Compatibility of multivendor dense wavelength division multiplexing system
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Compatibility of multivendor Dense Wavelength Division Multiplexing System. Master Thesis Jan Waldén, Helsinki Supervisor PhD Timo Korhonen. Table of contents. Optical characteristics Optical Signal to Noise Ratio Polarisation Mode Dispersion Chromatic dispersion

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Compatibility of multivendor Dense Wavelength Division Multiplexing System

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Compatibility of multivendor dense wavelength division multiplexing system

Compatibility of multivendorDenseWavelength Division Multiplexing System

Master Thesis

Jan Waldén, Helsinki

Supervisor

PhD Timo Korhonen


Table of contents

Table of contents

  • Opticalcharacteristics

  • OpticalSignal to NoiseRatio

  • PolarisationMode Dispersion

  • Chromatic dispersion

  • Optical Transport Network

  • ModulationMethods

  • ForwardErrorCorrection

  • Testsetup

  • Testresults

  • ITU-T specifications

  • Conclusions


Optical characteristics

Opticalcharacteristics

  • Transport Multiple wavelengths in onefibre.

  • A DWDM system is today mostcommonlyimplemented in the C-band, that is between 1530nm and 1565nm.

  • For example 1552,52nm equals 193,1 THz.

  • Conversion from frequency to wavelengthf=c/. The speed of light in the fibre is approximately two thirds of the speed of light in vacuum.


Optical characteristics1

Opticalcharacteristics

  • Channel spacingaccording to ITU-T G.694.

  • 100 GHz is approximately 0,8nm

  • 50 Ghz is approximately 0,4nm

  • 25 GHz is approximately 0,2nm

  • 12,5 GHz is approximately 0,1nm

  • Commonchannelsspacings in the backbonenetwork are the 100GHz and 50GHz spacing

  • With 50GHz spacing the number of channels in the C-band is between 72 to 88 channelsdepending on the mux/demuxtype.


Compatibility of multivendor dense wavelength division multiplexing system

OSNR

  • When the OSNR is toolow the BER starts to increase.

  • Forward ErrorCorrection (FEC) can be used to improve the BER

  • at low OSNR

  • - Whenplanning the DWDM network OSNR is the limitingfactor

  • Amplifying the signal alsoamplifies the noise

  • 3R regeneration (reamplification, reshaping, retiming)

  • Needed OSNR for modulation and linecodes


Measuring osnr

Measuring OSNR


Compatibility of multivendor dense wavelength division multiplexing system

PMD

  • Twoorthogonal polarisation modes travel at different speed and causespulsebroadening.

  • The refractive index is not constant at any cross sectional area of the fibre

  • The polarisation modes willhave different refractiveindexes and propagate at different velocity


Chromatic dipersion

Chromaticdipersion

  • Broadening of the pulse

  • High frequenciestravels faster thanlowfrequencies

  • Difference in the refractive index ->differentvelocity

  • Intersymbol interference

  • Mitigation of chromatic dispersion

    • Dispersion compensationfibre

    • ChirpedfibreBragggrating

    • Electronic dispersion compensation


Modulation methods and their weaknesses

Modulation methods and theirweaknesses


Compatibility of multivendor dense wavelength division multiplexing system

OTN

Client signal

OPU payload

The

ODU OH

Added

The

OPU OH

Added

The OTU OH Added

with the FEC Over head

OCh

The

OCh OH

Added

OTU

OPU

ODU

In every step the where an overhead is added the the former payload with the overhead

becomes the new payload


End to end circuit

End to endcircuit

OMS

3R

OTS

OTS

3R

Transponder

MUX

Switch

OA

OA

MUX

MUX

Transponder

OCh

OTU/ODU

Transponder

MUX

MUX

OA

OA

MUX

MUX

Transponder

3R

3R


Superfec itu t standard g 975

SuperFEC ITU-T standard G.975


Superfec gain

SuperFECgain


Compatibility of multivendor dense wavelength division multiplexing system

MUX/DEMUX

Vendor D

ATT

1

ATT

4

ATT

2

OA

DCM

DCM

ATT

3

OA

STM64


Vendor c dwdm system

Vendor C DWDM system


Test setup

Test setup


Compatibility of multivendor dense wavelength division multiplexing system

Test with vendor C and B


Vendor b and c optical levels

Vendor B and C opticallevels

Site X

Site Y

VOA 0,04 dB

Rx -10 dBm

Site Z

Rx -4 dBm

OPOUT -1,7 dBm

-18,6 dBm

Tx-13,9 dBm

OA

OA

md

OA

OA

md

Loop

WSS

GMD

OA

OA

OA

OA

-4,4 dBm

Out -9,2 dBm

VOA 1,61 dBm

0 dBm

-18,6 dBm

VOA 1,6 dB

System B

System C


Test results

Test results


G 959

G.959

DWDM interoperability with post-andpre-amplifiers


G 698 1

G.698.1

Metro DWDM withoutamplifiers


Compatibility of multivendor dense wavelength division multiplexing system

Interoperability of DWDM capacity

DWDM End

Terminal

VendorX

DWDM ring

Terminal

VendorX

DWDM end

Terminal

Vendor X

DWDM End Terminal

Vendor Y

According to G.698.1 metro

DWDM applicationshave a

Standard OTU1 and OTU2

G.709 frame with FEC in

order to enable

Interoperability for

Spans withoutlineamplifier

OCh

OCh

G.698.1

OTU1 and OTU2

OTU1 and OTU2

ODU1 and ODU2


Conclusion

Conclusion

  • OSNR toleranceimproved with FEC. The FEC is implemented on everychannel. Compatibilityissue, the same FEC has to be used by the transponders in bothends.

  • Chromatic Dispersion DCF (compensates all channelseasier to use with foreignwavelengths) or eDCO (compensatesonechannel) and reducesattenuation on the linerestricts the use of foreignwavelengths.

  • Tolerances of Modulation methods , compatibilitydepends on whichmethod is chosen by the vendors.


Itu t specifications

ITU-T specifications

  • G.871 Framework for Optical Transport Network Recommendations coordination of the

  • G.872 Architecture of optical networks

  • G.650.2 Definitions and test methods for statistical and nonlinear related attributes of single mode fibre and cable

  • G.652 Characteristics of a single mode fibrecable

  • G.694.1Spectral grids for WDM applications: DWDM frequency grid

  • G.698.1 Multichannel DWDM applications with single-channel Optical interfaces

  • G.709: Interfaces for the Optical Transport Network (OTN)

  • G.798: Characteristics of Optical Transport Network hierarchy equipment functional blocks

  • G.957 Optical interfaces for equipment and systems relating to synchronous digital hierarchy

  • G.959 Optical transport network physical layer interfaces

  • G.975 Forward error correction for high bit-rate DWDM submarine systems


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