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Proceedings Paper

Non-line-of-sight beam-steered optical wireless communication (Conference Presentation)
Author(s): Zizheng Cao; Xuebing Zhang; Gerwin Osnabrugge; Juhao Li; Ivo Vellekoop; A. M. J. Koonen

Paper Abstract

To meet the ever-growing demand for faster wireless communications, optical wireless communication (OWC) has been extensively developed, which can bring a huge improvement in communication capabilities, both in terms of ultra-high capacity per user and in terms of electromagnetic interference-free wireless communication [1-2]. However, one fundamental challenge for OWC arises when the direct pathway between transmitter and receiver is obstructed by an obstacle. When an optical beam is illuminated on a rough surface, the light is scattered to different directions, which results in the near-isotropic, speckled optical intensity distribution of the diffused light. Therefore, the intensity of the diffused light is inherently much lower than that of a collimated incident light arriving directly at the receiver. Usually, the proposed solutions do not address the diffusion mechanism itself but instead of focusing on the compensation of the diffusion-caused loss by increasing the system power, or they avoid diffuse reflection and/or scattering altogether, i.e., using a near-perfect mirror as a reflector. As a long-standing challenge, such diffuse loss critically hinders the application of OWC. Here, a novel non-line-of-sight (NLOS) beam reconfigurable optical wireless data transmission system for energy-efficient communication is proposed and experimentally verified. This is an overview of our previous work which is published on Light: Science&Applications [3]. By spatially modulating the light incident on a rough surface using a spatial light modulator (HOLOEYE PLUTO Phase Only SLM), the diffused light is focused on an optical wireless receiver, which breaks the NLOS limitation of OWC. A record-breaking 30-Gbit/s orthogonal frequency division multiplexing (OFDM) signal is transmitted over a diffused 110-mm optical wireless link with >17-dB gain, in an angular range of 20°. In this experiment, the 1550-nm laser source is used to match the well-established fibre-system. The OFDM signal is modulated onto the optical domain and amplified to the eye-safety power limit of 10 dBm. Then the light is collimated and delivered to an SLM. The angle between the incident beam and the reflected beam is 45°. To match the Gaussian beam (size), the central 1024-by-1024 pixels are activated, which are further grouped into segments of 64×64 pixels, yielding a total of 16×16 segments for data transmission. All pixels in a segment can be phase modulated from 0 to 2π in increments of π/8 individually. The phase-compensated beam is illuminated onto a rough barrier, which emulates the rough surface of ceilings or walls in an indoor scenario. Here, a Thorlabs polystyrene screen (EDU-VS1/M) and a sandblasted aluminium film are verified. To collect the diffused light to realize a large-capacity transmission, the light is coupled into a single-mode fibre using a collimator. Enabled by the feedback signal from a power meter, the received optical signal can be optimized by using the wavefront shaping [4]. The data-rate of 30 Gbit/s with blocked sightlines is achieved using the stepwise sequential algorithm [4].

Paper Details

Date Published: 9 March 2020
Proc. SPIE 11307, Broadband Access Communication Technologies XIV, 113070F (9 March 2020); doi: 10.1117/12.2544700
Show Author Affiliations
Zizheng Cao, Technische Univ. Eindhoven (Netherlands)
Xuebing Zhang, Technische Univ. Eindhoven (Netherlands)
Gerwin Osnabrugge, Univ. of Twente (Netherlands)
Juhao Li, Peking Univ. (China)
Ivo Vellekoop, Univ. of Twente (Netherlands)
A. M. J. Koonen, Technische Univ. Eindhoven (Netherlands)

Published in SPIE Proceedings Vol. 11307:
Broadband Access Communication Technologies XIV
Benjamin B. Dingel; Katsutoshi Tsukamoto; Spiros Mikroulis, Editor(s)

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