# US 2010/0166358 A1 · Dual Fiber Grating and Methods of Making and Using Same

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- Number: US 2010/0166358 A1
- Document ID: US20100166358A1
- Status: Published application
- Kind: A1
- Application number: 12/346,164
- Filed: 2008-12-30
- Published: 2010-07-01
- Earliest claimed: 2008-12-30
- Inventors: Daniel Homa; Brooks Childers
- Web page: https://patentgrep.com/patent/US20100166358A1

## CPC

- B29D 11/00721: {involving preforms for the manufacture of light guides}
- G01K 11/3206: at discrete locations in the fibre, e.g. using Bragg scattering
- G01L 1/246: {using integrated gratings, e.g. Bragg gratings}
- G01L 1/26: Auxiliary measures taken, or devices used, in connection with the measurement of force, e.g. for preventing influence of transverse components of force, for preventing overload
- G02B 6/021: {characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape}
- G02B 6/02142: {based on illuminating or irradiating an amplitude mask, i.e. a mask having a repetitive intensity modulating pattern}
- G02B 6/03694: {Multiple layers differing in properties other than the refractive index, e.g. attenuation, diffusion, stress properties}
- G02B 6/02047: {Dual mode fibre (G02B6/105 takes precedence)}
- G02B 6/02133: {using beam interference}
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00)
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A multiple-layer fiber-optic sensor is described with dual Bragg gratings in layers of different materials, so that the known temperature and strain response properties of each material may be utilized to simultaneously correct the sensor output for temperature and strain effects.

## Claims

### Claim 1

A fiber optic sensor for use in simultaneously measuring temperature and strain variations, comprising
a first layer, comprising a first material and a first Bragg grating,
a second layer concentric with said first layer and comprising a second material and a second Bragg grating, wherein said first Bragg grating and said second Bragg grating are essentially identically patterned and are co-located along the longitudinal axis of the fiber optic sensor, and
a third layer concentric with and intermediate said first layer and said second layer, wherein said third layer comprises a material different than said first and second layers.

### Claim 2 (depends on 1)

The fiber optic sensor of claim 1, wherein said first layer comprises GeO2, Al2O3, boron-doped silica, or a selectively co-doped material.

### Claim 3 (depends on 1)

The fiber optic sensor of claim 1, wherein said second layer comprises SnO2, GeO2, or another photosensitive, doped material.

### Claim 4 (depends on 1)

The fiber optic sensor of claim 1, wherein said third layer comprises an essentially pure silica layer that is essentially not photosensitive.

### Claim 5 (depends on 1)

The fiber optic sensor of claim 1, wherein said fiber is a dual mode fiber.

### Claim 6 (depends on 5)

The fiber optic sensor of claim 5, wherein said fiber transmits LP01 and LP11 modes.

### Claim 7

A method of constructing a fiber optic sensor for simultaneously measuring temperature and strain deviations, comprising the steps of
providing a fiber optic preform,
depositing a first layer of a first photosensitive material on a surface of said preform, wherein after deposition said first layer comprises a first exposed surface,
depositing an intermediate layer of an essentially non-photosensitive material on said first exposed surface, wherein after deposition said intermediate layer comprises a second exposed surface,
depositing a second layer of a second photosensitive material on said second exposed surface,
pulling said preform into a fiber optic,
forming essentially identically-patterned Bragg gratings in said first layer and said third layer at essentially the same longitudinal position along said fiber optic.

### Claim 8 (depends on 7)

The method of claim 7, additionally comprising the step of selecting the material for said first layer from the group of SnO2, GeO2, or another photosensitive, doped material.

### Claim 9 (depends on 7)

The method of claim 7, additionally comprising the step of selecting the material for said second layer from the group of GeO2, Al2O3, boron-doped silica, or a selectively co-doped material.

### Claim 10 (depends on 7)

The method of claim 7, wherein the step of forming essentially identically-patterned Bragg gratings in said first layer and said third layer at essentially the same longitudinal position along said fiber optic additionally comprises the step of utilizing a source of ultraviolet light to form said Bragg gratings.

### Claim 11 (depends on 10)

The method of claim 10, additionally comprising the step of positioning a mask between said source of ultraviolet light and said fiber optic.

### Claim 12

A method of determining strain and temperature imposed on a sensor by its environment, wherein said sensor comprises at least two essentially concentric Bragg gratings formed in different materials, comprising the steps of observing essentially simultaneous responses from said Bragg gratings, and mathematically resolving values for temperature and strain imposed on said sensor from the responses of said Bragg gratings.

### Claim 13 (depends on 12)

The method of claim 12, additionally comprising the step of recording said responses from said Bragg gratings.