Optical communication applications based on white LEDs

In this paper is proposed an indoor navigation system based on the use of Visible Light Communication (VLC) technology. The proposed system includes tri-chromatic white LEDs with the red and blue chips modulated at different frequencies and a pinpin photodetector with selective spectral sensitivity. The optoelectronic properties of the optical sources and photodetector device are analyzed. The photodetector device consists two pin structures based on a-SiC:H and a-Si:H with geometrical configuration optimized for the detection of short and large wavelengths in the visible range. Its sensitivity is externally tuned by steady state optical bias. The localization algorithm makes use of the Fourier transform to identify the frequencies present in the photocurrent signal and the wavelength filtering properties of the sensor under front and back optical bias to detect the existing red and blue signals. The viability of the system is demonstrated through the implementation of an automatic algorithm to infer the photodetector cardinal direction.