The operating wavelength of single-mode optical modules is generally 1310nm or 1550nm. In fiber-optic communication, a single-mode optical fiber, also known as fundamental- or mono-mode, is an optical fiber designed to carry only a single mode of light - the transverse mode. Modes are the possible solutions of the Helmholtz equation for waves, which is obtained by combining. SMF SFP primarily operates at wavelengths of 1310 nanometers and 1550 nanometers. Therefore, it is suitable for long-distance data transmission applications such as 2 kilometers, 10 kilometers, 40 kilometers, 60 kilometers, 80 kilometers, and 120 kilometers.