The document discusses communication and optical fiber communication. It defines communication as the exchange of information between a source and receiver. Optical fiber communication uses glass or plastic threads called optical fibers to transmit data in the form of light pulses. Fiber optic cables have several advantages over traditional copper cables including very high bandwidth, low signal loss, immunity to electromagnetic interference, and resistance to tapping. The document discusses the basic principles of optical fiber communication including total internal reflection and modulation techniques. It also covers topics such as fiber splicing, optical time domain reflectometry (OTDR) for fault detection, and applications of optical fiber communication.

1. SUBMITTED TO: -
SUBMITTED BY: -
SUDHIR KUMAR 1402071060
PRIYANKA CHAUHAN 1402071049
RUBY 1402071053
RANI POOJA 1502073003

2. WHAT IS COMMUNICATION
COMMUNICATION IS THE PROCESS OF EXCHANGING INFORMATION.
SENDING AND RECEIVING OF MESSAGES FROM ONE PLACE TO
ANOTHER IS CALLED COMMUNICATION.
THE BASIC ELEMENTS INVOLVED IN COMMUNICATION—
1. INFORMATION SOURCE
2. TRANSMITTER
3. COMMUNICATION CHANNEL
4. RECEIVER

3. TYPES OF ELECTRONIC COMMUNICATION
SIMPLEX
THIS TYPE OF COMMUNICATION IS ONE-WAY. EXAMPLES ARE:
• RADIO
• TV BROADCASTING
• BEEPER (PERSONAL RECEIVER)
HALF DUPLEX
THE FORM OF TWO-WAY COMMUNICATION IN WHICH ONLY ONE PARTY
TRANSMITS AT A TIME IS KNOWN AS HALF DUPLEX. EXAMPLES ARE:
• POLICE, MILITARY, ETC. RADIO TRANSMISSIONS
• CITIZEN BAND (CB)
• FAMILY RADIO
• AMATEUR RADIO
FULL DUPLEX
• MOST ELECTRONIC COMMUNICATION IS TWO-WAY AND IS REFERRED TO AS FULL-DUPLEX.
• WHEN PEOPLE CAN TALK AND LISTEN SIMULTANEOUSLY, IT IS CALLED FULL DUPLEX. THE
TELEPHONE IS AN EXAMPLE OF THIS TYPE OF COMMUNICATION.

4. TYPES OF COMMUNICATION
 ANALOG COMMUNICATION
AM, FM, PM ETC.
 DIGITAL COMMUNICATION
ASK, FSK, PSK, QPSK ETC.
 MICROWAVE COMMUNICATION
COMMUNICATION THROUGH RADIO/MICROWAVES/FREQUENCIES
 OPTICAL COMMUNICATION
COMMUNICATION THROUGH LIGHT

5. BASIC BLOCK DIAGRAM OF COMMUNICATION
SYSTEM
Noise degrades or interferes with transmitted information
Figure: General Model of All Communication Systems

6. BASIC CONCEPTS OF
COMMUNICATION
ANALOG SIGNALS
• AN ANALOG SIGNAL IS A SMOOTHLY AND CONTINUOUSLY VARYING VOLTAGE OR CURRENT.
EXAMPLES ARE:
SINE WAVE VOICE VIDEO (TV)
Analog and Digital Signals

7. BASIC CONCEPTS OF
COMMUNICATION
DIGITAL SIGNALS
• DIGITAL SIGNALS CHANGE IN STEPS OR IN DISCRETE INCREMENTS.
MOST DIGITAL SIGNALS USE BINARY OR TWO-STATE CODES.
EXAMPLES ARE:
• TELEGRAPH (MORSE CODE)
• CONTINUOUS WAVE (CW) CODE
• SERIAL BINARY CODE (USED IN COMPUTERS)
Analog and Digital Signals

8. CHANNEL MULTIPLEXING AND
MODULATION
MODULATION AND MULTIPLEXING ARE ELECTRONIC TECHNIQUES
FOR TRANSMITTING INFORMATION EFFICIENTLY FROM ONE PLACE
TO ANOTHER.
MODULATION MAKES THE INFORMATION SIGNAL MORE
COMPATIBLE WITH THE MEDIUM.
MULTIPLEXING ALLOWS MORE THAN ONE SIGNAL TO BE
TRANSMITTED CONCURRENTLY OVER A SINGLE MEDIUM.

