# Wire and Fiber Printable Lecture

General Wire Info

• Network wire is either PLENUM-Rated or NON-PLENUM rated.
• A plenum is an air space in a building used as an air circulation return.
• If the wires run in a plenum, you MUST use PLENUM-Rated cable. This is a fire code.

• Material of the outer coating of the cable is what changes in plenum vs non-plenum cable
• PLENUM-Rated cable will not give off toxic fumes in a fire. Non-plenum will.
• Plenum-rated cable will generally cost about 30% more than Non-plenum rated cable.
• Building engineers can indentify air plenum spaces

Coaxial Cable

• Thick Ethernet (Type RG-11, also called 10Base5 or "trunk" cable)

• Is a bright yellow, about the size of a garden hose, and hard to handle.
• Quite expensive.
• Marked with a band every 1.5 meters to indicated where a connection can be made. Connection made with a "Vampire Tap".

• Construction
• Carrier Wire (Carrier or Signal Wire)
• Copper-can be solid or multi-strands
• Insulation ("Dielectric" nonconductor)
• Foil Shiled(Not all coaxial cable will have this)
• Braided Shield Can be used as a Ground to protect from electromagnetic interference (EMI)
• Jacket Outer Layer of insulation
• Connectors
• Bayonet Nut Connector (BNC)for thin coaxial cable
• N-Series Connector are for thick coaxial cable
• Threaded Nut Connector (TNC) can be used as in the BNC, provided the other connector is also TNC. Connector are silver, not tin plated.
• Typically installed as a Bus

Coaxial Cable

• Thin EtherNet coaxial cable (RG-58, used to build 10Base2 ethernet networks)

• Much lighter weight than trunk cable, much less expensive and much easier to handle.
• Construction
• Same as thick (but about the size of a pencil)

• Easier to handle
• Connection must be made by T-connections

• Thin is used by networks other than Ethernet (Notable ArcNet)
• Typically installed as a Bus
• Sometimes installed as Daisy Chain

Twisted Pair Cable

• Shielded Twisted Pair

 Sometimes known as STP, IBM Type-1 Typically used for IBM Token Ring Two pairs of wire, one to RECEIVE one for SEND (Christmas pair and the Halloween pair)

 Typical connector is the IBM Type-1 data connector Installed in a Star A typical kit

Twisted Pair Cable

• Unshielded Twisted Pair  Sometimes known as UTP Used for many different network types including both 10base-T Ethernet and Token Ring Varying qualities or levels of UTP availiable Recommend only Level 5 or Category 5 for data networking Levels 1-5 are availiable, level of shielding is major difference between levels Typical connector is RJ-45 Installed in a Installation of RJ-45

Fiber Optics

Fiber Optic Cable Componenets

Fiber optic cable

• The Protective Covering
• The Optical Fiber

The protective covering
Surrounds the cladding and is usually composed of one or more layers of polymer. This coating protects the core and cladding (the optical fiber) from shock and other physical trauma.

Componenets from innermost to outer, respectively, are: the buffer, the strength members, and the (outer) jacket.

The optical fiber
Composed of two concentric layers called the core and cladding. The core is the light carrying part while the surrounding cladding provides the difference in refractive index necessary for total internal reflection of light through the core.

The index of the cladding is less than one percent lower than that of the core.

Fiber Optic Cable

Multi-Fiber Indoor Cable (MIC)

Single Fiber terminated with ST connector

• Single Mode Fiber
• Multi-mode Fiber

Refraction and Reflection
Fundamentals...(1 of 4)

• The velocity of electromagnetic energy in a vacuum is commonly known as the speed of light (Index of 1 - Velocity of 300,000 km per second).
• Light travels slower in other materials such as glass (Index of 1.5 - Velocity of 200,000 km per second).
• Light travelling from one material to another changes speed, resulting in a change in direction of travel. This deflection is known as refraction.
• Different wavelengths of light travel at different speeds in an identical medium. This variation of velocity with wavelength has an intergral role in fiber optics.
• Also of particular importance is that the index of glass can be changed by controlling its composition.

Refraction and Reflection
Fundamentals...(2 of 4)

If one were to stand on a pier and look directly down at a fish, the light would not be refracted, so the fish would be in its apparent position, but if one were to view that same fish at an angle, refraction of light would occur and the fish would appear closer to the surface. What appears to be a straight line from the fish to the eye is actually a line with a bend where the light passes from water into air and is thus refracted resulting in the fish actually being deeper in the water than it appears.

