Optical Signal Distortion Determination Using Chromatic Dispersion and PMD Correlation
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Solution Overview
Problem
Current optical communication systems lack an efficient model to consider combined effects of chromatic dispersion (CD), polarization mode dispersion (PMD), and the optical Kerr effect for determining signal distortion, particularly in high regenerator-less reach systems with low-dispersion or dispersion-managed fiber links.
Innovation Solution
An apparatus and method that determine signal distortion by introducing distortion measures for nonlinear signal distortions on single transmission spans and their correlations across spans, using chromatic dispersion and differential group delay values to combine signal powers and distortion measures, allowing for compensation of electrical field vectors and calculation of signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital signal processing techniques are employed to compensate linear signal distortions, then linear distortion compensation is improved, but nonlinear signal distortions cannot be effectively addressed
Solution Approach 1:
The patent segments the overall signal distortion into two distinct components: linear distortion (handled by existing DSP techniques) and nonlinear distortion (handled by the new correlation-based model). This segmentation allows each type of distortion to be addressed with appropriate methods without interfering with the other.
Solution Approach 2:
The patent introduces correlation coefficients as an intermediary parameter that quantifies the relationship between nonlinear distortions on different transmission spans. These correlation coefficients serve as a bridge between the physical effects (CD, PMD, Kerr effect) and the overall nonlinear distortion measurement, enabling the model to account for span interactions.
2Reliability
If existing GN model is used for nonlinear interference estimation, then some nonlinear effects are considered, but combined effects of CD, PMD, and optical Kerr effect are not efficiently modeled
Solution Approach 1:
The patent changes the key parameter from individual span distortion measurements to correlation coefficients between spans. By focusing on the correlation parameter ρ(i,k) rather than treating each span independently, the model efficiently captures the combined effects of CD, PMD, and Kerr effect without requiring exponentially more computational resources.
Solution Approach 2:
The patent performs preliminary calculations of distortion measures and correlation coefficients based on known fiber parameters (dispersion, PMD values) before actual signal transmission. This allows the model to be pre-configured with the specific characteristics of each transmission span, enabling efficient real-time distortion estimation without complex runtime computations.
3Ease of operation
If distortion measures for each transmission span are determined independently, then individual span analysis is simplified, but correlations between spans are ignored
Solution Approach 1:
The patent merges the individual span distortion measures by introducing correlation coefficients that quantify the relationship between spans. The total nonlinear distortion is calculated by combining individual span contributions weighted by their correlation coefficients, thus merging simple individual analyses into an accurate overall assessment.
4Length of stationary object
If high regenerator-less reach is pursued in optical communication systems, then transmission distance is extended, but nonlinear signal distortions emerge and increase
Solution Approach 1:
The patent provides a feedback mechanism by calculating the total nonlinear distortion based on correlation coefficients and using this information to optimize transmission parameters. The model enables system operators to predict distortion levels at different distances and adjust launch powers, dispersion management, or other parameters to maintain signal quality over extended reaches.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach efficiently accounts for nonlinear channel interactions influenced by CD and PMD, enabling accurate estimation and compensation of signal distortions, thereby improving the performance of optical communication systems.
Implementation Method 1
Linear and nonlinear signal distortions can e.g. be introduced by transmission of the optical signal over a number of fiber transmission spans of the optical transmission channel and can e.g. result from chromatic dispersion (CD)
Implementation Method 2
Linear and nonlinear signal distortions can e.g. be introduced by transmission of the optical signal over a number of fiber transmission spans of the optical transmission channel and can e.g. result from chromatic dispersion (CD), polarization mode dispersion (PMD)
Implementation Method 3
Linear and nonlinear signal distortions can e.g. be introduced by transmission of the optical signal over a number of fiber transmission spans of the optical transmission channel and can e.g. result from chromatic dispersion (CD), polarization mode dispersion (PMD), and/or an optical Kerr effect
Data Source
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AI summary
The invention relates to an apparatus (100) for determining a signal distortion of an optical signal, the optical signal comprising a number of frequency channels (m), the signal distortion being introduced by an optical transmission channel having a number of transmission spans (i, k), the apparatus (100) comprising a provider (101 ) being configured to provide a signal power (P) of the optical signal for each frequency channel (m) and for each transmission span (i, k) to obtain a number of signal powers, to provide a chromatic dispersion, CD, value for each frequency channel (m) and for each transmission span (i, k) to obtain a number of CD values, the number of CD values indicating a CD of the optical signal, and to provide a differential group delay, DGD, value for each frequency channel (m) and for each transmission span (i, k) to obtain a number of DGD values, the number of DGD values indicating a polarization mode dispersion of the optical signal, a determiner (103) being configured to determine a number of first distortion measures (κ) upon the basis of the number of CD values and the number of DGD values, the number of first distortion measures (κ) indicating a nonlinear signal distortion of the optical signal induced on a single transmission span (i, k), and to determine a number of second distortion measures (p) upon the basis of the number of CD values and the number of DGD values, the number of second distortion measures (p) indicating a correlation between nonlinear signal distortions of the optical signal induced on transmission span (i) and on transmission span (k), and a combiner (105) being configured to combine the number of signal powers, the number of first distortion measures (κ), and the number of second distortion measures (p) to obtain the signal distortion of the optical signal.