Single-polarization Fibers | previous | next | feedback |
Definition: optical fibers which transmit only light with a certain polarization
Single-polarization fibers are specialty optical fibers which can transmit light with a certain linear polarization direction, whereas light with the other polarization direction is either not guided or at least experiences strong optical losses. Such fibers should not be confused with polarization-maintaining fibers, which guide light with any polarization state, but can preserve a linear polarization state when the polarization direction is properly aligned with the birefringence axis.
In many cases, single-polarization guidance occurs only in a limited wavelength range. Outside that range, both polarization directions or no light at all may be guided. Also, some fibers exhibit a limited extinction ratio.
Operation Principles
Different principle of operations can be utilized for single-polarization fibers. A common approach is the use an elliptical core, which introduces strong birefringence as well as a wavelength dependence of a cut-off wavelength, so that only light with one polarization direction is guided, whereas the fiber is a leaky waveguide for the other polarization. Alternatively or in addition, the rotational symmetry may be broken by structures around the fiber core, such e.g. air holes in two sides (→ side-hole fibers, hole-assisted fibers). Another class of methods is using built-in mechanical stress. In any case, the birefringence is not only a side product of the broken symmetry, but also serves to reduce the coupling of the two polarization directions.
There are also various types of single-polarization photonic crystal fibers. Here, a suitable arrangement of microscopic air holes again breaks the rotational symmetry and introduces polarization-dependent guiding properties.
Applications
Used in fiber lasers, single-polarization fibers guarantee polarized laser emission. There are also various uses in the field of fiber-optic sensors, where polarization effects in standard fibers can often lead to unwanted effects.
Bibliography
| [1] | V. Ramaswamy et al., "Single polarization optical fibers: exposed cladding technique", Appl. Phys. Lett. 33, 814 (1978) |
| [2] | T. Hosaka et al., "Low-loss single polarization fibers with asymmetrical strain birefringence", Electron. Lett. 17, 530 (1981) |
| [3] | K. Okamoto et al., "Polarization properties of single-polarization fibers", Opt. Lett. 7 (11), 569 (1982) |
| [4] | T. Katsuyama et al., "Propagation characteristics of single polarization fibers", Appl. Opt. 22 (11), 1748 (1983) |
| [5] | D. A. Nolan, "Single-polarization fiber with a high extinction ratio", Opt. Lett. 29 (16), 1855 (2004) |
| [6] | D. T. Walton et al., "Challenges in single-polarization fibers", Proc. SPIE 5709, 316 (2005) |
| [7] | T. Schreiber et al., "Stress-induced single-polarization single-transverse mode photonic crystal fiber with low nonlinearity", Opt. Express 13 (19), 7621 (2005) |
| [8] | M.-J. Li et al., "High bandwidth single polarization fiber with elliptical central air hole", J. Lightwave Technol. 23 (11), 3454 (2005) |
| [9] | J. R. Folkenberg et al., "Broadband single-polarization photonic crystal fiber", Opt. Lett. 30 (12), 1446 (2005) |
See also: polarization-maintaining fibers, photonic crystal fibers
Category: fibers and other waveguides
