Transmission profile of a tapered fiber pull. Plot of transmission vs pull time for a tapered fiber pull, normalized to the maximum transmission through the fiber before the pull. This pull was performed using a hydrogen flame generated by the OX-00 torch tip, producing a hot-zone of ∼1.3 mm, at a pull speed of 40 μm/s, which resulted in a final transmission efficiency of 78%. The important regions of the transmission profile are labeled accordingly. Inset: Finite element method simulation of the time averaged energy density for the fundamental mode at 1550 nm of an air-clad tapered fiber with a diameter of 1 μm and index of refraction 1.4677. The white circle indicates the limits of the fiber geometry, separating the internal guided mode from the evanescent field located outside the fiber.