9. CHANNEL MULTIPLEXING AND MODULATION
Figure: Multiplexing and Modulation at The Transmitter

10. CHANNEL MULTIPLEXING AND
MODULATION
FREQUENCY DIVISION MULTIPLEXING
• EACH SIGNAL IS MODULATED TO A DIFFERENT CARRIER FREQUENCY
• CARRIER FREQUENCIES SEPARATED SO SIGNALS DO NOT OVERLAP
(GUARD BANDS)

11. CHANNEL MULTIPLEXING AND
MODULATION
TIME DIVISION MULTIPLEXING
• MULTIPLE DIGITAL SIGNALS INTERLEAVED IN TIME DOMAIN.
• TIME SLOTS PREASSIGNED TO SOURCES AND FIXED.

12. MODULATION FORMATS
NON-RETURN-TO-ZERO- IN COMMUNICATION, A NON-RETURN-TO-ZERO
(NRZ) LINE CODE IS A BINARY CODE IN WHICH ONES ARE REPRESENTED BY
ONE SIGNIFICANT CONDITION, USUALLY A POSITIVE VOLTAGE, WHILE ZEROS
ARE REPRESENTED BY SOME OTHER SIGNIFICANT CONDITION, USUALLY A
NEGATIVE VOLTAGE, WITH NO OTHER NEUTRAL OR REST CONDITION.
RETURN-TO-ZERO- (RZ or RTZ) describes a line code used in communications
signals in which the signal drops (returns) to zero between each pulse.

13. OPTICAL FIBER COMMUNICATION
• AN OPTICAL FIBRE CABLE IS A TRANSPARENT THIN FIBER, USUALLY MADE OF
GLASS OR PLASTIC, FOR TRANSMITTING LIGHT. FIBRE OPTICS IS THE BRANCH OF
SCIENCE AND ENGINEERING CONCERNED WITH SUCH OPTICAL FIBRE.
• A TECHNOLOGY THAT USES GLOSS OR PLASTIC THTREAD(FIBRES) TO TRANSMIT
DATA. A FIBRE OPTIC CABLE CONSISTS OF A BUNDLE OF GLASS THREADS, EACH
OF WHICH IS CAPABLE OF TRANSMITTING MESSAGE MODULATED ONTO LIGHT
WAVES

14. 14
Need of Fiber Optic Communications
 Fiber communication promised extremely high data rates,
which allow high capacity transmission quickly.
 It also had the potential for transmission over long
distances without the need to amplify and retransmit along
the way.
 Speed limit of electronic processing, limited bandwidth of
copper/coaxial cables.
 Optical fiber has very high-bandwidth (~30 THz)
 Optical fiber has very low loss (~0.25dB/km @1550nm)
 suitable for long-distance transmission

15. Increase of the bit rate distance
product BL for different
communication Technologies
over time.
Evaluation of Light wave Communication Systems
A figure of merit of communication
systems is the bit rate–distance product,
BL, where B is the bit rate and L is the
repeater spacing.

16. 16
Optical Communication
amplitude
wavelength
position/distanc
e
 electromagnetic wave
 carry energy from one point to another
 travel in straight line
 described in wavelength (usually in mm or nm)
 speed of light in vacuum = 3108 m/s

17. ADVANTAGES OF OPTICAL FIBER
COMMUNICATION
• INCREASED BANDWIDTH AND CHANNEL CAPACITY
• LOW SIGNAL ATTENUATION
• IMMUNE TO NOISE
• NO CROSSTALK
• LOWER BIT ERROR RATES
• SIGNAL SECURITY
• ELECTRICAL ISOLATION
• REDUCED SIZE AND WEIGHT OF CABLES
• RADIATION RESISTANT AND ENVIRONMENT FRIENDLY
• RESISTANT TO TEMPERATURE VARIATIONS ETC.

18. DISADVANTAGES OF OPTICAL FIBER
COMMUNICATION
• SPECIALIST SKILLS NEEDED
• COST OF INSTALLATION
• COST OF TRANSMISSION EQUIPMENT FROM ELECTRICAL TO OPTICAL
SIGNALS
• OPTICAL FIBERS CAN NOT CARRY ELECTRICAL POWER

