For BSNL Internal Circulation only

E2-E3

E&WS

OVERVIEW OF OFC NETWORK

For BSNL Internal Circulation only

WELCOME

• This is a presentation for the E2-E3 E&WS

Module for the Topic: Overview of OFC Network

• Eligibility: Those who have got the Upgradation

from E2 to E3.

• This presentation is last updated on 15-3-2011.

• You can also visit the Digital library of BSNL to

see this topic.

For BSNL Internal Circulation only

AGENDA

• OPTICAL FIBER CONCEPT &TYPE

• OFC ROUTE & OPTICAL BUDGET

• IMPORTANT OFC TEST INSTRUMENT

• USE OF OFC in BSNL& LAYING PRACTICE

For BSNL Internal Circulation only

OPTICAL FIBER CONCEPT&TYPE

1. Main job of optical fibre is to guide light waveswith a minimum attenuation.

2. Optical fibers are composed of fine threads ofglass in layers. The fine threads are of silicaglass mix with some dopant material.

3. Two main layers are known as core (central, of8 to 50 m ) & cladding (outer ,50 to125 m)

4. Core is having 1% more R.I. than Cladding

5. It transmits the Optical waves (Light) through itat the speed of 2/3 of speed of light in vacuumobserving the total internal reflection principle.

For BSNL Internal Circulation only

The Optical Fibre structure

Cladding

125 mCore 8-50 m

For BSNL Internal Circulation only

1. Light is either reflected or refracted depending

upon the angle of incident at which it strikes the

layer of separation.

2. It refracts away when it goes from denser to a

rearer medium

3. It reflects when it crosses the critical angle,

which is known as phenomenon of

TOTAL INTERNAL REFLECTION

For BSNL Internal Circulation only

INCIDENT RAY 1

Reflected Ray

Refrected Ray

1

1

3

2

2

3

N2 cladding

¢r

¢i

(Principal of total internal reflection)

n1 = 1.48

n2 = 1.46

N1 core

For BSNL Internal Circulation only

Jacket

Cladding

Core

Cladding

Angle of

reflection

Angle of

incidence

Light at less than

critical angle is

absorbed in jacket

Jacket

Light is propagated by

total internal reflection

Jacket

Cladding

Core

(n2)

(n2)

Fig. Total Internal Reflection in an optical Fibre

For BSNL Internal Circulation only

Classification based on Mode of propogation

Fibres can be classified based on numbers available for propagation :

1- Single-mode (SM) fiber.

2.- Multi-mode (MM) fiber.

Classification based on refractive index profile :

1. Step index (SI)

2. Graded index (GRIN) fiber.

CLASSIFICATION OF OPTICAL FIBRE

For BSNL Internal Circulation only

.NON DISPERSION SHIFTED FIBRE-NDSF-G652

. DISPERSION SHIFTED FIBRE-

DSF-G653

.NON ZERO DISPERSION SHIFTED FIBRE-

NZDSF-G655

SINGLE MODE FIBER DESIGNS:-

For BSNL Internal Circulation only

MULTIMODE( LARGE CORE DIA.)

Number of modes results in delay in receiving end :

1. Modal dispersion

2. Resulting reduction in bandwidth- width.

3. Resulting limits the distance of transmission.

4.To overcome modal dispersion core gradded refractive index fibres are used.

For BSNL Internal Circulation only

Two main types of cables

For BSNL Internal Circulation only

Advantage of optical comm.

High speed of transmission >10ghz

Low loss system can work >1okms

Large no.Channels signal can be

amplified in single fibre trans.

Low cost of transmission

Light in weight

Immune to EMI being non conductive

For BSNL Internal Circulation only

FIRST

WINDOW

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

RAYLEIGH

SCATTERING

Attenuation Curve

Wave Length (Lemda) in nm

Loss

dB

For BSNL Internal Circulation only

TRANSMISSION WINDOWS

First Window (800-900 nm)

Transmitter laser GaAs and LED and

Receiver -Silicon APD

It is suitable for Short distanceTransmission(due to high loss in this region)

For BSNL Internal Circulation only

TRANS WINDOW-Contd

SECOND WINDOW (1250 to 1350 nm)

Moderate loss of Fiber in this region

Chromatic Dispersion is very weak

Suitable for Long Distance Transmission

For BSNL Internal Circulation only

Transmission Window -Contd

Third Window(1500 nm C-band)

