KR0163243B1 - Invader alarm apparatus by using light fiber - Google Patents

Abstract

The present invention relates to an intruder alarm device using an optical fiber that detects and outputs and alerts a phase change of input light due to vibration or pressure caused by an intruder by using an optical fiber as a sensor. It is very useful not only for general homes and industrial facilities but also for military purposes as it is not detected in advance.

Description

Intruder alarm device using optical fiber

1 is a block diagram of the present invention.

2 is a detailed view of a speckle pattern and a receiving connection at an optical fiber end.

* Explanation of symbols for main parts of the drawings

10: laser diode (LD) drive 11: laser diode (LD) stabilization circuit

12: transmission connection portion 13: optical fiber

14: receiving connection 15: preamplifier

16: shield 17: differential amplifier

20: sensitivity control unit 21: alarm signal processing unit

30: Speckle Pattern

The present invention relates to an intruder alarm device using an optical fiber to bury the optical fiber underground or installed in the fence to recognize the intruder by the change of the signal received when the intruder invades and to alarm through the alarm device.

In the related art, intruder recognition and warning devices used ultrasonic sensors or infrared sensors.

However, when the ultrasonic sensor is used, the monitoring area is limited to within a few meters from the position of the ultrasonic sensor. When the infrared sensor is used, the monitoring area can be recognized only in the monitoring area between the interrupt type light emitting device and the light receiving device. If the weather conditions deteriorate due to the blocking of the light transmission path may be mistaken as an intruder alarm, there was a disadvantage that you need to check and maintain the adjustment of the mutual angle of the light emitting device and the light receiving device from time to time.

In addition, the ultrasonic sensor or the infrared sensor is installed in a state exposed to the outside has the disadvantage that intruders can detect the sensor device in advance.

The present invention was created to supplement and improve the above disadvantages, by using the optical fiber as the intruder detection sensor, the monitoring area can be adjusted from several m to several km or more according to the type and length of the optical fiber as necessary, and monitoring It can be buried underground or installed in a fence to prevent intruders from knowing in advance so that security can be improved.There is no deterioration of weather conditions such as deterioration of weather conditions. Its purpose is to provide an intruder alarm.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings (a laser diode drive 10, a differential amplifier 17, a low pass filter 18, a full wave rectifier 19, and an alarm signal processor 21 are generally used. 1 is a block diagram of the present invention, and the present invention comprises a transmission connection part 12 on one side of an optical fiber 13 that functions as a sensor by embedding or installing in an area to monitor an intruder. The laser diode (LD) drive 10 which starts the laser diode LD of the transmission connection part 12 and produces a coherent light source, and the laser diode LD of the transmission connection part 12 A laser diode stabilization circuit 11 is configured to maintain a stable operation, and the reception connection unit 14 and two inside the reception connection unit 14 which are composed of two photodiodes PD on the other side of the optical fiber 13 are provided. Photo A preamplifier 15 for amplifying the signal from the diode PD and a differential amplifier 17 for differentially amplifying the signal component from the preamplifier 15, and for passing only a predetermined frequency component or less. A full-wave rectifying unit 19 for rectifying the low-pass filter unit 18 to obtain only a positive signal, and a sensitivity adjusting unit 20 for adjusting and setting the reference voltage Vref to detect only an input signal above a predetermined signal level. It consists of an alarm signal processing unit 21 for processing the signal detected by the sensitivity control unit 20 with various alarm devices.

In the above, a part of the optical fiber 13 in contact with the transmitting connection part 12 and a part of the optical fiber 13 in contact with the receiving connection part 14 are located inside the building or a part of the non-monitoring area is exposed to a signal by external stress or vibration. As the shielding portion 16 to prevent the optical fiber from being transmitted to the optical fiber, an external protective agent such as a copper tube that can surround the optical fiber 13 is used.

In the present invention configured as described above, light emitted from the laser diode LD in the transmission connection portion 12 activated by the laser diode (LD) drive 10 is transmitted through an optical fiber (not shown) through a connector (not shown). Incident on one side of 13). Here, some of the light emitted from the laser diode LD is returned to the laser diode LD stabilization circuit 11 through the port diode PD of the transmission connection unit 12 so that the output of the laser diode LD is always one. Keep politics up

On the other hand, the optical fiber 13 is embedded in the basement of the place where you want to monitor the intruder in the depth of several cm to several tens of centimeters depending on the monitoring area conditions or installed in the fence, when the optical fiber 13 is pressed by the vibration or pressure of the intruder The light is reflected by the wall inside the optical fiber 13 to change the phase of the light traveling or going straight, thereby acting as a sensor.

FIG. 2 is a detailed view of the speckle pattern at the end of the optical fiber 13 and the receiving connection. Light incident from the laser diode LD is transmitted to the other side of the optical fiber 13 through the optical fiber 13 installed in the monitoring area. As shown in the figure, due to the interference of light, the speckle pattern 30 formed of light and dark appears.

The number of speckles depends on the number of modes of light advanced, and the intensity of light at each point of the optical fiber 13 differs according to the phase of the mode to form the speckle pattern 30. At this time, if the phase shift Φ of light through the optical fiber 13 is expressed by a formula

Φ = Lβ

(L: length of optical fiber, β is the propagation constant of the mode)

Becomes

The propagation constant β of the mode depends on the size of the optical fiber 13 and the refractive indices of the core and the clad.

If an external stress is applied to the optical fiber 13 to have a small influence on the cross-sectional size and the refractive index of the optical fiber 13, a phase change is generated by affecting the path length of each mode in the optical fiber 13.

That is, when an external stress is applied to the optical fiber 13, the speckle pattern 30 changes.

Therefore, as shown in FIG. 2, when the spatial filter 22 is inserted between the end of the optical fiber 13 and the photodiode PD, which is an optical receiver, the movement of the speckle pattern 30 can be measured.

