The main characteristics of a transmission media are:

Vp: Velocity of propagation of the signal expressed as

c fraction (speed of the light in the empty space): values included between 0.5 and 0.8 c

Z = r+jI impedance of the line

conductors' dimension

american AWG unit of measurement

Diameter, electrical resistance



May 2008


AWG: American Wire Gage Scale to measure the copper wire dimension

It is a geometrical regression

with 39 values in the interval 000 gage (0.460 diameterinch) and 36 gage (0.005 diameter inch)

Every increase of a gage corresponds to a diameter

relationship of:

0.460

0.005( )

1/39

= 92 = 1.2293221/39



May 2008


Copper cables AWG

AWG mm (Ø) mm2 Kg/Km Ω /Km

22 0.6438 0.3255 2.894 52.96

23 0.5733 0.2582 1.820 84.21

24 0.5106 0.2047 1.746 87.82

25 0.4547 0.1624 1.414 108.4

26 0.4049 0.1288 1.145 133.9

24 or 22 AWG for structured cabling system

26 AWG for patch cord



May 2008


Copper cable attenuation The attenuation is the output signal reduction with

respect to the entry signal in the cable:

attenuation linearly grows in dB with the length of thecable and the frequency square root

to reduce the cable attenuation expanded insulators areused because improve the capacity



May 2008


Attenuation

V1 V2

αdB = 20 log10 (V1 / V2)



May 2008


Copper pair Cross-Talk Signal energy part induction on the near conductors,

where a disturb becomes

The phenomenon increases with increasing it byfrequency

It can be measured in several manners



May 2008


NEXT: Near End Cross-Talk Cross-Talk measured at the transmitter side

V1

V3

NEXTdB = 20 log10 (V1 / V3)



May 2008


NEXT: Near End Cross-Talk The attenuation only makes the NEXT measure

significant by the first 20-30 mt of cable

The measurement is necessary to both ends: dual NEXT

V1

V3



May 2008


FEXT: Far End Cross-Talk Cross-Talk measured at the receiver side

V1

V4

FEXTdB = 20 log10 (V1 / V4)



May 2008


ACR ACR (Attenuation to Cross-Talk Ratio)

Combination of attenuation and NEXT

signal to noise ratio

noise caused by Cross-Talk

Required only by ISO and EN normative



May 2008


ELFEXT: Equal Level FEXT

~

~



May 2008


PSELFEXT (Power Sum ELFEXT)

~~

~~

~~



May 2008


Velocity of propagation (Vp) The propagation velocity of the signals on the

transmission means is high, but not infinite, so the

propagation time is little but not null It is necessary to ensure that delays do not exceed

certain maximum values to ensure the protocol working

VP ≅ 2/3 c

( c

is speed of the light in the empty space ≅ 3 • 10 8 m/s)



May 2008


Delay skew



May 2008


Return loss Il return loss = reflections measurements

Z1 Z3Z2Impedancevariations



May 2008


Shielded cable The shield presence can involve:

bigger immunity to the electromagnetic disturb

disturb radio emission reduction

bigger constancy of the impedance

if applied to single pair reduces the crosstalk

It is necessary to make a correct screen grounding:



May 2008


Twisted pair cable Constituted by one or more twisted pair of copper

conductors

Used for voice, local nets, structured cabling system the electrical characteristic required for LAN are

definitely higher than those for voice

Lower bandwith than the coaxial one Reduced costs and simple installation



May 2008


Twisted Pair cable types UTP (Unshielded Twisted Pair):

(Z = 100 Ω)

FTP (Foiled Twisted Pair):

(Z = 100 Ω)

S-UTP o S-FTP:

(Z = 100 Ω) STP (Shielded Twisted Pair):

(Z = 150 Ω)



May 2008


UTP 100 Ω

pair 1

pair 2

pair 3

pair 4



May 2008


FTP 100 Ω

pair 1pair 2

pair 3

pair 4

Drain wire for shield continuity

Foil shield



May 2008


S-UTP or S-FTP 100 Ω

pair 1

pair 2

pair 3

pair 4

Copper braid

Single foil shielded pair



May 2008


STP 150 Ω Know as Type 1 IBM

22 AWG



May 2008


GLASS FIBER OPTIC



May 2008


Glass Fiber Optic It is a tiny and flexible glass material thread:

an internal part called core

an outside part called cladding core and cladding have different refraction indexes to

border the light inside core

CORE

CLADDING

PRIMARY COATING

SECONDARY COATING



May 2008


Glass Fiber Optic characteristics The optic fibers are just suitable for point point links

Total immunity to the electromagnetic troubles

Characterized by two numbers n/m where:

diameter n of the leading internal light part

diameter m of the outside part

Typical values in micronmultimode 50/125, 62.5/125, 100/140

singlemode 8-10/125



May 2008


Step-index multimode fiber Characteristics

High modal dispersion

Low bandwith

M1

M4M3

M2

M1

M2

M3

M4

T1 T2

Input signal Output signal



May 2008


Graded-index multimode fiber Graded-index fiber have a bandwith higher than step-

index

work in 1st and 2nd window (850 and 1300 nm)

M 2008



May 2008


Singlemode fiber

The fiber behaves like a wave guide admitting asingle propagation mode:

does not have modal dispersion

the bandwith is very high, of the order of hundredsof GHz*Km

work in 2nd

and 3th

window (1300 and 1500 nm)

May 2008



May 2008


Wavelenght and optical components

A t t e n u a

t i o n ( d B X K m

)100

1

5

10

500 600 700 850 900 1000 1100 1200 13001310

1400 1550

LED\VCSEL

LASER DIODEVCSEL

LASER DIODE

May 2008



May 2008


Fiber optic cable types Tight

Break-out

dual fiber patch cord Light-duty

Loose

May 2008



May 2008


Break-Out tight fiber optic cable

Fiber opticExternal diameter 250 µm

250 µm = 125 µm + primary coating

CentralDielectric element

SheathToxfree or Low-smoke-fume

Kevlar

Secondary coatingExternal diameter 0.9 mm

External diameter 2 ÷ 3 mm

Indoor installation

May 2008



May 2008


Dual fiber patch cord



SheathToxfree o Low-smoke-fume

Kevlar

Secondary coatingExternal diameter 0.9 mm External diameter 2 ÷ 3 mm

May 2008



y


Light-duty tight fiber optic cable


Kevlar

Secondary coatingExternal diameter 0.9 mm



Roditor resistant protection

SheathToxfree o Low-smoke-fume

Indoor/Outdoor installation

May 2008



y


Loose fiber optic cable

Fiber optic

External diameter 250 µm250 µm = 125 µm + primary coating


Kevlar

Roditor resistant protection

TubeJelly filled

Sheath

Sheath

Outdoor installation

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