A method of qualifying an effective bandwidth of a multimode optical fiber at a first wavelength λ1, using DMD data of the fiber measured a second wavelength λ2. Data representative of a Radial Offset Delay, a Radial Offset Bandwidth and a Relative Radial Coupled Power of the fiber are derived from the DMD data at the second wavelength λ2. A transformation is performed on the ROD data and ROB data at the second wavelength λ2 to obtain corresponding ROD data and ROB data at the first wavelength λ1. An effective bandwidth of the fiber at the second wavelength λ2 is computed using the ROD data and the ROB data at the first wavelength λ1 and the {tilde over (P)}DMD data at the second wavelength λ2.