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This work simulates the (1+1)-dimensional nonlinear perturbed Schrödinger model (NLPSM ). Hydrodynamics, elastic media, nonlinear optical fiber communication, and plasma physics are just a few of this model's mathematical physics and engineering applications. The study aims to accomplish two main objectives. First, it seeks to find unique soliton solutions such as solitary, dark, periodic, and plane wave solutions that haven't been found in the literature before using the modified Sardar sub-equation approach (MSSEA ). Second, a novel approach to analysis called bifurcation analysis is used to investigate the dynamic behavior of the model. Physical compatibility findings are supported by density, 3-D, and 2-D illustrations made with parametric variables. The analysis shows that the approach used to quickly acquire complete and typical answers was successful. This approach works well for solving challenging problems in physics, engineering, mathematics and fiber optic phenomena. [ABSTRACT FROM AUTHOR]

This work focuses on the study of the paraxial wave model with a space–time fractional form. This model has more importance for describing light propagation in nonlinear optical fibers and telecommunication lines. The main aim of this work is to observe the effect of the fractional parameters and compare the truncated M -fraction with the beta-fraction, conformable fraction form, and classical form of the PW model. For this observation, we applied the Simplest equation technique to acquire analytical solutions to the space–time (spatiotemporal) M -fractional paraxial wave model. We are able to acquire several new optical soliton solutions, including periodic waves, kink-type waves, rogue-type waves, and several novel periodic waves, by providing the appropriate fractional parametric values. These solutions have significance for shedding light on a number of physical phenomena in the realms of optical fiber and communication sciences. The diverse values of fractional parameters and the three-dimensional and contour plot graphs of certain chosen solutions are depicted, which are the most accurate physical characterizations of the outcomes. We also sketch the comparative graph of diverse fractional forms and the classical form of the paraxial wave equation in two-dimensional plots. Consequently, our findings represent an important breakthrough in this complex area and help further develop our comprehension of the behavior of solitons. [ABSTRACT FROM AUTHOR]

The Quantum Noise Stream Cipher (QNSC) is offering very high security in physical layer of optical fiber communication network to meet the today's main requirement of secure networks. However, the problem of timing and carrier frequency offset synchronization was higher for Coherent optical orthogonal Frequency Division Multiplexing (CO-OFDM) systems using QNSC for network security. For higher-order modulation systems, the algorithms used to overcome this problem are offering very low accuracy. In addition to this, the chances of attack by an illegal receiver are more due to no encryption used for the preamble creation. Existing algorithms used to create a new preamble is: CNI ((conjugate, negative, and image) with Pseudo-Noise sequence) and CNC ((conjugate and negative) with Chu sequence). In this paper, ConvNN (Convolutional Neural Network) and CapNN (Capsule Neural Network) based joint synchronization of timing and frequency for CO-OFDM system is proposed. From the experiments, performed at 10Gbps, it has been illustrated that the proposed networks are giving more robust results. In addition to these proposed networks are offering better and secure performance for both timing and frequency offset synchronization by using less training data. [ABSTRACT FROM AUTHOR]

This study explores optical soliton solutions within the framework of the Caudrey–Dodd–Gibbon equation (CDGE) and the ( 1 + 1 )-dimensional Boussinesq equation, utilizing the modified Sardar sub-equation method (MSSEM). The derived solutions are meticulously verified using symbolic software Mathematica and encompass a rich array of mathematical functions, including trigonometric, hyperbolic, and exponential functions. Visualization techniques, such as 3D plots, 2D plots, density graphs, and contour graphs, effectively illustrate the diverse behaviors exhibited by these soliton solutions. These equations have been studied previously, their comprehensive traveling wave solutions are relatively unexplored. By employing the modified Sardar sub-equation method, which has demonstrated effectiveness in solving nonlinear evolution equations, this study aims to bridge this gap. The soliton solutions obtained encompass a wide spectrum of behaviors, including bright, dark, periodic, singular, dark-periodic, bright-periodic, dark-singular, compactons, and bright-singular soliton solutions, as well as other complex phenomena. The comprehensive exploration of soliton solutions not only enhances our understanding of fundamental wave phenomena but also provides valuable insights for addressing nonlinear equations across various scientific disciplines, including optical fiber communications, plasma physics, and nonlinear dynamics. [ABSTRACT FROM AUTHOR]

The use of optical fiber for communication has grown at a rapid pace due to the demands of the modern information era. In this paper, the modified extended direct algebraic method is implemented to explore optical solitons and other exact wave solutions for the coupled system of perturbed highly dispersive complex Ginzburg–Landau equation with polynomial nonlinearity law which describe the transmission of solitons in birefringent fibers. The obtained solutions include bright solitons, dark solitons, singular solitons and combo dark-singular solitons. Additionally, Jacobi elliptic function solutions, exponential solutions, and singular periodic solutions are also offered. To ensure the existence of the obtained soliton solutions, we set some constraints on the parameters. In addition, some selected solutions are visually shown to demonstrate the physical properties of the exact solutions. [ABSTRACT FROM AUTHOR]

In this paper, using the Hirota bilinear method, we investigate the perturbed Gerdjikov–Ivanov equation (PGIE) for lump soliton, rogue wave, periodic and kink cross rational solutions, homoclinic breathers, M-shaped and many other interactions. All these solutions have so many real life applications for example lump wave help to study the behavior of vortices and eddies in the ocean, which are used for climate modeling and fisheries management. Rogue waves are used in maritime safety, M-shaped solitons are used in optical fiber communications to transmit data over long distances without distortion, improving the efficiency and reliability of high-speed data transmission. Breathers can be used in fiber optic systems to generate ultrafast optical pulses, which have applications in telecommunications and laser technology. We also discuss the dynamical behaviour of our solutions in various dimensions. [ABSTRACT FROM AUTHOR]

The Schrödinger–Hirota equation are studied in light transmission, optical fiber communication, and nonlinear effects in optics. The auxiliary equation method is not only suitable for solving specific types of nonlinear partial differential equations, but also has strong applicability to all kinds of different types of equations. It helps us to deduce the exact solution of the equation faster and analyzes the dynamic behavior of the system further. The extended fourth Jacobi elliptic equation is used in this paper to seek different types of exact solutions, which include bright soliton solutions, kink solutions, periodic wave solutions, and singular traveling wave solutions via selecting appropriate parameters.The characteristics of some solutions are graphically presented using two- and three-dimensional graphs such as the real part, the imaginary part, and their modulus via providing suitable values to arbitrary parameters. Compared to other methods, the method is more direct and easier for calculations. Kindly check and confirm the edit made in the title. The edit made in the title is correct. The word "extended" in the title can be deleted if necessary. [ABSTRACT FROM AUTHOR]

