Low-cost fiber optic sensor for large strains

Patent metadata

Field	Value
Publication number	US-2016305771-A1
Application number	US-201615098891-A
Country	US
Kind code	A1
Filing date	Apr 14, 2016
Priority date	Apr 14, 2015
Publication date	Oct 20, 2016
Grant date	—

Abstract

A fiber grating device of low cost and arbitrary length is formed on a portion of a portion or the entirety of a highly elastic fiber optic core having a low Young's modulus of elasticity by causing elongation of the fiber optic core and forming or depositing a hard skin or cladding on the elongated fiber optic core. When the stress is then released, the hard skin or cladding buckles (including elastic or plastic deformation or both) to form wrinkles at the interface of the fiber optic core and the hard skin or cladding which are oriented circumferentially and highly uniform in height and spacing which can be varied at will by choice of materials, stretching, and thickness and composition of the cladding. Since the elastic elongation of the fiber optic core portion may be 200% or greater, an unprecedented measurement range is provided.

First claim

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is as follows:

1 . A fiber grating device comprising
an optical fiber core that is extensible by application of stress up to 200% or more of its unstressed length, and a hard skin or cladding on said optical fiber core and forming a wrinkled interface between said hard skin or cladding and said optical fiber core wherein height and periodicity of said wrinkles is altered by axial forces applied to said optical fiber core.

2 . The fiber grating device as recited in claim 1 , wherein said wrinkled interface extends substantially the entire length of said optical fiber.

3 . The fiber grating device as recited in claim 1 , wherein said wrinkled interface extends for less than the full circumference of said optical fiber core.

4 . The fiber grating device as recited in claim 3 , wherein said wrinkled interface extends for approximately one-half of a circumference of said optical fiber core.

5 . The fiber grating device as recited in claim 1 , wherein said skin or cladding is of a thickness not greater than one-half of a diameter of said fiber optic core.

6 . The fiber grating device as recited in claim 1 , wherein said hard skin is of a thickness of at least 5 nm.

7 . The fiber grating device as recited in claim 1 , wherein said hard skin or cladding is silica formed from material of said fiber optic core.

8 . The fiber grating device as recited in claim 1 , wherein said hard skin or cladding is formed of a metal film, a ceramic, a hard polymer, a composite of any two or more of metal, ceramic, or hard polymer, or a functionally graded film or material with functionally graded mechanical properties.

9 . The fiber grating device as recited in claim 1 , wherein said hard skin or cladding is formed of a cured nanoparticle ink.

10 . The fiber grating device as recited in claim 1 , wherein said hard skin or cladding is formed of multiple layers made of one or more of metal, ceramic, and cured nanoparticle ink.

11 . A method of forming a fiber grating device, said method comprising steps of
applying an axial force to at least a portion of an elastically deformable fiber optic core to produce an elongation, forming or applying a hard skin or cladding on said fiber optic core while elongated, and releasing said axial force to form wrinkles at an interface of said fiber optic core and said hard skin or cladding such that said axial force applied to produce said elongation produces buckling of said hard skin or cladding.

12 . The method as recited in claim 11 , including the further step of
irradiating said fiber optic core using ultraviolet light or a plasma to form said hard skin or cladding from material of said fiber optic core.

13 . The method as recited in claim 11 , wherein said elongation of said portion of said fiber optic core is up to 200% or more.

14 . The method as recited in claim 12 wherein a wavelength of said ultraviolet light is 254 nm and 185 nm.

15 . The method as recited in claim 11 , wherein said hard skin or cladding is one or multiple layers, each layer formed of either a metallic or ceramic film or a cured nanoparticle ink.

16 . The method as recited in claim 15 , wherein one or more of said metallic or ceramic films or cured ink layers is formed by physical or chemical vapor deposition or electroless or electrolytic plating.

17 . The method as recited in claim 11 , including the further step of applying a further cladding layer to said fiber grating device.

18 . The method as recited in claim 11 , including a further step of making a measurement using light transmitted through said fiber optic core and reflected from an end of said fiber optic core.

19 . The method as recited in claim 11 , including further steps of guiding light through said fiber optic core, and scattering said light from a location of said fiber grating device.

20 . A method of forming a fiber grating device, said method comprising steps of
forming or applying a hard skin or cladding on at least a portion of an elastically deformable fiber optic core, and permitting expansion of the hard skin or cladding or permitting contraction of the fiber optic core to form wrinkles at an interface of said fiber optic core and said hard skin or cladding.

Assignees

• Panat Rahul
• Li Lei
• Univ Washington State

Inventors

• Panat Rahul
• Li Lei

Classifications

• G02B6/02395

  Glass optical fibre with a protective coating, e.g. two layer polymer coating deposited directly on a silica cladding surface during fibre manufacture (G02B6/02052, G02B6/02057, G02B6/024, G02B6/032, G02B6/105, G02B6/14 take precedence; coating on fibre gratings G02B6/02104; multilayer core or cladding G02B6/036; reinforcing splice joints G02B6/2558; optical cables, i.e. comprising protective structures external to the protective coating such as a jacket or plural coated optical fibres G02B6/44; coating of glass to obtain optical fibres C03C25/104) · CPC title

• G01B11/165 Primary

  by means of a grating deformed by the object · CPC title

• G02B6/02142 Primary

  based on illuminating or irradiating an amplitude mask, i.e. a mask having a repetitive intensity modulating pattern · CPC title

• G02B6/02152

  involving moving the fibre or a manufacturing element, stretching of the fibre (G02B6/02147 takes precedence) · CPC title

• G02B6/021

  characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape · CPC title