Modal birefringence at low loss and an approximately zero material dispersion wavelength of around 1.3 μm, and chromatic dispersion characteristics for polarization mode dispersion in the

m wavelength region are measured in single-mode fibers with stress-induced anisotropy. It is found from the measurements that the quantity concerned with the difference between the phase and group velocities equals approximately

at the 1.290 μm wavelength in actual silica fibers. In addition, a stress-optical constant is evaluated from the measurements of linear birefringence caused by externally applied pressure, and it is

mm
2/kg . W at the 1.290 μm wavelength.