Adding to the variety of techniques for fabrication of optical fibers, scientists at Virginia Polytechnic Institute and State University in Blacksburg and at Fisk University in Nashville, Tenn., have developed a method they call “core suction.” The technique is especially useful in the fabrication of compound-glass-core fibers, which are important for their optical nonlinearity and their transmission into the infrared spectral region. In the core-suction technique, a molten core is vacuum-sucked into a cladding tube and allowed to cool. A fiber subsequently is drawn from the resulting preform. ©OSA.In the process, a molten core is vacuum-sucked into the cladding tube. Once the core has solidified, the preform can be drawn into a fiber on a conventional drawing tower. The technique is a variation of an earlier method in which the core material — either a powder or a rod — is inserted into a cladding tube and melted. The success of both techniques depends on the cladding having a higher melting temperature than the core. Because relatively minute quantities of the core material are required in either approach, both are especially appropriate for fabricating fibers with very expensive or toxic cores. The core-suction technique, however, eliminates several processing steps that can lead to contamination, and it avoids the problem of air bubbles that can form when the core material is melted inside a cladding tube. Optics Letters, Feb. 15, 2006, pp. 438-440.