Doping of optical fiber preforms via porous silica layer infiltration with salt solutions

Abstract

A process is described for reproducible deposition of porous layers uniform along the preform axis, and the effect of the nature of the solvent on the infiltration of salt solutions into the porous layer is analyzed in relation to the fabrication of fiber preforms with controlled doping level. Data are presented on the variation of the retention volume in the porous layer with sintering temperature.

Multiple solution-doping in optical fibre fabrication I – Aluminium doping

“…Recently, Khopin et al [10] have studied solution retention in a porous soot layer as a function of the deposition temperature and the soot layer composition. Partial sintering of the soot occurred immediately after deposition, so that the solution was less able to penetrate the soot layer.…”

An Improved Method of Fabricating Rare Earth Doped Optical Fiber

“…The surface tension of fixed strength of aqueous solution selected for the study is found to be 2 to 3 times higher than that of the ethanolic solution. It has been reported [Khopin et al 2005] Thus lower surface tension as well as smaller complex size of dopant ions are responsible for faster soaking in case of ethanolic solution compared to same strength of aqueous solution when soaked for fixed time span. The investigation reveals that solvent plays an important role in controlling incorporation of RE ion in fiber.…”

Effect of core glass composition on the optical properties of active fibers

“…With the aim of producing active optical fibers with an increased rare-earth concentration in the core, we examined the possibility of doping silica glass with alumina using a two-step MCVD process: deposition of a porous layer which is then infiltrated with a precursor salt solution [13]. As the precursor, we used aluminum nitrate, which is readily soluble in water and alcohols.…”

“…As seen in Fig. 1, the alumina content of the glass can be brought to 3.5-4.0 mol %, using the optimal temperature for sintering the porous layer [13].…”