Optical Dispersion Compensation Using Overlapped FFT Signal Blocks
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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 that segments digital received signals into blocks with overlap, performs Fourier transformation, applies coefficients based on wavelength dispersion and delay amounts, and performs inverse Fourier transformation to increase compensation without increasing the magnitude of fast Fourier transformation and inverse conversion.
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 received signal into multiple blocks with overlapping portions, processes each block separately through Fourier transformation, and combines the results. This segmentation allows wavelength dispersion compensation to be achieved through multiple small-scale Fourier transformations rather than one large transformation, reducing circuit scale while maintaining compensation effectiveness for extended transmission distances
2Reliability
If large fast Fourier transformation and inverse converter circuits are used to increase wavelength dispersion compensation amount, then wavelength dispersion compensation amount is increased, but power consumption increases
Solution Approach 1:
By segmenting the signal processing into multiple blocks that can be processed independently and in parallel, the patent reduces the computational burden on a single large Fourier transformation circuit. This approach achieves the required wavelength dispersion compensation amount while lowering power consumption through distributed, smaller-scale processing operations
3Length of moving object
If the magnitude of fast Fourier transformation is increased to compensate for longer distance transmission, then transmission distance is extended, but circuit complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the long transmission distance compensation into multiple shorter processing segments corresponding to different signal blocks. Each block undergoes Fourier transformation with appropriate scaling, and the results are combined to achieve overall long-distance compensation without requiring a single large-scale transformation circuit
Solution Approach 2:
The patent introduces a temporal dimension by processing multiple blocks sequentially in time, each with overlapping portions. This allows the system to achieve equivalent compensation to a large single transformation through multiple smaller transformations performed across different time intervals, effectively trading time for reduced circuit complexity
Data Source
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.