Inter-Null Band Multiplexing for Distortion-Tolerant Fiber Optic Transceivers
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Solution Overview
Problem
Fiber optic communication systems experience distortion due to channel nulls, which increase with distance, affecting data transmission reliability, especially at high data rates like 100 Gbps, and existing technologies fail to effectively mitigate this distortion.
Innovation Solution
The implementation of inter-null band multiplexing (INBM) technology, which estimates channel null locations and transmits data within inter-null frequency bands, avoiding distortion by using circuitry that processes and organizes data for transmission between channel nulls, thereby mitigating dispersion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data transmission is performed over long optical fiber links at high data rates, then communication distance and data rate are improved, but fiber dispersion causes channel nulls that distort the optical signal and reduce transmission reliability
Solution Approach 1:
The patent segments the frequency spectrum into multiple sub-carriers and identifies channel nulls within this segmented structure. By dividing the transmission bandwidth and applying inverse fast Fourier transform (IFFT) to generate time-domain signals, the system can selectively avoid null frequencies while maintaining high data rates. This segmentation allows reliable transmission by preventing signal energy from being concentrated at distorted frequency points.
2Productivity
If wavelength division multiplexing is used to increase the number of communication channels, then channel capacity is improved, but fiber dispersion distorts each channel and affects correct data recovery
Solution Approach 1:
The patent transitions from traditional time-domain or simple frequency-domain multiplexing to a two-dimensional approach combining frequency division (multiple sub-carriers) with cyclic prefix time-domain extension. This dimensional transformation allows the system to simultaneously support multiple WDM channels while using the cyclic prefix to compensate for inter-symbol interference caused by fiber dispersion, thereby maintaining data recovery accuracy across multiple channels.
3Device complexity
If direct detect systems are used for optical communication, then system complexity is reduced, but channel nulls in the power spectral density cause substantial energy loss and signal distortion
Solution Approach 1:
The patent applies preliminary action by inserting a cyclic prefix before the main data signal in the time domain. This cyclic prefix is generated in advance based on the channel characteristics and serves as a guard interval that prevents inter-symbol interference from channel nulls. By preparing this protective structure beforehand, the system maintains signal energy integrity without requiring complex real-time compensation mechanisms, thus keeping device complexity low while reducing energy loss.
Data Source
AI summary
According to one embodiment of the invention, fiber optic communications method is described. The method comprises a first operation of dynamically identifying frequencies at which spectral nulls occur in a signal received via an optical fiber, and thereafter, segregating communications over the optical fiber into a set of inter-null bands defined by the spectral nulls.