Coherent Receiver Phase Feedback for Group Delay Ripple Compensation
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Solution Overview
Problem
Existing optical fiber communication systems face challenges in achieving high spectral efficiency due to distortion from factors like group delay ripple and dispersion slope, which require long tap lengths in adaptive equalization filters, limiting accurate distortion compensation.
Innovation Solution
A compensation amount calculation apparatus and method that adaptively controls filter coefficients to compensate for group delay ripple by feeding back a phase response to filters before the adaptive equalization filter, reducing the tap length required for accurate distortion compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the tap length of the adaptive equalization filter is increased to compensate for group delay ripple and dispersion slope, then the distortion compensation accuracy is improved, but the circuit size and power consumption increase
Solution Approach 1:
The patent divides the distortion compensation function into two separate modules: a dispersion compensation filter that handles chromatic dispersion, and an adaptive equalization filter that handles polarization mode dispersion and other distortions. By segmenting the compensation tasks, each filter can use a shorter tap length while achieving overall high compensation accuracy, thus reducing circuit size and power consumption.
Solution Approach 2:
The patent introduces a dispersion compensation filter as an intermediary component between the optical signal source and the adaptive equalization filter. This intermediary filter pre-compensates for chromatic dispersion, allowing the adaptive equalization filter to focus on other distortion types with reduced tap length requirements, thereby reducing overall system complexity.
2Measurement precision
If the tap length of the adaptive equalization filter is increased to compensate for group delay ripple and dispersion slope, then the distortion compensation accuracy is improved, but the power consumption increases
Solution Approach 1:
The patent segments the compensation functions into separate filters with specialized roles. The dispersion compensation filter handles chromatic dispersion while the adaptive equalization filter handles other distortions. This segmentation allows each filter to operate with shorter tap lengths, reducing the computational load and power consumption while maintaining high compensation accuracy.
Solution Approach 2:
The patent changes the operational parameters of the filtering system by introducing a dedicated dispersion compensation filter that operates independently. This parameter change allows the adaptive equalization filter to reduce its tap length and computational complexity, thereby reducing power consumption while maintaining overall system performance.
3Measurement precision
If a long tap length is used in the adaptive equalization filter to handle all linear degradations, then the compensation accuracy for group delay ripple is improved, but the device complexity increases
Solution Approach 1:
The patent segments the linear degradation compensation into specialized functions: the dispersion compensation filter handles chromatic dispersion and group delay ripple, while the adaptive equalization filter handles polarization mode dispersion and other distortions. This functional segmentation allows each filter to use a shorter, simpler structure while achieving high compensation accuracy for its specific function.
Solution Approach 2:
The patent introduces a dispersion compensation filter as an intermediary that pre-processes the signal to remove chromatic dispersion and group delay ripple effects. This intermediary filtering simplifies the subsequent adaptive equalization task, allowing the use of a less complex filter structure while maintaining high compensation accuracy.
Data Source
AI summary
A distortion compensation filter whose filter coefficient is adaptively controlled compensates for a distortion included in a reception signal obtained by performing coherent reception of a signal transmitted from a transmitter in a receiver. A group delay ripple calculation device calculates a group delay included in the reception signal based on a filter coefficient of a distortion compensation filter and calculates group delay ripple from the calculated group delay. The feedback calculation unit calculates a phase response based on the calculated group delay ripple. The feedback calculation unit feeds the calculated phase response back to one or more filters having a phase compensation function disposed in a stage before an adaptive equalization filter included in the receiver, and causes one or more filters to at least partially compensate for the group delay ripple.