RESEARCH TASKS
There is examined, tested and built connection with the integrated facilities for providing border security, both land and sea, and the infrastructure objects, including protection of harbor equipment, employment of fiber-optic sensors and distributed parameter systems based on the same. The research tasks are focused on development and examination of sensors purposed for security and protection.
Generally, the sensors are divided in two groups:
1. Sensors with lumped parameters, the complete system and network being built of many sensors as two-dimensional antenna.
2. Sensors with distributed parameters, where the sensor gives information about the location of the arising events.
The first group includes, for instance, sensors on the base of Mahzender, Michelson, Sanyak, fiber-optic interferometers. The individual sensors are multiplexed on the base of their time frequency characteristics. The employment of broadband laser source or laser of high degree of coherence and re-adjustable wavelength is substantial. Depending on the individual configurations both variants could be employed.
The second group includes development and investigation of the long-term stability of the sensors using the effects of Rayleigh or Brillouin back scattering. The operating mode in case of land object defense can be described generally as follows: The system for detection and localization of vibrations caused by walking human consists of i/ fibre barriers buried at 20 – 30 cm under the ground and locating up to 1 m from the fence; and ii/ fibres attached to the fence. The fibres are connected to electronic system, computer with appropriate software and analysing visual controller.
The optical principle is a Phase Sensitive OTDR. A short impulse from a single frequency semiconductor laser is transmitted along the fibre. The high sensitive optical receiver detects the Brillouin scattered light. The signal is continuously decreasing due to the optical losses along the fibre. The temporal resolution of the A/D converter is higher than 30 ns and allows discrimination of local disturbances at more than 10 m. The signal without disturbances is stored in the memory. The next signal is compared to the stored one.
The system can cover distances up to 15 miles with resolution 20 to 100 meters.
The following tasks are being executed:
1. Development of various types of sensors of different purposes.
2. Development of methodology for differentiation the type of violation in the protected area which will result in improved reliability in cases of false alarms.
3. Development of integral systems for prevention of threats against land and sea borders, small or large infrastructure objects depending on the requirements for level of protection, which determines the cost price and the economical expedience of the sensors.
ANTICIPATED EFFECTS AND RESULTS
In the scope of “Borders security” high operational properties of the sensors developed shall be achieved in result of:
- ability for covering long distances with low exploitation costs and System control by one operator;
- high resistance against EMI noise;
- very low vibration spectrum frequency enabling to detect human steps through the spectrum analysis software, which allows to discriminate the false signals;
- possibility for protection against underground tunnel below the fence;
- easy and fast installation and maintenance and long, more than 10 years, maintenance free period;
- high resistance to changing meteorological conditions;
- easy multiplication with other series and parallel security nets;
- low price per linear meter, etc.
Founding an appropriate base for the development of next generations of sensors will permit a long-term and stable progress of the research activities in this field.