Birefringent Optical Fiber Research Articles

A novel ultrahigh birefringent hole-assistant microstructured optical fiber with low confinement loss

A novel hole-assistant microstructured optical fiber with a rectangle-like core and four elliptical holes as cladding is proposed. By employing a full-vector finite element method, the modal birefringence and confinement loss are numerically investigated, and the results show that in such a structure, an ultrahigh modal birefringence of 2.91×10 −2 and a low confinement loss (<1 dB/km) can be simultaneously obtained at excited wavelength of 1.55 μm. It is significant that such a microstructured optical fiber is easily fabricated with its simple structure and exhibits improved performance.

Stress and modal birefringence of single-mode specialty optical fibers with three-stress regions

Stress-induced birefringence and modal birefringence of single-mode specialty optical fibers with three stress regions are numerically analyzed by the vector finite element method. Stress distribution and stress-induced birefringence distribution of three kinds of optical fibers with different cross structures are presented and compared, and the influence on the stress-induced birefringence by temperature change are analyzed as well. The results show that the fibers with three-stress regions have a lower linear birefringence, which is very important for the fabrication of the circular polarization-maintaining fiber with high performance drawn from the same fiber preform by using the spinning method.

Evolution of first-order sidebands from multiple FWM processes in HiBi optical fibers

The generation of two idler waves inside a high birefringent (HiBi) optical fiber through three four-wave mixing (FWM) processes is studied theoretically. The coupled-equations for the field amplitudes are derived and analytically solved, in the co-polarized and orthogonal polarization schemes. The obtained solutions take into account the delayed Raman response of the medium. The polarization sensitivity of the generation of the idler waves is analyzed. Results show that the stimulated Raman scattering does not change the efficiency of the idler wave generation in the co-polarized scheme, whereas in the orthogonal polarization scheme that nonlinear process decreases the efficiency of the four-wave mixing processes. Results also show that this set of multiple four-wave mixing processes is physically quite different from the typical single or dual pump four-wave mixing configurations. Findings show that the power transfer from the pumps to the idler fields can lead to a monotonous growth, or a periodic evolution of the sidebands along the fiber. Results show that the process efficiency varies greatly with the angle between the two pump polarizations.

Technique and Apparatus for Accurate Cross-Sectional Stress Profiling of Optical Fibers

The design and performance of a technique for determining 2-D cross-sectional stress distributions in optical fibers and fiber-based devices is described. The Brace-Köhler phase compensation method is implemented on a commercial polarization microscope to perform full-field measurements of the transverse retardations induced by the low levels of birefringence in optical fibers. Analysis of the region surrounding the fiber enables removal of the background retardation induced by the imaging optics. A custom microscope stage plate, fiber rotation apparatus, and compensator rotation apparatus allow for semi-automated measurements at various angular orientations of the fiber. Image analysis techniques are described that reduce the number of angular increments over which the compensator must be rotated, thus providing a more workable total data acquisition time. Computed tomography principles and the filtered backprojection algorithm are implemented to determine full cross-sectional axial stress distributions. The lateral spatial resolution of the technique is 0.46 μm . The axial stress distribution in Corning SMF-28 fiber is presented. The resolution of the axial stress determined with the technique is estimated to be 0.24 MPa. The accuracy of the axial stress is estimated to be ±0.18 MPa.

Modal four-wave mixing supported generation of supercontinuum light from the infrared to the visible region in a birefringent multi-core microstructured optical fiber

We experimentally studied the process of supercontinuum generation in a birefringent multi-core microstructured optical fiber. By selecting the excitation of the fundamental mode, or by combining the first and the second order modes of a particular core, it was possible to emphasize the role of four-wave mixing on the transfer of power from the infrared to the visible region of the spectrum. We carried out an in-depth analysis of the effects of input light polarization on the generated supercontinuum spectral features. The measured polarization properties of the output Stokes and anti-Stokes bands confirmed the strong vector nature of the four-wave mixing processes. The experimental spectra exhibit excellent agreement with numerical simulations of the nonlinear mode interactions.

Polarized low-coherence interferometry applied to birefringent fiber characterization

We use a polarization-maintaining low-coherence interferometer to characterize birefringent optical fibers. We show how it is possible to determine the phase and group birefringence, the orientation of the two eigenaxes and the difference of chromatic dispersions along the eigenaxes, performing three measurements only.

