How to measure network cable voltage with an optical power meter

An optical power meter cannot measure electrical voltage on network cables; it is designed to measure light power in fiber optic cables.Why Optical Power Meters Cannot Measure VoltageOptical power meters are specifically designed to detect light signals in fiber optic cables and convert them into electrical signals to display optical power in dBm (decibels relative to 1 milliwatt) or insertion loss in dB . They use a photodiode sensor to detect photons, not the electrical voltage or current present in copper Ethernet cables . Attempting to measure voltage on a network cable with an optical power meter will not work and could damage the meter.Correct Methods to Measure Network Cable VoltageTo measure voltage on Ethernet or other copper network cables, you should use:Digital Multimeter (DMM)Set the meter to DC voltage mode.Connect the probes to the cable conductors (e.g., pins 1 and 2 for standard PoE lines).Read the voltage directly on the display.PoE Tester (for Power over Ethernet)Designed to safely measure PoE voltage and current on Ethernet cables.Provides quick verification of whether the cable is delivering the expected voltage (typically 48V for standard PoE).Cable Testers with Voltage DetectionSome advanced Ethernet testers can detect live voltage and verify cable integrity simultaneously.SummaryWhile an optical power meter is essential for fiber optic testing and can help check Ethernet cable integrity in terms of signal quality, it cannot measure electrical voltage. For voltage measurement, use a digital multimeter, PoE tester, or specialized cable tester. Always ensure the cable is powered appropriately and follow safety precautions when measuring live network lines.