FIBER OPTIC CABLE COURSE1.Overview of communication medias.2.Refraction&reflection of light.3. Fiber optic communication system.4.Optical fiber source & detector.5.Definition & type of F.O.6.Fiber optic structure.7.Installation of F.O.C.8.Optical fiber connections.9.Definition & types of attenuation.10. Measurement methods.11. Attachment photos.12. Practical parts(O&M,splicing, testing……etc.

FIBER OPTIC CABLE COURSE– Over view of communication medias:-

• Introduction:-• There are four types of media that can be used in

transmitting information in telecommunications system, which are:

1. Copper wire2. Coaxial cable (actually an adaptation of copper wire)3. Wireless4. Fiber optic

Disadvantages of Copper cable • Too expensive with respect to fiber optic cable.• need many pipes to be installed for pulling in the

cable.• Always exposed to be theft due to its high

commercial price.• Need to install in short distances as a

communication system.• Low carrying capacity (small bandwidth).• Can be affected with interference , crosstalk & other

neighboring circuit (as happened in wireless medias).

Advantages of fiber optic cables: • SPEED: Fiber optic networks operate at high speeds - up into the gigabits.• BANDWIDTH: large carrying capacity.• DISTANCE: Signals can be transmitted further .• RESISTANCE: Greater resistance to electromagnetic noise

such as radios, motors or other nearby cables. • Small size & weight(many KM’s can be delivered)• MAINTENANCE: Fiber optic cables costs much less to

maintain.

Refraction & reflection of light

• As a light ray passes from one transparent medium to another, it changes direction; this phenomenon is called refraction of light.

• How much that light ray changes its direction depends on the refractive index of the mediums.

Total internal reflection:Light pulses move easily down the fiber-optic line because of a principle known as total internal

reflection. "This principle of total internal reflection states that when the angle of incidence exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in. When this principle is applied to the construction of the fiber-optic strand, it is possible to transmit information down fiber lines in the form of light pulses.

Refractive index (n) of the medium: -This can be define as, is the ratio of the speed of light in vacuum (air) (Cn=1) to the

speed of light in the medium) (e.g. glass, for the glass n=1.5). n=C/VWHERE: C= is the velocity of light in the vacuum, which is constant(300000 km/s). V= is the velocity of light in glass, which depends on the density of the glass.Snells law:C1/C2= n2/n1C1= first medium( AIR), C2 = second medium GLASS).n2=second medium(1.5), n1= first medium(1).THERE FOR C for the glass is:Cg= 300000 km/s X 1/ 1.5=200000 km/s. Also there is basic relation between C , f & λ which is:C= f x λ.WHERE : C= is the speed of propagation. f= frequency. λ = wave length. (windows wavelengths for the for the light in fiber optic

which is in the range of 800 nm – 1700 nm).

Refraction Index• The index of refraction (n) is the ratio of the speed of

light in a vacuum (c) to its velocity in a material (v)– n = c / v

• Light changes speed (and bends) as it passes through different mediums

Material Index (n) Light speed (km/s)Vacuum 1.0 300 000

Water 1.33 225 000

Glass 1.5 200 000

Diamond 2.0 150 000

Frequency Hz

1800 1600 1400 1200 1000 800 600 400 200

2x1014 3x1014

5x1014

1x1015

Infraredrange

Ultravioletrange

wavelength nm

Visible range

single mode Laser

multi mode Laser

Laserrange

Radarrange

Wavelength range of optical transmission

Fiber optic communication system:• Fiber-optic communication is a method of transmitting information from one

place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information. First developed in the 1970s, fiber-optic communication systems have revolutionized the telecommunications industry and have played a major role in the advent of the Information Age. Because of its advantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networks in the developed world.The process of communicating using fiber-optics involves the following basic steps: Creating the optical signal involving the use of a transmitter, relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak, receiving the optical signal, and converting it into an electrical signal.

Optical communication system

Optical source and detectors: -• (1) Optical source:• Optical sources (transmitters) are an electronic components used to

convert the electrical signal to optical signal and send it through optical fibers after certain modulation to the signal. The most optical sources used in modern fiber optic system are laser diode (LD) and light emitting diode (LED), the advantages of these two diode are so small and more suitable for simple electronic energy.

• But generally we use light emitting diode for short distances and laser diode long distances. The word LASER stands for, Light Amplification by Stimulated Emission Radiation.

