Multi-Channel Multi-Beaming Optical Transmitter for Atmospheric Turbulence
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Solution Overview
Problem
Existing optical communication systems face challenges in high data rate transmission due to signal fading caused by atmospheric turbulence, which is not effectively addressed by conventional methods such as channel equalization, forward error correction, and spatial diversity, especially when the optical phase carries information.
Innovation Solution
Non-coherent combining of light beams from multiple data sources with different wavelengths, frequencies, or polarization angles at transmitting apertures, followed by dense wavelength division multiplexing, to reduce signal fading by ensuring statistically uncorrelated turbulence effects across the beams, thereby improving signal-to-noise ratio and data throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel equalization and forward error correction are applied at the physical layer, then errors due to atmospheric turbulence can be corrected, but the complexity of encoding and decoding increases prohibitively with codeword length
Solution Approach 1:
The invention segments the transmitted signal into multiple independent optical beams with different spatial, spectral, or temporal characteristics. Each beam experiences independent fading due to atmospheric turbulence, allowing the receiver to combine them to recover the original signal without requiring complex long codeword FEC decoding.
Solution Approach 2:
The invention transitions from single-dimensional error correction (temporal FEC coding) to multi-dimensional diversity (spatial, spectral, and temporal dimensions). By encoding information across multiple beams in different dimensions, the system achieves error resilience through diversity combining rather than through complex sequential FEC decoding.
2Reliability
If data retransmission is implemented upon detecting data loss, then errors can be corrected, but additional round-trip latency is introduced
Solution Approach 1:
The invention performs preliminary error protection by transmitting redundant information across multiple independent beams before the receiver needs to decode the signal. This proactive approach eliminates the need for reactive retransmission, as the diversity beams already contain the information needed to overcome fading effects in real-time.
3Reliability
If spatial diversity with multi-beaming is used to mitigate fading, then turbulence-induced errors are reduced, but the approach is only suitable when information is encoded by intensity and not when optical phase carries information
Solution Approach 1:
The invention creates a universal multi-beam diversity system that can handle both intensity-encoded and phase-encoded information. By using multiple beams with different spatial, spectral, or temporal characteristics, the system can recover both amplitude and phase information even when individual beams experience severe fading, making it applicable to various modulation schemes including PSK, QAM, and coherent detection.
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 enhances data transmission reliability and throughput by reducing symbol loss due to turbulence-induced fading, allowing for higher data rates and lower latency in optical communication systems.
Implementation Method 1
turbulence can be a significant source of channel impairment. For example, anomalous refraction of an optical beam (e.g., scintillation) can be caused by small-scale fluctuations in air density that result from temperature or pressure gradients along the path of the optical beam
Implementation Method 2
anomalous refraction of an optical beam (e.g., scintillation) can be caused by small-scale fluctuations in air density
Implementation Method 3
dense wavelength division multiplexing, to reduce signal fading by ensuring statistically uncorrelated turbulence effects across the beams
Data Source
AI summary
Optical communication systems and methods using coherently combined optical beams are disclosed. A representative system includes a first data source for sending first data at a first frequency of a first optical beam to a first aperture, and at a second frequency of a second optical beam to a second aperture. The system further includes a second data source for sending second data at a third frequency of a third optical beam to the first aperture, and at a fourth frequency of a fourth optical beam to the second aperture. The system also includes a first interleaver of the first aperture configured to interleave the first data at the first frequency and the second data at the third frequency; and a second interleaver of the second aperture configured to interleave the first data at the second frequency and the second data at fourth frequency.