Low transmitted power can mean the connectors are dirty. Is it safe to look into the end of a fiber cable?In this video, we explain how to repair an Optical Power Meter that powers ON but does NOT show any optical power reading. REF/dB key: Short press the dB to switch unit, click once nW/dBm/dB to enter the upper clear data, press and hold until REF is displayed on the screen, and set the current optical power as reference value, enter the relative. won't be the correct syntax to turn it off. Turn on the optical power meter (OPM) using the power button. Many sfp modules also have DOM/DDM, which lets you see digital diagnostic monitoring data on network equipment.