Capillary optical fiber – design, fabrication, characterization and application

The paper presents a modification of capillary optical fibers fabrication method from an assembled glass preform. A change of dimensional proportions in the capillary optical fiber drawn from a single preform is allowed on-line via the control of overpressure and thermal conditions in the outflow meniscus which essentially lowers the manufacturing costs. These conditions are among the solutions (velocity fields) of the Navier-Stokes equations adapted to the capillary optical fiber pulling geometry and temperature distribution in the oven. The velocity fields give solutions to other quantities of interest such as flow rate, pulling force and fiber geometry. The calculation and experimental results for capillary optical fibers were shown in the following dimensional range: internal diameters 2-200 μm, external diameters 30–350 μm, within the assumed dimensional stability (including ellipticity) better than 1%. The parameters of fabricated capillary optical fibers of high-quality low-loss optical multicomponent glasses were: losses¡100 dB/km, mechanical strength above 1GPa with Weibull coefficient in the range 3–7, internal numerical aperture 0.1–0.3, external numerical aperture 0.1–0.3, core index 1.5–1.8, transparency 0.4–2 μm, thermally and/or chemically conditioned internal surface, double polyimide protection layer, soft or hard jacketed, connectorized. The capillary optical fibers were applied in our own and several external laboratories in spectroscopy, refractometry, micro-fluidics and functional microoptic components. The paper summarizes a design, technological and application work on capillary optical fibers performed during a recent national research program devoted to optoelectronic components and modules.