Manufacturing
An SDF is usually created by tapering a commercial optical fibre. Special pulling machines accomplish the process.
An optical fibre usually consists of a core, a cladding and a protective coating. Before pulling a fibre, its coating is removed (the fibre is stripped). Then the bare fibre is fixed at two ends on the movable translation stages of the pulling machine. The middle of the fibre between the stages is then heated with a flame or a laser beam and at the same time the translation stages move in the opposite directions. The glass melts and the fibre is elongated so that its diameter decreases. The flame or laser beam usually also moves in order to obtain waist of significant length and constant thickness.
Using the described method, waists of 1...10 mm in length and diameters down to 100 nm are obtained.
Read more about this topic: Subwavelength-diameter Optical Fibre