Measurements of loss and bandwidth in multi-mode fibers are highly dependent on the modal condition of the light source used for the measurement. For example, OTDR and LS/PM loss measurements can differ significantly simply because an OTDR uses a laser source and not an LED. These widely different modal characteristics between sources used in measuring fiber optic systems and networks result in a large and source dependent uncertainty in the accuracy of measurements. When using a ModCon, you launch the same distribution of modes into the fiber regardless of the source being used and consequently reduce the uncertainty in your measurements due to variation between sources. In summary the ModCon increases the accuracy of measurements, gives better agreement between test data sets and is a simple and certifiable method of complying with international standards.