Intelligent underground fiber optic perimeter security system is presented. Their structure, operation, software and hardware with neural networks elements are described. System allows not only to establish the fact of violation of the perimeter, but also to locate violations. This is achieved through the use of WDM-technology division spectral information channels. As used quasi-distributed optoelectronic recirculation system as a discrete sensor. The principle of operation is based on registration of the recirculation period change in the closed optoelectronic circuit at different wavelengths under microstrain exposed optical fiber. As a result microstrain fiber having additional power loss in a fiber optical propagating pulse, which causes a time delay as a result of switching moments of the threshold device. To separate the signals generated by intruder noise and interference, the signal analyzer is used, based on the principle of a neural network. The system detects walking, running or crawling intruder, as well as undermining attempts to register under the perimeter line. These alarm systems can be used to protect the perimeters of facilities such as airports, nuclear reactors, power plants, warehouses, and other extended territory.
The method of a theoretical estimation of optical fiber durability used in optical fiber sensors as a sensitive element, depending on the strain arising at dynamic changes of temperature, pressure and other mechanical influences is offered. The developed analytical model takes into account design features of a fiber (diameters of a core and cladding, a metal or polymeric covering), doping types, relative humidity of an environment. Numerical modeling of silica optical fiber lifetime at dynamic influences of measured temperature and comparison with experimental data is carried out.
The structure of a fiber-optical dynamic memory (FODM) with series-parallel channels of input-output of the digital
information and optical regeneration is developed. Influence nonlinear phenomena in optical fiber on information
characteristics of such systems at spectral multiplexing of information channels is investigated. On the basis of the
developed mathematical model the multiparametric analysis of recirculating process of the information stream in closed optical contour in view of noise sources, ASE-induced timing jitter, and also effect of intersymbol interference is lead. For an estimation of opportunities of use considered FODM as buffer memory are carried out joint researches of a storage time and information capacity at the desired error probability. Laws of influence of contour elements operating modes on extremely achievable information parameters are revealed.
The new quasi-distributed frequency-output fiber-optic recirculating sensors for high-voltage measurements and
perimeter security system have been proposed. Fiber-optic sensor was constructed as a closed optoelectronic contour
formed by a source of radiation, an optical fiber delay line, spectral reflective elements, photoreceiver and regeneration
block. The sensitive element of this device was the optical fiber. The change of recirculation frequency or period of the
contour carried out identification of measured parameters with high accuracy. Sensitivity of these sensors was estimated.
Temperature dependence of measurement accuracy was investigated.
To use the new frequency-output fiber-optic recirculating sensor for voltage, electric current, dispersion properties of the
optical fiber measurements has been proposed. Fiber-optic sensor was constructed as a closed optoelectronic contour
formed by a source of radiation, an optical fiber delay line, photoreceiver and regeneration block. The sensitive element
of this device was the optical fiber. Identification of measured parameters was carried out with high accuracy by the
change of recirculation frequency in the contour. Sensitivity of these sensors was estimated.
Optical fibers as detectors of radiation have a lot of advantages: big length, little diameter, no electrical interference, and an opportunity to measure radiation from the spread source. Optical characteristics of pure silica glasses as a material for optical fibers are very important. Luminescence spectra of high-purity silica glasses made by sol-gel technology have been investigated. Silica glasses are very stable and their characteristics are changed in narrow range. Sol-gel technology was chosen because it allows obtaining samples with different properties during changing technology. In other technologies, uncontrolled admixtures presence leads to big number of luminescence bands appearance. Their analysis is difficult. Luminescence band with energy of 1,9 eV appeared during exposition of glasses to gamma-irradiation. Luminescence intensity dependence on irradiation dose is analyzed. Appearance reasons are investigated. Absorption band with energy 2,0 eV appears in glasses during irradiation due to nonbridging oxygen hole centers (NBOHC:identical to <i>Si</i>- <i>0</i>upward arrow). The same centers are responsible for luminescence with 1,9 eV. Energetic diagram is proposed. Principle scheme of gamma-irradiation optical fiber sensor is proposed on the basis of optical fiber made by sol-gel technology. Optical fiber is illuminated from the lightsource with energy of 2,0 eV. Luminescence appears at those portions of optical fiber, which are exposed to gamma irradiation. Such luminescence pulses are registered from both sides of optical fiber. Travel time is proportional to the distance from the end of fiber to irradiated portion. Length of pulse is proportional to the length of portion. Thermal annealing of optical fiber is discussed.
For registration and processing optical information signals was offered and realized opto-electronic vernier method of temporary situation definition of pulse information sequences, which used one opto-electronic recirculation generator with two optical wavelengths. On one wavelength in a recirculation mode there are information pulses, and on other wavelength-pulses of reference temporary scale. The developed method of automatic digtial-to-analog correction of scales is used. The signal-to-noise ratio in fiber-optic processing systems with avalanche photodiode was investigated.