Laser Diode Mixed White-Lighting for Indoor and Vehicle Communications

• Main Authors: Chia-Yu Su, 蘇家郁
• Other Authors: Gong-Ru Lin
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/482cs6

碩士 === 國立臺灣大學 === 光電工程學研究所 === 107 === Currently, visible light (wavelength ranging from 380 to 780 nm) communication (VLC) is a state-of-the-art technology of wireless communication, which can provide lighting and high-speed communication at the same time, and can be applied in numerous scenarios that range scale from indoor VLC all the way to vehicle communication and underwater wireless optical communication (UWOC) because of several key advantages, including ultrafast data rate, huge unregulated bandwidth, higher data security, and non-electromagnetic interference. At early stage, LED is the first choice to serve as a light source of VLC system because it can offer outstanding lighting performance. Nonetheless, its transmission performance is seriously limited by its narrow modulation bandwidth. Therefore, laser diode (LD) with higher brightness and broader modulation bandwidth becomes a potential alternatively candidate for the light sources to greatly upgrade the extreme data rate of the VLC system. For white-lighting generation, there are two typical ways, including adhering blue/violet LD with versatile phosphorous material for color conversion and combining red/green/blue (violet) LD to mix white light source. In this thesis, a high-speed violet LD with the BBEHP/MEH polymer phosphor based white-lighting VLC for indoor lighting communication and a miniaturized high-power red/green/violet (RGV) mixed white-lighting VLC module for vehicle communication is proposed. . First, in order to obtain the high-speed violet LD, three packaging method of the VLD has been discussed, and found that shortened the length of laser pin to improve the frequency response is the best choice to obtain the maximal modulation bandwidth of the TO-can laser diode, which enables the maximal 16-quadrature amplitude modulation orthogonal frequency division multiplexing (16-QAM OFDM) transmission data rate as high as 20.4 Gbit/s with a FEC qualified BER of 3.3×10-3. Based on the concept, the comparison of the transmission characteristics for different rated power VLD is also revealed. And the extreme modulation bandwidth for the 16-QAM OFDM encoded 150 mW, 250 mW and 500 mW VLD of 5.1-GHz, 4.6-GHz and 2.2-GHz is obtained, respectively, which concluded a linear decay slope of - 0.046 Gbps /mW to describe the relation between the output power and the extreme data rate. Afterward, the violet LD with an ultrafast color convertor BBEHP/MEH polymer phosphor based white-lighting VLC system is demonstrated. After adhering the BBEHP/MEH polymer phosphor in front of the violet LD to produce white-light, it demonstrates a qualified light source with correlated color temperature (CCT) of 3606 K, a color rendering index (CRI) of 84.6 and a CIE coordinate at (0.3768, 0.3226), which is a suitable light source for indoor lighting. Moreover, owing to the ultrafast lifetime of the BBEHP/MEH polymer phosphor is as short as 8.8 ns, the maximal 16-QAM OFDM transmission data rate can reach as high as 12.8 Gbit/s with the BER at 3.37×10-3, which is below the forward error correction criterion. Finally, a miniaturized high-power red/green/violet (RGV) LDs and a high-power yellow light emitting diode (LED) mixed white-lighting VLC module for vehicle communication is demonstrated. Comparing to the bulky optomechanic module architected with typical design, the size of the miniaturized R/G/V/Y module greatly reduces the volume by more than 310 times with W×L×H = 6×5.4×2 cm3. The R/G/V LDs are individually delivered 16-QAM OFDM data to reach the extreme data rate of 8.8 Gbit/s, 5.2 Gbit/s and 7.2 Gbit/s with the total data rate as high as 21.2 Gbit/s. Moreover, the output power of the R/G/V LDs under the optimized bias currents are 102/97/129 mW, respectively, which can provide a high illuminance of 12800 lux with a divergent angle of 54o at a distance of 0.5 m. And the high-power R/G/V/Y mixed white-lighting source exhibits a qualified CRI of 60.7, a CCT of 5176 K at CIE coordinate of (0.3461, 0.4424), which can satisfy the requirements of serving as a car headlight for vehicle communication.