Currently, there are three types of center wavelengths for commonly used optical modules: 850 nm, 1310 nm, and 1550 nm. Why are they defined in these three bands? This is related to the fiber loss of the optical signal transmission medium. Its main function is to convert. The optical module serves as a crucial component in optical fiber communication systems, operating at the physical layer, which is the lowest layer in the OSI model. Commonly used wavelengths include 850nm, 1310nm, and 1550nm, as well as the CWDM wavelengths ranging from 1270nm to 1610nm. The wavelength range used in optical communication is 850 ~ 1650 nm, and the optical module emits “color light” or “white light”, which are invisible to human eyes.