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Title: | 藍/綠/紅三色雷射二極體混成白光之正交分頻多工通訊 Blue/Green/Red Tri-color Laser diode Mixed White-light OFDM Communication |
Authors: | Yu-Fang Huang 黃郁方 |
Advisor: | 黃定洧(Ding-Wei Huang) |
Co-Advisor: | 林恭如(Gong-Ru Lin) |
Keyword: | 雷射二極體,可見光通訊,正交分頻多工, laser diode,VLC,OFDM, |
Publication Year : | 2017 |
Degree: | 碩士 |
Abstract: | 近年來可見光(波長範圍380~780 nm)通訊發展越來越成熟,能夠在通訊的同時也具有白光照明功能,且由於沒有電磁波的干擾且傳輸速率高於傳統的Wi-Fi,其可以應用於某些特殊場合,如醫院及機舱。以發光二極體(LED)為光源所建構之可見光通訊現今已被運用於大賣場,將日光燈與手機應用成是結合,幫助顧客快速找到所需之產品。後來,具有較高調變頻寬與較小發散角的雷射二極體被提出作為替換光源,其能夠提高傳輸速率及通訊距離。而產生白光的方法有以藍光雷射二極體搭配黃色螢光片及同時混合紅光與綠光雷射二極體兩種。無論是哪一種方法,皆需要藍光雷射,其發光波段在水中具有較低衰減係數,適用於水下通訊。首先,優化完所有的最佳操作參數後,所使用之藍光雷射二極體可實現在距離為16 m的空氣中速度高達18 Gbps之點對點通訊。接著,將一個長為1.6 m之玻璃水箱注入海水(將海鹽溶水清水中,其比重為1.02,以模擬真實海水),以相同的實驗架構進行水下通訊,可達到速度為14.8 Gbps 1.7-m水下通訊。藉由五面反射鏡反射藍光雷射光束,可將傳輸距離拉長至10.2 m,除了長距離下海水所造成的吸收及散射外,光在空氣/玻璃/水介面折射及反射鏡反射時所造成的功率損失導致傳輸速度下降至10.8 Gbps。接著,將Lu3Al5O12:Ce3+ 與 CaAlSiN3:Eu2+ 共摻雜之螢光玻與紅/綠/藍光雷射二極體結合,透過適當調整三色光的功率比例及搭配厚度為1 mm之黃色螢光玻璃,混出色溫為6500K、演色性高達80之白光多工Li-Fi系統,其傳輸速度為6 Gbps。最後,將黃色螢光玻璃替換成散光板,以建構較高傳輸速度之白光照明與通訊系統,優化調變訊號的取樣率及選取適當的散光片,可達到速度為14 Gbps及傳輸距離為0.5 m之白光照明通訊。為了降低白光的色溫至6500K,利用光學密度為0.6的衰減片將藍光功率衰減,但同時也降低了藍光雷射之傳輸速度。成功展示色溫為6560K、色座標位於(0.31,0.35)之白光多工Li-Fi系統,同時提供速度為11.2 Gbps及照度>300 lux之照明功用。 Over the last few years, visible light (wavelength range of 380~780 nm) communication (VLC) has been well developed and become to be mature technology that provides function of white lighting while communicating. Moreover, without interference from electromagnetic and with higher transmission data rate than traditional Wi-Fi, it can therefore be applied in specific area, e.g. hospital and air craft cabin. The visible light communication which sourced from light emitting diode (LED) has already been utilized in for instance hypermarkets that daylight lamp and smart phones’ applications are combined to help customers find required goods quickly. Afterwards, laser diode, which has higher modulation bandwidth and smaller divergent angles, is proposed to be utilized as substitute light source for being able to enhance transmission data rate and communication distance. White light can be produced by combining blue light laser diode (BLD) and yellow phosphor or mixing red and green light laser diodes. Both mentioned methods require blue light laser, which with wavelength that exhibits the lowest attenuation coefficient in water environment and is suitable for underwater communication (UWC). First, after all the operated parameters being optimized, the blue light laser can achieve distance of 16 m with data rate of 18 Gbps point to-point VLC in the air. Subsequently, with the same experiment construction yet in a 16-m glass container filled with seawater (sea salt dissolved in the fresh water that with resulted gravity of 1.02 to simulate real seawater) to conduct underwater communication, transmission data rate of 14.8 Gbps 1.7-m underwater communication can be achieved. While the blue laser beam is reflected by 5 reflective mirrors, the transmission distance can be extended to be 10.2 m. Except absorbing and scatter of seawater in long distance, power ratio loss from the light refraction at air/glass/water interface and reflection of reflective mirror also induce transmission data rate to decrease to 10.8 Gbps. Afterward, with combination of the phosphorous glass that adhering Lu3Al5O12:Ce3+ and CaAlSiN3:Eu2+ and red/green/blue (RGB) light laser diodes, the three-color light with fine-adjusted power ratio percentage together with 1-mm-thick yellow phosphorous glass are used to construct white light WDM Li-Fi system with correlated color temperature (CCT) of 6500 K and (color rendering index) CRI of 80, it in consequence has transmission data rate of 6 Gbps. At last, the yellow phosphorous glass is replaced by diffuser in order to construct white lighting and communication system with higher transmission data rate. By optimizing sampling rate of signal and using proper diffuser, the white light communication with transmission data rate of 14 Gbps and transmission distance of 0.5 m can be carried out. To lower CCT of the white light to be 6500 K, optical density (O.D.) filter with O.D. of 0.6 is used to attenuate the blue light power ratio, which nevertheless lowers transmission rate of the blue light in the meantime. The white light wavelength division multiplexing (WDM) Li-Fi system that with CCT of 6560K and Commission International de l’Eclairage (CIE) coordinate of (0.31, 0.35) eventually provides transmission data rate of 11.2 Gpbs and lighting function with illuminance of > 300 lux. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/77695 |
DOI: | 10.6342/NTU201703468 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 光電工程學研究所 |
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ntu-106-R04941034-1.pdf Restricted Access | 4.54 MB | Adobe PDF |
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