• The LDs and LEDs are operated infrared portion of electromagnetic spectrum, so their light out put usually invisible to the human being eye. Their operating wavelengths are chosen to be compatible with the lowest transmission loss and high sensitivity ranges of photodiodes. These wavelengths are 850 nm, 1310 nm and 1550 nm.

(2)Optical detectors:-• The optical detectors (receivers) convert the optical

signal back into original electrical signal.• The detector of the optical signal is either PIN-type

photo diode or avalanche type photo diode. The photo diode demodulates an optical signal by generating a current proportional to the intensity of electrical signal.

• For the area of operation in fiber optic transmission system where long distances transmission (greater than 100km), we use avalanche photo diode because it is designed for applications requiring greater sensitivity.

•Definition of O.F: -Physically optical fiber is a very thin flexible medium having solid cylindrical waveguide consisting of three layers, which are:1. The core.2. The cladding.3. The coating or jacket.

Types of F.O.:-There are three types of fiber optic commonly used: single

mode, multimode and plastic optical fiber (POF).Transparent glass or plastic fibers which allow light to be guided from one end to the other with minimal loss.

Types of fiber optic:• Single Mode cable is a single stand of glass fiber with

a diameter of 8.3 to 10 microns that has one mode of transmission. Single Mode Fiber with a relatively narrow diameter, through which only one mode will propagate typically 1310 or 1550nm. Carries higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width. Also single mode can be called as mono-mode optical fiber, single-mode fiber, single-mode optical waveguide, uni-mode fiber. Has a cladding diameter of 125 microns & coating or jacket diameter of 250 microns.

Single mode fiber:• Means only one single united beam running or

passing through the core and taking the center of it from first to end.

• Used for long distance applications(according to Tx equipment type).

• Multimode cable is made of of glass fibers, with a common diameters in the 50-to-100 micron range for the light carry component (the most common size is 62.5). POF is a newer plastic-based cable which promises performance similar to glass cable on very short runs, but at a lower cost.

Multimode fiber gives you high bandwidth at high speeds over medium distances. Light waves are dispersed into numerous paths, or modes, as they travel through the cable's core typically 850 or 1300nm. Typical multimode fiber core diameters are 50, 62.5, and 100 micrometers. However, in long cable runs (greater than 3000 feet [914.4 meters), multiple paths of light can cause signal distortion at the receiving end, resulting in an unclear and incomplete data transmission.

1. STEP-INDEX MULTIMODE FIBER has a large core, up to 100 microns in diameter. As a result, some of the light rays that make up the digital pulse may travel a direct route, whereas others zigzag as they bounce off the cladding. These alternative pathways cause the different groupings of light rays, referred to as modes, to arrive separately at a receiving point. The pulse, an aggregate of different modes, begins to spread out, losing its well-defined shape. The need to leave spacing between pulses to prevent overlapping limits bandwidth that is, the amount of information that can be sent. Consequently, this type of fiber is best suited for transmission over short distances, in an endoscope, for instance.

2. GRADED-INDEX MULTIMODE FIBER contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. Also, rather than zigzagging off the cladding, light in the core curves helically because of the graded index, reducing its travel distance. The shortened path and the higher speed allow light at the periphery to arrive at a receiver at about the same time as the slow but straight rays in the core axis. The result: a digital pulse suffers less dispersion.

Fiber cable structure

• Definitions:• Cabling is the process of packaging optical fibers in a solid

tube (called sheath) for ease of working activities ,handling & protection.

• From point of usage ,fiber cable had been classified in two categories, one for external plant covered with the sheath called polythene(PE) & other for internal installation covered with flexible sheath called polyvinyl chloride (PVC).

• Also according to the type of the fiber, the cable can be classified to single & multi mode cable.

Fiber cable manufacturing:• Fiber cable normally manufacturing in different

style structure:1. One called maxi-tube cable, in which all fibers

were inserted inside one tube situated in the middle of the cable.

2. Another type called loose buffered tube cable , in which all fibers were divided in to many colored tubes in the cable, situated in circular shape , in addition to another elements called fillers to keep the circularity shape of the cable.

