An optical power meter is a test device that measures the strength of light traveling through a fiber optic system. In fiber testing, the result is usually displayed as dBm for absolute optical power or dB for relative loss. Industry guidance commonly describes dBm as power referenced to 1. How to Maintain Your Optical Power Meter for Longevity? 6. The basic process is straightforward: turn the meter on, set it to the correct wavelength, clean your connectors, plug in, and read the. Optical power meters are a key element in the optimization and maintenance of such optical networks and of their components.