Single-mode fibers can propagate light with two orthogonal polarizations. Although transmission fibers are nominally circular, a small-core ellipticity can make the propagation constants and group velocities slightly different for the two polarizations, causing polarization mode dispersion (PMD). This can be the major limitation for high-bit-rate systems operating near the wavelength of zero chromatic dispersion. We describe a new technique for screening out fibers with PMD values that can be large enough to degrade system performance. It involves locating the major and minor axes of the fiber’s elliptical core and measuring the difference between the widths of the corresponding orthogonal far-field radiation patterns.
© 1988 Optical Society of AmericaPDF Article