Universal problem of spectral characterization for element base of microwave photonic means from broad band electrooptic and optical electronic modulators and receivers to narrow band Bragg and Fabry-Perot filters is very actual. The presented modulating and forming devices contain, in a minimal structure, a special laser diode and two modulators, the first of which is calibrated (master) and has a significant impact on the accuracy of modulation and forming in second (functional), and ensuring the operating modes of both modulators affects the complexity of the devices structure. The last one element is photoreceiver with given characteristics as laser diode ones. The purpose of the work is to present developed devices for various implementation with a minimized structure and simple control, which allow achieving results similar to those obtained using complex multi-stage, two-port, dual, parallel, polarization divided Mach-Zehnder modulators, accompanied with acousto-optic and polarization modulators, all of which have become unavailable under the sanctions pressure. Their advantages can become more significant using microminiaturization technologies – combined microwave and photonic, photonic and quantum integrated circuits (PIC), developing in KNRTU-KAI and UUST, especially under the influence of external climatic factors. These aspects are discussed in the report using the examples of instantaneous frequencies measurements, broadband spectral characteristics of modulators and photoreceivers, quantum key distribution systems with frequency coding. Few words are said about sensor networks.
This article describes a new method for the Doppler frequency shift (DFS) measurement of a radar microwave signal reflected from a moving object, based on radio photonics technologies. The DFS measurement device has the same structure as the sequential radiophotonic link with filtration and consists of a laser, a block of electro-optical modulators, a fiber Bragg grating (FBG), and a photodetector. The block of electro-optical modulators, in contrast to the known solutions based on a two-port Mach-Zehnder amplitude modulator, is based on two subunits, consisting of connected tandem single-port amplitude and phase modulators (TAPM). The general structure of the TAPM subunits is parallelserial. The microwave signal reflected from the object arrives at the first TAPM, which forms the measurement channel. The second and third TAPMs, connected in series, form a reference channel connected in parallel to the measurement one. The second TAPM receives a reference signal from the locator transmitter at the probing microwave frequency, after which the two-frequency radiation, spaced by twice of the probing frequency, is fed to the third TAPM, which generates from each component of the two-frequency radiation two more with a difference frequency equal to twice the maximum possible DFS. The beats of signals from the measurement and reference channels at the output of the photodetector are three high-frequency (GHz) or low-frequency (MHz) electrical signals, the frequencies and powers of which used for the DFS determination.
This article describes a new approach for the estimation of the direction or of the microwave signal reflected from the object, based on radio photonics technologies. The angle of arrival measurement device has the same structure as the classical fiber-optic communication channel and consists of a laser, a block of electro-optical modulators and a photodetector. The block of electro-optical modulators, in contrast to the known solutions based on a two-port Mach- Zehnder amplitude modulator, is based on two parallel subunits, consisting of tandem single-port amplitude and phase modulators (TAPM). A microwave signal reflected from the object with a time delay, the value of which is determined by the AOA, is sequentially received at the radio frequency inputs of two TAPMs through the receiving antennas connected to them. In this case, the initial components of the laser carrier at the output of the TAPM subunits of both channels are completely suppressed, which significantly distinguishes the proposed solution from the known ones for the better in terms of increasing the measurement accuracy. The beats of the output signals of the TAPMs at the output of the photodetector represent a signal reflected from the object, according to the power of which the AOA can be determined.
This work considers the issue of creating and promoting student communities focused on attracting young people to modern scientific work and development, in particular in the field of photonics and fiber optics. The materials of the article are based on the experience of implementing the project "Student Community of Photonics and Fiber Optics" and are devoted to management issues in the context of a well-established hierarchical approach to management in classical universities. In the course of the work, tasks were set and ways to solve them were described. Particularly important aspects of the influence on the future career guidance and career aspirations of the youth groups under consideration are reflected.
This article describes the design principles of optoelectronic system for instantaneous frequency measurement of microwave signals based on the use of amplitude-phase modulation conversion of single optical carrier into symmetrical dual-frequency ones for additional frequency separation according its wavelength, its modulation by unknown frequency and subsequent “frequency-amplitude” measurement conversion in fiber Bragg grating with Gaussian reflection profile along with the variations of schemes for realization of this method with the corresponding spectrums. Such approach increases the signal-to-noise ratio and allows measuring of several unknown frequencies simultaneously. Distinction and measurement of the instantaneous frequencies made depending on the amplitudes and modulation indexes of the signals received at the photodetector.
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