Ionizing radiation-resistant optical fiber amplifier

An amplifying optical fiber, comprising:

• a central core for transmitting and amplifying optical signals, said central core comprising discrete nanoparticles that include (i) at least about 85 weight percent silica and (ii) erbium (Er);
• and
• an inner optical cladding for confining optical signals transmitted in said central core, said inner optical cladding surrounding said central core;
• wherein outside the absorption band of erbium and before any irradiation, the optical fiber has optical losses less than or equal to 1.5 dB/km at a wavelength of 1200 nanometers.

A method for making an optical-fiber primary preform, comprising:

• synthesizing rare-earth-doped silica-based nanoparticles containing at least 85 weight percent silica by co-precipitating precursors of silica salts and rare earth salts in an aqueous solution, with a molar ratio of precursors of silica salts to precursors of rare earth salts of between about 30 and 300;
• dispersing the nanoparticles in an aqueous solution;
• and
• impregnating an internal porous layer of a silica tube with the aqueous solution containing nanoparticles in order to form the core of a primary preform.

An optical fiber, comprising:

• a central core comprising a core matrix;
• and
• an optical inner cladding surrounding said central core;
• wherein said core matrix comprises nanoparticles, said nanoparticles comprising a nanoparticle matrix that includes (i) at least about 85 weight percent silica and (ii) at least one rare earth element;
• and
• wherein, at ambient temperature, the optical fiber has a loss increment of less than 0.05 dB/m at a wavelength of 1550 nanometers under irradiation of 300 Gy at 0.08 Gy/min.