This lecture covers the application of Poisson processes to the signal-to-noise ratio of a photodetector in communication systems, discussing stochastic models for wireless and optical channels, the impact of Gaussian white noise, photon arrival processes, dark current, thermal noise, and the efficiency of a photodiode. The lecture also delves into the conversion of optical signals to electrical currents, the generation of current incidents, and the decision-making process based on threshold values. The instructor explains the concept of Poisson processes, the relationship between signal and noise, and the calculation of the signal-to-noise ratio using theoretical frameworks like the Campbell theorem.