Fiber pump lasers are widely used in a variety of fields, such as optical fiber communication, national defense, and medical beauty due to their high beam quality and intense laser energy. However, the alignment errors of optical parameters can influence the beam quality in the packaging of the fiber pump lasers. It is necessary to analyze the reflector, focusing lens, fiber, and the laser diode on the coupling influence between for guiding the fiber pump laser packaging. Firstly, we establish the optical path between the laser diode, focusing lens and reflector based on the physical ray-tracing method. On the other hand, the high coupling efficiency of whole system is achieved by optimize the parameters of each optical element. The simulation result shows that the highest coupling efficiency is 98.6% based on optimizing the parameters of the optical path while the experimental result of coupling efficiency is 90.36%. Also, the effects of refractive index, wavelength and fiber diameter on coupling efficiency are further investigated. The experimental results show that the radial displacement has the greatest influence on the coupling efficiency. The simulation results show that increasing the fiber core diameter can effectively improve the coupling efficiency. The results of rigorous analysis will provide an effective reference for manufacturing compact, high coupling efficiency fiber pumped laser. [ABSTRACT FROM AUTHOR]

Data privacy is becoming more important as the internet of things (IoT) rapidly expands. There are significant consequences for the broad adoption of the internet of things. Homomorphic encryption is one possible solution for protecting sensitive data in the IoT. However, there is a great deal of potential for efficiency gains. In order to get enough privacy and security, it is also crucial. Our homomorphic encryption technique for secure and private optical fibre communication is detailed in this publication. The data owner, fog server, and data consumers' privacy is the primary focus of the proposed architectural design. The performance of this research shows that our FCHE solution improves data security throughout the data storage operation and reduces encryption length. This research also aims to analyse the factors of optical fiber communication cost, storage cost, and computing cost in the context of FCHE. [ABSTRACT FROM AUTHOR]

This study addresses dual-mode equations, focusing on the nonlinear wave behavior characterized by simultaneous bidirectional movement influenced by a specific phase velocity. Building upon Korsunsky's enhanced Korteweg-De Vries equation, we introduce an innovative dual-mode simplified modified Camassa-Holm model and systematically analyze its solutions. Employing explicit tanh / coth , Exp-function expansion, extended Kudryashov-expansion, and rational sin / cos techniques, we establish soliton solution constraints. The validation process includes generating supportive 3D and 2D plots. Furthermore, the study is exploring the interaction between dual waves and how the speed of waves changes. The outcomes of this research are expected to unravel soliton behavior. particularly extend into diverse domains, such as shallow water waves and optical fiber communication. The novel techniques employed in this study contribute to the stability of the exact solutions obtained, offering new perspectives beyond previous endeavors in the field. [ABSTRACT FROM AUTHOR]

This manuscript presents some new exact solutions for the dispersive Schrödinger Hirota's (SH) equation considering the effects of spatio-temporal dispersion with parabolic law nonlinearity. A wave transformation technique is implemented to transform the SH equation into a nonlinear ordinary differential equation. The solutions for the dispersive SH equation are derived using the modified extended tanh approach. These solutions exhibits various sorts of solitons, including bright, dark, periodic, and singular solitons. The findings of this research hold potential significance in the domain of fiber-optic communication, as they contribute to a deeper understanding of soliton dynamics. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the impact of the integrability criterion on mixed-derivative nonlinear Schrödinger equations, specifically focusing on the Rangwala-Rao (R R) equation introduced by A. Rangwala in 1990. Our objective is to enhance our understanding of the dispersion effect by examining innovative soliton wave solutions and their interactions. The tanh method is utilized to generate unique solitary wave solutions for the Rangwala-Rao (R R) equation. The study of the Rangwala-Rao (R R) holds significance as it has the potential to contribute to the development of more efficient optical fiber communication systems. The numerical solutions presented in this research illustrate the dynamic nature of optical fiber pulse propagation, underscoring the distinctiveness of this work compared to previous scholarly endeavors. The study obtained various soliton solutions, including rational, trigonometric, and hyperbolic functions. The results are presented in graphical form with appropriate parameter values to aid visualization. The originality of our computed outcomes, which represent novel achievements that surpass previously derived solutions, becomes evident when we compare our accomplishments with theirs. These newly examined results are innovative and novel, with the potential to significantly propel the realms of nonlinear optics and mathematical physics forward. This study proves that the computational method used is efficient, brief, and widely applicable, making it valuable to engineers who work with engineering models and dynamical models. [ABSTRACT FROM AUTHOR]

In this work, we realised the soliton solutions of nonlinear Schrödinger equation (NLSE) that arise from optical fibers, we considered the modified Sardar sub-equation method (MSSEM) to find solitary solutions analytically. The stability of the retrieved soliton solutions realised from the NLSE are investigated. We demonstrate the soliton solutions that are stable and can last for a very long time without losing its form or energy under specific circumstances and those soliton solutions that are unstable. The MSSEM is a frequently employed technique in research for addressing specific mathematical modeling or physical phenomena problems. Its selection in this specific study might stem from its proven efficacy in handling the particular problem under investigation. The decision to utilize MSSEM could be driven by several considerations, including its precision, computationally efficient, effectiveness, greater accuracy and capability to manage intricate systems. Finally, our method offers greater flexibility in modeling various physical phenomena, which makes it particularly useful in applications in diverse fields such as quantum mechanics and nonlinear optics. The findings have ramifications for the architecture of optical fiber communications and offer significant new insights into the behavior of solitons in optical systems. The NLSE has proven to be an effective tool for understanding wave behavior in fiber optics. Its applications have helped engineers and scientists optimize the design of optical fibers and predict the behavior of various conditions. Moreover, our study provides insights into the fundamental properties of solitary solutions in the NLSEs and their practical implications in physical systems. [ABSTRACT FROM AUTHOR]

