本論文主旨為可見光通訊之發光二極體光源分析及實現傳輸系統。將此技術應用在室內照明系統上，使原有的燈具不僅作為照明之用途，亦可發展為無線光通訊，並且傳輸速率在Mbit/s等級以上，達到室內照明應用之目的。而本實驗的發射端設計以直徑長55 mm之透鏡，增加光檢測器接收的光功率；並在接收端設計以直徑長30 mm之透鏡，優化其光檢測器的耦合效率；而光訊號經由光檢測器轉為電訊號後，設計串階運算放大電路將其電流訊號作放大，進而得到所需的訊號。其本論文架構是使用白光發光二極體作為通訊光源，由於白光發光二極體的混光技術是使用藍光發光二極體晶片激發黃色螢光粉之技術，故在通訊時隨著調變訊號速率提升，造成黃色螢光粉被激發的轉換速率不及藍光調變訊號之速率，經由實驗得到驗證其白光發光二極體傳輸速率被侷限在3 Mbit/s左右。由於白光發光二極體在傳輸上有頻寬受限的問題，所以改用單色光藍光取代白光發光二極體作為通訊光源，其原理是以前述白光發光二極體作為可見光通系統訊光源，但在接收器前加入藍光濾波器，使光檢測器接收單純的藍光訊號。經由實驗可得藍光發光二極體可見光通訊系統，在傳輸距離2.5 m時，其最高的傳輸速率為7 Mbit/s，接收光功率為-21.1 dBm。並且比較白光與藍光發光二極體之系統眼圖的實驗量測，觀察在相同傳輸速率2 Mbit/s時，其眼開度以藍光優於白光發光二極體之系統架構。而同時在系統中，加入直徑長55 mm之透鏡，使耦合效率優化0.8 V。由紅光、藍光、綠光發光二極體的光源進行傳輸實驗，得到藍光在最高的傳輸速率時，其光檢測器所接收之光功率較佳，由此證實紅光、藍光、綠光的發光二極體在室內光通訊中，以藍光發光二極體為光源首選。

In the thesis, LED plays a role in visible light communication as well as indoor lighting. The transmission speed could be upgraded to few Mbps per LED chip. In our experiment, the transmitter path is optimized by using a convergent focal lens with diameter of 55 mm, while the receiver may couple much LED power by using a divergent lens with focal length of 30 mm. In order to acquire sufficient signal power, operational amplifiers are used to improve the sensitivity of photodiode.
The white LED used in this experiment is based on mixed light technology using a blue LED chip with phosphor emitting yellow light, so that the white LED VLC could transmit only at about 3Mbit/s due to its low response time. To increase the LED bandwidth and improve the response time, a blue light LED may be obtained by putting a blue-color filter in front of the receivers to filter out the other colors of this white light LED. Thus, only the blue light spectrum is remained. In the experiment, the blue LED communication system at distance 2.5 m, its transmitted rates is up to 7 Mbit/s at a received power of -21.1 dBm. In the same modulation speed of 2Mbit/s, we compare the eye diagrams performance of white light LED with blue light LED and find that the latter one has better performance thanks to its broader bandwidth. A further 0.8 V amplitude is increased when a convergent lens with diameter of 55 mm is added in front of the receiver. These experiences confirm that the blue light LED has better performance than those LEDs of other wavelength ranges.

參考文獻
[1] A. Paulraj, R. Nabar and D. Gore, “Introduction to space-time wireless communications,” United Kingdom, Cambridge: Cambridge University Press, 2003.
[2] M. Kavehrad, (2010, Dec. 23). Sustainable energy-efficient wireless applications using light. IEEE Communications Magazine. pp. 66-73.
[3] K. Wang, A. Nirmalathas, C. Lim and E. Skafidas, “High-speed duplex optical wireless communication system for indoor personal area networks,” Optics Express, vol. 18, no. 24, pp. 25199-25216, 2010.
[4] J. Granado, A. Torralba and J. Chávez, “Using broadband power line communications in non-conventional applications,” IEEE Transactions on Consumer Electronics, vol. 57, no. 3, pp. 1092-1098, 2011.
[5] J. Vuc ̌ic ́, C. Kottke, S. Nerreter, A. Buttner, K.-D. Langer and J.-W. Waleaski, “White light wireless transmission at 200+ Mb/s net data rate by use of discrete-multitone modulation,” IEEE Photonics Technology Letters, vol. 21, no. 20, pp. 1511-1513, 2009.
[6] G. Ntogari, T. Kamalakis, J. Walewski and T. Sphicopoulos, “Combining illumination dimming based on pulse-width modulation with visible-light communications based on discrete multitone,” IEEE/OSA Journal of Optical Communications and Networking, vol. 3, no. 1, pp. 56-65, 2011.
[7] A.-G. Al-Ghamdi and J.-M.-H. Elmirghani, “Spot diffusing technique and angle diversity performance for high speed indoor diffuse infra-red wireless transmission,” IEE Proceedings Optoelectronics, vol. 151, no. 1, pp. 46-52, 2004.
[8] X. Liu, H. Makino and K. Mase, “Improved indoor location estimation using fluorescent light communication system with a nine-channel receiver,” Journal of the Institute of Electronics, Information and Communication Engineers, vol. E93–B, no. 11, pp. 2936-2944, 2010.
[9] T. Komine and M. Nakagawa, “Integrated system of white LED visible-light communication and power-line communication,” IEEE Transactions on Consumer Electronics, vol. 49, no. 1, pp. 71-79, 2003.
[10] Z. Wang, C. Yu, W.-D. Zhong, J. Chen and W. Chen, “Performance of a novel LED lamp arrangement to reduce SNR fluctuation for multi-user visible light communication systems,” Optics Express, vol. 20, no. 4, pp. 4564-4573, 2012.
