Response Characteristic of Twisting Second-Azimuthal-Order Few-Mode Long-Period Fiber Grating

HUANG Xincheng1,2 WU Xiaowen1 GAO Shecheng1 FENG Yuanhua1 LIU Weiping1

(1.Department of Electronics and Engineering, College of Information Science and Technology, Jinan University, Guangzhou, Guangdong, China 510632)
(2.Department of Electronics and Information, Huzhou University Qiuzhen College, Huzhou, Zhejiang Province, China 313000)

【Abstract】This study experimentally and theoretically examines the response characteristic of twisting the second-azimuthal-order few-mode long-period fiber grating (FM-LPFG). The theoretical analysis shows that the twisting responsivity of the coupled resonant wavelength of the high-order FM-LPFG is closely related to the azimuthal order of the grating, namely the twisting responsivity of the resonant wavelength of the second-azimuthal-order FM-LPFG is almost two times larger than that of the first-azimuthal-order FM-LPFG. The twisting-induced phase mismatching leads to the almost linear decay of the intensity of the resonant peak in the transmission spectrum of the grating with the increase in the grating twisting rate in a relatively small twisting-rate domain. This decay rate is inversely related to the value of the phase mismatch. Further, the experimental results show that the twisting responsivity of the resonant wavelength of the second-azimuthal-order FM-LPFG is approximately 1.5 times larger than that of the first-azimuthal-order FM-LPFG, which reaches 0.72 nm· (rad·m−1)−1 and 0.82 nm· (rad·m−1)−1 in the cases of clockwise and counter-clockwise twisting, respectively. The intensity of the resonant peak varies linearly with the increase in the twisting-rate in the small twisting-rate domain, and the linear sensitivities are 0.81 dB· (rad·m−1)−1 and 0.72 dB· (rad·m−1)−1 in the cases of clockwise and counter-clockwise twisting, respectively. However, the corresponding intensity of the resonant peak has the characteristics of small variation amplitude and fluctuation in the large twisting-rate domain, indicating that experimental results are generally in agreement with the theoretical analysis. These twisting response characteristics of the wavelength and intensity of the resonant peak of the second-azimuthal-order FM-LPFG have potential applications in high-precision sensing of twisting mechanical parameters (such as twisting capacity, twisting speed, and acceleration) and simultaneous measurement of multiple parameters in the same monitoring twisting-rate domain.

【Keywords】 optical communications; second-azimuthal-order few-mode long-period fiber grating; twisting; response characteristic; resonant peak ;


【Funds】 National Natural Science Foundation of China (61875076, 61775085, 61865014) Science and Technology Planning Project of Guangdong Province, China (2017B010123005)

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(Translated by WEI JM)


    [1] Ramachandran S, Ghalmi S, Wang Z Y, et al. Band-selection filters with concatenated long-period gratings in few-mode fibers [J]. Optics Letters, 2002, 27 (19): 1678–1680.

    [2] Motoyuki S, Kubota H, Ohashi M, et al. A broadband mode converter from LP01 to LP11 modes based on a long-period fiber grating using a two-mode fiber [C]. //2018 Asia Communications and Photonics Conference (ACP), October 26–29, 2018, Hangzhou, China. New York: IEEE, 2018: 8355942.

    [3] Yang Y. Study on filtering characteristics of chirped long-period fiber grating [J]. Laser & Infrared, 2011, 41 (2): 173–176 (in Chinese).

    [4] Zhang X H, Liu Y G, Wang Z, et al. LP01-LP11a mode converters based on long-period fiber gratings in a two-mode polarization-maintaining photonic crystal fiber [J]. Optics Express, 2018, 26 (6): 7013–7021.

    [5] Xue Y R, Tian P F, Jin W, et al. Superimposed long period gratings based mode converter in few-mode fiber [J]. Acta Physica Sinica, 2019, 68 (5): 054204 (in Chinese).

    [6] Cacciari I, Brenci M, Falciai R, et al. Reproducibility of splicer-based long-period fiber gratings for gain equalization [J]. Optoelectronics Letters, 2007, 3 (3): 203–206.

