Atmospheric infrasonic sensing from an array of aircraft

• US 10,365,089 B1
• Filed: 08/04/2017
• Issued: 07/30/2019
• Est. Priority Date: 08/04/2017
• Status: Active Grant

• 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: Titovich, Alexey
• Primary Examiner(s): Rahll, Jerry
• Application Number:
  US15/669,050
• Time in Patent Office: 725 Days
• Field of Search: None
• CPC Class Codes: B64C 39/024 of the remote controlled vehicle type, i.e. RPV
• CPC Class Codes: G01B 11/18 using photoelastic elements
• 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
• CPC Class Codes: G01L 1/247 using distributed sensing elements, e.g. microcapsules along a single optical fibre G01L1/242
• CPC Class Codes: G01L 11/025 using a pressure-sensitive optical fibre
• CPC Class Codes: G01V 1/01 Measuring or predicting earthquakes
• CPC Class Codes: G01V 1/18 Receiving elements, e.g. seismometer, geophone or torque detectors, for localised single point measurements
• CPC Class Codes: G01V 7/16 specially adapted for use on moving platforms, e.g. ship, aircraft
• CPC Class Codes: G01W 1/08 Adaptations of balloons, missiles, or aircraft for meteorological purposes; Radiosondes transmission of measurements G01D; transmitting circuits H04B; balloons in general B64B; aeroplanes in general B64D; missiles in general F42B15/00
• CPC Class Codes: G01W 2001/003 Clear air turbulence detection or forecasting, e.g. for aircrafts
• CPC Class Codes: G06V 20/182 Network patterns, e.g. roads or rivers

Abstract

Exemplary practice of the present invention provides an air vehicle and at least one interferometric double-path fiber optic sensor connected with the air vehicle. Each fiber optic sensor includes a pair of optical fibers, viz., an optical sensing fiber and an optical reference fiber, in a parallel and propinquus relationship. The paired optical fibers of each fiber optic sensor are attached to the air vehicle either (i) circumferentially around the fuselage or (ii) lengthwise along the fuselage or (iii) span-wise along the wings and across the fuselage, and are configured whereby the sensing fiber is exposed to the atmosphere and the reference fiber is not. Each fiber optic sensor senses atmospheric infrasound but does not sense atmospheric wind noise, which is negated by incoherency associated with design lengthiness of the optical fiber pair. Noise and strain due to temperature, vibration, and propulsion are neutralized via interferometric common mode rejection.

Claims

1. A system for sensing infrasound, the system comprising plural vehicles capable of flight, plural fiber optic sensors, and a computer, each said vehicle having at least one said fiber optic sensor coupled with said vehicle, each said fiber optic sensor including an optical fiber pair consisting of a sensing optical fiber and a reference optical fiber that are proximate and substantially parallel to each other and that respectively represent two different beam paths, said optical fiber pair attached to said vehicle in the atmosphere whereby infrasound in the atmosphere measurably affects said sensing optical fiber and negligibly affects said reference optical fiber, said computer receiving and processing contemporaneous sensory signals transmitted from said plural fiber optic sensors that are coupled with said plural vehicles in the atmosphere, wherein said processing of said contemporaneous sensory signals includes generation of a three-dimensional spatiotemporal representation of an infrasonic field in the atmosphere.

2. The system for sensing infrasound as recited in claim 1, wherein said optical fiber pair is characterized by an optical fiber length, and wherein said optical fiber length is sufficiently long that wind in the atmosphere is rendered at least substantially incoherent with respect to said fiber optic sensor.

3. The system for sensing infrasound as recited in claim 1, wherein said optical fiber pair is configured so that said fiber optic sensor effectuates common mode rejection of noise and/or strain associated with at least one factor selected from the group consisting of temperature, structure of said vehicle, and propulsion of said vehicle.

4. The system for sensing infrasound as recited in claim 3, wherein said optical fiber pair is characterized by an optical fiber length, and wherein said optical fiber length is sufficiently long that wind in the atmosphere is rendered at least substantially incoherent with respect to said fiber optic sensor.

5. The system for sensing infrasound as recited in claim 1, wherein for at least one said fiber optic sensor coupled with at least one said vehicle:

said sensing optical fiber is attached to said vehicle on the outside of said vehicle;

said reference optical fiber is attached to said vehicle on the inside of said vehicle.

