Free-Space Optical Communication Range Extension via Duty Cycle Modulation
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Solution Overview
Problem
Free-space optical communication systems face significant signal strength attenuation over long distances, particularly in high-speed data transmission, making it challenging to accurately recover data signals due to high range loss.
Innovation Solution
A system and method that includes a first modulator generating a modulated optical signal, a second modulator turning off select pulses to create a low-duty cycle modulated signal, and an average-power limited optical amplifier boosting the signal strength, allowing for increased signal power while maintaining compatibility with existing receiver systems and minimizing disruption to carrier phase recovery algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transmitted optical signal power is increased to overcome range loss, then signal strength at receiver is improved, but average power limitations of optical amplifiers prevent further power increase
Solution Approach 1:
The patent applies periodic pulsed action by turning off selected pulses within pulse frames to create variable duty cycle patterns. This allows the optical amplifier to deliver high peak power during active pulses while maintaining acceptable average power levels, thereby increasing signal strength at the receiver without exceeding average power limitations.
Solution Approach 2:
The patent changes the duty cycle parameter of the optical signal by selectively turning off pulses. This parameter change allows the same optical amplifier to produce different effective signal strengths by adjusting the proportion of active pulses, enabling high signal strength transmission within average power constraints.
2Reliability
If high signal power is transmitted to maintain data integrity at high speeds, then data transmission reliability is improved, but signal attenuation over long distances worsens
Solution Approach 1:
By using periodic pulsed transmission with variable duty cycles, the system maintains high peak power levels necessary for reliable high-speed data detection while the periodic off periods allow average power to remain within transmission limits, compensating for long-distance attenuation.
Solution Approach 2:
The system dynamically adjusts the duty cycle by selectively turning off pulses based on transmission conditions. This dynamic adjustment allows optimization of signal strength for reliability while adapting to distance-related attenuation, maintaining data integrity over long distances.
3Measurement precision
If pulse width is increased to improve signal detection, then receiver sensitivity is improved, but duty cycle increases leading to higher average power consumption
Solution Approach 1:
The patent changes the duty cycle parameter by selectively turning off pulses, allowing individual pulse widths to remain sufficiently wide for good receiver sensitivity while the reduced duty cycle keeps average power consumption within acceptable limits.
4Productivity
If more pulses are transmitted per frame to increase data rate, then productivity is improved, but signal power per pulse decreases due to average power constraints
Solution Approach 1:
The system uses periodic pulsed transmission where selected pulses are turned off to create variable duty cycles. This allows maintaining high peak power for pulses that are transmitted, ensuring sufficient signal strength even when data rate is increased through higher pulse frequencies.
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 enhances signal power, enabling effective transmission over greater distances with increased sensitivity for high-speed data communication systems, maintaining compatibility with existing receivers and minimizing disruptions to recovery algorithms.
Implementation Method 1
an average-power limited optical amplifier coupled to the second modulator, for generating an amplified modulated signal from the low-duty cycle signal
Data Source
AI summary
Various embodiments for a system and method for a range-enhanced high-speed free-space optical communication are described herein. Generally, the optical communication system may include a first modulator, a second modulator and an average-power limited optical amplifier. The first modulator may receive an input optical signal and generate a modulated optical signal. The second modulator may receive the modulated signal and may be operable to turn-off a select number of pulses in each modulated pulse frame of the modulated signal to generate a low-duty cycle modulated signal. The average-power limited optical amplifier may then generate an amplified modulated signal from the low-duty cycle signal, wherein the amplified modulated signal comprises a plurality of amplified pulse frames with each amplified pulse frame defining an amplified version of a corresponding each low-duty cycle pulse frame.