Single-mode, single-polarization optical fiber

A single-mode, single-polarization optical fiber comprising a core and a cladding including an asymmetric stress-applying region, which fiber has a depressed index of refraction along at least one axis of symmetry and is characterized by the feature that

• a pair of refractive index profiles from a single symmetry axis of the optical fiber may be measured with plane polarized light that is aligned to be parallel to the chosen symmetry axis for one of said refractive index profiles and perpendicular to the chosen symmetry axis for the other of said refractive index profiles and a parameter and .eta. may be calculated from each such profile by the expression ##EQU3## where n(r) represents the refractive index at the radial position r measured along said symmetry axis and with one of the two said orientations of polarized light;
• n.sub.c1 is the average refractive index of the cladding over a distance from 4 to 7 core radii from the core center;
• and .alpha. has a value from 1 when both the core and cladding are circular to nearly 0 when the core and cladding are so elongated that the fiber behaves essentially as a planar waveguide;
• and
• .eta. for one symmetry axis is positive when calculated from the refractive index profile determined with one of the two said orientations of polarized light and is negative when calculated from the refractive index profile determined with the orthogonal orientation of polarized light, and for each other symmetry axis of the novel optical fiber .eta. is positive for both orientations of plane polarized light.