Optical layer attacks on optical fiber communication networks are one of the weakest reinforced areas of the network, allowing attackers to overcome security software or firewalls when proper safeguards are not put into place. Encrypting data using a random phase mask is a simple yet effective way to bolster the data security at the physical layer. Since the interactions of the random phases used for such encryption heavily depend on system properties like data rate, modulation format, distance, degree of phase randomness, laser properties, etc., it is important to determine the optimum operating conditions for different scenarios. In this work, assuming that the transmitter and the receiver have a secret pre-shared key, we present a theoretical study of security in such a system through mutual information analysis. Next, we determine operating conditions which ensure security for 4-PSK, 16-PSK, and 128-QAM formats through numerical simulation. Moreover, we provide an experimental demonstration of the system using 16-QAM modulation. We then use numerical simulation to verify the efficacy of the encryption and study two preventative measures for different modulation formats which will prevent an eavesdropper from obtaining any data. The results demonstrate that the system is secure against a tapping attack if an attacker has no information of the phase modulator and pre-shared key. [ABSTRACT FROM AUTHOR]

Phase encoding in quantum key distribution (QKD) enables long-distance information-theoretic secure communication in optical fibers. We present a novel theoretical model characterizing errors from various sources in practical phase encoding-based QKD systems, namely the laser linewidth, detector dark counts, and channel dispersion. This model provides optimized optical pulse parameters and less distortion in pulses, which eliminates system imperfections and leads to a reduced quantum bit error rate (QBER) for practical QKD scenario. This analysis is applicable to various fiber-based phase and time encoding protocols. In particular, we implement this to a differential phase shift (DPS) QKD scheme operating at a 2.5 GHz clock, which produces a secure key rate of 193 bits/s at a fiber length of 265 km and an unprecedented QBER < 1 % up to 225 km length with standard telecom components. We show that by adjusting the quantum efficiency and dark count rates of detectors, proposed system can establish secure keys up to 380 km distance using standard telecom grade fiber with a QBER of 1.48%. Moreover, the system is compatible with existing optical fiber networks and capable of establishing a secure key exchange between two cities 432 km apart using ultra-low-loss (ULL) specialty fiber. [ABSTRACT FROM AUTHOR]

Ranging from optical fiber communication to optical wireless communication regimes, twisted light has drawn the prodigious contemplation of researchers. Thus far, the tricolor visible light laser diodes (TVL-LDs) have not been scrutinized for optical angular momentum (OAM), which, however, could pioneer fortuitousness towards a new paradigm of indoor wireless communication. Here, we proposed an OAM superposition of three different Laguerre Gaussian modes such as l = 0, m = 0; l = 14, m = 0; and l = 40, m = 0, and realised by utilising red, green and blue (R/G/B) LDs as independent channels and binary data streams are encoded incorporating non return to zero linecoding, exhibiting a total capacity of 45 Gbps (3 wavelengths (λ) × 3 OAM beams × 5 Gbps). The performance of R/G/B LDs is compared in a visible light communication (VLC) model at different input parameters such as link length between the irradiating source (Lambertian) and receiver detection region, transmitter half angle, incidence half angle, and optical concentrator area. We successfully performed the transmission of 45 Gbps data over a 1.4 m line of sight VLC link and 2.3 m in a non-LoS link employing TVL-LDs, while the red LDs offered excellent performance. [ABSTRACT FROM AUTHOR]

Early detection of potentially unreliable areas in optical fibers makes it possible to detect degradation of optical fibers of fiber-optic communication lines at an early stage. Early diagnostics of the physical state of optical fibers located in the laid optical cables of telecommunication systems is an important topical task. The paper presents adaptive algorithms that allow one to determine the maximum of the Mandelstam–Brillouin scattering spectrum (Brillouin frequency shift), and then the degree of tension of optical fibers. The process of determining the Brillouin frequency shift, whose values at wavelengths of laser radiation used in telecommunication systems belong to the microwave range, can be significantly accelerated if adaptive algorithms for obtaining and processing data are implemented due to a special choice of the step for the scanning frequency and the time of accumulation of measurement results. The adaptive algorithms considered in this paper make it possible to speed up the process of obtaining output results in Brillouin reflectometers by ignoring readings that do not significantly affect the final characteristics. The construction of approximate graphs of the distribution of the spectrum and tension along the length of the fiber allows the trained user of the Brillouin reflectometer to stop the analysis process in order to make corrections to the measuring process (selection of the scanning range in frequency, change in the scanning step in frequency, choice of the accuracy of the presentation of output results, change in spatial resolution, etc.), which also speeds up the testing of the selected fiber. The measurement process can also be accelerated by adaptively changing the number of averages. With a database of measured Mandelstam–Brillouin scattering characteristics of optical fibers of various types and manufacturers, the speed of obtaining tension plots can also be increased. Since the approximate value of the Brillouin frequency shift is calculated already at the initial steps of the measurement process, preliminary dependences of the tension distribution along the length of the fiber will be constructed rather quickly. [ABSTRACT FROM AUTHOR]

Phase encoding in quantum key distribution (QKD) enables long-distance information-theoretic secure communication in optical fibers. We present a novel theoretical model characterizing errors from various sources in practical phase encoding-based QKD systems, namely the laser linewidth, detector dark counts, and channel dispersion. This model provides optimized optical pulse parameters and less distortion in pulses, which eliminates system imperfections and leads to a reduced quantum bit error rate (QBER) for practical QKD scenario. This analysis is applicable to various fiber-based phase and time encoding protocols. In particular, we implement this to a differential phase shift (DPS) QKD scheme operating at a 2.5 GHz clock, which produces a secure key rate of 193 bits/s at a fiber length of 265 km and an unprecedented QBER < 1 % up to 225 km length with standard telecom components. We show that by adjusting the quantum efficiency and dark count rates of detectors, proposed system can establish secure keys up to 380 km distance using standard telecom grade fiber with a QBER of 1.48%. Moreover, the system is compatible with existing optical fiber networks and capable of establishing a secure key exchange between two cities 432 km apart using ultra-low-loss (ULL) specialty fiber. [ABSTRACT FROM AUTHOR]

Oceans are crucial to human survival, providing natural resources and most of the global oxygen supply, and are responsible for a large portion of worldwide economic development. Although it is widely considered a silent world, the sea is filled with natural sounds generated by marine life and geological processes. Man-made underwater sounds, such as active sonars, maritime traffic, and offshore oil and mineral exploration, have significantly affected underwater soundscapes and species. In this work, we report on a joint optical fiber-based communication and sensing technology aiming to reduce noise pollution in the sea while providing connectivity simultaneously with a variety of underwater applications. The designed multifunctional fiber-based system enables two-way data transfer, monitoring marine life and ship movement near the deployed fiber at the sea bottom and sensing temperature. The deployed fiber is equally harnessed to transfer energy that the internet of underwater things (IoUTs) devices can harvest. The reported approach significantly reduces the costs and effects of monitoring marine ecosystems while ensuring data transfer and ocean monitoring applications and providing continuous power for submerged IoUT devices. [ABSTRACT FROM AUTHOR]

