Isotropic Optical Fiber Research Articles

Investigation of the Dimensions of Making Brillouin Laser in Optical Fiber

Optical fiber is a transparent material such as glass (silica) with plastic that can expel light from one end to the other, it has a much higher bandwidth than conventional cables which can be used for image data. It has the capacity to easily transmission of audio and other data with high bandwidth of up to 10 Gbps and above Nowadays optical telecommunications are the most important tools of data transmission due to their wider bandwidth, compared to copper cable, and less latency coppered to satellite telecommunications. In this paper, a fiber optic at speed of (6m)/min is made of an isotropic optical fiber (with similar physical properties on all sides) prefabricated with alight-sensitive core Geo2-B-Sio2.

Brillouin Interaction between Two Optical Modes Selectively Excited in Weakly Guiding Multimode Optical Fibers.

A multimode optical fiber supports excitation and propagation of a pure single optical mode, i.e., the field pattern that satisfies the boundary conditions and does not change along the fiber. When two counterpropagating pure optical modes are excited, they could interact through the stimulated Brillouin scattering (SBS) process. Here, we present a simple theoretical formalism describing SBS interaction between two individual optical modes selectively excited in an acoustically isotropic multimode optical fiber. Employing a weakly guiding step-index fiber approach, we have built an analytical expression for the spatial distribution of the sound field amplitude in the fiber core and explored the features of SBS gain spectra, describing the interaction between modes of different orders. In this way, we give a clear insight into the sound propagation effects accompanying SBS in multimode optical fibers, and demonstrate their specific contributions to the SBS gain spectrum.

Влияние радиуса изгиба на долговечность оптических волокон типа «Панда»

The research considers the possibility of applying the forced «aging» method used for single-mode cable optical fibers in accordance with IEC 60793-2-50 to confirm the reliability of the PANDA PM Specialty optical fiber under long-term bending. A comparison of the results of PANDA PM Specialty optical fiber with isotropic optical fibers, which differ in the diameters of the quartz cladding and polymer coating, is carried out. An analytical estimate of the lifetime is carried out.

Elliptically-Polarized Soliton Self-Frequency Shift in Isotropic Optical Fiber

Solitons are prevalent in various nonlinear physical systems. Optical solitons in optical fibers are exceptionally intriguing due to the multitude of both linear and nonlinear optical effects that are involved during their propagation. Here we demonstrate elliptically-polarized soliton self-frequency shift (SSFS) in a novel isotropic fiber, photonic-crystal (PC) rod. We combine three methodologies, i.e., experimental, numerical, and analytical, to elucidate the fundamental aspects of this novel physical process. Our results show that wavelength-shifted, elliptically-polarized solitons can be generated through the elliptically-polarized SSFS in PC rod. Our research sheds new light on the soliton physics.

Self-polarization effect in the middle point of an optical fiber

In this paper, we report both numerically and experimentally an unexpected phenomenon of self-polarization occurring in the middle point of an isotropic optical fiber when two uncorrelated partially polarized waves are simultaneously injected at the ends of the fiber. More precisely, we demonstrate that two counterpropagating waves of equal intensity exhibit a spontaneous organization of their polarization states around two pools of attraction just in the middle point of propagation, and then both recover a partially polarized state at their respective fiber outputs. The self-polarization effect then remains hidden within the optical fiber in the sense that no apparent sign of this process is detected at the fiber outputs. A geometric definition of the degree of polarization is used to measure the efficiency of the polarization phenomenon.

Light Absorption Induced in Undoped-Silica-Core Panda-Type Birefringent Optical Fiber by Pulsed Action of Ionizing Radiation

The evolution of radiation-induced absorption (RIA) of light at λ = 1.55 μmis compared after pulsed action of ionizing radiation at different probe light power in an undoped-silica-core Panda-type birefringent optical fiber and in an isotropic optical fiber drawn from the same preform before embedding the stress-applying rods.High efficiency of RIA photobleaching by the probe light at λ = 1.55 μm is revealed in the birefringent fiber.

Inscription and visualization of tilted fiber Bragg gratings

In this work the inscription and investigation of tilted fiber Bragg gratings induced in a single-mode isotropic optical fiber with increased photorefractivity are demonstrated. Using the Talbot interferometer and the KrF excimer laser system, tilted fiber Bragg gratings with different angles were fabricated, the spectra of the formed diffraction structures were analyzed, and their photographic images were taken with a confocal laser scanning fluorescence microscope in transmitted light. The calculated dependence of the tilt angle of tilted fiber Bragg gratings fabricated in the Talbot interferometer on the angle between the interference fringes created in the interferometer and the cross section of the optical fiber is experimentally verified.

Observation of Interaction of Spin and Intrinsic Orbital Angular Momentum of Light.

