An optical power meter measures the strength of light traveling through a fiber optic cable, giving you a reading in dBm (decibels relative to one milliwatt). To use an optical power meter correctly, you need to select the right wavelength, connect the detector or fiber adapter, choose a suitable. An optical power meter (OPM) is a device used to measure the power in an optical signal. TIA standard test FOTP-95 covers the measurement of optical power. The basic process is straightforward: turn the meter on, set it to the correct wavelength, clean your connectors, plug in, and read the.