19. APPLICATIONS OF OPTICAL FIBER
COMMUNICATION
 AS FIBERS ARE VERY FLEXIBLE, THEY ARE USED IN FLEXIBLE DIGITAL CAMERAS.
 FIBERS ARE USED IN MECHANICAL IMAGING I.E. FOR INSPECTION OF MECHANICAL WELDS IN PIPES AND
ENGINES OF ROCKETS, SPACE SHUTTLES, AIRPLANES.
 FIBERS ARE USED IN MEDICAL IMAGING SUCH AS ENDOSCOPES AND LAPAROSCOPES.
 FIBERS CAN BE USED UNDER SEA COMMUNICATION.
 FIBERS ARE USED IN MILITARY APPLICATIONS SUCH AS AIRCRAFTS, SHIPS, TANKS ETC.
 NUCLEAR TESTING APPLICATIONS USE OPTICAL FIBER PHASE SENSORS AND TRANSDUCERS
 FIBERS ARE USED IN PUBLIC UTILITY ORGANIZATIONS LIKE RAILWAYS, TV TRANSMISSION ETC.
 FIBERS ARE USED IN LAN SYSTEMS OF OFFICES, INDUSTRIAL PLANTS AND COLLEGES ETC.
 FIBERS ARE USED IN TELECOMMUNICATION SUCH AS VOICE TELEPHONES, VIDEO PHONES, TELEGRAPH
SERVICES, MESSAGE SERVICES AND DATA NETWORKS.

20. INTRODUCTION
FIBRE OPTIC COMMUNICATION HAS REVOLUTIONISED THE TELECOMMUNICATIONS
INDUSTRY. IT HAS ALSO MADE ITS PRESENCE WIDELY FELT WITHIN THE DATA
NETWORKING COMMUNITY AS WELL. USING FIBRE OPTIC CABLE, OPTICAL
COMMUNICATIONS HAVE ENABLED TELECOMMUNICATIONS LINKS TO BE MADE OVER
MUCH GREATER DISTANCES AND WITH MUCH LOWER LEVELS OF LOSS IN THE
TRANSMISSION MEDIUM AND POSSIBLY MOST IMPORTANT OF ALL, FIBER OPTICAL
COMMUNICATIONS HAS ENABLED MUCH HIGHER DATA RATES TO BE
ACCOMMODATED.
AS A RESULT OF THESE ADVANTAGES, FIBRE OPTIC COMMUNICATIONS SYSTEMS ARE
WIDELY EMPLOYED FOR APPLICATIONS RANGING FROM MAJOR
TELECOMMUNICATIONS BACKBONE INFRASTRUCTURE TO ETHERNET SYSTEMS,
BROADBAND DISTRIBUTION, AND GENERAL DATA NETWORKING.

21. TOTAL INTERNAL REFLECTION
When light traveling in an optically
dense medium hits a boundary at an
angle larger than the "critical angle"
for the media, the light will be
completely reflected. This is called
total internal reflection..Fiber optic
cables use total internal reflection
inside the optical fiber. The light
enters the optical fiber,
and every time it strikes the edge of
the fiber it experiences total internal
reflection. This way the light travels
down the length of the optical
fiber.

22. PRINCIPLE OF
OPERATION
22
Fiber-optic transmission of light depends on preventing light from escaping from the
fiber.
When a beam of light encounters a boundary between two transparent substances,
some of the light is normally reflected, while the rest passes into the new substance.
A principle called total internal reflection allows optical fibers to retain the light they
carry.
When light passes from a dense substance into a less dense substance, there is an angle,
called the critical angle, beyond which 100 percent of the light is reflected from the
surface between substances.

23. PRINCIPLE OF OPERATION
• Total internal reflection occurs when light strikes the boundary between substances at an angle greater than the
critical angle.
• An optical-fiber core is clad (coated) by a lower density glass layer. Light traveling inside the core of an optical fiber
strikes the outside surface at an angle of incidence greater than the critical angle so that all the light is reflected
toward the inside of the fiber without loss.
• As long as the fiber is not curved too sharply, light traveling inside cannot strike the outer surface at less than the
critical angle. Thus, light can be transmitted over long distances by being reflected inward thousands of times with
no loss 12/2/2016 23

24. DEFINITIONS
SPLICER
MECHANICAL DEVICE FOR JOINING TWO PIECES OF PAPER
OR FILM OR MAGNETIC TAPE
SPLICE
JOINT MADE BY OVERLAPPING TWO ENDS AND JOINING
THEM
SPLICING
PROCESS OF THE PERMANENT CONNECTION OF TWO PIECES
OF OPTICAL FIBRES

25. TYPES OF SPLICING
• MECHANICAL
• FUSION (WELDING)

26. SCRIBE & BREAK
END PREPARATION
• STRIPING (CABLE JACKET, BUFFER TUBE & COATING)
• CLEAVING
• CLEANING THE END SURFACE

