Quantum Key Receiver Miniaturization via Signal Fiber Separation
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Solution Overview
Problem
In quantum key transmission, the use of time division multiplexing and polarization multiplexing to isolate local oscillator signals from quantum signals prevents miniaturization of the receive end and reduces the signal-to-noise ratio due to the finite extinction ratio of polarization multiplexers.
Innovation Solution
A quantum key sending apparatus adjusts the polarization directions of quantum and local oscillator signals using a polarization controller, allowing them to be transmitted through different optical fibers, eliminating the need for time division and polarization multiplexing, which enables miniaturization of the receive end and improves signal-to-noise ratio by utilizing all optical fiber resources for the quantum signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If time division multiplexing and polarization multiplexing are used to isolate local oscillator signal from quantum signal, then crosstalk is reduced, but the receive end cannot be miniaturized and additional optical path difference is required
Solution Approach 1:
The patent extracts the local oscillator signal from the quantum signal transmission path by using a separate optical fiber dedicated to carrying the local oscillator signal. This separation eliminates the need for complex time division multiplexing and polarization multiplexing components at the receive end, while still preventing crosstalk between the two signals.
2Object-affected harmful factors
If polarization multiplexing is used to transmit local oscillator signal and quantum signal, then signal isolation is achieved, but finite extinction ratio limits local oscillator signal strength and reduces signal-to-noise ratio
Solution Approach 1:
The patent segments the transmission system into two independent channels: one optical fiber for the local oscillator signal and another optical fiber for the quantum signal. This segmentation eliminates the need for polarization multiplexing and its associated extinction ratio limitations, allowing the local oscillator signal to maintain full strength without interfering with the quantum signal.
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 integrated and miniaturized quantum key receivers with enhanced signal-to-noise ratios by eliminating the need for additional optical path differences and finite extinction ratio limitations, thereby improving the transmission efficiency of quantum signals.
Implementation Method 1
A quantum key sending apparatus adjusts the polarization directions of quantum and local oscillator signals using a polarization controller
Data Source
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AI summary
This application discloses a quantum key transmission apparatus and system, and relates to the field of quantum communications technologies. In this application, the quantum key transmission apparatus may adjust a polarization direction of a quantum signal and a polarization direction of a reference signal by using a polarization controller, and send a local oscillator signal and an adjusted quantum signal to different optical fibers for transmission. In this way, the local oscillator signal and the quantum signal no longer need to be isolated from each other through time division multiplexing and polarization multiplexing. On this basis, in a quantum signal receiver at a receive end, no additional optical path difference needs to be introduced for latency compensation. Therefore, the receive end can be integrated and miniaturized.