This read-write object sets the allowed variance, in dBm, in optical power received on this port beyond which a threshold-crossing alert will be generated. It lets an admin configure sensitivity to fiber-link degradation directly in terms of a deviation from a baseline receive-power level, rather than an absolute value, which better captures gradual drift on any given fiber run. For example, an admin might set cmEthernetTrafficPortThresholdVarOprVariance to 3 dBm so that an alert fires only once received optical power drifts three decibels from its established baseline, catching a slowly failing transceiver before it goes dark.