27. MECHANICAL SPLICING
• BONDING TWO FIBERS
TOGETHER IN AN
ALIGNMENT STRUCTURE
• TRANSPARENT ADHESIVE
- E.G. EPOXY RESIN
• COMMONLY USED GROOVE
- V-GROOVE
• ALIGNMENT PROBLEMS

28. FUSION SPLICING PROCESS
• PHYSICAL PREPARATION
• STRIPPING
• CLEANING
• CLEAVING
• PROTECTIVE SLEEVE
• SPLICING

29. FUSION SPLICING
• FUSING THE TWO FIBERS
• FLAME HEATING SOURCES
- MICRO-PLASMA BURNERS, OXY-HYDRIC
MICRO-BURNERS, ELECTRIC ARC..
• ADVANTAGE
- CONSISTENT AND EASILY CONTROLLED HEAT
WITH ADAPTABILITY
• POSSIBLE DRAWBACK
- WEAKENING OF FIBER IN THE VICINITY OF
SPLICE

30. COMPARISON
Mechanical splicing Fusion splicing
Reflection losses
(-45 db to -55 db)
No reflection losses
Insertion loss
(0.2 db)
Very low insertion loss
(0.1 db to .15 db)
cost – high Comparatively less
Used for short distance Used for long distance

31. SPLICING LOSSES
• INTRINSIC
- FREZNEL REFLECTION
• EXTRINSIC
- FOREIGN PARTICLES ON SURFACES
• REFLECTION
- INCIDENT AND REFLECTED BEAM TRAVEL ON THE SAME PATH

32. WHAT DO WE ACHIEVE BY SPLICING?
• CLEAR
• BETTER APPEARANCE
• GREATER STRENGTH

33. SPLICING? WHY NEEDED
• THERE ARE SEVERAL REASON FOR SPLICING A FIVER CABLE, THESE INCLUDED:
• TO EXTEND A CABLE RUN
• TO JOIN TWO FIBERS DUE TO A BREAKAGE
• TO CONNECT SOME OF THE CORES STRAIGHT THROUGH A PATCH CABINET
• TO GET RID OF CONNECTORS AND REDUCE LOSSES
• OR TO ATTACH A PRE-TERMINATED PIGTAIL(THROUGH DIRECT SPLICING) TO REDUCE LINE
LOSS

34. FUSION SPLICER
FSM-16S
manufacturer : Fujikura

35. SPECIFICATIONS
• APPLICABLE FIBER
• NO. OF FIBERS APPLIED
• SPLICE LOSS
• RETURN LOSS
• CLEAVED FIBER LENGTH
• MAGNIFICATION OF FIBRE
• VIEWING METHOD
• SPLICE LOSS ESTIMATION
• SPLICE RESULT STORAGE
• MECHANICAL PROOF TEST
• POWER SUPPLY
• DIMENSIONS
• WEIGHT

36. Optical Time Domain
Reflectometer

37. Understanding an OTDR Display
Light is reflected back to the OTDR from along the fibre the because of Rayleigh scattering in the fibre
Much larger reflections occur at joints with small airgaps and at the fibre end or at a break
Light reflected back from joints, breaks etc.. produces a spike on the display that looks like "gain".
Indicates joints between fibres with different backscatters
Key to diagram:
1. Fresnel reflection from first connector
2. Back scattered light from fibre
3. Increase in loss at fusion splice
4. Fresnel reflection from fibre end

38. Understanding an OTDR Display
 Light is reflected back to the OTDR from along the fibre the because of Rayleigh scattering in the
fibre
 Much larger reflections occur at joints with small airgaps and at the fibre end or at a break
 Light reflected back from joints, breaks etc.. produces a spike on the display that looks like "gain".
Indicates strong reflection from joint

39. Optical Time Domain
Reflectometry
An Optical Time Domain Reflectometer (OTDR) displays loss in a fibre link as a function of
distance.
Works by transmitting laser light pulses down an optical fibre and by measuring the reflected
light coming back to the OTDR as a function of time and level.
The OTDR converts time to distance and from the returned levels the loss at various distances
is estimated
The result is a display of loss versus distance for the fibre.
APD
Detector
Processing Display
Basic OTDR
block diagram
Fibre
Splice
Optical
Coupler
Pulsed Laser
Animation

40. What can an OTDR provide?
 An OTDR can typically provide the following information:
 total fibre loss
 loss per unit length
 connector insertion loss
 connector return loss (reflection)
 splice loss
 inter-splice loss
 absolute fibre length
 evidence of macro/micro bending
 position of cable defects or breaks

