This work reports results of laser beam profile measurements, performed for earlier on designed and successfully fabricated silica few-mode microstructured optical fiber (MOF) with hollow-GeO2-doped-ring core (HRC). We compared two drawn from the same preform HRC MOF samples without and with induced during the drawing process twisting of 790 revolutions per meter. Researched silica HRC MOF with outer diameter 65 µm contains hollow ring-core inner diameter of 30.5 µm with wall thickness of 1.7 µm and refractive index difference Δn = 0.03; 90 air holes, placed over typical hexagonal geometry in the periphery domain from the outside HRC at the distance 14 µm, with hole averaged diameter 2.5 µm and pitch 7.5 µm. According to simulation results (mode analysis, performed by rigorous finite element method via commercially available software COMSOL Multiphysics®), it supports two guided LP-modes (fundamental LP01 and the first higher-order LP11) or 4 HE/EH odd and even eigenmodes – HE11/EH11 and HE21/EH21, respectively. We present some results of laser beam profile measurements, performed under various launching conditions (different laser sources as well as excited optical fibers (both commercially available single-mode optical fiber of ITU-T Rec. G.652 and multimode optical fiber 50/125 of ISO/IEC Cat. OM2+/OM3)) at the output ends of researched HRC MOF twisted and untwisted samples as well as at the output end of large core multimode optical fiber 100/125, aligned with excited HRC MOF.
The article presents the method for predicting the lifetime of an optical cable after the maintenance cycle. The invention proposes a formula for calculating the remaining lifetime of optical fibers of cable, which has been in operation for some time. Proposed formula based on actual estimates of the strength of optical fibers of cable samples selected from the line.
This work presents method for prediction of laser-excited optical pulse additional distortions, occurring due to contamination of fiber optic connector end-face, under its propagation over short range multi-Gigabit network link with crypto-fibers – couple of special multimode optical fibers “encryptor-decoder”, operating in a few-mode regime. Results of optical pulse response envelop computations, propagating over 1 km link with 500 m crypto-fibers “encryptor” and “decoder” lengths, are compared under various conditions of 10GBase-LX transceiver laser-source fiber optic connector ferrule end-face contamination. Strong pulse splitting additional distortions due to strong ferrule contamination were noticed.
This work is concerned with some aspects of selection of graded refractive index profiles for couple combination of optical crypto-fibers “encryptor”–“decryptor”. We present some results of experimental approbation of method for differential mode delay (DMD) management by selection and recombination of two corresponding refractive index profiles, differing by technological defects in the core center. Here it is supposed, that combined fiber optic link, containing the sequence of two graded-index multimode optical fibers with strong DMD, occurring due to great technological defect of refractive index profile in the core center with a peak (or dip) in the first and, on the contrary, with a dip (or peak) in the second, provide inverting DMD diagram of selected mode components in the second optical fiber in relation to the first. Therefore, according to earlier on proposed alternative method for implementation of secure data transmission channel protected over physical layer for the "first/last mile" segment of intra-corporate network, the first optical fiber with strong unique distortions is considered as “encryptor”, while the second with inverted DMD diagram implements function of “decryptor” in the optical interface.
The article presents a comparative analysis of the reliability characteristics of fiber-optic communication lines in the application of underground laying of optical cable, mini-trench installation technique and cable in the outer protective duct. It is shown that the availability factor of underground laying armored optical is less than that of cables laid in the, outer protective duct and in microduct in the mini-trench.
In this paper the analysis of exceed fiber length distribution in loose tube cable and its relation with mechanical stress was carried out. The polarization reflectometry method for estimation of exceed fiber length distribution along cable during manufacturing and maintenance was proposed. The method of measurement local birefringence using polarization optical time domain reflectometer with three stage polarization controller was proposed. Results of computer stimulation are represented.
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.
One of the important characteristics of the optical cable, affecting its operating parameters, is stiffness. It is known that the stiffness of the optical cable increases at low temperatures due to increase in stiffness of the individual elements of the cable: outer and inner jacket, PBT loose tube and etc. However, as shown by the results of the research, the hydrophobic filling, used in optical cables, also influences on the optical cable stiffness at low temperatures. Results of researches of influence of a hydrophobic filling on stiffness are given in article.
