Single-mode Fiber Lightguides Research Articles

Influence of the Polarization Mode Dispersion on Propagation of Ultrashort Optical Pulses in the Spun Light Guides with Very Weak Linear Birefringence and Random Inhomogeneities

Although the spun light guides were developed in early 1980s, their quantity production has started only a few years ago. At present, the spun light guides with both strong and weak natural (unperturbed) linear birefringence are produced. The former are used for creating sensors of various physical parameters, mainly, current and magnetic field. The latter are very promising for use in fiber communication lines, since they have a considerable advantage over the conventional telecommunication light guides. In this work, we consider the influence of the polarization mode dispersion due to random inhomogeneities in the single-mode fiber light guides (SMFLGs) on propagation of ultrashort optical pulses in the fiber communication lines, which are based on the SMFLGs with very weak linear birefringence and strong regular twisting (such SMFLGs are called telecommunication spun light guides). The dependences of evolution of the envelope function of the ultrashort optical pulses and their spectra on the length of a spun light guide with very weak linear birefringence and random inhomogeneities are obtained by the numerical-simulation method. It is shown that an increase in the pulse width is proportional to the SMFLG length rather than occurs as per the diffuse law, as it is the case in the absence of torsion. It is established that the pulse widening to a certain (rather long) length with increasing length of the spun light guide occurs much slower than that in the untwisted light guides and faster for very long lengths. It is also shown that the relative intensity of radiation which is pumped from one orthogonal polarization mode to another over the depolarization length of nonmonochromatic radiation in the telecommunication spun light guides is small compared with unity, whereas an opposite situation is observed in the conventional telecommunication light guides.

Radiation-optical stability of single-mode W-type lightguides with depressed-index fluorosilicate cladding

This paper discusses how hydrogen-isotope doping of a single-mode W-type fiber lightguide with fluorosilicate cladding affects its additional optical losses under bending of the fiber and γ irradiation. It is established that introducing stable OH− and OD− groups into the core of a lightguide fabricated by modified chemical vapor deposition reduces its optical losses when it is bent but does not increase the radiation–optical stability.

Anisotropic single-mode lightguide with an elliptical germanium silicate core and depressed cladding

The properties of anisotropic single-mode fiber lightguides with an elliptical highly doped germanium core and elliptical fluorine-doped cladding have been investigated. When the difference of the refractive indices of the core and the cladding equals 0.033 and the ratio of the axes of the core is about 2, the birefringence is about 0.00037. The fabricated lightguides, despite the differential optical losses of the orthogonal modes to radiation leakage, are distinguished by a low level of polarization stability. The degree to which the radiation remains polarized in them (≈0.003 m−1) is two orders of magnitude worse than in commercially produced lightguides. This is probably caused by local microstrain of the low-viscosity glass of the core.

Increasing the birefringence in anisotropic single-mode fiber lightguides with an elliptical stress cladding

This paper discusses how the design features of anisotropic single-mode quartz fiber lightguides with an elliptical boron-germanosilicate stress cladding affect the birefringence. It is found that, as the ellipticity of the stress cladding and the drawing temperature increase, the contribution of the hydrostatic mechanism to the anisotropy of the stressed state of the core increases.

Amplitude modulation of guided radiation in single-mode fiber lightguides with a low normalized frequency due to seismic signals

The features of the amplitude modulation of guided radiation in single-mode fiber lightguides with a low normalized frequency when acted upon by seismic signals are investigated. It is shown that the sensitivity of sections of such lightguides to seismic shocks can reach 6·10–4 g. This makes it possible to use them to construct fiber-optical measuring transducers, whose metrological characteristics enable them to be used to solve a wide range of geophysics problems.

Influence of the polarization mode dispersion on the propagation of ultrashort optical pulses in single-mode fiber lightguides with very weak linear birefringence and random inhomogeneities

We consider the influence of the polarization mode dispersion, which is stipulated by the presence of random inhomogeneities in single-mode fiber lightguides, on the propagation of ultrashort optical pulses in the fiber communication lines with very weak linear birefringence. Evolution of the envelope of ultrashort optical pulses and their spectra as functions of the length of a single-mode fiber lightguide with very weak linear birefringence and random inhomogeneities are obtained by the method of mathematical simulation. An increase in the pulse duration is shown to be proportional to the square root of the length of a single-mode fiber lightguide. The numerical-simulation results are compared with the results of experimental measurements of the polarization mode dispersion.

Spectral analysis of the temperature dependence of the nonreciprocal phase difference of counterpropagating waves in a fiber ring interferometer

Using the method of the Fourier analysis, we obtain spectral-density distributions of the dependence of the nonreciprocal phase difference of counterpropagating waves at the output of a fiber ring interferometer on the temperature of a single-mode fiber lightguide of the interferometer circuit. It is shown that the main role in measuring the nonreciprocal phase difference is played by the temperature variation in the difference of the optical-path in slow and fast birefringence axes of the single-mode fiber lightguide between the circuit ends and random irregularities.

