RU128372U1 - FIBER OPTICAL SECURITY DEVICE BASED ON RELAY SCATTERING - Google Patents

Abstract

A fiber-optic security device based on Rayleigh scattering containing a coherent radiation source, a fiber optic cable and a photodetector, an optical splitter and an optical circulator, characterized in that the device uses a single-mode fiber optic cable, the first output of the optical splitter through an optical radiation modulator and a circulator connected to a single-mode fiber-optic cable, the third output of the circulator is connected to the mixer, through a balanced photodetector, and the second input a photodetector is connected to the second output of the optical splitter through a polarization and phase regulator, the second input of the mixer is connected to one of the outputs of the probing signal shaper, the other output of the shaper is connected to the control input of the modulator, and the output of the mixer is connected to the output of the device through a low-pass filter.

Description

The utility model relates to fiber-optic devices designed to protect objects with a large territory.

Well-known security fiber optic devices (see, for example, invention patents No. 2188858, 1999, or No. 2311687, 2004) are mainly intended for the protection of objects with a small perimeter. The input of the light pulse is carried out at the beginning of the optical cable, and the output at its end, which is usually located on the control panel. Moreover, the optical cable itself usually covers the perimeter of the protected area, for example, the SOVA security system (7.html). The device has a unit for receiving optical radiation (BPi), and a processing unit (BO), which can determine the vibration of the cable and approximately localize the area of mechanical stress along the cable by processing the information received by the BPI unit.

Fiber-optic alarm devices are also known (see, for example, patent for invention No. 95108004, 1997), operating on the basis of analysis of the reflected light signal in a multimode fiber-optic cable. However, the size of the protected objects using such devices is limited to hundreds of meters (up to 1 km), and the site of localization of the impact cannot be less than 100 m.

The technical result of the claimed utility model "Fiber-optic security device based on Rayleigh scattering" is to increase the detection range of mechanical effects on the optical fiber cable (by almost two orders of magnitude, up to 100 km), and to increase the accuracy of localization of this effect (from 100 to 3 meters, due to technical solutions).

The technical result is achieved by the fact that in the inventive utility model. a single-mode fiber optic cable is used, and mechanical vibration acting on the cable due to Rayleigh scattering of light in a single-mode fiber leads to its linear polarization. The device comprises a unit for generating an optical probe signal, and its directional input into the acoustically sensitive fiber 5 (AFC) of the optical fiber cable (Fig. 1). This function is performed by a laser radiation generator 1 (GLI), operating continuously at a wavelength in the infrared spectrum, with a narrow line and high power. The device has a block for receiving and preprocessing signals reflected from randomly located 5 (AFC) Rayleigh scattering centers. Radiated 1 (GLI) signal is divided in a ratio of 20: 80% using an optical splitter 2 (OR). In this case, most of the emitted signal is converted in the optical radiation modulator 3 (MOI) into a pulsed signal shifted in frequency by 100 MHz. Part 3 (MY) includes an acoustic modulator, and the formation of the probing signal is carried out using a double balanced mixer and a balanced power amplifier. At the input 1 of the shaper of the probing signal 6 (FZS), short (50 ns) periodic pulses with a high duty cycle (period of 50 μs) are applied. and a sinusoidal signal with a frequency of 100 MHz is supplied to input 2.

The optical sounding signal after modulation to 3 (MOI) through the optical circulator is fed to 5 (APC). The signal reflected from the Rayleigh scattering centers at 5 (APF) returns to the arm 2 of the optical circulator 4 (OC), and through it enters the input 1 of the balanced photodetection unit 8 (BFD). The other 2nd input of balanced photo-detection 8 (BFD) receives an unmodulated signal from the second output 2 (OR). The coordination of polarization states and phases is carried out by the regulator 7 (RPF). An electric pulse signal with a filling frequency of 100 MHz at the output 8 (BFD) is demodulated using a mixer 9 (SM), similar to a mixer in 6 (FZS), and pulses whose amplitude depends on the phase change of the optical radiation due to acoustic exposure are extracted using a filter low frequencies 10 (low-pass filter) with a band of 20 MHz.

Tests of the claimed utility model have been conducted. In this case, the device used the following standard equipment:

1. GLI - laser radiation generator (used precision laser PS-LM-1550.92-100-06, operating in continuous mode at a wavelength of 1550.92 nm;

2. OP - optical splitter (used CE-1-2X2-1.3 / 1.55-20% * 80% -10-FC / APC);

3. MY - optical radiation modulator (the acoustic modulator AOM -1550-01 was used);

4. OTs - optical circulator (CIR-4-15-1-10-FA);

5. APF - acoustically sensitive fiber (G.652);

6. FZS - probing signal shaper (a double balanced mixer on the LAM - 81008 chip was used, and a balanced power amplifier on two BGY85 chips);

7. RPF - polarization and phase regulator (FPC030);

8. BFD - balanced photodetector (PDB410);

9. SM-mixer (LAM-81008);

10. Low-pass filter - low-pass filter;

During the tests, it was found that the detection range of the mechanical impact on the fiber optic cable increased significantly (from 1 km to 100 km).

The accuracy of a fiber-optic security device based on Rayleigh scattering, when determining the place of mechanical impact on an optical single-mode cable, increased several tens of times, and with a cable length of 5 km, it was only 5 m.

This utility model can be successfully used to protect objects commensurate in area with Moscow, limited by the Moscow Ring Road. Very effectively, this device can be used to protect oil pipelines and gas pipelines, as well as highways and railways, and to protect the border strip.

Claims (1)

A fiber optic security device based on Rayleigh scattering, containing a coherent radiation source, a fiber optic cable and a photodetector, an optical splitter and an optical circulator, characterized the fact that the device uses a single-mode fiber-optic cable, the first output of the optical splitter through the optical radiation modulator and the circulator is connected to the single-mode fiber-optic cable, the third output of the circulator is connected to the mixer, through a balanced photodetector, and the second input of the photodetector is connected to the second output of the optical splitter through the polarization and phase regulator, the second input of the mixer is connected to one of the outputs of the driver of the probe signal, the other output of the driver is connected to the control input of the modulator, and the output of the mixer is connected to the output of the device through a low-pass filter.

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