The paper describes the implementation of a fiber-optic single-channel vibration sensor built on the basis of two fiber Bragg gratings, a broadband source, a photodetector and a sound card of a computer used as an ADC
Keywords: vibration, fiber optic sensor, fiber Bragg grating, Fourier transform
The complexity and high cost of multiplexing optical fiber sensors is still the main limitation for the widespread introduction of sensory systems, both distributed and quasi-distributed, and point-like. The article proposes a new multiplexing method that takes advantage of both broadband and two-frequency radio-photon multiplexing systems. The simplest broadband radiator is taken from the first, but a complicated and expensive system of spectrometry is not used to determine the central wavelength of fiber Bragg gratings. From the second, a recording system is used at the beat frequency between two components, but an expensive system for generating two- and polyharmonic probing systems is not used. The multiplexing parameter is determined by the frequency of separation between the transparency windows of a fiber Bragg grating, for example, with two phase π-shifts, which differs by a certain value for each of the sensors. The mechanism of modeling of gratings of the specified type is given, in principle the possibility of multiplexing of various number of sensors is shown. When using sensor networks built on the basis of passive optical, the number of multiplexed sensors can reach 256, with all sensors having the same Bragg wave of the wave, and can be combined into tree, bus and other topologies.
Keywords: fiber Bragg grating, phase inhomogeneity, fiber optic sensor, multiplexing, transparency window, frequency difference between transparency windows, beat frequency
A variant of the solution of the problem of characterization of a resonant Fano contour in optical biosensors of refractometric type based on ring fiber Bragg gratings with pi-shift is presented. The use of biosensors of this type makes it possible to increase the sensitivity of detecting changes in the refractive index of the medium under investigation to the level (1-2) x10-9 RIU. These sensitivity values are achieved due to the formation in the lattice of a high-quality Fano resonance with a loop width at half-height equal to 1-5 pm. However, the possibility of obtaining a significant gain in metrological characteristics on the one hand, poses the problem of characterizing such narrow-band resonances on the other, since the existing optical spectrum analyzers do not have the appropriate resolution. To solve this problem, we propose a radio-photon method of three-frequency probing of a high-band and an asymmetric Fano contour by symmetric amplitude-modulated radiation with side-amplitude components unbalanced in amplitude. In contrast to the previously used for solving similar problems of two-frequency symmetric sounding with equal amplitudes of side components and a suppressed carrier, we have uniquely determined the central frequency, the maximum amplitude and Q of the Fano circuits, as well as the possibility of greatly simplifying the technique of collecting information on their parameters. The article consists of two parts, which consistently reflect the posing of modeling problems and discussing its results with confirmation of the results of physical experiments.
Keywords: optical biosensor, refractometry, Bragg fiber grating, phase pi-shift, Bragg annular fiber grating with phase pi-shift, Fano resonance, refractive index change, sensitivity, resolving power, radiophoton measurement methods, two-frequency symmetric balance
An overview of the basic schemes, characteristics, and directions of development of microwave photonics systems is presented in this paper in terms of requirements defining the parameters of external amplitude-phase modulation of laser radiation as a key process for the formation of radio frequency signals in the optical range for systems with polarization multiplexing of polyharmonic signals.
Keywords: microwave photonics; external amplitude and phase modulation, optical generation of radio frequency signals; generation of poly-harmonic optical signals with microwave frequency components
Paper deals with the analysis and synthesis of geographically distributed systems for storage of hazardous substances from the environmental safety position. Particular attention is paid to the information layer to ensure environmental safety (ES) of these systems, which operates on the results of the processing of regulatory documents, environmental monitoring data, analytical reports, etc. Its operation is based on a system of specialized automated workplaces (AWP), each of which generates a plurality of projections and calculations in order to provide ES, using information on three levels of detail: the physical, technological and logical. The structures of mathematical, informationtion, software and hardware provision of AWP are discussed. It is shown that the proposed AWP structure can be used in the design of the various systems for storage of hazardous substances and is aimed to provide ES in their operation.
