| 摘要 |
<p>A polarization-maintaining optical fiber includes a core region and a cladding region formed around the core region, the cladding region having a refractive index lower than a refractive index of the core region. A refractive index profile of the core region is either one of a step shaped or a concave shaped, and the cladding region includes two holes formed in such a manner that a shortest distance from the core region is virtually zero at locations in opposite to each other across the core region. It is preferred that, when a shape of the refractive index profile of the core region from a point where a relative refractive index difference with respect to the cladding region is zero to a point where the relative refractive index difference is three quarters of a maximum relative refractive index difference is approximated by an ±-type refractive index profile at a boundary between the core region and the cladding region, the refractive index profile of the core region has a shape in which an ± value is equal to or larger than 3.5. With this scheme, there is provided a side-tunnel-type polarization-maintaining optical fiber with a superior polarization maintaining property and a reduced transmission loss.</p> |