Processing large blanks of anisotropic single-mode lightguides with elliptical cladding

This paper discusses the possibility of increasing the diameter of blanks for drawing anisotropic single-mode quartz fiber lightguides by fusing the preblank with a tube, the gap between which, is filled with quartz grits. It is shown that the polarization stability of such lightguides increases as the diameter of the light-fiber increases.

Geometric phases in singlemode fiber lightguides and fiber ring interferometers

We consider various geometric phases (GPs) in singlemode fiber lightguides (SMFs) and in fiber ring interferometers (FRIs): the Pancharatnam phase stemming from the cyclic evolution of the polarization state of radiation (RP state) in SMF, the Rytov–Vladimirskii phase (RV phase) stemming from the Rytov effect (specifically, rotation of the polarization plane due to noncoplanar winding of SMFs), as well as the nonreciprocal phase difference of counterpropagating waves (NPDCW) and nonreciprocal geometric phase of counterpropagating waves (NGPCW), which are caused by polarization nonreciprocity (PN) in FRIs. We show that in the general case, the Pancharatnam phase for an arbitrary RP state is inconsistent with the real phase change of light fluctuations in mediathat possess not only circular but also linear birefringence. We show that the RV phase, having a geometric origin, can in principle be considered as a dynamic phase (DP). We also show that the NGPCW can be considered as an effect of the evolution of the RP state mapped on the Poincaré sphere in Ginzburg's orthogonal screw polarization modes (GSPMs) of SMFs in the FRI contour. We analyze a number of experiments in which geometric phases were detected in FRIs: changing the RV phase and Rytov's angle (RA) in response to change of the pitch of helicoidal winding of SMFs.

Decreasing Input Losses of Laser Radiation in Single-Mode Fiber Light Guides

It is shown that use of an anisotropic fiber-optic insert for increasing the efficiency of the connection of an injection laser to a single-mode optical fiber is promising.

MCVD technology for single-mode low-damping fiber lightguides stable against microbends

MCVD technology for single-mode low-damping fiber lightguides stable against microbends

How random twists of a single-mode fiber lightguide affect the sensitivity of fiber gyroscopes to an external magnetic field

How random twists of a single-mode fiber lightguide affect the sensitivity of fiber gyroscopes to an external magnetic field

Random Groups in the Optical Waveguides Theory

We propose a new approach to the mathematical description of light propagation in a single-mode fiber light-guide (SMFLG) with random inhomogeneities. We investigate statistics of complex amplitudes of the electric field of light wave by methods of the random group theory. We have analyzed the behavior of the coherence matrix of a monochromatic light wave and the polarization degree of a nonmonochromatic radiation in SMFLG with random inhomogeneities as the length of the fiber tends to infinity; in particular, we prove that limit polarization degree is equal to zero.

Nonholonomic relation between the electromagnetic field state and the torsion angle in a single-mode lightguide with linear birefringence

The relation between the electromagnetic field state and the torsion angle in a twisted single-mode fiber lightguide (SFL) with linear birefringence is considered for the case where the lightguide is stretched into a straight line. It is shown that this relation is nonholonomic, because of the noncommutativity of two infinitesimal but different changes in the length and torsion of the lightguide. This indicates that the relation between the radiation polarization and the torsion angle in a twisted lightguide is also nonholonomic, and so is the relation between the Pancharatnam geometric-optics phase increment due to the evolution of the light polarization state in an anisotropic optical medium and the SFL torsion angle.

Effect of orthogonal-mode random coupling on polarization characteristics of single-mode fiber lightguides (SMFL) and SMFL-based ring interferometers. Part III. Zero drift in ring interferometers with nonmonochromatic-radiation depolarizers

A method is proposed for calculation of the zero drift and Fedding interference signal at the output of a fiber ring interferometer (FRI) based on a single-mode fiber lightguide (SMFL) with a nonmonochromatic radiation source. The fiber length is divided into sections that are equal to the depolarization length in the SMFL. It is shown that when the FRI is made of an anisotropic SMFL with weak orthogonal-mode coupling, the calculation results agree with those obtained earlier by other calculation methods. Results for an FRI made of a weakly anisotropic SMFL with strong orthogonal-mode coupling are obtained for the first time.

Effect of orthogonal-mode random coupling on polarization characteristics of single-mode fiber lightguides (SMFL) and SMFL-based ring interferometers Part II. Zero drift in fiber ring interferometers with nonmonochromatic radiation sources

Effect of orthogonal-mode random coupling on polarization characteristics of single-mode fiber lightguides (SMFL) and SMFL-based ring interferometers Part II. Zero drift in fiber ring interferometers with nonmonochromatic radiation sources

Methods for measurement of random coupling of polarized modes in weakly anisotropic single-mode fiber lightguides

Three methods for measurement of the h parameter in single-mode fiber lightguides (SFG) with different degrees of anisotropy are compared experimentally. It is shown that all three methods provide a practically identical result for an SFG with strong anisotropy, while only the method based on excitation of the SFG input by nonmonochromatic radiation of a single polarization mode has an adequate result, provided that the spectral width of the radiation source is comparable with its wavelength.

Analysis of directivity pattern of a multielement phased laser emitter with injection lasers and single-mode fiber lightguides

Analysis of directivity pattern of a multielement phased laser emitter with injection lasers and single-mode fiber lightguides