1. Unit – V FIBRE OPTIC
Dr. Ritesh S. Palaspagar
PRMIT&R

2. HISTORY REPEATS ITSELF
21ST CENTURY TO
FROM ANCIENT GREEKS

3. Transmission medium and physical layer

4. Classes of transmission media

5. Topics discussed in this section:
GUIDED MEDIA
Guided media, which are those that provide a conduit from one device to another, include twisted-pair cable, coaxial cable, and fiber-optic cable.
Topics discussed in this section:
Twisted-Pair Cable
Coaxial Cable
Fiber-Optic Cable

6. Evolution of Fiber 1880 – Alexander Graham Bell
1930 – Patents on tubing
1950 – Patent for two-layer glass wave-guide
1960 – Laser first used as light source
1965 – High loss of light discovered
1970s – Refining of manufacturing process
1980s – OF technology becomes backbone of long distance telephone networks in NA.

7. Why Optical Fibers ?
As mans need and hunger for communication increased, the amount of bandwidth required increased exponentially.
Initially we used smoke signals, then horse riders for communicating. But these ways were way to slow and had very little bandwidth or data caring capacity.
Then came the telephone and telegraph that used copper wires for communication. But soon demand outstripped (included) the capacity and capability of copper wires and data transport got added to voice communication. Then came Coaxial copper cables, VHF and UHF Radios, Satellite but demand still outstripped the supply.
It was not until Optical Fibers came on the scene that large amount of communication bandwidth became economically and easily available to everyone.
As an example 50,000 voice / data circuit copper cable is massive in size and very expensive, while a single Optical Fiber, the diameter of human hair, can carry 5,00,000 circuits of voice and data. This capacity is increasing day by day as supporting electronics is developing. In itself the capacity of Optical Fibers is limitless.

8. INTRODUCTION
Traditionally the communication was done with the help of copper wires. now a days it has been replaced by fibre optic cable.
The difference between two system is that the fibre optics system uses light pulses to transmit information instead of using electronic pulses as used in copper wire system.
Here a LED or ILD is used for generating the light pulses. Using lense the light pulses are transmitted into fibre optics system.

9. How are Optical Fibre’s made??
Three Steps are Involved
-Making a Preform Glass Cylinder
-Drawing the Fibre’s from the preform
-Testing the Fibre

10. Testing of Optical Fiber
Tensile Strength
Refractive Index Profile
Fiber Geometry
Information Carrying Capacity
Operating temperature/humidity range
Ability to conduct light under water
Attenuation

11. Wavelength of Transmitted Light

12. PRINCIPLE
Light pulses move easily in fibre optic cable because of the principle known as total internal reflection (T.I.R).
CONDITION FOR T.I.R
Light should travel from denser medium to rarer medium.
Angle of incidence is greater than the critical angle.
Transparent glass or plastic fibre which allow light to be transmitted from transmitter to receiver with minimal loss.

13. Fiber optics: Bending of light ray

14. TOTAL INTERNAL REFLECTION

15. CONSTRUCTION

16. CONSTRUCTION… Core Cladding Buffer Jacket
Glass or plastic with a higher index of refraction than the cladding
Carries the signal
Cladding
Glass or plastic with a lower index of refraction than the core
Buffer
Protects the fiber from damage and moisture
Jacket
Holds one or more fibers in a cable
CONSTRUCTION…

17. Fiber CONSTRUCTION…

18. Propagation modes

19. Modes

20. DESCRIPTION STEP INDEX FIBRE
IT IS AN OPTICAL FIBRE WHOSE CORE HAS A REFRACTIVE INDEX WHICH IS SLIGHTLY GREATER THAN THAT OF CLADDING.
BECAUSE OF REFRACTIVE INDEX OF THIS TYPE THE FIBRE MAKES A STEP CHANGE A CORE CLADDING INTERFACE.

21. SINGLE MODE STEP INDEX DIAMETER VARIES FROM 8.3 - 10 MICRON.
BANDWIDTH IS HIGHER THAN MULTIMODE.
IT GIVES HIGHER TRANSMISSION RATE.
NO OVERLAPPING,DISTORTION OF LIGHT PULSES OCCUR WITH LEASTY ATTENUATION.

