Over view of OF Comm

8/7/2019 Over view of OF Comm

1/48

OVERVIEW OF OPTICAL

FIBERCOMMUNICATION


2/48

CONTENTS

OPTICAL FIBER CONCEPT &TYPEFIBER CHARECTERSTICSFIBER CLASSIFICATIONOPTICAL COMMUNICATION ADVANTAGESTRANSMISSION WINDOSTRANSMISSIN CHALLENGESLENGTH OF OFC ROUTEOPTICAL BUDGETSTANDARD FIBER TYPESA TYPICAL OPTICAL FIBER LINKCURRENT TRENDS IN FIBER OPTIC COMMUNICATION-

APPLICATIONMAIN TESTS ON OFCMAIN INSTRUMENTS REQUIREDLAYING OF OPTICAL FIBER CABLE


3/48

Ray Theory:A number of optic phenomena are adequately explained byconsidering light as narrow rays.

The theory based on this approach is called geometrical optics.These rays obey a few simple rules:

1. In a vacuum, rays travel at a velocity of c =3x10 8m/s. In anyother medium, rays travel at a slower speed, given by

v = c/n n =refractive index of the medium.

2. Rays travel straight paths, unless deflected by some change inmedium.3. If any power crosses the boundary, the transmitted ray direction

is given by Snells law:n1 sin i = n2 sin r

Optical Principle

(Internal reflection theory)


4/48

INCIDENT RAYS 1

REFLECTED RAYS

REFRACTED RAYS

1

1

3

2

23

N2 claddingr

i

(principal of total internal reflection)

n1 = 1.48n2 = 1.46

N1 core


5/48

The Optical Fibre

Cladding

125 QmCore8-10 Qm

R efractive index


6/48


7/48

3

21

3

2

1

Light propagation in fibre


8/48

Basic Fibrecore with RI n1supported byconcentriccladding layer withRI n2.RI of core isgreater thancladding (n1 > n2).The cladding layer is surrounded by

one or moreprotective coating.Change in RI isachieved byselectively dopingthe glass perform.

CONSTRUCTION OF OPTICALFIBRE CABLE

CORE

CLADDING


9/48

Modal classification :Similar to metallic wave guides, there are stable propagation states of electromagnetic waves in an optical fiber called modes.

Fibers can be classified based on number of modes available for propagation : - single-mode (SM) fiber.

- Multi-mode (MM) fiber.

Classification based on refractive index profile :step index (SI)Graded index (GRIN) fiber.

CLASSIFICATION OF OPTICALFIBRE


10/48

2a

2a

2a8 - 12 Qm 125 Qm

50 - 200 Qm 125-400 Qm

50 Qm 125-400 Qm

C) Multi mode GRIN fiber

b) Multi mode step-index fiber

a) Single mode step-index fiber


11/48

Transmission Loss Th e trans m ission loss or attenuation of an optical fibre is per h aps t h e m ost i m portant c h aracteristic of t h e fibre; t h isdeter m ines if a syste m is practical. It controls (1) spacing

between repeaters and (2) t h e type of optical trans m itter and receiver to be used.

As lig h t waves travel down an optical fibre, t h ey lose partof t h eir energy because of various i m perfections in t h efibre. Th ese losses are m easured in decibels per kilo m eters(dB/k m ).


12/48

TRANSMISSION WINDOW

F irst Window (850 nm)-laser Ga A s/A l Ga A s and LED andR eceiver -Silicon AP DIt is suitable for S h ort distance

T rans m ission(due to h igh loss in t h isregion)


13/48

T R ANS WI

NDOW-Contd

SEOMD WI N DOW(1 3 10 n m )Moderate loss of Fiber in t h is region

Ch rom atic Dispersion is very weak

Suitable for Long Distance T rans m ission


14/48

FIRSTWINDOW

SECOND WINDOW

THIRD WINDOW

3.0

2.5

2.0

1.5

1.0

0.5

0800 900 1000 1100 1200 1300 1400 1500 1600 1700

TOTAL LOSS

RAYLEIGHSCATTERING

Attenuation Curve

Wave Length (Lemda) in nm

Loss

dB


15/48

SECO N D & TH IR D WI N DOWS FU R TH ER CL A SSIFIED I N FOLOWI N G B AN D OF S P EC R UM

O band Original 1260-1 3 60 n m

E band Extended 1 3 60-1460 n m

S band S h ort wavelengt h s 1460-15 3 0 n m

C band Conventional 15 3 0-1565n m

L band Long Wave lengt h 1565-1625 n m

U band Ultra long wavelengt h 1625-1675 n m

FUR TH

ER

CLA

SSIFIED BAN

D


16/48

5

4

3

2

1

0 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7

~ 190 THz~ 50 THz

OH - OH -

First window

Second window

Third window

Fourth window

Fifth window

Wavelength ( Qm)


