Fiber Optic Media Research Articles

Modulation instability analysis and optical solitary waves solutions of high-order dispersive parabolic Schrödinger–Hirota equation

The balance of nonlinearity and dispersion in optical fiber medium gives rise to a constantly propagating pulse. Such distortion less waves have attracted potential interest. The dynamics of optical solitons are governed by the nonlinear Schrödinger’s equation (NLSE). A modified form of NLSE which incorporates group velocity dispersion (GVD) and the Kerr law nonlinearity is recently adopted for the study of such waves. Here, we investigate the nonlinear Schrödinger–Hirota’s equation (NLSHE) using the Sardar subequation approach. Some novel solutions to the NLSHE corresponding to the bright, dark, kink, and cusp solitons have been reported. Additionally, the spatial and temporal dynamics of these solitons provide deep insight into the behavior of these solutions. The stability study is carried out via modulation instability (MI) concept. Our work might have benefits in the propagation of these pulses in the optical fiber for communication.

Comment on “Modulational instability and soliton trains in optical fiber media with real and imaginary Raman gains”

In their recent article, Nfor et al. [Optik - International Journal for Light and Electron Optics 285 (2023) 170951, https://doi.org/10.1016/j.ijleo.2023.170951] have studied, through a dissipative nonlinear Schrödinger equation, the modulational instability and soliton trains in optical fiber media with real and imaginary Raman gains. After finding a steady-state solution of this equation, they have applied the linear stability analysis to investigate its modulational instability. It appears that (i) their proposed steady-state solution is not really a continuous wave solution of their model equation, and (ii) their ansatz used for the modulation perturbation function violate all mathematical/physical rules, leading thus to an inappropriate results. Moreover, during their development on exact analytical solutions, authors have not established conditions under which those analytical solutions may exist, as one can easily verify in subsection 3.1. It is the aim of the present comment to correct all shortcomings about the modulational instability study carried out in their study. We start by presenting the correct steady-state solution of the considered dissipative nonlinear Schrödinger equation, and then investigate with details its modulational instability. We end this comment by establishing conditions under which equation (15) admits analytical solutions of form (16) when a6=0, and the present some other interesting solutions of this equation (16).

Modulational instability and soliton trains in optical fiber media with real and imaginary Raman gains

We consider a higher-order nonlinear Schrödinger amplitude equation with real and imaginary Raman gain terms. This equation is shown to govern the propagation of femtosecond pulses in optical fiber media. We investigate on the modulational instability of continuous wave solution of this amplitude equation and show that the gain exist in both the anomalous and normal dispersion regimes, provided the complex intrapulse Raman terms are considered. However, when the dissipation induced by Raman process in the optical fiber is neglected; periodic bright solitary waves can only be identified in the anomalous dispersion regime. Nonlinear periodic trains of optical pulses are analytically obtained using the ansatz technique which incorporates the direct integral method. The observation of an optical shock front moving at the group velocity, is attributed to the Raman dissipation process in the optical fiber. Finally, results of numerical simulations equally underscores the influence of Raman gain terms on the evolution of optical soliton trains.

(Invited) Golden jubilee of solitons in optical fibers: For young scientists who love creative works

A memoir related to the discovery of optical soliton is presented with an intention of stimulating motivation of young scientists for creative works. Soliton is clearly a more desirable pulse for stable transmission of information in optical fiber medium. However, I would like to emphasize additional capability of a soliton pulse as information carrier without increasing thermodynamical entropy and invite the reader’s attention to possible relation to information processing in biological systems.

Exploration of new solitons in optical medium with higher-order dispersive and nonlinear effects via improved modified extended tanh function method

Throughout this article, the improved modified extended tanh function method is presented for deriving fresh travelling wave alternative solutions in different forms of nonlinear Schrödinger equation (NLSE) with higher-order dispersive and nonlinear effects that describes the propagation of ultra-short optical solitons in an optical fiber medium. For this model, we have a variety of new solutions, including solitons (bright, dark and singular), exponential, singular periodic and Jacobi elliptic solutions. Graphical representations of selected solutions are provided to demonstrate the physical properties of the raised solutions.

Periodic and localized waves in parabolic-law media with third- and fourth-order dispersions.