41. OTDR Characteristics
 Distance range: Maximum distance at which the OTDR can detect a reflection
 Two point resolution: Defined as the minimum distance between two reflection points,
such as splices, which can be accurately distinguished
 Resolution depends on a number of factors, for example using a shorter pulse width
improves the resolution.
 Accuracy: Distance accuracy depends on a number of factors, including the refractive
index (IOR) value used:
1.477 2 % error
2 km 13 m 39.6 m
20 km 138m 387m
40 km 271m 775 m
Table shows effect of using
incorrect IOR
Correct IOR is 1.468
All OTDRs have a so called Dead Zone. This is the distance from the OTDR in which the
ODTR is unable to provide accurate measurements. Typically this is 20 m for many modern
OTDRs

42. Wide variety of benchtop, handheld and PC based OTDRs available
Ranges from single km to 100's of km, resolutions from <1 m to 50 m
Cost is still high relative to other instrumentation IR£ 10K and higher
Exfo FTB-300 OTDR
Available at 850, 1310 and 1550 nm
Can be configured with different modules for LAN to
long range distances
Multimode ranges from 0.1 km to 40 km
Singlemode ranges from 625 m to 160 km
Dead zone < than 25 m, Accurate to +/- 1m
Class 1 laser source (eye safe)
Typical OTDR

43. EVOLUTION OF OPTICAL 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.

44. WHAT IS OPTICAL FIBER?
• AN OPTICAL FIBER IS A HAIR THIN CYLINDRICAL FIBER OF GLASS OR ANY
TRANSPARENT DIELECTRIC MEDIUM.
• THE FIBER WHICH ARE USED FOR OPTICAL COMMUNICATION ARE WAVE GUIDES
MADE OF TRANSPARENT DIELECTRICS.
• ITS FUNCTION IS TO GUIDE VISIBLE AND INFRARED LIGHT OVER LONG
DISTANCES.

45. STRUCTURE OF OPTICAL FIBER

46. • CORE – CENTRAL TUBE OF VERY THIN SIZE MADE UP OF OPTICALLY
TRANSPARENT DIELECTRIC MEDIUM AND CARRIES THE LIGHT FORM
TRANSMITTER TO RECEIVER. THE CORE DIAMETER CAN VARY FROM
ABOUT 5UM TO 100 UM.
• CLADDING – OUTER OPTICAL MATERIAL SURROUNDING THE CORE
HAVING REFLECTING INDEX LOWER THAN CORE. IT HELPS TO KEEP THE
LIGHT WITHIN THE CORE THROUGHOUT THE PHENOMENA OF TOTAL
INTERNAL REFLECTION.
• BUFFER COATING – PLASTIC COATING THAT PROTECTS
THE FIBER MADE OF SILICON RUBBER. THE TYPICAL DIAMETER OF
FIBER AFTER COATING IS 250-300 UM.

47. WORKING PRINCIPLE
TOTAL INTERNAL REFLECTION
• WHEN A RAY OF LIGHT TRAVELS FROM A DENSER TO A RARER MEDIUM SUCH
THAT THE ANGLE OF INCIDENCE IS GREATER THAN THE CRITICAL ANGLE, THE
RAY REFLECTS BACK INTO THE SAME MEDIUM THIS PHENOMENA IS CALLED
TOTAL INTERNAL REFLECTION.
• IN THE OPTICAL FIBER THE RAYS UNDERGO REPEATED TOTAL NUMBER OF
REFLECTIONS UNTIL IT EMERGES OUT OF THE OTHER END OF THE FIBER, EVEN IF
THE FIBER IS BENT.

48. TOTAL INTERNAL REFLECTION IN
OPTICAL FIBER

49. CLASSIFICATION OF OPTICAL FIBER
• OPTICAL FIBER IS CLASSIFIED INTO TWO CATEGORIES BASED ON :-
1) THE NUMBER OF MODES, AND
2) THE REFRACTIVE INDEX

50. ON THE BASIS OF NUMBER OF
MODES:-
ON THE BASIS OF NUMBER OF MODES OF PROPAGATION THE OPTICAL
FIBER ARE CLASSIFIED INTO TWO TYPES:
(i) SINGLE MODE FIBER (SMF) AND
(ii) MULTI-MODE FIBER (MMF)
• SINGLE-MODE FIBERS – IN SINGLE MODE FIBER ONLY ONE MODE CAN
PROPAGATE THROUGH THE FIBER. THIS TYPE OF FIBER HAS SMALL
CORE DIAMETER(5UM) AND HIGH CLADDING DIAMETER(70UM) AND
THE DIFFERENCE BETWEEN THE REFRACTIVE INDEX OF CORE AND
CLADDING IS VERY SMALL. THERE IS NO DISPERSION I.E. NO
DEGRADATION OF SIGNAL DURING TRAVELLING THROUGH THE FIBER.
• THE LIGHT IS PASSED THROUGH THE SINGLE MODE FIBER THROUGH
LASER DIODE.

