Council of Scientific and Industrial Research

Bar-ilan University

Ministry of Information Technology

Mrinmay Pal

Ranjan Sen

Mukul Chandra Paul

Shyamal Kumar Bhadra

Kamal Dasgupta

Aharon Gedanken

Tarun Bandyopadhyay

Minati Chatterjee

Milan Kanti Naskar

Dibyendu Ganguli

Somesh 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 a method of fabricating rare earth doped preforms and optical fibers by a combination of modified chemical vapor deposition (MCVD) process and solution doping technique said MCVD process is used to develop matched or depressed clad structure inside a silica glass substrate tube followed by deposition of porous silica soot layer containing GeO, POor such refractive index modifiers by the backward deposition method for formation of the core and presintering the deposited particulate layer by backward pass with flow of GeCland/or corresponding dopant halides, soaking the porous soot layer into an alcoholic/aqueous solution of RE-salts containing codopants such as AlClin definite proportion, drying, oxidation, dehydration and sintering of the RE containing porous deposit and by collapsing at a high temperature to produce the preform followed by drawing the fibers by known technique to produce fibers with suitable core-clad dimensions and geometry.

Method of fabricating rare earth doped optical fibre

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Calcutta, India

Mrinmay Pal