Considering the higher-order nonlinearity is essential in a broad range of real physical media as it significantly influences the wave dynamics in these systems. We study the propagation of femtosecond light pulses inside an optical fiber medium exhibiting higher-order dispersion and cubic-quintic nonlinearities. Pulse evolution in such a system is governed by a higher-order nonlinear Schrödinger equationincorporating second-, third-, and fourth-order dispersions as well as cubic and quintic nonlinearities. The periodic and solitary wave solutions are identified using the equationmethod. Results presented indicated the potentially rich set of periodic waves in the system under the combined influence of higher-order dispersive effects and cubic-quintic nonlinearity. The velocity of these structures is uniquely dependent on all orders of dispersion. Conditions on the optical fiber parameters for the existence of these exact stable solutions are found by analytical stability analysis.

Chirped localized pulses in a highly nonlinear optical fiber with quintic non-Kerr nonlinearities

We study the existence and propagation properties of chirped localized pulses in a highly nonlinear fiber medium exhibiting self-steepening, self-frequency shift, and quintic non-Kerr nonlinearities. Pulse evolution in such fiber system is governed by a higher-order nonlinear Schrödinger equation incorporating the derivative Kerr and non-Kerr nonlinear terms. We show that bright, dark and kink type solitary waves exist in the presence of all physical processes. A special ansatz is introduced to analyze the existence of solitary waves on a continuous-wave background in the optical fiber medium. It is shown that the obtained localized pulses exhibit a nonlinear chirp which has a quadratic dependence on light intensity. We also find that the magnitude of the associated frequency chirp can be controlled effectively by varying the parameters of self-steepening, self-frequency shift, and derivative non-Kerr nonlinearity effects. The restrictions on the optical fiber parameters are also extracted for the existence of these nonlinearly chirped solitary waves. Results in this study may be useful for experimental realization of shape-preserved pulses in optical fibers and further understanding of their optical transmission properties.

Dark solitary pulses and moving fronts in an optical medium with the higher-order dispersive and nonlinear effects

We study the propagation dynamics of extremely short light pulses in an optical fiber medium exhibiting a plethora of higher-order dispersive and nonlinear effects of different nature. The wave propagation in such nonlinear media is described by an extended nonlinear Schrö dinger equation incorporating both even and odd higher-order terms. We introduce an appropriate nonlinear equation which enables us to achieve analytical shape-preserved and periodic wave solutions for the model. A new dark solitary wave is identified for the first time in the presence of all physical processes. In addition, we show that moving fronts or optical shock-type soliton solutions exist for the considered model. The periodic wave solutions are also found together with the parametric conditions for their existence. Results in this study may be useful for experimental realization of shape-preserved pulses in optical fibers and further understanding of their optical transmission properties.

Optical Bullets and Their Modulational Instability Analysis

The current work is devoted to investigating the multidimensional solitons known as optical bullets in optical fiber media. The governing model is a (3+1)-dimensional nonlinear Schrödinger system (3D-NLSS). The study is based on deriving the traveling wave reduction from the 3D-NLSS that constructs an elliptic-like equation. The exact solutions of the latter equation are extracted with the aid of two analytic approaches, the projective Riccati equations and the Bernoulli differential equation. Upon applying both methods, a plethora of assorted solutions for the 3D-NLSS are created, which describe mixed optical solitons having the profiles of bright, dark, and singular solitons. Additionally, the employed techniques provide several kinds of periodic wave solutions. The physical structures of some of the derived solutions are depicted to interpret the nature of the medium characterized by the 3D-NLSS. In addition, the modulation instability of the discussed model is examined by making use of the linear stability analysis.

Geometric phase in distributed fiber optic sensing.

The geometric phase in the beat signal from coherent interference of two frequency-offset light beams is measured using a novel distributed optical fiber sensing setup. In a fiber optic medium, with changing beam intensities, to the best of our knowledge, ours is the first measurement of the mentioned geometric phase. Experimental results of applying a 100-Hz sinusoidal stimulus to a polarization scrambler and a piezoelectric transducer inline to an optical fiber are presented. The results may enable novel distributed fiber sensing techniques.

Implementation of Two-Way Voice and Text Communication System Using Fiber Optic Media

In this technology age, people's need for communication systems is growing. In various places and conditions, communication must be maintained to meet various needs. One of the solutions required in these circumstances is an optical fiber communication system. Fiber optic cable is a light-based data transmission technique. The advantages of optical transmission include the fact that the light spectrum does not spread like radio frequencies, making it impossible to intercept, the fact that it propagates at a very high speed, allowing it to go very large distances, and the ease with which it may be installed. To tackle this problem, we proposed to innovate by realizing and developing a two-way voice and text communication system using fiber optic cable media. The voice and text communication system created and deployed in this study is based on an Android application. This communication system does not require a server and internet network. Only Android smartphones, access points, fiber media converters, and fiber optic cables are required. The greatest throughput value measured by the system is 2708 bytes/second, while the lowest is 1020 bytes/second. The longest delay is 2.314 seconds, while the shortest is 1.99 seconds. In terms of packet loss, the value is 0%.

