Free-space 16-ary orbital angular momentum coded optical communication system based on chaotic interleaving and...

Area of Science:

• Optical Communications
• Free-Space Optics
• Signal Processing

Background:

• Orbital angular momentum (OAM) states in free-space optical communication are susceptible to atmospheric turbulence (AT) distortions.
• These distortions cause crosstalk and power discrepancies, degrading system performance.
• Existing methods require enhancement to mitigate these effects effectively.

Purpose of the Study:

• To propose and evaluate a novel system for free-space optical communication using OAM states.
• To enhance system performance and robustness against atmospheric turbulence.
• To investigate the effectiveness of a chaotic interleaver and a convolutional neural network (CNN) as an adaptive demodulator.

Main Methods:

• Implementation of a novel chaotic interleaver with low-density parity-check coded OAM-shift keying.
• Utilization of a convolutional neural network (CNN) as an adaptive demodulator for enhanced detection.
• Employing the conjugate light field method for signal detection and analyzing performance under various turbulence conditions, distances, and signal-to-noise ratios (SNR).

Main Results:

• The proposed system with chaotic interleaving shows superior performance compared to systems without it, especially at longer propagation distances.
• The CNN-based demodulator achieves high accuracy, mean average precision (MAP), and area under the curve (AUC), demonstrating effectiveness in distinct turbulence conditions.
• Stochastic gradient descent with momentum and adaptive moment estimation optimizers yield better results than root mean square propagation for the CNN.

Conclusions:

• The integration of a chaotic interleaver and a CNN adaptive demodulator significantly improves the performance of OAM-based free-space optical communication systems.
• The proposed system demonstrates enhanced resilience to atmospheric turbulence, achieving better peak SNR and lower mean square error.
• The study validates the system's viability for reliable digital image transmission under challenging environmental conditions.