Process of fabrication of erbium and ytterbium-co-doped multi-elements silica glass based cladding-pumped fiber

A process of fabrication of erbium and ytterbium-co-doped multi-elements silica glass based cladding-pumped fiber for use as a highly efficient high power optical amplifier, which comprises the following steps:

• a) Deposition of pure SiO2 synthetic cladding within a silica glass substrate tube to obtain matched clad type structure;
• b) Deposition of fluorine doped porous phospho-silica layer with flow of O2/POCl3 in the range of 800 to 900 sccm and SF6 in the range of 25 to 35 sccm within 1420-1455° C. forming a core glass by back-pass deposition technique maintaining the burner speed within 28-35 mm/min;
• c) Pre-sintering of the deposited porous soot layer within 1075-1125° C. to maintain uniform porosity keeping the burner speed in the range of 305-315 mm/min along forward direction;
• d) Soaking of the porous fluorinated phospho-silica layer into an alcoholic solution containing AlCl3, 6H2O in the range of 0.12 to 0.15 (M), ErCl3, 6H2O in the range of 0.02 to 0.023(M), YbCl3 6H2O in the range of 0.25 to 0.28 (M), CeCl3 7H2O in the range of 0.003 to 0.0035(M), H3BO3 in the range of 0.5 to 0.75(M) under one hour soaking period;
• e) Drying of the soaked porous layer under flow of an inert Ar gas for 30 to 45 minutes;
• f) Incorporation of Er2O3, Yb2O3, P2O5, F, CeO2, Al2O3, B2O3 into a porous dried layer in the presence of O2 and He within 700-850° C. for efficient oxidation;
• g) Dehydration of the core layer at a temperature in the range of 850 to 900° C. in presence of Cl2 and O2;
• h) Sintering of the porous core layer in presence of a mixture of O2 and He in the temperature range 1350 to 1890° C. with flow of O2/GeCl4 and O2/POCl3;
• i) Incorporation of 2-3 numbers of Er and Yb co-doped multielements silica glass based layers through repetition of the above process from deposition of the porous layer to sintering stage maintaining all the process parameters same with respect to particular preform making run;
• j) Collapsing of the tube at a temperature in the range of 2000 to 2250° C. with the flow of POCl3 to achieve Er/Yb codoped multielements silica glass based optical preform of 10.0±0.1 mm diameter;
• k) Increase of preform diameter from 10.0±0.1 mm to 18.5±0.1 mm through the overcladding process using a thick silica tube at a temperature in the range of 2200 to 2400° C.;
• l) Octagonal shaping of the overcladded preform through grinding of silica mass from the preform surface varying the grinding length 0.72 to 0.75 mm from the surface of circular overcladded preform along each of 6 points on equal distance followed by polishing of each grinded side into Octagonal shaped structure;
• m) Drawing of octagonal cladding shaped Er/Yb doped fiber using PC 375L AP compound as a low RI resin coating at a preform feed down speed within 0.6 to 0.7 mm/min and fiber drawing speed within 20-25 m/min;
• n) Experiments for use of such kind of multielements doped silica glass based fiber as a highly efficient high power optical amplifier under pumping at 940 nm wavelength;
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• o) Experiments for use of such kind of multielements silica glass based fiber as high power optical amplifier in radiation environment through on-line measurement of the lasing output power under variation of the dose rates of 60Co gamma radiation within 0.35-0.70 rad/s (equivalent to dose rates in free space) upto 6.0 Krad total cumulative dose.