The presented work compares the methods of probing classical fiber Bragg gratings and targeted fiber Bragg structures in problems of monitoring the parameters of mechanical vibrations. In the course of the work, a prototype of an acoustic system for continuous monitoring of processes based on Bragg gratings was developed and experimentally studied within the framework of trial operation; the limitations of measurement methods based on FBGs were shown. In the course of a comparative analysis of the response of the sensor to a homogeneous FBG and an equivalent AFBS circuit, it was revealed that the transition to addressable structures makes it possible to reduce the lower detected frequency by 3.3 times due to operation in the region of lower noise of the photodetector.
KEYWORDS: Sensors, Fiber Bragg gratings, Temperature sensors, Fiber optics, Transformers, Temperature metrology, Control systems, Air temperature, Temperature control, Fiber optics sensors
In the course of work, a fiber optical system for the temperature of high-voltage busbars, conflicts and other loaded nodes of electrical networks was developed based on the control of fiber Bragg gratings. The system has a temperature determination error of ±1 °C and a resolution of 0.1 °C. Observed temperature changes for high voltage applications have also been considered and observed. The main advantage of the developed system is the ability to quickly use export-optical deliveries as an increase in the level of the system, which in turn is associated with a significant cost of one channel measurement and use per system deployment. In the course of study, the sensor part of the system was developed in the form of two temperature sensors, a sensor interrogation device and its software. Further, a number of experiments on detection of sensors calibration curves was carried out, studies of sensors were carried out for the occurrence of a breakdown between phases, trial operation was carried out at the operating object for selecting electrical networks for one month. The results of the studies show that the system can perform its functions in various operating conditions, the ways of developing the system functions were outlined, which consist in the number of measurements and the use of the system to control the wear of superconducting radiation on contact groups.
The paper describes an approach to the construction of microwave photonic vector analyzers that allow assessing the transfer and linear characteristics of optoelectronic, electro-optical and optical elements. The approach is based on the use of two- and three-frequency probing radiation generated through modulation conversion in an electro-optical Mach-Zehnder modulator.
The paper presents the results of a study of a computer model and a prototype of a probing radiation shaper for radio-photon vector analyzers. The measurement of the dynamic range and the level of nonlinear distortions of the generated radiation was carried out. The limitations of the available CAD for the design of radio-photonic systems in terms of the discrepancy between the obtained results and practical ones are revealed.
This work reports the results of bandwidth measurements and tests, performed for earlier on designed and fabricated pilot lengths of new silica laser-optimized graded-index multimode fibers (LOMFs) with extremely enlarged core diameter up to 100 μm and "typical" "telecommunication" cladding diameter 125 μm. Presented optical fibers are targeted for harsh environment short-range multi-Gigabit onboard cable systems and industrial networks. Proposed LOMF 100/125 differs by specially optimized graded refractive index profile, that provides low differential mode delay (DMD) for selected guided modes. We present some results of tests, performed for fabricated pilot 520 m length of described LOMF 100/125, focused on researches of bandwidth features. They contain DMD map and transfer function measurement as well as 10GBase-LX/SX channels eye-diagram and bit-error-ratio reports with following direct detection of the maximal acceptable optical fiber length for guaranteed 10Gbps channel supporting.
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.
The paper describes the problems of constructing optical branch analyzers. On the example of existing solutions (single-frequency scanning and microwave photonic methods), it is shown that these solutions have a number of limitations, which can be largely removed by a new approach to the construction of probing radiation. A description of the mathematical apparatus for restoring the contour characteristics is presented. A quantitative assessment of the dynamic and nonlinear characteristics of the probing radiation former are given.
The paper presents the concept of liquid media level control systems based on the use of fiber-optic technologies, in particular, addressable fiber Bragg structures. The paper presents methods for the formation of address structures and the principles of retrieving and processing information. The use of addressable fiber Bragg structures makes it possible to abandon the elements of bulk optics in the interrogation scheme, which increases the operational reliability, and simplifies the identification of the sensor in their common array in the measuring system.
A high-precision symmetric optical vector analyzer (OVA) based on amplitude-phase double sideband (DSB) modulation with suppression of an optical carrier is proposed and numerically simulated. Accurate and stable frequency characteristics are achieved by the formation and minimization of such higher-order components in the probe radiation, the difference frequency of which does not coincide with the difference frequency of the two main measuring components of the first order. In comparison with the known solutions, the processing of spectral information is carried out at the modulation frequency, and not at the doubled frequency; the operating range of OVA has been increased by 2 times in terms of the bandwidth of the tested devices; instead of the standard Pound-Drever-Hall technique used to stabilize the laser wavelength with an additional modulator, the technique of controlling the amplitude and phase of the beating envelope of the main probing components is used; the relative error in the reconstruction of the frequency response of the high-Q optical structure at each point does not exceed 5×10–5. The obtained characteristics are confirmed by numerical modeling of the developed OVA when characterizing the spectral parameters of a narrow-band fiber Bragg grating. The presented method is structurally simple, does not require the use of various generators to perform its main functions and monitoring functions, and can be used to characterize both selective fiber-optic structures and high-Q optical Fabry-Perot resonators, resonators based on whispering modes, ring active and passive resonators, transparency windows of nonlinear crystals, plasmon resonances, etc.
The paper presents the concept of a microwave photonic measuring system based on addressed fiber Bragg structures with a polarization multiplexed response. Mathematical models of response of such structures have been developed and verified by computer and physical modeling. The possibility of constructing transverse load sensors that do not require the introduction of additional sensors for temperature compensation of the Bragg grating wavelength shift is shown. A device for interrogating such sensors is proposed and verified.
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