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Lens design-based optimization of path loss in a high data-rate indoor visible light communication link

Ahmad, F and Ramachandrapura Nagaraju, S and Jyothsna, KM and Biswas, R and Raghunathan, V (2020) Lens design-based optimization of path loss in a high data-rate indoor visible light communication link. In: Proceedings of SPIE - The International Society for Optical Engineering, 3-4 February 2020, San Francisco; United States.

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Official URL: https://dx.doi.org/10.1117/12.2545939


In this paper, lens design-based optimization of the optical system for a blue laser diode downconverted with remote phosphor based indoor visible light communication link is studied using optical raytracing and experimentally characterized for illumination/ communication performance. Data modulated 450nm blue laser-diode is used to excite a remote-phosphor to down-convert the blue spectrum to white which is transmitted over a direct line-of-sight free-space link and detected using an amplified p-i-n detector. The combination of transmit and receive lenses are optimized in Zemax ray-tracing software with the objective of minimizing the path loss or maximizing the light collection efficiency within the detector area when placed at different transmitter-to-receiver separation distance. It is found that contrary to the typical 1/d2 dependence typically used in VLC system models, the path loss can be minimized at the required link distance by choosing the lens to phosphor and p-i-n detector distance at the transmitter and receiver side respectively. At the optimized location, the VLC link is experimentally characterized by transmitting digital data at a maximum rate of 700 Mbps and bit error rates (BER) obtained is much below 10-3. BER versus distance is also found to follow the inverse relation of the path-loss versus distance indicating that the optimized lens positions help in achieving improved data through-put due to minimization of the path losses. Optical spectra and color content measurements indicate that the optimized lens positioning results in enhanced blue content at the receive side due to efficient collection of the data modulated blue components at the expense of the green and red components of the down-converted white light. Further improvements to this link can be achieved by simultaneously optimizing performance at multiple wavelengths spanning blue, green and red wavelengths or using lower color temperature phosphors to improve illumination performance, albeit at the expense of some deterioration to the communication performance. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

Item Type: Conference Paper
Publication: Proceedings of SPIE - The International Society for Optical Engineering
Publisher: SPIE
Additional Information: cited By 0; Conference of Free-Space Laser Communications XXXII 2020 ; Conference Date: 3 February 2020 Through 4 February 2020; Conference Code:165705
Keywords: Bit error rate; Deterioration; Light; Light emission; Optical instrument lenses; Optical systems; Phosphors; Transmitters, Color temperatures; Communication performance; Content measurements; Light collection efficiency; Multiple wavelengths; Optimizing performance; Receiver separations; Transmitter and receiver, Visible light communication
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 11 Feb 2021 06:08
Last Modified: 11 Feb 2021 06:08
URI: http://eprints.iisc.ac.in/id/eprint/67541

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