FIBER BRAGG GRATING SYSTEMS AND METHODS FOR MOISTURE DETECTION

• US 20140102190A1
• Filed: 10/15/2013
• Published: 04/17/2014
• Est. Priority Date: 10/15/2012
• Status: Active Grant

• Current Assignee: University of Houston (University of Houston System)
• Original Assignee: University of Houston (University of Houston System)
• Inventors: Song, Gangbing, Ho, Siu Chun Michael, Liang, Ren
• Granted Patent: US 9,222,877 B2
• Time in Patent Office: Days
• US Class Current: 73/335.01
• CPC Class Codes: G01M 3/047 with photo-electrical detection means, e.g. using optical fibres
• CPC Class Codes: G01N 21/17 Systems in which incident light is modified in accordance with the properties of the material investigated where the material investigated is optically excited causing a change in wavelength of the incident light G01N21/63
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

A fiber Bragg grating (FBG) sensor for detecting moisture may include a sensor housing, FBG cable, water-swellable bead(s), and retaining mechanism. The housing secures the FBG cable and water-swellable bead. The retaining mechanism, such as one or more wire(s), placed adjacent to the FBG cable may be utilized to minimize lateral displacement of the water-swellable bead(s). The water-swellable bead(s) may swell as they absorb water, thereby causing the FBG to be strained to allow the detection of liquid moisture.

Claims

1. An apparatus for detecting moisture, the apparatus comprising:

a moisture sensor that comprises

a water swellable bead that swells when absorbing a liquid;

a sensor housing for the water swellable bead, wherein the sensor housing provides a top portion and a bottom portion, and the sensor housing provides at least one opening;

a fiber Bragg grating (FBG) cable, wherein the FBG cable is positioned in the sensor housing in contact with the water swellable bead; and

a retaining mechanism securing the water swellable bead in the sensor housing.

2. The apparatus of claim 1, wherein the water swellable bead is a superabsorbent polymer.

3. The apparatus of claim 2, wherein the superabsorbent polymer is sodium polyacrylate.

4. The apparatus of claim 1, wherein the water swellable bead is surrounded by a water permeable packet.

5. The apparatus of claim 1, wherein the retaining mechanism is superelastic wires, wherein the superelastic wires restrict lateral movement of the water swellable bead.

6. The apparatus of claim 5, wherein the superelastic wires are shape memory alloy wires.

7. The apparatus of claim 1, wherein the FBG cable is aligned through a longitudinal center of the sensor housing.

8. The apparatus of claim 1, wherein the FBG cable is placed in a furcation tube.

9. The apparatus of claim 1, wherein the FBG cable is fastened to conduits of the sensor housing.

10. The apparatus of claim 1, further comprising a temperature sensor.

11. The apparatus of claim 1, wherein the moisture sensor is operable after exposure to repeated load cycling.

12. The apparatus of claim 1, wherein the moisture sensor is operable after exposure to flooding conditions.

13. The apparatus of claim 1, wherein the moisture sensor is multiplexed with one or more additional moisture sensors, and each of the additional moisture sensors comprise the same components as the moisture sensor of claim 1.

14. A method for forming a sensor for detecting moisture, the method comprising:

fabricating a sensor housing, wherein the sensor housing provides a top portion and a bottom portion, and the sensor housing provides at least one opening;

placing a water swellable bead in the bottom portion of the sensor housing, wherein the water swellable bead swells when absorbing a liquid;

placing a fiber Bragg grating (FBG) cable in the sensor housing, wherein the FBG cable is in contact with the water swellable bead;

securing the water swellable bead in the sensor housing with a retaining mechanism; and

securing the top portion to the bottom portion of the sensor housing.

15. The method of claim 14, wherein the water swellable bead is a superabsorbent polymer.

16. The method of claim 15, wherein the superabsorbent polymer is sodium polyacrylate.

17. The method of claim 14, further comprising surrounding the bead with a water permeable packet.

18. The method of claim 14, wherein the retaining mechanism is superelastic wires, wherein the superelastic wires restrict lateral movement of the water swellable bead.

19. The method of claim 18, wherein the superelastic wires are shape memory alloy wires.

20. The method of claim 14, wherein the FBG cable is aligned through a longitudinal center of the sensor housing.

21. The method of claim 14, wherein the FBG cable is fastened to conduits of the sensor housing.

22. The method of claim 21, wherein the FBG cable is prestrained when fastened to the sensor housing.

23. The method of claim 14, further comprising placing a temperature sensor in the sensor housing.

24. The method of claim 14, wherein the sensor is operable after exposure to repeated load cycling.

25. The method of claim 14, wherein the sensor is operable after exposure to flooding conditions.

26. The method of claim 14, further comprising:

repeating the steps recited in claim 14 to form one or more additional moisture sensors; and

multiplexing the sensor with the one or more additional moisture sensors.