Download Module 3 Copper,Optical Media Presentation

CCNA1 Module 3
Topics
Objectives
•Discuss the electrical properties of matter.
•Define voltage, resistance, impedance, current, and
circuits.
•Describe the specifications and performances of different
types of cable.
•Describe coaxial cable and its advantages and
disadvantages over other types of cable.
•Describe shielded twisted-pair (STP) cable and its uses.
•Describe unshielded twisted-pair cable (UTP) and its
uses.
•Discuss the characteristics of straight-through, crossover,
and rollover cables and where each is used.
•Explain the basics of fiber-optic cable.
•Describe how fibers can guide light for long distances.
•Describe multimode and single-mode fiber.
•Describe how fiber is installed.
•Describe the type of connectors and equipment used with
fiber-optic cable.
•Explain how fiber is tested to ensure that it will function
properly.
•Discuss safety issues dealing with fiber-optics.
Periodic Table of Elements
Copper(Cu),Silver(Ag),
and Gold (Au)
Periodic Table
The periodic table categorizes some groups of atoms by
listing them in the form of columns. The atoms in each
column belong to particular chemical families. Although
they may have different numbers of protons, neutrons,
and electrons, their outermost electrons have similar
orbits and behave similarly when interacting with other
atoms and molecules. The best conductors are metals,
such as copper (Cu), silver (Ag), and gold (Au), because
they have electrons that are easily freed. Other
conductors include solder, a mixture of lead (Pb) and tin
(Sn), and water with ions. An ion is an atom that has more
electrons, or fewer electrons, than the number of protons
in the nucleus of the atom. The human body is made of
approximately 70% water with ions, which means that the
human body is a conductor.
Atoms and Electrons
•Electrons – Particles with a negative charge that orbit
the nucleus
•Nucleus – The center part of the atom, composed of
protons and neutrons
•Protons – Particles with a positive charge
•Neutrons – Particles with no charge (neutral)
The protons and neutrons are bound together by a very
powerful force. However, the electrons are bound to their
orbit around the nucleus by a weaker force. Electrons in
certain atoms, such as metals, can be pulled free from
the atom and made to flow. This sea of electrons, loosely
bound to the atoms, is what makes electricity possible.
Electricity is a free flow of electrons.
Loosened electrons that stay in one place, without
moving, and with a negative charge, are called static
electricity. If these static electrons have an opportunity to
jump to a conductor, this can lead to electrostatic
discharge (ESD).
ESD, though usually harmless to people, can create
serious problems for sensitive electronic equipment. A
static discharge can randomly damage computer chips,
data, or both. The logical circuitry of computer chips is
extremely sensitive to electrostatic discharge. Use caution
when working inside a computer, router, and so on.
Atoms, or groups of atoms called molecules, can be
referred to as materials. Materials are classified as
belonging to one of three groups depending on how easily
electricity, or free electrons, flows through them.
The basis for all electronic devices is the knowledge of how
insulators, conductors and semiconductors control the
flow of electrons and work together in various
combinations.
Voltage
Resistance and Impedance
The term attenuation is important when learning about
networks. Attenuation refers to the resistance to the flow of
electrons and why a signal becomes degraded as it travels
along the conduit.
The letter R represents resistance. The unit of measurement
for resistance is the ohm. The symbol comes from the Greek
letter omega.
Impedance is also measured in ohms, but takes into
account the capacitive reactance and inductive reactance
and resistive effects of the cable. This is a more realistic
measurement of how a cable will respond to AC signals.
Insulators, Conductors, and
Semiconductors
Current
If amperage or current can be thought of as the
amount or volume of electron traffic that is flowing,
then voltage can be thought of as the speed of the
electron traffic. The product of amperage and
voltage equals wattage. Electrical devices such as
light bulbs, motors and computer power supplies are
rated in terms of watts. A watt is how much power a
device consumes or produces.
