Quantum Channel Crosstalk Suppression via Optical Filtering
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Solution Overview
Problem
In quantum key distribution systems, the strong optical power of classical channels causes crosstalk noise that degrades the signal-to-noise ratio of weak quantum channels, limiting transmission distance and efficiency, and existing methods fail to effectively suppress this noise without requiring wide channel spacing or inefficient frequency use.
Innovation Solution
The system employs a multiplexing and demultiplexing configuration with specific transmission characteristics and optical power settings to isolate the quantum channel from the classical channel, using a multiplexer to suppress noise components and a demultiplexer to minimize crosstalk light, ensuring the classical channel does not affect the quantum channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If classical channels with large optical power are multiplexed on the same optical transmission medium as quantum channels with weak optical power, then frequency resource utilization is improved, but crosstalk noise from the classical channel degrades the signal-to-noise ratio of the quantum channel
Solution Approach 1:
The patent introduces an optical filter as an intermediary component between the classical channel and quantum channel. This filter selectively transmits optical signals at wavelengths suitable for quantum communication while blocking crosstalk noise from the classical channel, thereby enabling both channels to coexist on the same transmission medium without mutual interference
Solution Approach 2:
The patent applies different optical power levels and filtering characteristics to different sections of the transmission system. The classical channel operates at high optical power while the quantum channel receives filtered, lower-power signals, creating local quality differences that prevent crosstalk while maintaining frequency resource efficiency
2Object-affected harmful factors
If wide channel spacing is used to eliminate crosstalk, then signal-to-noise ratio is improved, but frequency resource utilization deteriorates
Solution Approach 1:
Instead of relying solely on wide channel spacing, the patent introduces an optical filter as a mediator that actively suppresses crosstalk noise. This allows channels to be placed closer together in frequency while still maintaining adequate signal-to-noise ratio, thereby improving frequency resource utilization without sacrificing signal quality
3Object-affected harmful factors
If optical power of classical channel is reduced to suppress crosstalk, then signal-to-noise ratio of quantum channel is improved, but transmission distance and communication capability of classical channel deteriorate
Solution Approach 1:
The optical filter serves as a mediator that protects the quantum channel from crosstalk without requiring the classical channel to reduce its optical power. The filter blocks harmful noise while allowing the classical channel to maintain high power levels for long-distance transmission, thus resolving the contradiction between suppressing crosstalk and maintaining transmission capability
Data Source
AI summary
In a system where a quantum channel and a classical channel are multiplexed on a single optical transmission line and information is transmitted from a transmitter to a receiver through the quantum channel, the classical channel is inhibited from affecting the quantum channel. To this end, the transmission characteristics of a transmitter-side wavelength multiplexer/demultiplexer for the classical channel, the transmission characteristics of a receiver-side wavelength multiplexer/demultiplexer for the quantum channel, and the optical power of a light source for the classical channel are designed so that crosstalk light due to spontaneous emission light and crosstalk light due to nonlinear optical effects can be suppressed, and the classical channel does not affect the quantum channel.