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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 12, Iss. 16 — Aug. 9, 2004
  • pp: 3888–3893
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Highly birefringent hollow-core photonic bandgap fiber

Xin Chen, Ming-Jun Li, Natesan Venkataraman, Michael T. Gallagher, William A. Wood, Alana M. Crowley, Joel P. Carberry, Luis A. Zenteno, and Karl W. Koch  »View Author Affiliations


Optics Express, Vol. 12, Issue 16, pp. 3888-3893 (2004)
http://dx.doi.org/10.1364/OPEX.12.003888


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Abstract

A hollow-core photonic band-gap fiber with very high group birefringence is fabricated and characterized. Two independent methods, wavelength scanning and direct measurement of differential group delay (DGD), are used to obtain the group beatlength and group birefringence. The fiber illustrates a very high group birefringence of 0.025 at 1550 nm. The wavelength dependence of the group beatlength and group birefringence are also analyzed.

© 2004 Optical Society of America

1. Introduction

Fibers with high birefringence are of significant research interest as they are expected to find many applications in optical communication systems, devices and fiber sensors. In conventional polarization maintaining (PM) fibers, high fiber birefringence is achieved by introducing anisotropy in the geometry or stress in the fiber profile [1

1. J. Noda, K. Okamoto, and Y. Sasaki, “Polarization-maintaining fibers and their applications,” J. Lightwave Technol. 4, 1071–1089 (1986) [CrossRef]

]. Fibers such as PANDA [2

2. T. Hosaka, K. Okamoto, T. Miya, Y. Sasaki, and T. Edahiro, “Low-loss single-polarization fibers with asymmetrical strain birefringence,” Electron. Lett. 17, 530–531 (1981). [CrossRef]

] and bow-tie fiber [3

3. M. P. Varnham, D. N. Payne, R. D. Birch, and E. J. Tarbox, “Single-polarization operation of highly birefringent bow-tie optical fibers,” Electron. Lett. 19, 246–247 (1983). [CrossRef]

] achieve high birefringence through stress members while fibers with an elliptical core [4

4. R. B. Dyott, J. R. Cozens, and D. G. Morris, “Preservation of polarization in optical-fiber waveguides with elliptical cores,” Electron. Lett. 15, 380–382 (1979). [CrossRef]

] and side air holes [5

5. T. Okoshi, K. Oyamada, M. Nishimura, and H. Yokata, “Side-tunnel-fiber: An approach to polarization-maintaining optical waveguide scheme,” Electron. Lett. 18, 824–826 (1982). [CrossRef]

] reach the high birefringence through asymmetry in core geometry. For highly birefringent fibers that use geometrical anisotropy the birefringence is influenced by the index contrast between the high index core and low index region [6

6. T. Okoshi, “Single-polarization single mode optical fibers,” IEEE J. Quantum. Electron. 17, 879–884 (1981). [CrossRef]

].

In recent years, alternative approaches for achieving high birefringence have been explored in the area of photonic crystal fibers (PCFs) since they can have a much higher refractive index contrast than conventional fibers [7

7. A. Ortigosa-Blanch, J. C. Knight, W. J. Wadsworth, J. Arriaga, B. J. Mangan, T. A Birks, and P. St. J. Russell, “Highly birefringent photonic crystal fibers,” Opt. Lett. 25, 1325–1327 (2000). [CrossRef]

12

12. K. Saitoh and M. Koshiba, “Photonic bandgap fibers with high birefringence,” IEEE Photon. Technol. Lett. 14, 1291–1293 (2002). [CrossRef]

]. Highly birefringent index-guiding PCFs with holes of different diameters along two orthogonal fiber axes or with asymmetric core designs have been proposed [7

7. A. Ortigosa-Blanch, J. C. Knight, W. J. Wadsworth, J. Arriaga, B. J. Mangan, T. A Birks, and P. St. J. Russell, “Highly birefringent photonic crystal fibers,” Opt. Lett. 25, 1325–1327 (2000). [CrossRef]

