Optical Sub-band Frequency Diversity for IM/DD Transmission
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Solution Overview
Problem
Optical access networks face challenges in providing high-speed, wide-coverage connectivity due to signal degradation with increasing transmission speed and distance, especially with intensity-modulation and direct-detection (IM/DD) formats, which suffer from poor transmission performance compared to coherent-detection formats.
Innovation Solution
The method involves partitioning optical signals into frequency sub-bands, generating signal frequency mappings, and using frequency diversity transmission by creating redundant correlated signals with spectrally-inverted sub-bands for digital coherent superposition, which helps equalize the signal-to-noise ratio across the frequency range and increase transmission distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If intensity-modulation and direct-detection (IM/DD) formats are used to reduce transceiver cost, then cost is reduced, but transmission performance deteriorates
Solution Approach 1:
The optical signal spectrum is divided into multiple frequency sub-bands, and frequency diversity is applied independently to each sub-band. This segmentation allows the system to mitigate frequency-selective fading and signal degradation in each sub-band, thereby improving overall transmission performance while maintaining the cost advantage of IM/DD formats.
Solution Approach 2:
The patent applies frequency diversity transmission by changing the frequency parameters of the signal across multiple sub-bands. By transmitting redundant copies of the signal at different frequency locations and using frequency mapping to rearrange sub-bands, the system exploits frequency diversity to improve signal quality and transmission performance without requiring coherent detection.
2Productivity
If optical transmission speed and transmission distance are increased to provide high-speed wide-coverage connectivity, then connectivity capability is improved, but signal degradation becomes more severe
Solution Approach 1:
The signal is partitioned into multiple frequency sub-bands, allowing independent optimization and diversity transmission for each sub-band. This segmentation enables the system to overcome signal degradation over long distances by transmitting redundant signal copies across different frequency sub-bands, improving overall signal quality and enabling high-speed wide-coverage connectivity.
Solution Approach 2:
The patent introduces redundant copies of the signal at different frequency locations before transmission. These redundant copies serve as a cushion against signal degradation by providing alternative signal paths that can compensate for fading and attenuation in the primary transmission path, thereby maintaining signal quality over extended distances.
3Reliability
If frequency diversity transmission with redundant correlated signals is applied to improve transmission performance, then bit error rate and signal-to-noise ratio are improved, but device complexity increases
Solution Approach 1:
The frequency diversity transmission is applied independently to each frequency sub-band, which segments the complex signal processing task into smaller, more manageable units. This segmentation reduces the computational complexity required for each sub-band while maintaining the overall performance benefits of frequency diversity across the entire signal spectrum.
Solution Approach 2:
The patent uses frequency mapping to rearrange frequency sub-bands, which simplifies the signal processing by transforming complex frequency-domain operations into simpler parameter transformations. This approach reduces the computational burden compared to traditional frequency diversity methods while achieving similar or improved transmission performance.
Data Source
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AI summary
An optical data transmission method comprising partitioning an optical signal into a plurality of frequency sub-bands, generating a signal frequency mapping that rearranges the plurality of frequency sub-bands, choosing a plurality of frequency components based on the signal frequency mapping to form a set of frequency components, and transmitting the set of frequency components using frequency diversity transmission. An optical data receiving method comprising obtaining a signal frequency mapping for an original signal, receiving an optical signal that comprises a plurality of frequency sub-bands, re-arranging the plurality of frequency sub-bands using the signal frequency mapping to generate a restored original signal, and processing the restored original signal to recover an original data sequence. The signal frequency mapping can be based on digital coherent superposition techniques, and space-time codes such as a silver code can be also used for the generation of new sub-carriers.