The optical power meter usually reads in dBm for power measurements or dB with respect to a user-set reference value for loss. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power. Every fiber optic power meter is calibrated traceable to the NIST standard, ensuring consistency among different meters within calibration uncertainty limits. Optical power in fiber optics is akin to the heating power of a light bulb but at significantly lower power levels. It's very useful in many jobs, especially in communications, fiber optics, andelectronics.