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RESEARCH OF THE FEATURES OF MANDELSTAM - BRILLOUIN BACKSCATTERING IN OPTICAL FIBERS OF VARIOUS TYPES
DOI 10.24411/2072-8735-2018-10216
Igor V. Bogachkov,
Omsk State Technical University (OmSTU), Omsk, Russia, bogachkov@mail.ru
Keywords: optical fiber, strain, Mandelstam - Brillouin backscatter, spectrum profile, Brillouin reflectometry.
Investigation results of capabilities of the Mandelstam - Brillouin scatter in various types of optical fibers (OFs) by using Brillouin traces are demonstrated in this article.
At present many various types of optical fibers (OFs) have been developed, each of which is optimized to solve certain problems.
A dispersion-shifted single mode fiber (DSF) is applied in long-range fiber optical communication lines (FOCL). A frequency behavior of the DSF dispersion is shifted so that the minimum ("zero") dispersion is observed near wavelength (X) 1.55 ^m. (A single-mode OF- G.652 has the minimum dispersion around X = 1.31 ^m). DSF have proven themselves both in attenuation rate and transmission capacity. However, it is known that the use of these OFs in fiber optical communication lines with wavelength division multiplexing (WDM) has been subjected to nonlinear effects. This led to the appearance of non-zero dispersion-shifted fiber (NZDSF) optimized particularly for long-range WDM systems. The "zero"-dispersion point is located before the fiber transparency "window" X = 1.55 ^m in the NZDSF, but there are types with negative dispersion, where this point is placed behind the fiber transparency "window" X = 1.55 ^m.
A timely location of mechanically stressed sections in the OF laid in the optical cables (OC) is a major objective in an early OF diagnostics.
To identify the fiber sections with enhanced strain and changed temperature is applied the Brillouin reflectometry method, which is taken as a basis for Brillouin optical time domain reflectometer (BOTDR). BOTDR supply accurate information on a distribution of a strain degree along OF length, and then allow the degradation of the OF to be forecast.
The Brillouin traces for optical fibers with heated and cooled light-guide segments are given. The changes in the capabilities of the optical fibers under test are evaluated.
The OFs of various manufacturers with similar optical capabilities have a different shape of the MBBS profile. The database of MBBS profiles of OFs of various types and manufacturers enables the OFs in the FOCL to be classified, as well as the "problem" segments to be identified.
The work was performed with the financial support of the Ministry of Education and Science of the Russian Federation within the scope of the base part of a State Assignment within the sphere of scientific activity (Project No. 8.9334.2017/8.9).
Information about author:
Igor V. Bogachkov, Associate professor (docent) of "Communication means and information security" department of Omsk State Technical University (OmSTU), Omsk, Russia
Для цитирования:
Богачков И.В. Изучение особенностей рассеяния Мандельштама - Бриллюэна в оптических волокнах различных видов // T-Comm: Телекоммуникации и транспорт. 2019. Том 13. №1. С. 60-65.
For citation:
Bogachkov I.V. (2019). Research of the features of Mandelstam - Brillouin backscattering in optical fibers of various types. T-Comm, vol. 13, no.1, рр. 60-65.
At present many various types of optical fibers (OFs) have been developed, each of which is optimized to solve certain problems [1-7].
For instance, a dispersion-shifted single mode fiber (G.653, DSP) is applied in long-range fiber optical communication lines (FOCL). A single-mode optical fiber has the minimum dispersion around X - 1.31 nm, and the minimum attenuation is about X = 1.55 pm. A frcqucney behavior of the DSF dispersion is shifted so that the minimum ("zero") dispersion falls within the fiber transparency "window" X = 1.55 jim [2, 3 J. These OFs have proven themselves both in attenuation rate and transmission capacity, However, it is known that the use of these OFs in fiber optical communication lines with wavelength division multiplexing (WDM) has been subjected to nonlinear effects.
This led to the appearance of non-zero dispersion-shifted fiber (G.655, NZDSF) optimized particularly for long-range WDM systems |4-7]. The zero dispersion point is located before the fiber transparency "window" X = 1.55 ¿im in the NZDSF, but there are types with negative dispersion, where this point is placed behind the fiber transparency "window" X- 1.55 jim.
