Analysis of the effect of photodetector filter bandwidth and optical preamplifier gain on the performance of high-power LED 16 QAM-OFDM VLC system

Commercial phosphorous light emitting diodes (PLEDs) have many impairments such as slow response, low bandwidth (BW), and signal attenuation which limit the performance of VLC systems. In our previous work, we proposed an efficient 16 QAM link integrating an optical preamplifier with a PLED. We successfully demonstrated the transmission of 0.5 Gbps over a VLC link of 7 m range. In this work, we have further modified the 16 QAM system and upgraded it to 16 QAM-OFDM employing an optical preamplifier and a bandpass filter (BPF) after the photodetector. The effect of the preamplifier gain and the BPF bandwidth on the performance of the 16 QAM-OFDM system have been investigated. The results showed that a BPF with BW of 375 MHz offers an optimum performance of the system at a data rate of 1 Gbps. A minimum Log of BER of -3.515 is achieved. The effect of the optical preamplifier gain on the link performance is also investigated. When the gain is 15 dB, the distance is restricted to 1.5 m only when considered SFEC limit. However, when the gain is 20 dB a maximum distance up to 3 m is achieved while considering SFEC limit.\\ The BPF optimized bandwidth of 375 MHz, and the preamplifier gain of 20 dB are used successfully to transmit a data rate of 6 Gbps for distance of 1.5 m while considering the SFEC limit. When the data rate is incresead to 7 Gbps, the link range is abruptly decreased to 0.5 m.