The 100GHz or 50GHz interval here corresponds to the relevant wavelength. The optical fiber has two long-wavelength low-loss windows, the 1310nm window and the 1550nm window, both of which can be used for optical signal transmission, but because the commonly used erbium-doped fiber amplifiers work in the wavelength range of 192.1 to 196.1 THz. Just around the 1550nm window.

Therefore, the operating wavelength region of the optical wavelength division multiplexing system is 192.1 ~ 196.1 THz. For details, refer to ITU-T G.692 regulations. Generally, C-band or L-band is most commonly used.