Optical power is measured in linear units of milliwatts (mW), microwatts (uW - really the greek letter "mu"W), nanowatts (nW) and decibels (dB). What is the difference between "dBm" and "dB"? dB is a ratio of two powers, for example the loss in a fiber optic cable. In essence, it helps engineers and technicians assess the fiber optic link's quality by measuring the light's signal strength in microwatts. An optical power meter (OPM) is a device used to measure the power in an optical signal.
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