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THE INFLUENCE OF PHASE SELF-MODULATION AND PHASE CROSS-MODULATION FOR THE TRANSMISSION
OF SIGNALS OPTICAL FIBER
The limitation of optical technology is achieved, the requirements for optical fibers and optical components becomes specialized for a specific use. Terrabyte and petabyte speed require very broadband optical fibers and the same components. The new single mode optical fibers should have the required characteristics: chromatic dispersion, polarization mode dispersion, optical nonlinearities, optical bandwidth, which has a special application, and architecture
Long distance constraint are non-linear effects such as Phase self-modulation, cross-modulation, and four wave mixing generating a signal distortion and a transient conversation that can't be removed at the receiver. Chromatic(CD) and polarization mode(PMD) dispersion generate intersymbol distortion. Nonlinear effects limit the transmission and depend on a number of factors: speed, optical power, optical fiber, modulation format. To reduce or to limit this impact can choice Single mode OB, choice of modulation format, optical phase configuration, dispersion, solution, electronic equipment. It should be noted that the bit error rate increases with increase in input S power due to the nonlinearity of the CQ.
The phase self-modulation (FSM), phase cross- modulation(FCM), in cooperation with the chromatic(CD) and polarization mode (PMD) dispersions at high speeds and at high extensions the Optical Line could have a negative impact on the transmission of signals and positive impact. The article discusses the impact of these nonlinear effects on the transmission and gives a decision on their account.
Eduard L. Portnov,
MTUCI, Moscow, Russia, lc@mtuci.ru
Jocelin Rabenandrasana,
MTUCI, Moscow, Russia
Keywords: optical fibers, nonlinear effects, phase self-modulation, phase cross-modulation, chromatic dispersion, polarization mode dispersion.
Information about authors:
Eduard L. Portnov, Head of the Department DTE, Doctor of Technical Sciences, Professor, MTUCI, Moscow, Russia Jocelin Rabenandrasana, Graduate student, MTUCI, Moscow, Russia
Для цитирования:
Портнов Э.Л., Рабенандрасана Ж. Определение влияния фазовой самомодуляции и кросс-модуляции на передачу сигналов по оптическому волокну // T-Comm: Телекоммуникации и транспорт. 2017. Том 11. №11. С. 80-83.
For citation:
Portnov E.L., Rabenandrasana J. (2017). The influence of phase self-modulation and phase cross-modulation for the transmission of signals optical fiber. T-Comm, vol. 1 1, no.1 1, рр. 80-83.
The limitation of optical technology is achieved, the requirements for optical fibers and optical components becomes specialized for a specific use. Terrabyte and petabyte speed require very broadband optical fibers and the same components [1]. The new Single mode OB should have the required characteristics: chromatic dispersion, polarization mode dispersion, optical non linearities, optical bandwidth, which is of particular use, and architecture. Increasing and developing FOTS-MS, broadband requires not only Single mode OB, but also the development of high-speed electronics and different techniques like DWDM, hTDM, and the combination of DWDM-TDM to minimize the cost of transmission on the channel. The development of electronic components for multiplexing, demultiplexing, modulation and the transition to optica! system technology leads to an increase transmission speeds to 100 GB/s 400r6nr/s and above. Modem development is focused on broadband DWDM and ultraline transport. This requires the creation of new modulation techniques, broadband amplification, broadband dispersion compensation and the use of pre-emptive error correction. S is ail integral component of the required framework.
Fiber parameters arc the basis for the selection of most of these components such as amplifiers and compensators. When using a DWDM system the Single mode OB parameters determine the solutions of dispersion, nonlinearity, distributed amplification, spectral losses and polarization mode dispersion.
Long distance constraint are non-linear effects such as phase self-modulation, cross-modulation, and four wave mixing, which generate signal distortions and transition the conversation thai could not be compensated at the receiver. Chromatic and polarization mode dispersion generating intersymbol distortion. Parameters CD (PS/nm.km) S (PS/nm2.kin), Aeff (|¿m2) and spectral attenuation (dB/km) can be optimized for specific system architectures.
From a large number of nonlinear effects Kerr effect is manifested in the change of refractive index under the action of the square of the electric field.
