The aim of this study was to fabricate a bioactive optical fiber able to monitor "in situ" its reaction with the body through changes in its optical properties. Core and cladding preforms were prepared with the composition (97.25*(0.50P(2)O(5)-0.40SrO-0.10Na(2)O)-2.5ZnO-0.25Er(2)O(3)) and (98.25*(0.50P(2)O(5)-0.40SrO-0.10Na(2)O)-1.75ZnO) (in mol%), respectively, and successfully drawn into a multimode core/clad optical fiber. Optical and near-Infrared images assessed the proper light guiding properties of the fiber. The fibers favor the precipitation of a Ca-P reactive layer at its surface concomitant with a reduction in the fiber diameter, when immersed in SBF, often assigned as a sign of bioactivity. It is clearly shown here that the bio-response of the fiber upon immersion in SBF can be tracked from the decrease in the intensity of the Er3+ ions emission at 1.5 mu m. This confirms that the newly developed optical fiber, which combines good optical properties with a suitable bioactive behavior, is a promising platform for the development of novel biomedical devices for biophotonic and photomedical applications. Finally, the successful splicing of the newly developed fiber with commercial optical fibers was an evidence of the possibility to integrate the newly developed phosphate fiber within existing components used in the field of biomedicine.