CN111077606A - Liquid crystal microstructure optical fiber temperature sensor based on mode coupling effect - Google Patents

Liquid crystal microstructure optical fiber temperature sensor based on mode coupling effect Download PDF

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CN111077606A
CN111077606A CN201911243278.0A CN201911243278A CN111077606A CN 111077606 A CN111077606 A CN 111077606A CN 201911243278 A CN201911243278 A CN 201911243278A CN 111077606 A CN111077606 A CN 111077606A
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air holes
core
layer
optical fiber
liquid crystal
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CN111077606B (en
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陈海良
王明月
张文逊
张赢月
马明建
井西利
李曙光
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Hebei Hongyu Communication Equipment Co ltd
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Yanshan University
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    • 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
    • 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
    • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
    • 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
    • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
    • G02B6/02342—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by cladding features, i.e. light confining region
    • 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
    • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
    • G02B6/02385—Comprising liquid, e.g. fluid filled holes

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)

Abstract

The invention provides a liquid crystal microstructure optical fiber temperature sensor based on a mode coupling effect, wherein a substrate material of the microstructure optical fiber temperature sensor is silicon dioxide, and the microstructure optical fiber temperature sensor comprises a fiber core, a cladding and a perfect matching layer outside the cladding; liquid crystal is filled in the corresponding air holes right above the fiber core to form a defect core, and the left side and the right side of the defect core have two diameters d3Large air holes. The refractive index of the liquid crystal is higher than that of the substrate material, and the refractive index around the defect core can be adjusted through the two large air holes beside the defect core, so that the mode coupling between the defect core and the fiber core is easier to occur, the mode of the defect core of the microstructure optical fiber is changed, the movement of the coupling loss peak of the defect core and the fiber core is adjusted through optimizing the structural parameters of the microstructure optical fiber, and finally the temperature measurement is realized through the movement of the coupling loss peak.