The refractive index of the optical fiber is slightly dependent on the optical power according to the relationship [1 j:
n (ffl,P)=n_0 (co)+I n_2=n_0 (to)+n_2 P/A_"eff'
where nO (□) is the linear refractive index of silica, n2 is the refractive index depending on intensity, and I = P/Aeff is the effective intensity of the environment. A typical value of n2 is 2.6 l20 m2/W. This number takes into account the average state of polarization of a light beam propagating in the fiber.
The dependence of refractive index on the intensity leads to three main effects that tend to significantly degrade the signal integrity. Self-modulation of a phase is because the intensity profile of optical pulses of one channel affects the refractive index profile and thus the centre of the pulse with higher intensity is distributed more slowly than ihc edges of the pulses with lower intensity. When one considers the many WDM channels, jointly propagating in the fiber, photons from channels with the 2nd to N-th can distort the profile indicator, which is applied to channel I. This distortion metric FKM is transmitted as a distortion speed of the light llux. The optical intensity propagating through the fiber, is the square of the electric field. When squared, the sum of the various fields, it appears that members are multiplied with the beat in different amounts and different
frequencies of the original signal. If the WDM channel exists in one frequency beating FWM, the beating of coherently interfere with another WDM channel and can potentially destroy data. The nonlinearity can be controlled with careful introduction and uniform distribution of X A, possibly with fixed and/or custom compensation [3].
Nonlinear effects limit the transmission and depend on a number of factors: speed, optical power, optical fiber, modulation formal.
Non-linear distortion reduces the ratio signal/noise at the receiver and does not allow to increase Renal. n2, D, Ac if determine the nonlinear transient conversation is created for the considered distances between the DWDM channels 11 J.
Aeff - 27tn3/yA. y = 27Uh/X,A3(]x}), here ri2 nonlinear refractive index for quartz is S of-3.2 x 10{-16) em2/W. The nonlinear coefficient y is changed to decide the ranges 2-30 1/W.km [4].
According to |2J the Phase self-modulation is dependent on large values of XA. Pulse shape control HD allows you to control four wave mixing, cross-phase modulation and the phase of the cell-modulation.
When the output level of the sourcc becomes large, the signal modulates its own phase. This leads to a broadening of the transmitted pulse and the temporary expansion or contraction of the signal, depending on the sign of the chromatic dispersion. This leads to a shift of the edge in the direction of long waves and the cutoff momentum in the direction of short waves. In systems FOTS-MS with small channel spacing, the spectral broadening under the effect of the phase self-modulation can cause interference between channels (cross-modulation). This effect ean be controlled by compensation of dispersion.
The phase self-modulation increases with increase in the transmission power and increasing transmission speed. It is not affected by reducing the spacing between channels and increased number of channels. At low value of the chromatic dispersion and large effective area S of the phase self-modulation is reduced. However, at a small distance between channels may occur, cross - phase modulation between adjacent channels [5].
The increase in spacing between channels in WDM systems will lessen the effect, cross-phase modulation.
Really nonlinear effects can be taken into account in the dispersion-length [3]:
Ld = dmQ 111 A-xJ)n22P02/B28 (1,1 p2}Q2n21P01 >.2 A3<[)
Upon reaching the dispersion length of the value is equal to the length of the regeneration phase through predictive error correction, compensation of chromatic and polarization mode dispersions and different modulation formats are able to run at high speeds with the use of FOTS-MS without significant system failures.
At low values of chromatic dispersion, cross-phase modulation and four wave mixing distort the transmitted signal, while increasing the value of the chromatic dispersion, cross-phase modulation and self-modulation of a phase contribute little distortion, The maximum acceptable losses in chromatic dispersion over a wide bandwidth DWDM channels, the optimal value of the chromatic dispersion 3-5 PS/nm.km, which corresponds to the S non-zero dispersion shifted Central wavelength of 1550 nm in the third window of transparency. The decrease in the value of the slope of the chromatic dispersion characteristics of S com-
r i >
pensating opt ical fiber will solve the problem of compensation in a broad band DWDM channels [4-7].
