Fabrication of miniature optical fiber and microfiber coils

We demonstrate a technique for simultaneous drawing, tapering, and coiling of a silica optical fiber that is locally heated by a CO2 laser. It allows us to fabricate coils of silica fibers and microfibers with diameters ranging from ∼100 μm down to less than a micron. As an application, we demonstrate an evanescent coiled fiber refractometric sensor comprising 15 cm of standard single mode optical fiber. The dimension of this sensor is only 3 mm×3 mm×4 mm and its sensitivity in the aqueous environment is estimated as ∼160 nm/RIU.