Analysis of Impact of Direct Current Bias on Optical Power Signal in VLC

Abstract

In visible light communications, adding direct current (DC) bias is the most common solution to the bipolar problem of signal, so that the precoding and optical orthogonal frequency division multiplexing (O-OFDM) can be performed. Moreover, it will be easier to achieve dimming control. In this paper, we analyze the impact of DC bias on optical power signal in the view of distribution, capacity and nonlinear distortion. Firstly, we classify the impacts of DC bias into two types depends on the total power, and derive their maximum entropy distributions. Then we investigate the capacity of two different channels with DC bias. Finally, we study the nonlinear distortion of power signal. Derivation and simulation results show that the capacity would decrease as the DC bias increases in most cases. The conclusions will help the consideration of DC bias in future system design.