17/48

MISSIO N

T R AN

SWI N

DOW-Contd Th ird Window(1550 n m C-band)

Widely used as FIBE R LOSS are very low

EDFA

available in th

isR

egion

Mostly used for T DM &DWDM applications


18/48

T R ANSMISSIO

NWI

NDOW-Contd

SEOMD WI N DOW(1 3 10 n m )Moderate loss of Fiber in t h is region

Ch rom atic Dispersion is very weak

Suitable for Long Distance T rans m ission


19/48

Trans

mission C

hallenges

Trans m ission of lig h t in optical fiber presents several c h allenges. Th ese are:1 A ttenuation2. C h rom atic Dispersion

3 N on linearities-cu mm ulative effects fro m intereaction of lig h r wit h m aterial t h roug h wh ich it travels.


20/48

There are several points in an optic system where losses occur.These are: coupler, splices, connectors and the fiber itself.Losses associated within the fiber classified as under:Losses due to absorption. Even the purest glass will absorb

heavily within specific wavelength regions. Other major sourceof loss is impurities like, metal ions and OH ions.Losses due to scattering: caused due to localized variations indensity, called Rayleigh scattering and the loss is:

L = 1.7(0.85/ P)4 dB/kmP is in micrometers

Losses due to geometric effect: micro-bending. macro-bending.

LOSSES IN FIBER (Attenuation)


21/48

Dispersion - Pulse Spreading

Optical fibres t h at carry data consist of pulses of lig h tenergy following eac h oth er. Th e fibre h as a li m it as toh ow m any pulses per second can be sent to it and beexpected to e m erge intact at t h e ot h er end. Th is is knownas pulse spreading w h ich lim its t h e Bandwidt h of t h e fibre.

Th e pulse sets off down t h e fibre wit h a square wavesh ape. A s it travels along t h e fibre, it progressively getswider and t h e peak intensity decreases.


22/48

SIMGLE MODE FIBER DESIGN

1. Generally long distance network SM mode G-652 (NDSF)is used.

2. It can be used for 1550-nm window, by dispersion

compensators.3. Non dispersion shifted fiber can also support 10 GigabitEthernet standard at distances over 300 meters.

4. Dispersion Shifted Fiber G-6534. G-655 (Non-zero dispersion-shifted) fiber-good for both

TDM and DWDM use in the 1550-nm region.5. PMD and other nonlinear effects are not so critical for

short-haul but they are in long-haul systems with higher speeds.


23/48

Composition of optical fibreSilica based glass or plastic fila m ents are spun

and packed into bundles of several h undreds or th ousands. Bundles m ay be put toget h er as rodsor ribbons and s h eets.

These bundles are flexible and can be twistedand contorted to conduct lig h t and i m ages around

corners

Th e th in glass center of t h e fibre w h ere t h e lig h ttravels is called t h e core.

Th e outer optical m aterial surrounding t h e coreth at reflects t h e lig h t back into t h e core is calledth e cladding.In order to protect t h e optical surface fro m m oisture and da m age, it is coated wit h a layer of

buffer coating.

Cross section of a bundle


24/48

The device which actually converts electrical signals to its opticalequipment.Most common light sources: light-emitting diodes (LEDs) Light Amplification by Stimulated Emission of Radiation (laser)

diodes.It is particularly required in lasers to maintain stable output power by way of feedback mechanism.

Laser is very sensitive to temperature. Operating characteristics of a semiconductor laser-notably threshold, current, output power,and wavelength change with temperature. Hence temperaturesensing and control is required to maintain stable temperature.

