This is the average value over the current performance-monitoring interval of the transmitted optical power level measured at this port's output during the current performance-monitoring interval, expressed in the device's optical-power units. The average transmit power over the interval shows whether the laser has been holding steady output, since a laser slowly losing output power is a classic sign of transceiver aging. For example, a transceiver whose outOpticalPowerAvg has drifted down by a couple of dB over a year, even though it's still within spec, would be flagged by an admin as a candidate for proactive replacement before it degrades further.