This study explores the impact of the integrability criterion on nonlinear Schrödinger (NLS ) equations with mixed derivatives, specifically focusing on the Rangwala–Rao ( R R ) equation formulated by A. Rangwala in 1990. The objective of this investigation is to enhance our understanding of the dispersion effect by examining novel soliton wave solutions and their interactions. By doing so, we aim to gain insights into the behavior of the slowly changing envelope of the electric field and pulse propagation in optical fibers. To achieve this, we employ recent computational approaches, including the Sardar Sub-equation and modified rational methods, to identify distinctive solitary wave solutions for the analyzed model. The significance of studying the Rangwala–Rao equation lies in its potential contribution to the development of more efficient optical fiber communication systems. The presented numerical solutions in this paper showcase the dynamic nature of optical fiber pulse propagation, thereby highlighting the originality of this work compared to existing scholarly contributions. [ABSTRACT FROM AUTHOR]

Optical layer attacks on optical fiber communication networks are one of the weakest reinforced areas of the network, allowing attackers to overcome security software or firewalls when proper safeguards are not put into place. Encrypting data using a random phase mask is a simple yet effective way to bolster the data security at the physical layer. Since the interactions of the random phases used for such encryption heavily depend on system properties like data rate, modulation format, distance, degree of phase randomness, laser properties, etc., it is important to determine the optimum operating conditions for different scenarios. In this work, assuming that the transmitter and the receiver have a secret pre-shared key, we present a theoretical study of security in such a system through mutual information analysis. Next, we determine operating conditions which ensure security for 4-PSK, 16-PSK, and 128-QAM formats through numerical simulation. Moreover, we provide an experimental demonstration of the system using 16-QAM modulation. We then use numerical simulation to verify the efficacy of the encryption and study two preventative measures for different modulation formats which will prevent an eavesdropper from obtaining any data. The results demonstrate that the system is secure against a tapping attack if an attacker has no information of the phase modulator and pre-shared key. [ABSTRACT FROM AUTHOR]

Data security is essential for applications that require a significant level of data privacy. Online banking and government mailing are good examples of data with security requirements. This paper demonstrates an enhanced secure fiber-optic communication system based on chaos using Optisystem 7.0 software. A 10 Gb/s externally modulated signal is transmitted over 100 km of standard single-mode fiber. The modulated data is hidden by a chaotic optical signal generated by controlling the rate parameters of a semiconductor laser. The results showed that chaos degrades the overall system performance and limits the transmission distance to 70 km. A chirped fiber-Bragg grating and erbium-doped fiber amplifier are introduced to compensate signal dispersion and to increase the transmission distance to 104 km (80% enhancement). Also, the results revealed that maximum Q-factor of 4.2 and a minimum bit error rate of 10 - 8 are successfully recovered the data at the receiver. [ABSTRACT FROM AUTHOR]

In this paper, we propose a dual-channel broadband photonic-crystal fiber polarization filter with high loss based on surface plasmon resonance. We carefully design gold-coated elliptical air hole structure to improve the confinement loss and the isolation of x-polarized and y-polarized guided modes. Multi-order plasmonic modes are excited to broad the filtering band. Moreover, in view of our simulation results, we demonstrate that plasmonic resonance occurs at the wavelength, where birefringence abnormally changes; also, complete and incomplete mode coupling are able to be distinguished by birefringence. At communication wavelengths of 1550 and 1318 nm, the calculated confinement loss of x-polarized and y-polarized core modes are 744.63 and 1089 dB/cm, with crosstalk up to – 1282.54 and 2233.46 dB, respectively. The proposed dual-channel polarization filter will be a good choice for optical fiber communication. [ABSTRACT FROM AUTHOR]

This article discusses the application of a new type of modem with pseudo-noise coding and additional tone modulation, developed for the comparison of reference time scales over satellite communication channels. Experimental studies have compared the time scales of hydrogen masers from the composition of the State Primary Standard of Units of Time, Frequency, and the National Time Scale GET 1-2022 over an optical communication channel using the modems under consideration. As a communication channel, fiber-optic lines of different lengths were used, along which the two-way signal was transmitted. The output radio frequency signals of the modems, with the use of optical transmitters connected to the ends of the fiber lines, were transmitted counter-currently at an optical carrier frequency with a wavelength of 1.55 μm. The demodulation of optical signals into the radio frequency range was implemented at the ends of the fiber lines by optical receivers. The results of an experimental evaluation of type A indefiniteness by comparing time scales along fiber-optic lines of 50-km, 100-km, and 200-km lengths are presented. On a line 200-kmlong, the type A measurement uncertainty when comparing time scales does not exceed 3 ps in the daily measurement interval. The experiments revealed that implementing the method of comparing time scales with modems with pseudo-noise coding and additional tone modulation is possible over a 200-km-long fiber-optic line without intermediate optical amplifiers. This finding opens up the prospect of creating cascaded comparison systems for time scales of remote standards over fiber-optic communication lines with fewer intermediate optical amplifiers. [ABSTRACT FROM AUTHOR]

It is extremely important to accurately measure the liquid level as a process variable of a storage tank used by any plant. The transmitted electrical signal from a liquid level transducer or any other transducer to a remote indicator or controller may sometimes suffer from the measurement error due to its contamination with noise signal. This may be easily avoided by using modern optical fiber communication technique wherein we see the production of optical signal from the transducer output and its noise free communication through fiber-optic cable. In thie present paper, an opto-electronic liquid level transmission technique has been proposed for liquid which is conducting in nature and generally, collected in a storage tank. The electronic part of the transmitter unit consists of a modified capacitive transducer with a signal conditioner unit which produces an electrical DC output voltage which is linearly related with the level of the conducting liquid in the storage tank. This DC voltage is transformed into an optical signal with the help of Mach–Zehnder Interferometer (MZI) based electro- optic converter. Generated Optical signal may be dispatched to any location which is remote in nature by using fiber optic cable. Thus, various types of measurement error observed in the conventional capacitive level transmitter are minimized by using the proposed system. In the preset paper, a prototype model of the proposed system has been designed and developed to test its functionality. A good linear characteristic of the normalized optical output in support of the derived equations is observed. [ABSTRACT FROM AUTHOR]

