Council of Scientific and Industrial Research

Bar-ilan University

Department of Electronics and Information Technology

Department of Information Technology

Ministry of Information Technology

Ranjan Sen

Mukul Chandra Paul

Shyamal Kumar Bhadra

Kamal Dasgupta

Tarun Bandyopadhyay

Mrinmay Pal

Aharon Gedanken

Himadri Sekhar Maiti

Maitreyee Saha

Minati Chatterjee

Dibyendu Ganguli

Milan Kanti Naskar

Somesh Chatterjee

Anirban Dhar

Anal Tarafder

Annapurna Kalyandurg

Atul Dnyaneshwar Sontakke

Kaushik Biswas

Basudeb Karmakar

Atiar Rahaman Molla

The present invention provides a process for fabrication of ytterbium (Yb) doped optical fiber through vapor phase doping technique. The method comprises deposition of Al2O3 and Yb2O3 in vapor phase simultaneously in combination with silica during formation of sintered core layer. This is followed by collapsing at a high temperature in stepwise manner to produce the preform and drawing of fibers of appropriate dimension. The process parameters have been optimized in such a way that Al and Yb-chelate compounds can be transported to the reaction zone without decomposition and condensation of precursor materials. Thus variations of dopants concentration along the length of the preform have been minimized to &#x3c;1% and good repeatability of the process has also been achieved. The resulting fibers also have smooth core-clad boundary devoid of any star-like defect. The process can be reliably adopted for fabrication of large core Yb doped optical fibers. The fibers also show low loss, negligible center dip and good optical properties suitable for their application as fiber lasers.

Process for fabrication of ytterbium doped optical fiber

The present invention provides a method of making rare earth (RE) doped optical fiber using BaO as co-dopant instead of Al or P commonly used for incorporation of the RE in silica glass by MCVD and solution doping technique. The method comprises deposition of particulate layer of GeOdoped SiOwith or without small POfor formation of the core and solution doping by soaking the porous soot layer into an aqueous solution of RE and Ba containing salt. This is followed by dehydration and sintering of the soaked deposit, collapsing at a high temperature to produce the preform and drawing of fibers of appropriate dimension. The use of Ba-oxide enables to eliminate unwanted core-clad interface defect which is common in case of Al doped fibers. The fibers also show good RE uniformity, relatively low optical loss in the 0.6-1.6 &#x3bc;m wavelength region and good optical properties suitable for their application in amplifiers, fiber lasers and sensor devices.

Method for fabricating rare earth (RE) doped optical fiber using a new codopant

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

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

Kolkata, India

Ranjan Sen