While optical power meters are the primary power measurement instrument, optical loss test sets (OLTSs) and optical time domain reflectometers (OTDRs) also measure power in testing loss. TIA standard test FOTP-95 covers the measurement of optical power. Lasers and LEDs for optical telecom will usually be in the near-infrared (=NIR) range of 1260 to 1625 nm, instead of visible light. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power. We describe NIST measurement services for the calibration of optical fiber power meters. They are commonly used during installation. An optical power meter (OPM) measures the power levels of light signals in devices that transmit data or power using light.