Earlier on we introduced model of piece-wise regular fiber optic link, operating in a few-mode regime: laser-based data transmission over large core optical fiber. Presented model is based on piecewise regular representation with general approach of split-step method application. It allows to take into account laser-excited optical signal launching conditions, differential mode delay, differential mode attenuation, higher-order mode chromatic dispersion and mode mixing / power diffusion, occurring due to optical fiber irregularity and fiber optic cable bends / twisting / stress / tension. While optical fiber irregularity can be directly set by protocols of optical fiber outer diameter monitoring system of drawing tower, cable external mechanical influences are simulated via equivalent angular misalignment at the splices of regular spans. Therefore, this work is concerned with issues of selection of this equivalent angular misalignment (EAM). We performed a computational test series under various values of mentioned above EAM under following comparison with experimentally measurements of few-mode optical pulse responses at the output of multimode optical fibers with strong differential mode delay effect.
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 and 600 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 graded refractive index profiles with height 0.0275. While Part I introduced results of differential mode delay map measurements with laser source excitation / laser-based data transmission over multimode optical fibers (MMFs) with core diameters 50 and 100 µm, combined with 6-core MOF, and Part II was concerned with researches of spectral responses, measured for fiber Bragg gratings, recorded in these MOFs, Part III reports results of far-field white light beam profile measurements, performed for weakly and strong twisted 6-core-MOFs.
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.
This work introduces first time fabricated spun silica microstructured optical fiber (MOF) with inclusion seven GeO2-doped capillaries, placed in the central part of MOF cross-section, and induced twisting. While Part I discussed technological issues for manufacturing of described complicated twisted fiber optic structure, presented some pilot samples of described MOFs with various twisting order and measured their transmission spectra, Part II describes some results of results of experimental researches, performed for successfully manufactured twisted MOF pilot samples with typical hexagonal geometry under hole radius 4.40 μm and pitch 9.80 μm, outer “telecommunication” diameter 125 μm, and center part, formed by seven hollow GeO2-doped ring cores with inner radius 2.50 μm, pitch 8.80 μm and refractive index difference Δn=0.030 with induced twisting 130, 300 and 730 revolutions per meter. Following test series were performed: measurements of far-field laser beam profiles, some attempts of fusion splicing of typical telecommunication optical fibers and fabricated MOF with insertion loss estimation, and spectral response measurements of both single and group WDM (Wavelength Division Multiplexing)-channels of commercially available telecom WDM-system under inclusion of 2 m length MOF into various spans of short-range lab fiber optic link.
This work considers the issue of creating and promoting student communities focused on attracting young people to modern scientific work and development, in particular in the field of photonics and fiber optics. The materials of the article are based on the experience of implementing the project "Student Community of Photonics and Fiber Optics" and are devoted to management issues in the context of a well-established hierarchical approach to management in classical universities. In the course of the work, tasks were set and ways to solve them were described. Particularly important aspects of the influence on the future career guidance and career aspirations of the youth groups under consideration are reflected.
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.
This work presents fast and simple method for estimation of the reflection at the connection of two singlemode optical fibers with contaminated fiber optic connector ferrule end faces via results of analysis of connector ferrule end face photo-image. Proposed solution is based on discretization of mode field distribution and following passage to representation of the mode field overlap integral in the form of finite nested sums. Proposed approach provides ability of taking into account the mode field distortions, occurring due to the optical fiber end face contaminations, by directly overlapping of connector ferrule end face image over discretized mode field radial distribution. We present some results of developed method approbation on really measured fiber optic connections between standard singlemode optical fibers with various order contaminated ferrules.
This work presents fast and simple method for estimation of the insertion loss at the connection of two singlemode optical fibers with contaminated fiber optic connector ferrule end faces. Proposed solution is based on the fundamental mode coupling coefficient (or e.g. transmission coefficient) evaluation via discretized mode field overlap integral. It is represented in the form of nested sums on radial mode field distributions, which are described well by Gaussian function under weakly guiding approximation or may be taken from the mode field distribution matrix, computed by rigorous numerical methods during analysis of real optical fiber samples with nonsymmetrical geometry. Proposed approach provides ability of taking into account the mode field distortions, occurring due to end face contaminations, by directly overlapping of connector ferrule end face image over discretized mode field radial distribution. We present some results of developed method approbation on really measured fiber optic connections between standard singlemode optical fibers with various order contaminated ferrules.
This work presents an alternative method implemented in software procedure for automated localization of fiber optic connector contaminated ferrule end face image artifacts. Here the main problem is concerned with detection and removing the aureoles of core/cladding and cladding/ferrule boundaries without impact on pixels of contamination particles. We considered typical end face images measured by commercially available fiber optic video probe kit containing video microscope and software, which provides ferrule end-face quality inspection "PASS/FAIL" according to ratified standard IEC 61300-3-35 that is a global common set of quality requirements for the surface of ferrule fiber optic connectors. After removing artifacts, modified image may be utilized for the following estimation of the predicted value of insertion loss. We also present some results of proposed procedure approbation for various order contaminated ferrule end face images.
This work presents research results of fiber optic connector ferrule end contamination impact on degradation of key parameters – insertion loss and reflection. We tested four sets of couples of fiber optic connections performed for FC/PC connectors of the same type optical fibers – singlemode (SMF-SMF) and multimode (MMF-MMF) – as well as for differing optical fiber types – SMF-MMF and MMF-SMF. Contamination assessment degree over the connector ferrule end face was estimated by using video probe kit containing video microscope and software which provides ferrule end face quality inspection "PASS/FAIL" according to ratified standard IEC 61300-3-35. The IEC 61300-3-35 standard is a global common set of quality requirements for the surface of ferrule fiber optic connectors. This standard defines 3 zones of ferrule end face: "A" – core zone; "B" – cladding zone; "C" – ferrule zone. Results of direct research of fiber optic connector ferrule end face contamination impact on the insertion loss and reflection are represented.
We present alternative method for implementation of secure data transmission channel protected over physical layer for the "first/last mile" segment of intra-corporate network by specialized fiber optic link. Proposed solution is based on application of operating in a few-mode laser-based regime multimode optical fibers with special refractive index profile providing optical pulse strong uniquely distortions due to differential mode delay effect that allows to consider those optical fibers as "encryptor". Therefore, transmitted traffic is strongly distorted and it is unable to be processed without corresponding "decryptor" which might be either also another one optical fiber with "inversed" refractive index profile in relation to the "encryptor"-fiber or electronic dispersion compensator device modified for such application. This work is concerned with configurations of proposed "crypto" fiber optic link as well as brief description of math apparatus for design it. Some results of preliminary simulations are also represented.
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.
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