PMD and DGD Performance Analysis in SMF due to Fiber Irregularities

A fundamental property of optical signal is polarization. Polarization refers to the electric field orientation of the light signal, which can vary significantly along the length of the fiber. Signal energy at a given wavelength occupies two orthogonal polarization modes .A varying birefringence along its length will cause each polarization mode to travel at significantly different velocity and polarization orientation is related with distance.The resulting difference in propagation time, DGD between two orthogonal polarizations will result in pulse splitting. PMD is related to the differential group delay, DGD caused by birefringence in optical fibers. Polarization mode dispersion, PMD is a phenomenon found in optical fiber and other wave guides .It is created by fiber irregularities and thus causes dispersion and distortion of the light pulse, thus increasing BER and limiting data rate. There are various types of irregularities in fiber, which arise due to an asymmetric fiber core or can be introduced through internal stresses during fiber manufacture, or through external stresses during cabling and installation. Optical fiber manufacturing processes are designed to yield fibers with a circular cross-section. Any deviation from this form will generally result in an elliptical core, which in turn will result in a refractive index difference between the X and Y-axes of the elliptical core. Even if the fiber core is manufactured with an ideal circular cross-section its refractive index can be asymmetric across its cross-section due to stresses built into the fiber during the manufacturing process or stress that is externally applied during deployment or operation. In the present paper, authors have analyzed PMD and DGD performance in the single mode fiber with different fiber irregularities.

Monitoring Method of Stray Current in Coal Mine on Optical Fiber Sensing Technique

In this work a novel monitoring method was developed to measure the underground stray current in coal mine with fiber current sensing technique. According to the theory of optical fiber current sensor based on Faraday magneto-optic effect, a fiber sensing system was designed and the relative experiments with current generator simulating stray current were completed. The results indicate that the measurement was influenced by birefringence and temperature change. The sensing heads with high cylindrical birefringence optical fiber had a good suppressing effect on linear birefringence and the polarization state of polarized light was also more stable than that with low birefringence optical fiber. The fiber current sensing method is doable in underground stray current monitoring system in coal mine.

Optimization of genetic algorithm for reconstruction of cross-phase modulation frequency-resolved optical gating data

We implemented a frequency-resolved optical gating (FROG) measurement method using cross-phase modulation in a highly birefringent microstructure optical fiber. The standard FROG data reconstruction algorithm of generalized projection failed for this setup and we successfully used the genetic algorithm (GA) instead which is less prone to get stuck to local minima. GA has several parameters that must be set up to suitable values. We describe the experimental setup and the algorithm and present our findings on what GA parameters are crucial and what are their optimal values. A single run of the algorithm takes 7 min on contemporary CPUs, making the algorithm suitable for routine laboratory work. Copyright © 2010 John Wiley & Sons, Ltd.

Joint-characteristic Function of the First- and Second-order Polarization-mode-dispersion Vectors in Linearly Birefringent Optical Fibers

This paper presents the joint characteristic function of the first- and second-order polarization-modedispersion (PMD) vectors in installed optical fibers that are almost linearly birefringent. The joint characteristic function is a Fourier transform of the joint probability density function of these PMD vectors. We regard the random fiber birefringence components as white Gaussian processes and use a Fokker-Planck method. In the limit of a large transmission distance, our joint characteristic function agrees with the previous joint characteristic function obtained for highly birefringent fibers. However, their differences can be noticeable for practical transmission distances.

Distributed characterization of bending effects on the birefringence of single-mode optical fibers

The effects of bending on randomly birefringent, single-mode optical fibers have been analyzed by means of polarization-sensitive optical frequency domain reflectometry. This distributed, pointwise characterization has been performed on ad hoc drawn spun fibers and on a ribbon cable. Experimental results are in agreement with the theoretical predictions and confirm the effectiveness of reflectometry as a means to characterize polarization properties of optical fibers.

Dark and anti-dark vector solitons of the coupled modified nonlinear Schrödinger equations from the birefringent optical fibers

Coupled modified nonlinear Schrodinger (CMNLS) equations describe the pulse propagation in the picosecond or femtosecond regime of the birefringent optical fibers. A new type of the Lax pair and another hierarchy of the infinitely many conservation laws are derived based on the Wadati-Konno-Ichikawa system. By means of the Hirota method, soliton solutions in the normal dispersion regime are obtained. Parametric regions for the existence of dark and anti-dark vector soliton solutions are given. Asymptotic analysis shows that the collision between two solitons (two anti-dark solitons, two dark solitons, or dark and anti-dark solitons) in each polarization direction is elastic. Moreover, there is no energy transfer between two polarization components of each vector soliton, whether dark or anti-dark vector soliton. In addition, dark and anti-dark solitons can coexist on the same background seen from the collision between the dark and anti-dark solitons in one polarization direction. Our graphical analysis shows that the parameters in the CMNLS equations not only determine the regions for the existence of dark and anti-dark soliton solutions but also control the phase and direction of the propagation of the solitons. Finally, through the linear stability analysis, the modulational instability condition is given.