Maxi-tube cable

P.E sheath

corrugated sheath

Jelly filling compound

Ripcord

fibers

Maxi-tube

Buffer tube cable

Samples of fiber cables• Direct buried cable • Submarine cable

Installation of optical fiber cables:-• The fiber optic cables installed in a pipe called

conduit system for more protection and ease of maintenance. There is pulling tool used to withdraw the cable in the conduit system, also there are manholes and hand holes used to ease the pulling of the cable and storing the connection point of the cable. Some times outside plant cable are directly laid in the ground after digging deep in the ground and back filling again, and this can decrease the cost of the installation.

Installation methods• Installation methods for both copper

cables and optical fiber cables are similar. • Fiber cable can be pulled with much greater

force than copper wire if pulled correctly.• Long distances laying mean cables are

spliced together, since cables are not longer than about 4 km.

• Most splices are by fusion splicing.

Do not pull on the fibers

• Pull on the strength members only! Any other method may put stress on the fibers and harm them.

• Most cables cannot be pulled by the jacket.• Do not pull on the jacket unless it is specifically

approved by the cable manufacturers and you use an approved cable grip.

Do not exceed the cable bend radius.

• Fiber is stronger than steel when pulled straight, but it breaks easily when bent too tightly.

• These will harm the fibers, maybe immediately, maybe not for a few years, but they may be harmed and the cable must be removed and thrown away!

Conduit and Inner-duct.• Outside plant cables are either installed in conduit or inner-duct or

direct buried, depending on the cable type. • Building cables can be installed directly, but can be put inside

plenum-rated inner-duct.• This inner-duct will provide a good way to identify fiber optic cable

and protect it from damage, generally a result of someone cutting it by mistake!

• The inner-duct can speed installation and maybe even cut costs. • It can be installed quickly by unskilled labor, then the fiber cable can

be pulled through in seconds. An inner-duct may have a pulling tape already installed.

Optical fibers connections:-Definition:

• The purpose of fiber termination is to provide easy ways for fiber cross connection and light wave signal distribution. There are two types of fiber terminations: connectors and splicing.

• Splicing:• Splicing is the process of connecting two bare fibers directly without any

connectors. There are two methods of fiber optic splicing: mechanical splicing and

fusion splicing.

Fusion splicing techniques:-This type of connection is done by a certain machine called fusion splicer , this splicer is the microprocessor machine used to produce a fixed low loss connection between the two fibers. This splicing is done, in the manner as heating, melting and then two fiber fused together. When the two fibers are totally fused, the machine displays a certain value of attenuation for this fused point. This fusion process is shown in the figure below:-

fusion splicer

Fiber end mismatches

• Mechanical connections: - In this type the two fibers are mechanically connected together, this can be done by two methods:

1. Sleeves method: In this method the two fibers coatings are stripped out of the fiber and cleared with ALCOHOL and then cleaved (cut) with certain cleaving lengths, and then the two end of the fiber are inserted in one sleeve and then pressed with the certain tool.

2. Connector method: The two fibers are already prepared in screw connector or any other form and then approached together in female connector and then tightly closed.

• Closures:-• Are solid tubes or containers used to protect the fibers at the

point of connection of two cables, manufactured from solid plastic material.

Definition & causes of attenuation• is the decrease (loss) in magnitude of the signal power in

transmission between points.• Attenuation usually measured in decibel (dB) at specific

wavelength.• As light is guided through the core of a fiber, four properties can

cause attenuation:1.Absorption:• Occurs when light strikes impurities in core glass and is

absorbed.2.Scattering:• Occurs when light strikes an area where the material density

changes.3.Macrobending:• Is large scale bending of the fiber bend which exceeds the fiber

bend radius and causes light to leave the core and travel in the cladding (usually an installation problem).

4.Micro bending: Is microscopic distortion of the fiber, which causes light to leave the core and travel in the cladding (created during manufacturing).

• Link loss (dB) = Cable loss + Connectors loss + Splices loss.

• Cable loss (dB) = Cable length (km) x Loss coefficient (dB/km)*

• Connector loss (dB) = number of connector pairs x connector loss (dB)*

• Splice loss = number of splices x splice loss (dB)*.

• Accepted attenuation range:• At 1310 nm should be in the range of 0.30 dB/km

to 0.35 dB /km.• At 1550nm , should be in the range of 0.20 dB

/km to 0.25 dB /km.

Acceptable link loss calculation

Measurements methods:1. transmission method:

• The simplest and most accurate method of measuring the end-to-end loss of an optical fiber is done by light source and power meter. Shown here above is the proper method for storing reference and then measuring loss.

