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  • 學位論文

以雷射二極體為基礎之照明與水下可見光通訊系統

Laser diode based free-space, underwater, and white-lighting visible light communication

指導教授 : 林恭如
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摘要


可見光(波長範圍350~750 nm)通訊可將全球高速網路延伸至特定空間,是未來銜接人類社會所有通訊網路的必要發展,藉由使用具有比發光二極體更高調變頻寬與更低發散角的藍光雷射二極體,不但能提高可見光通訊之傳輸速率,也能以低衰減係數有效進行水下通訊,同時若搭配黃色螢光片或混合以紅光與綠光雷射二極體,更可在通訊外添加白光照明功能。 首先,在最佳化操作參數後,所使用之藍光雷射二極體可實現10.8-Gbps/16-m之點對點自由空間傳輸性能,接著以藍光雷射二極體搭配Lu3Al5O12:Ce3+ 與 CaAlSiN3:Eu2+ 共摻雜之螢光玻璃為基礎建構白光照明可見光通訊系統。當螢光玻璃之厚度為0.85-mm時,其所產生之白光色溫、色座標與最大照度分別為7856 K、(0.29, 0.3)和1337 lux。同時,照明白光內之殘留藍光成分對人眼可能造成之危害藉由計算其曝露限制來分析。在不對人眼造成危害前提下,可達1-m/2.8-Gbps 之傳輸性能。 接著,利用藍光雷射二極體建構以自來水與純海水為傳輸介質之水下光通訊系統。在以自來水為基礎時,其不同傳輸距離所對應的最大傳輸速率分別為12.4-Gbps/1.7-m、12-Gbps/3.4-m、9.6-Gbps/6.8-m與5.2-Gbps/10.2-m,同時可得傳輸容量隨距離之衰減率為0.847 Gbps/m。接著將自來水更換為純海水,由於海水內雜質引起的散射會導致藍光光束在傳輸中功率被衰減。因此,其傳輸容量對距離之衰減率會增加至0.941 Gbps/m,同時其在不同傳輸距離下所對應的最大傳輸速率分別為7.2-Gbps/6.8-m與4-Gbps/10.2-m。 最後,利用紅、藍及綠光雷射二極體來建構室內照明與通訊系統,並提供分波多工訊號傳輸。藉由此方式產生之白光色座標、色溫與最大照度分別為(0.2928, 0.2981)、8382 K與7520 lux。為了減少藍光對人眼之傷害,光學密度為0.3之光衰減片被使用使產生白光之色座標與色溫分別被改變至(0.2938, 0.3513)與7275 K。在尚未混成白光前,其紅、藍及綠光雷射二極體輸出光在1公尺自由空間傳輸後分別展現10.8、10.4與8 Gbps之最大傳輸速率。而在混成白光後,在0.5公尺自由空間傳輸下,可達總傳輸速率為5.2 Gbps。

並列摘要


Since visible light (wavelength ranging from 350 to 750 nm) communication (VLC) can extend the global high-speed network to specific space, its development of connecting all communication networks in human society is necessary. Using blue laser diode (LD) with higher modulation bandwidth and lower divergence than light emitting diode (LED) can not only enhance the VLC transmission performance but also further perform underwater communication. By further adhering phosphorous glass upon blue LD or mixing the red/green/blue (RGB) LDs, white-lighting source can also be provided. In this thesis, laser diode based free-space, underwater, and white-lighting visible light communication is proposed. Firstly, a 450-nm blue LD is used to perform 10.8-Gbps/16-m point-to-point VLC. Furthermore, the white-lighting VLC is constructed by adhering Lu3Al5O12:Ce3+ and CaAlSiN3:Eu2+ co-doped phosphorous glass upon 450-nm blue LD. The correlated color temperature (CCT), Commission International de l’Eclairage (CIE) and maximal illuminance value of white light generated by 0.85-mm phosphorous glass is 7856 K, (0.29, 0.3) and 1337 lux, respectively. In addition, the blue light damage of human eye is discussed by measuring the exposure limit. In addition, the white-lighting VLC with transmission data rate of 2.8 Gbps and free-space distance of 1 m is demonstrated without endangering human eyes. Moreover, the blue LD is also used to demonstrate the tap and pure ocean water based underwater optical wireless communication (UOWC) systems. For the tap water based UOWC system, the maximal allowable transmission capacities with corresponding underwater distances of 12.4-Gbps/1.7-m, 12-Gbps/3.4-m, 9.6-Gbps/6.8-m and 5.2-Gbps/10.2-m are demonstrated, which exhibits a distance related decay rate on capacity of 0.847 Gbps/m. When using the pure ocean water to replace the tap water, it inside impurities induced scattering would attenuate the blue laser power during underwater transmission. Therefore, a slightly high decay rate of 0.941 Gbps/m is observed for the pure ocean water based UOWC system, which achieves 7.2 Gbps for 6.8-m and 4 Gbps for 10.2-m. Finally, RGB LDs based indoor white-lighting communication is demonstrated for wavelength-division multiplexing (WDM) transmission. Before mixing the RGB LDs, the individual RGB LDs carried 16-QAM OFDM data exhibit maximal transmission data rate of 10.8, 10.4 and 8 Gbps at 1-m free-space transmission distance, respectively. After mixing the RGB laser light, the generated white light with CIE coordinate of (0.2928, 0.2981) and CCT of 8382 K exhibits a maximal illuminance of 7540 lux. To reduce the blue light hazard of human eyes, a filter with 0.3 optical density (OD) is adhered on the blue LD, and the CIE coordinate and CCT of RGB LDs generated white light are (0.2938, 0.3513) and 7275 K, respectively. Moreover, the indoor white-lighting WDM system reveals a total allowable transmission data rate of 5.2 Gbps with transmission distance of 0.5 m.

參考文獻


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