Method and device for intrusion detection using an optical continuity system

• US 20060044136A1
• Filed: 08/26/2004
• Published: 03/02/2006
• Est. Priority Date: 08/26/2004
• Status: Active Grant

• Current Assignee: DSFE Security Systems International Incorporated
• Original Assignee: DSFE Security Systems International Incorporated
• Inventors: Kowal, Sandra E., Williams, Edwin L., Lambrecht, Frank E.
• Granted Patent: US 7,135,970 B2
• Time in Patent Office: Days
• US Class Current: 340/555
• CPC Class Codes: G08B 13/186 using light guides, e.g. optical fibres

Abstract

A fiber optic based security system is disposed on or in a structure such as a wall, roof, floor, ceiling, container, and/or ground. The security system contains an optical cable having first and second ends and an interface unit connected to both ends of the optical cable. The interface unit generates a specific light signal injected into the first end. The interface unit receives the specific light signal from the second end after the specific light signal propagates through the optical cable. The interface unit then determines if the specific light signal received falls within a given threshold and outputs an alarming signal indicating if the specific light signal received falls outside of the given threshold. An alarm system receives the alarming signal from the interface unit. The alarm system is activated if the interface unit indicates that the specific light signal falls outside of the given threshold.

Claims

1. A method of operating a security system, which comprises the steps of:

laying an optical cable throughout a structure to be protected;

generating a specific light signal and injecting the specific light signal into a first end of the optical cable;

receiving the specific light signal from a second end of the optical cable after the specific light signal propagates through the optical cable;

determining if the specific light signal received falls within a given threshold; and

setting an alarm condition if the specific light signal received falls outside of the given threshold.

2. The method according to claim 1, which further comprises the steps of:

generating a specific first electrical signal which is converted into the specific light signal by a light-emitting device; and

converting the specific light signal received from the second end of the optical fiber into a second electrical signal using a light-receiving device.

3. The method according to claim 2, which further comprises generating the specific first electrical signal as a random or pseudorandom signal.

4. The method according to claim 3, which further comprises the steps of:

comparing a difference between the received and transmitted signals to the given threshold which includes a high threshold value and a low threshold value;

generating an alarming signal if the amplified signal is not between the high threshold value and the low threshold value; and

setting the alarm condition for activating an alarm system.

5. The method according to claim 4, which further comprises the steps of:

transmitting the alarming signal wirelessly; and

selecting the given threshold to have at least one parameter selected from the group consisting of amplitude, frequency, phase, pulse width and pulse pattern.

6. The method according to claim 2, which further comprises generating the specific first electrical signal by changing one of its amplitude, frequency, phase, pulse width and pulse pattern between consecutive ones of specific first electrical signals.

7. The method according to claim 6, which further comprises using a controller selected from the group consisting of microprocessors, microcomputers, microcontrollers and application specific integrated circuits for generating the specific first electrical signal.

8. The method according to claim 2, which further comprises:

providing a light-emitting diode, laser diode or other device capable of converting an electrical signal to a light signal as the light-emitting device; and

selecting the light-receiving device from the group consisting of photo-detectors and phototransistors.

9. A security system, comprising:

an optical cable having ends including a first end and a second end;

an interface unit connected to both of said first and second ends of said optical cable, said interface unit generating a specific light signal injected into said first end of said optical cable, said interface unit receiving the specific light signal from said second end of said optical cable after the specific light signal propagates through said optical cable, said interface unit determining if the specific light signal received falls within a given threshold and outputs an alarming signal indicating if the specific light signal received falls outside of the given threshold; and

an alarm system receiving the alarming signal from said interface unit, said alarm system being activated if the alarming signal indicates that the specific light signal falls outside of the given threshold.

10. The security system according to claim 9, wherein said interface unit includes:

a controller generating a first specific electrical signal;

a light-emitting device connected between said controller and said first end of said optical cable, said light-emitting device receiving and converting the first specific electrical signal into the specific light signal injected into said first end of said optical cable; and

a light-receiving device connected between said second end of said optical cable and said controller, said light-receiving device receiving and converting the specific optical signal into a second electrical signal and forwards the second electrical signal to said controller for evaluation.

11. The security system according to claim 10, wherein:

said light-receiving device is selected from the group consisting of photo-detectors and phototransistors; and

said light-emitting device is a light-emitting diode, laser diode or other device capable of converting an electrical signal to a light signal.

12. The security system according to claim 10, wherein:

said alarm system has a receiver; and

said interface unit has a transmitter for transmitting the alarming signal to said receiver of said alarm system.

13. The security system according to claim 10, wherein said interface unit has an alarm interface connected between said controller and said alarm system or integrated in said controller.

14. The security system according to claim 11, wherein said controller evaluates the second electrical signal against the given threshold and the given threshold has at least one parameter selected from the group consisting of amplitude, frequency, phase, pulse width and pulse pattern.

15. The security system according to claim 14, wherein the given threshold includes a high threshold value and a low threshold value and an alarm function is inactive when the second electrical signal is between said high threshold value and said low threshold value.

16. The security system according to claim 10, wherein said controller is selected from the group consisting of microprocessors, microcomputers, microcontrollers, and application specific integrated circuits.

17. The security system according to claim 10, wherein said controller is programmed to form the first specific electrical signal.

18. In combination with a structure to be protected, a security system disposed on or in the structure, the security system comprising:

an optical cable having ends including a first end and a second end;

an interface unit connected to both of said first and second ends of said optical cable, said interface unit generating a specific light signal injected into said first end of said optical cable, said interface unit receiving the specific light signal from said second end of said optical cable after the specific light signal propagates through said optical cable, said interface unit determining if the specific light signal received falls within a given threshold and outputs an alarming signal indicating if the specific light signal received falls outside of the given threshold; and

an alarm system receiving the alarming signal from said interface unit, said alarm system being activated if the alarming signal indicates that the specific light signals falls outside of the given threshold.

19. The security system according to claim 18, wherein said interface unit includes:

a controller generating a first specific electrical signal;

a light-emitting device connected between said controller and said first end of said optical cable, said light-emitting device receiving and converting the first specific electrical signal into the specific light signal injected into said first end of said optical cable; and

a light-receiving device connected between said second end of said optical cable and said controller, said light-receiving device receiving and converting the specific optical signal into a second electrical signal and forwards the second electrical signal to said controller for evaluation.

20. The security system according to claim 19, wherein:

said light-receiving device is selected from the group consisting of photo detectors and phototransistors; and

said light-emitting device is a light-emitting diode, laser diode or other device capable of converting an electrical signal to a light signal.

21. The security system according to claim 19, wherein:

said alarm system has a receiver; and

said interface unit has a transmitter for transmitting the alarming signal to said receiver of said alarm system.

22. The security system according to claim 19, wherein said interface unit has an alarm interface connected to or part of said controller.

23. The security system according to claim 19, wherein said controller evaluates the second electrical signal against the given threshold and the given threshold has a parameter selected from the group consisting of amplitude, frequency, phase, pulse width, and pulse pattern.

24. The security system according to claim 23, wherein the given threshold includes a high threshold value and a low threshold value and an alarm function is inactive when the second electrical signal is between said high threshold value and said low threshold value.

25. The security system according to claim 19, wherein said controller is selected from the group consisting of microprocessors, microcomputers, microcontrollers and application specific integrated circuits.

26. The security system according to claim 19, wherein said controller uses programming to form the first specific electrical signal.

27. The security system according to claim 26, wherein said controller continuously varies the first specific electrical signal.

28. The security system according to claim 18, wherein the structure is selected from the group consisting of walls, roofs, floors, ceilings, containers, and ground.