Birefringent Optical Fiber Research Articles

Theory of nonlinear loop mirrors with twisted low-birefringence fiber

We analyze propagation in a nonlinear, birefringent optical fiber with twist. The results show that the polarization evolution is periodic, and they are applied to the analysis of a Sagnac interferometer. The period is calculated by using perturbation theory, and we find a condition for it to be independent of the initial polarization state. We derive a simplified set of equations to describe the nonlinear evolution of the phase. We give a useful way to visualize the behavior of the nonlinear optical loop mirror (as a function of birefringence, twist, length, and input polarization) in terms of the Poincare sphere.

Soliton propagation in a birefringent optical fiber with fiber loss and frequency chirping

We obtain the Lax pair for a coupled system where the fiber loss and pulse chirping terms exactly balance each other and thereby obtain single soliton solutions. The amplitude of the pulse is found to decrease in an exponential way with the pulse area always remaining a constant.

Measurements of Key Parameters for Birefringent Single-Mode Optical Fibers by Optical Frequency-Domain Interferometry

This Letter describes measurements of modal birefringence (MB) and polarization mode dispersion (PMD) of a birefringent single-mode optical fiber for use at 1.5 #x03BC;m in optical wavelength. Optical frequency-domain interferometry based on a fixed analyzer method is applied to the measurement of orthogonal polarization components of light guided in the fiber. An amplified spontaneous emission source having an optical wavelength range between 1520 and 1560 nm is used. A channeled interference spectrum is obtained to measure MB and PMD in turn. These two parameters are not frequency-dependent in the above optical wavelength range and MB = 4.0 #x00D7; 10#x2212;4 and PMD = 1.33 ps/m are obtained.

DYNAMICS OF SUPER-GAUSSIAN SOLITONS IN BIREFRINGENT OPTICAL FIBERS

The variational principle is employed to obtain the parameter dynamics of a super-Gaussian chirped soliton that propagates through birefringent optical fibers and is governed by the dispersion-managed vector nonlinear Schrödinger's equation. The waveform deviates from that of a classical soliton. The periodically changing strong chirp of such a soliton reduces the effective nonlinearity that is necessary for balancing the local dispersion. This study is extended to obtain the adiabatic evolution of the parameters of such a soliton in presence of perturbation terms.

Radiative losses due to pulse interactions in birefringent nonlinear optical fibers.

The transient evolution of two-polarization pulses in a birefringent nonlinear optical fiber, governed by coupled nonlinear Schrödinger (NLS) equations, is considered. The evolution is studied using a trial function consisting of coupled solitonlike pulses with varying parameters augmented by a radiative shelf in the Lagrangian formulation of the coupled equations, which yields ordinary differential equations for the pulse parameters. It is shown that including mass and momentum fluxes due to the radiative shelf is a requirement to obtain good agreement with full numerical solutions of the governing equations.

Fractal dependence of vector-soliton collisions in birefringent fibers

Vector-soliton collisions in birefringent nonlinear optical fibers are investigated. The underlying mathematical model is the non-integrable coupled nonlinear Schrödinger equations. It is shown that the exit velocity versus collision velocity graph has a fractal structure. When we zoom into different positions of this fractal, we get structures which are either a copy, a horizontal reflection or vertical reflection of the original structure. Collision dynamics in the zoomed-in windows and that in the original graph follow simple and well-defined patterns as well. We explain this fractal dependence of the collision by a novel resonance mechanism between translational motion of vector solitons and radiation modes which cause internal oscillations inside a vector soliton.

Dynamics of Gaussian and Super-Gaussian Solitons in Birefringent Optical Fibers

The variational principle is employed to obtain the parameters dynamics of Gaussian and super-Gaussian chirped solitons which propagates through birefringent optical fibers that is governed by the dispersion-managed vector nonlinear Schrodinger's equation. The waveform deviates from that of a classical soliton. The periodically changing strong chirp of such a soliton reduces the effective nonlinearity that is necessary for balancing the local dispersion. This study is extended to obtain the adiabatic evolution of the parameters of such a soliton in presence of perturbation terms.