Refraction and Reflection
Fundamentals...(3 of 4)

• The normal is an imaginary line perpendicular to the interface of the two materials.
• The angle of incidence is the angle between the incident ray and the normal.
• The angle of refraction is the angle between the refracted ray and the normal.

Refraction and Reflection
Fundamentals...(4 of 4)

Light traveling from a lower refractive index to a higher one is bent toward the normal while light passing from a higher index to a lower index refracts away from the normal, as shown above in the top illustration. As the angle of incidence increases, the angle of refraction approaches 90 degrees to the normal. The angle of incidence that yields an angle of refraction of 90 degrees is the critical angle. If the angle of incidence increases past the critical angle (90 degrees), the light is completely reflected back into the first medium and does not enter the second.

FIBER OPTICS - Light...(1 of 5)

Light Propagation Through an Optical Fiber

• Light injected into the fiber and striking the core-to-cladding interface at greater than the critical angle reflects back into the core. Since the angles of incidence and reflection are equal, then the reflected light will again be reflected allowing the light to continue to travel down the length of the fiber in a zigzagging manner.
• Any light striking the core-to-cladding interface at less than the critical angle passes into the cladding and over a distance is lost. Since the cladding is usually an inefficient light carrier, the light in the cladding becomes attenuated quickly.

FIBER OPTICS - Light...(2 of 5)

Internal Reflection In an Optical Fiber

• Analysis of internal reflection considers only meridional rays - those that pass through the fiber axis each time reflected. skew rays are the rays of light that travel down the fiber without passing through the axis.
• Factors affecting light propagation through fiber include: The size of the fiber, the composition of the fiber, and the light injected into the fiber.

FIBER OPTICS - Light...(3 of 5)

Core and Cladding Sizes Fibers are usually expresed by first giving the core size and then the cladding size. (50/125 = a core diameter of 50 $\mu$m and a cladding diameter of 125 m)

FIBER OPTICS - Light (4 of 5)

The Two Main Methods of Fiber Classification are Composition and Mode.

Fiber Classification by Composition

• Glass fibers are the most widely used, they contain a glass core and glass cladding. The glass used in fibers is ultrapure, ultratransparent silicon dioxide or fused quartz. Impurities are intentionally added to achieve the desired index of refraction.

• Plastic-clad silica (or PCS) fibers have a glass core and plastic cladding. Performance is less than glass fibers.

• Plastic fibers have a plastic core and cladding. Performance is low. Application is in enviorments where high bandwidth or low loss are not a concern.

FIBER OPTICS - Light (5 of 5)

Fiber Classification by Mode
The second method of classifying fibers is by the refractive index of the core and thus the modes that the fiber propagates.

• Multimode step-index fiber (commonly called step-index fiber).
• Single-mode step-index fiber (single-mode fiber).

Multimode Step-Index Fiber (Step Index)
Light reflects at different angles for different paths (Modes), the path lengths of different modes are different, thus, different rays take a shorter or longer length of time to travel the length of the fiber. The light is spread out in time. This is described by modal dispersion.

• Composed of cocentric layers of glass, similar to the annular rings of a tree.
• Each successive layer outward from the central axis of the core has a lower index of refraction.
• Each layer of the core refracts the light instead of sharply refecting it as in step-index fiber, the light is continually refracted in an almost sinusoidal pattern.
• Those rays traveling the longest path near the outside of the core have the fastest average velocity while the rays traveling near the center of the core have the slowest average velocity, resulting in all rays tending to reach the end of the path simultaneously.

This fiber is popular in applications requiring a wide bandwidth, such as telecommunications.

Single-Mode Step-Index Fiber (Single-mode fiber)

• Single mode Fiber carries only one mode, therfore, modal dispersion does not exist.
• Capable of 10 Gbps and 130,000 voice channels with repeators needed approximately every 35 km.
• The capacity of a single mode system is only limited by the electronics, not the fiber itself. As newer higher speed electronics systems improve, an existing single-mode fiber system can also be improved without the cost of replacing the entire cabling system!

Fiber Performance Comparisons (General)

Based upon bandwidth, information carrying capacity, and lower losses.

