Free-Space Optical Communication Terminal With Adaptive Optics
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Solution Overview
Problem
High-data-rate communication links between ground stations and earth-orbiting satellites face challenges due to atmospheric turbulence and signal loss caused by particulates, as well as pointing jitter, making error-free data transfer over long distances difficult.
Innovation Solution
The implementation of a free-space optical communication system using a communication terminal with a large data buffer, automatic repeat request (ARQ) controller, and high-speed optical modem, along with adaptive optics to mitigate channel fading, enabling reliable data transfer at speeds up to 100 Gb/s through wavelength-division multiplexing and flexible ARQ protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If optical communication links propagate through atmosphere for long distances, then data transmission capability is enabled, but signal loss and turbulence cause communication reliability to deteriorate
Solution Approach 1:
The patent segments data into blocks with identifiers and transmits them in organized units. The ARQ controller divides data into manageable blocks, assigns identifiers, and tracks transmission status of each block individually, enabling reliable retransmission of only failed blocks rather than entire data streams.
Solution Approach 2:
The patent implements feedback mechanisms where the receiving terminal sends acknowledgments and negative acknowledgments back to the transmitting terminal. The ARQ controller uses this feedback to determine which data blocks need retransmission, continuously adapting the transmission process based on channel conditions.
2Reliability
If adaptive optics are added to mitigate channel fading, then communication reliability is improved, but device complexity increases
Solution Approach 1:
The patent introduces an ARQ controller as an intermediary component that manages the complexity of reliable communication. Rather than making the entire system complex through adaptive optics, the ARQ controller handles error management, buffer management, and retransmission control as a dedicated intermediary layer.
Solution Approach 2:
The patent dynamically changes operational parameters such as buffer size, data block size, and transmission rate based on channel conditions. The ARQ controller adjusts these parameters in response to feedback about signal quality, allowing the system to adapt to atmospheric conditions without requiring complex hardware modifications.
3Reliability
If large data buffers are used with ARQ protocols, then error-free data transfer is achieved, but data transmission delay increases
Solution Approach 1:
The patent employs dynamic buffer management where the ARQ controller actively monitors channel conditions and adjusts buffer utilization accordingly. When channel conditions are good, data flows through with minimal buffering. When errors occur, the buffer temporarily holds data for retransmission, making the buffering behavior dynamic rather than static.
Solution Approach 2:
The patent prepares data blocks in advance with identifiers and organizes them in buffers before transmission. This preliminary organization allows the ARQ controller to quickly retrieve and retransmit specific blocks without delay, as the data is pre-segmented and identified rather than requiring post-transmission processing.
Data Source
AI summary
Communication systems and methods for high-data-rate, high-efficiency, free-space communications are described. High-speed optical modems and automatic repeat request can be employed to transmit large data files without data errors between remote devices, such as an earth-orbiting satellite and ground station. Data rates over 100 Gb/s can be achieved.