CN110954239A - Temperature sensor based on double-core single-hole optical fiber - Google Patents
Temperature sensor based on double-core single-hole optical fiber Download PDFInfo
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
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Abstract
The invention provides a temperature sensor based on a double-core single-hole optical fiber. The light source 1 is connected with a port 1 of an optical circulator 3 through a single mode fiber 2-1, a port 2 of the optical circulator 3 is connected with an optical fiber sensing probe 5 through a single mode fiber 2-2, and a port 3 of the optical circulator 3 is connected with a spectrum analyzer 4 through a single mode fiber 2-3. The optical fiber sensing probe 5 is composed of a Michelson interferometer and comprises a single-mode optical fiber, a double-core single-hole optical fiber filled with high thermo-optic coefficient liquid in a hole and a reflecting film. The two ends of the double-core single-hole optical fiber are respectively welded with one section of double-core optical fiber in a core-to-core mode, the double-core optical fiber at one end is welded with the single-mode optical fiber, the end face of the double-core optical fiber at the other end is plated with a reflecting film, and the manufacturing of the Michelson interferometer is completed by tapering at the welding position of the single-mode optical fiber and the double-core optical fiber. The invention realizes the measurement of the temperature by utilizing the interference of the light transmitted in the two fiber cores of the double-core single-hole optical fiber, and has simple structure and high sensitivity.
Description
(I) technical field
The invention relates to an optical fiber temperature sensor, in particular to a temperature sensor based on a double-core single-hole optical fiber, and belongs to the technical field of optical fiber sensing.
(II) background of the invention
The optical fiber sensing technology is based on the guided wave principle, utilizes optical fibers as a transmission medium or a sensing device, and utilizes light waves as a carrier. With the development of optical fiber communication technology, great development is made in the aspects of sensing principle, sensing structure, equipment manufacturing process means and the like, and various novel optical fiber sensors are developed. Compared with the traditional electromagnetic sensor, the optical fiber sensor has the characteristics of electromagnetic interference resistance, light weight, chemical corrosion resistance, quick response and the like, can be used for measuring parameters such as temperature, strain, pressure, magnetic field, acceleration, displacement, liquid level and the like, and is widely applied to various fields related to civil life and national defense. Particularly, the optical fiber sensor is used for effective detection in severe environment, so that the technical problems of various industries are solved.
The optical fiber sensor is classified into an amplitude modulation type, a phase modulation type, a wavelength modulation type, and a polarization modulation type according to a sensing mechanism. The amplitude modulation type is mainly to directly modulate the light intensity output by the optical fiber by using the physical quantity to be measured and detect the measured quantity by detecting the light intensity change, and the sensor of the type has a simple structure, but the light intensity is easily interfered by the vibration of the optical fiber. The wavelength modulation type mainly changes the wavelength of light transmitted in an optical fiber by using an external variable, and obtains the change condition of the external environment through monitoring the wavelength. The polarization modulation type mainly utilizes the polarization property of light to demodulate, and usually utilizes the effects of electro-optic, magneto-optic, photoelastic and the like, and an analyzer is used in the demodulation process, so that the light path is complex. The phase modulation type is a type that modulates the phase of light transmitted in an optical fiber by using an external parameter, and such a sensor has high sensitivity because the phase of light is sensitive to the external environment.
With the development of society, the requirements of people on the precision and the sensitivity of the sensor are continuously improved, the requirements of equipment miniaturization and integration are increased, and the phase modulation type optical fiber sensor becomes a hot point of research of people. The phase modulation type optical fiber sensor modulates a signal by interference of light. At present, the main interference modes include Mach-Zehnder interference, Michelson interference, Fabry-Perot interference, Sagnac interference and the like. For example, in 2011, m.yang et al (fiber-in-line Mach-zehnder interferometer structured by selective introduction of two air holes in photonic crystal fiber) proposed that Mach-zehnder type interferometers are fabricated by selectively filling liquid into the air holes of photonic crystal fibers to complete temperature detection, but this method requires filling of the air holes specific to photonic crystal fibers, which is difficult to operate. Tianmian Zhou et al (low cost non-additive tapered fiber for high-sensitive temperature sensing) proposed to manufacture a temperature sensor by tapering a single-mode optical fiber, and the temperature sensor is implemented by intermode interference at the optical fiber taper, but the optical fiber taper as a sensing part is fragile, and the optical fiber taper is easily broken due to external factors, and the sensitivity of the temperature sensor manufactured by the method is low.
Disclosure of the invention
The invention aims to provide a temperature sensor based on a double-core single-hole optical fiber, which has the advantages of simple and compact structure, good stability and high sensitivity.
In order to achieve the purpose, the invention adopts the scheme that:
the optical fiber sensing probe sequentially comprises a single-mode optical fiber, an optical fiber cone, a double-core optical fiber, a double-core single-hole optical fiber, a double-core optical fiber and a reflecting film, wherein the double-core single-hole optical fiber, the double-core optical fiber and the reflecting film are filled with high-heat-coefficient liquid, and the double-core optical fiber and the reflecting film jointly form a Michelson interference type temperature sensing probe. The used double-core optical fiber and the double-core single-hole optical fiber have the same fiber core distance, namely, light transmitted along the two fiber cores of the double-core optical fiber can be continuously transmitted along the two fiber cores of the double-core single-hole optical fiber after core-to-core welding.
