The paper presents the results of writing of type I and high-performance type II fiber Bragg gratings in birefringent optical fiber with an elliptical stress cladding by a single 20？ns pulse of KrF excimer laser (248？nm). The gratings’ efficiency produced by a single pulse was up to 100%. Experimental results on visualization of these gratings are presented. 1. Introduction The first fiber Bragg grating (FBG) was obtained in 1978 [1]. About ten years later, FBG was written through a lateral surface of optical fiber for the first time [2]. Nowadays, gratings are becoming more and more widely used. Fiber Bragg gratings written in birefringent optical fibers can be used in creation of sensors for measuring physical quantities [3, 4]. To date, FBGs have been induced in birefringent optical fibers of different types: with elliptical core [5], bow-tie [6], PANDA [7], and internal elliptical cladding [8]. Here we demonstrate the results of FBG writing by a single 20？ns KrF excimer laser pulse in birefringent optical fiber with an elliptical stress cladding, obtained using the technology [9, 10]. This birefringent optical fiber due to its unique properties [11] is being used to create precision interferometric sensors, such as a fiber-optic gyroscope [12]. Special quadrupole winding is used in a fiber-optic gyroscope with the class of accuracy below 0.01？deg/h for temperature drift compensation in the fiber loop, which is the main source of phase noise [12]. To create a fiber-optic gyroscope with class of accuracy 0.01？deg/h and higher, the development of an active system of temperature gradients compensation in the fiber loop is required. Refractive index gratings are being widely used in temperature sensors [13, 14]. So, it is possible to measure temperature gradients inside the gyroscope fiber loop using FBGs array. For creating FBGs array, this birefringent optical fiber with an elliptical stress cladding, obtained using the technology [9, 10] with complex structure [15], which includes a core, a circular isolating cladding, an elliptical stress cladding, and a circular outer cladding, was selected. To enhance the photosensitivity of the fiber the concentration of GeO2 in its core was increased to 16？mol. %. Enhancing the photosensitivity at the stage of preform formation allows you to write the FBG arrays during the drawing process of optical fiber. The disadvantage of this method is an increase in linear optical losses of the fiber. Losses of birefringent optical fiber with an elliptical stress cladding with 16？mol. % GeO2, used in this work, are
References
[1]
K. O. Hill, Y. Fujii, D. C. Johnson, and B. S. Kawasaki, “Photosensitivity in optical fiber waveguides: application to reflection filter fabrication,” Applied Physics Letters, vol. 32, no. 10, pp. 647–649, 1978.
[2]
G. Meltz, W. W. Morey, and W. H. Glenn, “Formation of Bragg gratings in optical fibers by a transverse holographic method,” Optics Letters, vol. 14, no. 15, pp. 823–825, 1989.
[3]
A. Othonos, “Fiber Bragg gratings,” Review of Scientific Instruments, vol. 68, no. 12, pp. 4309–4341, 1997.
[4]
S. Bette, C. Caucheteur, M. Wuilpart, and P. Mégret, “Theoretical and experimental study of differential group delay and polarization dependent loss of Bragg gratings written in birefringent fiber,” Optics Communications, vol. 269, no. 2, pp. 331–337, 2007.
[5]
G. Meltz and W. W. Morey, “Bragg grating formation and germanosilicate fiber photosensitivity,” in International Workshop on Photoinduced Self-Organization Effects in Optical Fiber, vol. 1516 of Proceedings of SPIE, pp. 185–199, Québec, Canada, December 1991.
[6]
P. C. Hill, G. R. Atkins, J. Canning, G. C. Cox, and M. G. Sceats, “Writing and visualization of low-threshold type II Bragg gratings in stressed optical fibers,” Applied Optics, vol. 34, no. 33, pp. 7689–7694, 1995.
[7]
I. Abe, R. E. De Góes, J. L. Fabris et al., “Production and characterization of refractive index gratings in high-birefringence fibre optics,” Optics and Lasers in Engineering, vol. 39, no. 5-6, pp. 537–548, 2003.
[8]
I. Abe, H. J. Kalinowski, R. Nogueira, J. L. Pinto, and O. Fraz？o, “Production and characterisation of Bragg gratings written in high-birefringence fibre optics,” IEE Proceedings—Circuits, Devices and Systems, vol. 150, no. 6, pp. 495–500, 2003.
[9]
M. A. Eron’yan, “Method of fabricating fiber lightguides that maintain the polarization of the radiation,” Russian Patent no. 2155359, 2000.
