Studying the properties of double-clad active cone optic fibers (original) (raw)
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An algorithm for the analysis of the double-clad fiber design is presented. The algorithm developed in the MATLAB computing language, is based on ray tracing method applied to three-dimensional graphics figures which are composed of a set of planes. The algorithm can evaluate an arbitrarily large number of ray paths calculating the corresponding pump absorption in each of the fiber elements according to the Lambert–Beer law. The beam path is evaluated in three dimensions considering the losses by reflection and refraction both at the fiber faces and within the fiber. Due to its flexibility, the algorithm can be used to study the ray propagation in double-clad fiber with: i) variable geometries of the inner clad and the core; ii) different position of the core inside the inner clad; and iii) bending and tapper effects.
Analytical Analysis of ray characteristics inside the optical fiber
In this paper we obtain solution of the ray equations in a parabolic and elliptical refractive index profile. We studied the various conditions for the suitable propagation of ray inside the fiber. A comparison is also made between the ray propagating in elliptical and parabolic refractive index profile.
Numerical Modeling of Pump Absorption in Coiled and Twisted Double-Clad Fibers
IEEE Journal of Selected Topics in Quantum Electronics, 2016
We report the analysis of multimode pump absorption in double-clad rare-earth-doped fibers under realistic bending conditions. The finite-element beampropagation method is used for the analysis. The fiber bending is approximated by the transformation of the refractive index profile of the fiber. Double-clad fibers of hexagonal, circular and stadium-like cross-sections are studied as examples. In addition, the double-clad waveguide structure of a two-fiber bundle is investigated. Simulations show that the bending effects cannot be neglected in double-clad fiber multimode pump propagation analysis and optimization. The reported rigorous numerical model opens new way to design double-clad fibers and to optimize the pump absorption efficiency. We show that high pump-absorption efficiency better than the ideal (ergodic) limit, can be achieved by simultaneous coiling and twisting of the double-clad fiber.
Simulations of Pump Absorption in Tandem-Pumped Octagon Double-Clad Fibers
IEEE Photonics Journal, 2021
The cladding pumping within a double-clad fiber structure is an effective technique to convert high-power multimode beam into high-power, almost diffraction limited beam. Since the pump efficiency is limited by the presence of higher skew-ray modes, geometrical perturbations are used to scramble the modes and to achieve a higher overlap of the electromagnetic field with the doped core. In this paper, the combined effect of fiber coiling and twisting is investigated in the double-clad fiber structure with the octagonal shape of an inner cladding. Electromagnetic field propagation through fibers with different cross-section areas, bending radii and twisting rates is numerically simulated using finite element beam propagation method. Holmium-doped double-clad fiber pumped in tandem configuration at wavelength 1950 nm is selected as an example. Nontrivial dependence of pump absorption on bending radius with the presence of local maxima is revealed. The observed impact of fiber coiling and twisting increases with the size of the cross-section area of the inner cladding.
Numerical Simulation of Radiation from Multimode Optical Fibers
Radiophysics and Quantum Electronics, 2005
We obtain an asymptotic expression for calculation of radiation fields of the waveguide modes of a multimode fiber with a step-like profile of the refractive index at high normalized frequencies. The distribution of intensity of the output radiation is calculated numerically. Statistical characteristics of the calculated speckles are found and compared with the experiment. Rigorous calculation of the intensity distribution of radiation from a multimode optical fiber in the far diffraction region with allowance for the edge effects is a complicated problem [1, 2]. If the number of propagating waveguide modes is large, then application of the classical numerical methods requires long computation time. Therefore, it is difficult or even impossible to implement such methods on a personal computer. For optical fibers (OFs) with step-like profiles of the refractive index, the problem under consideration can be solved analytically using a number of approximations, which reduces the duration of calculations by several orders of magnitude. Correspondingly, new possibilities for studying the parameters of the output radiation by means of numerical simulation appear. Actually, the posed problem consists of two parts, namely, determination of the intensity of the electromagnetic field at the output end of the fiber and calculation of the field in the far diffraction region. The expressions for field intensity of separate waveguide modes are well known. For example, the longitudinal component E z of the electric field can be written as [3, 4] E z (r, ϕ, z) = A ls J l (u ls r/r 0) cos(lϕ + ϕ 0) exp(iβ ls z)/J l (u ls), where l and s are the azimuthal and radial indices of the mode, respectively, A ls is the