An investigation on the application solution of light emitting diodes for improving the working bandwidth in visible light communication

Visible light communication (VLC) has attracted attention due to its promising future. However, the low bandwidth of the light source leads to the relatively low communication rate. In this work, a measurement platform mainly consisted of signal source and oscilloscope is established to measure the 3-dB modulation bandwidth of LED. Experiments are conducted to investigate the influences of the LED’s working current, distribution of LED array, and LED’s driving circuit on the working bandwidth of the VLC system. When the LED driving current increases from 22 mA to 32 mA, the corresponding 3-Db bandwidth of the blue LED is improved from 1.8 MHz to 2.3 MHz. Designing blue LED array with the controlled internal distance between the neighboring LEDs aimed at improving the overall working bandwidth of the commercial light sources. The 3-Db bandwidth of a single blue LED is 1.8 M under the working current of 20 mA. The 3- dB bandwidth of the 2×2 blue LED array in series is 2.9 M under the working current of 20 mA with the optimized internal distance of 10 mm. Under the same measurement conditions, the 3-Db bandwidth of 1×2 blue LEDs in parallel is improved from 1.8 M to 2.9 M after adding the as-designed LED driving circuit.