Fig. 1. Path loss with changes in rainfall intensity measured at wavelengths of 405, 450, 520, and 650 nm in the visible light range based on LDs: light rain (<2.5 mm/h), moderate rain (2.5–10 mm/h), and heavy rain (10–30 mm/h).

Fig. 2. Experimental setup (including the transmitter side, channel, and receiver side) and process diagram of a VLC system based on a laser in the rainy environment channel of 3.38 m.

Fig. 3. (a) The I-V and P-I curves of four wavelength lasers. (b) The −3 dB bandwidths of four wavelength lasers.

Fig. 4. The frequency spectrum using adaptive pre-equalization coefficient in different channel environments at (a) free space, (b) light rainfall, (c) moderate rainfall, and (d) heavy rainfall.

Fig. 5. SNR and bit numbers based on the adaptive OFDM bit-loading algorithm using different SNR gaps in different channel environments at (a) free space, (b) light rainfall, (c) moderate rainfall, and (d) heavy rainfall.

Fig. 6. BERs and data rates of various wavelength LDs in free space, heavy, moderate, and light rainfall conditions at (a) 405, (b) 450, (c) 520, and (d) 650 nm.