Patent ID: 6751990
Filing Date: 2004-06-22
Classification: C03B,Y02P

Abstract:
A process for making rare earth (RE) doped optical fibre, said process comprising steps of:a) providing deposition of P2O5 and F doped synthetic cladding within a silica glass substrate tube to obtain matched or depressed clad type structure, b) forming a core by depositing unsintered particulate layer at a tube surface temperature in the range of 1200-1400Â° C., c) maintaining P2O5 and GeO2 concentrations from 0.5 to 5.0 mol % and 3.0 to 25.0 mol % in the said particulate layer respectively to obtain a tube containing F-doped cladding and porous soot layer, d) immersing the tube containing the porous soot layer into a solution containing RE salt in the concentration range of 0.002 M to 0.25 M with or without aluminum salt in the concentration range 0.05 M to 1.25 M for a period of 1 to 2 hours, e) draining the solution out at a rate in the range of 10-50 cc/min, f) drying the porous layer by flowing dry nitrogen or any other inert gas through the tube, g) heating the tube gradually in presence of O2 and He at a temperature ranging between 600-1100Â° C., h) dehydrating the core layer of the tube at a temperature in the range of about 800-1200Â° C. and in presence of excess Cl2 and O2 and He, i) sintering the core layer in presence of a mixture of oxygen and helium and GeCl4 in the temperature range between 1400 to 1900Â° C., j) collapsing the tube at a temperature ranging from 2000-2300Â° C. to obtain a preform, k) overcladding the preform with silica tube, and l) drawing fibres from the preform.