Investigation of power LEDs response time in visible light communications

With the emergence of LEDs, the conventional incandescent or fluorescent lighting solutions tends to be replaced by LED lighting systems. Historically, the lighting system was invented before radio communications, therefore its infrastructure is more widespread and simpler. One property of the conventional lighting sources is that the optical radiation emitted by them cannot be switched on and off fast. In the latest trends in high-speed communication, LED lighting solutions are used to transfer data. This field is known as Visible Light Communications (VLC). In previous work, the authors investigated the available bandwidth of four power LEDs¹ that could be used for VLC systems. A typical low pass filter cutoff frequency identification procedure was used. For a complete characterization, the authors propose to determine the available bandwidth by investigating the switch-on time. The paper investigates the response time of power LEDs by studying four different LEDs: green, red, infrared and white. The LED driver circuit was especially designed for this application because it required very fast switch-on time.