In this paper, we present a tanh apodized FBG as a dispersion compensator in optical fiber communication systems. This grating is integrated as a hybrid system of four cascaded apodized FBGs with soliton transmission technique. This enhances the linewidth of the light source to get the most out of transmission per-channel bit rate of 9.687 Tbps at a temperature of 20 °C, a relative refractive index difference of 0.002, a Germania doping ratio of 0.2, and a signal wavelength of 1.65 µm. [ABSTRACT FROM AUTHOR]

The main focus of this research is to acquire innovatory solutions to the resonant fractional nonlinear Schrödinger equation (R-FNLSE) with quadratic cubic nonlinearity. This objective has been attained by applying two most reliable and efficient integrating techniques namely: the (G ′ G 2) -expansion technique and an equivalent form for the (exp (- ϕ (ξ))) -expansion technique. The beta derivative has been used for describing the fractional effects involved in the proposed model. The R-FNLSE plays an important role in the theory of fiber optic and telecommunication. The results received by employing the proposed analytical approaches have been classified as hyperbolic, rational and trigonometric solutions. On the basis of linear stability, the proposed model has been investigated for modulation instability. The dynamics of the extracted solution has also been tested by 3D plots and line plot. [ABSTRACT FROM AUTHOR]

The possibility of determining the difference in gravitational potentials and orthometric heights in the Earth's field based on measurements of the phase difference of laser radiation in an optical fiber is proposed and investigated in this study. Such a phase difference is attributed to the effect of the gravitational delay of light waves. A block diagram of a measuring complex designed to measure the phase difference of light waves caused by this effect is proposed. The measurements use two coherent light waves from a single laser, each propagating along a separate fiber-optic communication line. The composition of each fiber-optic communication line includes the same coils of a long optical fiber, spaced apart in height. The analysis of the factors influencing the phase relations of waves propagating along two communication lines of the measuring complex is performed. The phase effects of the delay, caused by the influence of the true gravitational field of the Earth, and the influence of the fields of inertial forces and gyroscopic effects due to the Earth's rotation are determined. Methods for suppressing interfering effects are proposed. The achievable errors in measuring the differences in gravitational potentials and corresponding orthometric heights are estimated. With a fiber length in coils of 100 km and a height difference of 100 m, the errors are 0.2 m2/s2 and 2 cm, respectively. The measuring complex under study is called a laser gravipotentiometer. It is an optical analog of the well-known radio-frequency quantum-level unit, but it does not require ultrastable frequency and time standards. The research results of the proposed measuring complex are relevant for the development and improvement of measuring instruments for the parameters of the Earth's gravitational field and a means of the high-precision synchronization of time scales of remote standards. [ABSTRACT FROM AUTHOR]

This paper extends previous studies work on the application of Machine Learning (ML) to distortion compensation in optical communication systems with optical fibers nonlinear coefficients (γ) that exceed current industry standards e.g. γ > 1.4 W - 1 k m - 1 . To quantify the improvement afforded by ML methods under different transmission conditions the procedures are applied to a model of a typical single-frequency optical communication system with, a 3200 km fiber length, double polarization, and a 16-QAM modulation format. The performance of both transmitters and receivers that incorporate Neural Networks (NNs) are then examined over a wide range of γ values. In all cases considered, the system Q-factor is improved although the degree of enhancement is dependent on the signal to noise ratio. The ML structures that were investigated include Siamese neural networks (SNN) implemented at the receiver end as well as two-stage architectures that employ NNs at the transmitter together with a classifier at the receiver side. Classifiers ranging from simple decision tree structures to boosting, forests, extra trees, and Multi-layer perceptron (MLP) were further examined and found to provide significant enhancement for γ > 4 W - 1 k m - 1 . The optimal performance for highly nonlinear systems was achieved for two-stage systems with random forest or extra tree classifiers. Finally, empirical equations for each ML technique were derived that relate the Q-factor enhancement and the value of γ , and the number of triplet terms that are input into the neural network. These results could potentially be employed to relax manufacturing constraints and accordingly reduce system costs. [ABSTRACT FROM AUTHOR]

GaSb-based type-I heterostructure exhibited low optical gain hence further investigations are needed to study the technique for tuning the optical gain characteristics. In this paper, the main emphasis has been given to studying the optical gain characteristics and lasing wavelength of GaSb-based Type-I AlSb/InGaAsSb/AlSb heterostructure under uniaxial strain (0–8 GPa) the variable well width ranging from 2.5 to 4.5 nm and carrier density ranging from 5 × 1012 cm−2 to 9 × 1012 cm−2at room temperature. It was observed that the wider quantum well width can enhance the optical gain with redshift in wavelength. For the proposed heterostructure maximum optical gain is achieved when the quantum well size is 4.5 nm and carrier concentration is 9 × 1012 cm−2. The calculations were performed using the two-band k.p model and Fermi Golden Rules. Computational analysis suggests that the designed heterostructure is compatible as an optical source in the telecom window of optical fiber communication. [ABSTRACT FROM AUTHOR]

Hybrid plasmonic waveguides have emerged as one of the most emerging tools for long-range subwavelength optical guidance. We propose the coupling of a hybrid plasmonic (HP) mode into a silicon tip. The HP mode is made to confine in the silicon tip through lateral as well as a vertical coupling, which provides moderately good field enhancement with long-range propagation. The lateral coupling exhibits a field enhancement of more than 200 in a silicon tip with a propagation length of 110 μm. Field enhancement in the vertically coupled case is 25 with a propagation length of 1.1 mm. In both cases, mode area remains around 50–60 nm2. In addition, both structures show broadband propagation of HP modes where propagation length remains long over a broad range wavelength. The proposed waveguide structures can be useful in realizing nanophotonic devices for broad range of applications including spectroscopy, optical fiber communication and bio-chemical sensing. [ABSTRACT FROM AUTHOR]