51. SINGLE MODE OPTICAL
FIBER
THIS MODE OF OPTICAL FIBER
ARE USED TO TRANSMIT ONE
SIGNAL PER FIBER (USED IN
TELEPHONE AND CABLE TV).
THEY HAVE SMALL CORES(9
MICRONS IN DIAMETER) AND
TRANSMIT INFRA-RED LIGHT
FROM LASER.
SINGLE-MODE FIBER’S SMALLER
CORE (<10 MICROMETERS)
NECESSITATES MORE EXPENSIVE
COMPONENTS AND
INTERCONNECTION METHODS,
BUT ALLOWS MUCH LONGER,
HIGHER-PERFORMANCE LINKS.

52. • MULTI-MODE FIBER :-
• MULTI MODE FIBER ALLOWS A LARGE NUMBER OF MODES FOR THE
LIGHT RAY TRAVELLING THROUGH IT.
• THE CORE DIAMETER IS (40UM) AND THAT OF CLADDING IS(70UM)
• THE RELATIVE REFRACTIVE INDEX DIFFERENCE IS ALSO LARGER THAN
SINGLE MODE FIBER.
• THERE IS SIGNAL DEGRADATION DUE TO MULTIMODE DISPERSION.
• THEY ARE NOT SUITABLE FOR LONG DISTANCE COMMUNICATION DUE
TO LARGE DISPERSION AND ATTENUATION OF THE SIGNAL.

53. MULTI MODE OPTICAL FIBRE
THIS TYPE OF OPTICAL FIBER ARE USED
TO TRANSMIT MANY SIGNALS PER FIBER
(USED IN COMPUTER NETWORKS). THEY
HAVE LARGER CORES(62.5 MICRONS IN
DIAMETER) AND TRANSMIT INFRA-RED
LIGHT FROM LED.
HOWEVER, MULTI-MODE FIBER
INTRODUCES MULTI-MODE DISTORTION
WHICH OFTEN LIMITS THE BANDWIDTHS
AND LENGTH OF THE LINK.
FURTHERMORE, BECAUSE OF ITS HIGHER
DOPANT CONTENT, MULTIMODE FIBER
IS SOME WHAT MORE EXPENSIVE.

54. REFRACTION AT A PLANE
SURFACE

55. Refraction
Refraction is the changing direction of
light when it goes into a material of
different density

56. ON THE BASIS OF REFRACTIVE INDEX
• THERE ARE TWO TYPES OF OPTICAL FIBER:-
• (I) STEP-INDEX OPTICAL FIBER
• (II) GRADED-INDEX OPTICAL FIBER

57. STEP INDEX FIBER
• THE REFRACTIVE INDEX OF CORE IS CONSTANT
• THE REFRACTIVE INDEX OF CLADDING IS ALSO CONSTANT
• THE LIGHT RAYS PROPAGATE THROUGH IT IN THE FORM OF
MERIDIOGNAL RAYS WHICH CROSS THE FIBER AXIS DURING EVERY
REFLECTION AT THE CORE CLADDING BOUNDARY.

58. GRADED INDEX FIBER
• IN THIS TYPE OF FIBER CORE HAS A NON UNIFORM REFRACTIVE INDEX
THAT GRADUALLY DECREASE FROM THE CENTRE TOWARDS THE CORE
CLADDING INTERFACE.
• THE CLADDING HAS A UNIFORM REFRACTIVE INDEX.
• THE LIGHT RAYS PROPAGATE THROUGH IT IN THE FORM OF SKEW
RAYS OR HELICAL RAYS. THEY DO NOT CROSS THE FIBER AXIS AT ANY
TIME.

