Commonly, a power meter on its own is used to measure absolute optical power, or used with a matched light source to measure loss. The term usually refers to a device for testing average power in fiber optic systems. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power meters (can be. Optical power meters are a key element in the optimization and maintenance of such optical networks and of their components. In this article, learn: What is an optical power meter? An optical power meter (OPM) measures the power levels of light signals in devices that transmit data or power using. In optical fiber networks, the units of optical power are often expressed in milliwatts (mw) and decibel milliwatts (dbm). The relationship is: 1mw=0dbm, that is to say, 2mw=3dbm, 10*lgmw is the dbm value. In addition to. In this blog, we'll explore what a power meter and light source are and provide a simple, step-by-step guide on how to perform loss testing accurately.