6. The system for sensing infrasound as recited in claim 1, wherein for at least one said fiber optic sensor coupled with at least one said vehicle:

said sensing optical fiber is attached to said vehicle on the outside of said vehicle;

said reference optical fiber is attached to said vehicle on the outside of said fuselage and is at least substantially encompassed by a tube that hermetically seals said reference fiber.

7. The system for sensing infrasound as recited in claim 1, wherein for at least one said fiber optic sensor coupled with at least one said vehicle:

said sensing optical fiber is attached to said vehicle on the outside of said vehicle and is at least substantially encompassed by a perforated tube so as to be at least substantially exposed to infrasound in the atmosphere;

said reference optical fiber is attached to said vehicle on the outside of said vehicle and is at least substantially encompassed by a solid tube so as to be at least substantially insulated from infrasound in the atmosphere.

8. The system for sensing infrasound as recited in claim 1, wherein:

at least one said vehicle has a fuselage;

said fuselage is characterized by a fuselage circumference;

in at least one said fiber optic sensor coupled with at least one said vehicle having said fuselage characterized by said fuselage circumference, said optical fiber pair is circumferentially attached to said vehicle around said fuselage circumference.

9. The system for sensing infrasound as recited in claim 1, wherein:

at least one said vehicle has a fuselage;

said fuselage is characterized by a fuselage length;

in at least one said fiber optic sensor coupled with at least one said vehicle having said fuselage characterized by said fuselage length, said optical fiber pair is longitudinally attached to said vehicle along at least substantially the entire said fuselage length.

10. The system for sensing infrasound as recited in claim 1, wherein:

at least one said vehicle has a fuselage and a pair of wings projecting on opposite sides from said fuselage;

said pair of wings is characterized by a wingspan;

in at least one said fiber optic sensor coupled with at least one said vehicle having said fuselage and said pair of wings characterized by said wingspan, said optical fiber pair is attached to said vehicle across said fuselage and along at least substantially the entire said wingspan.

11. The system for sensing infrasound as recited in claim 1, wherein:

at least one said vehicle has a fuselage;

said fuselage is characterized by a fuselage circumference and a fuselage length;

at least a first said fiber optic sensor and at least a second said fiber optic sensor are coupled with each of at least one said vehicle having said fuselage characterized by said fuselage circumference and said fuselage length;

in the first said fiber optic sensor, said optical fiber pair is circumferentially attached to said vehicle around said fuselage circumference;

in the second said fiber optic sensor, said optical fiber pair is longitudinally attached to said vehicle along at least substantially the entire said fuselage length.

12. The system for sensing infrasound as recited in claim 1, wherein:

at least one said vehicle has a fuselage and a pair of wings projecting on opposite sides from said fuselage;

said fuselage is characterized by a fuselage circumference;

said pair of wings is characterized by a wingspan;

at least a first said fiber optic sensor and at least a second said fiber optic sensor are coupled with each of at least one said vehicle having said fuselage characterized by said fuselage circumference and said pair of wings characterized by said wingspan;

in the first said fiber optic sensor, said optical fiber pair is circumferentially attached to said vehicle around said fuselage circumference;

in the second said fiber optic sensor, said optical fiber pair is attached to said vehicle across said fuselage and along at least substantially the entire said wingspan.

13. The system for sensing infrasound as recited in claim 4, wherein:

at least one said vehicle has a fuselage and a pair of wings projecting on opposite sides from said fuselage;

said fuselage is characterized by a fuselage length;

said pair of wings is characterized by a wingspan;

at least a first said fiber optic sensor and at least a second said fiber optic sensor are coupled with each of at least one said vehicle having said fuselage characterized by said fuselage length and said pair of wings characterized by said wingspan;

in the first said fiber optic sensor, said optical fiber pair is longitudinally attached to said vehicle along at least substantially the entire said fuselage length;

in the second said fiber optic sensor, said optical fiber pair is attached to said vehicle across said fuselage and along at least substantially the entire said wingspan.

14. The system for sensing infrasound as recited in claim 1, wherein:

at least one said vehicle has a fuselage and a pair of wings projecting on opposite sides from said fuselage;

said fuselage is characterized by a fuselage circumference and a fuselage length;

said pair of wings is characterized by a wingspan;

at least a first said fiber optic sensor, at least a second said fiber optic sensor, and at least a third said fiber optic sensor are coupled with each of at least one said vehicle having said fuselage characterized by said fuselage circumference and said fuselage length and said pair of wings characterized by said wingspan;

in the first said fiber optic sensor, said fiber optic fiber pair is circumferentially attached to said vehicle around said fuselage circumference;

in the second said fiber optic sensor, said optical fiber pair is longitudinally attached to said vehicle along at least substantially the entire said fuselage length;

in the third said fiber optic sensor, said optical fiber pair is attached to said vehicle across said fuselage and along at least substantially the entire said wingspan.