Water Analogy for Electricity
For AC and DC electrical systems, the flow of electrons is
always from a negatively charged source to a positively
charged source.
However, for the controlled flow of electrons to occur, a
complete circuit is required. Remember, electrical current
follows the path of least resistance.
Oscilloscope
An oscilloscope is an electronic device used to measure
electrical signals relative to time. An oscilloscope graphs the
electrical waves, pulses, and patterns. An oscilloscope has an
x-axis that represents time, and a y-axis that represents
voltage. There are usually two y-axis voltage inputs so
that two waves can be observed and measured at the
same time.
Series Circuits
Cable Specifications
Cables Specs
10BASE-T refers to the speed of transmission at 10 Mbps.
The type of transmission is baseband, or digitally interpreted.
The T stands for twisted pair.
10BASE5 refers to the speed of transmission at 10 Mbps.
The type of transmission is baseband, or digitally interpreted.
The 5 represents the capability of the cable to allow the
signal to travel for approximately 500 meters before
attenuation could disrupt the ability of the receiver to
appropriately interpret the signal being received. 10BASE5 is
often referred to as Thicknet. Thicknet is actually a type of
network, while 10BASE5 is the cabling used in that network.
10BASE2 refers to the speed of transmission at 10 Mbps.
The type of transmission is baseband, or digitally
interpreted.
The 2, in 10BASE2, represents the capability of the cable
to allow the signal to travel for approximately 200 meters,
before attenuation could disrupt the ability of the receiver
to appropriately interpret the signal being received.
10BASE2 is often referred to as Thinnet. Thinnet is
actually a type of network, while 10BASE2 is the cabling
used in that network.
Coaxial Cable
Shielded Twisted Pair
ScTP Screened Twisted Pair
Unshielded Twisted Pair
UTP Cabling
Unshielded twisted-pair cable has many advantages. It is
easy to install and is less expensive than other types of
networking media. In fact, UTP costs less per meter than any
other type of LAN cabling. However, the real advantage is
the size. Since it has such a small external diameter, UTP
does not fill up wiring ducts as rapidly as other types of cable.
This can be an extremely important factor to consider,
particularly when installing a network in an older building. In
addition, when UTP cable is installed using an RJ-45
connector, potential sources of network noise are greatly
reduced and a good solid connection is practically
guaranteed.
There are disadvantages in using twisted-pair cabling.
UTP cable is more prone to electrical noise and
interference than other types of networking media, and
the distance between signal boosts is shorter for UTP
than it is for coaxial and fiber optic cables.
UTP was once considered slower at transmitting data
than other types of cable. This is no longer true. In fact,
today, UTP is considered the fastest copper-based
media.
Straight-Through Cable Pinouts
Switch to Switch Connections
Cross-Over Cable
Connecting to a Console Port
Rollover Cable
Wavelength
The light used in optical fiber networks is one type of
electromagnetic energy.
When an electric charge moves back and forth, or
accelerates, a type of energy called electromagnetic energy
is produced. This energy in the form of waves can travel
through a vacuum, the air, and through some materials like
glass. An important property of any energy wave is the
wavelength.
Electromagnetic Spectrum
Visible Light Spectrum
W=700 nm
F=428.5 THz
W= 300,000,000m/s / freq
1x10^12 Hz = 1 TeraHz
W=400 nm
F=750 THz
Human eyes were designed to only sense electromagnetic
energy with wavelengths between 700 nanometers and
400 nanometers (nm).
A nanometer is one billionth of a meter (0.000,000,001
meter) in length.
Electromagnetic energy with wavelengths between 700 and
400 nm is called visible light.
The longer wavelengths of light that are around 700 nm are
seen as the color red. The shortest wavelengths that are
around 400 nm appear as the color violet.
This part of the electromagnetic spectrum is seen as the
colors in a rainbow.
Wavelengths that are not visible to the human eye are
used to transmit data over optical fiber.