11

11. J. Ju, W. Jin, and M.S. Demokan, “Properties of a highly birefringent photonic crystal fiber,” IEEE Photon. Technol. Lett. 15, 1291–1293 (2003). [CrossRef]

]. Highly birefringent photonic bandgap fibers (PBGFs) with asymmetric air cores have also been suggested [12

12. K. Saitoh and M. Koshiba, “Photonic bandgap fibers with high birefringence,” IEEE Photon. Technol. Lett. 14, 1291–1293 (2002). [CrossRef]

]. Numerical analysis indicates that birefringence as high as 10-3 is possible for both types of fibers. Measured birefringence values resulting from index-guiding PCFs, which are in the range of 10-4 to 10-3, have confirmed the numerical predictions [7

7. A. Ortigosa-Blanch, J. C. Knight, W. J. Wadsworth, J. Arriaga, B. J. Mangan, T. A Birks, and P. St. J. Russell, “Highly birefringent photonic crystal fibers,” Opt. Lett. 25, 1325–1327 (2000). [CrossRef]

, 9

9. T. P. Hansen, J. Broeng, E. B. Libori, E. Knudsen, A. Bjarklev, J. R. Jensen, and H. Simonsen, “Highly birefringent index-guiding photonic crystal fibers,” IEEE Photon. Tech. Lett. 13, 588–590 (2001). [CrossRef]

, 10

10. K. Suzuki, H. Kubota, and S. Kawanishi, “Optical properties of a low-loss polarization-maintaining photonic crystal fiber,” Opt. Express 9, 676–680 (2001). [CrossRef] [PubMed]

]. No experimental efforts in achieving high birefringence in PBGFs have been reported, although experimental study on a birefringent PBGF with beatlength as short as 4 mm around 850 nm has been conducted [13

13. G. Bouwmans, F. Luan, J. C. Knight, P. St. Russell, L. Farr, B. J. Mangan, and H. Sabert, “Properties of a hollow-core photonic bandgap fiber at 850nm wavelength,” Opt. Express 14, 1613–1620 (2003). [CrossRef]

]. The level of the birefringence in Ref.[13

13. G. Bouwmans, F. Luan, J. C. Knight, P. St. Russell, L. Farr, B. J. Mangan, and H. Sabert, “Properties of a hollow-core photonic bandgap fiber at 850nm wavelength,” Opt. Express 14, 1613–1620 (2003). [CrossRef]

] has not exceeded that of conventional polarization maintaining fibers.

In this paper, we report on a highly birefringent PBGF. Fiber group birefringence of 0.025 at 1550 nm is demonstrated. To the best of our knowledge, this is the first experimental demonstration of such high level of group birefringence in microstructured fibers. Our focus in this paper is the group birefringence. The birefringence mentioned in the literature can either be group birefringence (beatlength) or phase birefringence (beatlength). However, since the difference in value between the two is usually within 10–15%, a fiber with high group birefringence also has high phase birefringence.

2. The highly birefringent photonic bandgap fiber and its characterization

Fig. 1. Cross section of the hollow-core PBGF profile. The dark regions are air, while the white regions are glass.
Fig. 2. The normalized transmission spectrum of the photonic bandgap fiber.

We employ two independent methods, wavelength scanning and direct measurement of differential group delay (DGD) to obtain the group beatlength of the fiber under test.

Fig. 3. Schematic of group beatlength measurement using wavelength scanning method.

LB=Δλλ¯L,
(1)

where λ̄ is the center wavelength between the two peaks and L is the length of the sample fiber. In [14

14. K. Kikuchi and T. Okoshi, “Wavelength-sweeping technique for measuring the beat length of linearly birefringent optical fibers,” Opt. Lett. 8, 122–124 (1983) [CrossRef] [PubMed]

] it is suggested that both polarizers be aligned at 45 degrees to the birefringent axis of the fiber under test, we find that the period of the modulated signal is not affected by the polarizer orientations. Therefore, in our measurements, little effort was made to align the polarizers except that we ensured that sufficient modulation be observed.

