| Author: | Cao, Yonggui |
| Title: | Single-pixel optical encoding and transmission with random numbers |
| Advisors: | Chen, Wen (EEE) Yu, Changyuan (EEE) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Optical communications Free space optical interconnects Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Electrical and Electronic Engineering |
| Pages: | xx, 111 pages : color illustrations |
| Language: | English |
| Abstract: | Free-space optical communication (FSO) is promising for data transmission, offering specific advantages over traditional systems in some applications, e.g., high bandwidth. Optical communication in free space is also less susceptible to interference and signal degradation, when atmospheric attenuation and multipath fading happen. However, FSO still faces significant challenges in practice. 1) The impact of scattering media, e.g., fog, smoke, or dust, can significantly degrade signal quality and limit data transmission range. 2) Security of optical data transmission needs to be addressed in many scenarios. Therefore, it is crucial to investigate high-fidelity optical data transmission in free space, which can overcome the challenges associated with scattering media and ensure the security of optical data transmission in free space. In this thesis, new optical encoding approaches for high-fidelity optical diffraction and transmission through scattering media in free space are proposed using a series of 2D arrays of random numbers as information carriers. A series of 2D arrays of random numbers are directly generated to encode the ghosts, i.e., original signals or images. In addition, a new transmission scheme is designed to realize optical transmission through dynamic scattering media (e.g., smoke or turbid water). Real-time optical thickness is calculated to describe temporal change of the properties of optical wave in dynamic environment. Transmission noise and errors caused by dynamic smoke are temporally corrected. It is experimentally demonstrated that irregular analog signals can always be retrieved with high fidelity. To enhance transmission rate of the proposed system and evaluate robustness of the designed methods against dynamic and complex scattering media, the proposed optical data transmission scheme is optimized. New algorithms are proposed to generate 2D binary arrays (i.e., information carriers). Therefore, the transmission rate would be increased significantly, since a digital micro-mirror device with a high switching rate can be applied. In addition, security of the developed optical data transmission schemes is also analyzed, and an improved encrypted transmission scheme is proposed to realize high-fidelity and high-security data transmission. Different security keys, i.e., computer-generated keys and physically-generated keys, are applied in a scattering environment. An optimized data transmission system is also introduced to improve security of optical data transmission, when it is applied in a dynamic and complex scattering environment. Experimental results demonstrate feasibility and effectiveness of the proposed methods. The studies in this thesis address two key scientific problems in optical data transmission in free space, i.e., high-fidelity optical data transmission through scattering media and high-security optical data transmission through scattering media. The studies pave a way for realizing high-fidelity and high-security free-space optical data transmission through scattering media using the concept of ghost diffraction and transmission with random numbers. |
| Rights: | All rights reserved |
| Access: | open access |
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