Ruslan V. Kutluyarov

Nonlinear impairments in mode division multiplexed systems

In this paper we consider nonlinear impairments of mode division multiplexed signals with QAM modulation in optical fibers with linear mode coupling of spatial modes. We simulate simultaneous propagation of fundamental mode and two first-order vortex modes in standard single mode fiber at 850 nm and propagation of fundamental mode and first- and second-order vortices in step-index fiber with enlarged core at 1550 nm. Simulation results shows that in strong coupling regime linear coupling lead to sufficient increasing of nonlinear impairments, but QAM-modulated signal is more robust to this effect than OOK modulated signal.

Optical device models for RoF systems

This paper studies engineering design and modeling of an optical device intended for Radio-over-Fiber (RoF) antenna array radio emitting management. Design and assembled models of the device are based on either profiled multiple-wave interferometer or long-haul ring topology FOCL. To construct the interferential type OSCD (optical signal splitting and chirping device) models optical ceramic glass mixer processed with the ITHP (intense twist under high pressure) method was used. Loss and transmission coefficients with account of splitting for all the prototype units were measured — on frame-controller equipment and on RoF segment test bench equipment. Satisfactory measurement results obtained allow to make conclusion on OSCD models applicability for RoF test segments. The designed models and test bench pictures are also illustrated in this article.

Increase of nonlinear signal distortions due to linear mode coupling in space division multiplexed systems

This paper is focused on the analysis of linear and nonlinear mode coupling in space division multiplexed (SDM) optical communications over step-index fiber in few-mode regime. Linear mode coupling is caused by the fiber imperfections, while the nonlinear coupling is caused by the Kerr-nonlinearities. Therefore, we use the system of generalized coupled nonlinear Schrödinger equations (GCNLSE) to describe the signal propagation. We analytically show that the presence of linear mode coupling may cause increasing of the nonlinear signal distortions. For the detailed study we solve GCNLSE numerically for the standard step index fiber at the wavelength of 850 nm in the basis of spatial modes with helical phase front (vortex modes) and for a special kind of few-mode fiber with enlarged core, providing propagation of five spatial modes at 1550 nm. Simulation results confirm that the linear mode coupling may lead to a significant increase of the nonlinear distortions. It is necessary to take this phenomenon into account in SDM systems with linear compensation of mode coupling, because the nonlinear distortions may sufficiently decrease the effectiveness of the compensation.

Analysis of optical fiber complex propagation matrix on the basis of vortex modes

We propose and experimentally demonstrate a novel method for reconstruction of the complex propagation matrix of optical fibers supporting propagation of multiple vortex modes. This method is based on the azimuthal decomposition approach and allows the complex matrix elements to be determined by direct calculations. We apply the proposed method to demonstrate the feasibility of optical compensation for coupling between vortex modes in optical fiber.

Approach for producing the nanocrystalline sitall samples with distributed refractive index

We have explored a novel technique for producing transparent volumetric nanocrystalline sitall by means of intensive plastic deformation. This material is intended to be used for components of fiber optic devices, including various applications in all-optical networks. We have examined properties of the material experimentally and by means of the proposed analytical model.

Signal improvement due to interaction of PMD and Kerr-nonlinearities in WDM system

We considered interaction of PMD and Kerr-nonlinearities in the two-channel WDM system to derive conditions of signal improvement due to such interaction. We presented statistics of eye-diagram opening and investigated properties of fiber links providing this kind of signal improvement.

Interaction of PMD and Kerr-nonlinearities and its impact on WDM-signal transmission

This paper presents results of investigation on interaction of PMD and Kerr-nonlinearities in long-haul fiber links. It is shown that PMD may significantly reduce impairments caused by nonlinear effects. There are shown dependences on the input polarization, peak pulse power, PMD coefficient and used line codes.

WDM signal impairments due to the cross-modulation in the case of nonlinear transmission in the presence of PMD

This paper presents results of investigation on cross-phase modulation effect and influence of polarization effects on it. It is shown that fast polarization scrambling can effectively reduce impairments caused by cross-phase modulation in the case of NRZ signal.

Simulation of pulse propagation in fiber link with nonlinearities and PMD

This paper presents results of numerically solved model of fiber link including Kerr-nonlinearities, dispersive effects and polarization-mode dispersion. Different types of Gaussian pulses are modeled at step-index and non-zero dispersion shifted fibers.

Synthesis of reflective optical multilayer filters

We present a solution of the synthesis for reflective optical filters designed for WDM-systems. Filter is based on multilayer dielectric structures with apodized (modulated) refractive index profile. The method of synthesis provides calculation of the uniform quarter-wave filter-prototype. The calculation of the prototype is executed with relation, which join given spectrum characteristics with constructive parameters of the filter. On the base of calculated filterprototype the filter with bilateral Gaussian apodization of a refractive index profile, possessing given spectral properties is formed.