Multi-Stage ROADM Architecture for High-Degree Wavelength Routing
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Solution Overview
Problem
Existing reconfigurable optical add-drop multiplexers (ROADMs) face limitations in scalability and add-drop rates, leading to challenges in meeting increasing network capacity demands, and expanding wavelength selective switches (WSS) is costly and degrades switching performance.
Innovation Solution
A multi-stage reconfigurable add-drop multiplexer design comprising multiple stages of optical switching devices, including first, second, third, and fourth stages, with a controller to manage switching states, allowing for high-degree connectivity and flexibility in adding or dropping wavelengths without increasing Polarization Dependent Loss (PDL).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of bi-directional fibers (degrees) of ROADMs is increased to meet network capacity demand, then network capacity is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the ROADM system into multiple stages (first stage with D switching devices, second stage with DN switching devices, third stage with D switching devices, and fourth stage with D combining devices). Each stage handles a portion of the wavelength routing task, allowing the system to achieve high-degree connectivity through compositional architecture rather than requiring a single complex switching element.
Solution Approach 2:
The patent implements a nested structure where multiple stages of optical switching devices are hierarchically organized. The first stage switches distribute wavelengths to second stage switches, which further distribute to third stage switches, which finally combine at the fourth stage. This nested arrangement enables scalable degree expansion by composing simpler switching elements.
2Adaptability or versatility
If wavelength selective switch (WSS) size is increased to provide larger ROADM degrees, then connectivity is improved, but cost increases and switching performance degrades
Solution Approach 1:
Instead of using a single large WSS, the patent segments the switching function across multiple smaller WSS devices arranged in stages. Each WSS handles a subset of the total wavelength routing requirements, allowing the system to achieve high connectivity using multiple smaller, more cost-effective components rather than one large expensive WSS.
Solution Approach 2:
The patent combines multiple smaller WSS devices to achieve the functionality of a larger WSS. By merging the capabilities of several smaller switching devices through multi-stage architecture, the system attains high-degree connectivity while avoiding the prohibitive cost and performance degradation associated with single large WSS implementations.
3Adaptability or versatility
If nodal degree bundling is used to scale up ROADMs with the same WSS size, then degree is increased, but directionless feature is lost and switching performance degrades
Solution Approach 1:
The patent segments the wavelength switching function across multiple stages, with each stage performing a specific portion of the routing task. This segmentation preserves the directionless feature at each stage while achieving high overall connectivity, avoiding the performance degradation associated with degree bundling that forces directional constraints.
Solution Approach 2:
The patent transitions from a single-dimensional switching approach to a multi-dimensional multi-stage architecture. By adding temporal and spatial dimensions through multiple stages, the system achieves high connectivity while maintaining the directionless feature, as each stage can independently route wavelengths without being constrained by fixed directional assignments.
Data Source
AI summary
Reconfigurable optical add-drop multiplexers (ROADMs) includes D optical inputs that receive optical signals, D first optical switching devices, each first optical switching device being associated with one of the D optical inputs, second optical switching devices associated with one of the outputs of a corresponding first optical switching device, each second optical switching device fans-out the optical signal into N multiple signals, third optical switching devices, that combine second output signals received from a corresponding M=D|N of the second optical switching devices, and combining devices that, in use, combine third output signals of N corresponding third optical switching devices and provide a set of D optical outputs of the ROADM and a controller communicably connected to the first, second, third and fth optical switching devices to adjust a switching state thereof.