The interaction of spin and intrinsic orbital angular momentum of light is observed, as evidenced by length-dependent rotations of both spatial patterns and optical polarization in a cylindrically symmetric isotropic optical fiber. Such rotations occur in a straight few-mode fiber when superpositions of two modes with parallel and antiparallel orientation of spin and intrinsic orbital angular momentum (IOAM=2ℏ) are excited, resulting from a degeneracy splitting of the propagation constants of the modes.

Quantitative analysis of transcranial and intraparenchymal light penetration in human cadaver brain tissue.

Photobiomodulation (PBM) also known as low-level light therapy has been used successfully for the treatment of injury and disease of the nervous system. The use of PBM to treat injury and diseases of the brain requires an in-depth understanding of light propagation through tissues including scalp, skull, meninges, and brain. This study investigated the light penetration gradients in the human cadaver brain using a Transcranial Laser System with a 30 mm diameter beam of 808 nm wavelength light. In addition, the wavelength-dependence of light scatter and absorbance in intraparenchymal brain tissue using 660, 808, and 940 nm wavelengths was investigated. Intact human cadaver heads (n = 8) were obtained for measurement of light propagation through the scalp/skull/meninges and into brain tissue. The cadaver heads were sectioned in either the transverse or mid-sagittal. The sectioned head was mounted into a cranial fixture with an 808 nm wavelength laser system illuminating the head from beneath with either pulsed-wave (PW) or continuous-wave (CW) laser light. A linear array of nine isotropic optical fibers on a 5 mm pitch was inserted into the brain tissue along the optical axis of the beam. Light collected from each fiber was delivered to a multichannel power meter. As the array was lowered into the tissue, the power from each probe was recorded at 5 mm increments until the inner aspect of the dura mater was reached. Intraparenchymal light penetration measurements were made by delivering a series of wavelengths (660, 808, and 940 nm) through a separate optical fiber within the array, which was offset from the array line by 5 mm. Local light penetration was determined and compared across the selected wavelengths. Unfixed cadaver brains provide good anatomical localization and reliable measurements of light scatter and penetration in the CNS tissues. Transcranial application of 808 nm wavelength light penetrated the scalp, skull, meninges, and brain to a depth of approximately 40 mm with an effective attenuation coefficient for the system of 2.22 cm(-1) . No differences were observed in the results between the PW and CW laser light. The intraparenchymal studies demonstrated less absorption and scattering for the 808 nm wavelength light compared to the 660 or 940 nm wavelengths. Transcranial light measurements of unfixed human cadaver brains allowed for determinations of light penetration variables. While unfixed human cadaver studies do not reflect all the conditions seen in the living condition, comparisons of light scatter and penetration and estimates of fluence levels can be used to establish further clinical dosing. The 808 nm wavelength light demonstrated superior CNS tissue penetration.

Effect of Raman gain on the self-steepening characteristic in isotropic fibers

Under the condition that the light pulses meet the slowly varying function pulses, the higher-order nonlinear Schrödinger equation has been deduced by taking into consideration the Raman gain. The linear operator and nonlinear operator specific expressions are obtained using split-step Fourier numerical method. The Raman gain on the self-steepening of the Gaussian pulse has been simulated and then the result is compared with the self-steepening effect without taking into consideration the Raman gain when the pulse propagate in the isotropic optical fiber. Raman gain specific impact on the self-steepening of the Gaussian pulse has been obtained under different conditions. Results show that the Raman gain may affect the Gaussian pulse broadening, pulse peak attenuation as well as the oscillation of the edge. These influences depend on the parameters of self-steepening, input power, and dispersion coefficient.

Complete nonlinear polarization control in an optical fiber system

We consider the counterpropagating interaction of a signal and a pump beam in an isotropic optical fiber. On the basis of recently developed mathematical techniques, we show that an arbitrary state of polarization of the signal beam can be converted into any other desired state of polarization. On the other hand, an unpolarized signal beam may be repolarized into two specific states of polarization, without loss of energy. Both processes of repolarization and polarization conversion may be controlled by adjusting the polarization state of the backward pump.

Integrability of the Vector Short Pulse Equation

Using the Painlevé analysis preceded by appropriate transformations of nonlinear systems under investigation, we discover two new cases in which the Pietrzyk–Kanattšikov–Bandelow vector short pulse equation must be integrable due to the results of the Painlevé test. Those cases are technologically important because they correspond to the propagation of polarized ultra-short light pulses in usual isotropic silica optical fibers.

Simultaneous achievement of polarization attraction and Raman amplification in isotropic optical fibers.

We present a theoretical analysis and experimental demonstration of the combined effects of polarization attraction and Raman amplification in isotropic optical fibers. The polarization attraction process is based on four-wave mixing interaction of counterpropagating pump and signal waves. We show that this technique can be used for the design of a highly efficient nonlinear system that permits the simultaneous processing of repolarization and amplification of light waves in dielectric media.

