Polarization Transform Estimation for Optical Wave Recovery
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Solution Overview
Problem
Polarization multiplexed optical transmission systems face challenges in accurately recovering original optical waves due to birefringence-induced changes in polarization states during transmission, leading to inefficiencies and the need for iterative searches for alignment transforms, which are slow and unreliable.
Innovation Solution
A method involving measuring the electrical field of the polarization multiplexed optical wave, determining a transform to align orthogonal polarization states with receiver axes, and applying this transform to recover the original optical waves, eliminating the need for iterative searches by using a polarization diversity receiver and control systems to estimate and apply the necessary alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If iterative search methods are used to find alignment transforms for polarization multiplexed optical waves, then the transform can be found, but the process is slow and unreliable
Solution Approach 1:
The patent applies preliminary action by measuring the polarization state of the transmitted optical wave before transmission through the optical link, and using this pre-measured state to directly determine the alignment transform. This eliminates the need for time-consuming iterative searches at the receiver end, as the transform is already known from the transmitter-side measurement.
Solution Approach 2:
The patent replaces the mechanical iterative search process with a direct mathematical calculation. Instead of repeatedly adjusting and testing alignment transforms through iterative searches, the system uses a calculated transform based on the measured polarization state, substituting the mechanical search process with a computational approach that is both faster and more reliable.
2Productivity
If polarization multiplexing is used to improve spectral efficiency, then transmission capacity doubles, but birefringence causes polarization state changes during transmission
Solution Approach 1:
The patent implements feedback by measuring the actual polarization state of the transmitted optical wave and using this measurement information to determine the appropriate alignment transform. This feedback loop allows the system to compensate for birefringence-induced polarization changes, maintaining accurate recovery of the multiplexed signals despite environmental variations during transmission.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the alignment transform parameters based on the measured polarization state. When birefringence causes polarization state changes during transmission, the system modifies the transform parameters to compensate for these changes, thereby maintaining stable and accurate signal recovery throughout varying transmission conditions.
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 allows for reliable, quick, and precise alignment of polarization states, enhancing the recovery of original optical waves and improving the efficiency of polarization multiplexed systems by directly estimating the transform from measured states.
Implementation Method 1
an optical transmitter uses a polarization beam combiner (PBC) to combine two optical waves having orthogonal polarization states
Implementation Method 2
as a result of birefringence in optical fiber, and because of the dependence of birefringence on environmental factors such as temperature and vibration, the polarization states of the optical waves combined in a polarization multiplexed optical wave change as the waves propagate through an optical link
Implementation Method 3
optical receivers are typically configured to separate a polarization multiplexed optical wave into optical waves having horizontal and vertical polarization states
Data Source
AI summary
First and second transmitted optical waves having orthogonal polarization states are combined in a polarization multiplexed optical wave. At an optical receiver, an electrical field of the polarization multiplexed optical wave is measured. A plurality of polarization states of the polarization multiplexed optical wave is determined from the measured electrical field. From the plurality of polarization states, a transform that aligns the orthogonal polarization states of the first and second transmitted optical waves with respect to principal axes of the optical receiver is estimated. The first and second transmitted optical waves are recovered by applying the transform to one of i) the polarization multiplexed optical wave and ii) the measured electrical field of the polarization multiplexed optical wave.