Description

Liquid crystal microstructure optical fiber temperature sensor based on mode coupling effect
Technical Field
The invention belongs to the technical field of optical fiber sensing, and mainly relates to a liquid crystal microstructure optical fiber temperature sensor based on a mode coupling effect.
Background
At present, the size of a temperature sensor is large, and the temperature detection precision is not high enough.
The cladding region and the core region of the microstructure optical fiber are filled with different materials, so that the microstructure optical fiber has different performances and functions. The microstructure optical fiber is mainly made of quartz, and the influence of temperature on the quartz is small, so that a temperature sensitive material needs to be selected to be combined with the microstructure optical fiber to realize the temperature sensing of the microstructure optical fiber. Hameed M F O and the like research the coupling characteristic between a core guide mode in a nematic LC permeable PCF core and a surface plasma mode formed by filling nano-gold wires, and optimize structural parameters so as to achieve higher temperature sensitivity. Chenhailiang et al studied a new type of polarization beam splitter based on a dual-core silica glass photonic crystal fiber with a liquid crystal modulation core by a finite element method.
Liquid crystals are a physical state that is between isotropic liquid and solid crystals. The light is incident into the liquid crystal and then divided into two beams, one beam follows the refraction law of light, namely ordinary ray, and the refractive index of the ordinary ray is recorded as noThe size is independent of the direction of propagation of light in the crystal. The other light does not follow the law of refraction of light, called extraordinary light, the refractive index of which is denoted ne. The liquid crystal molecules have anisotropic physical properties and generally exhibit a rod-like shape, and are arranged in a certain rule within a certain temperature range. When the temperature is raised to destroy the alignment of the liquid crystals, i.e. the temperature reaches the clearing point of the substance, the substance becomes an isotropic liquid. When the temperature is lower than the clearing point of the liquid crystal, the optical properties of the substance are anisotropic. n isoAnd neAs the temperature changes.
The liquid crystal has the characteristic optical birefringence characteristic and good electromagnetic and temperature response characteristics, so the liquid crystal has application value for developing related scientific researches. Ho B Y and the like connect a small section of liquid crystal filled photonic crystal fiber between two sections of single mode fibers, so that a manufacturing method of the temperature all-fiber Mach-Zehnder interferometer is realized, and when the temperature is increased from 25 ℃ to 77 ℃, the wavelength temperature sensitivity of-1.55 nm/DEG C can be obtained. Kongting et al selectively infiltrated liquid crystal into two adjacent air holes to prepare a liquid crystal selectively-filled photonic crystal fiber with birefringence characteristics, the temperature was varied from 37.5 ℃ to 55 ℃, and the temperature variation range was small.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the liquid crystal is combined with the microstructure optical fiber by utilizing the characteristics that various optical properties of the liquid crystal are obvious to the external temperature, the electric field and the like, so that the problems of large volume and low temperature detection precision of the traditional temperature sensor are solved.
In order to solve the technical problems, the invention provides a liquid crystal microstructure optical fiber temperature sensor based on a mode coupling effect, wherein a substrate material of the microstructure optical fiber temperature sensor is silicon dioxide and comprises a fiber core, a cladding and a perfect matching layer on the outer side of the cladding; the fiber core is arranged at the center of the microstructure optical fiber and is formed by a region surrounded by a first layer of regular hexagonal air holes, and the diameter of the fiber core can be indirectly changed by adjusting the diameter of the first layer of air holes; the cladding is a circular area outside the fiber core, and three layers of hexagonal air holes are formed in the cladding; the diameter of the first layer of air holes is d2(ii) a The second layer of air holes are arranged outside the first layer of air holes, and liquid crystal is filled in the corresponding air holes right above the fiber core in the second layer of air holes to form a defect core with the diameter d1The two diameters of the left and right sides of the defect core are d3The large air holes are used for reducing the integral refractive index of the defect core; the rest of the air holes in the second layer and the air holes in the third layer outside the air holes in the second layer have the same diameter d4(ii) a The spacing between the air holes is Λ.
Preferably, the defect core has a diameter d11.2 μm, diameter d of the large air hole32.96 μm; the diameter of the first layer of air holes is d21.04 μm; in the air hole of the second layerAnd the other air holes of the third layer outside the air holes of the second layer have the same diameter d41.2 μm; the spacing Λ between the air holes is 2.8 μm.
Compared with the prior art, the invention has the following effects:
according to the invention, the characteristic that the refractive index of liquid crystal is very sensitive to temperature change and can be adjusted by changing the temperature is utilized, one air hole of the microstructure optical fiber is filled with the liquid crystal to form the defect core, the refractive index of the liquid crystal is higher than that of the substrate material, and the refractive index around the defect core can be adjusted by two large air holes beside the defect core, so that the defect core and the fiber core are easy to generate mode coupling, the defect core mode of the microstructure optical fiber is changed, the movement of the coupling loss peak of the defect core and the fiber core is adjusted by optimizing the structural parameters of the microstructure optical fiber, and finally the temperature measurement is realized by the movement of the coupling loss peak.
Drawings
FIG. 1 is a cross-sectional view of a microstructured optical fiber in an embodiment of the present invention;
FIG. 2 is a graph showing the variation of the refractive index of the filled liquid crystal according to the temperature in the embodiment of the present invention;
FIG. 3 is a Y-axis mode field coupling profile of a liquid crystal filled microstructured optical fiber in an embodiment of the present invention;
FIG. 4 is a graph of the Y-axis core and defect core refractive index and confinement loss as a function of wavelength for a liquid crystal filled microstructured optical fiber in an embodiment of the present invention;
FIG. 5 shows d at different temperatures according to example 1 of the present invention1When the thickness is 1.0 mu m, the variation distribution diagram of the limiting loss of the Y-axis fiber core and the defect core along with the wavelength is shown;
FIG. 6 shows d at different temperatures according to example 1 of the present invention1A profile of change in an exponential fit of Y-axis temperature and resonance wavelength at 1.0 μm;
