An optical power meter works by converting incoming optical energy into an electrical measurement through a photodiode detector. The detector senses the light level, and the meter displays the result in the selected unit. Newport's 1936/2936-R Series Optical Power Meters are among the most versatile power meters in the market, and the. An optical power meter (OPM) is a device used to measure the power in an optical signal. Industry guidance commonly describes dBm as power referenced to 1.