Break detection system using optical fibers having unique frequency modulated light

• US 5,013,908 A
• Filed: 11/28/1988
• Issued: 05/07/1991
• Est. Priority Date: 11/28/1988
• Status: Expired due to Fees

• Current Assignee: Kaman Sciences Corp (ITT, Inc.)
• Original Assignee: Kaman Sciences Corp (ITT, Inc.)
• Inventors: Chang, James
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Beck, George
• Application Number:
  US07/276,629
• Time in Patent Office: 890 Days
• Field of Search: 250/227, 250/227.15, 250/227.21, 455/610, 455/612, 455/608, 455/619, 356/73.1, 370/3, 340/555, 340/556, 340/550
• US Class Current: 250/227.15
• CPC Class Codes: G01M 11/083 by using an optical fiber in contact with the device under test [DUT]
• CPC Class Codes: G08B 13/124 with the breaking or disturbance being optically detected, e.g. optical fibers in the perimeter fence
• CPC Class Codes: G08B 13/186 using light guides, e.g. optical fibres

Abstract

A fiber optic detection system comprising an array of fiber optic elements is presented. Each fiber optic element is uniquely encoded using a plurality of discrete ferquencies, digital codes or other encoding techniques. When a break occurs in one or more fiber optic elements, the missing light frequencies or digital codes are sensed, thereby indicating the break. Preferably, the fiber optic elements are arranged in a grid pattern so that precise location of the break can be made.

Claims

1. Fiber optic detection system comprising:

a plurality of fiber optic elements, each element having an input end and an output end;

light inputting means for inputting modulated encoded light to each of said input ends of said fiber optic elements wherein each fiber optic element receives a light code having a unique modulated frequency so that each fiber optic element will be assigned a different pre-selected frequency;

light detecting means for interrogating the output ends of said fiber optic elements wherein the absence of one or more unique light codes indicates a break in at least one of said fiber optic elements.

2. The system of claim 1 wherein:

said light inputting means comprises a light emitting diode coupled to the input ends of each fiber optic element.

3. The system of claim 1 wherein:

said light detecting means comprises photodiode means.

4. The system of claim 1 wherein:

said output ends of all of said plurality of fiber optic elements terminate at photodiode means.

5. The system of claim 3 wherein:

said output ends of all of said plurality of fiber optic elements terminate at said photodiode means.

6. The system of claim 1 including:

fast fourier transformer means for separating said light detected by said photodiode means into said preselected frequencies.

8. The method of claim 1 wherein:

said light inputting step is accomplished using a light emitting diode coupled to the input ends of each fiber optic element.

7. A method of detection using a fiber optic detection system including a plurality of fiber optic elements, each element having an input end and an output end, comprising the steps of:

inputting modulated encoded light to each of said input ends of said fiber optic elements wherein each fiber optic element receives a light code having a unique modulated frequency so that each fiber optic element will be assigned a different pre-selected frequency; and

interrogating the output ends of said fiber optic elements wherein the presence and absence of one or more of said unique light codes is detected and wherein the absence of one or more of said unique light codes indicates a break in at least one of said fiber optic elements.

9. Fiber optic detection system comprising:

a plurality of fiber optic elements, each element having an input end and an output end, said plurality of fiber optic elements being arranged in a grid configuration defining an array of X fiber optic elements and an array of Y fiber optic elements;

light inputting means for inputting modulated encoded light to each of said input ends of said fiber optic elements wherein each fiber optic element in said X array receives a light code having a unique modulated frequency so that each fiber optic element in said X array will be assigned a different pre-selected frequency and each fiber optic element in said Y array receives a light code having a unique modulated frequency so that each fiber optic element in said Y array will be assigned a different pre-selected frequency;

light detecting means for interrogating the output ends of said fiber optic elements in said X and Y arrays wherein the absence of one or more of said unique light codes indicates a break in at least one of said fiber optic elements.

10. The system of claim 9 wherein:

said light inputting means comprises a light emitting diode coupled to the input ends of each fiber optic element.

11. The system of claim 9 wherein:

said preselected frequencies in said X array respectively correspond to said preselected frequencies in said Y array.

12. The system of claim 9 wherein:

said light detecting means comprises first photodiode means for detecting light from said X array and second photodiode means for detecting light from said Y array.

13. The system of claim 9 wherein:

said output ends of all of said X array fiber optic elements terminate at first photodiode means and said output ends of all of said Y array fiber optic elements terminate at second photodiode means.

14. The system of claim 12 wherein:

said output ends of all of said X array fiber optic elements terminate at first photodiode means and said output ends of all of said Y array fiber optic elements terminate at second photodiode means.

15. The system of claim 14 including:

fast fourier transformer means for separating said light detected by said first and second photodiode means into said preselected frequencies.

16. A method of detection using a fiber optic detection system including a plurality of fiber optic elements arranged in a grid configuration defining an array of X fiber optic elements and an array of Y fiber optic elements, each element having an input end and an output end, comprising the steps of:

inputting modulated encoded light to each of said input ends of said fiber optic elements in said X array wherein each fiber optic element in said X array receives a light code having a unique modulated frequency so that each fiber optic element in said X array will be assigned a different pre-selected frequency;

inputting modulated encoded light to each of said input ends of said fiber optic elements in said Y array wherein each fiber optic element in said Y array receives a light code having a unique modulated frequency so that each fiber optic element in said Y array will be assigned a different pre-selected frequency;

interrogating the output ends of said fiber optic elements in said X array wherein the presence and absence of one or more of said unique light codes is detected and wherein the absence of one or more of said unique light codes indicates a break in at least one of said fiber optic elements in said X array; and

interrogating the output ends of said fiber optic elements in said Y array wherein the presence and absence of one or more of said unique light codes is detected and wherein the absence of one or more of said unique light codes indicates a break in at least one of said fiber optic elements in said Y array.

17. The method of claim 16 wherein:

said light inputting step is accomplished using a light emitting diode coupled to the input ends of each fiber optic element.

18. The system of claim 16 wherein:

said preselected frequencies in said X array respectively correspond to said preselected frequencies in said Y array.

19. Fiber optic detection system comprising:

a plurality of fiber optic elements, each element having an input end and an output end, said plurality of fiber optic elements being arranged in a grid configuration defining an array of X fiber optic elements and an array of Y fiber optic elements;

light inputting means for inputting encoded light to each of said input ends of said fiber optic elements wherein each fiber optic element in said X array receives a unique light code and each fiber optic element in said Y array receives a unique light code;

light detecting means for interrogating the output ends of said fiber optic elements in said X and Y arrays wherein the absence of one or more unique light codes indicates a break in at least one of said fiber optic elements said light detecting means comprising first photodiode means for detecting light from said X array and second photodiode means for detecting light from said Y array with said output ends of all of said X array fiber optic elements terminating at said first photodiode means and said output ends of all of said Y array fiber optic elements terminating at said second photodiode means;

said unique light code comprising a unique frequency wherein each fiber optic element in said X array is assigned encoded light having a different preselected frequency and each fiber optic element in said Y array is assigned encoded light having a different preselected frequency; and

fast fourier transformer means for separating said light detected by said first and second photodiode means into said preselected frequencies.