This work presents results of test series, performed for earlier on designed and successfully fabricated silica few-mode microstructured optical fibers (MOF) with six GeO2-doped cores, induced twisting 100 revolutions per meter, typical “telecommunication” outer diameter 125 μm, core diameter 8.7 μm, air hole diameter 4.6 μm, pitch 7.2 μm, and core quasi-step / graded refractive index profiles with height 0.0360/0.0275, respectively. Part I introduces attempts for splicing of typical telecommunication optical fibers and fabricated samples of MOFs by commercially available field arc fusion splicer kits and results of differential mode delay map measurements, performed for laser excited large core (multimode) optical fibers with core diameters 50 and 100 μm, jointed via free space to described above 2 m long pilot samples of 6-GeO2-core MOFs at both receiving and transmitting ends under laser-excited gaussian optical pulse launching with precision offset conditions, while Part II is concerned with researches of spectral responses, measured for fiber Bragg gratings, recorded in these MOFs.
This work presents some results of pulse and spectral responses, performed for laser-excited pilot sample of earlier on designed and fabricated chiral silica few-mode optical fiber (FMF) with induced twisting 66 revolutions per meter (rpm), typical (for telecommunication optical fibers) cladding diameter 125 μm, weakly increased core diameter up to 11 μm and numerical aperture NA=0.22, corresponding to improved height of quasi-step refractive index profile. Described FMF 11/125 provides propagation of 4 and 6 guided modes over “C” and “O”-bands, respectively. We present results of tests, focused on researches of few-mode effects, occurring under laser-excited optical signal propagation over pilot sample optical fiber, and their influence on pulse and spectral responses, including some measurements, performed for fiber Bragg grating, recorded in tested FMF 11/125.
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.
We present modified technique for differential mode delay map measurement. Here according to well-known methods a fast laser pulse is also launched into a tested multimode fiber (MMF) via single mode fiber (SMF), which scans core of MMF under precision offset positions. However unlike known technique formalized in ratified standards, proposed modification differs by addition scanning of the output end of tested MMF by short tail of SMF. Therefore for each radial offset position at the input/output MMF ends, the shape of pulse response of launched optical signal is recorded, that provides to get more informative differential mode delay map. This work presents some results of experimental approbation of proposed modified technique for differential mode delay map measurement.
Results of investigations of optical fiber curvature distributions along loose-tube optical cable are discussed here. These
distributions are obtained from measurements by using OTDR on optical cable delivery length. The statistical characteristics
of these distributions are presented.
The investigation of polarization reflectometry sensitivity to detection and localization of new events in fiber optical lines is carried out. The results of numerical simulation and experimental measurements are represented. The estimation of localization accuracy for different events depending on polarization characteristic is represented. The algorithm of data processing and method for measurement using polarization controller are represented.
In this article mathematical models for estimation calculation of birefringence components for step-index optical fiber with a microcrack on the waveguide cladding are considered. Dependences of geometrical and mechanical birefringence components and beat length on the geometrical microcrack size are received. Results of calculation indicate potential possibility of detection of local defects on the waveguide cladding.
This paper is concerned with the applications of polarization reflectometry for identification and localization of defects
of various types in the fiber optical lines. The methods of physical simulations of various defects in optical fibers are
described. The methods and algorithms for polarization optical time domain reflectometer (POTDR) data processing are
represented. The results of laboratory and field tests are represented.
Polarization mode dispersion (PMD), at present, is one of the most meaningful effects, limiting bit rates in both TDMand
WDM-systems, and non-regeneration distance. PMD influence becomes significant for signal quality at bit rates of
more than 10 Gbit/s per channel.
PMD compensators development is in progress now all over the world with using different models, methods and
technologies.
We offer PMD compensation model based on the combination Faraday rotation of optical radiation and LiNbO3-based
differential group delay emulator. Such way presents applied interest because of simplicity of its body of mathematics.
Physical simulation of optical fiber cladding defects and experimental investigation results are described in present
paper. By these results it is confirmed that assumption about fiber light-guide cladding defects localization on short
length of optical fiber by comparison polarization backscattering characteristic with sliding correlation test is correct.
Samples of defects localization on less then 2 km optical fiber with less then 100 m error are represented.
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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