The aim of this study is to present a proposed chromatic dispersion compensation model for single mode optical fiber. The proposed model consists of 4-stages of cascaded identical linear chirped fiber Bragg grating (CFBG) in post-compensation connection scheme. It is based on differential phase shift keying modulation format. To evaluate the performance of the proposed model, a comparative study is conducted using offset quadrature phase shift keying modulation technique. This comparative study includes four cases with and without using CFBG. For system performance evaluation, a 10 Gbps wavelength division multiplexing link is simulated at a distance of 70 km under conventional operating parameters. Optisystem 7.0 has been used for simulation and evaluation process. Quality factor (Q-factor) and bit error rate (BER) are used as evaluation metrics. The proposed model shows the best performance in case of using CFBG compared to the other cases. A maximum Q-factor of 7.22, and a corresponding minimum BER of 2.59 × 10−13are obtained. The proposed system performance is enhanced by at least 53% as compared to related work. [ABSTRACT FROM AUTHOR]

Optical communication system is preferred over microwave and radio frequency communication system because of license free operation. Simulative analysis of 10gbps Optical Communication using different optical bands of L-Band S-Band, E-Band and C-Band under different attenuation condition has been performed in this paper. The Free Space Optics system has been analyzed with transmission distance of 1 km using Optical Wireless Communication channel and the effect of variation in attenuation value in the scenario of different weather conditions (clear, haze, rain and fog) were also examined. The Optical Fiber Communication is also examined under conditions of attenuations due to physical imperfections. The cross-layer Artificial Intelligence Framework is implemented to perform the prediction of different optical communication. The diffused channel is studied by varying the parameters of transmitter half angle and the distance of separation between the transmitter and the receiver. The attenuation effects of the links are also taken into consideration. Bit Error Rate and Quality factor performance of the different optical links are carried over at different wavelengths; thus the best link for the particular wavelength and the distance is identified. [ABSTRACT FROM AUTHOR]

In this article, a solid silica core plasmonic photonic crystal fiber-based polarization splitter is proposed to concurrently achieve a short length, good extinction ratio, and acceptable bandwidth at communication wavelength. The model consists of dual-core design with a series of air holes arranged symmetrically. The surface plasmon resonance (SPR) active metal is metallic gold. Resonant coupling between the second-order surface plasmon polaritons (SPP) mode and the core-guided modes can improve the coupling characteristics of the developed dual-core photonic crystal fiber (DC-PCF). A complete analysis was performed using the finite element method for wavelengths from 1200 to 2100 nm. The splitter extinction ratio at the 1.55 µm wavelength is 149.9 dB, which is better than − 20 dB. The splitter has a short length of 34 µm and a bandwidth of 200 nm. In comparison to the designed DC-PCF with gold wire, a gold layer is put into the designed DC-PCF to achieve excellent splitting performance and reasonable bandwidth. Therefore, the proposed design proves to be highly applicable in fiber-optic communication systems. [ABSTRACT FROM AUTHOR]

In the development of orbital angular momentum (OAM) mode division multiplexing, the capacity of optical fiber communication must be improved. However, owing to dispersion and confinement loss, many OAM modes do not propagate stably over a long distance in optical fibers. In this work, the effects of the size, number, shape, number of layers, and layer spacing of air holes in the cladding of the fiber on the dispersion and confinement loss are analyzed based on a simple structure. The trends are studied and summarized to facilitate the design of optical fibers to achieve stable transmission of OAM modes over a long distance. [ABSTRACT FROM AUTHOR]

This article negotiates the investigation of optical pulses with the Biswas-Arshed equation in birefringent fibers that involves a two-component form for vector solitons in an optical fiber communication system. Various optical pulses are recovered in single and combo shapes like bright, dark, singular, bright-dark, and dark-singular solitons by the uses of the extended Fan-sub equation method (EFSEM). In addition, the hyperbolic, singular periodic waves, Jacobi's elliptic function solutions are also derived. This method is beneficial for solving the nonlinear partial differential equations (NLPDEs), because this method is not only useful for finding the new solitary wave solutions, but also gives us the solutions obtained previously by the usage of other techniques (Riccati equation, or first kind elliptic equation, or the generalized Riccati equation as mapping equation, or auxiliary ordinary differential equation method) in a combined approach. The constraints conditions to ensure the existence criteria of reported optical soliton solutions are also listed. The stability analysis of the studied model is also examined by utilizing linear stability theory. In addition, by selecting different parametric values, the physical representation of some achieved solutions is plotted in 3D and contour graphs with the help of Mathematica. The reported results show that the proposed method is effective, concise, straightforward, powerful, and it can be used to tackle some more complex nonlinear systems. [ABSTRACT FROM AUTHOR]

Over last decades, the free space optics (FSO) emerged as most prominent way of communication over radio frequency communication and microwave communication. The FSO works in the same way optical fiber cable (OFC) network works with the only difference that the optical beams were transmitted through the free space and not by using the OFC core i.e. the glass fiber. The presence of mist, fog, rain and clouds in the atmosphere directly affects the performance of FSO and the power of propagating signal is degraded significantly. Since the wavelength of propagating beam is comparable to size of fog particles, they mainly lead to atmospheric attenuation. To mitigate the impact of atmospheric attenuation on signals, the present study develops a spectrum slicing (SS)-wavelength division multiplexing (WDM) system with Pre and Post Amplification. The performance of the proposed SS-WDM-Pre and SS-WDM-Post scheme is analyzed and then compared with the traditional SS-WDM model in the Opti-system in terms of Q-factor and BER values. The analysis of the proposed and traditional scheme is done under varying attenuation and power signals during summer, winter, autumn and spring season.The comparative analysis proved that the performance of the proposed SS-WDM-Post and SS-WDM-Pre-model is more effective and efficient when compared with the traditional SS-WDM model in terms of Q-Factor and BER during all 4 seasons. [ABSTRACT FROM AUTHOR]

Methods for improving the accuracy of reference frequency and time signals transmission using a new fiber-optic modem with phase instability compensation are presented. Algorithms for transmitting a 1PPS pulse time signal with a synchronization error of no more than 200 ps are considered. The results of measurements of the Allan deviation during the transmission of a reference signal with a frequency of 100 MHz through a two-kilometer fiber-optic line with additional external temperature impact are presented. With the help of the developed fiber-optic line emulator, the accuracy of reference signals transmission for fiber lines up to 100 km long, as well as for various external impacts, has been estimated. A full-function device for transmitting and receiving reference frequency and time signals through a fiber-optic communication line up to 100 km long, the instability characteristics of which reach approximately 1–3·10–17 in the daily measurement interval, has been developed. [ABSTRACT FROM AUTHOR]

