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					         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 waves
   with a minimum attenuation.
2. Optical fibers are composed of fine threads of
   glass in layers. The fine threads are of silica
   glass mix with some dopant material.
3. Two main layers are known as core (central, of
   8 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 it
   at the speed of 2/3 of speed of light in vacuum
   observing the total internal reflection principle.


                  For BSNL Internal Circulation only
  The Optical Fibre structure




8-50 m
          Core                                            125 m




                                                      Cladding




                 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
      1
                                                      n1 = 1.48
                                                      n2 = 1.46

 INCIDENT RAY 1
      2                                                                     Reflected Ray
                                                                                     3
          3
N1 core                                   ¢i
                                                                                         2

 N2 cladding
                                                 ¢r
                                                                  Refrected Ray
                                                                        1

               (Principal of total internal reflection)
                             For BSNL Internal Circulation only
    Jacket                                                    Jacket

                                                              Cladding
                                                                    Core




     Cladding (n2)                                                Cladding

Core (n2)                                                          Jacket
                     Light at less than Angle of Angle of
                     critical angle is
                                        incidence reflection
                     absorbed in jacket
                                        Light is propagated by
                                        total internal reflection

                       Fig. Total Internal Reflection in an optical Fibre
                         For BSNL Internal Circulation only
CLASSIFICATION OF OPTICAL FIBRE

  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.

                   For BSNL Internal Circulation only
SINGLE MODE FIBER DESIGNS:-


 .NON DISPERSION SHIFTED FIBRE-NDSF-G652

 . DISPERSION SHIFTED FIBRE-
 DSF-G653

 .NON ZERO DISPERSION SHIFTED FIBRE-
 NZDSF-G655



              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
Loss    FIRST               Attenuation Curve
dB      WINDOW




3.0
                                 SECOND WINDOW
2.5

2.0

1.5                                                               THIRD WINDOW

1.0                 RAYLEIGH
                   SCATTERING
0.5

0
       800   900     1000     1100       1200        1300        1400   1500   1600   1700
                    Wave Length (Lemda) in nm

                            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      distance
Transmission(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 this
 Region

 Mostly used for WDM & DWDM applications



              For BSNL Internal Circulation only
FURTHER CLASSIFIED BAND
  SECON & THIRD WINDOWS FURTHER CLASSIFIED
  IN FOLLOWING BAND OF SPECTRUM

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(total
    loss)/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
MAIN TESTS ON OPTICAL FIBRE
          CABLES


     Cable Loss.
     Splice Loss.
     Connector Loss.
     Fibre Length.
     Continuity of Fiber.
     Fault Localizations/Break Fault.




            For BSNL Internal Circulation only
INSTRUMENTS REQUIRED


Optical Power Meter.
Calibrated Light Source.
Optical Attenuator.
Optical Time Domain Reflectometer (OTDR).
Optical Talk Set.




            For BSNL Internal Circulation only
CALIBRATED LIGHT SOURCE



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

 Wavelength variations to match Fiber's
 Wavelength.




              For BSNL Internal Circulation only
    OPTICAL ATTENUATORS
TYPES:-
Fixed Attenuators.
Variable Attenuators.

APPLICATIONS:-
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.
RECEIVER SENSITIVITY
              For BSNL Internal Circulation only
    OPTICAL TIME DOMAIN
   REFLECTOMETER (OTDR)

Used for measuring :
 Fiber Loss.
 Splice Loss.
 Connector Loss.
 Fiber Length.
 Continuity of Fiber.
 Fault Localization.




              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 in
  RCC
vi) Road Crossing 1.5 in RCC along 3 mtrs side
  of 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
For BSNL Internal Circulation only

				
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