The most important wavelengths in the telecommunications industry are 1310 nm and 1550 nm, and an attenuator is placed between the light source and the power meter to set the power to the appropriate level. The difference between these two power levels is the loss of the cable plant which can be tested as described above. The basic process is straightforward: turn the meter on, set it to the correct wavelength, clean your connectors, plug in, and read the. Select Wavelength: Use the wavelength selection feature to set the wavelength corresponding to the fiber optic system under test. This is typically done through a menu or a dedicated button. This paper describes the measurement standards, techniques, systems, and.