B=λLB.
(2)

Using Eq. (2), we obtain the birefringence of the sample to be 0.029 and 0.02 at 1520 nm and 1580 nm, respectively. To our knowledge, this is the highest fiber birefringence ever reported in the literature. Despite of very high birefringence, higher order mode that can be excited due to slight misalignment at the light launch end can negatively affect the polarization maintaining capability of the fiber. This fiber does not preserve polarization as well as conventional polarization maintaining fibers without a careful alignment.

Fig. 4. The optical spectrum collected by the OSA. (a) the whole spectrum; (b) spectrum around 1520nm; (c) spectrum around 1580nm. The length of the fiber under test is 357 mm.

τ=λLcLB=B·Lc,
(3)

where L is the length of the fiber under test and c is the speed of light in vacuum. Using Eq. (3) we calculate the fiber birefringence as shown in Fig. 6(b). For comparison, we also show the birefringence obtained by fitting the wavelength scanning data. Good agreement is achieved between the two methods.

Fig. 5. (a) The spectrum of Windowed Fourier transformation of OSA trace. The OSA data spacing is 0.025nm, and window size is 4nm. (b) The fiber beat length and birefringence as a function of wavelength. The solid lines are the linearly fitted birefringence, and the resulting beat length.
Fig. 6. DGD of the fiber under test with length of 520mm. (b) The birefringence as a function of wavelength. The red line is the fitted line obtained by fitting the wavelength scanning data.

3. Conclusion

A highly birefringent hollow-core photonic bandgap fiber is characterized. The fiber group birefringence properties were measured by two independent methods: wavelength scanning, and direct measurement of differential group delay. The fiber group beatlength and group birefringence have subsequently been calculated. Good agreement between the two methods is achieved. It is found that the fiber has a group birefringence of 0.025 at the wavelength of 1550nm. We also obtain an empirical equation describing the group birefringence as a function of wavelength.

To our knowledge, this is the first experimental work intentionally realizing high group birefringence in a hollow-core photonic band-gap fiber. The reported group birefringence is higher than all previously reported microstructured fibers, and is one order of magnitude higher than that predicted in a theoretical calculation [12

12. K. Saitoh and M. Koshiba, “Photonic bandgap fibers with high birefringence,” IEEE Photon. Technol. Lett. 14, 1291–1293 (2002). [CrossRef]

]. Understanding the discrepancy between our experimental results and the theoretical predictions represents a significant theoretical challenge. Note that in a typical PBGF, the refractive index span of a photonic band gap is on the order of 0.02. We believe that understanding the detailed theoretical mechanism of such a high level of group birefringence in hollow-core photonic band-gap fiber is a subject worthy of future research. Further effort along this line has been initiated.

Acknowledgments

This work was funded in part by DARPA under contract MDA972-02-3-0004. We also would like to thank Dirk Müller for some preliminary measurements in early stage of the work.

References and links

1.

J. Noda, K. Okamoto, and Y. Sasaki, “Polarization-maintaining fibers and their applications,” J. Lightwave Technol. 4, 1071–1089 (1986) [CrossRef]

2.

T. Hosaka, K. Okamoto, T. Miya, Y. Sasaki, and T. Edahiro, “Low-loss single-polarization fibers with asymmetrical strain birefringence,” Electron. Lett. 17, 530–531 (1981). [CrossRef]

3.

M. P. Varnham, D. N. Payne, R. D. Birch, and E. J. Tarbox, “Single-polarization operation of highly birefringent bow-tie optical fibers,” Electron. Lett. 19, 246–247 (1983). [CrossRef]

4.

R. B. Dyott, J. R. Cozens, and D. G. Morris, “Preservation of polarization in optical-fiber waveguides with elliptical cores,” Electron. Lett. 15, 380–382 (1979). [CrossRef]

5.

T. Okoshi, K. Oyamada, M. Nishimura, and H. Yokata, “Side-tunnel-fiber: An approach to polarization-maintaining optical waveguide scheme,” Electron. Lett. 18, 824–826 (1982). [CrossRef]

6.

