Dual fiber bragg grating strain sensor system

• US 6,829,397 B2
• Filed: 11/15/2002
• Issued: 12/07/2004
• Est. Priority Date: 04/10/2002
• Status: Active Grant

• Current Assignee: National Tsing Hua University
• Original Assignee: National Tsing Hua University
• Inventors: Wang, Li-Karn, Chiang, Yen-Ju, Yang, Chih-Chung
• Primary Examiner(s): Lee, John R.
• Assistant Examiner(s): Hughes, James P.
• Application Number:
  US10/294,731
• Publication Number:
  US 20030194167A1
• Time in Patent Office: 753 Days
• Field of Search: 385/12, 385/13, 385/37, 336/32, 336/35.5, 336/478, 738/00
• US Class Current: 385/12
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35354 Sensor working in reflection
• CPC Class Codes: G01L 1/246 using integrated gratings, e.g. Bragg gratings
• CPC Class Codes: G01L 1/26 Auxiliary measures taken, or devices used, in connection with the measurement of force, e.g. for preventing influence of transverse components of force, for preventing overload

Abstract

The present invention provides a dual fiber Bragg grating strain sensor system, which comprises a broadband light source, a power reading unit, and a sensor unit having a first fiber Bragg grating and a second fiber Bragg grating placed adjacent to each other; wherein the broadband light reaches said sensor unit through said power reading unit, the light that corresponds to the intersection between the spectra of the two FBGs is backreflected and is detected by an optical power meter/detector at the detection port.

Claims

1. A dual fiber Bragg grating strain sensor system, which comprises:

a broadband light source;

a power reading unit; and

a sensor unit having two fiber Bragg gratings (FBGs) including a first fiber Bragg grating written on a first fiber and a second fiber Bragg grating written on a second fiber, the first fiber Bragg grating is placed adjacent to the second fiber Bragg grating,

wherein the broadband light reaches said sensor unit through said power reading unit, and said first fiber Bragg grating and said second fiber Bragg grating reflect light that corresponds to an intersection between a spectra of the two FBGs to said power reading unit, said power reading unit detecting a signal corresponding to the reflected light.

2. The system of claim 1, wherein said first fiber Bragg grating and said second Bragg grating of said sensor unit have a same temperature sensitivity.

3. The system of claim 1, wherein one of said first fiber Bragg grating and said second Bragg grating of said sensor unit is protected by a specific material having a different strain sensitivity.

4. The system of claim 1, wherein both said first fiber Bragg grating and said second Bragg grating of said sensor unit are protected by a specific material, respectively, having a different strain sensitivity.

5. The system of claim 1, wherein said power reading unit further comprises a first fiber coupler, a second fiber coupler, and a detection port;

the broadband light reaches said sensor unit through said first fiber coupler and said second fiber coupler; and

said first fiber Bragg grating and said second fiber Bragg grating reflect the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through said second fiber coupler.

6. The system of claim 1, wherein said power reading unit further comprises an optical circulator and a detection port;

the broadband light reaches said sensor unit through said optical circulator, and said first fiber Bragg grating and said second fiber Bragg grating reflect the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through said optical circulator.

7. A dual fiber Bragg grating strain sensor system, which comprises:

a broadband light source;

a calibration system;

a power reading unit; and

a sensor unit having two fiber Bragg gratings (FBGs) including a first fiber Bragg grating written on a first fiber and a second fiber Bragg grating written on a second fiber, the first fiber Bragg grating is placed adjacent to the second fiber Bragg grating;

wherein the broadband light reaches said sensor unit through said calibration system and said power reading unit, and said first fiber Bragg grating and said second fiber Bragg grating reflect a light that corresponds to an intersection between a spectra of the two FBGs to said power reading unit, said power reading unit detecting a signal corresponding to said reflected light.

8. The system of claim 7, wherein said first fiber Bragg grating and said second Bragg grating of said sensor unit are placed adjacent to each other for having the have a same temperature sensitivity.

9. The system of claim 7, wherein one of said first fiber Bragg grating and said second Bragg grating of said sensor unit is protected by a specific material having different strain sensitivity.

10. The system of claim 7, wherein both said first fiber Bragg grating and said second Bragg grating of said sensor unit are protected by a specific material, respectively, having a different strain sensitivity.

11. The system of claim 7, wherein said power reading unit further comprises a first fiber coupler, a second fiber coupler, and a detection port;

the broadband light reaches said sensor unit through said first fiber coupler and said second fiber coupler, sand said first fiber Bragg grating and said second fiber Bragg grating generate the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through said second fiber coupler.

12. The system of claim 7, wherein said power reading unit further comprises an optical circulator and a detection port;

the broadband light reaches said sensor unit through said optical circulator, and said first fiber Bragg grating and said second fiber Bragg grating reflect the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through said optical circulator.