OPTICAL SOURCES


25/48

Two main types of cablesStep Index F ibre Th is cable h as a specific index of refraction for th e core and t h e cladding. It causes defor m ationsdue to t h e various pat h s lengt h s of t h e lig h tray. Th is is called m odal distortion. It is t h ech eapest type of cabling. Wit h in t h e cladding andth e core, t h e refractive index is constant.

Graded Index Fibre

In graded index fibre, rays of lig h t followsinusoidal pat h s. A lth ough th e pat h s are differentlengt h s, t h ey all reac h th e end of t h e fibre at t h esam e tim e. Multi m ode dispersion is eli m inated

and pulse spreading is reduced. Graded Indexfibre can h old t h e sa m e a m ount of energy asm ulti m ode fibre. Th e disadvantage is t h at t h istakes place at only one wavelengt h .


26/48

OFC Cable Link Design

Factors needs to be consider Ch oice of fiber

Operating wavelength

T rans m itter power Ch oice of lig h t sourceCh oice of connectorsN um ber of splicesOptical line codeCh oice of cableSyste m design m argin etc.


27/48

POWE

R BUDGE

T

OFC C A BLE LOSS 0. 3 5 Db /k m (includingsplice loss)For C A LCUL AT I N G TH E H OP SEC T IO N LE N GTH (in k m s)

Tx power(db m )- R x sensivity(db m )/0. 3 5


28/48

Th e typical syste m m argin are taken fro m 3 to 6 db Th e difference between t h e TX power and R X sensitivity is t h e power

m argin.Equation of power budget.

P t-(Lcp+Lct+Lsp+Lfb+Msys)>= Srec w h ere:PT = lig h t source trans m itting power, in dB m

Lcp = coupling loss source to fiber, in dBLct= connectors losses (2: source to fibre and fibreto detector); in dB

Lsp = splicing loss, in dBMsys = syste m loss m argin require m ent, in dBSrec = required P D receiver sensitivity, in dB m

Lfb = loss of Fiber cable, in dB m

Link P ower Budget


29/48

Link P ower Budget

Power Budget provides to convenient way to analyzeand quantify losses in a link.

The available power

margin between trans

mitter andreceiver is allocated to:

1. Fiber loss2. Splicing losses3

. Connector losses4. Coupling losses5. Syste m loss m argin


30/48


31/48

OPTICAL FIBRE : TESTS AND MEASUREMENTS.

BY TX-I FACULTY

A.L.T.T.C;GHAZIABAD


32/48

FEATURES BENEFITS * Low TX Loss. * Long repeater Spacing

or R epeater less N /W.* Wide Bandwidt h . * Larger C h l. Capacity* N on-inductive. * N o da m age to Eqpt.

due to surge voltage.* Imm unity fro m * N o sh ielding to Eqpt.

Electro- m agnetic no X -talk or Signalinterference. leakage.

*

Sm

all size,*

Easy to install, bending radius and reduction in spaceligh t weig h t. needed.

* Difficult to tap. * H igh Security andCopper resource savings.

Main Features and Benefits of Optical Fiber Cables


33/48

System Composition

Transmitter E/OC onverterO/E

C onverter Receiver

Application area of Measuring InstrumentsIn Optical F iber C ommunication system

ElectricalSignal Optical

Signal

ElectricalSignal

D ata In D ata Out

D

D

F

D

D

F

FD

F

FD

F


34/48

C able Loss.Splice Loss.C onnector Loss.F ibre Length.C ontinuity of F iber.F ault Localizations/Break F ault.

MAIN TESTS ON OPTICALFIBRE CABLES


35/48

Optical Power Meter.C alibrated Light Source.

Optical Attenuator.Optical Time D omain Reflectometer(OT D R ).

INSTRUMENTS REQUIRED


36/48

G enerates Light signals of knownpower and wavelength (LE D or

LASER).

Wavelength variations to matchF iber's Wavelength.

CALIBRATED LIGHT SOURCE


37/48

TYPES:- F ixed Attenuators. Variable Attenuators.

APPLI C ATIONS:- To Simulate the Regenerator Hop Loss at the FDF . To Provide Local Loop Back for Testing. To measure the Bit Error Rate by varying the Optical

Signal at the Receiver Input.(RE C EIVER SENSITIVITY)

OPTICAL ATTENUATORS


38/48

U sed for measuring F iber Loss. Splice Loss. C onnector Loss. F iber Length. C ontinuity of F iber. F ault Localization.

