On the performance of digital to analog conversion in the optical domain

Optical domain digital to analog conversion (ODAC) has been proposed recently as a suitable technique able to cope with LED driving requirements and evolved modulation schemes (such as OFDM) in visible light communication systems (VLC). ODAC´s concept is based on using groups of LEDs arranged in an array to transmit digital signals. The radiation pattern of these LED groups adds together on the optical domain enabling the transmission of complex signals. Since the LED driving signals are digital signals, both constant current and PWM dimming requirements can be adequately met. This paper addresses the analysis of ODAC error performance over a predefined area. The analysis framework consisted of a multipath communication scenario with a single reflection. In order to better understand the effects due to reflections, the analysis considered low data rate communication systems, thus enabling to neglect the channel input response. Major conclusions ascertain that the effects of LED array arrangement are apparent under near field conditions and that the root mean square error approaches its ideal value, given by LSB/2 as the distance from the source increases.