13. The system of claim 7, wherein said calibration system further comprises a third fiber coupler and a referencing port;

said broadband light reaches said sensor unit through said third fiber coupler and said power reading unit, and said referencing port detecting the light from said broadband light source to monitor the optical power entering the strain sensing system.

14. A dual fiber Bragg grating strain sensor system, which comprises:

a broadband light source;

a power splitter;

a plurality of power reading units; and

a plurality of sensor units, each sensor unit having two fiber Bragg gratings (FBGs) including a first fiber Bragg grating written on a first fiber and a second fiber Bragg grating written on a second fiber, the first fiber Bragg grating is placed adjacent to the second fiber Bragg grating,

wherein the broadband light reaches each said power reading unit through said power splitter and reaches each sensor unit through each said power reading unit, and each said first fiber Bragg grating and each said second fiber Bragg grating reflect a light that corresponds to an intersection between a spectra of the two FBGs to each said power reading unit, said power reading unit detecting a signal corresponding to the reflected light.

15. The system of claim 14, wherein said first fiber Bragg grating and said second Bragg grating of each said sensor unit have a same temperature sensitivity.

16. The system of claim 14, wherein one of said first fiber Bragg grating and said second Bragg grating of said sensor unit is protected by a specific material having a different strain sensitivity.

17. The system of claim 14, wherein both said first fiber Bragg grating and said second Bragg grating of said sensor unit are protected by a specific material, respectively, having a different strain sensitivity.

18. The system of claim 14, wherein each said power reading unit further comprises a first fiber coupler, a second fiber coupler, and a detection port;

wherein the broadband light split by said power splitter reaches each said sensor unit through said first fiber coupler and said second fiber coupler of each said power reading unit, and said first fiber Bragg grating and said second fiber Bragg grating of each said sensor unit generate reflect the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through said second coupler of each said power reading unit.

19. The system of claim 14, wherein each said power reading unit further comprises an optical circulator and a detection port separately;

the broadband light split by said power splitter reaches each said sensor unit through each said optical circulator, and said first fiber Bragg grating and said second fiber Bragg grating of each said sensor unit reflect the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through said optical circulator of each said power reading unit.

20. The system of claim 18, further comprising a referencing port detecting the light from said broadband light source to monitor the optical power entering the strain sensing system.

28. The system of claim 19, further comprising a referencing port detecting the light from said broadband light source to monitor the optical power entering the strain sensing system.

21. A dual fiber Bragg grating strain sensor system, which comprises:

a broadband light source;

a power splitter;

a plurality of calibration systems;

a plurality of power reading units; and

a plurality of sensor units, each sensor unit having two fiber Bragg gratings (FBGs) including a first fiber Bragg grating written on a first fiber and a second fiber Bragg grating written on a second fiber, the first fiber Bragg grating is placed adjacent to the second fiber Bragg grating,

wherein the broadband light split by said power splitter reaches each said sensor unit through each said calibration system and each said power reading unit, and said first fiber Bragg grating and said second fiber Bragg grating of each sensor unit reflect a light that corresponds to an intersection between the a spectra of the two FBGs to each said power reading unit, said power reading unit detecting a signal corresponding to the reflected light.

22. The system of claim 21, wherein said first fiber Bragg grating and said second Bragg grating of each said sensor unit have a same temperature sensitivity.

23. The system of claim 21, wherein one of said first fiber Bragg grating and said second Bragg grating of said sensor unit is protected by a specific material having a different strain sensitivity.

24. The system of claim 21, wherein both said first fiber Bragg grating and said second Bragg grating of said sensor unit are protected by a specific material respectively having a different strain sensitivity.

25. The system of claim 21, wherein each said power reading unit further comprises a first fiber coupler, a second fiber coupler, and a detection port;

the broadband light reaches each said sensor unit through said first fiber coupler and said second fiber coupler of each said power reading unit, and said first fiber Bragg grating and said second fiber Bragg grating of each sensor unit reflect the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through said second fiber coupler of each said power reading unit.

26. The system of claim 21, wherein each said power reading unit further comprises an optical circulator and a detection port separately;

the broadband light reaches each said sensor unit through each said optical circulator, and said first fiber Bragg grating and said second fiber Bragg grating of each said sensor unit reflect the light that corresponds to the intersection between the spectra of the two FBGs to said detection port through each said optical circulator of each said power reading unit.

27. The system of claim 21, wherein each said calibration system further comprises a third fiber coupler and a referencing port separately;

the broadband light reaches each said sensor unit through said third fiber coupler of each said calibration system and said power reading unit, and said referencing port of each said calibration system detecting the light from said broadband light source to monitor the optical power entering each strain sensing system.