The working principle of the invention is as follows:
the thermo-optic effect is a physical phenomenon in which the refractive index of an optical medium changes with a change in temperature. The thermo-optic effect is an optical property of an optical material itself, and in a changing temperature field, the refractive index of a crystal, a semiconductor material, glass and other materials applied in different optical devices and optical systems changes along with the change of temperature.
According to the principle of interference
Wherein the phase position
Effective refractive index difference Δ neff＝n1,eff-n2,eff. According to the above formula, the output light of interference is related to the light intensity and phase of the two interference light paths. Under certain conditions of length and intensity of the two interference arms,the output interference spectrum is only related to the phase, namely the difference of effective refractive indexes of the two interference arms.
The working process of the sensing probe comprises the following steps: broadband light signals are input from the single-mode optical fiber, light is coupled into two fiber cores of the double-core optical fiber according to a certain light intensity ratio through the optical fiber cone, and the two fiber cores can be regarded as two interference arms of the interferometer. When the light of the two fiber cores is transmitted to the end face of the double-core single-hole optical fiber, the light is reflected by the reflecting film and transmitted back along the same path, and interference occurs at the optical fiber cone. Because the hole of the double-core single-hole optical fiber is filled with liquid with high thermo-optic coefficient, the fiber cores adjacent to the air hole are influenced by the liquid in the hole, the effective refractive index of the fiber cores is changed, and the light transmitted along the two fiber cores generates optical path difference, so that an interference output spectrum can be observed at the output end. Since the filled liquid has a high thermo-optic coefficient, a change in temperature causes a change in the refractive index of the liquid, thereby causing a change in the effective refractive index of the core adjacent to the air hole, and ultimately a change in the interference spectrum. From the above, the measurement of the temperature can be realized by observing the change of the interference spectrum.
In order to effectively influence the liquid in the air hole on one of the fiber cores, the air hole is close enough to one of the fiber cores, and the air hole can be in any direction of the fiber core. The air holes are sufficiently distant from the other core so that the liquid filled in the air holes does not affect the light transmitted along the core.
According to the conception and the working principle of the invention, the invention adopts the following technical scheme:
a temperature sensor based on a double-core single-hole optical fiber comprises a light source, a single-mode optical fiber, an optical circulator, a double-core optical fiber, a double-core single-hole optical fiber, a reflecting film and a spectrum analyzer. The light source is used as an incident end and is connected with a port 1 of the optical circulator through a single mode fiber, a port 2 of the optical circulator is connected with the optical fiber sensing probe through the single mode fiber, and a port 3 of the optical circulator 3 is used as an output end and is connected with the optical spectrum analyzer 4 through the single mode fiber. The optical fiber sensing probe is a Michelson interferometer which consists of a single-mode optical fiber, an optical fiber cone, a double-core optical fiber, a double-core single-hole optical fiber filled with high thermo-optic coefficient liquid in a hole and a reflecting film.
The Michelson interferometer is realized by welding a section of double-core optical fiber at each of two ends of the double-core single-hole optical fiber, welding one end of one section of double-core optical fiber with the single-mode optical fiber, plating a reflecting film on the end face of the other section of double-core optical fiber, filling high-thermal-optical-coefficient liquid in an air hole of the double-core single-hole optical fiber, and finally performing fusion tapering at the welding position of the single-mode optical fiber and the double-core optical fiber.
The sensor can have high sensitivity by using liquid with high thermo-optic coefficient, and the filled liquid can be prepared refractive index matching liquid, or liquid such as glycerol, ethanol and the like and mixed liquid of the liquid and water.
The used double-core optical fiber and the double-core single-hole optical fiber have the same fiber core distance, namely after the two optical fibers are welded in a core-to-core mode, the light energy transmitted along the two fiber cores of the double-core optical fiber is continuously transmitted along the two fiber cores of the double-core single-hole optical fiber. The distance between the two fiber cores of the double-core single-hole optical fiber used is more than 10 microns, so that light transmitted along the two fiber cores cannot be coupled. The liquid filled in the air holes affects only one core, the air holes can be in any direction of the core, and the air holes do not affect the light transmitted along the other core.
The cut end face of the optical fiber may be used as a reflective film of the sensor, or the end face may be plated with a metal film.
The filling of the high thermo-optic coefficient liquid adopts a method of welding first and then filling, so that the vaporization of the liquid during welding is avoided. Firstly, welding two ends of a double-core single-hole optical fiber with the double-core optical fiber in a core-to-core mode, then manufacturing two microgrooves communicated with an air hole on a cladding on one side of the air hole of the double-core single-hole optical fiber by using a laser etching, heating and hole blowing or chemical corrosion method, then filling by using liquid siphon, and finally plugging the two microgrooves by using ultraviolet glue.
