A design method for single-mode holey fibers with low bending losses

Abstract

With increased demand for larger capacity and lower cost for optical communication systems, high-density wiring and indoor wiring using optical fibers that can be installed or stored with a small bending radius are required. In response to this requirement, the holey fiber (HF), which has a structure with several air holes around the usual optical fiber core, has drawn attention. For the HF, the bending losses can be reduced by enlarging the air holes. However, if a large air hole diameter is used, there is a possibility that multimode operation may occur. Like the conventional optical fiber, the bending losses can be reduced in the HF if the mode field diameter (MFD) is made smaller. In this case, it becomes difficult to connect the HF with a standard single-mode fiber without increasing the loss. In this paper, an HF with two layers of air holes around a core doped with germanium is considered. It is reported that an HF with an allowable bending radius of less than 6.5 mm, a cutoff wavelength of less than 1.25 µm, and an MFD of about 9 µm at a wavelength of 1.55 µm can be designed if the core diameter, the hole spacing, and the hole diameter in each layer are appropriately selected. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(2): 1–7, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20219