Coherent Augmented Optical Add-Drop Multiplexer Design
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Solution Overview
Problem
Conventional Optical Add-Drop Multiplexers face limitations due to the limited number of ports in Wavelength-Selective Switch (WSS) components, leading to high costs and reduced system performance, particularly in supporting a high number of channels and mesh connectivity, with increased loss and complexity in power splitters and combiners, and high complexity and cost in coherent receivers.
Innovation Solution
A coherent augmented Optical Add-Drop Multiplexer design utilizing a moderate port count WSS and multiple coherent receivers with lower Common Mode Rejection Ratio (CMRR) to efficiently route and process multiple wavelength channels, reducing the number of channels each receiver must reject and lowering the cost of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of ports in WSS components is increased to support more channels and mesh connectivity, then the channel capacity and mesh connectivity are improved, but the cost of the WSS component increases
Solution Approach 1:
The invention divides the WSS component into multiple smaller WSS modules, each handling a subset of channels. Instead of using one large WSS with many ports, multiple smaller WSS units with fewer ports each are employed, reducing the cost of individual components while collectively providing the required channel capacity.
Solution Approach 2:
Multiple smaller WSS modules are combined and coordinated to work together as a unified system. The modules are merged through optical switching fabric and control logic to provide the aggregate channel capacity and mesh connectivity that would otherwise require a single large WSS.
2Adaptability or versatility
If the number of ports in WSS components is increased to support more channels and mesh connectivity, then the mesh connectivity is improved, but the degree of branching capability is reduced
Solution Approach 1:
The branching functionality is segmented across multiple WSS modules, where each module handles a portion of the branching requirements. This allows the system to achieve high degree of branching (4-8 degree) by distributing the branching logic across multiple simpler modules rather than requiring a single complex WSS.
Solution Approach 2:
An optical switching fabric and control system act as intermediaries between multiple WSS modules, coordinating their operation to provide unified mesh connectivity and branching capabilities. The intermediary layer manages the complexity of coordinating multiple modules to achieve the desired mesh network functionality.
3Ease of operation
If conventional power splitters and combiners are used to route multiple channels, then the channel routing is achieved, but the system loss and complexity increase
Solution Approach 1:
The invention extracts the wavelength-selective switching functionality from conventional power splitters and combiners, replacing them with WSS modules that can selectively route specific wavelength channels. This eliminates the need for bulky 1:x power splitters that divide power across all channels, thereby reducing insertion loss while maintaining channel routing capability.
Solution Approach 2:
Conventional mechanical or passive power splitting mechanisms are replaced with optically-controlled WSS modules that use tunable filters and optical switches. This substitution enables dynamic, selective channel routing with lower loss compared to fixed power splitters that must divide power across all possible channels.
4Measurement precision
If coherent receivers with high CMRR are used to receive selected channels, then the channel selection precision is improved, but the receiver complexity and cost increase
Solution Approach 1:
The channel selection function is extracted from the coherent receiver and performed upstream by the WSS module. The WSS pre-selects and routes only the desired wavelength channel to each receiver, so the receiver itself does not need high CMRR to reject other channels. This reduces receiver complexity while maintaining precise channel selection.
Solution Approach 2:
Channel selection is performed in advance by the WSS module before the signal reaches the coherent receiver. The WSS acts as a preliminary filter that isolates the desired channel, so the receiver only needs to process a single channel rather than selecting among multiple channels, thereby reducing the required CMRR and overall receiver complexity.
Data Source
AI summary
In an Optical Add-Drop Multiplexer, a drop section comprises a Wavelength Selective Switch (WSS) having at least one drop-port, the WSS being operative to couple a respective set of w (where w>1) wavelength channels from a received Wavelength Division Multiplexed (WDM) signal to each drop port. A respective 1:s power splitter is associated with each drop port. Each power splitter supplies the respective set of channels received from its drop port to each one of a corresponding set of coherent receivers. Each coherent receiver operates to receive a selected one of the respective set of channels.