Optical fibre communication

Optical fibre communication

SUBMITTED TO: -Mr. Kumar Brijesh Chandra

SUBMITTED BY: - SUDHIR KUMAR 1402071060PRIYANKA CHAUHAN 1402071049

RUBY 1402071053

RANI POOJA 1502073003 SACHIN SINGH CHAUHAN 1402071055

ROHIT 1402071052

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

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.

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

BASIC BLOCK DIAGRAM OF COMMUNICATION SYSTEM

Noise degrades or interferes with transmitted information

Figure: General Model of All Communication Systems

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

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

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.

CHANNEL MULTIPLEXING AND MODULATION

Figure: Multiplexing and Modulation at The Transmitter

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)

CHANNEL MULTIPLEXING AND MODULATION

TIME DIVISION MULTIPLEXING

• MULTIPLE DIGITAL SIGNALS INTERLEAVED IN TIME DOMAIN.

• TIME SLOTS PREASSIGNED TO SOURCES AND FIXED.

MODULATION FORMATSNON-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.

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

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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

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

Optical Communicationamplitude

wavelengthposition/distance

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 = 3108 m/s

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.

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

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.

INTRODUCTIONFIBRE 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.

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.

PRINCIPLE OF OPERATION

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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.

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 05/03/2023 23

DEFINITIONSSPLICER MECHANICAL DEVICE FOR JOINING TWO PIECES OF PAPER

OR FILM OR MAGNETIC TAPESPLICE JOINT MADE BY OVERLAPPING TWO ENDS AND JOINING

THEMSPLICING PROCESS OF THE PERMANENT CONNECTION OF TWO PIECES

OF OPTICAL FIBRES

TYPES OF SPLICING

• MECHANICAL

• FUSION (WELDING)

SCRIBE & BREAK

END PREPARATION

• STRIPING (CABLE JACKET, BUFFER TUBE & COATING)

• CLEAVING

• CLEANING THE END SURFACE

MECHANICAL SPLICING

• BONDING TWO FIBERS TOGETHER IN AN ALIGNMENT STRUCTURE

• TRANSPARENT ADHESIVE

- E.G. EPOXY RESIN

• COMMONLY USED GROOVE

- V-GROOVE

• ALIGNMENT PROBLEMS

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

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

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 lessUsed for short distance Used for long distance

SPLICING LOSSES

• INTRINSIC

- FREZNEL REFLECTION

• EXTRINSIC

- FOREIGN PARTICLES ON SURFACES

• REFLECTION

- INCIDENT AND REFLECTED BEAM TRAVEL ON THE SAME PATH

WHAT DO WE ACHIEVE BY SPLICING?

• CLEAR

• BETTER APPEARANCE

• GREATER STRENGTH

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

FUSION SPLICER

FSM-16S

manufacturer : Fujikura

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

Optical Time Domain Reflectometer

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 connector2. Back scattered light from fibre3. Increase in loss at fusion splice4. Fresnel reflection from fibre end

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

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 DisplayBasic OTDR

block diagram

Fibre

SpliceOptical Coupler

Pulsed Laser

Animation

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

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 % error2 km 13 m 39.6 m20 km 138m 387m40 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

Wide variety of benchtop, handheld and PC based OTDRs availableRanges from single km to 100's of km, resolutions from <1 m to 50 mCost is still high relative to other instrumentation IR£ 10K and higher

Exfo FTB-300 OTDRAvailable at 850, 1310 and 1550 nmCan 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

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.

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.

STRUCTURE OF OPTICAL FIBER

• 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.

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.

TOTAL INTERNAL REFLECTION IN OPTICAL FIBER

CLASSIFICATION OF OPTICAL FIBER

• OPTICAL FIBER IS CLASSIFIED INTO TWO CATEGORIES BASED ON :-1) THE NUMBER OF MODES, AND2) THE REFRACTIVE INDEX

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.

SINGLE MODE OPTICAL FIBERTHIS 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.

• 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.

MULTI MODE OPTICAL FIBRETHIS 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.

REFRACTION AT A PLANE SURFACE

RefractionRefraction is the changing direction of

light when it goes into a material of different density

ON THE BASIS OF REFRACTIVE INDEX

• THERE ARE TWO TYPES OF OPTICAL FIBER:-• (I) STEP-INDEX OPTICAL FIBER• (II) GRADED-INDEX OPTICAL FIBER

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.

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.

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

OPTICAL FIBER COMMUNICATION SYSTEM

Information

source

Electrical source Optical

sourceOptical fiber

cable Optical

detector Electrical receive

Destination

• 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.

• 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.

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.

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 metermodule. Price range: $10,000 - $16,000

SPLICES V. CONNECTORS

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

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

OPTICAL LOSS• EXTRINSIC LOSS

• PROBLEMS THE PERSON DOING THE SPLICING CAN AVOID

• MISALIGNMENT• BAD CLEAVES• AIR GAPS• CONTAMINATION: DIRT, DUST, OIL, ETC.• REFLECTANCE

ACCEPTABLE LOSSESFiber & Joint

Loss (max) Reflectance (min)

SM splice 0.15 dB 50 dBSM connector 1 dB 30 dBMM splice 0.25 dB 50 dBMM connector

0.75 dB 25 dB

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

TESTING REQUIREMENTSParameter Example InstrumentOptical 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 analyzerBackscatter Loss, length,

fault locationOTDR

Fault location OTDR, VFLBandwidth/dispersion Bandwidth tester

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

WAVELENGTHS

• POWER METERS ARE CALIBRATED AT THREE STANDARD WAVELENGTHS• 850 NM, 1300 NM, 1550 NM

• TYPICAL MEASUREMENT UNCERTAINTY IS 5% (0.2 DB)

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

OTDROPTICAL TIME-DOMAIN REFLECTOMETER

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

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

OTDR DISPLAY

Deadzone

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

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

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

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

MICROSCOPE• USED TO INSPECT FIBERS AND

CONNECTORS• PARTICULARLY DURING EPOXY-

POLISH PROCESS

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