• Multimode and single mode optical measurements can be done perfectly by this method .

Link Loss measurements

2.Back scattering method

LCD

• The optical time domain reflectometer (OTDR), sends out a pulse of light and measures the level of light that is reflected back. An optical coupler allows both optical source and optical receiver to be connected to the same fiber.

CONTROLLER

LASER SOURCE

DETECTOR

Coupler/ splitter

Fiber under test

Pulse width

O.T.D.R– TYPICAL BACKSCATTERED TRACE

Fusion spliceConnector Fibreend

O.T.D.R

Att (

dB )

Dist (Km )

O.T.D.Rconnector

Noise

Rayleighscattering

Fresnelreflection

Mechanicalsplice

Visual fault locator• A "visual fault locator". It injects a bright red laser

light into the fiber to find faults. If there is a high loss, such as a bad splice, connector or tight bend stressing the fiber, the light lost may be visible to the naked eye. This will find events close to the OTDR or close to another event that are not resolvable to the OTDR. It's limitation is distance too, it only works over a range of about 2.5 miles or 4 km.

•  The visual fault locator is so valuable a tool that many OTDRs now have one built into them.

Attenuation & Dispersion

Input pulse

Output pulse

Attenuation () : the signal received is less than the transmitted.

Modal dispersion (Bandwidth limitation) : the signal is widen due to different propagation times (T)

W0 TW0

Transmitted pulse fiber Received pulse

Attenuation: the loss of signal in the fibre (e.g., 0.2 dB/km)

Dispersion:-• Dispersion: is the spread and broadening pulse of light as it is guided through the fiber.• There are four types of dispersion:-• Modal dispersion: occurs when various modes of light follow different paths through the

fiber and arrive at the far end at different times. It occurs only in multimode fibers.• Material (or chromatic ) dispersion: occurs because different wave lengths (colors) of light

travel at different velocities through the fiber. • Wave guide dispersion: occurs because light travels in both the core and cladding at slight

different speeds. It is most significant in single-mode fibers.• Polarization mode dispersion: occurs when the X and Y polarization states of a light signal

travel at different speeds through a fiber. This is similar to MODAL dispersion except that it can be significant in single – mode fiber.

• The unit of dispersion for single mode step index fiber is• Ps/ km.nm • While the unit of dispersion for multimode step index and graded index is the MHz.

Gradient Index Glass slows down the faster light modes and speeds up the slower ones

Core

CladdingInput pulse

Output pulse

Source

Ray of light

MULTIMODE GRADED INDEX62.5 / 125 µm (Core / Cladding)

• Dispersion – Modus dispersion or Modal Delay (4000

different modes)

140 µm

100 µm

Multimode Step-Index

SINGLEMODE STEP INDEX

Core

CladdingLaser

Ray of light

Input pulse

Output pulse

No dispersion9 / 125 µm (Core / Cladding)

Patch cords:

SC-SC UPC 9/125µm Single mode Simplex Patch Cord

SC-SC UPC 9/125µm Single mode Duplex Patch Cord

LC-LC UPC 9/125µm Single mode Simplex Patch Cord

LC-LC UPC 9/125µm Single mode Duplex Patch Cord

Single mode adapters:

SC Single mode Duplex AdapterSC Single mode Simplex Adapter

LC Single mode Duplex AdapterLC Single mode Simplex Adapter

Fiber optic closure

• Fiber color code system

1. Blue 2. Orange3. Green 4. Brown5. Gray6. White7. Red 8. Black9. Yellow10. Violet11. Pink12. Aqua

Pigtails & Patch cords:

FSM-50S –Fujikura FUSION SPLICER

TOOL KIT: tools used for cable preparation

Fiber optic maintenance workshop tools & equipments:

No. item quantity

1 Human resources At least 3 persons(one Eng. &two Technicians)

2 (closed environment) 4-wheel drive car 1

3 Optical time domain reflectometer 1

4 Splicing machines 2

5 Cable preparation tool kit for cable jointing 1

6 Closures 4

7 Fiber optic cable (required capacity) At least 300m

8 Generator(3kw) 1

9 Electric cable(reel of 25 m) 1

10 Electric lamp(for light during night) 2

11 Optical set(light source &power meter 1

12 Pig tails & patch cord 2 (for each)

13 Movable flash light 2

THANKS