WSS Filter Impairment via Differentiated Channel Modulation
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Solution Overview
Problem
Wavelength selective switches (WSSs) in WDM optical communication systems cause impairment due to non-ideal pass-band filtering, leading to bit errors and degraded network performance, as different channels experience varying attenuation, resulting in unequal bit error rates and concentrated errors in specific channels.
Innovation Solution
Implementing techniques such as comparative channel pre-emphasis, differentiated channel modulation formats, multi-channel forward error correction interleaving, differentiated channel baud rates, and selective subcarrier adjustments to mitigate WSS filter-based impairment, thereby reducing bit error rates and differentials across channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If WSS filter-based transmission is used to route optical signals, then channel routing and wavelength selection are improved, but differential attenuation across channels causes unequal bit error rates and concentrated errors in specific channels
Solution Approach 1:
The patent applies local quality by implementing channel-specific modulation formats tailored to each channel's attenuation characteristics. Channels experiencing higher attenuation use more robust modulation formats (e.g., BPSK), while channels with lower attenuation can use higher-order formats (e.g., QPSK, 16-QAM). This localized adaptation ensures each channel operates at optimal reliability levels despite differential WSS filter effects.
Solution Approach 2:
The patent changes modulation format parameters based on channel conditions. By dynamically selecting modulation formats with different constellation sizes and robustness characteristics for different channels, the system adapts to varying attenuation levels caused by WSS filters, thereby equalizing bit error rates across all channels in the super-channel.
2Productivity
If higher data rates are achieved by combining multiple optical signals into super-channels, then transmission capacity is improved, but differential filter attenuation causes concentrated bit errors in specific channels
Solution Approach 1:
The patent implements local quality by assigning different modulation formats to different channels within the super-channel based on their individual attenuation characteristics. This ensures that each channel contributes reliably to the overall high data rate transmission, preventing concentrated errors that would compromise the super-channel's integrity.
Solution Approach 2:
The patent segments the super-channel into individual channel components, each processed with its own modulation format selection. This segmentation allows independent optimization of each channel's transmission parameters, ensuring that high aggregate data rates are achieved without concentrated errors in any single channel.
3Device complexity
If uniform modulation format is used across all channels in a super-channel, then system complexity is reduced, but differential attenuation by WSS filters results in unequal bit error rates
Solution Approach 1:
The patent applies local quality by implementing channel-specific modulation formats tailored to each channel's attenuation characteristics. Channels experiencing higher attenuation use more robust modulation formats (e.g., BPSK), while channels with lower attenuation can use higher-order formats (e.g., QPSK, 16-QAM). This localized adaptation ensures each channel operates at optimal reliability levels despite differential WSS filter effects.
Solution Approach 2:
The patent introduces dynamic modulation format selection across channels based on real-time or pre-characterized attenuation measurements. The system dynamically assigns appropriate modulation formats to each channel, transforming from a static uniform approach to a dynamic adaptive approach that equalizes bit error rates while maintaining manageable complexity through automated format selection.
Data Source
AI summary
A method may include transmitting, by an optical device, a first set of channels using a first modulation format. The first set of channels may be attenuated during transmission by a filter associated with a wavelength selective switch. The method may further include transmitting, by the optical device, a second set of channels using a second modulation format. The second set of channels may be attenuated during transmission by the filter associated with the wavelength selective switch. The first set of channels and the second set of channels may be included in a super-channel. The first modulation format may be selected based on a first signal quality factor associated with attenuation by the filter associated with the wavelength selective switch. The second modulation format may be selected based on a second signal quality factor associated with attenuation by the filter associated with the wavelength selective switch.