60. HOW OPTICAL FIBER’S ARE MADE??
• THREE STEPS ARE INVOLVED IN THE MANUFACTURING OF THE OPTICAL FIBER
WHICH ARE GIVEN BELOW:-
-MAKING A PREFORM GLASS CYLINDER
-DRAWING THE FIBER’S FROM THE PREFORM
-TESTING THE FIBRE

61. OPTICAL FIBER COMMUNICATION SYSTEM
Information
source
Electrical
source Optical
source
Optical fiber
cable
Optical
detector
Electrical
receive
Destination

62. • INFORMATION SOURCE- IT PROVIDES AN ELECTRICAL SIGNAL
TO A TRANSMITTER COMPRISING AN ELECTRICAL STAGE.
• ELECTRICAL TRANSMITTER- IT DRIVES AN OPTICAL SOURCE TO
GIVE AN MODULATION OF THE LIGHT WAVE CARRIER.
• OPTICAL SOURCE- IT PROVIDES THE ELECTRICAL-OPTICAL
CONVERSION .IT MAY BE A SEMICONDUCTOR LASER OR AN LED.

63. • OPTICAL CABLE: IT SERVES AS TRANSMISSION MEDIUM.
• OPTICAL DETECTOR: IT IS RESPONSIBLE FOR OPTICAL TO
ELECTRICAL CONVERSION OF DATA AND HENCE RESPONSIBLE
FOR DEMODULATION OF THE OPTICAL CARRIER. IT MAY BE A
PHOTODIODES, PHOTOTRANSISTOR, AND
PHOTOCONDUCTORS.
• ELECTRICAL RECEIVER: IT IS USED FOR ELECTRICAL
INTERFACING AT THE RECEIVER END OF THE OPTICAL LINK
AND TO PERFORM THE SIGNAL PROCESSING ELECTRICALLY.
• DESTINATION: IT IS THE FINAL POINT AT WHICH WE RECEIVE
THE INFORMATION IN THE FORM OF ELECTRICAL SIGNAL.

64. CONSTRUCTION OF OPTICAL
FIBER
• CORE-THIN GLASS CENTER OF
FIBER WHERE LIGHT TRAVELS.
• CLADDING-OUTER OPTICAL
MATERIAL SURROUNDING THE
CORE.
• BUFFER COATING-PLASTIC
COATING THAT PROTECTS THE
FIBER.

65. PORTABLE OTDR
AGILENT E6000C MINI-OTDR
Dynamic range: 45 dB
Fiber break locator
Multi-fiber testing for fast
high-count cable qualification
Perform power and loss
measurement with the built-in
light source and the power meter
module.
Price range: $10,000 - $16,000

66. SPLICES V. CONNECTORS
• A PERMANENT JOIN IS A SPLICE
• CONNECTORS ARE USED AT PATCH PANELS, AND CAN BE DISCONNECTED

67. OPTICAL LOSS
• INTRINSIC LOSS
• PROBLEMS THE SPLICER CANNOT FIX
• CORE DIAMETER MISMATCH
• CONCENTRICITY OF FIBER CORE OR
CONNECTOR FERRULES
• CORE ELLIPTICITY
• NUMERICAL APERTURE MISMATCH
 THE NUMERIC APERTURE OF THE
TRANSMITTING FIBER IS LARGER THAN
THAT OF THE RECEIVING FIBER

68. OPTICAL LOSS
• EXTRINSIC LOSS
• PROBLEMS THE PERSON DOING THE
SPLICING CAN AVOID
• MISALIGNMENT
• BAD CLEAVES
• AIR GAPS
• CONTAMINATION: DIRT, DUST, OIL, ETC.
• REFLECTANCE

69. ACCEPTABLE LOSSES
Fiber &
Joint
Loss (max) Reflectance
(min)
SM splice 0.15 dB 50 dB
SM connector 1 dB 30 dB
MM splice 0.25 dB 50 dB
MM connector 0.75 dB 25 dB

70. MECHANICAL SPLICING
• MECHANICALLY ALIGNS FIBERS
• CONTAINS INDEX-MATCHING GEL TO TRANSMIT LIGHT
• EQUIPMENT COST IS LOW
• PER-SPLICE COST IS HIGH
• QUALITY OF SPLICE VARIES, BUT BETTER THAN CONNECTORS
• FIBER ALIGNMENT CAN BE TUNED USING A VISUAL FAULT
LOCATOR

71. TESTING REQUIREMENTS
Parameter Example Instrument
Optical power Source output,
receiver signal
level
Power meter
Attenuation or loss Fibers, cables,
connectors
Power meter and
source, or Optical Loss
Test Set (OLTS)
Back reflection or
Optical Return Loss
(ORL)
OTDR or OCWR
(Optical Continuous
Wave Reflectometer)
Source wavelength Spectrum analyzer
Backscatter Loss, length,
fault location
OTDR
Fault location OTDR, VFL
Bandwidth/dispersion Bandwidth tester

