Refractive index and strain sensitivities of a long period fiber grating

Abstract

A long period fiber grating (LPFG) fabricated upon the all-solid photonic bandgap fiber by CO₂ laser irradiation was investigated, and its resonance wavelength was at 1335.76 nm with a modulation depth of 15 dB and a 3-dB bandwidth of 2.6 nm. We studied its strain, temperature, and index sensor characteristics, the strain sensitivity of 0.992 pm/μɛ was obtained by using linear fit, and the relationship between the refractive index and wavelength obeyed the distribution of quadratic function. Also, we demonstrated its temperature response was relatively insensitive (21.51 pm/°).

Keywords

Long period fiber grating / strain sensors / index sensors

References

[1] Hill K O, Malo B, Bilodeau F, Johnson D C, Albert J. Bragg gratings fabricated in monomode photosensitive optical fiber by UV exposure through a phase mask. Applied Physics Letters, 1993, 62(10): 1035-1037.

[2] Rao Y J. In-fiber Bragg grating sensors. Measurement Science & Technology, 1997, 8(4): 355-375.

[3] Vengsarkar A M, Lemaire P J, Judkins J B, Bhatia V, Erdogan T, Sipe J E. Long-period fiber grating as band-rejection filters. Journal of Lightwave Technology, 1996, 14(1): 58-65.

[4] Wang Y P, Wang D N, Jin W, Rao Y J, Peng G D. Asymmetric long period fiber gratings fabricated by use of CO₂ laser to carve periodic grooves on the optical fiber. Applied Physics Letters, 2006, 89(15): 151105-1-151105-3.

[5] Kondo Y, Nouchi K, Mitsuyu T, Watanabe M, Kazansky P G, Hirao K. Fabrication of long-period fiber gratings by focused irradiation of infrared femtosecond laser pulses. Optics Letters, 1999, 24(10): 646-648.

[6] Wang Y P, Liao C R, Zhong X Y, Zhou J T, Liu Y J, Li Z R, . Long period fiber gratings writing in photonic crystal fber by use of CO₂ laser. Photonic Sensors, 2013, 3(3): 193-201.

[7] Ju J, Jin W. Long period gratings in crystal fibers. Photonic Sensor, 2012, 2(1): 65-70.

[8] Erdogan T. Cladding-mode resonances in short-and long-period fiber grating filters. Journal of the Optical Society of America A, 1997, 14(8): 1760-1773.

[9] Rao Y J, Wang Y P, Ran Z L, Zhu T. Novel fiber-optic sensors based on long-period fiber gratings written by high-frequency CO₂ laser pulses. Journal of Lightwave Technology, 2003, 21(5): 1320-1327.

[10] Villatoro J, Finazzi V, Minkovich V P, Pruneri V, Badenes G. Temperature-insensitive photonic crystal fiber interferometer for absolute strain sensing. Applied Physics Letters, 2007, 91091109, 091109-1-091109-3.

[11] Kim G, Cho T, Hwang K, Lee K, Lee K S, Han Y G, . Strain and temperature sensitivities of an elliptical hollow-core photonic bandgap fiber based on Sagnac interferometer. Optics Express, 2009, 17(4): 2481-2486.

[12] Aref S H, Amezcua-correa R, Carvalho J P, Frazão O, Caldas P, Santos J L, . Modal interferometer based on hollow-core phonic crystal fiber for strain and temperature measurement. Optics Express, 2009, 17(21): 18669-18675.

[13] Zheng J R, Yu Y Q, Ou Z L, Yan P G, Wang J S, Chen X, . Bending characteristics of long period fiber grating fabricated upon all-solid photonic bandgap fiber by CO₂ laser. Optical Engineering, 2013, 52(6): 065002-1-065002-6.

[14] Zheng J R, Yan P G, Yu Y Q, Ou Z L, Wang J S, Chen X, . Temperature and index insensitive strain sensor based on a photonic crystal fiber in line Mach-Zehnder interferometer. Optics Communications, 2013, 297(15): 7-11.

[15] Xuan H, Jin W, Zhang M, Ju J, Liao Y. In-fiber polarimeters based on hollow-core photonic bandgap fibers. Optics Express, 2009, 17(15): 13246-13254.

[16] Zu P, Chan C C, Jin Y, Gong T, Zhang Y, Chen L H, . A temperature-insensitive twist sensor by using low birefringence photonic crystal fiber based Sagnac interferometer. IEEE Photonics Technology Letters, 2011, 23(13): 920-922.

[17] Shi Q, Lv F, Wang Z, Jin L, Hu J J, Liu Z, . Environmentally stable Febry-Pérot-type strain sensor based on hollow core photonic bandgap fiber. IEEE Photonics Technology Letters, 2008, 20(4): 237-239.

[18] Shi Q, Huang Z, Jin L, Li Y, Zhang H, Lu F, . A hollow-core photonic crystal fiber cavity based multiplexed Fabry-Pérot interferometric strain sensor system. IEEE Photonics Technology Letters, 2008, 20(15): 1329-1331.