Efficiency of Installed ADM Capacity Utilisation [%]

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Strategic consideration on the introduction of WDM network

layer

Tivadar Jakab

Department of Telecommunications Budapest University of Technology

and Economics

FER, ZAGREB, June 2000

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Outline

• Motivation

• WDM architectures

• Driving forces to introduce WDM technology

• Introduction scenios

• WDM network planning

• SDH-WDM similarities and analogies

• New planning problems, an example

• Summary, conclusions

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Motivation

• liberalized telecom market, sharp competition

• Internet revolution, increasing capacity demands

• huge bandwith potential of the optical infrastructure

• transparent transport service for the different clients

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WDM functionalities

• transport network technology

• similar functionalities as in SDH:

– amplification, 3R (?), routing (wavelength), terminal and add-drop multiuplexing, cross- connection,

• architectures with routing and protection

functionalities realised partly or fully in the optical domain

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Basic node functionalities

a.) m ultip le xing b .) add -d ro p c.) cro ss-co nnec tin g

OMS_4 OMS_4

OMS_4 OMS_1 OCH

a.) add-drop with cross-connecting b.) cross-connect

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WDM architectures

Architecture Routing Protection Key equipments

Electrical Optical

CS Ring optical + electrical

electrical linear multiplex section protection (MSP) can be improved with logical node reordering

ADM OADM

OMSSP Ring optical (+ electrical)

opticalmultiplex section shared protection (MSSP)

ADM or DXC (SDH client)

OADM and optical switches

MWTN Mesh optical (+electrical)

OXCbased restoration (optical) DXC (SDH client)

OXC

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Coloured Section Rings

• SDH-WDM hybrid

• Basic idea

– SDH-transparent ring architecture – Different wavelength to each ring link

– Transit routes realized via the electrical ADMs

• Protection:

– Duplicated optical interfaces on the both sides of the electrical ADMs

– Linear multiplex section protection

• Extra features:

– Logical ring structure can be different from the physical one – Multiplied insertion of nodes into the same ring

– Capacity for protection separated in wavelength

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CS ring node structure

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CS ring protection

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CS ring routing

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1+1 Path Protection in

Coloured Section Ring

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Node Reordering (1)

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Node Reordering (2)

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Summary and Conclusions on the CS ring Protection Solutions

• With proper node reordering the protection ability of Colored Section ring can be improved

– the availability performance for this solution is practically the same as for extra 1+1 path protection

– the node reordering seems to be better from capacity utilization point of view.

• Application of 1+1 path protection has significant

advantages from operational point of view comparing with MSSP over Colored Section ring solution.

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Optical Multiplex Section Shared Protected Ring

• Transparent optical architecture

• Wavelength routing

• MSSP protection scheme realized in the optical domain

• Logical mesh, easy to upgrade the SDH client (point to point)

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Optical Multiplex Section Shared Protected Ring

A B

D C

A B

D C

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Multi-Wavelength Transport Network

• Transparent opticl architecture

• OXC based node structure

• Restoration in the optical layer (or protection)

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Multi-Wavelength Transport Network

OXCs TUNABLE FILTERS

DXC

TUNABLE Tx TUNABLE Rx

ADD DROP

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Driving forces to introduce WDM technology

• introduction: not a replacement but additional layer

• gradual introduction is possible (more and more functionalities)

• lack of optical fibre capacity

• improvement of SDH capacity utilization

• OA&M advantages, new services

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Introduction scenario 1

• in case of lack of optical fibre capacity

• only SDH client, no rearrangement in the SDH layer

• point to point WDM systems

• no problems with technological limitations (transparent networking)

• no complex networking solutions (maximum liner OMSP protection)

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Introduction scenario 2

• in case of improvement of SDH capacity utilization

• only SDH client, rearrengements in the SDH layer

• WDM networking, routing, protection

• WDM islands interconnected in SDH layer

• transparent (e.g. MWTN) and non- transparent solutions e.g. CS ring

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Utilisation of ADM Capacities in Different SH Rings

