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.
In this paper is described an approximate analytical solution for the fundamental mode of the step-index optical fiber with taking into account the Kerr nonlinearity. The solution is obtained by a known method of Gauss approximation. Based on the obtained analytical solution there were calculated the spectral dependencies of time delay and first and second order chromatic dispersion the parameters for mode LP01 of the sample of the step-index optical fiber.
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.
In this article experimental investigation of differential mode delay (DMD) of regular multimode fiber links is presented.
Measurement of DMD depending on input conditions for multimode fiber of different generation are executed. The
measurement technique is described. Analysis of received data is carried out.
Approximate analytic solutions for special cases of optical refractive index profile are proposed. Results of mode
parameter estimation by introduced expressions under special refractive index profiles are presented.
This paper presents algorithm of reconstruction of equivalent refractive index profile of optical fiber by differential mode
delay diagrams. Calculations were performed for profile example of the sample multimode optical fibers.
In this article present results of measurements for refractive index profile of silica graded multimode optical fibers are
presented. The measurement technique is described. Estimation of parameters for profile defects of investigated
samples of multimode optical fibers is received. Analysis data for effect of profile defects of graded multimode optical
fibers (MMF) on differential mode delay (DMD) is presented.
Signal power redistribution between a few modes in a conventional multimode optical fiber have been simulated under
laser excitation with central and offset launch conditions through the special singlemode optical fiber been installed
between pigtailed laser and multimode fiber (MMF).
Chromatic dispersion characteristics of dispersion compensating fibers with arbitrary shapes and index profiles are
calculated by using a finite element method. A vector finite element method with mixed interpolation type triangular
elements implemented. The approach uses optimized way of global sparse system assembling which is considerably
reduces calculation time. Different types of mesh formation examined for better resolve of the dielectric interface
boundaries. Features of the algorithm are demonstrated by examples of calculation for microstructured fibers. The
correctness of assessments confirmed by comparison with those of known solutions and experimental data.
Errors of optical fiber chromatic dispersion calculation caused by line approximation of silica glass refraction index as a
function of dopant concentration are investigated. Calculation of chromatic dispersion for fibers with refractive index
profiles, for which experimental data of chromatic dispersion are known, is performed by an investigated method. Errors
of chromatic dispersion calculation are estimated by deviation evaluated results from data of measuring for samples of
optical fiber. On the basis of the comparative analysis the estimation of adequacy of the cosidered method is given.
A device for conversion of single frequency signal into two-frequency signal, based on lithium niobate dual-drive Mach-Zehnder modulator was proposed. The output spectrum was obtained analytically the proved numerically. The conditions
for two-frequency signal generation were described.
We present results of attempts to apply a conventional fiber parameter field-test equipment for identification of
multimode fibers with high differential mode delay (DMD). Backscattering traces, obtained by optical time domain
reflectometer (OTDR) with the single-mode optical unit, and refractive index profile form, reproduced by image
processing of lighted fiber end-face, were compared with pulse forms, registered by introduced DMD measurement
system. Silica graded-index multimode fibers 50/125 of different generations were considered. Comparing results of high
DMD fiber identification by OTDR, video diagnostics system and DMD measurement system are represented.
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