Fiber comparisons from lowest to highest:

• Plasitc
• Step Index glass (multi-mode)
• Single mode

Glass fibers outperform plastic and a smaller core, typically means beter performance.

Typical Fiber Characteristics

Fiber Type
Core Diameter
(in microns)$1$
Diameter
(in microns)

Attenuation
(Max)

Bandwidth
(Max)
Single Mode3.780 or 12510 dB/km @ 650 nm
`   `
5.085 or 1252.3 dB/km @ 850 nm5000 MHz @ 850 nm
6 ps/km$2$
9.31250.4 dB/km @ 1300 nm

0.3 dB/km @ 1550 nm
8.11250.5 dB/km @ 1300 nm

0.25 dB/km @ 1550 nm
Graded Index501252.4 dB/km @ 850 nm

0.6 dB/km @ 1300 nm

0.5 dB/km @ 1550 nm
600 MHz/km @ 850 nm

1500 MHz @ 1300 nm
62.51253.0 dB/km @ 850 nm

0.7 dB/km @ 1300 nm

0.3 dB/km @ 1550 nm
200 MHz @ 850 nm

1000 MHz @ 1300 nm
851252.8 dB/km @ 850 nm

0.7 dB/km @ 1300 nm

0.4 dB/km @ 1550 nm
200 MHz @ 850 nm

400 MHz @ 1300 nm
1001403.5 dB/km @ 850 nm

1.5 dB/km @ 1300 nm

0.9 dB/km @ 1550 nm
300 MHz @ 850 nm

500 MHz @ 1300 nm
Step Index2003806.0 dB/km @ 850 nm6 MHz @ 850 nm
3004406.0 dB/km @ 850 nm6 MHz @ 850 nm
PCS20035010 dB/km @ 790 nm20 MHz @ 790 nm
Plastic485500240 dB/km @ 650 nm5 MHz @ 680 nm$3$
735750230 dB/km @ 650 nm
9801000220 dB/km @ 650 nm

NOTES:
1 - Mode field for single-mode fiber; actual core diameter is less.
2 - Dispersion per nanometer of source width.
3 - Plastic fibers typically are used for distances under 100 m, with data rates up to 50 Mbits/s.

Information source: 1993 Amp, Incorporated.

Indoor Cables(1 of 2)

Simplex Cables
Contain a single optical fiber allowing only simplex or one-way communication since a fiber carries signals in only one direction.

Duplex Cables
Contain two optical fibers allowing duplex or two-way communication. One fiber carries signals in one direction while the other carries them in the oppposite direction. (Of course duplex communication is possible with two simplex cables)
Multifiber Cables
Contain more than two fibers. Allow building wide distribution. Cables are comprised of several loose-buffer tubes, each containing one or more fiber pairs; the tubes are stranded around a central strength member which helps to provide strain relief for the fibers when the cable is stressed.
Breakout Cables
Contain several individual simplex cables inside an outer jacket. Dielectric fillers are utilized to keep the cables positioned and a Mylar wrap containing a ripcord are contained in the jacket allowing the cables inside to be exposed with ease to desired length when needed. Typically available with two or four fibers.

Indoor Cables continued (2 of 2)

Duty Specific Cables, Indoor

Light duty cables
Light jacketed not specifically designed for rugged installation.
Heavy duty cables
Usually have a thicker jacket than Light duty cables to allow for rough handling during installation.
Plenum cables OFNP (optical fiber nonconductive plenum)
As previously discussed, plenum rated cables are for installing in plenum spaces where cabling is not enclosed in a fireproof conduit.
Riser Cables OFNR (optical fiber nonconductive riser)
A cable that runs vertically between floors of a building. Riser cables must be engineered to prevent fires from spreading between floors.

Outdoor Cable

Cables are hung from telephone poles.
Direct burial
Cables are placed directly in the ground (trench) and buried without addtional protective means.
Indirect burial
Similar to Direct burial but the cables are first placed in some protective space such as a conduit or duct prior to buial.
Submarine
The cable is placed underwater. (Includes transoceanic applications)

Outdoor Cable

• The fiber count in outdoor cable is usually quite high.
• Must be more durable than indoor cable due to the extreme of handling and various climatic changes.
• Most outdoor cables have additional protective sheaths such as steel armoring to prevent rodents from chewing into and damaging the sensitive optical fiber (the actual transmission medium).
• Some outdoor loose-tube buffer cables have the buffer space filled with a protective gel, thus removing any air in the buffering space as well as provide a non-freezing shock absorbing medium of protection. Fibers within this "gel" will not freeze and expand to damage the optical fibers within.

