Sensitivity-Enhanced Hot-Wire Anemometer by Using Cladding-Etched Fiber Bragg Grating

Abstract

A sensitivity-enhanced hot-wire anemometer based on a cladding-etched optical fiber Bragg grating (FBG) coated with a layer of silver film and optically heated by using a 1480 nm laser diode is demonstrated. The silver film absorbs the laser power to heat the FBG to a certain high temperature and the airflow cools down the FBG hot-wire with the cooling effect and hence the Bragg wavelength of the FBG is determined by the airflow velocity. Experimental measurement results show that the heating efficiency of the FBG hot wire is improved by 3.8 times in magnitude by etching the fiber cladding from 125 µm down to 73.4 µm, and the achieved airflow velocity sensitivities, under a laser power of 200 mW, are −3 180 pm/(m/s), −889 pm/(m/s), −268 pm/(m/s), and −8.7 pm/(m/s) at different airflow velocities of 0.1 m/s, 0.5 m/s, 1.5 m/s, and 17 m/s, respectively. In comparison, the sensitivities are only −2193 pm/(m/s), −567 pm/(m/s), −161 pm/(m/s), and −4.9 pm/(m/s) for the reference anemometer without cladding etching even at a much higher heating laser power of 530 mW. These results prove that the method by using a cladding-etched FBG to improve sensitivity of FBG-based hot-wire anemometers works and the sensitivity is improved significantly.

Keywords

Fiber Bragg grating / hot-wire anemometer / optical fiber sensors

References

[1] Ligęza P. An investigation of a constant-bandwidth hot-wire anemometer. Flow Measurement and Instrumentation, 2009, 20(3): 116-121.

[2] Silvestri S, Schena E. Micromachined flow sensors in biomedical applications. Micromachines, 2012, 3(2): 225-243.

[3] Gao S, Zhang A P, Tam H Y, Cho L H, Lu C. All-optical fiber anemometer based on laser heated fiber Bragg gratings. Optics Express, 2011, 19(11): 10124-10130.

[4] Chen R, Yan A, Wang Q, Chen K P. Fiber-optic flow sensors for high-temperature environment operation up to 80 °C. Optics Letters, 2014, 39(13): 3966-3969.

[5] Liu G, Hou W, Qiao W, Han M. Fast-response fiber-optic anemometer with temperature self-compensation. Optics Express, 2015, 23(10): 13562-13570.

[6] Gao R, Lu D, Cheng J, Qi Z. Real-time fiber-optic anemometer based on a laser-heated few-layer graphene in an aligned graded-index fiber. Optics Letters, 2017, 42(14): 2703-2706.

[7] Wang F, Duan Y, Lu M, Zhang Y, Jing Z, Sun C, . Linear-response and simple hot-wire fiber-optic anemometer using high-order cladding mode. Optics Express, 2020, 28(18): 27028-27036.

[8] Gao R, Lu D F. Temperature compensated fiber optic anemometer based on graphene-coated elliptical core micro-fiber Bragg grating. Optics Express, 2019, 27(23): 34012-34022.

[9] Zhang J, Dong X, Xu P, Lv D, Yang J, Qin Y. Optical fiber thermal anemometer with light source-heated Fabry-Perot interferometer. Journal of Lightwave Technology, 2022, 40(9): 3010-3015.

[10] Wang F, Duan Y, Lu M, Zhang Y, Jing Z, Sun C, . Fiber-optic hot-wire anemometer with directional response based on symmetry-breaking induced heat transfer mechanism. Journal of Lightwave Technology, 2021, 39(12): 3919-3925.

[11] Liu Z, Wang F, Zhang Y, Jing Z, Peng W. Low-power-consumption fiber-optic anemometer based on long-period grating with SWCNT coating. IEEE Sensors Journal, 2019, 19(7): 2592-2597.

[12] Zhang Y, Wang F, Liu Z, Duan Z, Cui W, Han J, . Fiber-optic anemometer based on single-walled carbon nanotube coated tilted fiber Bragg grating. Optics Express, 2017, 25(20): 24521-24530.

[13] Lee C L, Liu K W, Luo S H, Wu M S, Ma C T. A hot-polymer fiber Fabry-Perot interferometer anemometer for sensing airflow. Sensors, 2017, 17(9): 2015.

[14] Zhao Y, Hu H, Bi D, Yang Y. Research on the optical fiber gas flowmeters based on intermodal interference. Optics and Lasers in Engineering, 2016, 82, 122-126.

[15] Wylie M, Brown A, Colpitts B. Distributed hot-wire anemometry based on Brillouin optical time-domain analysis. Optics Express, 2012, 20(14): 15669-15678.

[16] Cashdollar L J, Chen K P. Fiber Bragg grating flow sensors powered by in-fiber light. IEEE Sensors Journal, 2005, 5(6): 1327-1331.

[17] Jewart C M, McMillen B, Cho S K, Chen K P. X-probe flow sensor using self-powered active fiber Bragg gratings. Sensors and Actuators A: Physical, 2006, 127(1): 63-68.

[18] Caldas P, Jorge P, Rego G, Frazão O, Santos J, Ferreira L, . Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure. Applied Optics, 2011, 50(17): 2738-2743.

[19] Dong X, Zhou Y, Zhou W, Cheng J, Su Z. Compact anemometer using silver-coated fiber Bragg grating. IEEE Photonics Journal, 2012, 4(5): 1381-1386.

[20] Wang X, Dong X, Zhou Y, Ni K, Cheng J, Chen Z. Hot-wire anemometer based on silver-coated fiber Bragg grating assisted by no-core fiber. IEEE Photonics Technology Letters, 2013, 25(24): 2458-2461.

[21] Wang J, Liu Z, Gao S, Zhang A, Shen Y, Tam H. Fiber-optic anemometer based on Bragg grating Inscribed in metal-filled microstructured optical fiber. Journal of Lightwave Technology, 2016, 34(21): 4884-4889.

[22] Berruti G, Vaiano P, Boniello A, Principe S, Quero G, Persiano G, . Highly efficient fiber optic thermal heating device based on turn-around-point long period gratings. Journal of Lightwave Technology, 2022, 40(3): 797-804.

[23] Garcia-Ruiz A, Dominguez-Lopez A, Pastor-Graells J, Martins H, Martin-Lopez S, Gonzalez-Herraez M. Long-range distributed optical fiber hot-wire anemometer based on chirped-pulse ΦOTDR. Optics Express, 2018, 26(1): 463-476.

[24] Kim J Y, Park M J, Lee J H. Effect of Al₂O₃/ZnO nanolaminate by atomic layer deposition (ALD) on p-Si photocathode for photoelectrochemical hydrogen evolution. Science of Advanced Materials, 2015, 7(11): 2492-2495.

[25] Li Z, Wang J, Liu T, Zhao L, Sun T, Grattan K T V. High-sensitivity “hot-wire”-based gas velocity sensor for safe monitoring in mining applications. IEEE Sensors Journal, 2018, 18(24): 10192-10198.

[26] Bruun H. Hot-wire anemometry: principles and signal analysis, 1995, New York: Oxford University Press

[27] Wang X, Dong X, Zhou Y, Li Y, Cheng J, Chen Z. Optical fiber anemometer using silver-coated fiber Bragg grating and bitaper. Sensors and Actuators A: Physical, 2014, 214, 230-233.

[28] Han B, Zhang Y N, Wang X, Yang D, Liu Y, Sun J C, . High-sensitive fiber anemometer based on surface plasmon resonance effect in photonic crystal fiber. IEEE Sensors Journal, 2019, 19(9): 3391-3398.