FIG. 7 shows d at different temperatures according to example 1 of the present invention1When the thickness is 1.2 mu m, the variation distribution diagram of the limiting loss of the Y-axis fiber core and the defect core along with the wavelength is shown;
FIG. 8 shows d at different temperatures according to example 1 of the present invention1A profile of change in an exponential fit of Y-axis temperature and resonance wavelength at 1.2 μm;
FIG. 9 shows the diameter d at different temperatures according to example 1 of the present invention2When the thickness is 1.04 mu m, limiting loss of a Y-axis fiber core and a defect core changes along with the change of the wavelength;
FIG. 10 shows d at different temperatures according to example 1 of the present invention2A profile of change in an exponential fit of Y-axis temperature and resonance wavelength at 1.04 μm;
FIG. 11 shows the diameter d at different temperatures according to example 1 of the present invention2When the thickness is 1.36 mu m, the variation profile of the limiting loss of the Y-axis fiber core and the defect core along with the wavelength is shown; and
FIG. 12 shows d at different temperatures according to example 1 of the present invention2A profile of change in an exponential fit of Y-axis temperature and resonance wavelength at 1.36 μm;
the reference numbers illustrate:
1-liquid crystal core, 2-fiber core, 3-perfect matching layer, 4-substrate material, 5-big air hole, 6-first layer air hole, 7-air hole.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Example 1
In the cross-sectional view of the micro-structured fiber in the embodiment of the present invention shown in fig. 1, the base material 4 of the micro-structured fiber temperature sensor is silica, and comprises a fiber core 2, a cladding and a perfect matching layer 3 outside the cladding; the fiber core 2 is formed in the center of the microstructure optical fiber by a region surrounded by a first layer of regular hexagonal air, and the diameter of the fiber core 2 can be indirectly changed by adjusting the diameter of the first layer of air holes 6; the cladding is a circular area outside the fiber core, and three layers of hexagonal air holes are formed in the cladding; the diameter of the first layer air holes 6 is d21.04 μm; the second layer of air holes are arranged outside the first layer of air holes, and the corresponding air holes right above the fiber core in the second layer of air holes are filled with liquid crystal to form a hole with the diameter d11.0 μm defect core with two diameters d on the left and right sides3 Large air holes 5 of 2.96 μm for reducing defect coresThe bulk refractive index; the rest of the air holes in the second layer and the air holes in the third layer outside the air holes in the second layer have the same diameter d41.2 μm; the pitch Λ between the air holes 7 is 2.8 μm.
In the microstructure optical fiber MOF, the change of the refractive index of the liquid crystal is related to the electric field, the magnetic field and the temperature, the liquid crystal filled in the embodiment is that the extraordinary refractive index of the liquid crystal is reduced along with the increase of the temperature when the electric field is 90 degrees, and the ordinary refractive index of the liquid crystal is firstly slowly reduced and then increased along with the increase of the temperature. The distribution of the change of the refractive index of the filled liquid crystal with the temperature difference in the present embodiment is shown in fig. 2.
The mode field coupling distribution of the liquid crystal filled microstructured fiber in the Y-axis of this example is shown in fig. 3. The electric field distribution forms a fiber core mode in the fiber core, a defect mode is formed in the defect core, and when the phase matching condition is met, the fiber core mode and the defect core mode are in mode coupling.
The distribution of the refractive index and the limiting loss of the Y-axis fiber core and the defect core of the liquid crystal filled microstructure optical fiber according to the embodiment of the invention along with the change of the wavelength is shown in FIG. 4. In fig. 4, the intersection of the refractive indices of the fiber core and the liquid crystal core 1 represents a phase matching point at which the mode coupling effect occurs between the fiber core 2 and the liquid crystal core 1.
Example 2
In this example, the difference from example 1 is the diameter d of the defective core of the microstructured optical fiber11.2 μm, diameter d of the air holes of the first layer21.36 μm, the remaining parameters being the same.
The distribution of the Y-axis core and defect core confinement losses with wavelength at different temperatures in example 1 is shown in fig. 5, where the positions of the loss peaks of the core mode and defect mode shift with temperature, the loss peaks blue shift and the shift amount is 170 nm; the variation profile of the Y-axis core and defect core confinement loss with wavelength in example 2 is shown in FIG. 7, where the positions of the loss peaks of the core mode and defect core mode shift with temperature, the loss peaks shift blue and the shift amount is 220nm, and thus with d1The amount of shift of the loss peak increases.
Y-axis of example 1 at various temperaturesThe distribution of core and defect core confinement losses as a function of wavelength is shown in fig. 9. Along with the change of the temperature, the positions of the loss peaks of the fiber core mold and the defect core mold move, the loss peaks are subjected to blue shift, and the moving amount is 170 nm; the distribution of the Y-axis core and defect core confinement loss with wavelength in example 2 is shown in fig. 11. As can be seen from the graph, the positions of the loss peaks of the core mode and the defect mode shift with the temperature change, the loss peaks blue shift by 180nm, and the shift amount is d2The amount of shift of the loss peak increases.
The variation distribution of the exponential fit relationship between the Y-axis temperature and the resonance wavelength in example 1 of the present invention at different temperatures is shown in FIG. 6, which is a correlation coefficient R of the exponential fit curve20.99796, sensitivity-4.15 nm/deg.C at 30 deg.C; the distribution of the change of the exponential fit relationship between the Y-axis temperature and the resonance wavelength in example 2 of the present invention is shown in fig. 8, and the correlation coefficient R of the exponential fit curve is shown20.99567, sensitivity was-5.37 nm/deg.C at 30 deg.C. By optimizing the diameter d1，d1When R is 1.0 μm2Maximum, but d1D is selected because the sensitivity is maximal at 1.2 μm1The sensitivity of the liquid crystal microstructure optical fiber temperature sensor is improved when the thickness is 1.2 mu m.
The distribution of the change of the exponential fit relationship between the Y-axis temperature and the resonance wavelength in example 1 at different temperatures is shown in FIG. 10, in which the correlation coefficient R of the exponential fit curve20.99905, sensitivity-4.22 nm/deg.C at 30 deg.C; FIG. 12 is a graph showing the distribution of the change in the relationship between the Y-axis temperature and the resonance wavelength in example 2, and the correlation coefficient R of the exponential fit curve20.99392, sensitivity was-4.19 nm/deg.C at 30 deg.C. By optimizing the diameter d2，d2When R is 1.04 μm2Maximum and maximum sensitivity, so d is selected2The sensitivity of the liquid crystal microstructure fiber temperature sensor is improved when the thickness is 1.04 mu m.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims (2)

