Thermal and structural characterization of erbium-doped borosilicate fibers with low silica content containing various amounts of P2O5 and Al2O3

The propagation losses at 1300nm were measured between (7±1) and (25±1)dB/m depending on the glass composition. These high losses have been related not only to crystal formation in some of the fibers during the drawing process as suspected from the Raman spectra but also to inhomogeneity of composition along the preforms as suspected from the picture of the fiber cross-section and also to a large quantity of surface or volume defects within the glass such as impurities, micro-cracks and bubbles. [Display omitted] •Er3+ doped borosilicate glasses were successfully drawn into fibers.•Micro-Raman spectroscopy was used to identify post-draw structural modification.•Drawing leads to changes in small scale molecular orientation.•The extent in the changes between the preform and fiber properties depend on the glass composition.•The Er3+ absorption in the fibers varies between 36 and 47dB/m depending on the glass composition. We report results on the processing and characterization of different glass preforms and single core fibers within the SiO2–Na2O–B2O3–Er2O3–P2O5–Al2O3 system. Micro-Raman spectroscopy was used to identify post-draw structural modification. The differences in the micro-Raman spectra recorded on the preform and on the fiber glass were attributed to a change in the structure induced by the drawing process. Changes in the silicate network organization and small scale molecular orientation within the glass matrix are suspected to occur during the fiber drawing process. We found that the extent in the changes between the preform and fiber properties depend on the glass composition. The glass network of the Al-containing fiber is expected to be less sensitive to the drawing process than that of the fiber matrix as the network of this Al-containing fiber is formed by a larger number of Si-BO units in the network and neutral three-coordinated boron compared to the network of the fiber matrix. From the micro-Raman spectra, formation of small crystals is suspected to occur in the P-containing glasses during the fiber drawing process. The resulting fibers were found to have propagation losses at 1330nm and Er3+ absorption between (7±1) and (25±1)dB/m and (36±1) and (47±1)dB/m, respectively, depending on the glass composition.