In-Situ Monitoring the Degradation of LEDs En Route the Visible Light Communication System

摘要

White light-emitting diodes (LEDs) offer the opportunity to realize energy efficient illumination and high-speed free-space visible light communication (VLC) simultaneously. The decrease of the optical power (OP) was usually used to characterize the degradation of LEDs, but the degradation does not always and only refers to a decrease in OP. This paper proposes using the characteristics parameters of VLC performances as in-situ indicators of the degradation of the LED light source itself. LED devices being intentionally stressed for 168 h at 120 °C and 85% relative humidity and 350 mA are used for demonstration. Stressing generates new defects in LED chips, which is accompanied by the decrease of frequency-response bandwidth and bit-error rate values of LEDs at the rated voltages. Compared with low-frequency light intensity noise characterization methods, the VLC system is something like to measure a dimming optical noise, featured by free-space measurement and compatibility with the existing illumination and wireless communication system.