Wave Propagations in Nonlinear Low-Pass Electrical Transmission Lines through Optical Fiber Medium

The present article discovers the new soliton wave solutions and their propagation in nonlinear low-pass electrical transmission lines (NLETLs). Based on an innovative Exp-function method, multitype soliton solutions of nonlinear fractional evolution equations of NLETLs are established. The equation is reformulated to a fractional-order derivative by using the Jumarie operator. Some new results are also presented graphically to understand the real physical importance of the studied model equation. The physical interpretation of waves is represented in the form of three-dimensional and contour graphs to visualize the underlying dynamic behavior of these solutions for particular values of the parameters. Moreover, the attained outcomes are generally new for the considered model equation, and the results show that the used method is efficient, direct, and concise which can be used in more complex phenomena.

Quantum key distribution integrating with ultra-high-power classical optical communications based on ultra-low-loss fiber.

The demand for the integration of quantum key distribution (QKD) and classical optical communication in the same optical fiber medium greatly increases as fiber resources and the flexibility of practical applications are taken into consideration. To satisfy the needs of the mass deployment of ultra-high power required for classical optical networks integrating QKD, we implement the discrete variable quantum key distribution (DV-QKD) under up to 25 dBm launch power from classical channels over 75 km on an ultra-low-loss (ULL) fiber by combining a finite-key security analysis method with the noise model of classical signals. To the best of our knowledge, this is the highest power launched by classical signals on the coexistence of DV-QKD and classical communication. The results exhibit the feasibility and tolerance of our QKD system for use in ultra-high-power classical communications.

Localized pulses in optical fibers governed by perturbed Fokas–Lenells equation

We study the existence and properties of propagating solitary waves in an optical fiber medium described by the perturbed Fokas-Lenells equation. Additional effects to the usual Fokas-Lenells equation include third- and fourth-order dispersions, inter-modal dispersion, nonlinear dispersion and self-steepening effect. The model applies to the description of light pulse propagation applicable to a femtosecond or subpicosecond regime. We introduce an efficient ansatz for the field amplitude that enables us to obtain solitary waves with the governing model. More pertinently, we find that solitary wave solutions of bright and dipole shape do exist in the presence of all orders of dispersion and various nonlinear effects. We also find that the energy associated to the obtained structures depends on all material parameters. The requirements concerning the optical fiber parameters for the existence and uniqueness of such solitary waves are presented.

Propagation of chirped periodic and localized waves with higher-order effects through optical fibers

We study the propagation properties of nonlinear periodic waves in an optical fiber medium exhibiting Kerr dispersion and quintic nonlinearity. The quintic derivative nonlinear Schrödinger equation is applied to model the evolution of femtosecond light waves in such system. Unlike periodic structures in Kerr media, the novel waves possess a nonlinear chirp which varies with their intensity. In addition to the linear part, the pulse chirp also includes two intensity dependent chirping terms. The conditions on fiber parameters for the existence of the newly found periodic waves are presented. A wide variety of solitary pulse shapes including the bright, dark, kink, anti-kink, and gray solitary waves are obtained in the long-wave limit. Our results show that Kerr dispersion plays a crucial role in introducing a nonlinear chirp for the periodic and solitary waves. Finally, the stability of these nonlinearly chirped solutions is numerically studied under the finite perturbations.

Design of Polarimetric-Based Optical Current Sensor for Electric Power System Application

Many problems arise in the electric power protection system due to applying a ferrous core current transformer (CT). One of the most crucial problems is a magnetic saturation issue, which tends to cause a measurement error on the secondary side of the CT and could reduce the performance of the protection system. An alternative solution to this issue is the needs to develop an electric current sensor utilizing optical materials. A polarimetric-based optical current sensor (OCS) is a technique considered to be compatible with the future smart grid environment. The OCS principles are based on the magneto-optic Faraday effect that could produce optical rotation in the optical media when a polarized light propagates in those materials. Due to the linear and circular birefringences effect in optical fiber medium are exist, therefore, in this paper the OCS and its associated elements are modelled by considering the birefringence effect in the optical sensor system including optical fiber links. Then, the OCS model is translated to a computer simulation program using a computer application software. Orientation of the second polarizer (analyzer) to the first polarizer in the simulation were conducted using two different angles which are angle α of 45° and 90°. Performance assessment of the OCS model is presented using two various electric current of the power system test to investigate the presence or absence of the saturation effect that may arise in the polarimetric-based optical current sensor model. The simulation results have provided that the saturation effect disappear in the simulation and the analyzer orientation angle α of 45° gives better performances of optical power modulation than the other angle.

