Optical Fiber Amplifier Gain Limiting for Secure QKD Pulses
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Solution Overview
Problem
Standard optical amplifiers for quantum key distribution are vulnerable to signal diversion by eavesdroppers due to high gain sensitivity to pump power increases and suffer from significant signal losses caused by components like optical isolators and couplers, compromising security and data integrity.
Innovation Solution
A method and system for optical signal amplification that determine a target operating gain and maximum gain, with an active fiber section and pumping device, to limit signal diversion and maintain security, while preventing pulse shape distortion and energy imbalance, using a core cross-sectional area adjustment and controlled pumping power to restrict eavesdropping possibilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If standard amplifiers use high pump absorption coefficient to maximize efficiency, then pump power to signal power conversion efficiency is improved, but gain sensitivity to pump increase increases making the system vulnerable to signal diversion
Solution Approach 1:
The patent changes the pump absorption coefficient parameter from high to low values. By using a low pump absorption coefficient, the amplifier reduces gain sensitivity to pump power increases, preventing eavesdroppers from diverting signals by simply increasing pump power while maintaining acceptable conversion efficiency through optimized fiber length and pump power levels.
2Stability of the object's composition
If optical isolators and couplers are used to ensure stable operation, then operational stability is improved, but signal losses increase which is unacceptable for secure data transmission
Solution Approach 1:
The patent extracts and removes traditional components like optical isolators and couplers from the amplifier system. By eliminating these components that cause signal losses, the system achieves secure data transmission while maintaining operational stability through alternative design approaches in the fiber amplifier architecture.
3Power
If active fiber section length is increased to achieve target gain, then amplification capability is improved, but pulse shape distortion increases for high-energy pulses
Solution Approach 1:
The patent optimizes the active fiber section length parameter to achieve a balance between amplification capability and pulse shape preservation. By carefully selecting the fiber length, the system provides sufficient gain for quantum key distribution while minimizing pulse shape distortion that would occur with excessively long fiber sections.
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 solution effectively limits signal diversion, maintains low error rates, and enhances security by ensuring that any increase in pumping power beyond the operating level results in minimal signal leakage, thus protecting the integrity of quantum key distribution.
Implementation Method 1
an optical amplifier with an active fiber section and a pumping device
Data Source
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AI summary
The present disclosure refers to a method for optical signal amplification, the method being implementable in a system which comprises: a transmission line (10) for transmitting optical signals between a first data processing device (11) and a second data processing device (12); and an optical amplifier (14) disposed at the transmission line (10), the optical amplifier (14) comprising an active fiber section (15) and a pumping device (16). The method comprises: determining a target operating gain of the optical amplifier (14); determining a target maximum gain of the optical amplifier (14); determining an active fiber section length such that the optical signals are amplified with at most the target maximum gain; determining a core cross-sectional area size of the active fiber section (15) based on a maximum allowable pulse shape distortion and a target maximum energy per pulse such that high-energy pulses with the target maximum energy per pulse are distorted by at most the maximum allowable pulse shape distortion; and determining an operating pumping power of the pumping device (16) below the maximum pumping power such that the optical signals are amplified with the target operating gain. Further, a system for optical signal amplification is disclosed.