Proc. SPIE. 8845, Ultrafast Imaging and Spectroscopy
KEYWORDS: Visible radiation, Digital signal processing, Light emitting diodes, Data transmission, Multimedia, Data communications, System integration, Computer architecture, Systems modeling, Standards development
Visible light communication (VLC) technology has attained its attention in both academic and industry lately. It is determined by the development of light emitting diode (LED) technology for solid-state lighting (SSL).It has great potential to gradually replace radio frequency (RF) wireless technology because it offers unregulated and unlicensed bandwidth to withstand future demand of indoor wireless access to real–time bandwidth-demanding applications. However, it was found to provide intrusive uplink channel that give rise to unpleasant irradiance from the user device which could interfere with the downlink channel of VLC and hence limit mobility to users as a result of small coverage (field of view of VLC).To address this potential problem, a Hybrid VLC system which integrates VLC (for downlink) and RF (for uplink) technology is proposed. It offers a non-intrusive RF back channel that provides high throughput VLC and maintains durability with conventional RF devices. To deploy Hybrid VLC system in the market, it must be energy and cost saving to attain its equivalent economical advantage by comparing to existing architecture that employs fluorescent or LED lights with RF technology. In this paper, performance evaluation on the proposed hybrid system was carried out in terms of device cost and power consumption against data throughput. Based on our simulation, Hybrid VLC system was found to reduce device cost by 3% and power consumption by 68% when compares to fluorescent lights with RF technology. Nevertheless, when it is compared to LED lights with RF technology, our proposed hybrid system is found to achieve device cost saving as high as 47% and reduced power consumption by 49%. Such promising results have demonstrated that Hybrid VLC system is a feasible solution and has paved the way for greater cost saving and energy efficient compares with the current RF architecture even with the increasing requirement of indoor area coverage.
A thorough analysis on the separate confinement heterostructure (SCH) designed for 1.5-μm InGaAlAs/InP multiplequantum-
well (MQW) lasers is presented. Simulation results show that the enhancement rates of the threshold current
and the slope efficiency of graded-index SCH (GRINSCH) drop with the increasing number of graded layers. Hence,
requirement on truly graded structure may be relieved, which eases the growth process and reduces the cost. The
thickness of the GRINSCH has a profound impact on the laser's performance, whereby over 25 mA reduction in
threshold current was deducible by optimizing this design parameter alone. The grading energy range of the GRINSCH
is found to effectively reduce the carrier leakage at elevated temperature, resulting in improved threshold current's
sensitivity to the temperature. However, the increased GRINSCH energy barrier may also bring detrimental effect to the
slope efficiency. To overcome this problem, a non-symmetrical SCH (NS-SCH) structure with reduced n-SCH energy
barrier is proposed. Simulation results show that laser structure with NS-SCH design has better light-current performance
than the laser structure with electron stopper layer. The laser structure with NS-SCH exhibits 20% decrease in threshold
current and 43% increase of maximum output power as compared to those of the reference laser structure.