Fiber optic sensor for detecting multiple parameters in a harsh environment

• US 7,336,862 B1
• Filed: 03/22/2007
• Issued: 02/26/2008
• Est. Priority Date: 03/22/2007
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Al-Khalidy, Abdul Rahman Abdallah, Xai, Hua, Young, Clayton Ming, Luo, Huageng, McCarthy, Kevin Thomas, Jiang, Jie, Balasubramaniam, Mahadevan
• Primary Examiner(s): Connelly-Cushwa; Michelle
• Assistant Examiner(s): CHU, CHRIS H
• Application Number:
  US11/689,850
• Time in Patent Office: 341 Days
• Field of Search: None
• US Class Current: 385/12
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• CPC Class Codes: G01D 5/35341 Sensor working in transmission
• CPC Class Codes: G02B 6/021 characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape
• CPC Class Codes: G02B 6/02138 based on illuminating a phase mask
• CPC Class Codes: G02B 6/02147 Point by point fabrication, i.e. grating elements induced one step at a time along the fibre, e.g. by scanning a laser beam, arc discharge scanning G02B6/02133 and G02B6/02142 take precedence
• CPC Class Codes: G02B 6/02185 based on treating the fibre, e.g. post-manufacture treatment, thermal aging, annealing annealing glass fibres C03B37/15
• CPC Class Codes: G02B 6/02209 Mounting means, e.g. adhesives, casings G02B6/02171 and G02B6/02195 take precedence

Abstract

A fiber optic sensor is provided. The fiber optic sensor includes a fiber core having a plurality of Bragg grating elements wherein, the grating elements comprise a periodic or a quasiperiodic modulated microcrystalline and rigid silicon dioxide tetrahedral structure and a cladding disposed about the fiber core.

Claims

1. A fiber optic sensor, comprising:

a fiber core having a plurality of Bragg grating elements wherein, the grating elements comprise a periodic or a quasiperiodic modulated microcrystalline and rigid silicon dioxide tetrahedral structure; and

a cladding disposed about the fiber core.

2. The fiber optic sensor of claim 1, wherein the fiber core comprises a non-photosensitive fused quartz single mode fiber.

3. The fiber optic sensor of claim 1, wherein the sensor is configured to simultaneously detect a plurality of parameters in a high or a dynamic temperature environment.

4. The fiber optic sensor of claim 3, wherein the parameters comprise a dynamic strain, or vibration, or a temperature, or combinations thereof.

5. The fiber optic sensor of claim 3, wherein the sensor is configured to detect the parameters in a temperature environment having a temperature of about 800°

C.

6. The fiber optic sensor of claim 3, wherein the sensor is configured to detect at least one parameter in a gas turbine, or a steam turbine, or a nuclear reactor vessel, or a combustion cell, or aircraft engines, or a coal-fired boiler, or combinations thereof.

7. The fiber optic sensor of claim 1, wherein the periodic or quasiperiodic modulated microcrystalline and rigid silicon dioxide tetrahedral structure is formed through high power femtosecond laser inscribed technique followed by a thermal post-treatment process.

8. The fiber optic sensor of claim 1, wherein the cladding comprises silicon dioxide with a fluorine dopant.

9. The fiber optic sensor of claim 1, wherein the fiber optic sensor comprises first and second claddings and wherein the first cladding comprises a low-percentage fluorine or chlorine dopant and the second cladding comprises a relatively high-percentage fluorine or chlorine dopant.

10. The fiber optic sensor of claim 1, further comprising;

an optical source configured to illuminate the fiber core; and

a detector module configured to detect at least one parameter based upon a reflection spectrum generated from the grating elements.

11. A method of fabricating a fiber optic sensor, comprising:

providing a fiber core;

inscribing a periodic or a quasiperiodic microcrystalline silicon dioxide tetrahedral grating structure on the fiber core; and

converting an under-constrained silicon dioxide structure to an over-constrained silicon dioxide tetrahedral structure.

12. The method of claim 11, further comprising disposing a cladding circumferentially about the fiber core.

13. The method of claim 11, wherein the inscribing step comprises inscribing the periodic or quasiperiodic microcrystalline silicon dioxide tetrahedral grating structure on the fiber core through a high-power pulsed femtosecond laser technique.

14. The method of claim 11, wherein the converting step comprises converting the under-constrained silicon dioxide structure to an over-constrained silicon dioxide tetrahedral structure through a thermal post-treatment process.

15. The method of claim 11, wherein the converting step comprises modification of the fiber material microstructure through isothermal and isochronal processes.

16. The method of claim 15, comprising transforming the under-constrained silicon dioxide structure to a rigid silicon dioxide tetrahedral structure to facilitate operation of the sensor at elevated temperatures and high radiation environments.

17. The method of claim 15, further comprising reducing a grain size distribution and a grain boundary density in the microcrystalline grating structure through the isothermal process.

18. The method of claim 17, wherein reducing the grain size distribution comprises substantially reducing a residual strain in between the fiber core and a cladding interface that substantially prevents light scattering loss from grain boundaries for improving light transmission through the fiber optic sensor.

19. The method of claim 11, comprising substantially eliminating intra-band impurity energy levels of the fiber core for preventing carrier excitation from impurity bands to conduction bands at elevated temperatures and radiation environments.

20. The method of claim 19, further comprising substantially eliminating intra-band structural defect energy levels to prevent the carrier excitation from defect bands to conduction bands at the elevated temperatures and radiation environments.

21. The method of claim 11, wherein the fiber core comprises a non-photosensitive fused quartz single mode fiber.

22. The method of claim 11, comprising inscribing the periodic or quasiperiodic microcrystalline grating structure on the fiber core using fast local melting and quenching processes such that an elasto-optical coefficient of the sensor is independent of a silicon dioxide cluster morphology.

23. The method of claim 11, further comprising packaging the fiber optic sensor with a fiber sensor package material.

24. The method of claim 23, wherein the fiber sensor package materials comprise adhesives and encapsulation materials and fiber protection materials.

25. A method of detecting a plurality of parameters in an environment, comprising:

providing a source of light to a fiber optic sensor having a plurality of grating elements with a periodic or a quasiperiodic modulated microcrystalline and rigid silicon dioxide tetrahedral structure; and

detecting reflection or transmission spectra from the fiber optic sensors.

26. The method of claim 25, further comprising determining the parameters corresponding to changes in the environment based upon the reflection or transmission spectra from the fiber optic sensors.

27. The method of claim 25, comprising detecting at least one parameter in a gas turbine, or a steam turbine, or a nuclear reactor vessel, or an aircraft engine, or a combustion cell, or a coal-fired boiler, or combinations thereof.

28. The method of claim 27, comprising detecting a dynamic strain, or vibration, or a temperature, or combinations thereof.

29. A distributed sensing system for sensing a plurality of parameters in an environment, comprising:

a plurality of sensors disposed on a distributed cable, wherein each of the plurality of sensors comprises;

a fiber core having a periodic or a quasiperiodic modulated microcrystalline and rigid silicon dioxide tetrahedral grating structure; and

a cladding disposed about the fiber core.

30. The distributed sensing system of claim 29, wherein the distributed cable comprises stainless steel, Inconel, or Platinum etc.

31. The distributed sensing system of claim 29, further comprising an optical source configured to illuminate the fiber core of each of the plurality of sensors.

32. The distributed sensing system of claim 31, wherein the illumination source comprises a tunable laser.

33. The distributed sensing system of claim 29, further comprising an optical spectral analyzer configured to measure a parameter based on a wavelength spectrum from the distributed sensor system.