0 10 20 30 40 50 60 70 80 90 100

1 2 3 4 5 6 7 8 9 10 11 12

Network Cases

Efficiency of Installed ADM Capacity Utilisation [%]

PP Ring [16]

MSSP Ring [16]

CS Ring [16]

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Optimal Tributary Capacities for Coloured Section Rings

0 2 4 6 8 10 12

1 2 3 4 5 6 7 8 9 10 11 12

Network Cases

Total Number of SDH ADMs

Trib.: 16 STM-1s Trib.: 24 STM-1s Trib.: 32 STM-1s

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Introduction scenario 3

• in case of OA&M advantages, new services

• transparent wavelength based services

• new clients (ATM, IP)

• complex WDM networking

• WDM island and overlay network

• only transparent architectures (MWTN, OMSSP)

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Installation Cost Breakdown for MWTN

electrical / optical / infrastructure breakdown of MWTN architecture

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

5 nn_n 5 nn_h 5 h_n 5 h_h 5 u_n 5 u_h 8 nn_n 8 nn_h 8 h_n 8 h_h 8 u_n 8 u_h

infr.

opt. int.

elect.eq.

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Overall Installation Costs for MWTN and SDH meshes

Investment cost in MECU for a 5 node mesh with a uniform traffic demand

0 2 4 6 8 10 12 14 16

Investment cost (MECU)

Infrastructure Optical equipment

Electrical equipment

SDH MWTN

normal traffic demand

SDH MWTN

5 times normal traffic demand FER, ZAGREB, June 2000

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Relative Overall Installation Cost Savings for Optical Rings

in Comparison with SDH MSSP Ring

-20.00%

-10.00%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

N5_NN_N N5_HU_N N5_UN_N N8_NN_N N8_HU_N N8_UN_N N5_NN_H N5_HU_H N5_UN_H N8_NN_H N8_HU_H N8_UN_H

CSR OMS-SP

Normal Traffic High Traffoc (5 x normal)

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WDM network planning

• analogies and similarities with SDH network planning

• key issue to reuse the existing planning methodology and expertise

• new problem wavelength allocation

• modified problem stand-by network planning

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SDH-WDM similarities and analogies

entity SDH WDM

demand VC-4 OCH connection

cross-connection (DXC) cross-connection (OXC) add-drop (ADM) add-drop (OADM) functionality (equipment)

regeneration (reg.) regeneration (O/E/O, 3R) DXC-based mesh OXC-based mesh

SNCP-DPRing OCH-DPRing

architectures

MS-SPRing OMS-SPRing

linear SNCP (1+1, 1:1) linear OCHP(1+1, 1:1)

SNCP-DPRing OCH-DPRing

protection

MS-SPRing OMS-SPRing

multiplexing n VC-4s on a STM-n MS w OCH connections on a w- wavelength OMS allocation STM-n MS to a fibre OMS to a fibre

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Planning problems

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• routing: wavelength routing, transparent wavelength routes

• grooming: optical channels to fibre, ne problem wavelength assignment

• stand-by network dimensioning: in case on no wavelength conversion a multiplied

problem

• system dimensioning: not so complex than the SDH

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WDM stand-by network planning

• restoration on optical channel level

• full cross-connectivity in case of wavelength conversion

• different const structure in compariosn with SDH (transmission/switching)

• different model and method is needed

• SDH methodology (LP) can be extended

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Wavelength layers in WDM

stand-by

network

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Introduction of wavelength conversion into the model

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A new model for WDM stand-by network planning

G G'

Flexibility point Topological point

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Summary, conclusions

• Both economical and operational

advanteges can be gained introducing a WDM network layer

• The actual situation of a PNO may imply differet driving forces

• Since the introduction is not a replacement, it can be performed gradually

• Strategic network planing is a key issue in the introductuction phase

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