In the transition from the transmission speed from 10 GB/s transfer rale 40 Gbps requirements OOS is increased by 6 (IB, PMD increases 4 times, the impact of chromatic dispersion increases 16 times, increasing the influence of nonlinear effects.
To reduce or to limit this impact can choice S, choice of modulation format, optical phase configuration, dispersion, solution, electronic equipment. It should be noted that the bit error rate increases with increase in input S power due to the nonlin-earity of the CQ.
The level of FWM is sensitive to the increase in optical power in the channel, to increase the number of channels, to reduce the spacing between channels, to reduce the absolute value of the chromatic dispersion.
Fig. 1. (e) shows a SNR of 35 dB with a single source of interference crosstalk is equal to -25 dB, And the eye chart, and the charts show a similar expansion due to the degradation of the SNR, but different noise statistics. Finally, figure 1(f) shows the SNR of 25 dB degradation of odd, I'MD, and crosstalk at the same lime. These results show that the phase portraits contain a kind of signature patterns which can be used in order to highlight and measure deterioration even in cases where they occur simultaneously (3)
Modulational instability of (Mil) leads to the transformation of a continuous signal in the modulated structure in the regime of anomalous dispersion. The frequency shift and amplification of the side bands is determined by the intensity of the original waves as well as dispersion and nonlinear coefficients CQ. MN can be considered as a special case of FWM, where 2 photons of
the input signal is converted into 2 photons with different frequencies. MN can reduce the ratio signal/noise. The use of filters or self-filtering in systems in the great length allows you to solve the issue. Management of dispersion and reduction of the power level, the use of lasers with external modulation also leads to a decrease of MN.
Nonlinear effects described above, caused by the dependence of the power from the refractive index, and are elastic in the sense that there is no exchange of energy between electromagnetic field and dielectric environment.
Nonlinearity fiber, including FSM, FCM and FWM and the stimulated scattering starts to degrade the optical signals when the optical power in the fiber is high. An important parameter that sets the length of the plot in optical systems, is the power excited in the fiber. The capacity must be large enough to provide an acceptable SNR at the output of the plot, but below the limit, which is expected to signal distortion due to nonlinearity of the fiber. The specific limit depends on several different factors such as the type of fiber used, the transmission speed, the length of the amplifier and the distribution of the applied dispersion. In a dense WDM systems compromise the relationship between the SNR degradation and the accumulated ASF, noise from optical amplifiers and nonlinear distortion of the wave shape in the fibers in the transmission determines the optimum transmission power, and together they limit the length of the regenerator-repeater [3J.
Summarizing the above, we note that in optical networks, there are many effects resulting in the degradation of the channel, they affect the performance of the system, special attention is paid to the nonlinear effects of Kerr: phase self-modulation, cross-phase modulation, which interact with chromatic and polarization mode dispersions at high speeds and at high extensions the FOL could have a negative impact on the transmission of signals and positive impact. No doubt the definition of task under different conditions and combinations of nonlinear effects to determine the border and to get only positive effect in the influence of phase self-modulation and cross-phase modulation is decisive in rahling transmission speeds
References
1. Agrawal G.P. (2013). Nonlinear Fiber Optics. Moscow. 323 p.
2. Portnov E.L. (2009). Principles of primary networks, and opticaI cable lines. Moscow: Floi line-Telecom, 544 p.
3. Kaminow I.P. (2013). Optical fiber Telecommunication VIA. Academic Press. 595 p.
4. Agrawal G.P. (2002), Fiber-optic Communication Systems. Wiley-lntersciencc. 580 p.
5. Grigoryaii A.K., Portnov E.L. (2013). Algorithmic method of determining polarization mode dispersion on fiber-optic communication lines, T-Comm, no. 8, pp. 99-101.
6. Portnov E.L. (2012). Optic cables, their installation and size. Moscow : I lot line-Telecom. 448 p,
7. Portnov E.L., Marinosyan E.H, (2014). Chromatic dispersion in single-mode optical fibers and its limitations when chirping. T-Comm, no. 9.
