Directional Phase-Shifter Polarization Modulator for Error Compensation
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Solution Overview
Problem
Existing optical signal transmission systems suffer from undesired modulation errors due to parasitic effects, particularly in polarization-modulated signals, which are difficult to distinguish from intended modulation, leading to signal quality degradation.
Innovation Solution
A modulator unit is designed with a polarizing beam splitter, phase shifter, and Faraday rotators to split and recombine polarization components in opposite directions, using a polarization-dependent phase modulator to modulate one component while maintaining the other unchanged, thereby eliminating directional-dependent parasitic influences and reducing modulation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional modulator unit is used to modulate the optical signal, then the modulation function is achieved, but parasitic effects cause undesired changes in the carrier signal that cannot be distinguished from desired modulation, degrading signal quality
Solution Approach 1:
The optical signal is segmented into two separate polarization components (first and second polarization components) that are guided through opposite directions in the optical ring. This segmentation allows each component to experience parasitic effects independently, and their combination at the polarizing beam splitter enables cancellation of common-mode parasitic influences while preserving the desired modulation signal.
Solution Approach 2:
The patent introduces asymmetry by having the first and second polarization components propagate in opposite directions through the optical ring. This asymmetric configuration ensures that directional-dependent parasitic effects affect both components differently, allowing the system to distinguish between desired modulation and undesired parasitic influences through differential detection.
2Loss of information
If polarization components are modulated in a conventional manner, then information is transmitted, but directional-dependent parasitic influences cause modulation errors that are difficult to distinguish from intended modulation
Solution Approach 1:
The optical ring configuration provides a feedback mechanism where the first polarization component is modulated and then combined with the second polarization component after both have traversed the ring in opposite directions. This feedback loop allows the system to compensate for parasitic effects by comparing the phase and polarization states of the two components, enabling error correction and improved modulation accuracy.
Solution Approach 2:
The patent applies inversion by having the second polarization component propagate through the optical ring in the opposite direction to the first polarization component. This reverse propagation causes directional-dependent parasitic effects to manifest differently for each component, enabling the system to identify and eliminate modulation errors caused by these parasitic influences through differential analysis.
3Device complexity
If a simple modulator design is used, then device complexity is reduced, but polarization errors occur due to inability to compensate for parasitic effects
Solution Approach 1:
The optical ring structure serves multiple functions simultaneously: it guides both polarization components, provides phase modulation capability, enables polarization rotation through Faraday rotators, and facilitates parasitic effect compensation through the combination of oppositely propagating components. This multi-functionality achieves high polarization accuracy without requiring separate compensation mechanisms, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges the modulation function and the parasitic compensation function into a single integrated optical ring structure. By combining the first and second polarization components in the same optical path but with opposite propagation directions, the system achieves polarization error compensation without requiring separate compensation devices, thus limiting the increase in overall device complexity while maintaining high reliability.
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
The modulator unit effectively compensates for phase errors and reduces modulation errors by ensuring both polarization components experience consistent parasitic influences, maintaining signal quality and enabling accurate polarization modulation.
Implementation Method 1
The phase shifter includes a first Faraday rotator, a second Faraday rotator, and a polarization-dependent phase modulator. The first Faraday rotator is configured such that it changes a polarization direction of passing optical signals in a first polarization change direction and the second Faraday rotator is configured such that it changes a polarization direction of passing optical signals
Implementation Method 2
The first optical partial link or the second optical partial link contains a polarization rotator, which is designed to change a polarization direction of optical signals that pass the polarization rotator so that the first polarization component has the same polarization direction as the second polarization component
Implementation Method 3
The polarizing beam splitter is designed to split the input signal into the first polarization component and the second polarization component
Implementation Method 4
The polarization-dependent phase modulator is designed to execute a phase modulation of only one polarization component
Data Source
AI summary
A modulator unit for modulating the phase of a polarization component of an optical signal contains a polarizing beam splitter and a phase shifter. The beam splitter splits an input signal into a first and a second polarization components having different polarization directions and sends the components in opposite directions via an optical ring containing the phase shifter. A polarization rotator is arranged in the optical ring, which changes the polarization direction of passing optical signals, so that the polarization components arriving at the phase shifter are polarized in the same direction. The phase shifter changes the polarization directions of the incoming optical signals such that they are polarized orthogonally to one another in the phase shifter. One polarization component is modulated. When the optical signals leave the phase shifter, their polarization direction is brought back to the original polarization direction.