A timely location of mechanically stressed segments in an OF laid in the optical cables (OC) is a major objective in an early OF diagnostics [1, 5, 7]. Note that the enhanced strain of the OF affects the OC life time. To ensure a long life lime of the OC (at least 25 years), the OF strain should not exceed 0.2 %. If the strain of OF increases to 0.45 %, the probability 50% ofOF breakout appears during the life time 11, 5, 8].
To identity the segments of the OFs with enhanced strain and changed temperature the Brillouin reflectometry method is applied [3 - 101. The Brillouin reflectometry method is taken as a basis for performance of Brillouin optical time domain refiectometer (BOTDR) and Brillouin optical time domain analyzer (BOTDA), which supply accurate information on a distribution of a strain degree along OF length, and then allow the degradation and breakout of the OF to be forecast 11 - 5, 8].
The advantage of the Brillouin reflectometry method is the monitoring of mechanical stresses of OFs with the possibility of spatial localization of "problem" OF segments. BOTDR is enough to connect to one end of the OF, w hich enables the measurements in the construction and operation of the OK to be carried out fl —5].
The capabilities of the OF core can be varied within certain limits depending on the types and concentration of alloying elements, which will affect the value fBand the MBBS profile:
n = 1.458(1 (l)
p = 2200 {1 + 6.4 ■ 10"1 ivG.0 - 3.4 ■ 10"3 wr), (2)
= 5.944 (1 - 7.2 -10~: - 2.7 -10~2 wF), (3)
% = 3.749 (1-6.4-10"„ - 2.7 -10"2 wy), (4)
where n is the refractive index of the medium, (km/s) is the longitudinal hyperacoustic velocity, (km/s) is the transverse (shear) hyperacoustic velocity, wqo is the concentration (%) of germanium oxide (GeO?), is the concentration (%) of fluorine [6],
The "Corning ClearCurve LBL" OF (LBL) is an OF G.652.D with improved flexural capabilities. This OF is designed to replace the OF G.657.A2/B2 in order to have compatibility with OF of various types with good bending capabilities.
The "Corning LEAF" (LEAF) OF is a non-zero dispersion-shifted fiber (NZDSF, G.655) with low dispersion and losses.
The "Coming SMF-28 Ultra" OK (ULTRA) is an OF G.652.D with low losses and improved bending capabilities. This OF is made to replace the OF G.657.A1 with good bending capabilities and certain welding problems with other OF types.
The Brillouin reflectometry method is premised on the analysis of the Mandelstam -■ Brillouin backseafter spectrum (MBBS) in the light-guide which can be seen when the increased radiation is launched into the OF. The components of the MBBS have the frequency shift by a value proportional to the OF strain and its temperature. Analyzing the distribution of the MBBS along the light-guide and estimating the Brillouin frequency shift (the frequency of MBBS maximum), one can obtain a distribution pattern of strains in the OF [4-12].
The structure of various OF types consists of several layers, the physical capabilities of which are different. Researches have shown that the /B is determined as
Л = 1 c = 2 /лг' (5}
where fL is the laser frequency Оч. is the wavelength), v^ is the effective velocity of hyperacoustic wave, and is the effective refractive index of the medium, с is the light velocity in the vacuum.
The MBS components as a function of temperature is linear if the condition is realized as shown in Eq. (6).
hfe«kBT, (6)
where h is the Planck constant (A = 6.63- 10"J4 J s), kii is the Boltzmann constant (kB = 1.38-10 2> J/K), T is the absolute temperature (K), after the substitution the equation is as following:
fB<< U-10'T.
(?)
Taking into account that fg in an OF is not more than tens of GHz, the dependence offg on temperature can be considered linear even at very low temperatures.
For single-mode OF (G.652) ().L = 1.55 jim) the temperature dependence/s(/o) is taken as following: 1 MHz per 1°C [2, 6, 8].
The Brillouin frequency shift (fB) as a function of the OF temperature (/°) is characterized by a linear dependence as [1-6]:
/i«°) = + (8) where Cf is the linearization index depending on ki and Young's
modulus (sy), fa is the initial (for example, a room temperature) temperature, fgo is the initial value of (j\w = /¿(/0)).
Using the fg (/°) the strain of the OF (.vK) can be calculated [1-6]:
.f„ in '/,„-'
Cc • (9)
/0
For single-mode OF (G.652) (A;. = 1.55 ¡im) the dependence 0f/fl on sL(%) is given as: 490 Ml Iz by 1% [8-12].
