Source: http://opticjourn.ru/vipuski/1770-opticheskij-zhurnal-tom-85-10-2018.html
Timestamp: 2019-04-26 00:53:57+00:00

Document:
In phase correlation measurement technique of Brillouin dynamic grating sensors, two counter-propagating pump waves are modulated by a pseudo-random bit sequence (PRBS) which applies a random phase shift of either 0 or  with a specified period. In order to define the sensing length and spatial resolution, the shape of the correlation peak has to be found. So far, many methods have been used to demonstrate the phase correlation but, they often require several lengthy and sometimes complicated mathematical assumptions and equations. One of the techniques which has the best reported spatial resolution, is called the time gated phase correlation technique. We introduce a novel method based on matrix solution to show the phase modulation in the phase correlation technique. It is a straightforward and an intuitive pattern to visualize the phase modulation of the pumps and to attain the shape of the phase correlation peaks. Finally, the results of the matrix method are completely consistent with the previous results.
Keywords: distributed fiber sensor, Brillouin dynamic grating (BDG), BDG sensor, matrix method, phase correlation technique.
При проведении измерений сигналов от датчиков на основе динамических бриллюэновских решёток с использованием метода фазовой корреляции производится модуляция двух встречных волн накачки псевдослучайной последовательностью битов с наложением случайного фазового сдвига со значениями 0 или  с заданным периодом. Для определения измеряемого интервала длины и пространственного разрешения необходимо определить форму корреляционного пика. Многие из применяемых для этого способов требуют длительных расчётов и зачастую сложных математических процедур. Одним из обсуждаемых способов, обеспечивающим наилучшее пространственное разрешение, является использование временного стробирования. Предложен новый метод проведения вычислений с использованием матричного решения, основанный на прямом и интуитивно понятном подходе к визуализации процедуры фазовой модуляции волн накачки, позволяющий находить форму корреляционного пика. Показано соответствие полученных результатов с ранее опубликованными.
Ключевые слова: распределенный волоконный датчик, динамическая бриллюэновская решетка, матричный метод, техника фазовой корреляции.
1. Bao X., Chen L. Recent progress in distributed fiber optic sensors // Sensors. 2012. V. 12(7). P. 8601–8639.
2. Minardo A., Coscetta A., Bernini R., Zeni L. Heterodyne slope-assisted Brillouin optical time-domain analysis for dynamic strain measurements // Journal of Optics. 2016. V. 18(2). P. 025606.
3. Song K.Y., Zou W., He Z., Hotate K. All-optical dynamic grating generation based on Brillouin scattering in polarization-maintaining fiber // Opt. Lett. 2008. V. 33(9). P. 926–928.
4. Kim Y.H., Song K.Y. OTDR based on Brillouin dynamic grating in an e-core two-mode fiber for simultaneous measurement of strain and temperature distribution // Optical Fiber Sensors Conference (OFS) in Jeju Island, South Korea. 25 th. IEEE. 2017. V. 10323. P. 103230S-1–4.
5. Bergman A., Langer T., Tur M. Slope-assisted complementary-correlation optical time-domain analysis of Brillouin dynamic gratings for high sensitivity, high spatial resolution, fast and distributed fiber strain sensing // Fifth Asia-Pacific Optical Sensors Conference in Jeju Island, South Korea. International Society for Optics and Photonics. 2015. V. 9655. P. 96550.
6. Song K.Y., Hotate K., Zou W., He Z. Applications of Brillouin dynamic grating to distributed fiber sensors // Journal of Lightwave Technology. 2017. V. 35(16). P. 3268–3280.
7. Choi B.H., Kwon I.B. Brillouin optical correlation analysis system using a simplified frequency-modulated time division method // Optical Engineering. 2014. V. 53(1). P. 016105.
8. Lee H., Mizuno Y., Nakamura K. Measurement sensitivity dependencies on incident power and spatial resolution in slope-assisted Brillouin optical correlation-domain reflectometry // Sensors and Actuators A: Physical. 2017. V. 268. P. 68–71.
9. Chin S., Primerov N., Thévenaz L. Sub-centimeter spatial resolution in distributed fiber sensing based on dynamic Brillouin grating in optical fibers // IEEE Sensors. 2012. V. 12(1). P. 189–194.
10. Teng L., Dong Y., Zhou D., Bao X., Chen L. Distributed hydrostatic pressure sensor using a thin-diameter and polarization-maintaining photonics crystal fiber based on Brillouin dynamic gratings // Optical Fiber Sensors Conference (OFS) in Jeju Island, South Korea. 25 th. IEEE. 2017. V. 10323. P. 103236Q-1–4.
11. Jouybari S.N., Latifi H., Farahi F. Reflection spectrum analysis of stimulated Brillouin scattering dynamic grating // Measurement Science and Technology. 2012. V. 23(8). P. 085203.
12. Song K.Y., Chin S., Primerov N., Thévenaz L. Time-domain distributed fiber sensor with 1 cm spatial resolution based on Brillouin dynamic grating // Journal of Lightwave Technology. 2010. V. 28(14). P. 2062–2067.
13. Denisov A., Soto M.A., Thévenaz L. Going beyond 1000000 resolved points in a Brillouin distributed fiber sensor: theoretical analysis and experimental demonstration // Light: Science & Applications. 2016. V. 5(5). P. e16074.
14. Denisov A. Brillouin dynamic gratings in optical fibers for distributed sensing and advanced optical signal processing // Ph.D. Thesis. École Polytechnique Federale de Lausanne, 2015. P. 17–22.
15. Bergman A., Langer T., abd Tur M. Phase-based, high spatial resolution and distributed, static and dynamic strain sensing using Brillouin dynamic gratings in optical fibers // Optics express. 2017. V. 25(5). P. 5376–5388.
16. Denisov A., Soto M.A., Thévenaz L. 1’000’000 resolved points along a Brillouin distributed fibre sensor // Proc. SPIE. 2014. V. 9157. No. EPFL-CONF-199500. P. 9157D2.
17. Khalid K.S., Zafrullah M., Bilal S.M., Mirza M.A. Simulation and analysis of Gaussian apodized fiber Bragg grating strain sensor // Journal of Optical Technology. 2012. V. 79(10). P. 667–673.
18. Jouybari S.N., Latifi H., Ahmadlou A., Karami M. Spatial resolution enhancement for Brillouin optical time domain analysis distributed sensor by use of correlation peak // SPIE Europe Optical Metrology. International Society for Optics and Photonics. 2009. V. 7389. P. 73892T-1–7.

References: V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V.