Abstract

Optical fibers with silica-air microstructures called photonic crystal fibers (PCF) have lots of unique properties which are not realized in conventional optical fibers.^1,2 Two types of PCFs have been developed. The first type has a conventional core and cladding structure. Air holes are added in the vicinity of the core.³ The second type of PCFs is made from a single material such as un-doped silica glasses.¹ An array of air holes runs along the length of the fiber. One of the holes which act as a core is missing. Unfortunately, the optical losses of these fibers have been relatively high compared with those of conventional single-mode fibers, which exhibit optical loss of 0.2 dB/km at 1.55 µm wavelength. Several researches have already been done to reduce the optical loss of PCFs. In the first type fiber, the lowest loss of 0.82 dB/km has been reported.⁴ In the second type of fibers, the lowest loss so far reported is 3.2 dB/km at 1.55µm wavelength.⁵ However, for a practical transmission line, the optical losses are still high and further improvement in fabrication technology should be needed to reduce the losses.

© 2002 Optical Society of America