In real life, because of the speed of light, we develop light for information transmission.
Just like we usually use voice to communicate, if a person wants to speak, they need the support of vocal organ tissue. For example, our throat is one of the most important vocal organs, and of course, the vocal cord tissue inside our throat is the most important.
Similarly, if we want to use light to help us speak, we also need a luminous organ. The light module is like a throat, and a luminous device can be compared to vocal cord tissue, called tosa.
Of course, communication is an interactive process, so in addition to speaking, it is not enough, but also necessary to be able to listen. In the human body, we have ears to help us listen. Similarly, in optical communication, we have modules that receive light. The devices that can receive light correspond to the tympanum inside the ear, which we call rosa. A device that can both speak and listen is called a bosa.
However, in real life, what sounds we individuals can make is basically determined after birth or after the sound change period. Generally, A cannot make the sound of B, and B is not very able to make the sound of A. The same is true for optical modules. For a single mode, module A cannot emit the wavelength of module B. The same is true for reception. For a single mode, the optical module cannot distinguish. You must tell him who is speaking (using the module corresponding to the wavelength of the light) before he can receive the information.
“Such a stupid module cannot meet practical needs, so we can compensate for this by using an optical module that can be easily plugged in and out. At this point, the optical module is equivalent to a sound transformer, and you can make any sound (which wavelength) you want it to emit.”.