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.
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.
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.