[11] W.-Y. Lin, C.-Y. Chen, H.-H. Lu, C.-H. Chang, Y.-P. Lin, H.-C. Lin and H.-W Wu, “10m/500Mbps WDM visible light communication systems,” Optics Express, vol. 20, no. 9, pp. 9919-9924, 2012.
[12] S. Rajbhandari, Z. Ghassemlooy and M. Angelova, “Experimental investigation of wavelet-based denoising receiver for LOS indoor optical wireless communications links,” IEEE Photonics Technology Letters, vol. 23, no. 20, pp. 1502-1504, 2011.
[13] J. Rufo, J. Rabadan, F. Delgado, C. Quintana and R. Perez-Jimenez, “Experimental evaluation of video transmission through LED illumination devices,” IEEE Transactions on Consumer Electronics, vol. 56, no. 3, pp. 1411–1416, 2010.
[14] I.-E. Lee, M.-L. Sim and F.-W.-L. Kung, “Performance enhancement of outdoor visible light communication system using selective combining receiver,” Journal of the Institution of Engineering and Technology Optoelectronics, vol. 3, no. 1, pp. 30-39, 2009.
[15] M. Akanegawa, Y. Tanaka and M. Nakagawa, “Basic study on traffic information system using LED traffic lights,” IEEE Transactions on Intelligent Transportation Systems, vol. 2, no. 4, pp. 197–203, 2001.
[16] E.-F. Schuber, “Light emitting diodes,” 2nd ed. New York: Cambridge University Press, 2006.
[17] D.-A. Neamen, “Semiconductor physics and devices,” 4nd ed. New York: McGraw-Hill, 2012.
[18] S. Muthu﹐ F.-J. Schuurmans and M.-D. Pashley, “Red, green and blue LED based white light generation: issues and control,” in Proc. IEEE Industry Applications Conference﹐IAS’02, vol. 1, Pittsburgh, USA, Oct. 2002, pp. 327-333.
[19] 黃建歷，“高功率白光LED照明之光學設計”，國立台灣科技大學碩士論文，2009年7月。
[20] 陳建安，“高功率白光發光二極體之混光設計優化和光學設計”，國立台灣科技大學碩士論文，2007年6月。
[21] J.-K. Sheu, S.-J. Chang, C.-H. Kuo, Y.-K. Su, L.-W. Wu, Y.-C. Lin, W.-C. Lai, J.-M. Tsai, G.-C. Chi and R.-K. Wu, “White-light emission from near UV InGaN–GaN LED chip precoated with blue/green/red phosphors,” IEEE Photonics Technology Letters, vol. 15, no. 1, pp. 18-20, 2003.
[22] K.-D. Langer and J. Gubor, “Recent developments in optical wireless communications using infrared and visible light,” in Proc. International Conference on Transparent Optical Network, ICTON’07, vol. 3, Rome, Italy, Jul. 2007, pp. 146-151.
[23] D.-C. O’Brien, M. Katz, P. Wang, K. Kalliojarvi, S. Arnon, M. Matsumoto, R. Green and S. Jivkova, “Short-range optical wireless communications,” in Proc. Wireless World Research Forum, 2005.
[24] R.-J. Green, H. Joshi, M.-D. Higgins and M.-S. Leeson, “Recent developments in indoor optical wireless [optical wireless communications],” Journal of the Institution of Engineering and Technology Communications, vol. 2, no. 1, pp. 3-10, 2008.
[25] J. Vučić, C. Kottke, S. Nerreter, K.-D. Langer and J.-W. Walewski, “513 Mbit/s visible light communications link based on DMT-modulation of a white LED,” Journal of Lightwave Technology, vol. 28, no. 24, pp. 3512-3518, 2010.
[26] 呂宛蒨，“160 Gbit/s雙向分波多工之無線光通訊設計與系統傳輸”，國立台灣科技大學碩士論文，2011年6月。
[27] Thorlabs COM., “FDS100,” http://www.thorlabs.hk/index.cfm, 2011.
[28] 萊普士光電科技有限公司，“光學積分球”，http://www.lightports.com，2009。
[29] 胡國瑞，孫沛立，徐道義，陳鴻興，黃日鋒，詹文鑫，羅梅君，“顯示色彩工程學”，全華科技圖書，台北，第5章， 2009。
[30] 陳鴻興，陳詩涵 譯，“色彩工程學理論與應用”，全華科技圖書，台北，第6章，2007。
[31] D.-B. Judd, “The 1931 I. C. I. standard observer and coordinate system for colorimetry,” Journal of the Optical Society of America, vol. 23, no. 10, pp. 359-373, 1933.
[32] 日本照明學會 編，“照明手冊”，全華圖書科技，台北，第1章，2006。
[33] L.-M. Hoa, D.-C. O’Brien, G. Faulkner, L. Zeng, K. Lee, D. Jung and Y. Oh, “High-speed visible light communications using multiple-resonant equalization,” IEEE Photonics Technology Letters, vol. 20, no. 14, pp. 1243-1245, 2008.
[34] L. Zeng, D.-C. O’Brien, H.-L. Minh, G. Faulkner, K. Lee, D. Jung, Y. Oh and E.-T. Won, “High data rate multiple input multiple output (MIMO) optical wireless communications using white LED lighting,” IEEE Journal on Selected Areas in Communications, vol. 27, no. 9, pp. 1654-1662, 2009.
[35] Tektronix COM., “TDS2022B,” http://www.tek.com, 2006.
[36] S.-Y. Jung, S. Hann and C.-S. Park, “TDOA-based optical wireless indoor localization using LED ceiling lamps,” IEEE Transactions on Consumer Electronics, vol. 57, no. 4, pp. 1592-1597, 2011.