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09 Mar 2006
A simple suction technique is an ideal way to create optical fiber preforms whose core is made from multiple constituents, say researchers.
Researchers in the US say they have come up with a simple and inexpensive way to make optical fibers with compound glass cores. Named "core-suction", the team believes the approach is ideal for producing the nonlinear fibers required for Raman amplifiers, fiber lasers and continuum generation. (Optics Letters 31 438)
"The core-suction technique also eliminates several processing steps compared with other techniques, which can lead to contamination," Nitin Goel from Virginia Polytechnic Institute and State University told optics.org. "Our approach also avoids the problem of air bubbles which can form when the core material is melted inside the cladding tube."
The core-suction method involves melting the core glass sample, which could contain multiple components, in a small alumina crucible within a muffle furnace. A silica cladding tube is then inserted into the crucible and a vacuum pump draws the molten core material into the cladding tube to create the preform. Once the preform has cooled, it can be drawn into a fiber or overcladded to achieve a desired core-cladding ratio.
Goel and his colleagues from Fisk University, US, have successfully fabricated several preforms using their core-suction technique. The first preform incorporated Schott SF6 glass as the core while the second was made with a lead-tellurium-germanate core glass.
"The other materials systems we have used so far are lead-germanate-tellurite-erbium, lead-germanate-tellurite-neodymium and a high erbium-doped phosphate glass called MM2," said Goel. "The preform made from the MM2 glass was also drawn into fibers and used to make optical amplifiers with 1 cm and 5 cm lengths of fiber."
The researchers add that the small quantities of starting materials allow expensive high-purity materials to be used. "The use of a controlled atmosphere [in the furnace] and extremely small quantities of start material should make the safe use of toxic constituents possible," say the authors in their paper.
Goel adds that the team is hoping to draw bismuth-based glasses into fibers in the near future.
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