Preservation of polarisation orthogonality through a linear optical system

Abstract

It is well known that when two orthogonally polarised optical waves are launched into an optical medium they may experience a loss in orthogonality. In the letter we derive a simple bound on this loss. Our result predicts that orthogonality is virtually preserved for many common single-mode optical components (for example, long lengths of fibres, directional couplers and filters).