Widely used as FIBER LOSS are very low

Euro doped Fibre Amp. available in thisRegion

Mostly used for WDM & DWDM applications

For BSNL Internal Circulation only

SECON & THIRD WINDOWS FURTHER CLASSIFIEDIN FOLLOWING BAND OF SPECTRUM

FURTHER CLASSIFIED BAND

O band Original 1260-1360 nm

E band Extended 1360-1460 nm

S band Short wavelengths 1460-1530 nm

C band Conventional 1530-1565nm

L band Long Wave length 1565-1625 nm

U band Ultra long wavelength 1625-1675 nm

For BSNL Internal Circulation only

TRANSMISSION CHALLENGES

Several challenge that must be dealt with

(1) ATTENUATION: Decaying of signals.

i) INTERINSIC

ii) EXTRANSIC

(2)DISPERSION: Spreading of light pulses.

i) MODAL,

ii) MATERIAL,

iii) WAVE GUIDE

For BSNL Internal Circulation only

Length of the OFC route &

optical budget

Tx.power=Loss in cable(.35db)+splice loss(.1db)

Spliter loss+min.power reqd.at receiver.

For Calculating The HOP Length (in kms)

Tx power(dbm)- Rx sensivity(dbm)/0.35

Cable length in kms=6db(totalloss)/0.35=17.14kms.

For BSNL Internal Circulation only

APPLICATION

1.Non Dispersion Shifted Fibre :

a) TDM :1310 nm

b)DWDM :1550 nm. supports 10gbs up to 300 mtrs.

2.Dispersion shifted fibres suitable for TDM but not

for DWDM.

3.Non Zero DSF :for TDM & DWDM 1550 nm.

4.Newer generation fibre : It allows energy to travel

further in cladding creating small amount of

dispersion to counter four wave mixing .

For BSNL Internal Circulation only

Cable Loss.

Splice Loss.

Connector Loss.

Fibre Length.

Continuity of Fiber.

Fault Localizations/Break Fault.

MAIN TESTS ON OPTICAL FIBRE

CABLES

For BSNL Internal Circulation only

Optical Power Meter.

Calibrated Light Source.

Optical Attenuator.

Optical Time Domain Reflectometer (OTDR).

Optical Talk Set.

INSTRUMENTS REQUIRED

For BSNL Internal Circulation only

Generates Light signals of known power andwavelength (LED or LASER).

Wavelength variations to match Fiber'sWavelength.

CALIBRATED LIGHT SOURCE

For BSNL Internal Circulation only

TYPES:-

Fixed Attenuators.

Variable Attenuators.

APPLICATIONS:-

To Simulate the Regenerator Hop Loss at theFDF.

To Provide Local Loop Back for Testing.

To measure the Bit Error Rate by varying theOptical Signal at the Receiver Input.

RECEIVER SENSITIVITY

OPTICAL ATTENUATORS

For BSNL Internal Circulation only

Used for measuring :

Fiber Loss.

Splice Loss.

Connector Loss.

Fiber Length.

Continuity of Fiber.

Fault Localization.

OPTICAL TIME DOMAIN

REFLECTOMETER (OTDR)

For BSNL Internal Circulation only

Laying of OFC Cable

• HDPE Pipe 75mm appx.5mtr.length

• 18-20ft.

• HDPE Pipe 50mm appx.5mtr.length

18-20ft.

• PLB HDPE Pipe 40 mm appx.1km/200mtr.length

• GI Pipe for PLP 50mm of 6 mtr. In length.

For BSNL Internal Circulation only

Measurements of cable Depth.

i)Cross country route:Above HDPE 1.5mtr/1.65 trench/.9 rocky area.

ii) In built up route (City/Town/Urban)

iii)Existing duct / HDPE /RCC/GI Pipe

iv) Along the Bridge side walls.

v) Along rail bridge or crossing 1.5 mtrs HDP inRCC

vi) Road Crossing 1.5 in RCC along 3 mtrs sideof rd.

For BSNL Internal Circulation only

Route Indicators

1.At every 200 mtr.: Yellow

2.At every Joint : Red.

3. Branch : at route diversions.

For BSNL Internal Circulation only

Conclusion

• OPTICAL FIBER CONCEPT &TYPE

• OFC ROUTE & OPTICAL BUDGET

• IMPORTANT OFC TEST INSTRUMENT

• USE OF OFC in BSNL& LAYING PRACTICE

For BSNL Internal Circulation only