Experimental researches using the BOTDR "Ando AO 8603" with the assistance of JSC "Moskabel-Fujikura" (Moscow) and "Incab" Ltd. (Perm) were made to study the capabilities of the MBBS in the OFs of various types such as LBL, LF,AF h ULTRA under the influence of different factors.
In experimental researches, the results of which are presented below, the light-guide is composed of "Coming" OF: the OF-G.652 (the compensation coil) is welded to the LBL, which in turn is welded to the LEAF, then the connection to the ULTRA follows, which is welded to the EDF (the erbium-doped fiber). In these experiments, the EDF is used only as an artificial load,
Ss(t°) =
7ТЛ
T-Comm Vol.13. #1-2019
The graphs for G.652, G.657, LBL and ULTRA are located nearly. The LEAF graph is close to the graph of another type of "NZDSF.
Mf), GHz - ">.657..
.--TIJS
"G.657
LE — _____
r —"" DSF, "Panda' V
G.652
LBL
ULTRA
G.657
LEAF NZDSF
C, °C
Fift. 8. Temperature dependences for the studied OFs
The Brillouin reflectometry method allows operators to carry out the early diagnostics of the OFs and identify the OF segments with modified temperature. The application of the BOTDR improves the efficiency of monitoring systems for the OFs [1-3].
The OFs of various manufacturers with similar optical capabilities have a different shape of the MBBS profile.
The database of MBBS profiles of OFs of various types and manufacturers enables the OFs in the FOCL to be classified, as well as the "problem" segments to be identified [14, 15].
The article has been prepared with the financial assistance of the Ministry of Education and Science of the Russian Federation within the scope of the base part of a State Assignment within the sphere of scientific work (Project No. 8.9334.2017/8.9).
The author would like to thank CJSC "Moskabel-Fujikura" (Moscow) and "Incab" (Perm) Ltd. for the help in performing these tests.
References
1. Bogachkov I.V. (2015). Research of influence of the optical fibers strain degree on the Brillonin back scattering characteristics. International Siberian Conference on Control and Communications (S1BC0N-2Q15), Omsk, pp. 1-6.
2. Bogachkov I.V. (2017). Temperature Dependences of Mandct-stam - Brillouin Back scatter Spectrum in Optical Fibers of Various
Types, Systems of Signal Synchronization. Generating and Processing in Telecommunications (SINKHROINFO-20I7). Proceedings, Kazan, pp. 1-6.
3. Bogachkov I.V., Gorlov N.I. (2016). Researches of Strain Characteristics of Dispersion-Shifted Optical Fibers. 13th International Conference on Actual Problems of Electronic Instrument Engineering Proceedings(APEIE-20l6). Proceedings, Novosibirsk, vol. I, p. 1, pp. 169-174.
4. Bogachkov I.V. (2016). Experimental Researches of Brillouin Backscatter Spectrum in Non Zero Dispersion-Shifted Optical Fibers at Longitudinal Stretching Forces. Dynamics of Systems, Mechanisms and Machines fDynamics—2016). Proceedings, Omsk, pp. 1-5.
5. BOTDR Measurement Techniques and Brillouin Backscatter Characteristics of Corning Single-Mode Optical Fibers. http://www.corning.com/media/worldwide/coc/documents/Fibcr/RC-%20White%20Papers/WP-General/WP4259_01-15.pdf.
6. Koyamada Y., Salo S., Nakamura S., Sotobayaslii II., Chujo W. (2004). Simulating and designing Brillouin gain spectrum in singlemode libers. Lightwave Techno!., vol. 22, pp. 631-639.
7. Liu X. (2011). Characterization of Brillouin Scattering Spectrum in LEAF fiber. University ofOttawa. 102 p.
8. Bao X., Chen L. (2011). Recent Progress in Brillouin Scattering Based Fiber Sensors. Sensors, vol. 11, pp. 4152-4187.
9. Bogachkov I.V. (2016). Experimental Researches of Temperature Dependences of Brillouin Backscatter Spectrum in Optical Kibers of Various Types. Dynamics of Systems, Mechanisms and Machines (Dynamics-2016). Proceedings, Omsk, pp. 1-7,
10. Horiguchi T., Kurashima T., Koyamada Y. (1992). Measurement of temperature and strain distribuiion by Brillouin frequency shift in silica optical fibers. Distributed and Multiplexed Fiber Optic Sensors, vol. 1797, pp. 2-13.
