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.
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.
The problems of synthesis and application of fiber Bragg gratings with special spectrum shapes in measurement and information channels of quazi-distributed fiber optic systems for climatic test systems are introduced. In particular, gratings with concave, triangular symmetric and triangular asymmetric spectrum shapes are considered, also the new poly-harmonic methods of its interrogation are presented. Projects of system decisions and results of experimental researches of its blocks are discussed.
The paper is devoted for presentation of training course for applications and construction principles of poly-harmonic (two-frequency or four-frequency) cw laser systems for characterization of different nonlinear scattering effects in fibers and reflection of devices based on fiber Bragg gratings (FBG) in down-hole telemetric sensor nets, which are widely used in down-hole telemetric systems. In particular, we’ll speak about evaluation of Mandelstam-Brillouin gain contour, Raman scattering contours and FBG reflection spectra characterization. Investigation methods and approaches are based on the unity of resonant structures of generated fiber responses on exciting and probing radiation or external physical fields for all given effects. The main decision is based on poly-harmonic probing of formed resonance responses. Training course united idea is software defined approach for down-hole parameters characterization in spite of measuring conversion principles.
This paper presents a microwave photonics method for the instantaneous frequency measurement of microwave signals,
based on the generation of a two-frequency laser radiation in the Mach-Zehnder modulator with a difference frequency
equal to the measured, and the "frequency - amplitude" conversion in the π-phase-shifted fiber Bragg grating. Frequency
measurement occurs in two ranges: 0.3 - 3 GHz in the passband of the FBG and 3 - 30 GHz in its reflection band. Using
the specific conversion of two-frequency radiation in the π-phase-shifted fiber Bragg grating allowed us to obtain measuring
characteristics, that are independent of the amplitude fluctuations of the optical carrier and to organize additional
circuit for monitoring the spectral characteristics of the used elements to reduce measurement inaccuracy caused by their
temperature instability.
The paper considers possibility of using a system based on amplitude measurement method with a fiber Bragg grating as
a sensitive element. The features of measurement technique is application of Bragg gratings with a special spectrum
structure for different industries.
Problems of refractometric optical biosensors and courses of their fast and technological decision are considered. In particular
the resolution and sensitivity increase, formation of stable on amplitude and spectrum cleanliness probing radiation,
allocation of refractometric information from a complex of sensor parameters defined by universality of FBG response
to changes of pressure, temperature and refraction factor, construction of dot type sensors and the distributed
networks on their basis are analyzed.
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