Laser Pulse Quadrature Control Without External Modulators
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Solution Overview
Problem
Existing optical transmitters for classical and quantum communication rely on bulky and power-hungry external electro-optic modulators, leading to instability, high costs, and limited bandwidth, which are particularly problematic in quantum key distribution systems due to low signal-to-noise issues when propagating weak light over long distances.
Innovation Solution
A compact apparatus and method that generates optical pulses using a laser device driven by electrical pulses with pre-determined distributions, operating below and above the laser threshold to randomize phases and control quadrature values, eliminating the need for external modulators and enhancing robustness and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external electro-optic modulators are used to encode information onto optical pulses, then communication performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the external electro-optic modulator from the transmitter structure. Instead of using separate modulator components, the invention directly modulates the laser source itself to generate optical pulses with desired quadrature distributions, thereby simplifying the overall device architecture while maintaining communication performance
Solution Approach 2:
The laser device is designed to perform multiple functions: it serves as both the light source and the modulation element. By directly generating optical pulses with controlled quadrature distributions, the laser replaces the traditional separate modulator component, reducing device complexity while achieving the same communication function
2Reliability
If external electro-optic modulators are used for encoding, then signal modulation capability is improved, but power consumption increases
Solution Approach 1:
The patent merges the modulation function into the laser device itself. By directly generating optical pulses with the desired quadrature distributions through controlled electrical excitation of the laser, the system eliminates the need for separate high-power modulator components, thereby reducing overall power consumption while maintaining signal modulation capability
3Speed
If external electro-optic modulators are used, then modulation bandwidth is achieved, but device size and compactness are compromised
Solution Approach 1:
The patent removes the bulky external modulator components from the transmitter. By using a compact laser device that directly generates modulated optical pulses, the invention achieves the required electro-optic bandwidth without the need for large-scale external modulation hardware, thereby enabling compact transmitter design
4Reliability
If external electro-optic modulators are used, then signal encoding capability is improved, but stability over time deteriorates due to operating point fluctuations
Solution Approach 1:
The patent combines the modulation function directly into the laser device, eliminating the separate modulator component that suffers from operating point drift. By generating modulated optical pulses directly at the laser source, the system achieves stable signal encoding capability without the time-dependent instability issues associated with external electro-optic modulators
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 enables high-performance, compact, and cost-effective optical transmitters for classical and quantum communication, improving robustness and bit-rate, while simplifying schemes and reducing the need for expensive single photon technology, thereby enhancing the reliability of quantum key distribution systems.
Implementation Method 1
a laser device configured to output the light pulses
Implementation Method 2
a pulse driver configured to supply the electrical pulses with amplitudes/intensities obeying a pre-determined probability distribution (in time, namely, within one temporal repetition period/duty cycle of electrical pulses) to the laser device such that quadrature values of the light pulses obey another pre-determined probability distribution
Data Source
AI summary
The present disclosure relates to an apparatus for generating light pulses, comprising a laser device configured to output the light pulses and a pulse driver configured to supply electrical pulses to the laser device to drive the laser device. Furthermore, the pulse driver is configured to supply the electrical pulses with amplitudes/intensities obeying a pre-determined probability distribution to the laser device such that quadrature values of the light pulses obey another pre-determined probability distribution.