[10]
S. V. Bureev, K. V. Dukel'skiǐ, M. A. Eron'yan et al., “Processing large blanks of anisotropic single-mode lightguides with elliptical cladding,” Journal of Optical Technology, vol. 74, no. 4, pp. 297–298, 2007.
[11]
S. V. Bureev, I. K. Meshkovski？, E. Yu. Utkin et al., “Minimizing the optical losses in anisotropic single-mode lightguides with elliptical boron germanosilicate cladding,” Journal of Optical Technology, vol. 79, no. 7, pp. 433–436, 2012.
[12]
I. K. Meshkovsky, V. Y. Strigalev, G. B. Deineka, V. G. Peshekhonov, D. V. Volynsky, and A. A. Untilov, “Three-axis fiber-optic gyroscope: development and test results,” Gyroscopy and Navigation, vol. 2, no. 4, pp. 208–213, 2011.
[13]
H. Bartelt, K. Schuster, S. Unger, C. Chojetzki, M. Rothhardt, and I. Latka, “Single-pulse fiber Bragg gratings and specific coatings for use at elevated temperatures,” Applied Optics, vol. 46, no. 17, pp. 3417–3424, 2007.
[14]
Y. Zhan, H. Wu, Q. Yang, S. Xiang, and H. He, “Fiber grating sensors for high-temperature measurement,” Optics and Lasers in Engineering, vol. 46, no. 4, pp. 349–354, 2008.
[15]
A. G. Andreev, I. I. Kryukov, T. V. Mazunina et al., “Increasing the birefringence in anisotropic single-mode fiber lightguides with an elliptical stress cladding,” Journal of Optical Technology, vol. 79, no. 9, pp. 608–609, 2012.
[16]
S. V. Varzhel’, A. V. Kulikov, I. K. Meshkovskii, and V. E. Strigalev, “Recording Bragg gratings in a birefringent optical fiber with a single 20-ns pulse of an excimer laser,” Journal of Optical Technology, vol. 79, no. 4, pp. 257–259, 2012.
[17]
J. Canning, “Fibre gratings and devices for sensors and laser,” Laser & Photonics Reviews, vol. 2, no. 4, pp. 275–289, 2008.
[18]
S. A. Vasil'ev, O. I. Medvedkov, I. G. Korolev, A. S. Bozhkov, A. S. Kurkov, and E. M. Dianov, “Fibre gratings and their applications,” Quantum Electronics, vol. 35, no. 12, pp. 1085–1103, 2005.
[19]
S. V. Varzhel’, A. V. Kulikov, K. A. Konnov, and A. I. Gribaev, “Single excimer pulse writing of Bragg gratings in birefringent optical fiber with an elliptical stress cladding: visualization and thermal annealing of the gratings,” in Proceedings of the Materials of the 5th International Research and Practice Conference, vol. I, pp. 305–310, Munich, Germany, October 2013.
[20]
L. Reekie, J. L. Archambault, and P. S. J. Russell, “100% reflectivity fibre gratings produced by a single excimer laser pulse,” in Proceedings of the Optical Fiber Communication Conference, OSA Technical Digest Series, paper PD14, pp. 327–330, San Jose, Calif, USA, February 1993.
[21]
B. Malo, D. C. Johnson, F. Bilodeau, J. Albert, and K. O. Hill, “Single-excimer-pulse writing of fiber gratings by use of a zero-order nulled phase mask: grating spectral response and visualization of index perturbations,” Optics Letters, vol. 18, no. 15, pp. 1277–1279, 1993.
[22]
S. V. Varzhel’, V. V. Zakharov, G. N. Vinogradova, A. V. Veniaminov, and V. E. Strigalev, “Visualization of type II fiber Bragg gratings Induced in a birefringent fiber with an elliptical stress cladding,” Optics and Spectroscopy, vol. 114, no. 1, pp. 116–119, 2013.
[23]
B. Kouskousis, D. J. Kitcher, S. Collins, A. Roberts, and G. W. Baxter, “Quantitative phase and refractive index analysis of optical fibers using differential interference contrast microscopy,” Applied Optics, vol. 47, no. 28, pp. 5182–5189, 2008.
[24]
N. M. Dragomir, C. Rollinson, S. A. Wade et al., “Nondestructive imaging of a type I optical fiber Bragg grating,” Optics Letters, vol. 28, no. 10, pp. 789–791, 2003.
