An optical power meter (OPM) is a type of electronic test device used to measure the power output of fiber optic equipment or the power or loss of an optical signal transmitted through a fiber cable. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power. This article provides a comprehensive overview of optical power meters, instruments used to measure the power of light beams. It helps engineers verify the performance of optical fiber systems, ensuring that the signal strength meets requirements, and is an essential tool for communication network maintenance and troubleshooting. An OPM uses a photodiode to generate an electrical current proportional to optical power.