Low flow-noise conformal fiber optic hydrophone

• US 5,140,559 A
• Filed: 02/21/1991
• Issued: 08/18/1992
• Est. Priority Date: 02/21/1991
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Fisher, Stanley A.
• Primary Examiner(s): ELDRED, JOHN W
• Application Number:
  US07/658,496
• Time in Patent Office: 544 Days
• Field of Search: 367/149, 250/227.14, 250/227.28, 250/227.19, 356/345, 356/357, 350/96.29
• US Class Current: 367/149
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125

Abstract

A fiber-optic hydrophone having a pair of jacketed fiber optic windings fed in a concentric planar spiral configuration in a layer of polyurethane is provided. One of the fiber optic windings has a fiber with a bonded acoustically sensitive jacket thereby increasing its sensitivity to acoustic energy. The second fiber optic winding, the reference winding, has a unbonded jacket enclosing the fiber resulting in reduced sensitivity to acoustic energy. Sensitivity to vibrational energy; however, is not reduced. The combining of signals from the pair of fibers provides a vibration-canceled acoustic signal.

Claims

1. A vibration-canceling fiber optic hydrophone comprising:

a. a sensing coil formed with an optical fiber having a jacket which is acoustically sensitive bonded to the optical fiber;

b. a reference coil formed with an optical fiber having a protective jacket that is not bonded to the optical fiber;

c. a planar acoustic sensing disk formed by forming said sensing coil and reference coil into a planar concentric spiral;

d. an acoustically transparent material encapsulating said planar acoustic sensing disk thereby forming a sealed, compliant planar layer;

e. a coherent light source connected to and transmitting light to said reference optical fiber and to said sensing optical fiber; and

f. an opto-electronic unit connected to and receiving transmitted light from said reference and sensing optical fibers suitable for determining phase shift differences between said sensing and reference optical fibers.

2. A vibration-canceling fiber optic hydrophone comprising:

a. means for providing coherent light;

b. means for receiving coherent light, said receiving means having optical characteristics which vary when subjected to acoustic impingement;

c. means for detecting vibration signals, said detecting means being insulated from acoustic impingement;

d. means for processing output signals from said receiving means and said detecting means; and

e. means for demodulating processed output signals to obtain a low vibration noise acoustic signal.

3. A vibration-canceling fiber optic hydrophone as in claim 2 wherein said means for providing coherent light is a laser light source.

4. A vibration-canceling fiber optic hydrophone as in claim 3 wherein said laser light source emits light at a wavelength of 800 nM.

5. A vibration-canceling fiber optic hydrophone as in claim 3 wherein said laser light source emits light at a wavelength of 1300 nM.

6. A vibration-canceling fiber optic hydrophone as in claim 2 wherein said means for receiving coherent light is a fiber optic coil having an acoustically sensitive jacket continuously bonded to the fiber optic coil and wound on a compliant sheet of acoustically transparent material.

7. A vibration-canceling fiber optic hydrophone as in claim 6 wherein said acoustically transparent material is polyurethane.

8. A vibration-canceling fiber optic hydrophone as in claim 2 wherein said means for detecting vibration signals comprises a fiber optic coil having a jacket that is not bonded to the fiber optic coil and wound on a compliant sheet of acoustically transparent material.

9. A vibration-canceling fiber optic hydrophone as in claim 8 wherein said acoustically transparent material is polyurethane.

10. A vibration-canceling fiber optic hydrophone as in claim 2 wherein said means for receiving coherent light and said means for detecting vibration signals each comprise a fiber optic coil with the coils collocated on a compliant;

sheet and form concentric windings.

11. A vibration-canceling fiber optic hydrophone as in claim 2 wherein said means for processing output signals is an optical-electronic processor having an optical phase detector, photo-voltage converter, and preamplifier.

12. A vibration-canceling fiber optic hydrophone as in claim 2 wherein said means for demodulating is a device using synthetic heterodyne demodulation.