These wavelengths are slightly longer than red light and
are called infrared light. Infrared light is used in TV
remote controls.
The wavelength of the light in optical fiber is either 850
nm, 1310 nm, or 1550 nm.
These wavelengths were selected because they travel
through optical fiber better than other wavelengths.
850nm light is called short wave (1000baseSX).
1550nm light is called long wave (1000baseLX).
Ray Model of Light
Index of Refraction
Think of light rays as narrow beams of light like those
produced by lasers.
In the vacuum of empty space, light travels continuously
in a straight line at 300,000 kilometers per second.
However, light travels at different, slower speeds through
other materials like air, water, and glass. When a light ray
called the incident ray, crosses the boundary from one
material to another, some of the light energy in the ray
will be reflected back.
That is why you can see yourself in window glass. The
light that is reflected back is called the reflected ray.
The light energy in the incident ray that is not reflected
will enter the glass. The entering ray will be bent at an
angle from its original path.
This ray is called the refracted ray.
How much the incident light ray is bent depends on the
angle at which the incident ray strikes the surface of the
glass, and the different rates of speed at which light
travels through the two substances
A material with a large index of refraction is more
optically dense and slows down more light than a
material with a smaller index of refraction.
Reflection
The Law of Reflection states that the angle of reflection of
a light ray is equal to the angle of incidence.
In other words, the angle at which a light ray strikes a
reflective surface determines the angle that the ray will
reflect off the surface.
Refraction
If the incident ray strikes the glass surface at an exact 90degree angle, the ray goes straight into the glass. The ray is
not bent.
However, if the incident ray is not at an exact 90-degree angle
to the surface, then the transmitted ray that enters the glass is
bent.
The bending of the entering ray is called refraction.
How much the ray is refracted depends on the index of
refraction of the two transparent materials. If the light ray
travels from a substance whose index of refraction is smaller,
into a substance where the index of refraction is larger, the
refracted ray is bent towards the normal. If the light ray travels
from a substance where the index of refraction is larger into a
substance where the index of refraction is smaller, the
refracted ray is bent away from the normal.
Consider a light ray moving at an angle other than 90
degrees through the boundary between glass and a
diamond. The glass has an index of refraction of about
1.523. The diamond has an index of refraction of about
2.419. Therefore, the ray that continues into the diamond
will be bent towards the normal. When that light ray
crosses the boundary between the diamond and the air at
some angle other than 90 degrees, it will be bent away
from the normal. The reason for this is that air has a lower
index of refraction, about 1.000 than the index of refraction
of the diamond.
Total Internal Refraction
A design must be achieved for the fiber that will make the
outside surface of the fiber act like a mirror to the light ray
moving through the fiber. If any light ray that tries to move
out through the side of the fiber were reflected back into the
fiber at an angle that sends it towards the far end of the
fiber, this would be a good “pipe” or “wave guide” for the light
waves.
The following two conditions must be met for the light
rays in a fiber to be reflected back into the fiber
without any loss due to refraction:
1. The core of the optical fiber has to have a larger
index of refraction (n) than the material that surrounds
it.
The material that surrounds the core of the fiber is
called the cladding.
2. The angle of incidence of the light ray must be
greater than the critical angle for the core and its
cladding.
When both of these conditions are met, the entire
incident light in the fiber is reflected back inside the
fiber.
Numerical Aperture (NA)
The numerical aperture of the fiber – The numerical
aperture of a core is the range of angles of incident light rays
entering the fiber that will be completely reflected.
Modes – The paths which a light ray can follow when
traveling down a fiber.
By controlling both conditions, the fiber run will have total
internal reflection. This gives a light wave guide that can be
used for data communications.
Fiber Optics
Single Mode & Multimode Fiber
Single-mode fiber has a
much smaller core that
only allows light rays to
travel along one mode
inside the fiber.
If the diameter of the core of
the fiber is large enough so
that there are many paths that
light can take through the
fiber, the fiber is called
“multimode” fiber.
