| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 106 === Recently, visible light (wavelength ranging from 380 to 780 nm) communication (VLC) has been recognized as a promising technology to provide high-speed data communication. By integrating with the existing lighting facility, it can provide both indoor lighting and high-security wireless communication in the smart office. Besides, it can provide wireless communication through optical signal without electromagnetic interference in hospital, aircraft and space shuttle, where the traditional Wi-Fi is not available. Previously, VLC systems based on light-emitting diode (LED) have been widely reported due to its desirable lighting performance, yet the transmission performance was severely limited by its narrow modulation bandwidth. Accordingly, laser diode (LD) with higher brightness, longer coherent distance and larger transmission capacity has been considered as a more desirable transmitter toward high-speed VLC system. Typically, either using blue LD covered with a phosphorous film or mixing red/green/blue LDs by a diffuser, the high-speed white-light VLC system can be constructed. In this thesis, the violet LD (VLD) at 405 nm is employed in the CdSe-QD based white-lighting VLC and the red/green/violet (RGV) mixed white-lighting VLC systems to fulfill the requirement for various applications.
First, a novel white-lighting VLC system based on the violet laser diode (VLD) adhered with the cadmium selenide (CdSe) quantum dots (QDs) doped polydimethylsiloxane (PDMS) film is exhibited for both high-speed communication and white-lighting. The CdSe-QD doped PDMS film is applied as the color converter to provide red and green fluorescence, and the white light is generated by mixing residual violet light with excited fluorescence. The proposed white light exhibits a correlated color temperature (CCT) of 6389 K, a color rendering index (CRI) of 63.3 and a Commission International del1’Eclairage (CIE) coordinate at (0.3214, 0.2755) with a divergent angle of 127 degree. By encoding the VLD with 16-quadrature amplitude modulation discrete multi-tone (16-QAM DMT) data, the white-lighting VLC system can support a data rate at 9.6 Gbit/s with a FEC demanded BER of 3.59×10-3.
Afterwards, the VLC composed by red/green/violet (RGV) LDs and a yellow light emitting diode (Y-LED) diverged by a frost glass is proposed for both the indoor high-quality white-lighting and the high-speed communication. By respectively coding the RGV LDs with the filtered DMT data for wavelength division multiplexing (WDM) wireless communication, the high total data rate of 34.8 Gbit/s is achieved. To fulfill the demanded color rendering index (CRI) for indoor lighting, a Y-LED is utilized to contribute the broadband yellowish-orange light, and the optical density filter with an OD value of 0.6 is employed to attenuate the red laser light. With attenuation, the RGV-LD+Y-LED white-lighting VLC system can support a transmission data rate of 28.4 Gbit/s with a CCT of 4852 K, a high CRI of 71.6, the CIE coordinate at (0.3652, 0.4942), the illuminance of 6800 lx with a divergent angle of 60 degree.
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