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.
This work presents results of test series, performed for earlier on designed and successfully fabricated twisted silica fewmode microstructured optical fibers (MOF) with six GeO2-doped cores. While Part I introduces results of differential mode delay map measurements, Part II is focused on researches of spectral responses, measured for fiber Bragg gratings, recorded in these multi-core MOFs with core graded refractive index profiles and induced twisting 100 revolutions per meter. Specially setup for spectral response measurement for described complicated fiber optic element was developed, that provides selected alignment of matching singlemode optical fiber with particular single core of MOF via free space and reducing of reflection by precision 8 angle cleaving. Comparing analysis of measured spectral responses confirmed written FBGs in 2 of 6 cores, and demonstrated potentiality of fabricated complicated structure, containing multi-core MOF with FBG, for applications in multichannel fiber optic sensors with spatial division multiplexing technique.
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.
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.
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.
We proposed recently a new «Smart Grids Plus» concept for digital energy grids design. These grids, in addition to layers of intelligent energy grids and information communication channels, include a layer of diagnostic monitoring based on a passive fiber optic sensor networks. Sensor networks have a hybrid TWDM structure – information exchange channels and integrated fiber optical sensors – core, based on a new technology for address interrogation and multiplexing – special addressable fiber Bragg gratings, combined for arbitrary topologies - point and quasi-distributed. Some examples of diagnostic monitoring nets for temperature control of complete switchgear contacts (point) and bus bars (quasi-distributed) are considered. Their principles of operation are discussed. The main advantages of these sensor networks are using of addressable fiber Bragg gratings simultaneously as sensors and multiplexing elements, and using of PON structure simultaneously as sensor and communication networks.
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