The optical module is faulty or not securely installed. If the transmit optical power is abnormal, replace the. An optical power meter is a key tool that measures light strength in the fiber, helping identify signal losses or connection problems. Even minor deviations—whether too high, too low, or unstable—can impact signal integrity, trigger service alarms, or interrupt traffic on DWDM, OTN, or long-haul optical line systems. The meter measures that current and applies a calibration curve to convert it into an optical power reading in dBm.