中文摘要：

LED作为可见光通信（VLC）的发射光源时为保证足够大的光信号覆盖范围和信号强度，应采用大电流脉冲调制。本文研究了大功率LED的光-电脉冲响应比小功率器件较慢、从而造成光调制带宽降低的原因，以及LED注入电子和空穴的缓慢复合与驱动电路晶体管在大电流工作时的存储效应；由此设计了FPGA控制下的光脉冲整形方案，信号脉冲经由FPGA再生同时产生另外两路相位关联的短脉冲，同步控制驱动电路分别在信号脉冲上升沿施加一个瞬时高压加速载流子注入，在脉冲下降沿使LED两端短路将剩余载流子泄放，使光脉冲边沿加速进行整形。对接收信号的眼图和误码率（BER）的测试结果表明，在接近安培量级的峰一峰值调制电流下，通过这种同步控制方法使光信号质量得到有效改善，传输速率得到明显提高。

英文摘要：

Light emitting diodes （LEDs） can be used as the light sources for wireless optical communication,which are expected to be developed into optical local area network. In terms of a specific transmission speed requirement, large current modulation should be adopted to ensure large area of signal coverage and signal intensity. In this paper,the mechanisms of the slower photo-electric response and smaller optical modulation bandwidth of the high power LEDs than those of the lower power ones are investigated. The slow recombination of the electrons/holes injected into the LED and the carrier storage effect of the transistor in the driving circuit are analyzed. The optical pulse shaping technique is selected to promote the transmission speed. FPGA is used to generate the two outputs of additional short pulses with their phases correlated to the signal pulses regenerated by the FPGA. The two pulses synchronously control a driving circuit to apply a transient over-voltage at the pulse rising edge to speed up the carrier injection,and a short circuit to the LED at the pulse falling edge discharging the remaining carriers. The measurement results of eye-diagram and bit error rate （BER） of the received signals demonstrate that the optical signal quality and the transmission rate are significantly improved,at the nearly ampere level of the peak-peak modulating current.