Optical data transmission through scattering media in free space with single-pixel detection

Abstract

Optical data transmission through scattering media is challenging, which has attracted much interest in many fields, such as marine ecology and biomedical science. The existing methods suffer from huge computational cost and limited application ranges, which cannot be effectively applied to complex environment, especially in strongly and randomly scattering media. In this thesis, high-fidelity and high-robustness optical analog-signal transmission through scattering media is proposed and systematically studied, e.g., turbid water and biological tissue. The first challenging task is how to realize high-fidelity and high-efficiency optical analog-signal transmission in static and turbid water. I have proposed a new method to optically transmit analog signals in free space through static and turbid water. Each pixel of original signal is sequentially encoded into random amplitude-only patterns as information carrier. A single-pixel detector is utilized to collect light intensities at the receiving end. Experimental results demonstrate that the proposed method shows high robustness against different propagation distances through turbid water and resists the effect of various turbulence factors. The proposed method is easy to operate and is cost-effective, which could open up a novel insight into optical signal transmission in free space through turbid water. The second challenging task is to deal with the obstacles in the optical path, e.g., walls, rocks, suspended particles and organic matters or planktonic organisms in water. A non­-line-of-sight (NLOS) optical transmission system is built to realize high-fidelity optical analog-signal transmission through turbid water around a corner. Optical experimental results demonstrate the feasibility of the proposed method when there is an obstacle behind turbid water. In addition, the proposed method possesses a wide detection range at the receiving end, which is of great significance in practical applications. The third challenging task is how to achieve high-accuracy optical analog-signal transmission in free-space through non-static scattering media, e.g., dynamic and turbid water. I have proposed an effective method by using a series of dynamic scaling factors to temporally correct light intensities recorded by a single-pixel bucket detector. A fixed reference pattern is utilized to obtain the series of dynamic scaling factors during optical data transmission in free space. It is demonstrated that the proposed scheme is robust against water-flow-induced turbulence and turbid water, and high-fidelity free-space optical information transmission is realized at wavelengths of 658.0 nm and 520.0 nm. The fourth challenging task is how to realize accurate optical information transmission and achieve large penetration depth through thick biological tissues. The proposed method utilizes zero-frequency modulation to generate a series of 2D random amplitude-only patterns. The proposed method realizes accurate optical information transmission through thick biological tissues, and can overcome the challenges, e.g., penetration through small-thickness tissues and low quality of the retrieved signals. My study in this thesis opens up a new research perspective for theoretical understanding and experimental verifications of high-fidelity free space optical analog-signal transmission through complex scattering media including static and dynamic environment. My research work will benefit the development of optical wireless data transmission in various research fields, e.g., marine ecology and biomedical science.