A HIGH-PERFORMANCE BLUE FILTER FOR A WHITE-LED-BASED VISIBLE LIGHT COMMUNICATION SYSTEM

A high-performance blue filter was demonstrated and employed to increase the modulation bandwidth and dramatically reduce the bit error rate of a white-LED-based VLC system. It has a very wide stopband (500-1050 nm), high transmittance passband (average 97.5 percent in the blue signal range of 430-485 nm), and a sharp and precise cutoff edge. Not only can the blue filter completely remove the slow phosphorescent component from modulated signals, but it can also effectively reject ambient solar radiation. Meanwhile, the blue light signals of the LED can almost be retained. This results in a high SNR and improves the performance of a VLC system, including increased modulation bandwidth and reduced BER. The BER can be dramatically reduced from 3.6 x 10(-2) to 1.7 x 10(-4) at 50 MHz bandwidth, and from 2.6 x 10(-2) to 1.9 x 10(-5) at a distance of 30 cm compared to a VLC system without our blue filter. More importantly, the stop band covers the whole response range of the receiver except for the blue signal band, which strongly increases the ability of a VLC system used in the sun or outdoors.