Vladimir A. Andreev

Radiophotonic method for instantaneous frequency measurement based on principles of “frequency-amplitude” conversion in Fiber Bragg grating and additional frequency separation

This article describes the design principles of optoelectronic system (OES) for instantaneous frequency measurement (IFM) of microwave signals based on the use of amplitude-phase modulation conversion of single optical carrier into symmetrical dual-frequency signal for additional frequency separation, its modulation by unknown frequency and subsequent “frequency-amplitude” measurement conversion in Fiber Bragg Grating (FBG) with Gaussian reflection profile. Such approach allows increasing of measurement resolution at low frequencies.

Investigation of cross-phase modulation in multichannel dispersion managed soliton systems

In this paper cross-phase modulation in mutichannel dispersion managed soliton systems was investigated. Method for evolution of main optical soliton parameters for two-channel WDM systems based on variatonal approach was proposed. Results of soliton propagation simulation in communication lines with different dispersion maps are represented and comparison with numerical method was carried out.

Analysis of spectral characteristics of Rayleigh scattering parameters for different types of single-mode fibers

In this paper the spectral characteristics of Rayleigh scattering parameters were considered for different types of single-mode fibers. Making use of Gauss approximation mode field, I have proposed analytical equations for scattering parameters. Using these equations spectral characteristics of scattering parameters are calculated for the most used types of single-mode fibers. Results of calculations were compared and analyzed.

Results of differential mode delay map measurements performed for multimode optical fibers with strong and weak diameter variation

We present results of experimental research and comparison of differential mode delay (DMD) maps measured for silica graded index multimode optical fibers (MMFs) with strong and weak diameter variation. Preliminary for two synthesized by MCVD fiber preforms were selected by criterion of expected strong DMD due to great profile dip in the core center. Then two lengths of MFMs were drawn. The first one was manufactured according typical operations with automatic control of technological processes, while the second one was drawn under manual maintenance. Therefore two samples of MMFs of ISO/IEC Cat. OM2 with length about 1 km were manufactured with diameter variation ± 0.3 μm and ± 1.2 μm respectively. At the next stage we performed DMD map measurement of described two MMF 50/125 samples by DMD analyzer lab kit R2D2 according to ratified standards TIA-455-220-A/FOTP-220 and IEC 60793-2-10 to research and analyze influence of fiber diameter variation on mode coupling in the form of additional DMD distortions during laser-excited optical pulse propagation over MMF under a few-mode regime.

Results and analysis of survey conducted among professional fiber optic technicians and engineers concerned with skills in fiber optic link testing and measurement

In work results of the survey conducted among professional fiber optic technicians and engineers concerned with skills in fiber optic link testing and measurement are presented. Head count was provided on the basis of the Samara Regional Telecommunication Training Centre (SRTTC) of the Povolzhskiy State University of Telecommunications and Informatics (PSUTI) during the period from February to April, 2017. The developed survey included a set of the questions allowing to estimate an work length and qualification of the engineer, his practical skills, the main activity field, typical work volume on measurements and results processing and, respectively, obligatory and optional actions for grouping, marking, structuring and hosting of the database on this or that trace of the elementary cable section of fiber optic transmission links. More than 40 employees of communication industry, business units of the big companies and also the separate enterprises of medium and small business carry on installation and maintenance of fiber optic transmission links have participated in survey. At the same time part of them have been defective, proceeding from the revealed unacceptably low skill level and/or short work length. The analysis of the received survey results have allowed to establish the corresponding subsections of course programs in the Measurements on Fiber Optic Transmission Links demanding, at least, enhanced studying, and in some cases – modifications and carrying out an additional lecture practical training.

Impact of mode coupling effects on few-mode optical fiber communication line performance

In this paper, the signal propagation is described by a generalized nonlinear Schrodinger equation take into account linear and nonlinear mode coupling. A modified solution based on split-step Fourier method is considered. The method for simulation of mode coupling coefficients based on statistical characteristics is proposed. Results of bit error rate estimations for space division multiplexing signal propagation in few mode fiber communication line for weak and strong coupling regime are represented.

