The elusive next-gen ROADM

Reconfigurable add/drop multiplexer (ROADM) technology continues to evolve. Though existing components were deemed sufficient for deployment in optical networks, system vendors and carriers requested colorless and directionless capability for added flexibility in responding to future changes in traffic patterns. Now, just as the required optical components are coming to market, carriers have added contentionless to the wish list. Looking even further ahead, discussions on gridless functionality to maximize fiber capacity have recently begun.



Report Highlights

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Executive summary
In a nutshell
Ovum view
Dynamic network will continue to add more functionality
Industry slowed by difficult decisions
ROADM generations
Roadmap focuses on add/drop functionality
Industry undecided over next step
Progress in larger WSS for Phase 3 or 4
Recent emergence of gridless requirement
Application description
Network port block will stay WSS but add gridless requirement
Partitioning by network direction created constraints
Multiple channel bank options for adding functionality
Adding colorless feature
What is contentionless?
Complex design trade-offs still under study
The contentionless requirement is under contention
Reliability concerns favor smaller components
Separate small and large node requirements
Changing channel counts
Multiple technologies still in the running
WSS is incumbent
Tunable filters for smaller ROADMS
PLC very interesting to address splitting and routing complexity as well





List of Figures
Figure 1: ROADM block diagram showing separation of network port functions and channel bank function
Figure 2: Current network port implementation using WSS
Figure 3: ROADM block diagram of Phase 1 ROADM without directionless capability showing stranded resource for desired local drop
Figure 4: Colored channel bank as in Phases 1 and 2
Figure 5: AWG/LMOS and WSS alternative implementations of colorless channel bank
Figure 6: Illustrative examples of directionless with and without contention


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