What are the Main Factors Affecting the Fiber Loss?

In transmission, the optical loss is mainly depending on the wavelength of the transmitted light and the use of the type of optic fiber cable.
850nm wavelength for multimode fiber: 3.0 dB / km
1310nm wavelength for multimode fiber: 1.0 dB / km
1310nm wavelength for single-mode fiber: 0.4 dB / km
1550nm wavelength for single-mode fiber: 0.2 dB / km