The optical power meter is similar to the voltohmmeter in application but measures the optical resistance (losses measured in dBm or dBM) of a cable before and after installation and provides a comparative analysis of the splices. The range of the meter is adjustable. Unchecked optical modules can cause: Testing ensures compliance with IEEE 802. 3 and MSA standards, helping avoid failure in real-world deployments. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power. An optical power meter (OPM) measures the power levels of light signals in devices that transmit data or power using light.