Efficient optical filtering for outdoor visible light communications in the presence of sunlight or articifical light

An efficient optical filtering method for blocking outdoor light noise at visible light communication (VLC) systems has been presented. Unlike spread spectrum techniques or combining methods previously reported, the proposed method is very practical and efficient in that it uses an optical filter on the top of the photo diode to block obliquely incident unwanted lights, under the realistic assumption that light noise does not come into the photo diode directly. The experimental system demonstrates that the optical filtering method blocks nearly all light noise incident from an angle of 30° or higher. A simple pulse transmission over the VLC link also verifies the filter´s blocking capability.