Laser Pulse Control for Phase Randomization Without Gain Switching
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Solution Overview
Problem
Existing technologies have not effectively addressed the challenge of achieving secure and efficient phase randomization in quantum key distribution systems, particularly in applications such as quantum cryptography, with existing systems requiring phase modulators and gain switching circuitries, which are costly and complex, and introduce noise-related effects.
Innovation Solution
A system and method for discrete phase randomization in quantum key distribution systems that employs direct phase modulation by switching power supply signals between working and idle supply levels above the lasing threshold, ensuring continuous and uninterrupted laser light emission without the need for phase modulators or gain switching, using a control system to randomly alter time intervals or power levels of the idle supply signals to achieve random phase changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase modulators are used to achieve phase randomization, then phase randomization is achieved, but system complexity and cost increase
Solution Approach 1:
The patent extracts the phase randomization function from a separate phase modulator component and integrates it directly into the laser light source by modulating the electrical injection current. This eliminates the need for an external phase modulator, thereby reducing system complexity while maintaining phase randomization capability.
Solution Approach 2:
The patent combines the phase randomization function with the laser light source operation by using the electrical injection current modulation to achieve both laser generation and phase randomization simultaneously. This merging of functions reduces the number of components and simplifies the overall system architecture.
2Reliability
If gain switching circuitries are used to achieve phase randomization, then phase randomization is achieved, but noise-related effects are introduced
Solution Approach 1:
The patent changes the operating parameters of the laser light source by modulating the electrical injection current between different levels (above and below threshold current) to achieve phase randomization. This parameter-based approach avoids the need for complex gain switching circuitries and reduces associated noise effects.
3Device complexity
If discrete phase randomization with minimal phase values is used, then system complexity is reduced, but security may be compromised
Solution Approach 1:
The patent implements discrete phase randomization with a minimal set of phase values (N=4 or N=10) which is sufficient for security requirements. This partial action approach achieves adequate security without the complexity of continuous phase randomization, balancing security needs with system simplicity.
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 solution ensures efficient phase randomization in quantum key distribution systems, enhancing security and reducing system complexity and noise-related effects.
Implementation Method 1
a laser light source configured to generate laser light when driven by electrical supply signals having a power level greater than a lasing threshold of the laser light source
Implementation Method 2
a control system configured to randomize a phase of the laser light by randomly altering time intervals or power levels of the idle supply signals
Data Source
AI summary
Techniques for controlling light/radiation emitted from a laser light source are disclosed, wherein electric supply signals of a laser light source are modulated for generating a plurality of fixed predefined working supply signals configured to drive the laser light source during time intervals in which the light/radiation thereby emitted is encoded with data, mid variable idle supply signals for driving the laser light source between the data encoding time intervals. The modulating comprises at least one of generating the idle supply signals to include random time intervals and fixed idle supply signal level/intensity greater than a lasing threshold of said laser light source, and/or generating the idle supply signals to include idle supply signals having random levels/intensities or randomly alternated levels/intensitics greater than a lasing threshold of said laser light source, to thereby affect random phase changes between said data encoding time intervals without reducing the supply signal below said lasing threshold.