Polarization Demultiplexing Unit Using Delay and Rotation
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Solution Overview
Problem
Current polarization demultiplexing techniques in optical transmission networks face high computational complexity and power consumption due to the use of butterfly filters with many filter coefficients, and training-assisted approaches suffer from additional overhead and limited temporal validity.
Innovation Solution
A polarization demultiplexing unit that uses a limited number of parameters, including a delay parameter, phase shift parameter, and rotation angle parameter, to efficiently demultiplex signals, implemented using a digital signal processor with a cost function to determine these parameters iteratively, reducing computational complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a butterfly filter with many filter coefficients is used for polarization demultiplexing, then the demultiplexing performance is improved, but the computational complexity and power consumption increase significantly
Solution Approach 1:
The patent extracts only the essential parameters needed for polarization demultiplexing (delay parameter, phase shift parameter, and rotation angle parameter) from the full set of filter coefficients, thereby reducing computational complexity while maintaining demultiplexing performance. This is achieved by identifying and processing only the critical degrees of freedom in the polarization signal.
Solution Approach 2:
The patent transforms the problem from determining many filter coefficients to determining just three key parameters (delay, phase shift, and rotation angle). This parameter reduction is achieved through mathematical transformation of the polarization demultiplexing problem, converting it into an optimization task for these specific parameters using a cost function.
2Measurement precision
If the filter length is increased to improve demultiplexing performance, then the performance is improved, but the adaptation speed decreases
Solution Approach 1:
The patent extracts only the essential temporal parameter (delay parameter) from the filter coefficients, reducing the number of parameters that need to be adapted. This extraction of critical parameters enables faster adaptation while maintaining the ability to compensate for polarization mode dispersion effects.
3Measurement precision
If training assisted approaches are used to determine filter coefficients, then the demultiplexing accuracy is improved, but additional transmission overhead is required
Solution Approach 1:
The patent enables the system to determine the three key parameters (delay, phase shift, and rotation angle) autonomously using a cost function and optimization algorithms, without requiring external training sequences. The system self-adjusts by processing the actual data stream and minimizing a cost function based on signal properties, thereby eliminating training overhead while maintaining accuracy.
Data Source
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AI summary
The present document relates to optical transmission networks. In particular, the present document relates to the demultiplexing of polarization division multiplexed optical signals. A polarization demultiplexing unit (200, 300, 400) configured to determine a first and a second polarization demultiplexed signal (121, 122) from a first and a second polarization signal (111, 112) is described. The polarization demultiplexing unit (200, 300, 400) comprises a delay unit (203, 303, 403) configured to delay a signal derived from the first polarization signal (111) relative to a signal derived from the second polarization signal (112) by a delay parameter, to yield a first delayed signal. Furthermore, the polarization demultiplexing unit comprises a spatial rotation entity (101, 202) configured to perform a spatial rotation of the first delayed signal and of the signal derived from the second polarization signal (112) using a phase shift parameter and a rotation angle parameter. In addition, the polarization demultiplexing unit comprises a parameter determination unit (103) configured to determine the phase shift parameter and the rotation angle parameter using a cost function depending on a property of the first and second polarization demultiplexed signals (121, 122).