    [7] Jiang J, Callender C L, Noad J P, et al. Hybrid silica/polymer long period gratings for wavelength filtering and power distribution [J]. Applied Optics, 2009, 48 (26): 4866–4873.

    [8] Ni W J, Lu P, Fu X, et al. Highly sensitive optical fiber curvature and acoustic sensor based on thin core ultralong period fiber grating [J]. IEEE Photonics Journal, 2017, 9 (2): 7100909.

    [9] Wu H, Tang M, Wang M, et al. Few-mode optical fiber based simultaneously distributed curvature and temperature sensing [J]. Optics Express, 2017, 25 (11): 12722–12732.

    [10] Lü R Q, Wang Q, Hu H F, et al. Fabrication and sensing characterization of thermally induced long period fiber gratings in few mode fibers [J]. Optik, 2018, 158: 71–77.

    [11] Guo Y C, Liu Y G, Wang Z, et al. Dual resonance and dual-parameter sensor of few-mode fiber long period grating [J]. Acta Optica Sinica, 2018, 38 (9): 0906003 (in Chinese).

    [12] Deng J, Feng Y H, Gao S C, et al. High sensitivity torsion sensors based on few-mode long-period fiber gratings [J]. Laser & Optoelectronics Progress, 2017, 54 (10): 100602 (in Chinese).

    [13] Budinski V, Donlagic D. Fiber-optic sensors for measurements of torsion, twist and rotation: a review [J]. Sensors, 2017, 17 (3): 443.

    [14] Wang Q L, Sang M, Zhong C H, et al. Refractive index and curvature sensitivity of LPFG inscribed in few-modes fiber [J]. Proceedings of SPIE, 2017, 10464: 1046408.

    [15] Zhang L, Liu Y Q, Cao X B, et al. High sensitivity chiral long-period grating sensors written in the twisted fiber [J]. IEEE Sensors Journal, 2016, 16 (11): 4253–4257.

    [16] Yang K, Liu Y G, Wang Z, et al. Twist sensor based on long period grating and tilted Bragg grating written in few-mode fibers [J]. IEEE Photonics Journal, 2018, 10 (3): 7102708.

    [17] Snyder A W. Coupled-mode theory for optical fibers [J]. Journal of the Optical Society of America, 1972, 62 (11): 1267–1277.

    [18] Reichman D R, Charbonneau P. Mode-coupling theory [J]. Journal of Statistical Mechanics: Theory and Experiment, 2005, 2005 (5): P05013.

    [19] Alexeyev N, Volyar V, Yavorsky A. Optical vortices in twisted optical fibres with torsional stress [J]. Journal of Optics A: Pure and Applied Optics, 2008, 10 (9): 095007.

    [20] Ruan J, Zhang G, Zhang H, et al. Temperature and twist characteristics of cascaded long-period fiber gratings written in polarization-maintaining fibers [J]. Journal of Optics, 2012, 14 (10): 105403.

    [21] Ulrich R, Simon A. Polarization optics of twisted single-mode fibers [J]. Applied Optics, 1979, 18 (13): 2241–2251.

    [22] Yariv A, Yeh P. Photonics: optical electronics in modern communications (the oxford series in electrical and computer engineering) [M]. 6th ed. UK: Oxford University Press, 2006: 232.

    [23] Wu H, Gao S C, Huang B S, et al. All-fiber second-order optical vortex generation based on strong modulated long-period grating in a four-mode fiber [J]. Optics Letters, 2017, 42 (24): 5210–5213.

    [24] Ivanov O V. Propagation and coupling of hybrid modes in twisted fibers [J]. Journal of the Optical Society of America A, 2005, 22 (4): 716–723.

This Article


CN: 31-1339/TN

Vol 46, No. 12, Pages 206-213

December 2019


Article Outline


  • 1 Introduction
  • 2 Basic principle
  • 3 Experiments and analysis
  • 4 Conclusion
  • References