ALL FIBER TOWED ARRAY

• US 20110176811A1
• Filed: 10/19/2010
• Published: 07/21/2011
• Est. Priority Date: 10/20/2009
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: TIETJEN, Byron W.
• Granted Patent: US 9,448,319 B2
• Time in Patent Office: Days
• US Class Current: 398/115
• CPC Class Codes: G01V 1/3808 Seismic data acquisition, e.g. survey design

Abstract

A system and method for an acoustic sensor array of a bundle of N different length optical fiber sensors. A coherent or noncoherent light source is input to each fiber for transmission along the length of the fiber. The light signal is reflected back at the fiber end point, and the resulting reflected light is diverted to an optical receiver so that perturbations of intensity and/or phase may be extracted.

Claims

1. An apparatus for use in an acousto-optical sensor array comprising:

a plurality of at least partially overlapping optical fibers configured to sense an acoustic signal;

a receiver operatively connected to the plurality of optical fibers, and

a processor operatively connected to the receiver and configured to extract the acoustic signal sensed from non-overlapping portions of the optical fibers.

2. The apparatus of claim 1, wherein each optical fiber is configured to receive an optical signal at an input thereof, alter a characteristic of the received optical signal according to the sensed acoustic signal, and output the altered optical signal.

3. The apparatus of claim 1, wherein the processor is configured to extract the acoustic signal by subtracting an output signal from one of the plurality of optical fibers from an output signal of another one of the plurality of optical fibers.

4. The apparatus of claim 1, wherein the plurality of optical fibers comprise differing lengths.

5. The apparatus of claim 4, wherein the processor is operative to subtract the output optical signal of one of the plurality of optical fibers from the output optical signal of another one of the plurality of optical fibers of greater length.

6. The apparatus of claim 5, wherein the plurality of optical fibers comprise consecutively increasing lengths, and the processor is operative to subtract the output optical signal of one of the plurality of optical fibers having a given length from the output optical signal of one of the plurality of optical fibers having the next consecutively greater length.

7. The apparatus of claim 5, wherein the plurality of optical fibers comprise consecutively increasing lengths, and the processor is operative to subtract the output optical signals of a pair of the plurality of optical fibers, the optical fibers comprising the pair separated by a predetermined number of consecutive length optical fibers.

8. The apparatus of claim 7, wherein an operating frequency of the array is altered by changing the predetermined number of consecutive length optical fibers between each of the optical fibers to be subtracted.

9. A method for processing optical signals comprising:

inputting optical signals to plurality of at least partially overlapping optical fibers;

sensing an acoustic signal acting on the plurality of optical fibers;

outputting a plurality of optical signals indicative of the received acoustic signal from each of the plurality of optical fibers, and

processing the sensed acoustic signal by extracting the portion of the acoustic signal sensed by the non-overlapping portions of the optical fibers.

10. The method of claim 9, wherein the step of processing the sensed acoustic signal includes subtracting the output optical signal from one of the plurality of optical fibers from the output optical signal of another one of optical fibers.

11. The method of claim 10, wherein the plurality of optical fibers comprise a plurality of optical fibers having consecutively increasing lengths, and the step of processing the sensed acoustic signal comprises subtracting the output optical signal of one of the plurality of optical fibers from the output optical signal from the optical fiber having the next consecutively greater length.

12. The method of claim 10, wherein the plurality of optical fibers comprise a plurality of optical fibers having consecutively increasing lengths, and the step of processing the sensed acoustic signal comprises subtracting the output optical signals of a pair of the plurality of optical fibers, the optical fibers comprising the pair separated by a predetermined number of consecutive length optical fibers.

13. The method of claim 12, further comprising the step of altering an operating frequency of the array by changing the predetermined number of consecutive length optical fibers between the pair optical fibers which are to be subtracted.

14. An optical sensor array system for use in a towed array sensor comprising:

a towing platform;

an array comprising a plurality of optical fibers operative to sense acoustic signals and cause a change in a characteristic of an optical signal provided to the plurality of optical fibers;

a control system comprising components operative to generate the optical signal and process a received return optical signal, wherein each of the components of the control system are arranged on or within the towing platform.