TF-QKD Polarization-Maintaining Coupling for Stable Phase Locking
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Solution Overview
Problem
Conventional TF-QKD systems face challenges with complex and unstable polarization coupling, requiring manual calibration and high-cost electronics, leading to inconsistent polarization states due to environmental factors, which affect frequency locking and phase stability.
Innovation Solution
Implementing a TF-QKD system with polarization-maintaining wavelength division multiplexers to couple frequency-locking and phase reference lights, using inherent optical characteristics for stable polarization coupling without external intervention, ensuring consistent polarization states through integrated modules at Alice and Bob terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional wavelength division multiplexing is used to monitor channel phase perturbation, then phase monitoring capability is improved, but polarization coupling consistency deteriorates due to environmental factors
Solution Approach 1:
The patent introduces a polarization coupling module as an intermediary component that actively maintains polarization consistency between signal light and reference light. This module compensates for environmental-induced polarization changes, enabling stable polarization coupling while allowing accurate phase monitoring through the wavelength division multiplexer.
Solution Approach 2:
The system implements feedback control by continuously monitoring polarization states and adjusting the polarization coupling module accordingly. This ensures that polarization coupling consistency is maintained despite environmental perturbations, while the phase monitoring function operates independently with high precision.
2Stability of the object's composition
If manual calibration is used to maintain polarization coupling, then polarization consistency is improved, but system complexity and operational burden increase
Solution Approach 1:
The polarization coupling module operates autonomously to maintain polarization consistency without requiring manual calibration. The system self-adjusts to environmental changes, eliminating the need for operator intervention while maintaining stable polarization coupling. This reduces both system operational complexity and the burden of manual maintenance.
3Stability of the object's composition
If EPC (electronic polarization controller) is used for polarization compensation, then polarization coupling is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex, expensive EPC devices with a simpler polarization coupling module that achieves the same polarization compensation function. This alternative implementation maintains polarization coupling consistency while significantly reducing electronic complexity and system cost, making the solution more practical for deployment.
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
Stabilizes frequency locking and phase compensation, reducing system complexity and cost while enhancing integration and stability against environmental perturbations, ensuring reliable quantum key distribution.
Implementation Method 1
the frequency-locking reference light and the phase reference light have different wavelengths, and the first wavelength division multiplexer is configured to perform wavelength division coupling on the frequency-locking reference light and the phase reference light in a polarization-maintaining manner
Implementation Method 2
perform wavelength division coupling on the frequency-locking reference light and the phase reference light in a polarization-maintaining manner
Implementation Method 3
the first beam-splitting module is configured to split the combined reference light to form two components of combined reference light
Implementation Method 4
the first frequency-locked light source is configured to generate a first optical signal in a frequency-locking manner by using the frequency-locking reference light
Implementation Method 5
the first quantum state preparation module is configured to prepare a quantum state on the first optical signal to generate the first quantum optical signal
Implementation Method 6
perform wavelength division coupling on the first quantum optical signal and the phase reference light in a polarization-maintaining manner to form the first combined signal light
Implementation Method 7
perform wavelength division coupling on the first quantum optical signal and the phase reference light in a polarization-maintaining manner
Implementation Method 8
the measurement module is configured to measure an interference signal of the first and second quantum optical signals
Data Source
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Figure 2a~2b
Figure 3
AI summary
Disclosed in the present invention are a TF-QKD system and a stable TF-QKD implementation method. The frequency-locked reference light and the phase reference light are subjected to polarization-maintaining wavelength division coupling into a reference optical signal at the Charlie end, so that in the Alice end and the Bob end, two polarization-maintaining wavelength division multiplexers are used in combination with the frequency locking technology to realize polarization-consistent wavelength division coupling of a quantum optical signal and the phase reference light, and an EPC or manual intervention is not needed, so as to ensure the stability of polarization-consistent coupling using a simple optical path. In addition, polarization compensation can be firstly performed on the reference optical signal in the Alice end and the Bob end, so that the stability of the frequency-locked reference light and the phase reference light is also ensured is ensured by a polarization-consistent coupling module in the present application, thereby ensuring the stability of the frequency locking effect.