The basic structural element of fiber-optic communication lines are optical cable. An important objective is to study the
reliability of the optical cable depending on the ambient temperature in winter, the deformation of the optical cable and
the optical fibers in loose-tube. The objective of this article is to examine the problems of reliability optical cable during
construction and operation at low temperatures to provide high-quality functioning of fiber-optic communication lines.
Results of the analysis of technical and economic indicators of installation of the cable line on two technologies – traditional with the underground optical cable and duct optical cable are given in article. It is shown that installation cost of the "duct cable" technology is slightly higher. But this technology allows higher reliability of an optical cable in exploitation therefore its application is economically more effective.
Results of research of the gel-filled optical cable at low temperatures are presented in article. It is shown that stiffness of tubes of an optical cable increases at low of temperature more strongly if in tubes there is a hydrophobic filling compound.
The results of measurements of number of fibers with attenuation increasing in the loose tube measured at various deformations of the tube are presented in article. In experiment all fibers in the module were at the same time controlled. By results of experiment function of probability of optical fiber attenuation increasing due to optical cable loose tube is obtained.
In this article the new method of determination of optical cable stiffness at low temperatures is offered. The method is allows to simplify process of measurements. Thus presence of technicians at climatic chamber in the course of measurements is not required.
The main optical and electric characteristics of the combined cable with optical fibers and copper conductors for
installation along the railways are considered. The cable design is described. Results of tests the cables ability to
mechanical loadings and results of measurement of PMD are given. It is shown that the manufacturing techniques of the
combined cable do not make considerable change of optical and electric characteristics of optical fibers and conductors
in a cable.
Results of experimental researches of "optical microcable in a microduct" system stability to effect of freezing water are
presented. It is shown this system is steadier to water freezing in comparison to lighten optical cable in protective
polymer tube.
In article results of experimental researches of incrementation of attenuation in an optical fiber at deformation of loose
tubes are presented. The loose tubes with 4, 8, 12 fibers made from polybutyleneterephthalate were exposed to tests. It is
shown that critical value of deformation of a loose tube at which registered incrementation of attenuation exceeds
threshold value of losses (0,05 dB), changes depending on the square of the area of cross section of loose tube without
fibers practically under the linear principle. The received results of researches can be used for the forecast of optical
cable stability to influence of crushing loadings.
In article results of experimental researches of optical cable behavior in microducts at water freezing are presented. Researches were
carried out with the polymeric and steel microducts. Researches have shown that loadings which influence on a cable at water freezing
in the steel microduct is higher than in polymeric and can lead to attenuation increase in the optical fiber. In the polymeric duct
loadings more low, than in the steel. However if a polymeric microduct freeze in ice, pressure upon a cable as can cause an
incrementation of attenuation.
In article experimental results increase attenuation in dependence of deformation optical buffer tube supply. Subsequent
to the results of tests quantitative estimate increase attenuation in dependence of deformation optical buffer tube receive,
calculate of the coefficients for allowed value deformation tube estimate.
The algorithm of estimation of local lateral stress-induced birefringence in an optical fiber is represented. Results of calculation of mechanical stress and birefringence in an optical fiber under lateral stress are resulted.
Optical cable jointing is one of the most important parts of the fiber optic telecommunication line installation. For
practical applications it is interesting to use some universal material kit for the sealing of the fiber optic closure ports
with various cables, differing by their types and manufactures, in addition to basic closure kit. Here a reasonable
question occurs: is it possible to develop universal instruction manuals for various combinations of optical cable and
universal fiber optic closures, based on closure kit and generalized additional kit, contenting the most conventional
sealing materials? It is obviously, technological tests are required to answer the mentioned question. Here, some results
of investigations are represented.
At increase in a link speed of the data on a fiber optic network up to 40 Gbits with and is higher, influence Polarization
modal dispersion (PMD) increases. Measurements on building lengths were spent, at change of climatic conditions. The
purpose was to reveal influence change ofa climate on PMD in a cable and closure.
Tests on a cable with closure and separately on closures were spent. Schedules of change PMD from temperature were
under construction.
The problems concerning reliability connections of optical cables in closures are considered. Drew conclusions on
necessity of completion of normative base existing today, develop technological cards of installation closures in view of
features such as a cable for which it is used closure, include in techniques of certified tests closures for an optical cable
the control of parameters of transfer of optical fibers in closures.
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