Multi-Band ROADM Routing to Preserve OSNR in WDM Links
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Solution Overview
Problem
In WDM transmission systems using multiple wavelength bands, the optical signal-to-noise ratio (OSNR) is degraded due to noise generated in wavelength converters, leading to communication quality deterioration as the signal passes through multiple nodes.
Innovation Solution
An optical communication device with a configuration that includes wavelength filters, selective switches, and wavelength converters to process signals in different wavelength bands, while avoiding noise accumulation by routing through signals without converters when possible, thus expanding the bandwidth without increasing the bandwidth of wavelength selective switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wavelength converters are used in ROADMs to enable multi-band WDM transmission, then the system can transmit optical signals using multiple wavelength bands (S-band and C-band), but the optical signal-to-noise ratio (OSNR) is degraded due to noise generated in the wavelength converter
Solution Approach 1:
The patent segments the WDM signal processing into separate paths: a first path for through signals that bypasses the wavelength converter, and a second path for add/drop signals that uses the wavelength converter. This segmentation allows through signals to avoid noise degradation while maintaining multi-band transmission capability for signals that require conversion.
Solution Approach 2:
The patent introduces a wavelength selective switch as an intermediary component that can selectively route signals through different paths. This intermediary enables the system to choose whether to use the wavelength converter based on the signal type, thereby protecting through signals from noise while still enabling wavelength conversion when needed for add/drop operations.
2Quantity of substance
If wavelength converters are deployed at multiple ROADMs to expand bandwidth, then the system can handle more wavelength channels, but the noise degradation accumulates as the signal passes through multiple nodes
Solution Approach 1:
The patent creates distinct signal paths within each ROADM: through signals are routed through a converter-bypass path while add/drop signals use the wavelength conversion path. This segmentation ensures that at each node, through signals avoid noise accumulation, and the effect compounds positively across multiple nodes in the transmission chain.
Solution Approach 2:
The patent applies different processing qualities to different signal types: through signals receive noise-free transmission by bypassing the converter, while add/drop signals undergo wavelength conversion when necessary. This local quality differentiation optimizes the overall system performance by protecting the majority of through signals from noise while enabling wavelength flexibility where needed.
3Device complexity
If a single wavelength selective switch is used to process all wavelength bands, then the device complexity is reduced, but the switch must handle the entire extended bandwidth which increases its complexity
Solution Approach 1:
The patent segments the wavelength selective switching function into multiple specialized switches: one switch handles the C-band, another handles the S-band, and they operate independently. This segmentation allows each switch to be optimized for a specific bandwidth range, reducing individual switch complexity while collectively handling the extended multi-band spectrum.
Solution Approach 2:
The patent adds a dimensional separation by processing different wavelength bands through separate switch instances rather than forcing a single switch to handle all bands. This dimensional approach to bandwidth management allows the system to scale to multiple bands without proportionally increasing the complexity of individual switching components.
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 suppresses noise addition to through signals, maintaining or improving OSNR, allowing for higher-quality communication over a greater number of transmission spans.
Implementation Method 1
a wavelength filter configured to extract a first WDM signal allocated in a first wavelength band and a second WDM signal allocated in a second wavelength band different from the first wavelength band from a reception WDM signal
Implementation Method 2
a wavelength converter configured to convert wavelengths from the second wavelength band to a third wavelength band
Data Source
AI summary
An optical communication device processes a WDM signal in a WDM transmission system that uses a first wavelength band and a second wavelength band. A wavelength filter extracts a first WDM signal allocated in the first wavelength band and a second WDM signal allocated in the second wavelength band from a WDM signal received from first node. An optical signal branched from the first WDM signal is guided to an access network and a remaining optical signal that is not branched from the first WDM signal is guided to second node. An optical signal branched from the second WDM signal is guided to the access network via a wavelength converter and a remaining optical signal that is not branched from the second WDM signal is guided to the second node. The wavelength converter converts wavelengths from the second wavelength band to a third wave length band.