WO2008030224A1 - Capteur et système optiques en fibre de niobate de lithium - Google Patents

Capteur et système optiques en fibre de niobate de lithium Download PDF

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Publication number
WO2008030224A1
WO2008030224A1 PCT/US2006/034486 US2006034486W WO2008030224A1 WO 2008030224 A1 WO2008030224 A1 WO 2008030224A1 US 2006034486 W US2006034486 W US 2006034486W WO 2008030224 A1 WO2008030224 A1 WO 2008030224A1
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WO
WIPO (PCT)
Prior art keywords
fiber
light
lncf
host material
para
Prior art date
Application number
PCT/US2006/034486
Other languages
English (en)
Original Assignee
Fanasys Llc
Negussey, Dawit
Kornreich, Phillip
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fanasys Llc, Negussey, Dawit, Kornreich, Phillip filed Critical Fanasys Llc
Priority to PCT/US2006/034486 priority Critical patent/WO2008030224A1/fr
Publication of WO2008030224A1 publication Critical patent/WO2008030224A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03605—Highest refractive index not on central axis
    • G02B6/03611—Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35303—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using a reference fibre, e.g. interferometric devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
    • G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/0004—Force transducers adapted for mounting in a bore of the force receiving structure
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02295—Microstructured optical fibre
    • G02B6/023—Microstructured optical fibre having different index layers arranged around the core for guiding light by reflection, i.e. 1D crystal, e.g. omniguide
    • G02B6/02304—Core having lower refractive index than cladding, e.g. air filled, hollow core

