Fractional Delay Filter Decouples Equalizer Complexity
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Solution Overview
Problem
Current fractionally spaced equalizers (FSEs) in optical communication systems are complex, power-hungry, and costly, limiting the increase in bandwidth and throughput due to their design constraints, particularly in meeting the demands of next-generation optical communication systems requiring multi-terabit per second capacities.
Innovation Solution
The implementation of a non-integer, sub-symbol sampling FSE system that decouples channel equalization functions from fractional delay functions, using a fractional delay filter (FDF) and a single adaptive fractionally spaced equalizer (AFSE) to align received samples with transmitted symbols, reducing power consumption and design complexity by operating at a lower sampling rate and employing a single AFSE per output signal from an analog-to-digital converter (ADC).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current fractionally spaced equalizers (FSEs) are used to correct sampling phase errors and minimize noise enhancement, then robustness against sampling phase errors is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent segments the equalization process into two independent parts: a fractional delay filter that handles sampling phase alignment, and a simplified integer-spaced equalizer that handles noise enhancement. This segmentation allows each component to be optimized independently, reducing overall complexity while maintaining robustness.
Solution Approach 2:
The patent introduces a fractional delay filter as an intermediary component between the ADC and the equalizer. This intermediary handles the sampling phase correction function, allowing the main equalizer to focus solely on noise enhancement mitigation, thereby reducing its complexity.
2Reliability
If oversampling is used to enable fractionally spaced equalization, then tolerance against sampling phase errors is improved, but sampling rate requirements and power consumption increase
Solution Approach 1:
The patent separates the sampling phase correction function (handled by fractional delay filter) from the equalization function (handled by integer-spaced equalizer). This allows the system to achieve phase error tolerance without requiring high oversampling rates, thereby reducing power consumption.
Solution Approach 2:
The patent changes the sampling rate parameter from high oversampling rates to lower rates that still satisfy the Nyquist criterion. By combining this parameter change with the fractional delay filter, the system maintains phase error tolerance while reducing power consumption.
3Reliability
If fractionally spaced equalizers are used to minimize noise enhancement from spectral nulls, then signal quality is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the equalization task into two separate components: fractional delay filtering for phase alignment and integer-spaced equalization for noise enhancement minimization. This segmentation allows the use of simpler integer-spaced equalizer structure while achieving the same noise enhancement minimization效果.
Solution Approach 2:
The fractional delay filter acts as an intermediary that pre-aligns the signal phases before the integer-spaced equalizer processes the signal. This intermediary function enables the use of simpler equalizer structure while maintaining the ability to minimize noise enhancement from spectral nulls.
4Productivity
If higher sampling rates are used to increase bandwidth and throughput capacity, then capacity is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent changes the sampling rate parameter from high oversampling rates to lower rates that still satisfy the Nyquist criterion. This parameter change reduces device complexity and power consumption while maintaining the ability to achieve high bandwidth and throughput capacity through efficient signal processing.
Data Source
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AI summary
An apparatus comprising a memory and a processor coupled to the memory, wherein the memory includes instructions that when executed by the processor cause the apparatus to perform the following: receive an incoming signal at a sampling rate that is greater than a symbol rate associated with the incoming signal, replicate a plurality of data streams from the incoming signal, apply a plurality of fractional delays to the plurality of data streams correspondingly, generate data blocks from each of the fractionally delayed data streams, and perform an adaptive equalization on each of the data blocks sequentially, wherein the fractional delay is applied to the data streams independently of the adaptive equalization, and wherein the adaptive equalization implements taps spaced at a fraction of a symbol interval associated with the incoming signal.