WHY FIBER OPTICS?

Bandwidth

• A fiber optic link is capable of transmitting the entire text of a 30-volume encyclopedia over 100 miles in 1 second!
• Current useful bandwidth up to 10 Gbps carrying 130,000 voice channels (for Single-mode) with repeators needed every 6-15 km(for multimode) and 30-40+ km (for single mode) as opposed to coaxial: up to 90 Mbps (1,344 voice channels) with repeators needed every 1-2 km. *
• Fiber optics permit transmission of channels requiring much greater bandwidth than a voice. Television and teleconfrencing require a channel capacity 14 to 100 times that of a digitally encoded voice (896 kbps-6.4 Mbps)!
• Future systems will probably double the highest rate for fibers and reduce the distance between repeators while a similar advance will not occur for coaxial systems.
• Potential useful range to about 1 THz

*AMP Incorporated, 1987.

LOW LOSS...(1 of 3)

Attenuation
Loss of signal strength as it travels along a transmission path (medium) as expressed in decibels.

• In a copper cable, attenuation increases with modulation frequency; the higher the frequency, the greater the loss.
• In an optical fiber, attenuation is flat: loss is the same at any signalling frequency up to the highest useful ranges (begining around 1 GHz for Multimode graded index and around 10 GHZ for Single mode). The loss at very high frequency ranges is not a result from additional attenuation of the light itself by the optical fiber but is caused by loss of information rather than loss of optical power (signal). Information is contained within the variation of the optical power; as such, at very high frequencies, distortion causes a reduction or a loss of information

LOW LOSS... (2 of 3)

Illustration of attenuation in optical fiber versus copper

LOW LOSS... (3 of 3)

• Severe attenuation requires repeaters to be placed at intermediate points within the transmission path. Generally, in copper cables the repeater spacings decrease as operating speeds increase where as, in optical fiber, the repeater spacings increase along with operating speeds, because efficient low-loss fibers are utilized in high data rate networks.
• Cost Consideration Note: Repeators are costly to build, install, and maintain, thus fewer repeaters may mean lower cost systems.

ELECTROMAGNETIC INTERFERENCE

Electromagnetic Interference
Electromagnetic energy (or electrical noise) originating externally that can disrupt with normal operations of electronic equipment.

ELECTROMAGNETIC INTERFERENCE IMMUNITY

• Cables interconnecting equipment can be one of the main sources of EMI and can also be one of the main receiving antennas carrying EMI into equipment.
• Digital transmission requires that signals be transmitted error free. A burst of EMI (elctromagnetic interference) may appear as a pulse, where no pulse occured in the original pulse stream.

Security

• The two main methods of eavesdropping are: tapping a wire and picking up energy radiated from a wire or electronic equipment. It is virtually impossible to tap an optical fiber without detection. (Recall that optical fiber does not eminate energy to be detected.)

Light Weight

• A fiber weighs considerably less than a copper conductor. A typical single-conductor fiber optic cable weighs 9 pounds per 1000 feet while a comparable coaxial cable weighs approximately 80 pounds per 1000 feet.
• Consider the weight of wire as a factor in large multi-storied buildings where long vertical (between floors) as well as long horizontal runs (between wiring closets and terminals) can create difficulties.

Small Size

• The small size of fiber can be a great benefit where current or anticipated space is a concern such as small plenum spaces and beneath computer room floors.
• A 4.5 in. diameter coaxial cable can carry as many as 40,300 duplex (two-way) conversations over short distances while a fiber optic cable which contains 144 fibers in its 0.5 inch diameter structure, has the capacity to carry 24,192 coversations on each fiber pair or nearly 1.75 million calls on all 144 fibers.

Saftey

• An optical fiber does not attract lightning and is dielectric (does not carry electicity), therefore it presents no spark or hazard that can cause explosions or fires as a faulty copper cable is capable. So an optical fiber can be run through potentially hazardously areas and be run between buildings without fear of lightning.
• (Recall that if copper cabling is run between two buildings, it creates one large circuit. Even if eletro -optical and opto-electrical adaptors are implemented, if the ajoining cable is not buried it still poses a substantial lightning risk.)