T. Okoshi, “Single-polarization single mode optical fibers,” IEEE J. Quantum. Electron. 17, 879–884 (1981). [CrossRef]

7.

A. Ortigosa-Blanch, J. C. Knight, W. J. Wadsworth, J. Arriaga, B. J. Mangan, T. A Birks, and P. St. J. Russell, “Highly birefringent photonic crystal fibers,” Opt. Lett. 25, 1325–1327 (2000). [CrossRef]

8.

S. B. Libori, J. Broeng, E. Knudsen, A. Bjarklev, and H. R. Simomsen, “High-birefringent photonic crystal fiber,” in Proc. Optical Fiber Conference (OFC)2001, paper TuM2.

9.

T. P. Hansen, J. Broeng, E. B. Libori, E. Knudsen, A. Bjarklev, J. R. Jensen, and H. Simonsen, “Highly birefringent index-guiding photonic crystal fibers,” IEEE Photon. Tech. Lett. 13, 588–590 (2001). [CrossRef]

10.

K. Suzuki, H. Kubota, and S. Kawanishi, “Optical properties of a low-loss polarization-maintaining photonic crystal fiber,” Opt. Express 9, 676–680 (2001). [CrossRef] [PubMed]

11.

J. Ju, W. Jin, and M.S. Demokan, “Properties of a highly birefringent photonic crystal fiber,” IEEE Photon. Technol. Lett. 15, 1291–1293 (2003). [CrossRef]

12.

K. Saitoh and M. Koshiba, “Photonic bandgap fibers with high birefringence,” IEEE Photon. Technol. Lett. 14, 1291–1293 (2002). [CrossRef]

13.

G. Bouwmans, F. Luan, J. C. Knight, P. St. Russell, L. Farr, B. J. Mangan, and H. Sabert, “Properties of a hollow-core photonic bandgap fiber at 850nm wavelength,” Opt. Express 14, 1613–1620 (2003). [CrossRef]

14.

K. Kikuchi and T. Okoshi, “Wavelength-sweeping technique for measuring the beat length of linearly birefringent optical fibers,” Opt. Lett. 8, 122–124 (1983) [CrossRef] [PubMed]

15.

S. C. Rashleigh, “Measurement of fiber birefringence by wavelength scanning: effect of dispersion”, Optics Leters 8, 336–338, (1983) [CrossRef]

16.

J. R. Folkenberg, M. D. Nielsen, N. A. Mortensen, C. Jakobsen, and H. R. Simonsen, “Polarization maintaining large mode area photonic crystal fiber,” Opt. Express 8, 956–960 (2004) [CrossRef]

17.

C. D. Poole and J. Nagel, “Polarization effects in lightwave systems”, Chapter 6 of Optical Fiber Telecommunications IIIA, Academic Press (1997)

18.

B. L. Heffner, “Automated measurement of polarization mode dispersion using Jones matrix eigenanalysis,” IEEE Photon. Technol. Lett. 4, 1066–1069 (1992) [CrossRef]

OCIS Codes
(060.2310) Fiber optics and optical communications : Fiber optics
(060.2400) Fiber optics and optical communications : Fiber properties

ToC Category:
Research Papers

History
Original Manuscript: July 12, 2004
Revised Manuscript: July 30, 2004
Published: August 9, 2004

Citation
Xin Chen, Ming-Jun Li, Natesan Venkataraman, Michael Gallagher, William Wood, Alana Crowley, Joel Carberry, Luis Zenteno, and Karl Koch, "Highly birefringent hollow-core photonic bandgap fiber," Opt. Express 12, 3888-3893 (2004)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-12-16-3888


