Efficiency of Installed ADM Capacity Utilisation [%]

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Comparison of Classical and WDM Based Rings Architecture

Laurent. BLAIN, Andre HAMEL, Alain SUTTER France Telecom CNET

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Objectives

• Networking Aspects of Coloured Section Ring Architecture

• New Levels of Optimisation in Network Dimensioning

• Cost Comparison Case Studies to Evaluate Coloured Section Ring Architecture

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SDH Ring Networks

• SDH - networks in the present, networks in the future

• well known advantages (flexible

configuration, good support for management, worldwide standard, etc..)

• SDH self-healing ring architectures are effective solutions for full protected

transmission networks

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Limitations of SDH Rings

• Pure upgradability

• Uniform node architecture can conflict with the different demand loads of nodes

• In most popular two-fibre bi-directional rings the ring link capacity often limits the

utilisation of the ADM capacity

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Coloured Section Rings

• Basic idea

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

– Transit routes realised via the electrical ADMs

• Protection:

– Duplicated optical interfaces in the electrical ADMs – Linear multiplex section protection

• Extra features:

(Coloured Section Ring Architecture is covered by a patent owned by France Telecom)

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Coloured Section Rings (cont.)

• Advantages:

– Increased ring capacity, full electrical ADM capacity for working connections

– Optimal logical order of nodes, minimised transit in nodes

• Drawbacks:

– Extra optical interfaces

– MSP provides incomplete protection (no protection against transit node failures), however mixed

application of MSP and PP can solve the problem – Multiplied number of spare parts (optical interfaces

with transmitters at selected wavelength)

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Coloured Section Rings (cont.)

• Typical applications

– metropolitan area interoffice networks

• Planning:

– planning goal - ring dimensioning

– new levels of optimisation (connection order of nodes, node multiplication in the same ring)

– non-linear sub-problem: optimal node order

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Node Architecture in Coloured

Section Ring

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Routing in Coloured Section

Ring

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Protection in Coloured Section

Ring

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Cost Comparison Case Studies

• Relative cost comparison

– Comparison of two-fibre path protected (PP) and multiplex section shared protected (MSSP) classical SDH rings with Coloured Section rings

• Network cases

– Assumptions for WDM-based rings

» Number of available wavelengths: 8

» Limited distances, no extra amplification (metropolitan area)

– Real network clusters from French and Hungarian

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Cost model

• Only installation cost

• Simplified network cost : only equipment cost (SDH ADMs) considered, fibre and

management costs not included

• Equipment costs of different ADM

configurations (with two or four optical

interfaces, with different tributary capacities, etc.) based on functional equipment models

• Different cost ratios between electrical and optical parts studied

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Analysis of Results

• Classical SDH ring results obtained with help of a planning tool ANOP

– developed by France Telecom CNET

– based on mixed programing and simulated anneling

• CS ring results obtained with help of integrated transmission planning tool PLANET

– developed by Dept. of Telecomm.

– applied in planning activities of Hungarian Telecom Co.

– based on heuristics and graph algorithms

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Analysis of Results (cont.)

• Total cost for SDH ADMs

– if the relative cost of the optical part of the SDH ADM less then 1/2 WDM-based rings are with comparable costs

• Cost gap for OADMs in WDM-based rings

– at least 15-25% of the SDH ADM cost is available for OADMs (OADM built up from passive elements, so 5% of the SDH ADM cost seems to be enough)

• Optimal tributary capacity of SDH ADMs in coloured section rings

– higher tributary capacities (24 or 32 STM1s) optimal for smaller clusters (up to 6 nodes) because of low transit traffic

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Utilisation of ADM Capacities in Different SH Rings

30 40 50 60 70 80 90 100

PP Ring [16]

MSSP Ring [16]

CS Ring [16]

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Network Cost Comparison (Cost option 1:1)

0 2 4 6 8 10 12 14 16 18 20

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

Network Cases

Total ADM Cost

PP Ring [16]

MSSP Ring [16]

CS WDM Ring [16]

Basic SDH ADM relative cost components:

two optical terminations: 0.5, electrical part with 16 STM-1s tributary capacity: 0.5

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Network Cost Comparison (Cost option 1:2)

6 8 10 12 14 16 18 20

Total ADM Cost

PP Ring [16]

MSSP Ring [16]

CS Ring [16]

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Network Cost Comparison (Cost option 1:3)

0 2 4 6 8 10 12 14 16 18 20

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

Network Cases

Total ADM Cost

PP Ring [16]

MSSP Ring [16]

CS WDM Ring [16]

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Network Cost Comparison (Cost option 1:4)

6 8 10 12 14 16 18 20

Total ADM Cost

PP Ring [16]

MSSP Ring [16]

CS WDM Ring [16]

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Cost Gap for OADMs by Node (Cost option 1:1)

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50

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

Network Cases

Cost Gap for One Additional OADM

Trib.: 16 STM-s1 Trib.: 24 STM-s1 Trib.: 32 STM-s1 (Basic SDH ADM relative cost components:

two optical terminations: 0.5, electrical part with 16 STM-1s tributary capacity: 0.5)

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Cost Gap for OADMs by Node (Cost option 1:2)

0.00 0.10 0.20 0.30 0.40 0.50 0.60

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

t Gap for One Additional OADM

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Cost Gap for OADMs by Node (Cost option 1:3)

-0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70

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

Network Cases

Cost Gap for One Additional OADM

Trib.: 16 STM-1s Trib.: 24 STM-1s Trib.: 32 STM-1s (ADM Relative Cost Components: Optical terminations: 0.25, Electrical part: 0.75)

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Cost Gap for OADMs by Node (Cost option 1:4)

0.10 0.20 0.30 0.40 0.50 0.60 0.70

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Cost Gap for OADMs by Node (ADM trib. cap.: 16 STM-1 )

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 0.60

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

Network Cases

Relative Cost Gap for One Additional OADM

Rel. opt. cost: 0.5 Rel. opt. cost: 0.33 Rel. opt. cost: 0.25 Rel. opt. cost: 0.2

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Cost Gap for OADMs by Node (ADM trib. cap.: 24 STM-1 )

0.00 0.20 0.40 0.60 0.80

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Cost Gap for OADMs by Node (ADM trib. cap.: 32 STM-1 )

-0.40 -0.20 0.00 0.20 0.40 0.60 0.80

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

Network Cases

Relative Cost Gap for One Additional OADM

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Optimal Tributary Capacities for Coloured Section Rings

4 6 8 10 12

Total Number of SDH ADMs

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

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Efficiency of ADM Capacity Utilisation in CS WDM Rings Realized with Different ADMs

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 the Utilisation of Installed ADM Capacities [%]

Trib. :16 STM-1s Trib.: 24 STM-1s Trib.: 32 STM-1s (100% = Installed ADM capacity is equal to the theoretical minimum ADM capacity)

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Conclusions

• Coloured Section rings provide best SDH ADM capacity utilisation from the studied architecture

• Competitive cost of Coloured Section rings strongly depends on the cost of optical

interfaces

• If the relative cost of the optical part of the SDH ADM around 1/2 of the cost of Coloured

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Conclusions (cont.)

• Coloured Section rings built up of standard SDH equipment and passive optical

components (except optical amplifiers, if needed)

• protection solutions based on well known

linear multiplex section protection techniques

• Coloured Section ring architecture provide cost effective solutions for self-healing high speed network applications in the near future