Definitions

  • the present invention relates generally to fiber sensors, and more particularly to fiber sensors adapted for sensing load or pressure and strain or deformation changes in a host material.
  • the output is converted to electrical signal for processing and control decision.
  • the processor controls actuators to initiate an adaptive response.
  • This cycle continues to maintain set objectives for the system operation.
  • An example would be to use sensor input and output to determine the axle load and wheelbase of a vehicle and the control decision may be to collect an appropriate toll charge for the vehicle. If successive sensors are linked, the toll can reflect also the travel time and speed of the vehicle. In addition, the toll can also reflect the time of day and level of traffic.
  • Such a system would revolutionize the efficiency, energy conservation, law enforcement and safety of the highway system. While the technology for such a system exists, associated costs and complexity remain high.
  • An ordinary optical or plain fiber ( Figure 1 ) is a wave-guide through which light is propagated by continuous total internal reflection within the central core.
  • the glass surrounding the core is known as the cladding.
  • Both the core and cladding glass are dielectric materials. Because the index of refraction of the core is made higher than of the cladding, light waves remain trapped within the core in transmission.
  • optical fibers may be classified as single mode or multi mode fiber. Multi mode fibers have core diameters commonly of either 50 or 62.5 ⁇ m and can be used for sensors that rely on intensity modulation. Whereas, single mode fibers have diameters in the range of 3 to 10 ⁇ m. Long distance communication and data transmission lines are generally of single mode fiber.
  • Multimode fibers cannot be coupled. Apart from other inherent limitations, multi mode fiber sensors cannot be integrated within existing communication fiber grid network. Commonly used fiber optical sensors for pressure and strain detection consist of segments of single mode sized fibers that contain Bragg gratings. When the sensor segment is subjected to changes in pressure and compliant strain, the grate spacing becomes altered. Such changes modulate the light wave passing through the sensor segment. Monochromatic light source of high intensity and interferometer detectors are usually required for the sensor system. The cost of such systems can be of the order of several thousand dollars.
  • the present invention provides a system for sensing pressure and strain in a host material, comprising an optical fiber having first and second ends and extending at least partially within the host material, wherein the optical fiber comprises a glass core; a glass cladding surrounding the glass core; and a predetermined material coating the glass core that has an index of refraction that changes in proportion to changes in strain; a first light transmitting fiber having a first end and a second end that is coupled to the first end of the optical fiber; a light source coupled to the first end of said first light transmitting fiber; a second light transmitting fiber having a first end attached to the second end of the optical fiber and a second end; and a light detector coupled to the second end of the second light transmitting fiber.
  • the present invention pertains to Lithium-Niobate fiber optical sensors ("LNCF") and systems for detection of load or pressure and strain or deformation changes that occur in a host material.
  • the host material can be a component of a system, such as a part of a bridge, or a selected material, such as a geofoam, that provides a protective and compliant medium to which the LNCF would be securely attached.
  • the compliance of the host material and imposed physical changes on the bonded or attached LNCF segment can be calibrated to operate as sensors.
  • Lithium-Niobate Fiber Optical Sensors is anticipated to cover, but would not be limited to, smart materials and structures, intelligent transportation systems, clean air and energy conservation measures, seismic hazard mitigation, sonar detection, surveillance and security enforcements.
  • Figure 2 is a partially cut-away perspective view of a lithium niobate fiber used in accordance with the present invention
  • Figure 3 is a schematic representation of a first configuration of the system
  • Figure 4 is a schematic representation of a second configuration of the system
  • Figure 5 is a schematic representation of a test set-up and third configuration of the system.
  • Figure 6 is a graphical representation of collected test data.
  • Lithium Niobate (LNCF), designated generally by reference numeral 10, comprising a glass core 12, a sol-gel layer of lithium niobate 14 coating glass core 10, and a glass cladding 16 surrounding layer 14.
  • Lithium Niobate (LiNbOa) is a crystal with excellent electrooptical and acoustooptical properties.
  • the index of refraction (n) of thin film LiNbO 3 changes slightly and in proportion with the application of an electric field (electrooptical effect) or the application of stress (piezoelectric effect).
  • LiNbO 3 cylinder fiber such as LNCF 10
  • LNCF 10 is an optical fiber with a thin film of LiNb ⁇ 3 sol gel material 14 between the core 12 and cladding 16 of the fiber.
  • LNCF 10 preferably has a core diameter in the range of 3 to 10 ⁇ m and can mate with single mode data transmission fibers, as will be described hereinafter.
  • LiNb ⁇ 3 has an index of refraction much greater than either the core or cladding of optical plain fibers.
  • light mostly propagates in the thin film surrounding the core. Upon application of pressure and development of compliant strain in the LNCF, attenuation of the propagating light intensity takes place.
  • LNCF 10 Light intensity attenuation in strained segments of LNCF is due to the stress-induced change in the index of refraction in the thin film where the light propagates.
  • the index of refraction changes slightly causing the light propagating in the thin film to leak into the cladding.
  • the intensity of the light detected at the output becomes less than the input.
  • the intensity modulation of LNCF 10 can be a basis for pressure sensing and strain detection in a variety of host materials and applications.
  • a length of LNCF 1 0 is surface mounted ( Figure 3) or embedded within ( Figure 4) or through ( Figure 5) a host material 18.
  • a conventional single mode fiber 20 is spliced to one end of LNCF 1 0, and LNCF 10 includes a reflector (not shown) at its terminal end.
  • the opposite (or leading) end of single mode fiber 20 is connected to a light source 22, such as a LASER.
  • a directional coupler 24 is positioned at an intermediate location along fiber 20 and includes a second, single mode fiber 26 extending therefrom.
  • Directional couple 24 permits the light emanating from light source 22 to pass entirely through fiber 20 and into LNCF 10 where the light, in this configuration, is then reflected back through fiber 20. When the reflected light reaches directional coupler 24, it is fully directed through fiber 26.
  • the terminal end of fiber 26 is connected to a conventional optical detector 28 which detects the output level of the light passing through fiber 26.
  • second fiber 26 is spliced to the terminal end of LNCF 10 which, in this configuration, does not include a reflector, but rather permits passage of light therethrough.
  • detector 28 is still connected to the terminal end of fiber 28
  • light source 22 is still connected to the leading end of fiber 20.
  • the sensor in fiber form it could also be fabricated in sheet form with a central layer of glass surrounded on both sides by the sol gel layer and with a protective glass cladding on the outermost layer.
  • the panel could be incorporated into building facades, road surfaces, or other areas where it would be more conducive to use a fiber sensor configured to mount on a surface in sheet form as opposed to in embedded fiber form.
  • the invention described herein will be more fully appreciated by describing an experimental test set-up that has been used to verify the efficacy of the present invention. To that end:
  • LNCF based sensors can detect a wide range of disturbances ranging from sonar to seismic waves and pedestrian to vehicle traffic.
  • Geofoam as a medium for LNCF offers several potential advantages.
  • a sensor network or grid in 1 , 2 or 3 dimensions can be formed for placement in a geofoam block mold.
  • Encapsulating geofoam of desired size can be formed to contain the sensor grid.
  • the outer skin of the geofoam can be shaped and surface treated to enhance performance and provide protection. Grid crossings are adequate to promote sufficient micro bending. Presence of multiple fibers would offer redundancy and reliability and also disturbance direction detection capability.
  • Geofoam has very low density and high R-value. These special properties can be useful to produce a wide range of overall sensor sizes of manageable weight and very little variation in internal stress distribution due to self-weight.
  • the high R-value of geofoam can be useful in moderating temperature changes or maintaining steady operating temperatures.
  • the sensor system consisting of the LNCF sensors, light sources, detectors, multiplexers, microprocessor circuits and data storage or broadcast components can all be housed within the geofoam encasement.
  • Other host materials are, of course, possible. For instance, incorporating LNCF 10 in a pre-stressed concrete that will ultimately be used in a construction would be a typical host material.
  • structural materials, such as steel I-beams may also serve as the host material, as can the material composing a machine that is the subject of vibration monitoring or analysis.
  • LNCF 10 could be mounted to pipelines, tunnel walls, bridge structures/girders, building facades, and the like, composed of composite materials, plastic, or aluminum, for instance.
  • [Para 31 ] LNCF 10 can be easily integrated in new or existing single mode communication fiber networks.
  • LNCF sensors can rely on remote light source and detection, rapid wide band data transmission or can be networked with other sensors and systems to accomplish a variety of coordinated intelligent tasks.
  • LNCF sensors do not require special treatment such as etching necessary to form Bragg gratings. Drawing of LNCF is not different than for production of plain fiber.
  • LNCF sensors rely on intensity modulation, requirements for source power and coherence can be easily met by conventional power lasers or LEDs.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Transform (AREA)

