Optical communication is any type of communication in which light is used to carry the signal to the remote end, instead of electrical current. The transmitted information is firstly converted into an electrical signal in the transmitting end, and then the electrical signal is modulated onto the laser beam emitted by the light source, so that the light intensity changes with the frequency of electrical signal. Based on the principle of total internal reflection, the light signal is transmitted in optical fiber. https://www.glsun.com/article-p105-what-is-optical-communication.html