11. Bogachkov I.V., Gorlov N.L (2016). Researches of the influence of temperature changes in optical fibers on the Brillouin back scattering spectrum. 13th International Conference on Actual Problems of Electronic Instrument Engineering (APEIE-2016). Proceedings, Novosibirsk, vol. 1, pp. 157-161.
12. Parker T„ Farhadiroushan M., Handerck V„ Rogers A. (1997). Temperature and strain dependence of the power level and frequency of spontaneous Brillouin scattering in optical fibers. Optics letters, vol. 26, N. 11, pp. 787-789.
13. Belal M., Newson T.P. (2012). Experimental Examination of the Variation of the Spontaneous Brillouin Power and Frequency Coefficients Llnder the Combined Influence of Temperature and Strain. Journal of Lightwave Technology, vol. 30, N. 8, pp. 1250-1255.
14. Bogachkov I.V. (2018). A Classification of Optical Fibers Types on the Characteristics of the Mandelstam - Brillouin Backscatter Spectrum, IEEE Ural Symposium on Biomedical Engineering. Radioelectronics and Information Technology (USBERE1T-2018) -Proceedings, Ekaterinburg, pp. 308-312.
15. Bogachkov I.V. (2018), Detection of initial level of Brillouin frequency shift in optical tlbres of different types. Journal of Physics: Conference Series, vol. 1015 (2018), pp. 1-6.
ИЗУЧЕНИЕ ОСОБЕННОСТЕЙ РАССЕЯНИЯ МАНДЕЛЬШТАМА - БРИЛЛЮЭНА В ОПТИЧЕСКИХ ВОЛОКНАХ РАЗЛИЧНЫХ ВИДОВ
Богачков Игорь Викторович, Омский государственный техническийуниверситет, Омск, Россия, bogachkov@mail.ru
Работа выполнена при финансовой поддержке Министерства образования и науки Российской Федерации в рамках базовой части государственного задания в сфере научной деятельности (проект № 8.9334.2017/8.9)
Аннотация
Приведены результаты исследований характеристик спектра рассеяния Мандельштама - Бриллюэна (СРМБ) в оптических волокнах (ОВ) различных видов по бриллюэновским рефлектограммам. В настоящее время разработано множество разновидностей ОВ, каждая из которых оптимизирована для решения определённых задач. Одномодовые ОВ со смещённой дисперсией (DSF) нашли распространение в протяженных волоконно-оптических линиях связи. В DSF частотная характеристика дисперсии смещена так, что минимальная ("нулевая") дисперсия попадает в "окно" X = 1.55 мкм, в то время как у обычного ОВ (G.652) минимальная дисперсия наблюдается около X = 1.31 мкм. DSF хорошо зарекомендовали себя как по удельному затуханию, так и по пропускной способности. Однако известно, что применение этих ОВ в оптоволоконных системах со спектральным уплотнением (WDM) натолкнулось на трудности, связанные с проявлением нелинейных эффектов. Это привело к появлению одномодовых ОВ с ненулевой смещенной дисперсией (NZDSF), оптимизированных именно для протяженных WDM-систем. В NZDSF точка нулевой дисперсии располагается до "окна прозрачности" X = 1.55 мкм, но есть разновидности с отрицательной дисперсией, в которых эта точка располагается за "окном прозрачности" X = 1.55 мкм. Важной задачей ранней диагностики ОВ является своевременное обнаружение механически напряжённых участков в ОВ, находящихся в оптических кабелях (ОК). Повышенное натяжение ОВ влияет на долговечность ОК. Для обнаружения участков ОВ с повышенным натяжением и с изменённой температурой применяется метод бриллюэновской рефлектометрии, который положен в основу работы бриллюэновских рефлектометров (BOTDR), которые способны предоставить точную информацию о распределении степени натяжения ОВ вдоль его длины, а на основе этой информации позволяют прогнозировать деградацию и обрыв ОВ. Приведены бриллюэновские рефлектограммы для ОВ при нагревании и охлаждении их участков. Дана оценка изменений характеристик исследуемых ОВ, приведены их сравнительные температурные графики. ОВ разных производителей при схожих оптических характеристиках имеют разную форму профиля СРМБ. Наличие базы данных профилей СРМБ волокон различных типов и производителей позволяет классифицировать ОВ в ВОЛС, а также обнаруживать "проблемные" участки.
