Availability Analysis and
Comparison of Different Optical Architectures
Tivadar Jakab - Budapest University of Technology and Economics
Dávid Arató - Hungarian Telecommunications Co.
Endre Kállay - Budapest University of Technology and Economics
2nd International Workshop on the
Design of Reliable Communication Networks Munich, Germany,10 April 2000
Motivations
¨ Extensive preparations to introduce and develop an optical network layer
¨ Transparent optical network architectures are applied to meet different client layer demands
¨ Network flexibility is preferred to cope with the changing and uncertain planning conditions
¨ Optical network layer introduces extra complexity into the transport networks, the impact of this extra
complexity on the availability performance of the network should be analysed
Outline
¨ Optical network architectures under study
¨ Study cases
¨ Modeling and analysis methodology
¨ Analysis of results
¨ Summary and conclusions
Optical Network Architectures under Study
• Single architectures
•Optical Channel Dedicated Protected Ring (OCDP)
•Optical Multiplex Section Shared Protected Ring (OMSSP)
•Multi-Wavelength Transport Network (MWTN)
• Interconnected architectures
•OCDP-MWTN (dual homing with 1+1 OCh protection)
•OMSSP-OMSSP (Dual homing with D&C)
Study Cases
• Basic studies cases
• 6-node rings
• 10-node mesh
• 10 km spans without line amplification
• Fixed OADM structure
• Special studies cases
• 100 km spans with line amplification
•Flexible OADM structure
Fixed OADM structure
Demux
modul Mux
modul
Input Output
Dropped channels
Added channels
1 1
1 1
2 2
2
2 K K
Flexible OADM structure
1 2 K DEMUX MUX 1 2 K
Switch
Input Switch Output
Switch 2x2
2x2
2x2
Modeling and Analysis Methodology
¨ Bi-state network elements are assigned to each basic functionality (e.g. optical multiplexing, demultiplexing, splitting, switching, etc.)
¨ Elements are characterised with – Main Failure Rate
– Mean Time To Repair
¨ Path level description of the network
¨ Down Time Ratio analysis of the routed optical channels
¨ State space in reduced for the significant states (however, the eliminated states are with very low
DTR of an optican channel routed on different single architectures
5.00E-06 1.00E-05 1.50E-05 2.00E-05 2.50E-05
D T R
basic flex. OADM line ampl.
flex. OADM+line ampl.
Analysis of results
¨ Basic cases
– OCDP with shorter protection paths then OMSSP and simpler node structure then MWTN has better availability performance
¨ Flexible OADM cases
– Extra switches do not have significant impact on the DTR of the routed optical channels
¨ Cases with longer spans and line amplification
– Longer routes and line amplification increase the DTR significantly
DTR of an optican channel routed on different interconnected architectures
5.00E-06 1.00E-05 1.50E-05 2.00E-05 2.50E-05 3.00E-05 3.50E-05
DTR
OCDP-MWTN OMSSP-OMSSP
Analysis of results (2/1)
¨ OCDP-MWTN
– in the basic case the complex node structure of MWTN dominates the interconnected architecture from availability point of view
– extra swithes in flexible OADM do not have significant impact
– longer routes and line amplification results a significantly increased DTR
Analysis of results 2/2
¨ OMSSP-OMSSP
– the drop and continue functionality implemented in the optical domain increrases the DTR, however
with this increased complexity and longer
protection routes optical channels can be routed with better availability on the interconnected
OMSSP rings then on OCDP-MWTN
¨ optical channels routed on the interconnected
architectures are with the same order of DTRs than that for the single architectures
Summary and Conclusions
¨ Availability analysis of optical channels routed on single and interconnected transparent optical
architectures have been presented
¨ Due to the high reliability of the passive optical
elements the optical architectures realizing complex routing and protection functionalities are with good avaialbility performances
¨ Extra switches in felxible OADM do not have significant impact on the DTR of routed optical channels
¨ Based on the studied architectures and cases the
general contribution of the optical server layer to the