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References

  1. J. Noda, K. Okamoto, and Y. Sasaki, ???Polarization-maintaining fibers and their applications,??? J. Lightwave Technol. 4, 1071-1089 (1986) [CrossRef]
  2. T. Hosaka, K. Okamoto, T. Miya, Y. Sasaki, and T. Edahiro, ???Low-loss single-polarization fibers with asymmetrical strain birefringence,??? Electron. Lett. 17, 530-531 (1981). [CrossRef]
  3. M. P. Varnham, D. N. Payne, R. D. Birch, and E. J. Tarbox, ???Single-polarization operation of highly birefringent bow-tie optical fibers,??? Electron. Lett. 19, 246-247 (1983). [CrossRef]
  4. R. B. Dyott, J. R. Cozens, and D. G. Morris, ???Preservation of polarization in optical-fiber waveguides with elliptical cores,??? Electron. Lett. 15, 380-382 (1979). [CrossRef]
  5. T. Okoshi, K. Oyamada, M. Nishimura, and H. Yokata, ???Side-tunnel-fiber: An approach to polarizationmaintaining optical waveguide scheme,??? Electron. Lett. 18, 824-826 (1982). [CrossRef]
  6. T. Okoshi, ???Single-polarization single mode optical fibers,??? IEEE J. Quantum. Electron. 17, 879-884 (1981). [CrossRef]
  7. A. Ortigosa-Blanch, J. C. Knight, W. J. Wadsworth, J. Arriaga, B. J. Mangan, T. A Birks, and P. St. J. Russell, ???Highly birefringent photonic crystal fibers,??? Opt. Lett. 25, 1325-1327 (2000). [CrossRef]
  8. S. B. Libori, J. Broeng, E. Knudsen, A. Bjarklev, and H. R. Simomsen, ???High-birefringent photonic crystal fiber,??? in Proc. Optical Fiber Conference (OFC) 2001, paper TuM2.
  9. T. P. Hansen, J. Broeng, E. B. Libori, E. Knudsen, A. Bjarklev, J. R. Jensen, and H. Simonsen, ???Highly birefringent index-guiding photonic crystal fibers,??? IEEE Photon. Tech. Lett. 13, 588-590 (2001). [CrossRef]
  10. K. Suzuki, H. Kubota, S. Kawanishi, ???Optical properties of a low-loss polarization-maintaining photonic crystal fiber,??? Opt. Express 9, 676-680 (2001). [CrossRef] [PubMed]
  11. J. Ju, W. Jin, and M.S. Demokan, ???Properties of a highly birefringent photonic crystal fiber,??? IEEE Photon. Technol. Lett. 15, 1291-1293 (2003). [CrossRef]
  12. K. Saitoh and M. Koshiba, "Photonic bandgap fibers with high birefringence,??? IEEE Photon. Technol. Lett. 14, 1291-1293 (2002). [CrossRef]
  13. G. Bouwmans, F. Luan, J. C. Knight, P. St. Russell, L. Farr, B. J. Mangan, H. Sabert, ???Properties of a hollow-core photonic bandgap fiber at 850nm wavelength,??? Opt. Express 14, 1613-1620 (2003). [CrossRef]
  14. K. Kikuchi and T. Okoshi, ???Wavelength-sweeping technique for measuring the beat length of linearly birefringent optical fibers,??? Opt. Lett. 8, 122-124 (1983) [CrossRef] [PubMed]
  15. S. C. Rashleigh, ???Measurement of fiber birefringence by wavelength scanning: effect of dispersion,??? Opt. Lett. 8, 336-338, (1983) [CrossRef]
  16. J. R. Folkenberg, M. D. Nielsen, N. A. Mortensen, C. Jakobsen, and H. R. Simonsen, "Polarization maintaining large mode area photonic crystal fiber,??? Opt. Express 8, 956-960 (2004) [CrossRef]
  17. C. D. Poole, and J. Nagel, ???Polarization effects in lightwave systems,??? Chapter 6 of Optical Fiber Telecommunications IIIA, Academic Press (1997)
  18. B. L. Heffner, ???Automated measurement of polarization mode dispersion using Jones matrix eigenanalysis,??? IEEE Photon. Technol. Lett. 4, 1066-1069 (1992) [CrossRef]

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