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T-Comm Tom 11. #11-2017
ОПРЕДЕЛЕНИЕ ВЛИЯНИЯ ФАЗОВОЙ САМОМОДУЛЯЦИИ И КРОСС-МОДУЛЯЦИИ НА ПЕРЕДАЧУ СИГНАЛОВ ПО ОПТИЧЕСКОМУ ВОЛОКНУ
Портнов Эдуард Львович, Московский технический университет связи и информатики, Москва, Россия, lc@mtuci.ru Рабенандрасана Жослен, Московского технического университета связи и информатики, Москва, Россия
Aннотация
Ограничение оптических технологий достигнуто, требования к оптическим волокнам и оптическим компонентам становится специализированным для особого использования. Терабитные и петабитные скорости требуют очень широкополосных оптических волокон и таких же компонентов. Новые ОВ должны иметь требуемые характеристики: хроматическую дисперсию, поляризационную модовую дисперсию, оптические нелинейности, оптическую ширину полосы, которая имеет особое применение, и архитектуру. Увеличивая и развивая ВОСП-СР, требуются не только широкополосные ОВ, но и развитие высокоскоростной электроники и различные методы как DWDM, так иTDM, так и сочетание DWDM-TDM для уменьшения стоимости передачи на канал. Развитие электронных компонентов для мультиплексирования, демультиплексирования, модуляции и перехода к оптической системной технике приводит к увеличению скоростей передачи до 100 Гбит/с ,400Гбит/с и выше. Современные разработки сфокусированы на широкополосном DWDM и ультрадальнем транспорте. Это требует создания новых методов модуляции, широкополосного усиления, широкополосной компенсации дисперсии и использования упреждающей коррекции ошибок. ОВ является интегральным компонентом необходимой системы.
Волоконные параметры являются основой выбора большинства таких компонентов, таких как усилители и компенсаторы. При использовании системыDWDM параметры ОВ определяют решения по дисперсии, нелинейности, распределенному усилению, спектральным потерям и поляризационной модовой дисперсии.
Для длинных дистанций ограничением являются нелинейные эффекты, такие как фазовая самомодуляция (ФСМ), фазовая кросс-модуляция (ФКМ) и четырех волновое смешивание (ЧВС), которые генерируют сигналы искажений и переходный разговор, который не может быть исключен на приемнике. Хроматическая дисперсия(ХД) и поляризационная модовая диспер-сия(ПМД) генерируют межсимвольные искажения. Параметры ХД (пс/нм.км), S (пс/нм?.км), Aэфф(мкм?) и спектральное затухание (дБ/км) могут быть оптимизированы для специальных системных архитектур.
Рассматриваются в статье возможные решения по уменьшению нелинейных эффектов, являющихся определяющими по ограничению длины протяженных ВОСП-СР.
Ключевые слова: оптическое волокно, нелинейные эффекты, фазовая самомодуляция, фазовая кросс-модуляция, хроматическая дисперсия, поляризационная модовая дисперсия.
Литература
1. Agrawal G.P. Nonlinear Fiber Optics. Moscow, 2013. 323 p.
2. Портнов Э.Л. Принципы построения первичных сетей и оптические кабельные линии связи. М.: "Горячая линия-Телеком", 2009. 544 с.
3. Kaminow I.P. Optical fiber Telecommunication VIA. Academic Press 2013. 595 p.
4. Agrawal G.P. Fiber-optic Communication Systems, Wiley-Interscience 2002. 580 p.
5. Григорьян А.К., Портнов Э.Л. Алгоритмическая методика определения поляризационной модовой дисперсии на волоконно-оптической линии связи // T-Comm: Телекоммуникации и транспорт. 2013. №8. С. 99-101.
6. Портнов Э.Л. Оптические кабели связи, их монтаж и измерение. Учебное пособие для вузов. М.: Горячая линия-Телеком, 2012, 448 с.
7. Портнов Э.Л.,Мариносян Э.Х. Хроматическая дисперсия в одномодовых оптических волокнах и её ограничения при чирпировании // T-Comm: Телекоммуникации и транспорт, №9, 2014.
Информация об авторах:
Портнов Эдуард Львович, Московский технический университет связи и информатики, заведующий кафедрой, д.т.н., профессор, Москва, Россия
Рабенандрасана Жослен, аспирант Московского технического университета связи и информатики, Москва, Россия
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