The performance of moment generating function approaches, specifically Chernoff bound (CB) and modified Chernoff bound (MCB), is examined and improved in this study. We evaluates and enhances the performance of a wavelength division multiplexing (WDM) technique for free-space optical (FSO) fibre communications based on passive optical network (PON) using the M-ary digital pulse-position modulation (M-ary DPPM) schemes under amplified spontaneous emission (ASE) noise effects, interchannel crosstalk (ICC), and atmospheric turbulence (AT). We use a data rate of 2.5 Gbps for eight channels over a PON/DWDM-FSO optical fibre system in the C-band with 100 GHz channel spacing start from 1550 nm. The results achieve 20 Gbit/s transmissions (2.5 Gbps × 8 channels). This is a technology that can have extended leverage, higher data rates, power-efficient, and is considered an ideal option for the provision of bandwidth for potential access networks. When compared to the CB at a low gain (G = 8), the MCB outperforms the Gaussian approximation at high gain (G = 30). Because of its superior performance at a high gain (G = 30), the MCB offers the tightest limit on the bit error rate (BER). In comparison to an equivalent on–off keying (OOK) non-return-to-zero (NRZ), the M-ary DPPM scheme with a coding level (M) of 2 improves average power about by 2.9 dB at a data rate of 2.5 Gbps on the 1550 nm wavelength and BER of 10 - 9 . The sensitivity of the M-ary DPPM modulation scheme remains improved over OOK in the presence of ICC. The lower power penalty is predicted to be approximately 0.2–3.0 dB in the DWDM-FSO systems for low coding level M = 2. We achieve a lower power penalty at 0.2–3.0 dB for the hybrid fiber DWDM/PON-FSO optical communication system at a BER of 10 - 9 . At a target BER of 10 - 12 , the hybrid OOK-NRZ/M-ary DPPM offers about 4–8 dB of optical signal-to-noise-ratio improvements over the M-DPPM of the WDM-PON/FSO link for strong turbulence. The results demonstrated that the M-ary DPPM and the optical relaying amplification technique are powerful treatments for mitigating the impacts of ASE noise, AT, and ICC. [ABSTRACT FROM AUTHOR]

This paper studies Radhakrishnan-Kundu-Laksmannan equation which is used to describe the pulse propagation in optical fiber communications. By using improved modified extended tanh-function method various types of solutions are extracted such as bright solitons, singular solitons, singular periodic wave solutions, Jacobi elliptic solutions, periodic wave solutions and Weierstrass elliptic doubly periodic solutions. Moreover, some of the obtained solutions are represented graphically. [ABSTRACT FROM AUTHOR]

This paper builds exact optical solitons to the coupled of nonlinear equations which describes the pulse propagation in birefringent optical fibers with the effects of ellipticity angle and coupling coefficient. By adopting the new Sardar sub-ODE method, diverse optical solitons as W-shaped bright, dark optical solitons, trigonometric function and singular function solutions have been secured. To show out the warranty of the stability of the acquired results, we examine the effects of the ellipticity angle and coupling coefficient on modulation instability. It is noted beside of the linear and circular birefringence, for θ = 45 o , it is exhibited unstable zone where MI growth rate. To enroll the effects of the coupling coefficient on MI growth rate, we fixed a value of the ellipticity angle θ = 45 o . In Figs. 6 and 10, we acquired some new behavior of the MI gain compared to Houwe et al. (2021). These results show out stable/unstable zones compared to Ablowitz and Horikis (2017), Houwe et al. (2021). Moreover, these results will be helpful in nonlinear optical fibers to explain the communication over long distance and optical fibers design. [ABSTRACT FROM AUTHOR]

Photonic crystal fibers (PCFs) which can transmit orbital angular momentum (OAM) modes are attractive to optical communication due to the large capacity and flexible structure. Herein, a method is proposed to optimize a simple fiber structure by changing the thickness of the annular area. The changes in the effective index, effective index difference, dispersion, effective mode area, nonlinear coefficient, numerical aperture, mode purity, and walk-off length in the thickness range of 2.0 μm to 2.5 μm are determined, compared, and analyzed systematically. The distance between the square air holes and central air hole is the better parameter to optimize the dispersion, effective mode area, and nonlinear coefficient, whereas the radius of the central air hole is more suitable for optimizing the NA, OAM purity and walk-off length. The optimization method and results have great value pertaining to the design and improvement of PCFs for transmission of OAM modes. [ABSTRACT FROM AUTHOR]

In this paper, an ultra-broadband microstructure fiber filter is proposed and its properties are studied by full vector finite element method. Numerical results show that the effective modal index of x-polarized core mode (PCM) is much larger than those of surface plasmon polariton modes (SPPMs) in gold-coated areas. These index mismatches weaken the x-PCM's couplings with SPPMs to guarantee a very low confinement loss. As to the filtered y-PCM, it resonates with all the first three lowest order SPPMs, which is the first time to the best of our knowledge. Further studies show that better filtering performances can be achieved by complete resonances between the filtered y-PCM and 1st, 0th order SPPMs and optimized distribution of the resonant wavelengths. Through parameter optimization, an ultrabroad high loss band with loss no less than 123.49 dB/cm has been achieved within 1.1–2.0 μm. Taken extinction ratio 20 dB as criteria, a 1350 nm bandwidth can be reached within only 0.7 mm filtering length. Its operational range covers the entire O + E + S + C + L + U bands. This filter can find promising applications in the areas of optical communication and fiber sensing. [ABSTRACT FROM AUTHOR]

The saturated gain performance of the two-pump fiber optical parametric amplifier (2-P FOPA) in the presence of random dispersion fluctuation as well as fourth-order dispersion coefficient are investigated. The gain spectra of the 2-P FOPA is simulated by solving the coupled equations numerically, considering the dispersion fluctuations along the fiber as a stochastic process with a given standard deviation and correlation length. The gain performance of 2-P FOPA is analysed with the variation of correlation length, standard deviation and fourth-order dispersion coefficient, respectively. It shows that, the gain saturation curves of 2-P FOPA exhibit obvious differences in the presence of dispersion fluctuations and fourth-order dispersion coefficients. The peak gain reduces with the increase of the standard deviation and the reduction is higher in case of shorter correlation lengths, also the variations of 2-P FOPA saturation powers are affected by the standard deviation and correlation length significantly. In addition, the performance of the 2-P FOPA varies greatly while considering the fourth-order dispersion coefficient, where the peak gain remains the same, but the 3 dB bandwidth is wider with considering the fourth-order dispersion coefficient. The numerical analysis is meaningful for the research of 2-P FOPA saturated gain performance, which having attracted great research interests in the optical fiber communication systems. [ABSTRACT FROM AUTHOR]