Keywords: geographically distributed storage systems, hazardous materials, environmental security, information maintenance, environmental specialists, workstation
From the standpoint of environmental safety paper deals with the analysis and synthesis of geographically distributed systems for storage of hazardous substances. The main attention is paid to the technical maintenance of ecological safety of these systems which is determined by the layer of tool control system (TCS) in ecological situation monitoring channels, storage of hazardous substances and protection parameters of perimeter storage. Operation of TCS relies on the use of fiber-optic sensors based on fiber Bragg gratings in each of said channels and their methods of polyharmonic probing. Defined principles of joint measurement of temperature and pressure as the main storage options, optical absorption measurements of gas concentrations using remote multicomponent fiber optic infrared analyzer for monitoring the environmental situation are discussed. The information about the construction of storage areas perimeter security systems sensors are given. It is shown that the proposed TCS structure can be used in the design of the various systems of hazardous substances storage and is aimed at addressing issues of environmental safety in their operation.
Keywords: geographically distributed storage systems, hazardous materials, environmental security, technical support, fiber Bragg grating, measurement of temperature and pressure, multi-fiber optical infrared gas analyzer
The principles of construction of the interrogator for fiber optic sensors based on Bragg gratings, implementing radiophotonics measuring conversion technology on the principle of "optical wavelength - the amplitude and phase of a radio signal - measured value" are concerned. Their comparison with classical opto-electronic and radio photonic interrogator, implementing technology measurement conversion on the principle of "optical wavelength - radio frequency - the measured value" are produced. It is shown that the opto-electronic interrogator have significant limitations on resolution and interrogation speed and difficulty of simultaneous measurement of multiple, complexed to at least two measured values. Radiophotonic frequency interrogator, built on the basis of interferometers with additional dispersion conversion "rate - time" or optoelectronic oscillators allow to overcome the drawbacks of optoelectronic, but characterized by the complexity of the implementation of schemes of measuring conversion shift of the center wavelength of the grating in the information of unknown frequency. Radiophotonic amplitude-phase interrogator which is working at a known frequency - radio frequency envelope of the beat between the components of the two-frequency probe radiation signal, are proposed. This technique allows to exclude from the measurement process information search procedure of unknown frequency or amplitude of the maximum reflection of the FBG, which improves the speed and resolution of interrogation. Experimental results are presented to verify the procedure.
Keywords: fiber optic sensor, fiber Bragg grating, optoelectronic interrogator, radiophotonika, opto-electronic oscillator, measuring conversion type "optical wavelength - the frequency of the radio signal - measured value", measuring conversion type "optical wavel
The principles of construction of sensory passive optical networks, implemented the concept of the unified field of complexed fiber optic sensors and based on hybrid wave and time division multiplexing, are discussed. Their advantages in comparison with classical techniques of oneparameter multiplexing by time, wavelength, frequency, space, codes, etc. are shown. Prototypes and the structure of the sensory passive optical network with a hybrid wave and time division multiplexing are presented. The ability how to survey the point sensors, sensors of quasi-distributed and distributed types are defined, so as ability how to use the probing signals of pulse and continuous types. Especially the issues of similar probing of consecutive Bragg gratings using layered exclusion mechanisms (pulse sensing) and Q-factor measurement of the total envelope of the gratings spectrum (continuous amplitude-phase sensing) are explained. The requirements for the construction of sensory passive optical networks based on the hybrid wave and time division multiplexing in diverse parameters matching of Bragg gratings wavelength with multiplexers based on arrayed waveguide grating are presented. This requrements are based on the possibility of using the latter as support structures for interrogation of the first. Variants of the networks and their characteristics are presented.
Keywords: unified field of complexed fiber-optic sensors, sensory passive optical network, the hybrid time and wave division multiplexing, pulse and continuous probing, fiber Bragg grating, arrayed waveguide grating
The principles of intelligent node of electroengine - brush are discussed. Into the brush an optical fiber sensor of wear and temperature on the basis of serial low reflection fiber Bragg gratings (FBG) is embedded. In contrast to existing, developed sensors are complexed and are able to simultaneously measure the temperature of the shift of the central wavelength of laser radiation reflected by the FBG, the amount of wear by means of registration the change in the length of the FBG arrays. Analysis of the signal reflected from the FBG allows you to define the parameters of the engine speed, temperature changes - the state of brush-collector unit. At a resolution of the interrogator in the wavelength about 2 ps the temperature sensor has resolution 0,2 ° C. Measurement error values of wear sensor, determined by the stability of the amplitude parameters of laser radiation, are near tenth part of micrometer.
Keywords: friction, complexed fiber optic sensor, fiber Bragg grating, wear, temperature,electroengine, smart brush, rotation speed