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Single-polarization Fibers

Author: the photonics expert Dr. Rüdiger Paschotta

Definition: optical fibers which transmit only light with a certain polarization

Category: article belongs to category fiber optics and waveguides fiber optics and waveguides

DOI: 10.61835/7bx Cite the article: BibTex plain text HTML Link to this page LinkedIn

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 in only 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 principles of operation can be utilized for single-polarization fibers. A common approach is the use an elliptical core, which introduces strong birefringence and also a polarization 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 as air holes on two sides (side-hole fibers, hole-assisted fibers). Another class of methods uses built-in mechanical stress. In any case, the birefringence 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 lead to unwanted effects.

More to Learn

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Bibliography

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[2]	T. Hosaka et al., “Low-loss single polarization fibers with asymmetrical strain birefringence”, Electron. Lett. 17, 530 (1981); https://doi.org/10.1049/el:19810371
[3]	K. Okamoto et al., “Polarization properties of single-polarization fibers”, Opt. Lett. 7 (11), 569 (1982); https://doi.org/10.1364/OL.7.000569
[4]	T. Katsuyama et al., “Propagation characteristics of single polarization fibers”, Appl. Opt. 22 (11), 1748 (1983); https://doi.org/10.1364/AO.22.001748
[5]	D. A. Nolan, “Single-polarization fiber with a high extinction ratio”, Opt. Lett. 29 (16), 1855 (2004); https://doi.org/10.1364/OL.29.001855
[6]	D. T. Walton et al., “Challenges in single-polarization fibers”, Proc. SPIE 5709, 316 (2005); https://doi.org/10.1049/el:19810371
[7]	T. Schreiber et al., “Stress-induced single-polarization single-transverse mode photonic crystal fiber with low nonlinearity”, Opt. Express 13 (19), 7621 (2005); https://doi.org/10.1364/OPEX.13.007621
[8]	M.-J. Li et al., “High bandwidth single polarization fiber with elliptical central air hole”, J. Lightwave Technol. 23 (11), 3454 (2005); https://doi.org/10.1109/JLT.2005.855856
[9]	J. R. Folkenberg et al., “Broadband single-polarization photonic crystal fiber”, Opt. Lett. 30 (12), 1446 (2005); https://doi.org/10.1364/OL.30.001446
[10]	X. Chen et al., “Wide band single polarization and polarization maintaining fibers using stress rods and air holes”, Opt. Express 16 (16), 12060 (2008); https://doi.org/10.1364/OE.16.012060
[11]	K. K. Y. Lee et al., “Design strategies and rigorous conditions for single-polarization single-mode waveguides”, Opt. Express 16 (19), 15170 (2008); https://doi.org/10.1364/OE.16.015170
[12]	M. Chen and Y. Zhang, “Improved design of polarization-maintaining photonic crystal fibers”, Opt. Lett. 33 (21), 2542 (2008); https://doi.org/10.1364/OL.33.002542

(Suggest additional literature!)

Suppliers

The RP Photonics Buyer's Guide contains four suppliers for single-polarization fibers. Among them:

Exail

Exail (formerly iXblue) polarizing fiber (PZ) is designed so that only one state of polarization is guided along the fiber; any other state of polarization will be lost rapidly, thus yielding a high built-in polarization extinction ratio. This particular mechanism is obtained through a specific waveguide design and a careful optimization of the glass composition resulting in both high birefringence and leakage behavior.

PZ fibers are available for different wavelengths with a broad polarizing window (typically larger than 100 nm), low attenuation and high extinction ratio (≥30 dB), that can be tuned by coiling the proper fiber length at the appropriate coil diameter.

Exail also offers ready-to-use polarizing solutions based on PZ fibers.

Fibercore

Fibercore Zing™ speciality optical fiber is an all-fiber polarizer, guiding only a single-polarization state, providing practical real world polarizing performance. Straight or coiled, Zing™ delivers the high Polarization Extinction Ratio (PER) and broad, stable operating window that applications demand.

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