CN211401478U - Double-core coupling-based perturbation type photonic crystal fiber temperature sensor - Google Patents

Double-core coupling-based perturbation type photonic crystal fiber temperature sensor Download PDF

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CN211401478U
CN211401478U CN202020234893.7U CN202020234893U CN211401478U CN 211401478 U CN211401478 U CN 211401478U CN 202020234893 U CN202020234893 U CN 202020234893U CN 211401478 U CN211401478 U CN 211401478U
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double
defect
core coupling
core
photonic crystal
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蔡俊
高翔
张江梅
陈奂文
董超
张克非
蔡哲军
白筱蕊
唐鹏
王坤朋
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Southwest University of Science and Technology
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Abstract

The utility model discloses a perturbation type photonic crystal fiber temperature sensor based on double-core coupling, which comprises an air hole cladding (4) and a double-core coupling waveguide structure (3); the air hole cladding (4) is arranged on the outer layer of the optical fiber, and the air hole cladding (4) is formed by periodically arranging a plurality of defective small holes (1) and is in a regular hexagon structure; the double-core coupling waveguide structure (3) is arranged in the middle of the optical fiber and is arranged in the air hole cladding (4); the double-core coupling waveguide structure (3) comprises two defect large holes (2) and a defect slit (5), wherein the two defect large holes (2) are communicated through the defect slit (5) with curvature; filling ethanol liquid in the double-core coupling waveguide structure (3); this application utilizes the structure advantage of optic fibre itself and filling material's thermophoto physical properties, and the physical properties through filling material gos deep into the couple transmission characteristic of influence twin-core, realizes high accuracy temperature sensing, has advantages such as anti-electromagnetic interference, corrosion-resistant, the structure is small and exquisite and low cost.

