<title>Optical properties measurement of several photonic crystal fibers</title>

We report the fabrication process for several types of photonic crystal fibers (PCFs), which enables mass-production with a 125micrometers diameter. Five layers of silica capillary tubes having 2 mm inner and 3 mm outer diameters were stacked in a hexagonal pattern around a silica rod of a 3 mm diameter. By jacketing a large silica tube around the tube stack, the preform for a PCF was obtained. Another type of PCF was made by stacking four tubes in one layer, which had 6 mm inner and 8 mm outer diameters. In order to draw PCFs from both types of preforms, a drawing tower for conventional fibers was used. In the beginning of the drawing process, the temperature was set to be the running temperature for the conventional fiber, and then lowered by a couple of hundreds degrees. The optical properties of the fabricated PCFs were measured with various hole sizes and pitches. These include the intensity distribution of the guided beam that was a single mode at 1550 nm, and the transmission loss measured by using the cut back method, and the fundamental mode cut-off characteristic at a short wavelength, and the numerical aperture measured at several wavelengths by using the far field patterns.