1. A liquid crystal microstructure optical fiber temperature sensor based on mode coupling effect is characterized in that a substrate material of the microstructure optical fiber temperature sensor is silicon dioxide and comprises a fiber core, a cladding and a perfect matching layer on the outer side of the cladding; the fiber core is arranged at the center of the microstructure optical fiber and is formed by a region surrounded by a first layer of air holes in a regular hexagon; the cladding is a circular area outside the fiber core, and three layers of hexagonal air holes are formed in the cladding; the diameter of the first layer of air holes is d2(ii) a The second layer of air holes are arranged outside the first layer of air holes, and liquid crystal is filled in the corresponding air holes right above the fiber core in the second layer of air holes to form a defect core with the diameter d1The two diameters of the left and right sides of the defect core are d3Large air holes; the rest of the air holes in the second layer and the air holes in the third layer outside the air holes in the second layer have the same diameter d4(ii) a The spacing between the air holes is Λ.
2. The liquid crystal microstructure optical fiber temperature sensor based on mode coupling effect as claimed in claim 1, wherein the defect core has a diameter d11.2 μm, diameter d of the large air hole32.96 μm; the diameter of the first layer of air holes is d21.04 μm; the rest of the air holes in the second layer and the air holes in the third layer outside the air holes in the second layer have the same diameter d41.2 μm; the spacing Λ between the air holes is 2.8 μm.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113568090A (en) * 2021-07-14 2021-10-29 艾菲博(宁波)光电科技有限责任公司 Multi-core microstructure optical fiber for distributed sensing system

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Publication number Priority date Publication date Assignee Title
CN102243113A (en) * 2011-06-22 2011-11-16 天津大学 Photonic crystal fiber grating temperature sensor with tunable wavelength
CN102495022A (en) * 2011-11-11 2012-06-13 江苏大学 Two-core photonic crystal optical fibre refractive index sensor and sensing system

Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
CN102243113A (en) * 2011-06-22 2011-11-16 天津大学 Photonic crystal fiber grating temperature sensor with tunable wavelength
CN102495022A (en) * 2011-11-11 2012-06-13 江苏大学 Two-core photonic crystal optical fibre refractive index sensor and sensing system

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陈海良: "功能材料填充微结构光纤光子器件的研究", 《中国博士学位论文全文数据库，信息科技辑》 *

Cited By (2)

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Publication number Priority date Publication date Assignee Title
CN113568090A (en) * 2021-07-14 2021-10-29 艾菲博(宁波)光电科技有限责任公司 Multi-core microstructure optical fiber for distributed sensing system
CN113568090B (en) * 2021-07-14 2023-08-22 艾菲博(宁波)光电科技有限责任公司 Multi-core microstructure optical fiber for distributed sensing system

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