Sidelobe suppression in all-fiber acousto-optic tunable filter using torsional acoustic wave

We propose two techniques to suppress intrinsic sidelobe spectra in all-fiber acousto-optic tunable filter using torsional acoustic wave. The techniques are based on either double-pass filter configuration or axial tailoring of mode coupling strength along an acousto-optic interaction region in a highly birefringent optical fiber. The sidelobe peak in the filter spectrum is experimentally suppressed from -8.3 dB to -16.4 dB by employing double-pass configuration. Axial modulation of acousto-optic coupling strength is proposed using axial variation of the fiber diameter, and the simulation results show that the maximum side peak of -9.3 dB can be reduced to -22.2dB. We also discuss the possibility of further spectral shaping of the filter based on the axial tailoring of acousto-optic coupling strength.

Sensitivity of Bragg gratings in birefringent optical fiber to transverse compression between conforming materials

A theoretical and experimental investigation of the transverse load sensitivity of Bragg gratings in birefringent fibers to conforming contact is presented. A plane elasticity model is used to predict the contact dimensions between a conforming material and optical fiber and the principal stresses, indicating birefringence, created as a result of this contact. The transverse load sensitivity of commercially available birefringent fiber is experimentally measured for two cases of conforming contact. Theoretical and experimental results show that birefringent optical fiber can be used to make modulus-independent measurements of contact load. Therefore, Bragg gratings could be applied to conforming contact load measurements while avoiding some of the complications associated with existing contact sensors: specifically, the necessity to precalibrate by using materials with mechanical properties identical to those found in situ.

Technology of high birefringent microstructured polymer optical fibers

Technology of high birefringent microstructured polymer optical fibers

Consideration of chiral optical fibres

Circular birefringence is a property of chiral materials. In this work, we consider the use of chiral materials in optical fibres to produce circularly birefringent optical fibres and in fibres where a contrast in circular birefringence contributes to forming the waveguide. (t϶-menthyl methacrylate is also investigated as a possible material for the fabrication of such fibres.

Drawing parameters optimization for birefringence reduction in optical fibers

The impact of the drawing process on the stress-induced birefringence in optical fiber is experimentally analyzed. By means of the photoelastic tomographic technique, residual internal stresses are measured in fiber samples drawn under different conditions of temperature, drawing tension and speed. From measured residual stress distributions, the stress-induced birefringence and beatlength are mathematically derived and compared, proving that an effective birefringence reduction can be obtained by a proper choice of drawing parameters.

Photon pair generation in birefringent optical fibers

We study both experimentally and theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in standard birefringent optical fibers. The ability to produce a range of two-photon spectral states, from highly correlated (entangled) to completely factorable, by means of cross-polarized birefringent phase matching, is explored. A simple model is developed to predict the spectral state of the photon pair which shows how this can be adjusted by choosing the appropriate pump bandwidth, fiber length and birefringence. Spontaneous Raman scattering is modeled to determine the tradeoff between SFWM and background Raman noise, and the predicted results are shown to agree with experimental data.

Soliton interaction in the coupled mixed derivative nonlinear Schrödinger equations

The bright one- and two-soliton solutions of the coupled mixed derivative nonlinear Schrödinger equations in birefringent optical fibers are obtained by using the Hirota's bilinear method. The investigation on the collision dynamics of the bright vector solitons shows that there exists complete or partial energy switching in this coupled model. Such parametric energy exchanges can be effectively controlled and quantificationally measured by analyzing the collision dynamics of the bright vector solitons. The influence of two types of nonlinear coefficient parameters on the energy of each vector soliton, is also discussed. Based on the significant energy transfer between the two components of each vector soliton, it is feasible to exploit the future applications in the design of logical gates, fiber directional couplers and quantum information processors.

Experimental evidence of Brillouin-induced polarization wheeling in highly birefringent optical fibers

We study the influence of Stimulated Brillouin Scattering on the polarization stabilization of a light beam propagating in a highly-birefringent optical fiber. In particular, due to a saturation effect, we find that the output polarization lies on a ring when the polarization is represented onto the Poincaré sphere.