The luminescence properties of the Yb/Er-doped phosphosilicate preforms used for the design of active optical fibers were investigated under a tunable laser excitation from ultraviolet to infrared domain. We demonstrated that codoping the glass matrix with Ce 3+ ions strongly influences the infrared emission associated with Er 3+ ions, it enhances the energy transfer from Yb 3+ to Er 3+ ions, and it provides an additional ultraviolet excitation channel for the emission of both Yb 3+ and Er 3+ ions. The excitation/emission pathways are discussed on the basis of models proposed in literature for other systems.