Description

Double-core coupling-based perturbation type photonic crystal fiber temperature sensor
Technical Field
The utility model belongs to the technical field of the optical fiber sensing, concretely relates to based on two core coupling perturbation type photonic crystal optic fibre temperature sensor.
Background
With the rapid development of science and technology, a variety of temperature sensors appear in recent years, such as an expansion type thermometer, a temperature sensitive semiconductor and an optical fiber sensor, have respective use conditions and play a role in temperature sensing. However, photonic crystals, as a new type of optical fiber, have unique structure and transmission characteristics, and have been the focus of attention in recent years.
The photonic crystal fiber has the characteristics of large mode field area, single-mode transmission, high nonlinearity, high birefringence, ultralow loss and the like, can be widely applied to various designs and fields, and achieves the purposes of efficient transmission, high-precision measurement and the like. At present, with the continuous and deep research of photonic crystal fibers, various photonic crystal fiber structures gradually appear, and the double-core photonic crystal fiber is focused as an important branch.
The double-core photonic crystal fiber can realize the design of a high-precision sensing device according to the variability of the photonic crystal fiber structure design and the coupling characteristic of the double-core structure.
The optical fiber sensing devices are various in types, such as an optical fiber grating sensor, a photonic crystal filling sensor, a directional coupling sensor, optical fiber surface plasma sensing and the like, however, most of the sensing devices have the problems of low sensing precision, small monitoring range, difficult and expensive manufacturing process and the like, and are difficult to meet the actual requirements.
For the double-core photonic crystal fiber, the double-core photonic crystal fiber can be applied to detection in different environments according to the coupling and transmission characteristics of the optical field in the waveguide, and high-precision and wide-range measurement is realized. However, the current dual-core coupling technology is mainly limited to general core coupling and pore filling, and does not fully utilize the characteristics of the photonic crystal structure and the filling material.
Therefore, in order to solve the above problems, a temperature sensor based on a dual-core coupling perturbation type photonic crystal fiber needs to be provided.
Disclosure of Invention
The objective of the present invention is to provide a temperature sensor based on a twin-core coupled perturbation type photonic crystal fiber in order to solve the above problems.
The utility model discloses a following technical scheme realizes above-mentioned purpose:
based on two core coupling perturbation type photonic crystal optic fibre temperature sensor includes:
an air hole cladding (4); the air hole cladding (4) is arranged on the outer layer of the optical fiber; the air hole cladding (4) is formed by periodically arranging a plurality of defective small holes (1) and is in a regular hexagon structure;
a dual core coupled waveguide structure (3); the double-core coupling waveguide structure (3) is arranged in the middle of the optical fiber and is arranged in the air hole cladding (4); the double-core coupling waveguide structure (3) comprises two defect large holes (2) and a defect slit (5), wherein the two defect large holes (2) are communicated through the defect slit (5) with curvature; filling ethanol liquid in the double-core coupling waveguide structure (3); the double-core coupling waveguide structure (3) is symmetrically arranged based on the central axis of the optical fiber.
Preferably, the diameter of the defective pinhole (1) is 1.6125 μm, and the distance between two adjacent defective pinholes (1) is 4.3 μm.
Preferably, the diameter of the defect macropore (2) is 12.9 μm, and the distance from the center of the defect macropore (2) to the central axis of the optical fiber is 10 μm.
Preferably, the radius of curvature of the defect slit (5) is 7.5 μm and the center waist distance is 1.6025 μm at a temperature T293.15K.
The beneficial effects of the utility model reside in that:
this application utilizes the structure advantage of optic fibre itself and filling material's thermophoto physical properties, and the physical properties through filling material gos deep into the couple transmission characteristic of influence twin-core, realizes high accuracy temperature sensing, has advantages such as anti-electromagnetic interference, corrosion-resistant, the structure is small and exquisite and low cost.
Drawings
FIG. 1 is a schematic cross-sectional view of a dual-core coupled perturbation type photonic crystal fiber;
FIG. 2 is a graph of dual-core coupled energy distribution during optical transmission;
fig. 3 shows the transmission line of a single port at a temperature T303K;
FIG. 4 is a graph of transmission lines at different temperatures;
FIG. 5 is a graph of a fit of different temperature versus peak position;
FIG. 6 is a graph showing the transmission lines of the corresponding bands at a large temperature variation;
in the figure: 1-defect small hole, 2-defect large hole, 3-double-core coupling waveguide structure, 4-air hole cladding and 5-defect slit.
Detailed Description
The present invention will be further explained with reference to the accompanying drawings:
as shown in fig. 1, the photonic crystal fiber temperature sensor based on the dual-core coupling perturbation type comprises:
an air hole cladding (4); the air hole cladding (4) is arranged on the outer layer of the optical fiber; the air hole cladding (4) is formed by periodically arranging a plurality of defective small holes (1) and is in a regular hexagon structure;
a dual core coupled waveguide structure (3); the double-core coupling waveguide structure (3) is arranged in the middle of the optical fiber and is arranged in the air hole cladding (4); the double-core coupling waveguide structure (3) comprises two defect large holes (2) and a defect slit (5), wherein the two defect large holes (2) are communicated through the defect slit (5) with curvature; filling ethanol liquid in the double-core coupling waveguide structure (3); the double-core coupling waveguide structure (3) is symmetrically arranged based on the central axis of the optical fiber.
The photonic crystal fiber is characterized in that a double-fiber-core structure is introduced around the center of the photonic crystal fiber and is an optical power coupling transmission path; two defect macropores (2) filled with refractive index liquid are arranged above and below the cross section of the plate, the defect macropores (2) are communicated through a vertical hyperbolic defect slit (5), the curvature radius of the defect slit (5) is 7.5 mu m at the temperature T293.15K, and the distance between the waists is L0The coupling perturbation layer is formed in a mode of 1.6025 microns, the defect slit (5) is communicated with the two defect large holes (2) to form a dumbbell-shaped refractive index liquid coupling perturbation filling area, the perturbation effect during double-core coupling transmission is achieved, and the double-core waveguide power transmission is affected. For the coupling perturbation filling area, ethanol is selected as a filling material in the design, and high-precision temperature sensing is realized.
For the coupling perturbation filling area, other materials can be selected as filling materials, and the refractive index range is about 1.32-1.43. The refractive index of the selected ethanol liquid is 1.36048 at the temperature T293.15K.
In some embodiments, the diameter d of the defective pinhole (1) is 1.6125 μm, and the pitch Λ between two adjacent defective pinholes (1) is 4.3 μm. The ratio d/Λ of the diameter of the defective small hole (1) to the distance between the defective small holes (1) is less than 0.45, and the single-mode non-cutoff transmission condition of the photonic crystal fiber is met.
Under the optimization of experimental simulation, the diameter of the defect macropore (2) is 12.9 mu m, and the distance from the center of the defect macropore (2) to the central axis of the optical fiber is 10 mu m.
The utility model discloses a to the high accuracy detection principle of temperature, mainly according to external environment temperature's change, influence the refracting index and the expansion volume of the filling liquid body in the coupling perturbation layer, and then change model effective refractive index and coupling interval, let light in two core waveguide coupling transmission processes, receive the influence that different refracting index liquid and coupling interval change, finally form different transmission spectrums at output port, through the removal of analysis transmission spectrum peak value, realize the high accuracy detection of temperature.
The ethanol has better thermo-optic effect, better linear change relation between the refractive index and the temperature within a certain range, low cost and easy filling, and the thermo-optic coefficient α is 3.94 × 10-4K, coefficient of thermal expansion β ═ 1.09 × 10-3The refractive index of the ethanol changes along with the change of the temperature T according to the following relation:
n=nO-α(T-T0) (1)
wherein n is the dependent variable of the refractive index of ethanol at different temperatures; n is0For ethanol at a temperature T0Refractive index n at 293.15K01.36048; t is a temperature variable.
In addition to causing a change in the refractive index of the fill liquid during a change in ambient temperature, the thermal expansion of the ethanol, which is related to the change in coupling distance, is approximately linear expansion within a certain range, and can be shown as:
L=L0+Loβ(T-T0) (2)
wherein L is the dependent variable of the distance between the waists at different temperatures, L0The initial spacing is 8.6 × 10 since the thermo-optic coefficient α of the quartz glass-6K, coefficient of thermal expansion β ═ 5.5 × 10-7and/K is different from the filling material by more than two orders of magnitude, so that the influence of temperature on the refractive index and the thermal expansion of the quartz is ignored, and only the influence of the temperature on the refractive index change of the filling material and the influence of the thermal expansion on the slit distance in the coupling perturbation layer are considered.
The utility model discloses based on two core coupling perturbation type photonic crystal optic fibre temperature sensor's concrete implementation method, mainly according to the coupling theory and above relational expression, analysis ambient temperature and ethanol refracting index, coupling interval's change relation. And (3) adopting a BeamPROP module in Rsoft to perform simulation analysis on power coupling and output port transmission spectrums at different ambient temperatures. When the ambient temperature T is 303K, the input wavelength is 1550nm, the refractive index n of ethanol is 1.3565991, and the coupling distance L is 1.61970524125 μm, the power coupling relationship during two-channel coupling transmission is obtained through simulation analysis, as shown in fig. 2. During optical transmission, the transmission distance of the double-core coupling power is periodically and stably changed, and the coupling length Lc18948 μm. When the wave band analysis is carried out on a certain environment, the coupling length of the double-core coupling transmission can be changed under different wavelengths according to the coupling theory, and different transmission spectral lines are finally formed at an output port. Therefore, here, with the same temperature environment, the transmission spectrum of one of the ports at different wavelengths is obtained by simulation analysis, as shown in fig. 3. It contains a complete transmission peak in this band. From the coupling theory, when the effective refractive index and the coupling distance are changed, the peak package of the transmission spectrum at the wave band is changed. When the environmental conditions are changed, according to the expressions (1) and (2), transmission spectrums at different temperatures are obtained when the simulation analysis temperatures are 304K, 305K and 306K. As the temperature increases, the peak thereof moves for a long distance and the peak moves in a long wavelength direction, as shown in fig. 4. After a large number of data simulations, the data were processed by Matlab to obtain a peak shift fit curve, which has a very good linear relationship as shown in fig. 5, and the functional relationship between the peak shift S (μm) and the temperature t (K) is S (μm) ═ 0.004(μm/K) t (K) +0.2514(μm), and the temperature sensitivity is 0.004 μm/K.
According to the theory of double-core coupling, when the effective refractive index and the coupling distance change greatly, the transmission peaks of the coupled and transmitted ports form different transmission peaks under various wave bands due to the periodic coupling of transmission power, and the half-height widths of the transmission peaks are different. In order to control the monitoring wave band range to be about 1.55 mu m, the required transmission peak can be determined under the long wave band. When the temperature is changed in an overlarge range, according to the movement rule of the projection peak, high-precision detection of each temperature can be realized only by adjusting the detection wave width or widening the detection range of the transmission spectrum, and the result is shown in fig. 6. When the environmental temperature changes greatly, the temperature detection can be carried out, and when the temperature changes in a small range, the detection precision is higher. The utility model discloses a twin-core coupling perturbation photonic crystal fiber sensor can adjust the input wavelength according to the different temperature range of measuring environment, and the transmission peak under the slight change of temperature appears in the control wavelength interval removes, and effectual analysis ambient temperature reaches the high accuracy real-time detection's to the temperature purpose.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the above embodiments, and that the foregoing embodiments and descriptions are provided only to illustrate the principles of the present invention without departing from the spirit and scope of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (4)