Research of the local communication combined cable on resistance to mechanical stress

Communication cables in general and combined in particular, applied on objects of technological communication of gas, oil, processing industry and also on objects of other industries should have high reliability and resistance to mechanical loadings. This work the resistance of optical fibers and copper conductors of the combined cable to influence of the tensile and crushing loadings and also stiffness of a cable which arise at their installation is considered.

Design of low DMD few-mode optical fibers with extremely enlarged core diameter providing nonlinearity suppression for operating over “C”-band central region

We present method for design of refractive index profile for silica GeO2-doped graded-index few-mode optical fibers with reduced differential mode delay and suppressed mode nonlinearity due to extremely enlarged core diameter up to 42 μm. Proposed solution is based on earlier on developed modified Gaussian approximation generalized for analysis of silica weakly guiding optical fibers with single outer cladding and arbitrary axially-symmetric refractive index profile, that provides ability to derive analytical expressions for guided mode delays. Therefore the objective function is represented as a sum of squares of deviations between mode staff delays and reference value corresponding to refractive index profile of current iteration. Based on developed method we performed computation for various combination of the reference mode delay and first iteration profile parameter. Some results of desired graded-index profile for a few-mode optical fibers 42/125 providing differential mode delay minimization over central region of C-band are represented.

Quasi-interferometric scheme improved by fiber Bragg grating written on macrostructure defect in silica multimode optical fiber operating in a few-mode regime

This work presents results of experimental approbation of earlier on proposed modified fiber optic stress sensor based on a few-mode effects occurring during laser-excited optical signal propagation over silica multimode optical fiber (MMF). Modification is concerned with a passage to quasi-interferometric scheme realized by two multimode Y-couplers with equalized arm lengths improved by fiber Bragg grating (FBG) written on preliminary formed precision macrostructure defects in silica multimode graded-index optical fibers and special offset launching conditions providing laser-based excitation of higher-order modes. The “arms” of quasi-interferometer are two equalized lengths of MMF Cat. OM2 with great central dip of refractive index profile and strong pulse splitting due to high differential mode delay (DMD). We tested FBGs with Bragg wavelength both 1310 nm and 1550 nm written over tapers or up-tapers preliminary formed in short pieces of MMF Cat. OM2+/OM3 and further jointed to the end of one of the arms before output Y-coupler. Researches were focused on comparison analysis of pulse responses under changing of selected excited mode mixing and power diffusion processes due to stress distributed action to sensor fiber depending. Here we considered FBGs not only as particular wavelength reflector during spectral response measurement but also as local periodic microstructure defect which strongly effects on few-mode signal components mixing process also improved by combination with macro-defect like taper or up-taper that should provide response variation. Some results pulse response measurements produced for different scheme configuration and their comparison analysis are represented.

Technique for writing of fiber Bragg gratings over or near preliminary formed macro-structure defects in silica optical fibers

This work presents method for performing precision macro-structure defects “tapers” and “up-tapers” written in conventional silica telecommunication multimode optical fibers by commercially available field fusion splicer with modified software settings and following writing fiber Bragg gratings over or near them. We developed technique for macrodefect geometry parameters estimation via analysis of photo-image performed after defect writing and displayed on fusion splicer screen. Some research results of defect geometry dependence on fusion current and fusion time values re-set in splicer program are represented that provided ability to choose their “the best” combination. Also experimental statistical researches concerned with “taper” and “up-taper” diameter stability as well as their insertion loss values during their writing under fixed corrected splicer program parameters were performed. We developed technique for FBG writing over or near macro-structure defect. Some results of spectral response measurements produced for short-length samples of multimode optical fiber with fiber Bragg gratings written over and near macro-defects prepared by using proposed technique are presented.