Dynamics of Gaussian and Super-Gaussian Solitons in Birefringent Optical Fibers- Abstract

The variational principle is employed to obtain the parameters dynamics of Gaussian and super-Gaussian chirped solitons which propagates through birefringent optical fibers that is governed by the dispersion-managed vector nonlinear Schrödinger's equation. The waveform deviates from that of a classical soliton. The periodically changing strong chirp of such a soliton reduces the effective nonlinearity that is necessary for balancing the local dispersion. This study is extended to obtain the adiabatic evolution of the parameters of such a soliton in presence of perturbation terms.

The Use of Lorentz Group Formalism in Solving Polarization Effects of a Birefringent Single Mode Optical Fiber

A theoretical analysis on the polarization effects of a light beam propagating in a birefringent single-mode fiber is presented. We derive a system of differential equations representing the evolution of Stokes parameters and illustrate their application to polarization effects in a straight birefringent single mode optical fiber. The solutions to the set of equations are obtained using specifically the methods of the unified formalism for polarization optics which adopt the use of the Stokes–Mueller equation and the Lorentz group to model polarization phenomena in media such as optical fibers. The analytical results presented using this approach are identical to results obtained from other conventional methods. We observe the characteristic exponential decrease in the total intensity of the input light due to attenuation by the fiber.

Controlling a quantum communication system with synchronized nonlinear fiber ring resonators

We take advantage of suitable properties of nonlinear optical devices such as synchronized nonlinear fiber ring resonator and the effects of birefringence in optical fibers to construct a setup, using only optical fibers, for quantum communications. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 302–304, 2000

Polarized Chirped Soliton Oscillations in a Lossy Elliptically Low Birefringent Optical Fiber

Abstract Using a variational method, a new model of the nonlinear propagation of optical solitons generated from semiconductor lasers through a lossy elliptically low birefringent fiber, is presented within the frame-work of a system of coupled nonlinear Schroedinger (CNLS) equations. This model demonstrates polarized soliton oscillations in a lossy elliptically low birefringent fiber.

Analytical description of backscattered states of polarization in polarization optical time-domain reflectometry measurements on uniformly twisted linearly birefringent optical fiber.

We present a detailed derivation of the locus of Rayleigh backscattered states of polarization for polarization optical time domain reflectometry in uniformly twisted optical fiber with intrinsic linear birefringence. The locus is algebraically a quartic whose topology is determined by the relative orientation on the Poincaré sphere of the input SOP and the effective birefringence vector. We present an analysis that indicates how experimental data may be interpreted, through geometric parameters of the locus, for evaluating the fiber parameters. The analysis also indicates the minimum number of experimental data points required for meaningful values for the fiber parameters to be obtained.

Simultaneous achievement of suppression of modulational instability and reduction of stimulated Raman scattering in optical fibers by orthogonal polarization pumping

We present experiments that show simultaneous achievement of suppression of modulational instability and substantial reduction of stimulated Raman scattering in birefringent optical fibers under dual-frequency, orthogonal polarization pumping. The suppression mechanism is based on careful control of the group-velocity match between the pumps and on an appropriate choice of the input power distribution among the components of the pump field. The use of orthogonally polarized pump beams permits suppression of the parametric and Raman Stokes beams in any one of the fiber axes, with a frequency spacing between the pumps (2.4 THz) that is reduced by more than 1 order of magnitude compared with the pump-frequency spacing required for a linearly polarized pump field (26 THz).

Direct polarization-heterodyne measurement of Kerr-induced birefringence in optical fibers

We have directly measured the amount of birefringence induced by nonlinear Kerr effect in standard optical fibers, by means of a double-polarization-heterodyne method, suitable for characterizing short samples of fibers. Birefringence is measured with a resolution of /spl Delta/n/spl ap/10/sup -12/ and the optical Kerr coefficient is extracted. The agreement of experimental results and theoretical predictions confirms the accuracy of the technique.

Polarization dynamics of solitons in birefringent fibers

We study the dynamics of uniformly polarized pulses in a birefringent optical fiber. By considering the Hamiltonian structure, symmetries, and the momentum map of the underlying equations, we obtain a self-consistent set of equations for the polarization state alone. In the autonomous case, we find the bifurcation curve of this system, and discuss how the orbits change in the neighborhood of this curve. We calculate the orbits explicitly. An extension to nonautonomous underlying equations is also possible. We further briefly discuss the effect of radiation emission from solitons as their polarization state changes.