normalization factor, J l is a Bessel function of the first kind of order l, r 0 is the radius of the OF core, r, ϕ and z are cylindrical coordinates, and u ls and β ls are, respectively, the eigenvalue of the characteristic equation and the axial propagation constant for the mode with indices l and s. For the classical numerical transformation, it is necessary to calculate beforehand the field at the OF output end by summing up the fields of all waveguide modes and, then, to determine the field in the far diffraction region. In the case of analytical solution, it is convenient to calculate at first the field of each waveguide mode in the far zone and, then, to perform summation with allowance for the phase and polarization. Due to the cylindrical symmetry of the initial distribution, it is expedient to use cylindrical coordinates when performing integration in the plane of the OF output end. The concept of calculating the directional pattern and the field intensities by the stationary-phase method is well known [5]. We neglect both the penetration of the fields of the waveguide modes into the fiber cladding and a change in the field as it escapes into free space and assume that cos θ ≈ 1, where θ is the angle of radiation escape. Representing the expression for a plane electromagnetic wave as a sum of Bessel functions [6] and following [5-7], we can reduce the considered problem of radiation escape to the well-known problem of radiation injection [6]. In
Optical fiber waveguides in radiation environments, II
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1984
This paper will review recent progress in understanding the behavior of optical fiber waveguides when they are exposed to ionizing radiation. Not only have the growth and recovery of the radiation-induced attenuations been thoroughly characterized, in some cases the defect centers which cause these absorptions have been identified, and means for reducing the radiation sensitivity of the fibers have become apparent. The behavior of the radiation-induced loss is described in terms of parameters such as fiber composition and dopants, fiber structure, wavelength and intensity of the light source, temperature, total dose, time after irradiation, dose rate, and radiation history.
Optical Fiber Applications [Working Title]
2019
dalajara, Mexico, is recognized for the desirable profile PRODEP, and is a member of both the National System of Researchers Level I and the consolidated research group Complex Systems, Optics and Innovation. Dr. Huerta-Cuellar has more than eight years' teaching experience at undergraduate, masters, and doctorate levels. He has made research stays in Mexico, Italy, Spain, Russia, and the United States of America. He has produced 31 indexed articles, five book chapters, and 12 congress articles. To date, he has directed and completed six theses at undergraduate level and two at masters level, and has a PhD in progress. Dr. Roghayeh Imani is a semiconductor physicist. Her main expertise is in nanostructured semiconductor growth, characterization, and optoelectronic devices. Parallel to experimental research, she is also studying computer modeling and simulation to design and predict new types of semiconductors. She received her bachelor and master degrees in physics, and obtained her undergraduate training at the Laboratory of Thin Film and Surface Physics. She was awarded her doctoral degree in Nanoscience-Physics in November 2015 from the Electrical Engineering Faculty of Ljubljana University. During her PhD program she conducted impressive research into the biomedical application of multifunctional nanostructured semiconductors, and in 2017 her PhD was selected as a top-10 research subject in Ljubljana University. So far, her postdoctoral research in Sweden has been focused on the development of optoelectronic devices based on nanostructured semiconductors. Contents Preface XIII Section 1 Preface After the invention of the laser in the 1960s, the appearance of optical fibers enhanced applications that required the transportation of light from one place to another. As is well known, one of the main applications of optical fibers is optical communications, which were initially inefficient. Over time, different groups of scientists and engineers have been working to improve the efficiency of information transmission in optical fibers with materials that reduce absorption to the greatest extent possible. However, a large number of applications have been developed for which light absorption is not a real problem since the distances for sending information can be very short. Therefore, the technological development of optical fibers, for short or long distances, has been applied to a variety of uses in different areas such as the armed forces, industry, medicine, scientific research, and of course in communications, to name a few. Among the large number of applications that exist in optical fibers are different types of sensors, medical equipment to perform invasive surgeries, devices for industrial applications used in difficult access situations, various toys, decorative lighting, long-distance communications, and optical amplifiers, among others. Because of their great potential in applications and the advantages they offer over other systems, optical fibers will continue to be the subject of scientific research and technological development.