22. MULTIMODE STEP INDEX DIAMETER VARIES FRM 50 - 100 MICRON.
MUCH LARGER PORT DIAMETER.
EASY TO SPLICE AND COUPLE SERGMENTS TOGETHER WITH MINIMAL LOSS.
MULTIPATH DISPERSSION IS PRESENT.
RAYS WITH SMALL ANGLE OF INCIDENCE REACH THE RECIEVER AFTER THOSE RAYS WHICH ARE LARGER ANGLE OF INCIDENCE.

23. MULTI MODE (CONT.)

24. GRADED INDEX
CONTAINS A CORE IN WHICH R.I GRADUALLY DECREASES FROM CORE TO CLADDING.
THE HIGHER R.I AT THE CORE MAKES THE LIGHT RAY MOVING DOWN THE AXIS ADVANCE MORE SLOWLY THAN THOSE NEAR CLADDING.
HERE LIGHT RAYS MOVE IN HELICAL PATH INSTEAD OF ZIGZAGGING DUE TO GRADED INDEX , HENCE REDUCING TRAVELLING TIME.

26. Fiber Optic Specifications
Attenuation
Loss of signal, measured in dB
Dispersion
Blurring of a signal, affects bandwidth
Bandwidth
The number of bits per second that can be sent through a data link
Numerical Aperture
Measures the largest angle of light that can be accepted into the core

27. Attenuation
Modern fiber material is very pure, but there is still some attenuation
The wavelengths used are chosen to avoid absorption bands
850 nm, 1300 nm, and 1550 nm
Plastic fiber uses 660 nm LEDs

28. Optical fiber performance

29. Three Types of Dispersion
Dispersion is the spreading out of a light pulse as it travels through the fiber
Three types:
Modal Dispersion
Chromatic Dispersion
Polarization Mode Dispersion (PMD)

30. Modal Dispersion Modal Dispersion
Spreading of a pulse because different modes (paths) through the fiber take different times
Only happens in multimode fiber
Reduced, but not eliminated, with graded-index fiber

31. Chromatic Dispersion
Different wavelengths travel at different speeds through the fiber
This spreads a pulse in an effect named chromatic dispersion
Chromatic dispersion occurs in both singlemode and multimode fiber
Larger effect with LEDs than with lasers
A far smaller effect than modal dispersion

32. Polarization Mode Dispersion
Light with different polarization can travel at different speeds, if the fiber is not perfectly symmetric at the atomic level
This could come from imperfect circular geometry or stress on the cable, and there is no easy way to correct it
It can affect both singlemode and multimode fiber.

33. Numerical Aperture
If the core and cladding have almost the same index of refraction, the numerical aperture will be small
This means that light must be shooting right down the center of the fiber to stay in the core

34. MERITS
SPEED : FIBRE OPTIC NETWORK OPERATE AT HIGH SPEED UPTO GIGABYTES.
DISTANCE : FIBRE OPTIC CABLE CAN COMMUNICATE OVER A LONG DISTANCE.
COST : MUCH LESS AS COMPARED TO OTHER TRANSMITTING MEDIA.

35. MERITS(CONT.)
BAND WIDTH : FIBRE OPTIC CABLES HAVE MUCH GREATER BANDWIDTH THAN METAL CABLES.
LESS WEIGHT :IT IS LESS WEIGHER THAN COPPER WIRE.
SECURITY :IMPOSSIBLE TO TAP INTO A FIBRE OPTICS CABLE, MAKING IT MORE SECURE.
BECAUSE OF NO ELECTRICITY THROUGH OPTICAL FIBRE IT IS NON FLAMABLE.
DATA CAN BE TRANSMITTED DIGITALLY.

36. DEMERIT FIBRE OPTIC CABLE ARE EXPENSIVE TO INSTALL.
THE TERMINATION OF FIBRE OPTIC CABLE IS COMPLEX.
THEY ARE MORE FRAGILE THAN COAXIAL CABLE

37. APPLICATION TELE COMMUNICATION CABLE TV
IT INDUSTRY (HIGH SPEED LAN WIRES)
INTERNET
INDUSTRIAL PLANT

38. CONCLUSION
THE AGE OF OPTICAL COMMUNICATION IS A NEW ERA. IN SEVERAL ASPECTS FIBREOPTICS COMMUNICATION IS BETTER THAN ELECTRIC COMMUNICATION.
WITH A BANDWIDTH AND INFORMATION CAPACITY A THOSAND TIMES GREATER THAN COPPER WIRES, FIBRE OPTICS WILL SOON PROVIDE US WITH ALL COMMUNICATION TECHNOLOGY AT A COST EFFICIENT PRICE.

39. Thank You