The Necessity of Testing the Optical Fiber Link in the Distributed Control System

With the rise of industry 4.0 and the Internet, a large number of network optical fiber links are applied in the control system of thermal power plants. However, there are no test methods and requirements for optical fiber links in the acceptance test procedures for decentralized control system of thermal power plants. In this paper, the optical fiber medium, field bus type and so on are introduced, and the necessity and method of optical fiber link testing are discussed.

Bilinear Forms and Dark-Dark Solitons for the Coupled Cubic-Quintic Nonlinear Schrödinger Equations with Variable Coefficients in a Twin-Core Optical Fiber or Non-Kerr Medium**Supported by the National Natural Science Foundation of China under Grant Nos. 11772017, 11805020, 11272023 and 11471050, the Fund of State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), China (IPOC: 2017ZZ05),

Twin-core optical fibers are applied in such fields as the optical sensing and optical communication, and propagation of the pulses, Gauss beams and laser beams in the non-Kerr media is reported. Studied in this paper are the coupled cubic-quintic nonlinear Schrödinger equations with variable coefficients, which describe the effects of quintic nonlinearity for the ultrashort optical pulse propagation in a twin-core optical fiber or non-Kerr medium. Based on the integrable conditions, bilinear forms are derived, and dark-dark soliton solutions can be constructed in terms of the Gramian via the Kadomtsev-Petviashvili hierarchy reduction. Propagation and interaction of the dark-dark solitons are presented and discussed through the graphic analysis. With different values of the delayed nonlinear response effect b(z), where z represents direction of the propagation, the linear- and parabolic-shaped one dark-dark soltions can be derived. Interactions between the parabolic- and periodic-shaped two dark-dark solitons are presented with b(z) as the linear and periodic functions, respectively. Directions of velocities of the two dark-dark solitons vary with z and the amplitudes of the solitons remain unchanged can be observed. Interactions between the two dark-dark solitons of different types are displayed, and we observe that the velocity of one soliton is zero and direction of the velocity of the other soliton vary with z. We find that those interactions are elastic.

Secure EEG Signal Transmission for Remote Health Monitoring Using Optical Chaos

For the very first time, we present the use of optical chaos for the secure transmission of electroencephalogram (EEG) signals through optical fiber medium in remote health monitoring systems. In our proposed scheme, a semiconductor laser source is used to generate optical chaos, which hides EEG signal before its transmission over the optical fiber medium. The EEG signals are acquired by using a 14-channel Emotiv headset device, which are then processed and rescaled to be compatible with the experimental environment (Optisystem). The mixing of EEG signals and chaos is performed using additive chaos masking scheme, which exhibits certain useful properties such as simplicity and easy recovery of the message. Chaotic data (a combination of EEG signals and chaos) is sent over the optical fiber medium to investigate propagation issues associated with secure EEG signal transmission. The scheme is implemented for long haul communication in which the linear impairments of optical fiber are controlled for successful transmission of the secure signal. The parameters at transmitting and receiving sides are selected to achieve synchronization, such that the transmitted signal could be subtracted from identical chaos to restore the original EEG signal at the receiving side. The scheme is tested for different lengths of the optical fiber cable in which the quality of the received signal is determined by obtaining Q-factors. This scheme could also be used with medical signals such as electrocardiography and electromyography.

Impact of Combine Dithering and Modulators to Mitigate Noise in Radio Over Fiber System

<p>A well-prepared Radio over Fiber (RoF) is a technology that combines two transmission technologies, radio and optical fiber transmissions. The study focused on the characteristics and problems of the optical fiber medium. One of the problems in the optical fiber is the effect of nonlinear characteristic, which caused by the high light intensity in the optical fiber core with extended interaction area in a single mode fiber (SMF). This characteristic reduces the output width and creates a pulse broadening. The nonlinear characteristics discussed in this study focused on SPM (self-phase modulation) and GVD (Group Velocity Dispersion). To overcome the nonlinear problems, this study presented a method to make the noise-resistant transmitted signal and improve the optical fiber power range. The fundamental of this study was developing similarities of previous studies regarding nonlinearity in the optical fiber. The results show that the use of two modulators combined with the amplification generated the signal with smoother spectrum, which means that the spectrum distribution was more uniform. There was 61.5 % increase of the peak power of the output signal after amplification using an optical amplifier.</p>