Polarization mode dispersion minimization in fiber-wound piezoelectric cylinders

We describe a technique for minimizing polarization mode dispersion (PMD) in broadband interferometry for use with phase modulators of the type formed by coiling nominally circular-core single-mode optical fiber onto piezoelectric cylinders. The technique involves using two piezoelectric elements, arranged to be optically orthogonal. We show that in the general case the two cylinders give rise to four distinct interferograms, but by careful alignment of the elements we reduce these to two coincident interferograms. Hence the large PMD of a single-element modulator is reduced to a negligible level.