Lanthanide-doped polymers are very attractive, since they can be used for luminescent optical fiber fabrications. This Letter presents the terbium-ions-doped poly(methyl methacrylate) fiber fabrication and spectroscopic characterization. The measured excited state (D45) lifetime of 0.741 ms confirms that a used organometallic can be used to obtain an intense luminescence in a polymeric fiber. The luminescence spectrum shape modification versus the fiber length is also investigated.