Fabrication of Alumina-Doped Optical Fiber Preforms by an MCVD-Metal Chelate Doping Method

Abstract

This paper reports on the fabrication of alumina-doped preforms using a modified chemical vapor deposition (MCVD)-vapor phase chelate delivery system with Al(acac)3 as the precursor. The objectives of this work are to study the deposition process, the efficiency of the fabrication process, and the quality of the fabricated fiber preforms. Two parameters are studied, the Al(acac)3 sublimator temperature (TAl °C) and the deposition direction (i.e., downstream and upstream). Other parameters such as the oxygen flow and deposition temperature are fixed. The results show that high uniformity of the refractive index difference (%RSD < 2%) and core size (%RSD < 2.4%) was obtained along the preform length using downstream deposition, while for the combined upstream and downstream deposition, the uniformity deteriorated. The process efficiency was found to be about 21% for TAl °C of 185 °C and downstream deposition. From the EDX elemental analysis, the refractive index was found to increase by 0.0025 per mole percent of alumina.

Advances in laser‐based manufacturing techniques for specialty optical fiber

“…F I G U R E 9 Schematic illustrating the laser-aided fabrication of specialty fibers: (left to right) LPD of X-doped rod printing, preform making, and fiber drawing. As shown by the inserted cross-sectional composition profiles graph, by adapting the rod-in-tube technique, composition discrepancies at the center of the preform can be mitigated (see Figure 2 and e.g., Sharif et al 59 ; adapted from Maniewski et al 120 ).…”

“…This fabrication method may lead to composition discrepancies at the center of the preform 42,57 . These discrepancies can originate from the difference in volatility or reaction rates for different precursors, which could lead, for example, to so‐called burn‐out or incomplete oxidation of the precursors 58,59 . Although process optimization, which includes reaction temperature, oxygen, and precursor flow rates, can help reduce the discrepancies, unattained significant axial inhomogeneities may be a clear drawback for core‐pumped gain fibers, as this inhomogeneity typically overlaps with the peak power of the pump, thus potentially lowering device efficiency.…”

Broadband Profiled Eye-Safe Emission of LMA Silica Fiber Doped with Tm3+/Ho3+ Ions

“…Therefore, a system of precise control of the chemical composition of the preform along its entire length is crucial. This was discussed in detail in prior publications [34][35][36][37][38][39][40]. The increasing refractive index of silica is performed using phosphorus, germanium, and aluminum.…”