Optical Receiver Pulse Concentration for Deep Space Communication
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Solution Overview
Problem
Current satellite communication systems using Pulse Position Modulation (PPM) face limitations in transmitting information over long distances due to high instantaneous power requirements, low efficiency in converting electrical to optical power, and issues with heat dissipation and fiber optical element damage, especially in deep space communication.
Innovation Solution
A receiver system that utilizes polarisation-phase sequences of pulses generated by a modulated continuous operation laser, with optical elements such as polarisation beam splitter cubes, half-wave plates, and polarisation modulators to concentrate energy into a single pulse, increasing the instantaneous power-to-average power ratio while maintaining high efficiency and using a correcting subsystem to enhance the acceptance angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Q-switching is used to achieve high instantaneous optical power for deep space communication, then the instantaneous optical power reaches kilowatt level, but the transmission speed decreases considerably due to cavity modulation frequency limitation to several hundred kHz
Solution Approach 1:
The patent uses periodic pulse generation with variable pulse width modulation instead of Q-switching. The laser operates in pulsed mode with repetition frequencies that can be much higher than Q-switching limits, achieving both high instantaneous power and high transmission speed by independently controlling pulse width and repetition rate
Solution Approach 2:
The patent changes the operating parameters of the laser system by using pulse width modulation technology. Instead of modulating the Q-factor of the resonating cavity, the system directly controls the pulse duration and repetition frequency, allowing instantaneous power to reach kilowatt level while maintaining transmission speeds limited only by the pulse generator capability rather than cavity dynamics
2Power
If Q-switching is used to achieve high instantaneous optical power, then deep space communication becomes possible, but the efficiency of conversion of electrical into optical power amounts to only 10-15%
Solution Approach 1:
The patent uses pulse width modulation to create copies of optical pulses with varying durations. By modulating the width of pulses from a continuous wave laser or laser operating below threshold, the system achieves high instantaneous power with much better electrical-to-optical conversion efficiency, avoiding the inefficient Q-switching process
Solution Approach 2:
The patent replaces the mechanical Q-switching mechanism with an electronic pulse width modulation control system. This substitution eliminates the inefficiencies of cavity modulation and directly controls the optical output through electronic timing circuits, achieving both high instantaneous power and improved conversion efficiency
3Length of stationary object
If high instantaneous optical power is used for deep space communication, then transmission distance increases, but heat dissipation problems and risk of damaging fibre optical elements occur
Solution Approach 1:
The patent uses periodic pulsed operation instead of continuous high power operation. By delivering energy in short pulses with appropriate duty cycles, the system achieves the necessary instantaneous power for long-distance transmission while allowing the optical elements to cool between pulses, preventing heat accumulation and damage
Solution Approach 2:
The patent performs preliminary pulse shaping and timing control before the optical pulses enter the transmission medium. By pre-modulating the pulse width and timing using electronic circuits, the system achieves the required peak power without subjecting the optical elements to sustained high power conditions that would cause heating and damage
4Productivity
If standard PPM modulation is used with continuous operation laser, then transmission speed reaches several megabits per second, but instantaneous power remains at only several watts enabling communication only over relatively short distances
Solution Approach 1:
The patent introduces dynamic pulse width modulation to the PPM system. Instead of using fixed-width pulses from a continuous wave laser, the system dynamically varies the pulse width and timing to achieve both high instantaneous power and maintain high transmission speeds. The pulse generator can be modulated at speeds comparable to standard PPM while delivering much higher peak powers
Solution Approach 2:
The patent merges the advantages of pulsed laser operation with PPM modulation. By combining pulse width modulation capability with position modulation, the system achieves both the high instantaneous power of pulsed lasers and the high data rate of PPM, extending communication distance while maintaining speed
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 effective transmission of weak signals over long distances with increased power efficiency and tolerance to signal distortions, suitable for satellite communication, telecommunication, and deep space applications.
Implementation Method 1
comprises at least one polarisation splitting element... part of the optical signal following a shorter, and part of it a longer optical path length
Implementation Method 2
at least one plate rotating the polarisation (HWP, QWP)
Implementation Method 3
optical elements such as polarisation beam splitter cubes, half-wave plates, and polarisation modulators to concentrate energy into a single pulse
Data Source
AI summary
Exemplary arrangements relate to receivers for receiving information using very weak light pulses. The exemplary arrangements include an input optical signal having a sequence of light pulses, optical elements, and a detector. The optical elements include at least one polarisation modulator, at least one polarisation splitting cube, an element with a different optical path length for different polarisations, and at least one polarization rotating plate. Part of the optical signal follows a shorter optical path length, and part of it follows a longer optical path length. The element with different optical path lengths is placed between two polarisation beam splitter cubes. The beam splitter cubes split and then merge the sequence of pulses reducing the sequence by half and forming an amplified signal readable by the detector. Exemplary arrangements also relate to a method for transmitting information using the exemplary arrangement.