Abstract

La présente invention concerne des capteurs et des systèmes optiques en fibre de niobate de lithium ('LNCF') destinés à détecter des modifications induites par une charge ou une pression et une contrainte ou une déformation apparaissant dans un matériau hôte. Le matériau hôte peut être un composant de système, tel une partie de pont, ou un matériau sélectionné, telle une géomousse, qui offre un support protecteur et accommodant sur lequel les LNCF peuvent bien se fixer.
PCT/US2006/034486 2006-09-02 2006-09-02 Capteur et système optiques en fibre de niobate de lithium WO2008030224A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2006/034486 WO2008030224A1 (fr) 2006-09-02 2006-09-02 Capteur et système optiques en fibre de niobate de lithium

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2006/034486 WO2008030224A1 (fr) 2006-09-02 2006-09-02 Capteur et système optiques en fibre de niobate de lithium

Publications (1)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10349937B2 (en) 2016-02-10 2019-07-16 Covidien Lp Surgical stapler with articulation locking mechanism
US10349941B2 (en) 2015-05-27 2019-07-16 Covidien Lp Multi-fire lead screw stapling device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4918305A (en) * 1988-08-01 1990-04-17 General Motors Corporation Fiber optic pressure sensor using pressure sensitive fiber different from input and output fibers
US5245180A (en) * 1992-06-02 1993-09-14 University Of Maryland Metal coated fiber optic damage detection sensors with system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4918305A (en) * 1988-08-01 1990-04-17 General Motors Corporation Fiber optic pressure sensor using pressure sensitive fiber different from input and output fibers
US5245180A (en) * 1992-06-02 1993-09-14 University Of Maryland Metal coated fiber optic damage detection sensors with system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10349941B2 (en) 2015-05-27 2019-07-16 Covidien Lp Multi-fire lead screw stapling device
US10349937B2 (en) 2016-02-10 2019-07-16 Covidien Lp Surgical stapler with articulation locking mechanism

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