Simplified ROADM Using Segmented Wavelength Selective Switches
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Solution Overview
Problem
Conventional colorless-directionless reconfigurable optical add/drop multiplexors (ROADMs) are complex and costly due to the requirement for multiple stages of switching and complex two-dimensional arrays of switching elements in M×N wavelength-selective optical switches, leading to high device costs and optical losses.
Innovation Solution
A simplified ROADM design using a modified 1×N wavelength-selective switch with increased input ports, employing micro-electro-mechanical systems (MEMS) or liquid crystal-on-silicon (LCoS) arrays for wavelength-selective switching, allowing independent redirection of wavelength channels without the need for full M×N switching capabilities, thereby reducing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If M×N wavelength-selective switches with multiple stages of switching are used in conventional ROADMs, then wavelength-selective switching capability is achieved, but device complexity and cost increase significantly
Solution Approach 1:
The patent segments the wavelength-selective switching function into two separate components: a wavelength-selective coupler that performs wavelength-dependent coupling, and a simpler N×1 or 1×N switch that performs basic routing. This segmentation eliminates the need for complex M×N switching matrices while achieving the same wavelength-selective routing capability through coordinated operation of the segmented components.
Solution Approach 2:
The patent introduces a wavelength-selective coupler as an intermediary component between the input/output ports and the simple N×1 or 1×N switch. This intermediary performs the complex wavelength-selective function, allowing the main switch to remain simple while achieving overall wavelength-selective switching capability. The coupler acts as a mediator that handles the complexity so the switch itself can be simplified.
2Adaptability or versatility
If M×N wavelength-selective switches with complex two-dimensional arrays of switching elements are used, then full wavelength routing capability is achieved, but device cost increases
Solution Approach 1:
The patent divides the complex M×N switching function into a wavelength-selective coupler (handling wavelength discrimination) and a simple N×1 or 1×N switch (handling routing). This segmentation allows each component to be manufactured with simpler technology, reducing overall device cost while maintaining full wavelength routing capability through their coordinated operation.
Solution Approach 2:
The patent replaces expensive, complex M×N switching matrices with cheaper, simpler N×1 or 1×N switches combined with wavelength-selective couplers. The simpler switch components are more cost-effective to manufacture and implement, achieving the same functional outcome at lower cost.
3Adaptability or versatility
If multiple WSS components are used in ROADMs for redundancy and flexibility, then routing flexibility is improved, but optical losses increase
Solution Approach 1:
The patent extracts the wavelength-selective function from the switching components and places it in dedicated wavelength-selective couplers. This allows the main switches to be simpler N×1 or 1×N types with fewer components, reducing the number of switching elements and thereby reducing cumulative optical losses while maintaining routing flexibility through the couplers' wavelength-selective capabilities.
Solution Approach 2:
The patent uses partial switching capability (N×1 or 1×N instead of full M×N) combined with wavelength-selective couplers to achieve the required routing flexibility. This partial switching approach uses fewer components and switching stages, reducing optical losses while the wavelength-selective couplers provide the necessary flexibility for adding, dropping, and routing wavelength channels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution simplifies the ROADM structure, reduces optical losses, and lowers device costs while maintaining independent wavelength-selective switching capabilities, improving device reliability and flexibility in optical networking.
Implementation Method 1
employing micro-electro-mechanical systems (MEMS) or liquid crystal-on-silicon (LCoS) arrays for wavelength-selective switching
Implementation Method 2
employing micro-electro-mechanical systems (MEMS) or liquid crystal-on-silicon (LCoS) arrays for wavelength-selective switching
Implementation Method 3
a first wavelength-selective coupler for coupling the ingress ports to the array of directors, and the array of directors to the egress ports
Data Source
AI summary
A colorless, directionless ROADM includes a pair of contentioned add and drop wavelength-selective optical switches, an input wavelength-selective optical switch having one input port, and an output wavelength-selective optical switch having one output port. Unintended input-to-output port couplings, which appear in the “contentioned” add and drop switches, can be mitigated by the input and output wavelength-selective optical switches carrying the through traffic.