Council of Scientific and Industrial Research

Bar-ilan University

Tarun Bandyopadhyay

Ranjan Sen

Mukul Chandra Paul

Kamal Dasgupta

Shyamal Kumar Bhadra

Aharon Gedanken

Mrinmay Pal

Milan Kanti Naskar

Dibyendu Ganguli

Minati Chatterjee

The present invention discloses a process for making rare earth (RE) doped optical fiber by using RE oxide coated silica nanoparticles as the precursor material, more particularly the method of the present invention involves preparation of stable dispersions (sol) of RE oxide coated silica nanoparticles at ambient temperature and applying a thin coating on the inner surface of silica glass tube following dip coating technique or any other conventional methods, of the said silica sol containing suitable dopants selected from Ge, Al, P, etc., the coated tubes were further processed into optical preforms by following MCVD technique and fiberized in desired configuration, the novelty lies in eliminating the step of the formation of porous soot layer at high temperature by CVD process inside a fused silica glass tube for formation of the core and also in the elemination of the incorporation of the rare earth ions into the porous soot layer following the solution doping technique or other conventional methods, the direct addition of RE oxides in the sol eliminates the formation of microcrystalites and clusters of rare earth ions and prevents change in composition including variation of RE concentration in the core which results in increase in the reproducibility and reliability of the process to a great extent, further the addition of Ge(OET)at ambient temperature in the silica sol reduces the quantity of GeClwhich is required at high temperature to achieve the desired Numerical Aperture.

Process of making rare earth doped optical fiber

The present invention provides an improved process for making rare earth doped preforms and fibers by a combination of MCVD technique and solution doping method, said method comprising developing matched or depressed clad structure inside a silica glass substrate tube followed by deposition of unsintered particulate layer containing GeO and P O for formation of the core and solution doping by soaking the porous soot layer into an alcoholic/aqueous solution of RE-salts containing co-dopants like AlCl /Al(NO ) in definite proportion, controlling the porosity of the soot, dipping period, strength of the solution and the proportion of the codopants to achieve the desired RE ion concentration in the core and minimize the core clad boundary defects and followed by drying, oxidation, dehydration and sintering of the RE containing porous deposit and collapsing at a high temperature to produce the preform and overcladding with silica tubes of suitable dimensions and fiber drawing to produce fibers.

Process for making rare earth doped optical fiber

Growing community of inventors

Calcutta, India

Tarun Bandyopadhyay