Abstract

In contrast to a multimode fibre carrying many modes,the single-mode fibre has the ability to transmit linearly polarized light over long distances. In a practical monomode fibre, however, a degree of ellipticity exists in the core (typically 1-10% in our fibres). This produces a propagation delay between the two orthogonally polarized states of the HE₁₁ mode and, consequently, a birefringence. In general, therefore, the output polarization state is elliptical and differs from that at the input. A knowledge of the retardation which occurs between the two non-degenerate forms of the HE₁₁ mode is important, not only because it ultimately provides a limitation to the attainable fibre bandwidth (1), but because several potential applications require a predictable and stable output polarization. Examples are those which require two beam interference, such as the fibre interferometer (2) and remote holography, and those which observe the output polarization, as in magnetic field measurements. The latter utilise the Faraday effect to rotate the fibre polarization state in proportion to an applied magnetic field.

© 1977 Optical Society of America