Duplex Fiber
Fiber Optic Cable Connector
Usually, five parts make up each fiber-optic cable. The
parts are the core, the cladding, a buffer, a strength
material, and an outer jacket.
Dispersion
Dispersion of a light flash also limits transmission
distances on a fiber. Dispersion is the technical term for the
spreading of pulses of light as they travel down the fiber.
Multimode uses a type of glass, called graded index
glass for its core. This glass has a lower index of
refraction towards the outer edge of the core.
Therefore, the outer area of the core is less optically
dense than the center and light can go faster in the outer
part of the core.
This design is used because a light ray following a mode
that goes straight down the center of the core does not
have as far to travel as a ray following a mode that
bounces around in the fiber.
All rays should arrive at the end of the fiber together. Then
the receiver at the end of the fiber receives a strong flash
of light rather than a long, dim pulse.
Optical Cable Design
Emitters
Infrared Light Emitting Diodes (LEDs) or Vertical Cavity
Surface Emitting Lasers (VCSELs) are two types of light
source usually used with multimode fiber. Use one or the
other.
LEDs are a little cheaper to build and require somewhat
less safety concerns than lasers.
However, LEDs cannot transmit light over cable as far as
the lasers.
Multimode fiber (62.5/125) can carry data distances of up
to 2000 meters (6,560 ft).
Single Mode Fiber
Warning: The laser light used with single-mode has a
longer wavelength than can be seen. The laser is so strong
that it can seriously damage eyes.
Never look at the near end of a fiber that is connected to a
device at the far end.
Never look into the transmit port on a NIC, switch, or
router. Remember to keep protective covers over the ends
of fiber and inserted into the fiber-optic ports of switches
and routers.
Be very careful.
Transmission Devices
SC and ST Fiber Connectors
Connectors are attached to the fiber ends so that the
fibers can be connected to the ports on the transmitter
and receiver.
The type of connector most commonly used with
multimode fiber is the Subscriber Connector (SC
connector).
On single-mode fiber, the Straight Tip (ST) connector is
frequently used.
There are two types of light sources used to encode and
transmit the data through the cable:
•A light emitting diode (LED) producing infrared light with
wavelengths of either 850nm or 1310 nm. These are used
with multimode fiber in LANs. Lenses are used to focus the
infrared light on the end of the fiber
•Light amplification by stimulated emission radiation
(LASER) a light source producing a thin beam of intense
infrared light usually with wavelengths of 1310nm or 1550
nm. Lasers are used with single-mode fiber over the longer
distances involved in WANs or campus backbones. Extra
care should be exercised to prevent eye injury
Signals and Noise in
Fiber Optic Cable
Although fiber is the best of all the transmission media at
carrying large amounts of data over long distances, fiber is
not without problems.
When light travels through fiber, some of the light energy is
lost. The farther a light signal travels through a fiber, the
more the signal loses strength. This attenuation of the
signal is due to several factors involving the nature of fiber
itself.
The most important factor is scattering. The scattering of
light in a fiber is caused by microscopic non-uniformity
(distortions) in the fiber that reflects and scatters some of
the light energy.
Absorption is another cause of light energy loss. When a
light ray strikes some types of chemical impurities in a fiber,
the impurities absorb part of the energy. This light energy is
converted to a small amount of heat energy. Absorption
makes the light signal a little dimmer.
Another factor that causes attenuation of the light signal is
manufacturing irregularities or roughness in the core-tocladding boundary. Power is lost from the light signal
because of the less than perfect total internal reflection in
that rough area of the fiber. Any microscopic imperfections in
the thickness or symmetry of the fiber will cut down on total
internal reflection and the cladding will absorb some light
energy.
Dispersion of a light flash also limits transmission distances
on a fiber. Dispersion is the technical term for the spreading
of pulses of light as they travel down the fiber.
Scattering
Bending
Fiber End Face Finishes