How accurate are ORL measurements?
The measurement uncertainty of ORL is very high, about +/-1 dB for singlemode and +/-5dB for multimode, according to round robin results from standards committees. This is a function of the difficulty in creating a reference for the measurement, the reflection is very small compared to the test signal causing noise problems and the dependence of the measurement on the connector on the test apparatus is very high. To minimize uncertainty, keep the connections extremely clean and inspect the connectors continuously with a microscope and repolish when needed. Making measurements to a 0.01 dB resolution is ridiculous; remember this is a +/- 1 dB measurement.
