Atmospheric compensation experiments on advanced free-space optical coherent communication systems

Ronald E. Meyers

Nicholas J. Savino, Jacob M. Leamer, Ravi K. Saripalli +3 more

Free-space optical (FSO) communication can be subject to various types of distortion and loss as the signal propagates through non-uniform media. In experiment and simulation, we demonstrate that the state of polarization and degree of polarization of light passed though underwater bubbles, causing turbulence, is preserved. Our experimental setup serves as an efficient, low cost alternative approach to long distance atmospheric or underwater testing. We compare our experimental results with those of simulations, in which we model underwater bubbles, and separately, atmospheric turbulence. Our findings suggest potential improvements in polarization based FSO communication schemes.

J. Jeyarani, Jeyaseelan Alan

Abstract This investigation examines the use of a Quadrature Phase Shift Keying (QPSK)-based Free-space Optical (FSO) Communication system combined with Quantum Key Distribution (QKD) for improved security and dependability in disaster management situations. We tackle the problems caused by atmospheric turbulence by utilizing a hybrid gamma–gamma and log–normal channel model to precisely characterize the FSO link. The proposed system’s purpose is to offer secure, high-bandwidth communication for emergency response coordination, telemedicine, and data transmission in environments affected by disasters. We present a system design and performance evaluation based on the hybrid atmospheric model, discuss the potential advantages, drawbacks, and countermeasures of the approach, and propose future research avenues, encompassing real-time adjustment, modulation variability, and field testing. Our implementation of real-time adaptation mechanisms lowers the BER by about 30 % under conditions affected by turbulence, while hybrid FSO/RF switching maintains uninterrupted connectivity during severe atmospheric attenuation.

Baris I. Erkmen, Bruce E. Moision, Kevin M. Birnbaum

Ning Wang, Xuegui Song, Julian Cheng +1 more

Security issues of terrestrial free-space optical (FSO) communications over strong atmospheric turbulence are investigated. Based on a subcarrier intensity modulated FSO system model, we first study the scintillation reciprocity of the system from a coherence time perspective. A private secret key-based cryptosystem with key management is introduced to enhance FSO security, and a key agreement approach is proposed based on statistics of the random atmospheric turbulence-induced fading channel measurements. Secret key rate of the key agreement scheme is studied for the strong turbulence channel characterized by the K-distribution. Practical key agreement protocol is designed based on channel identification.

聂敏 Nie Min, 高 锟 Gao Kun, 杨光 YANG Guang +2 more