Free Space Optical Communication Using Orthogonal Aberration Modes
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Solution Overview
Problem
Free space optical communication systems are susceptible to atmospheric turbulence and aberrations, which degrade performance and limit data transfer rates due to susceptibility of orbital angular momentum modes to distortions and intensity fluctuations.
Innovation Solution
The system employs a transmitting unit that encodes user data onto orthogonal aberration modes of a laser beam using binary holograms, generating a data-encoded beam that is less affected by atmospheric distortions, and a receiving unit with a high-speed wavefront sensor to detect and decode these modes, immune to intensity fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If orbital angular momentum states are used to increase data content in the beam, then data transfer rate is improved, but the system becomes severely affected by aberrations in the medium
Solution Approach 1:
The patent changes the encoding parameter from traditional intensity modulation to orthogonal aberration mode modulation. By representing data as amplitudes of orthogonal aberration modes (e.g., Zernike polynomials), the system achieves higher data rates while the orthogonal nature of these modes provides inherent immunity to atmospheric turbulence and aberrations, resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent combines multiple orthogonal aberration modes (such as Zernike polynomials of different orders) to create a composite encoding scheme. This composite approach allows simultaneous transmission of multiple data streams through different modes, increasing data rate while the orthogonality of the composite modes ensures robustness against medium-induced aberrations
2Stability of the object's composition
If laser speckle tracking and locking principle is employed to minimize intensity fluctuation, then intensity stability is improved, but operating speed is limited by tracking and locking mechanism capability
Solution Approach 1:
The patent replaces the mechanical tracking and locking system with an optical-based orthogonal mode detection system. Instead of physically tracking and locking the laser speckle pattern, the system uses orthogonal aberration mode decomposition to inherently reject intensity fluctuations, achieving both stability and high speed without mechanical limitations
3Reliability
If liquid-crystal SLM is used for adaptive aberration correction, then aberration correction capability is improved, but correction rate is limited by response time of liquid crystal molecules
Solution Approach 1:
The patent extracts the aberration information directly from the transmitted signal itself by decomposing the received beam into orthogonal aberration modes. This eliminates the need for separate adaptive correction systems like liquid-crystal SLM, achieving high-speed aberration measurement and compensation without being limited by molecular response times
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 results in a communication system that is inherently less susceptible to wavefront distortions and intensity fluctuations, enabling faster and more reliable data transmission even in the presence of atmospheric disturbances.
Implementation Method 1
at least one light modulator displaying binary holograms and configured to: encode using alternate polarity of said user data shifted to ternary numbers, said incident laser beam at two or more consecutive instant of time
Implementation Method 2
at least one wavefront sensor, adapted to: detect the presence of aberration in said input laser beam
Implementation Method 3
Free space optics (FSO) is a telecommunication technology that uses optical beam in free space to transmit data between two points
Data Source
AI summary
The present invention provides a free space optical communication system that uses orthogonal modes of aberration in a laser beam as means for encoding the information. The system comprises a transmission station which transmits the user defined information in terms of the amplitudes of certain orthogonal aberration modes present in the transmitted beam. The beam then travels through free space before it reaches the receiving station. The receiving station comprises a high speed wavefront sensor of light beams. The wavefront sensor measures the amplitudes of various orthogonal aberration modes present in the incident beam at different instants of time. The amplitudes of the orthogonal modes at a certain regular time interval are then used to extract the user information.