15. The system for sensing infrasound as recited in claim 1, wherein:

each said vehicle has a fuselage and a pair of wings projecting on opposite sides from said fuselage;

said fuselage is characterized by a fuselage circumference and a fuselage length;

said pair of wings is characterized by a wingspan;

for each said fiber optic sensor, said attachment of said optical fiber pair to said vehicle is selected from the group consisting of circumferential attachment, longitudinal attachment, and span-wise attachment;

according to said circumferential attachment, said optical fiber pair is circumferentially attached to said vehicle around said fuselage circumference;

according to said longitudinal attachment, said optical fiber pair is longitudinally attached to said vehicle along at least substantially the entire said fuselage length;

according to said span-wise attachment, said optical fiber pair is attached to said vehicle across said fuselage and along at least substantially the entire said wingspan.

16. The system for sensing infrasound as recited in claim 15, wherein:

said optical fiber pair is characterized by an optical fiber length;

said optical fiber length is sufficiently long that wind in the atmosphere is rendered at least substantially incoherent with respect to said infrasound sensor;

said optical fiber pair is configured so that said fiber optic sensor effectuates common mode rejection of noise and/or strain associated with at least one factor selected from the group consisting of temperature, structure of said vehicle, and propulsion of said vehicle.

17. The system for sensing infrasound as recited in claim 15, wherein for each said fiber optic sensor:

said sensing optical fiber is attached to said vehicle on the outside of said vehicle;

said reference optical fiber is attached to said vehicle on either the outside of said vehicle or the inside of said vehicle;

said sensing optical fiber is either at least substantially un-encompassed by a tube or at least substantially encompassed by a perforated tube, said sensing optical fiber being at least substantially exposed to infrasound in the atmosphere;

if said reference optical fiber is attached to said vehicle on the outside of said vehicle, then said reference optical fiber is at least substantially encompassed by a tube that hermetically seals said reference fiber.

18. The system for sensing infrasound as recited in claim 17, wherein:

said optical fiber pair is characterized by an optical fiber length;

said optical fiber length is sufficiently long that wind in the atmosphere is rendered at least substantially incoherent with respect to said fiber optic sensor;

said optical fiber pair is configured so that said fiber optic sensor effectuates common mode rejection of noise and/or strain associated with at least one factor selected from the group consisting of temperature, structure of said vehicle, and propulsion of said vehicle.

19. A method for sensing infrasound, the method comprising:

providing a plurality of vehicles capable of flight;

coupling at least one fiber optic sensor with each said vehicle, each said fiber optic sensor including an optical fiber pair consisting of a sensing optical fiber and a reference optical fiber that are proximate and substantially parallel to each other, said sensing optical fiber and said reference optical fiber respectively representing two different beam paths, said coupling including attaching said optical fiber pair to said vehicle whereby infrasound in the atmosphere measurably affects said sensing optical fiber and negligibly affects said reference optical fiber; and

using said at least one fiber optic sensor coupled with each said vehicle, sensing infrasound in the atmosphere while each said vehicle is in flight;

wherein;

each said vehicle has a fuselage and a pair of wings projecting on opposite sides from said fuselage;

said fuselage is characterized by a fuselage circumference and a fuselage length;

said pair of wings is characterized by a wingspan;

for each said fiber optic sensor, said attachment of said optical fiber pair to said vehicle is selected from the group consisting of circumferential attachment, longitudinal attachment, and span-wise attachment;

according to said circumferential attachment said optical fiber pair is circumferentially attached to said vehicle around said fuselage circumference;

according to said longitudinal attachment said optical fiber pair is longitudinally attached to said vehicle along at least substantially the entire said fuselage length;

according to said span-wise attachment said optical fiber pair is attached to said vehicle across said fuselage and along at least substantially the entire said wingspan;

the method further comprises receiving signals from each said fiber optic sensor and generating a spatiotemporal representation of infrasound in the atmosphere based on said signals received, wherein the receiving of said signals and the generating of said spatiotemporal representation are performed using a computer.