We present new type of silica graded index laser-optimized multimode optical fibers (LOMF) with extremely enlarged core diameter up to 100 μm and “typical” “telecommunication” cladding diameter 125 μm. This optical fiber was designed for harsh environment Gigabit onboard cable systems and industrial networks. It differs by special optimized graded refractive index profile, providing low differential mode delay (DMD) for selected guided modes. We present some results of tests, performed for manufactured pilot 520 m length of described LOMF 100/125, concerned with its geometry properties as well as key transmission parameters—attenuation and DMD map.

This work presents designed and fabricated silica few-mode optical fiber (FMF) with induced twisting 10 and 66 revolutions per meter, core diameter 11 µm, typical “telecommunication” cladding diameter 125 µm, improved height of quasi-step refractive index profile and numerical aperture 0.22. Proposed FMF supports 4 guided modes over “C”-band. We discussed selection of specified optical fiber parameters to provide desired limited mode number over mentioned wavelength range. Some results of tests, performed with pilot samples of manufactured FMF, are represented, including experimentally measured spectral responses of laser-excited optical signals, that comprise researches and analysis of few-mode effects, occurring after fiber Bragg grating writing.

This paper presents a new two-frequency method for the instantaneous frequency and amplitude measurement of unknown microwave signal. Using the specific interaction of two-frequency radiation with fiber Bragg grating (FBG) in first version and FBG with phase π-shift in second allowed us to obtain measuring characteristics, that are independent of the energy fluctuations of the optical carrier and the microwave signal. Frequency measurement occurs in two ranges: 3-30 GHz in FBG reflection band, and in second version 0,3-3 GHz in the FBG pass band. Additional circuit for spectral characteristics monitoring of the used elements are organized to reduce measurement inaccuracy caused by their temperature instability.

This work presents a fabricated silica few-mode microstructured optical fiber (MOF) with a special six GeO₂-doped core geometry, an outer diameter of 125 µm (that corresponds to conventional commercially available telecommunication optical fibers), and improved induced twisting up to 500 revolutions per 1 m (under a rotation speed of 1000 revolutions per meter with a drawing speed of ~2 m per minute). The article discusses some technological aspects and issues of manufacturing the above-described twisted MOFs with complicated structures and geometry as GeO₂-doped silica supporting elements for them. We present results of some measurements performed for fabricated samples of chiral silica six-GeO₂-doped-core few-mode MOFs with various orders of twisting and both step and graded refractive indexes of “cores”. These tests contain research on MOF geometrical parameters, attenuation, and measurements of the far-field laser beam profile.

In this paper, a two-element sensor of relative humidity of a parallel structure is proposed for consideration, which differs from the existing ones by using address fiber Bragg gratings made in SMF-28 fiber. One of the grids has a quartz shell replaced by polyimide, synthesized using a fiber coating with a full multiplicative response to temperature and deformation caused by humidity. The second grating recorded in a standard fiber and responds to temperature. It is possible to include an additional third grating with a partially etched cladding, which can be used for refract metric measurements of the amount of condensed moisture on the elements of a complete switchgear. All gratings are identical, have the same Bragg wavelength, after manipulating their claddings, but differ in a unique address, which is formed by recording two transparency windows in each of the gratings with different difference frequency space. The transparency windows correspond to phase π-shifts symmetrically located at the same distance from the center of each of the gratings. The structure obtained makes it possible to record information of the measurement conversion at the indicated difference frequencies in the radio range, which significantly increases the speed of measurements of relative humidity and their accuracy by an order of magnitude. In addition to what has been said, it is possible to note the possibility of building a network of these sensors in consecutively arranged switchgear devices, with a different radiofrequency address group being used in each of them.