To set the REF value with the REF key, first connect your optical power meter (OPM) to a stable light source or a reference patch cord, ensuring the connector is clean. Power on the OPM and select the correct wavelength, usually 1310 nm or 1550 nm. It serves as a "zero point" for comparing power loss. If set incorrectly, it can lead to wrong readings and confusion about cable performance. After entering the relative power test mode, the insertion loss (dB) is. Page 1 KPM-11M Optical Power Meter User Manual External and key function description Power reference value setting 1. An optical. PM100USB 1 General Information The PM100USB Optical Power and Energy Meter measures the optical power of laser light or other monochromatic or near monochromatic light, detected by an appropriate sensor and is compatible with all Thorlabs “C-Series” Photodiodes, Thermal Sensors, Pyroelectrics. The OPM Software is a Graphical User Interface (GUI) that has been specially designed for use with various Thorlabs light analysis devices.