Ключевые слова: оптическое волокно, натяжение, рассеяние Мандельштама — Бриллюэна, профиль спектра, бриллюэновская рефлектометрия. Литература
1. Богачков И.В. Исследования характеристик рассеяния Мандельштама - Бриллюэна в оптических волокнах с различными законами дисперсии // T-Comm: Телекоммуникации и транспорт, 2016. Том 10. № 11. С. 40-45.
2. Богачков И.В. Температурные зависимости спектра рассеяния Мандельштама - Бриллюэна в оптических волокнах различных типов // Системы синхронизации, формирования и обработки сигналов, 2017. Том 8. №1. С. 8-11.
3. Богачков И.В., Горлов Н.И. Экспериментальные исследования спектра бриллюэновского рассеяния в оптических волокнах со смещённой дисперсией // Вестник СибГУТИ. Новосибирск: Изд-во СибГУТИ, 2017. Вып. 2 (38). С. 17-25.
4. Богачков И.В. Экспериментальные исследования спектра бриллюэновского рассеяния в оптических волокнах с ненулевой смещённой дисперсией при продольных растягивающих силах // Динамика систем, механизмов и машин. Омск: Изд-во ОмГТУ, 2016. №4. С. 166-171.
5. BOTDR Measurement Techniques and Brillouin Backscatter Characteristics of Corning Single-Mode Optical Fibers: http://www.corning.com/media/worldwide/coc/documents/Fiber/RC-%20White%20Papers/WP-General/WP4259_0l-l5.pdf.
6. Koyamada Y., Sato S., Nakamura S., Sotobayashi H., Chujo W. Simulating and designing Brillouin gain spectrum in single-mode fibers // Lightwave Technol., 2004.Vol. 22, pp. 631-639.
7. Liu X. Characterization of Brillouin Scattering Spectrum in LEAF fiber. University of Ottawa, 2011. 102 p.
8. Bao X., Chen L. Recent Progress in Brillouin Scattering Based Fiber Sensors // Sensors, 2011. Vol. 11, pp. 4152-4187.
9. Богачков И.В., Горлов Н.И. Обнаружение участков с измененной температурой волоконно-оптических линий связи методом бриллюэновской рефлектометрии // Вестник СибГУТИ, 2015. Вып. 4 (32). С. 74-81.
10. Horiguchi T., Kurashima T., Koyamada Y. Measurement of temperature and strain distribution by Brillouin frequency shift in silica optical fibers // Distributed and Multiplexed Fiber Optic Sensors, 1992. Vol. 1797, pp. 2-13.
11. Богачков И.В., Горлов Н.И. Экспериментальные исследования влияния температуры на спектр бриллюэновского рассеяния и характеристики оптических волокон // Вестник СибГУТИ. Новосибирск: Изд-во СибГУТИ, 2015. Вып. 4 (32). С. 3-12.
12. Parker T., Farhadiroushan M., Handerek V., Rogers A. Temperature and strain dependence of the power level and frequency of spontaneous Brillouin scattering in optical fibers // Optics letters, 1997. Vol. 26, No. 11, pp. 787-789.
13. BelalM., Newson T.P. Experimental Examination of the Variation of the Spontaneous Brillouin Power and Frequency Coefficients Under the Combined Influence of Temperature and Strain // Journal of Lightwave Technology, 2012. Vol. 30. No. 8, pp. 1250-1255.
14. Богачков И.В., Трухина А.И., Иниватов Д.П., Киреев А.П., Горлов Н.И. Классификация оптических волокон по профилю спектра рассеяния Мандельштама - Бриллюэна // Динамика систем, механизмов и машин. Омск: Изд-во ОмГТУ, 2018. Т. 6. № 4. С. 96-100.
15. Bogachkov I.V. Detection of initial level of Brillouin frequency shift in optical fibres of different types // Journal of Physics: Conference Series, 2018, Vol. 1015 (2018). pp. 1-6.
Информация об авторе
Богачков Игорь Викторович, к.т.н., доцент, доцент кафедры "Средства связи и информационная безопасность" Омского государственного технического университета, Омск, Россия
7ТТ