1. Based on two core coupling perturbation type photonic crystal fiber temperature sensor, its characterized in that includes:
an air hole cladding (4); the air hole cladding (4) is arranged on the outer layer of the optical fiber; the air hole cladding (4) is formed by periodically arranging a plurality of defective small holes (1) and is in a regular hexagon structure;
a dual core coupled waveguide structure (3); the double-core coupling waveguide structure (3) is arranged in the middle of the optical fiber and is arranged in the air hole cladding (4); the double-core coupling waveguide structure (3) comprises two defect large holes (2) and a defect slit (5), wherein the two defect large holes (2) are communicated through the defect slit (5) with curvature; filling ethanol liquid in the double-core coupling waveguide structure (3); the double-core coupling waveguide structure (3) is symmetrically arranged based on the central axis of the optical fiber.
2. The photonic crystal fiber temperature sensor based on the dual-core coupling perturbation type, according to claim 1, wherein: the diameter of the defective pinhole (1) is 1.6125 mu m, and the distance between two adjacent defective pinholes (1) is 4.3 mu m.
3. The photonic crystal fiber temperature sensor based on the dual-core coupling perturbation type, according to claim 1, wherein: the diameter of the defect macropore (2) is 12.9 mu m, and the distance from the center of the defect macropore (2) to the central axis of the optical fiber is 10 mu m.
4. The photonic crystal fiber temperature sensor based on the dual-core coupling perturbation type, according to claim 1, wherein: the radius of curvature of the defect slit (5) at a temperature T293K is 7.5 μm, and the center waist distance is 1.6025 μm.
CN202020234893.7U 2020-03-02 2020-03-02 Double-core coupling-based perturbation type photonic crystal fiber temperature sensor Active CN211401478U (en)

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Application Number Priority Date Filing Date Title
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