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Propagation characteristics of Super-Gaussian pulse in dispersion-decreasing fiber
Published in Gin Jose, Mário Ferreira, Advances in Optoelectronic Technology and Industry Development, 2019
All three cases are assumed that the loss of the optical fiber is negligible. The three spectra are different, and the steep front and back edges of the super-Gaussian pulse will distort the shape of the pulse greatly with the increase of the distance. Usually within a certain range, the spectrum exhibits an oscillating structure over the entire frequency range, and the spectrum is a multi-peak structure with the maximum intensity of the outermost peak, but most of the energy is still retained in the central peak. This is because the |T|<T0 is a super-Gaussian pulse with almost uniform light intensity. The reason why the spectrum is continuously broadened during transmission is because the new frequency components caused by self-phase modulation are continuously generated, and secondly. This is because modulation instability is likely to occur in the anomalous dispersion region of the fiber, and modulation instability affects the pulse distribution.
a system of four coupled, nonlinear Schrödinger equations with the effect of a coupling coefficient
Published in Kuppuswamy Porsezian, Ramanathan Ganapathy, Odyssey of Light in Nonlinear Optical Fibers, 2017
H. Tagwo, S. Abdoulkary, A. Mohamadou, C.G. Latchio Tiofack, T.C. Kofane
Self-focusing and self-guiding light beams organized in the solitonic structure have received much attention in recent years. Spatial and spatiotemporal soli-tons can find applications in all-optical switching and integrated logic, since they are self-guided in bulk media. Extensive research has been carried out in the field of pulse propagation in optical fibers [1–4]. On par with pulse propagation, continuous wave propagation in optical fibers has also demanded special attention [4]. A continuous wave with a cubic nonlinearity in an anomalous dispersion regime is known to develop instability with respect to small modulations in amplitude or in phase in the presence of noise or any other weak perturbation, called modulational instability (MI) [2, 4, 5]. Generally, the perturbation has its origin in quantum noise or a frequency shifted signal wave [4]. The MI phenomenon was discovered in fluids [6], in nonlinear optics [7] and in plasmas [8]. MI of a light wave in an optical fiber was suggested by Hasegawa [9] as a means to generate a far infrared light source, and since then it has attracted extensive attention for both its fundamental and applied interests [4, 5, 10]. In the optics community, MI is relevant to many topics, including Bragg grating s [11,12], cross-phase modulations [13,14], four-wave mixing, novel materials [15, 16], parametric oscillators [17], polarization and birefringence [18, 19], saturable nonlinearity [20], spatial instability [21], su-percontinuum generation [22], and temporal solitons in fibers [23,24].
Anharmonic Excitations in Graphene and Other 2-D Nanomaterials
Published in Kun Zhou, Carbon Nanomaterials, 2020
Elena A. Korznikova, Sergey V. Dmitriev
Another important feature of DVMs is their ability to create energy localization via modulation instability processes. Modulational instability is the effect of the deviation from periodic vibrations reinforced by nonlinearity and results in inhomogeneous distribution of energy in the system [38]. This phenomenon was observed in various physical systems including nonlinear optics [39] and fluid dynamics [40] as a possible reason for the well-known rogue waves phenomenon [41]. In nonlinear lattices, modulational instability in the presence of small perturbations is considered to be the first step toward energy localization in the form of DBs [42].
Impact of fractional effects on modulational instability and bright soliton in fractional optical metamaterials
Published in Waves in Random and Complex Media, 2023
Azakine Sindanne Sylvere, Mibaile Justin, Vroumsia David, Mora Joseph, Gambo Betchewe
Modulational instability (MI) is one of the most fundamental processes in nonlinear wave systems in nature. It occurs as a result of interplay between the nonlinearity and dispersion in the time domain or diffraction in the spatial domain [9,10]. It appears when the weak perturbations imposed on a continuous wave (cw) state grow exponentially [9,11]. The MI phenomenon has been studied in ordinary materials and in MMs by many authors using the Nonlinear Schrödinger Equations (NLSE) in classical derivative. F. Ndzana et al. showed the influence of quintic term on MI by using the standard linear stability and the variational approach [12]. Recently the effect of the cross-phase modulation was shown in higher-order nonlinear dispersion in an elliptical birefrigent positive-negative index coupler with self-steepening and intrapulse Raman scattering [13]. MI was also investigated in the coupled nonlinear field equations for pulse propagation in a NIM embedded into a Kerr medium [9], the few cycle pulses in optical fibers [14], in the role of anomalous self-steepening effect in NIM [15], in nonlinear MMs induced by cubic-quintic nonlinearities and higher-order dispersion effects [16] and in nonlinear NIM [17]. The influence of memory effect was also studied in MI phenomena.
Oscillating two-dimensional Ca2+ waves in cell networks with bidirectional paracrine signaling
Published in Waves in Random and Complex Media, 2021
C. B. Tabi, A. S. Etémé, A. Mohamadou, T. C. Kofané
It is now recognized that modulational instability (MI) is one of the direct mechanisms that lead to the formation of modulated soliton-like structures in physical systems where competitive effects between nonlinearity and dispersion are effective. The technique of MI has been successfully applied to different physical settings, both in one and two-dimensional configurations [33–40]. We intend to use it in this work in order to discuss the regions of parameter values where modulated waves of are likely to be observed. We equally want to find exact solutions for the proposed model and show that they may have some spiraling features, as already observed numerically in many works related to oscillations in cell networks [41–43]. The rest of the paper is therefore outlined as follows: In Section 2, we make use of the semi-discrete approximation to show that the dynamics of the cellular network can fully be described by the 2D complex Ginzburg–Landau (2DCGL) equation for each of the frequency modes. In Section 3, the MI of plane wave solutions is addressed, where regions of instability, for both the HF and LF regimes, are detected and compared. We thereafter derive exact solutions for the model using the -expansion method. The obtained solutions are found to display some spiral-like behaviors. Concluding remarks end the paper.
Computer Model for EDFA Dynamics Over 1525–1560 nm Band Using a Novel Multi-Wavelength MATLAB Simulink Test Bed for 8-Channels
Published in IETE Journal of Research, 2018
Reena Sharma, Sanjeev Kumar Raghuwanshi
Practically, it is not easy to obtain high gain with relatively low noise and high pumping efficiency at the same time. The foremost constraint is introduced by the ASE. The foremost constraint is introduced by the ASE when it travels backward in the direction of the pump and reduces the pump power. However, relatively less noise of EDFAs picture them as a preferred choice for WDM lightwave systems. Despite relatively low noise, the quality of network structure employed for long distances using multiple EDFAs get affected by the amplifier noise. Over the dispersion region of the fibre, the degradation in signal quality increases because of modulation instability. Cascaded EDFAs structure is used for transmission over seas. In this case, small ASE addition in amplifier gain for individual channels grows at a high rate along a chain of inline amplifiers that makes the problem more severe.