The requirements of the mass consumer and educational market impose great restrictions on the cost of hardware-software demonstrators with relatively low requirements for the characteristics of the quantum key distribution process. This means that these devices do not have to be advanced and, as such, can provide a dramatic reduction in size, weight, and power compared to other quantum key distribution systems. The article presents the stages of development and creation of an experimental prototype of a hardware-software demonstrator of a universal quantum key distribution system that implements existing methods based on amplitude and phase modulation, as well as the proposed method of tandem amplitude-phase modulation of an optical carrier. The evaluation of the technical, economic and operational characteristics of the hardware-software demonstrator was carried out; practical recommendations were formulated for its development, creation and operation, as well as for the choice of an import-substituting element base, which ensured its low cost and the possibility of wide use at various research and educational sites, including World Skills youth championships and Future Skills process. In addition, the proposed demonstrator, embedded in a desktop computer, can act as access devices that can be connected to a terminal combined with a quantum network node to replenish a secret key store, which can then be used to encrypt daily activities on conventional platforms such as the Internet.
Seven years ago, we proposed the concept of addressed fiber Bragg structures (AFBS), which simultaneously perform the functions of: a complexed sensitive element based on two FBGs (2λ-AFBS) with different Bragg frequencies or FBG with two π-phase shifts (2π-AFBS), the difference frequency of which is the AFBS address and the value of it is invariant to measured physical fields; a two-frequency laser radiation source, which can operate as in reflection, so as transmission mode respectively to structure above, a self-multiplexed set of sensors, if the difference frequency will be unique for each AFBS, enabling their address multiplexing. In this article, we consider the ontology of AFBS, including the parent structures with 2λ- or 2π-components, successor AFBS with three spectral components and various combinations of difference frequencies: symmetrical and asymmetric, performing the functions of the addressing and converting information signals to the low-frequency region at the same time, along with the functions of rejecting collisions caused by the relative movement of structures relative to each other during measurements. The subjects of interrogation of these structures and their calibration are discussed as well as prospects of AFBS further development based on common tasks born by ontology formalization and decisions of applicability tasks.
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 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.
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