Channel Pre-combiner for CDC Optical Add/Drop Scaling
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Solution Overview
Problem
Conventional CDC optical architectures face limitations in scaling and cost per port due to low add/drop channel capacity and high expenses, particularly when using Contentionless Wavelength Selective Switches (CWSS) in ROADM nodes, which restricts the number of channels that can be supported and requires costly node expansions.
Innovation Solution
The implementation of channel pre-combiners in a CWSS-based optical add/drop system, which includes passive and amplified configurations, allows for the pre-combination and splitting of local add/drop ports, enhancing channel capacity and reducing costs by utilizing Contentionless Wavelength Selective Switches (CWSS) and M×N Wavelength Selective Switches to support a colorless, directionless, and contentionless architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CDC architecture with CWSS is used, then operational simplicity and restoration capability are improved, but cost per port and device complexity increase
Solution Approach 1:
The system segments the add/drop functionality by introducing channel pre-combiners that group multiple add ports and drop ports into pre-combined channels. This segmentation allows the CWSS to handle fewer individual port connections while maintaining full CDC functionality, thereby reducing the number of required WSS ports and lowering cost per port.
Solution Approach 2:
Channel pre-combiners are introduced as intermediary devices between the optical modems and the CWSS. These pre-combiners perform the initial channel combination and routing functions, allowing the expensive CWSS component to operate at higher levels of aggregation, thus reducing the total port count required on the CWSS and lowering overall system cost.
2Ease of operation
If CDC architecture with CWSS is used, then operational simplicity is improved, but scaling capability deteriorates due to low add/drop channel capacity
Solution Approach 1:
The system adds a new dimensional layer of channel combination by introducing pre-combiners that aggregate multiple channels before they reach the CWSS. This dimensional change in the architecture allows the system to support significantly higher add/drop capacities (scaling to thousands of channels) without increasing the operational complexity at the node level, as the pre-combiners handle the aggregation automatically.
3Productivity
If node expansion is performed to scale beyond channel limits, then channel capacity is improved, but device complexity and cost increase
Solution Approach 1:
The channel pre-combiners perform preliminary channel aggregation and routing actions before signals reach the main CWSS node. This preliminary action allows the node to scale to higher capacities by simply adding more pre-combiner units rather than expanding the complex CWSS matrix itself, thereby avoiding the need for costly and complex second-layer WSS expansions.
Solution Approach 2:
Multiple pre-combiner units can be merged into a single CWSS node, with each pre-combiner handling a subset of channels. This merging approach allows linear scaling of channel capacity by adding pre-combiners rather than exponentially increasing the complexity of the switching matrix, making high-capacity nodes more cost-effective and simpler to deploy.
Data Source
AI summary
An optical add/drop system supporting a colorless, directionless, and contentionless (CDC) architecture includes a Contentionless Wavelength Selective Switch (CWSS)-based optical add/drop device including N local add/drop ports and M degree ports; and a channel pre-combiner including a common port connected to a first port of the N local add/drop ports and at least two local add/drop ports coupled to the common port. The CWSS-based optical add/drop device can include an M-array of 1×N Wavelength Selective Switches (WSSs) and an N-array of M×1 switches. The channel pre-combiner can be a passive device which passively combines the at least two local add ports and splits the at least two local drop ports. The channel pre-combiner can also include amplifiers on the common port in both an add direction and a drop direction.