We propose 1 state and 2 state multi-step Kalman filters (MKFs) to estimate and compensate CFO, LPN and NLPN in long-haul coherent fiber-optic communication systems. The proposed filters generate state estimates once every m symbols and therefore operate at a reduced sampling rate compared to conventional KFs that perform symbol by symbol processing. No computations are performed to obtain phase estimates of the intermediate m - 1 samples; instead, the present and previous estimates are averaged and used to derotate the intermediate m - 1 samples which are then demodulated to recover the transmitted symbols. This reduces the computational load on the receiver DSP. Further, in order to improve estimation accuracy, we adaptively vary the process noise covariance Q. Simulation results of 200 Gbps PDM 16 QAM system over 12 spans shows that the proposed 1 state MKF can reduce the sampling rate requirement by a factor of m = 20 with Q-factor degradation of 1.32 dB compared to single-step KF at linewidth of 100 kHz. The 2 state MKF tracks PN and CFO with a maximum step size of m = 10 for a CFO of 100 MHz at linewidth of 100 kHz. We also study the dynamic performance of the proposed algorithms by applying step change to CFO. The 2 state MKF with adaptive Q is able to track a step change of 400 MHz of CFO with m = 1 and 3 with high estimation accuracy but slower convergence time compared to the non-adaptive 2 state MKF. Finally, we study the computational requirements of the proposed MKFs and show that they offer significant reduction in computations compared to single-step KF thus making the proposed filters suitable for hardware implementation. [ABSTRACT FROM AUTHOR]

The problem of information protection against unauthorized access is considered and the results of a comparative analysis of methods for extracting information from an optical fiber are presented. A method for detecting the formation of channels of information leakage, which is performed in various ways, is proposed for the successful struggle against unauthorized access. Among the analyzed methods for forming information leakage channels in a fiber-optic communication line, the simplest method involves bending the optical fiber to disturb the conditions for the total internal reflection. In this case, the monitoring system must track the introduced losses made in order to detect fiber bends. [ABSTRACT FROM AUTHOR]

In spatial division multiplexing (SDM)-based communication systems, each spatial mode can act as an independent information-bearing carrier capable of scaling the total transmission capacity by several orders of magnitude. It has been reported that in SDM networks the signal amplitude depends upon the optical-path-length (OPL) difference between the various optical modes. In this work, we realize SDM technique using a multimode fiber (MMF), because MMFs have a potential to increase transmission capacity drastically by transmitting signals over large number of modes separately. The system performance is analyzed on the basis of following parameters: visualizer spatial profile, mode index profiles, fiber transfer function, refractive index profile, bit error rate, and quality factor. Also we measure changes in the optical path length due to a phase-shifting laser beam. We conclude that MMFs have huge scope for future ultrahigh-capacity transmission systems employing SDM. [ABSTRACT FROM AUTHOR]

Problems requiring high-precision comparisons and synchronization of time scales (TS) of remote time and frequency standards are analyzed. The prospects of using fiber-optic communication lines to solve these problems are considered. Data on maximum operating distances and accuracy characteristics of TS comparison systems using fiber-optic communication lines are given. It is shown that the range of existing systems is not sufficient for solving a number of relevant problems. A method for amplifying optical signals in an optical fiber using the stimulated Raman scattering (SRS) effect is proposed. The application of the Raman amplifier in telecommunication systems is considered. A method is suggested for using SRS to amplify the optical signals of TS comparison systems. A scheme is proposed for a system of one- and two-way TS comparisons of distant objects using signal amplification based on the SRS effect realized using two-way counter-pumping. The operational principle of the system is described along with the procedure for determining the divergence in the TS of remote objects. The results of estimating the error and range of systems of one- and two-way comparisons of time scales using the Raman amplifier are presented. It is shown that the implementation of Raman amplification in the equipment of such systems will allow their range to be increased by more than three times without reducing system accuracy. [ABSTRACT FROM AUTHOR]

Problems that arise in the course of attempting to determine and monitor an optical fiber, the medium of transmission of fiber-optic communication systems, are considered. One of the controllable parameters is the cut-off wavelength of a single-mode optical fiber. The cut-off wavelength defines the minimal wavelength of optical radiation at which an optical fiber supports only a single propagated mode, i.e., it functions in a single-mode regime. The problem of determining the cut-off wavelength of an optical fiber used in fiber-optic communication systems is critical, since in a multi-mode regime of operation of an optical fiber its throughput decreases as a consequence of inter-mode dispersion. Methods of measuring the cut-off wavelength of an optical fiber are considered. A model of a new high-precision apparatus for measurement of the cut-off wavelength of an optical fiber is proposed. The measurements are performed on the basis of the reference bending method described in GOST R MEK 60793-1-44-2013. The precision characteristics of the newly developed apparatus are analyzed and a quantitative assessment of the measurement error is obtained. [ABSTRACT FROM AUTHOR]

Quantum computing and quantum communication, have been greatly developed in recent years and expected to contribute to quantum internet technologies, including cloud quantum computing and unconditionally secure communication. However, long-distance quantum communication is challenging mainly because of optical fiber losses; quantum repeaters are indispensable for fiber-based transmission because unknown quantum states cannot be amplified with certainty. In this study, we demonstrate a versatile entanglement source in the telecom band for fiber-based quantum internet, which has a narrow linewidth of sub-MHz range, entanglement fidelity of more than 95%, and Bell-state generation even with frequency multimode. Furthermore, after a total distribution length of 20-km in fiber, two-photon correlation is observed with an easily identifiable normalized correlation coefficient, despite the limited bandwidth of the wavelength converter. The presented implementation promises an efficient method for entanglement distribution that is compatible with quantum memory and frequency-multiplexed long-distance quantum communication applications. Quantum technologies have seen a remarkable development in recent years and are expected to contribute to quantum internet technologies. The authors present an experimental implementation over commercial telecom fibres of a two-photon comb source for quantum communications with long coherence times and narrow bandwidth, which is used in a 20 km distribution experiment to show the presence of remote two-photon correlations. [ABSTRACT FROM AUTHOR]