*Article* **Fabrication of Active Polymer Optical Fibers by Solution Doping and Their Characterization**

#### **Igor Ayesta 1,\*, Mikel Azkune 2, Eneko Arrospide 1, Jon Arrue 2, María Asunción Illarramendi 3, Gaizka Durana 2 and Joseba Zubia 2**


Received: 27 November 2018; Accepted: 26 December 2018; Published: 31 December 2018

**Abstract:** This paper employs the solution-doping technique for the fabrication of active polymer optical fibers (POFs), in which the dopant molecules are directly incorporated into the core of non-doped uncladded fibers. Firstly, we characterize the insertion of a solution of rhodamine B and methanol into the core of the fiber samples at different temperatures, and we show that better optical characteristics, especially in the attenuation coefficient, are achieved at lower temperatures. Moreover, we also analyze the dependence of the emission features of doped fibers on both the propagation distance and the excitation time. Some of these features and the corresponding ones reported in the literature for typical active POFs doped with the same dopant are quantitatively similar among them. This applies to the spectral location of the absorption and the emission bands, the spectral displacement with propagation distance, and the linear attenuation coefficient. The samples prepared in the way described in this work present higher photostability than typical samples reported in the literature, which are prepared in different ways.

**Keywords:** polymer optical fibers; rhodamine B; solution-doping technique; photostability; optical characterization; penetration of the dopant solution