If the size of the spatial filter 22 is equal to one speckle size, the current of the photodiode PD is changed by the movement of the speckle.

However, it is necessary to appropriately increase the size of the spatial filter 22 in order to increase the signal-to-noise ratio.

In addition, two ports in a receptacle (not shown) connected to a connector (not shown) at the end of the optical fiber 13 coupled to the receiving connection portion 14 without using the spatial filter 22 are shown. Floating the diode PD to an appropriate space and molding may obtain the effect of the spatial filter.

As described above, the light reaching the two photodiodes PD through the space filter 22 or the space of the appropriate size in the receiving connection unit 14 passes through the preamplifier 15 and has a signal having an electrical waveform. These signals are differentially amplified by the differential amplifier 17.

As the output value of the differential amplifier 17 is close to zero, the resistors R1 and R2 in the preamplifier 15 are adjusted to adjust the two input signal levels of the differential amplifier 17 equally.

If an intruder stresses or vibrates the buried or buried optical fiber 13, the speckle pattern 30 reaching the laser diode LD in the receiving connection 14 moves to move the preamplifier ( 15 sends the output of the different signal waveforms to each input of the differential amplifier 17.

That is, when there is no intruder, the output of the differential amplifier 17 is almost zero, but when there is an intruder, a signal of several magnitudes to several tens of dBs appears. The frequency component of this signal is between several tenths of HZ and several KHZ.

This frequency band varies depending on the conditions of the region where the optical fiber 13 is installed. The frequency is low in the soft ground and high in the hard material such as concrete.

Accordingly, the output signal of the differential amplifier 17 is passed through the low pass filter 18 having a cutoff frequency of several KHz to remove the noise components and then sent to the full wave rectifier 19 to obtain a positive signal.

The sensitivity control unit 20 is a reference signal (Vref) which is an input of the sensitivity control unit 20 according to the installation state and the object to be invaded, such as the component and the depth of embedding in the area where the optical fiber 13 is buried or buried Can be set as a resistor (R3), and when the signal of a level higher than this reference signal comes out of the output of the full wave rectifying unit 19 and enters the sensitivity adjusting unit 20, there is an intruder in the alarm signal processing unit 21. Signal is transmitted.

The alarm signal processing unit 21 may be configured as a buzzer or a lamp for notifying an intrusion state through a logic circuit, or may send a signal to a computer through an interface circuit, and also configure a microprocessor to process an alarm state.

The present invention configured and acting as described above can be used for various purposes not only for protecting general homes or industrial facilities, but also for military purposes, and has a feature of distinguishing a target or type of invasion by defining a reference output signal. Effective inventions can be made.

Claims (5)

An optical fiber, a light generating device for generating a light source, an optical receiving device for receiving an optical signal outputted from the light generating device and transmitted through the optical fiber, and a warning device for warning when intruder intrusion information is input by electrical processing of the optical signal. In the intruder warning device using an optical fiber, the laser diode (LD) configured on one side of the optical fiber 13 to output the light and the light emitted from the laser diode (LD) is partially returned to output the laser diode (LD). A transmission connection part 12 formed of a photodiode (PD) which serves to maintain a constant; A laser diode drive (10) for activating the laser diode (LD) to generate a coherent light source; A laser diode stabilization circuit (11) for maintaining a stable operation of the laser diode (LD); Receiving connection portion 14 configured on the other side of the optical fiber 13, consisting of two photodiodes (PD) for receiving the light propagated along the optical fiber 13 is output from the laser diode (LD) of the transmission connection portion 12 Wow; A preamplifier 15 which amplifies the signals output from the two photodiodes PD of the reception connection unit 14; A differential amplifier 17 for differentially amplifying the signal components output from the preamplifier 15; A low pass filter unit 18 for passing only a predetermined frequency component or less; A full-wave rectifying unit 19 for rectifying the signal to obtain only a positive signal; A sensitivity adjusting unit 20 for detecting only an input signal having a predetermined signal level or more; An alarm signal processor 20 for alarming the sensed signal from the sensitivity controller 20; Optical fiber, characterized in that consisting of a shielding portion 16 that serves to shield the external stress signal from a portion where the transmission connection portion 12 and the reception connection portion 14 and the optical fiber 13, the inside of the building or a non-monitoring area. Intruder alarm system using. The intruder warning device according to claim 1, wherein the reception connection unit (14) recognizes the intruder information signal by a change in the speckle pattern (30) appearing at the end of the optical fiber (13). 3. Appropriate distance according to claim 1 or 2, wherein a space filter 22 of an appropriate size is used between the end of the optical fiber 13 and the photodiode of the receiving connection to increase the signal-to-noise ratio, or without using the space filter. And molding two photodiodes PD in a receptacle (not shown) to adjust the light receiving angle of the photodiode PD to perform the function of the spatial filter 22. Intruder alarm system using an optical fiber, characterized in that the configuration. The preamplifier 15 adjusts the level of signal components from the two photodiodes PD in the receiving connection unit 14 so that the output signal of the differential amplifier 17 is in steady state. Nearly zero, when the end speckle pattern 30 of the optical fiber 13 is moved and the photodiode PD receives different patterns, the output signal of the differential amplifier 17 receives a signal of a predetermined level or more. Intruder alarm system using an optical fiber, characterized in that the circuit is composed of a resistor (R1) (R2) to have. The reference voltage (Vref) of claim 1, wherein the sensitivity adjusting unit 20 sends only a signal of a predetermined level or more to the output according to the embedding or laying state of the optical fiber 13 embedded or buried or the sensitivity of the optical fiber 13. Intruder alarm system using an optical fiber, characterized in that the control circuit is composed of a resistor (R3) to adjust the level.