Wavelength Dispersion Compensation Using Multi-Stage Frequency Coefficients
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Solution Overview
Problem
In digital coherent transmission, existing wavelength dispersion compensation methods require large fast Fourier transformation and inverse converter circuits to achieve longer distance transmission, leading to increased circuit scale and power consumption.
Innovation Solution
A wavelength dispersion compensation apparatus with a coefficient multiplication unit that includes multiple multiplier arrays and an adder, utilizing a lookup table for coefficient multiplication results and shift processing to apply coefficients based on frequency positions, allowing for increased compensation without increasing the magnitude of Fourier transformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large fast Fourier transformation and inverse converter circuits are used to increase wavelength dispersion compensation amount, then transmission distance is extended, but circuit scale and power consumption increase
Solution Approach 1:
The patent divides the frequency domain equalization process into multiple stages, where each stage processes a portion of the wavelength dispersion compensation. The coefficient multiplication unit applies different coefficients to different frequency components in multiple passes, allowing the system to achieve large wavelength dispersion compensation through incremental processing rather than requiring a single large-scale FFT circuit.
Solution Approach 2:
The patent employs periodic application of coefficient multiplication operations across multiple time slots. The coefficient multiplication unit repeatedly applies different coefficient sets to the frequency domain signal in a periodic manner, enabling cumulative wavelength dispersion compensation effect without requiring proportionally larger circuit规模.
2Reliability
If large fast Fourier transformation and inverse converter circuits are used to increase wavelength dispersion compensation amount, then transmission distance is extended, but power consumption increases
Solution Approach 1:
By segmenting the coefficient multiplication into multiple smaller operations applied sequentially, the patent reduces the peak power consumption compared to a single large-scale operation. Each coefficient multiplication stage consumes less power individually, and the cumulative effect achieves the required wavelength dispersion compensation for extended transmission distances.
Solution Approach 2:
The patent applies coefficient multiplication in multiple partial steps rather than attempting to compensate for all wavelength dispersion in a single operation. Each coefficient multiplication stage addresses a portion of the total dispersion, and the cumulative partial actions achieve the full compensation effect with lower overall power consumption.
3Reliability
If the magnitude of fast Fourier transformation is increased to compensate for larger wavelength dispersion, then compensation amount increases, but device complexity increases
Solution Approach 1:
The patent maintains a fixed, manageable FFT magnitude but compensates for increased wavelength dispersion by applying multiple stages of coefficient multiplication to the frequency domain output. This segmentation of the compensation function keeps the Fourier transformation circuit scale constant while achieving variable compensation amounts through subsequent processing stages.
Data Source
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AI summary
An electric digital received signal obtained from a received optical signal is segmented into blocks of a certain length with an overlap of a length determined in advance with an adjacent block. Fourier transformation is performed for each of the blocks. The blocks subjected to the Fourier transformation are stored consecutively in time series, a coefficient determined based on a wavelength dispersion compensation amount according to one of frequency positions and a delay amount according to one of the frequency positions and one of time positions is applied to each of frequency component values included in a plurality of the stored blocks, and the blocks to which the coefficient has been applied and which are obtained by adding up the frequency component values to which the coefficient has been applied for each of the frequency positions are generated. Inverse Fourier transformation is performed on the generated blocks to which the coefficient has been applied. A part of the overlap subjected to the inverse Fourier transformation is removed.