Two-step system for image receiving in OAM-SK-FSO link

Area of Science:

• Optical communication systems
• Free-space optical communication
• Signal processing

Background:

• Atmospheric turbulence (AT) poses significant challenges for free space optical (FSO) communication systems, particularly those employing orbital angular momentum shift keying (OAM-SK).
• Traditional methods struggle to maintain high data fidelity under turbulent atmospheric conditions.

Purpose of the Study:

• To propose and evaluate a novel two-step combinational system for enhancing image data reception quality in OAM-SK-FSO links affected by AT.
• To demonstrate the superiority of the proposed system over conventional approaches in terms of data fidelity and turbulence resistance.

Main Methods:

• Development of an AT-detector-based multi-Convolutional Neural Network (ATDM-CNN) demodulator to detect AT strength and recognize OAM modes.
• Simulation-based comparison of ATDM-CNN with a single-CNN (S-CNN) demodulator for OAM mode recognition rates.
• Implementation of a secondary correction step using a rank-order adaptive median filter (RAMF) and a very-deep super-resolution (VDSR) network to address residual errors.

Main Results:

• The ATDM-CNN demodulator demonstrated a significant improvement in OAM mode recognition rates compared to the S-CNN.
• The combined RAMF-VDSR approach effectively corrected residual information errors with minimal data loss, even in severe AT conditions.
• The two-step system achieved a much higher quality of received image data.

Conclusions:

• The proposed two-step system, integrating ATDM-CNN and RAMF-VDSR, offers a robust solution for high-fidelity image data transmission in OAM-SK-FSO systems under atmospheric turbulence.
• This approach significantly enhances the reliability and performance of FSO communication links.