Polarization-multiplexed and phase-stepped fibre optic shearography usinglaser wavelength modulation

A shearography system that measures the deformation gradient usingtwo orthogonal shear directions and performs phase stepping, using no movingmechanical components and a single CCD camera, is described. The light exitingfrom a highly linearly birefringent optical fibre is switched between twoorthogonal linearly polarized states by tuning the optical wavelength of alaser diode via injection current modulation. A polarization sensitiveMichelson interferometer is used to shear the image in orthogonal directionsfor p- and s-polarized light. The change in the optical wavelength is alsoused to provide a phase step in the pathlength imbalanced interferometer. Inthis way wavelength modulation of a laser diode source is used to accomplishsimultaneously polarization multiplexing and phase stepping in the shearinginterferometer. By carefully matching the optical wavelength shift, theoptical fibre length and the pathlength imbalance in the interferometer, theπ/2 polarization shift can be matched to the required phase step.

Shape-changing collisions of coupled bright solitons in birefringent optical fibers

We critically review the recent progress in understanding soliton propagation in birefringent optical fibers. By constructing the most general bright two-soliton solution of the integrable coupled nonlinear Schrödinger equation (Manakov model) we point out that solitons in birefringent fibers can in general change their shape after interaction due to a change in the intensity distribution among the modes even though the total energy is conserved. However, the standard shape-preserving collision (elastic collision) property of the (1 + 1)-dimensional solitons is recovered when restrictions are imposed on some of the soliton parameters. As a consequence the following further properties can be deduced using this shape-changing collision. 1. (i) The exciting possibility of switching of solitons between orthogonally polarized modes of the birefringent fiber exists. 2. (ii) When additional effects due to periodic rotation of birefringence axes are considered, the shape changing collision can be used as a switch to suppress or to enhance the periodic intensity exchange between the orthogonally polarized modes. 3. (iii) For ultra short optical soliton pulse propagation in non-Kerr media, from the governing equation an integrable system of coupled nonlinear Schrödinger equation with cubic-quintic terms is identified. It admits a nonlocal Poisson bracket structure. 4. (iv) If we take into account the higher-order terms in the coupled nonlinear Schrödinger equation then their effect on the shape changing collision of solitons, during optical pulse propagation, can be studied by using a direct perturbational approach.

Dispersion-managed solitons in a periodically and randomly inhomogeneous birefringent optical fiber

The propagation of dispersion-managed vector solitons in optical fibers with periodic and random birefringence is studied. With the help of a variational approach, the equations that describe the evolution of pulse parameters are derived. Numerical modeling is performed for variational equations and for fully coupled periodic and stochastic nonlinear Schrodinger equations. It is shown that variational equations can be effectively used to describe the averaged dynamics of dispersion-managed vector solitons with stochastic perturbations. It is shown, analytically and numerically, that dispersion-managed (DM) solitons have the same resistance to random birefringence as do ordinary solitons. The dependence of the mean decay length of a DM vector soliton on the strength of random birefringence and on the energy of the initial pulse is found.

Measurement of nonlinear polarization rotation in a highly birefringent optical fibre using a Faraday mirror

We present both a theoretical and experimental analysis of nonlinear polarization rotation in an optical fibre. Starting from the coupled nonlinear Schrodinger equations an analytical solution for the evolution of the state of polarization, valid for fibres with large linear birefringence and quasi cw input light with arbitrary polarization, is given. It allows us to model straightforwardly go-and-return paths as in interferometers with standard or Faraday mirrors. In the experiment all the fluctuations in the linear birefringence, including temperature- and pressure-induced ones, are successfully removed in a passive way by using a double pass of the fibre under test with a Faraday mirror at the end of the fibre. This allows us to use long fibres and relatively low input powers. The match between the experimental data and our model is excellent, except at higher intensities where deviations due to modulation instability start to appear.

Polarization-dependent loss-induced pulse narrowing in birefringent optical fiber with finite differential group delay

A combination of polarization-mode dispersion (PMD) and polarization-dependent losses in optical fiber may lead to anomalous pulse narrowing despite the existence of finite differential group delay. It raises the issue for more complete assessments when studying the pulse propagation in single-mode fiber (SMF) in the presence of polarization-dependent loss.