I also want to mention that in the WDM-based access, the bandwidth demand has increased rapidly; thus, it is a potential solution for future data transport with regard to all optical wide area networks . In fiber optics communication, WDM is well known and used extensively. Several single-beam FSO WDM transmission systems have been successfully demonstrated where the different wavelengths are carried by one beam. Even though more than one wavelength is used to increase the data rate, after all, this system lies under a single-beam attenuation affect. In the current study, the performance and applicability of the four-beam FSO system in rainy weather are proposed and investigated using WDM. The study is conducted based on simulation using on-site attenuation and rain intensity measurements. It considers the received power, geometrical losses, and atmospheric losses due to heavy rain.
I hope this is helpful to you
Regards