USA As Represented by Secretary of the Navy

Clay K Kirkendall

Brandon F Redding

Allen R Davis

Geoffrey A Cranch

Anthony Dandridge

Matthew J Murray

Multiplexed fiber optic sensors are able to monitor a multitude of sensor positions along an optical fiber from a single interrogation point. A long-standing goal is to increase the length of fiber and the number of multiplexed sensors without significantly compromising performance or increasing the size, weight, power and cost of the fiber and interrogation system. A technique is provided for performing extremely long-range, multiplexed fiber optic strain sensing in an efficient manner. This technique utilizes a serial optical frequency comb based interrogation system to probe an array of sensors placed along a single optical fiber.

Multiplexed long-range fiber optic sensing

Methods and apparatuses for quantitatively measuring strain in an optical fiber. An optical source comprising an optical beam generator and a pulse generator receives instructions from a controller and generates a pulsed optical beam in response to those instructions. The pulsed optical beam is directed into an optical fiber to generate a reflected beam from scattering centers within the optical fiber. A detector records a plurality of frames of data generated by the reflected beam, and the controller tracks an evolution of a speckle pattern carried by the reflected beam from the plurality of frames and calculates a strain induced in a section of the optical fiber from the evolution of the speckle pattern.

Methods and apparatuses for quantitative sensing using Rayleigh scattering in optical fiber

A method of interferometric optical sensing via spatial demodulation includes emitting a laser beam; splitting the laser beam into a reference beam and an interrogation beam; converting a desired signal into a change in the optical path of the interrogation beam via an optical sensor; and capturing the reference beam and the interrogation beam via a camera, wherein the interrogation beam is incident to the camera at a first angle and the reference beam is incident to the camera at a second angle different from the first angle, thereby causing an interference pattern at the camera.

Advantages of spatial demodulation in interferometric optical sensing applications

An apparatus includes a rigid support and a first cantilever including a first optical fiber and a first rigid ribbon. The first optical fiber and the first ribbon, together include a first neutral surface. The first optical fiber is connected to the rigid support. The first optical fiber includes at least one first wave-guiding core running parallel to the first neutral surface. Each of the at least one first wave-guiding core includes at least one first reflector. The first rigid ribbon is affixed to the first optical fiber and to said first rigid support. The apparatus further includes a first membrane surrounding the first cantilever.

Fiber optic cantilever acoustic vector sensor

A planar or cylindrical, cantilever-type apparatus including a rigid support. The apparatus further includes a first optical fiber connected to the rigid support, the first optical fiber including a first neutral axis and at least one first wave-guiding core running parallel to the first neutral axis and located at a distance from the first neutral axis, each of the at least one first wave-guiding core including at least one first reflector. The apparatus further includes a first membrane surrounding the first optical fiber; and a first liquid inside the first membrane and surrounding the first optical fiber, the first liquid including a Reynolds number less than one.

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Fairfax Station, VA, United States of America

Clay K Kirkendall