Selective Subcarrier Adjustment for WSS Filter Impairment Mitigation
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Solution Overview
Problem
Wavelength selective switch (WSS) filter-based impairments in WDM optical communication systems lead to bit error rate imbalances across channels, degrading network performance due to non-ideal pass-band filtering, which results in unacceptable information loss and reduced signal quality.
Innovation Solution
Implementing techniques such as comparative channel pre-emphasis, differentiated channel modulation formats, multi-channel forward error correction averaging via interleaving, differentiated channel baud rates, and selective subcarrier adjustments to mitigate bit error rate imbalances and improve signal quality across channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If WSS filter-based routing is used to route optical channels, then channel routing flexibility is improved, but bit error rate imbalance and signal quality degradation occur due to non-ideal pass-band filtering
Solution Approach 1:
The system applies preliminary compensation actions before signal degradation becomes critical. Transmitters adjust channel powers and apply pre-emphasis filtering to counteract the expected WSS filter-induced attenuation patterns, thereby preventing bit error rate imbalance before it occurs during normal operation
Solution Approach 2:
The system dynamically changes transmission parameters including channel powers, modulation formats, and pre-emphasis filter characteristics based on measured bit error rates and WSS filter responses. This allows the system to adapt to different routing configurations while maintaining signal quality
2Adaptability or versatility
If non-ideal pass-band filtering is applied by WSS filters, then wavelength selective routing is achieved, but bit error rate imbalances and information loss increase
Solution Approach 1:
The system implements feedback mechanisms where bit error rates are measured for each channel after WSS filtering, and this information is used to adjust transmitter parameters. The feedback loop continuously optimizes channel powers and pre-emphasis settings to minimize information loss while maintaining wavelength selective routing capabilities
Solution Approach 2:
The system performs preliminary signal conditioning and pre-emphasis filtering at the transmitter before signals enter the WSS. This preliminary action compensates for the anticipated filtering effects, reducing information loss that would otherwise occur during wavelength selective routing
3Reliability
If channel powers are increased to compensate for filter attenuation, then signal quality improves, but power consumption and nonlinear effects increase
Solution Approach 1:
The system applies local quality adjustment by selectively increasing power only for channels that experience high attenuation due to WSS filter characteristics. Instead of uniformly increasing all channel powers, the system tailors power adjustments to specific channels based on their individual bit error rates and filter-induced attenuation patterns, thereby minimizing overall power consumption while maintaining signal quality
Data Source
AI summary
A method may include transmitting, by an optical device, a first channel. The first channel may have a first set of subcarriers. The first channel 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 channel. The second channel may have a second set of subcarriers. The second channel may be attenuated during transmission by the filter associated with the wavelength selective switch. The first channel and the second channel being included in a super-channel. The first set of subcarriers may be selected based on a first signal quality factor associated with attenuation of the first set of subcarriers by the filter. The second set of subcarriers may be selected based on a second signal quality factor associated with attenuation of the second set of subcarriers by the filter.