Nonlinear polarization dynamics of counterpropagating waves in an isotropic optical fiber: theory and experiments

The nonlinear interaction between two intense counterpropagating laser beams in an isotropic optical fiber may lead to spatiotemporal polarization instabilities of both waves. Experiments with various mutual polarization arrangements and different powers of the two counterpropagating input beams showed that nonlinear birefringence may lead to significant polarization cross switching of both beams. In the case of two counterrotating circular input waves, the cross-polarization interaction of the beams led to the generation of a polarization kink or domain wall soliton. This soliton is formed by a superposition of counterpropagating waves that represent switching of the state of polarization of light between two domains where both waves are circularly polarized and corotating. The experimental observations are found to be in good agreement with the theoretical predictions.

Theoretical model for the transverse interference pattern of GRIN optical fiber using a laser sheet of light

A new technique (El-Ghandoor et al., Opt. Laser Technol. 31(7) (1999) 481–488) has been applied to study the shape of transverse interference fringes, instead of multiple beam Fizeau fringes (Marhic, Stein, Appl. Phys. Lett. 35 (1975) 1678–1682), from a GRIN optical fiber. In this technique, a laser light sheet is used to illuminate and pass directly through the optical fiber. Theoretical expressions are derived for the optical path differences of three groups of interference beams. The first one passes through the cladding, the core, and then the cladding once again; the second passes through the cladding only, and the third passes through the surrounding air. Theoretical expressions for the shape of transverse interference fringes formed across isotropic non-absorbing optical fibers are also calculated.

Spin-orbit interaction in the field of an optical vortex of a few-mode fiber

A quantum-mechanical analog of the spin-orbit interaction operator \(\hat V\) is constructed for the fields of optical CV vortices and TE and TM modes in an optical fiber. It is shown that the polarization correction δβ to the propagation constant, which is the mean value of this operator, is a measure of the “level splitting” of the propagation constant \(\tilde \beta \) in the scalar case. The difference in the operation of the individual parts of the operator \(\hat V\) on the fields of CV vortices and on the fields of TM and TE modes is indicative of the presence of two different physical processes — circular and linear birefringence in the locally isotropic optical fiber. The conversion of the “scalar” field \(\tilde e\) to a vector field e1 as a consequence of the spin-orbit interaction operator can be regarded as resulting from a re-radiation of the additional field e1 by the vortex field \(\tilde e\), which rotates around the optical axis of the fiber. In this picture the additional field e1 can be regarded as being a “relativistic” correction to the vortex field for the distortions of the main field \(\tilde e\) and arising as a result of the rotation of the field of the optical vortex in the medium of the few-mode fiber.

Rotating vector solitary waves in isotropic fibers

The properties of elliptically polarized solitary waves in isotropic optical fibers are investigated. Two families of polarized solitary pulses are identified, but only one of them is shown to be stable. These pulses are characterized by a fixed polarization pattern that rotates at a constant rate as the pulse propagates down the fiber. The evolution of the polarization of these pulses is important for the operation of short-pulse fiber lasers and other nonlinear devices.

A new numerical method for computing the optical characteristics of birefringent fibers

In this article, we present a new numerical method for solving vectorial Maxwell equations which makes it possible to study the birefringence of any geometric pattern of isotropic optical fiber. The distinguishing feature of this method is its use of an iterative process to determine the modes of propagation. The major advantage is the ease of the procedure since the various mathematical steps required can be performed by commercially available software.

Application of phase contrast microscopy to quantitative characterization of optical fibers

The application possibilities of the phase contrast method in investigations of both isotropic and anisotropic optical fibers are discussed. In particular, this method enables the core diameter and other geometrical parameters of graded-refractive-index (GRIN) fibers to be determined more accurately when combined with scanning microdensitometry. The refractive index profile of some fibers, especially that of monomode fibers, can be determined by using a negative phase contrast device if the difference Δ<i>n</i> between refractive indices of the fiber core and cladding is very small (smaller than 0.03). The result obtained is comparable to that offered by differential microinterferometry. In general, highly sensitive negative phase contrast microscopy, such as that based on the KFA device with soot phase rings (commercially available from the Polish Optical Works, Warsaw), permits us to observe extremely small optical inhomogeneities that cannot be revealed with the help of conventional microinterferometric techniques.

Third-order three-wave mixing in single-mode fibers: exact solutions and spatial instability effects

Exact solutions are presented to the steady-state coupled-mode equations that govern the nonlinear parametric interaction of a central-frequency wave with a pair of upshifted and downshifted sidebands in isotropic single-mode optical fibers. This solution accounts for pump depletion as well for as a possible phase mismatch among the waves. The existence is predicted of eigensolutions propagating unchanged along the fiber, which may be either spatially stable or spatially unstable, depending on the total power and the propagation-constant mismatch. The presence of spatially unstable eigensolutions dramatically affects the power exchange among the three waves. The physical implications of this instability for the frequency-conversion process, as well as its potential application to all-optical switching, are discussed.