72. POWER METERS
• THE POWER METER BY ITSELF CAN BE USE TO
MEASURE SOURCE POWER
• WITH A SOURCE, IT CAN MEASURE THE LOSS OF A
CABLE PLANT, CALLED INSERTION LOSS
• MOST POWER MEASUREMENTS ARE IN THE RANGE
+10 DBM TO -40 DBM
• ANALOG CATV (CABLE TV) OR DWDM (DENSE
WAVELENGTH DIVISION MULTIPLEXING) SYSTEMS
CAN HAVE POWER UP TO +30 DBM (1 WATT)
Image from
lanshack.com

73. WAVELENGTHS
• POWER METERS ARE CALIBRATED AT THREE STANDARD WAVELENGTHS
• 850 NM, 1300 NM, 1550 NM
• TYPICAL MEASUREMENT UNCERTAINTY IS 5% (0.2 DB)

74. SOURCES
• SOURCES ARE EITHER LED OR LASER
• 665 NM FOR PLASTIC OPTICAL FIBER
• 850 NM OR 1300 NM FOR MULTIMODE
• 1310 NM OR 1550 NM FOR SINGLEMODE
• TEST YOUR SYSTEM WITH A SOURCE SIMILAR TO
THE ONE THAT WILL BE ACTUALLY USED TO SEND
DATA

75. OTDR
OPTICAL TIME-DOMAIN
REFLECTOMETER

76. OTDR USES
• MEASURE LOSS
• LOCATE BREAKS, SPLICES, AND CONNECTORS
• PRODUCES GRAPHIC DISPLAY OF FIBER STATUS
• CAN BE STORED FOR DOCUMENTATION AND LATER REFERENCE
• CABLE CAN BE MEASURED FROM ONE END

77. BACKSCATTER
• A SMALL AMOUNT OF LIGHT IS SCATTERED BACK TO THE
SOURCE FROM THE FIBER ITSELF
• SPLICES OR CONNECTOR PAIRS CAUSE A LARGER REFLECTION
OF LIGHT BACK TO THE SOURCE

78. OTDR DISPLAY
Dead
zone

79. OTDR ACCURACY
• OTDR CAN GIVE FALSE LOSS VALUES WHEN COUPLING DIFFERENT FIBERS
TOGETHER
• SPLICES CAN EVEN SHOW MORE LIGHT ON THE OTHER SIDE “GAINER”
• THIS IS AN ILLUSION CAUSED BY INCREASED SCATTERING ON THE OTHER SIDE
• SPLICE LOSS UNCERTAINTY UP TO 0.8 DB

80. VISUAL CABLE TRACERS
AND
VISUAL FAULT LOCATORS
• CABLE TRACER IS JUST A FLASHLIGHT
• VFL USES AN LED OR LASER SOURCE TO GET MORE LIGHT INTO
THE FIBER
• USEFUL TO TEST A FIBER FOR CONTINUITY
• TO CHECK TO MAKE SURE THE CORRECT FIBER IS CONNECTED
• WITH BRIGHT SOURCES, YOU CAN FIND THE BREAK BY LOOKING
FOR LIGHT SHINING THROUGH THE JACKET
• VISIBLE LIGHT ONLY GOES 3-5 KM
THROUGH FIBER

81. FIBER IDENTIFIERS
• BENDS THE FIBER TO DETECT THE
LIGHT
• CAN BE USED ON LIVE FIBER
WITHOUT INTERRUPTING SERVICE
• CAN DETECT A SPECIAL
MODULATED TONE SENT DOWN A
FIBER

82. OPTICAL CONTINUOUS WAVE
REFLECTOMETER (OCWR)
• MEASURES OPTICAL RETURN LOSS (REFLECTANCE) OF CONNECTORS
• INACCURATE ON INSTALLED SYSTEMS BECAUSE IT INCLUDES BACKSCATTER AND
ALL SOURCES OF REFLECTANCE
Cable to
be
Tested

83. MICROSCOPE
• USED TO INSPECT FIBERS AND
CONNECTORS
• PARTICULARLY DURING EPOXY-
POLISH PROCESS

84. ATTENUATORS
• SIMULATES THE LOSS OF A LONG
FIBER RUN
• VARIABLE ATTENUATORS ALLOW
TESTING A NETWORK TO SEE HOW
MUCH LOSS IT CAN WITHSTAND
• CAN USE A GAP, BENDING, OR
INSERTING OPTICAL FILTERS