Perimeter security system based on single optical fiber and fiber bragg grating of single optical fiber

Abstract

The invention discloses a perimeter security system based on a single optical fiber and a fiber bragg grating of the single optical fiber, which is suitable for fields such as optical fiber communication and optical fiber sensing. An output end of a light source (1) of the system is connected with an input end of a phase modulator (13); an output end of the phase modulator is connected with a first branch (101) of a Y branching device; a second branch (102) of the Y branching device is connected with an input end of a wave separator (3); a third branch (103) of the Y branching device is connected with one end of an optical fiber (4); a knocking signal (5) is applied to the optical fiber and an output end of the wave separator (3) is connected with an input end of a photoelectric detector (6); an output end of the photoelectric detector is connected with an input end of an amplifying circuit (7); an output end of the amplifying circuit is connected with an input end of a signal processing module (8); and an output end of the signal processing module is connected with a display module (9) and a loudspeaker (10). The system has a simple structure and is easy to realize; and an interference field can be formed by the single optical fiber to detect and position an invading signal.

Description

technical field [0001] The invention relates to a perimeter security system for a single optical fiber and a single optical fiber grating optical cable, and is suitable for the fields of optical fiber sensing, optical fiber communication and the like. Background technique [0002] Modern perimeter security systems are applied to areas with high confidentiality requirements or large-scale perimeter security requirements such as military sites, banks, museums, and airports. It has important practical significance for timely detection and location of intrusion behaviors. [0003] At present, the perimeter security systems based on optical fibers mainly include the following methods: optical power loss method, optical time domain reflection method, Sagnac interference field method, and fiber Bragg grating reflection wavelength shift method. The optical power loss method is to identify the interference signal by real-time monitoring of the optical power change at the receiving en...

AI Technical Summary

Problems solved by technology

The optical power loss method is to identify the interference signal by real-time monitoring of the optical power change at the receiving end of the optical fiber under test. This method has low precision and cannot be accurately located; The principle of reflection, accepting backscattered light, using the relationship between distance and time to detect the position of fiber disturbance, this method measures the signal is very weak, not suitable for dynamic detection, and its cost is high; Sagnac interference field method is to use The two optical fibers in the optical cable form a Sagnac interference field to detect interference signals. This method requires two optical fibers. As the transmission distance increases, the loss of the optical fiber doubles and the accuracy is greatly reduced; the reflection wavelength of the fiber grating is biased. At present, this method is widely used, such as patent 201010147787.6, patent 200810157485.X, patent 200910243040.8, etc. This method needs to accurately measure the change of the reflection wavelength of the fiber grating, and has low precision, complex structure and high cost.

Through in-depth research, we learned that the current perimeter security system based on fiber grating has shortcomings such as weak measurement signal, complicated signal demodulation, and high system cost.

[0004] Patent 200310111529.2 proposes a large-capacity coded fiber grating sensor monitoring system, which needs to code the reflected wavelength of the fiber grating, and the signal processing system of this method has a complex structure and high cost

[0005] Patent 201010237638.9 proposes a monitoring system based on fiber gratings. The device uses fiber gratings to reflect the same wavelength and different reflectivity, and only use power fluctuations to identify and locate intrusion signals. This method has low precision and requires initial settings.

[0006] Patent 02115542.9 proposes an identical fiber grating temperature monitoring and alarm system. The device uses multiple identical fiber gratings, which is complicated to manufacture and cannot be positioned accurately

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