OPTICAL TIME DOMAIN REFLECTOMETER(OTDR)


39/48

REQUIREMENTS OF

ATTENUATORS Attenuation Range.

Lowest Insertion Loss.

Independent of Wavelength.

Type of C onnectors at the Input and Output.


40/48

OTDR INSTRUMENT PRINCIPLE

F iber

AP D

Signal

Oscilloscope Amplifier

Trigge r

PulseG enerator Laser


41/48

R eflections s h ow O T DR P ulse Widt h and R esolution

Connectors s h ow bot hLoss and R eflections

Splices are usuallynot R eflective.Splices Loss

Slope of trace s h ows Fiber A ttenuation Coefficient

OTDR Trace Information


42/48

Laying of OFC Cable

Trenc h ing:For underground OFC cable laying t h e trenc h ing work isto be first done.Soil categorization:- T o broad categories are t h ere

1. R ocky (wit h blasting or c h iseling)2. Unrocky (ot h er th an rocky)

It m ay be decided by t h e project aut h orities for t h eclassification of soils on t h e basis of t h e actual and

practical execution of trenc h ing.T renc h ing is to be done by m anual or by m ach ine. Th estandards of trenc h ing dept h are as per t h e decided byth e co m panies R &D of Q A branc h .


43/48

In general t h e dept h of t h e trenc h sh ould be better t h an1.65 m eter for non rocky area.

In case of rocky th

em

inim

um

sh

ould be 1.0m

eter or 0.9m eter above t h e pipe.

Laying of OFC Cable

45 c m

3 0 cm

1.65 m eter


44/48

Pipes for cable laying and protection: H DP E pipe are of cable laying of 75 mm outer dia but now a days

P LB/P LP pipes of 200 m eter lengt h are being used for OFC cable

laying. Th e extra protection to t h e cable is also provided in built up area /

h eavy loaded traffic area/ T rain or R oad crossing. Th e protection pipes m ay be of R CC /GI of t h e suitable dia m eter and

lengt h as per require m ent.

Th e all laid route of t h e cables are to be protected by placing t h e stoneslabs/bricks over t h e cable lengt h in non ducted areas.On crossing of river /nalla h e th e cable s h ould be laid in t h e parapetwall of t h e bridge t h roug h GI pipe.

Laying of OFC Cable


45/48

Providing of t h e route indicators (Green color)For identifying t h e OFC route t h e route indicators of t h esuitable size along t h e route at every 200 m eter distanceis provided. Following are inscribed on R I:

1. Co m pany na m e2. R oute na m e3 . R oute kilo m eter/ R I nu m ber

Th e route indicators are m ade of stone slabs of about 1m eter lengt h and 3 0 c m wide, erected along t h e road bywh ich th e OF cable is laid. Th ese are in different coloursas per t h e ch oose of t h e co m pany.

Laying of OFC Cable


46/48

Branc h indicator :It is provided w h enever a route is diverted (spur) fro m th em ain route or any route is going to diverted fro m th e m ainroute to a branc h route.

Splice indicator / Joint indicator :(red color) A t th e m eeting point of two fiber dru m th e joint is to be

m ade for fiber continuity, known as splicing of fiber. A t every dru m lengt h (2k m ) splice is done in t h e m ain h ole

and h ere a indicator is also placed s h owing t h e splicenum ber and route lengt h kilo m eter.

Laying of OFC Cable


47/48

Maintenance of OFC R outes

PH ILOSO PHY

Flexibility to upgrade t h e network in future

Significantly lower costs of failure repairsSpeed of repairs or replacing of OF cableR igh t m aintenance p h ilosop h y can be basedkeeping in m ind rig h t installation practices

ph ilosop h y to generate overall & quality based onconsu m er in ter m s of availibility,reliability anderror perfor m ance.


48/48

Maintenance of OFC

Preparation of faults -restoration kit1 O T DR

2 SP

LICI N

G MA

CH

I N

E 3 Fiber cutter 4 Stipper 5 Joint box/tray wit h sleeve6 Engine alternator 7 P ower cords/boards8 Joint closure/cleaning solutions9 R oute diagra m /fault register

Over view of OF Comm

Documents

Transcript of Over view of OF Comm