(IV) description of the drawings
Fig. 1 is a schematic structural diagram of a temperature sensor based on a dual-core single-hole optical fiber.
Fig. 2 is a schematic structural view of the temperature sensing probe of the present invention.
FIG. 3 is a schematic cross-sectional view of a dual-core single-hole fiber.
FIG. 4 is a schematic cross-sectional view of a dual core optical fiber.
Fig. 5 is a schematic liquid fill.
FIG. 6 is an interference spectrum at different temperatures.
FIG. 7 is a graph of wavelength versus temperature.
(V) detailed description of the preferred embodiments
The following describes an embodiment of the dual-core single-hole fiber-based temperature sensor according to the present invention with reference to the accompanying drawings:
fig. 1 shows a schematic structural diagram of a temperature sensor based on a dual-core single-hole optical fiber. The device comprises a light source 1, a single mode fiber 2, an optical circulator 3, a spectrum analyzer 4 and a temperature sensing probe 5. The light source is used as an incident end and is connected with a port 1 of the optical circulator through a single mode fiber, a port 2 of the optical circulator is connected with the optical fiber sensing probe through the single mode fiber, and a port 3 of the optical circulator 3 is used as an output end and is connected with the optical spectrum analyzer 4 through the single mode fiber. The structural schematic diagram of the optical fiber sensing probe is shown in fig. 2 and is composed of a Michelson interferometer which is composed of a single-mode optical fiber 2-2, an optical fiber cone 5-1, a double-core optical fiber 5-2, a double-core single-hole optical fiber 5-3 filled with high thermo-optic coefficient liquid in a hole and a reflecting film 5-4. The single-mode optical fiber 2-2 is connected with one end of the double-core optical fiber 5-2-1 through an optical fiber cone 5-1, and the other end of the double-core single-hole optical fiber 5-3; the other end of the double-core single-hole optical fiber is connected with the other section of double-core optical fiber 5-2-2, and the tail end of the double-core optical fiber 5-2-2 is plated with a metal reflecting film 5-4.
The structure of the dual-core single-hole fiber 5-3 used in this embodiment is shown in fig. 3, which is a biased dual-core single-hole fiber, wherein the diameters of the two fiber cores are the same, the diameter of the air hole 5-3-1 is much larger than the diameter of the fiber core, and the distance between the air hole 5-3-1 and one of the fiber cores 5-3-2 is about 1 micron, so that the change of the refractive index of the liquid in the air hole can effectively affect the light transmitted along the fiber core, and the distance between the two fiber cores is 27 microns, so that the light transmitted along the two fiber cores is not affected by each other. The air holes are in a straight line with the two fiber cores, so that the liquid filled in the air holes only affects the fiber core 5-3-2 adjacent to the air holes, and does not affect the other fiber core 5-3-3. The structure of the used bias twin-core fiber is shown in fig. 4, which has the same core diameter and the same core pitch as the twin-core single-hole fiber.
And liquid in the double-core single-hole optical fiber is filled after the two ends of the double-core single-hole optical fiber are welded with the double-core optical fiber. Firstly, manufacturing two microgrooves with air holes communicated with the outside on a cladding on one side of the air hole of the double-core single-hole optical fiber by methods of laser etching, heating hole blowing, chemical corrosion and the like, as shown in figure 5, wherein 5-3-4 and 5-3-5 are two microgrooves, then dripping liquid to be filled on the microgrooves on one side, completing filling by utilizing siphon of the liquid, and finally, plugging the two microgrooves by using ultraviolet glue.
After connecting the light source, the spectrum analyzer and other parts in sequence, manufacturing the optical fiber cone, welding the single-mode optical fiber and the double-core optical fiber, performing fusion tapering at a welding spot to complete manufacturing of the optical fiber cone, controlling the length of the tapered cone through the spectrum analyzer in the tapering process, and stopping tapering when an obvious interference spectrum is seen on the spectrum analyzer.
When light emitted by the light source is transmitted to the optical fiber cone through the optical circulator, the light is divided into two beams, one beam is transmitted along the fiber core of the double-core optical fiber close to the air hole, the other beam is transmitted along the fiber core of the double-core optical fiber without being influenced by the air hole, the other beam is reflected through the reflecting film on the end face, the two beams of light are transmitted back along the path when coming, interference occurs at the position of the optical fiber cone, the interference light is transmitted to the optical spectrum analyzer through the optical circulator, and therefore the output spectrum can be obtained. When the temperature changes, the refractive index of the liquid filled in the holes of the dual-core single-hole optical fiber changes, so that the effective refractive index of the fiber core affected by the air holes changes, and therefore, the optical path difference of light transmitted along the two fiber cores changes, which causes the interference spectrum to change, and when the length of the used dual-core single-hole optical fiber is 1 cm, the interference spectra at different temperatures are shown in fig. 6. The temperature measurement can be realized by measuring the shift of the interference peak, and the change curve of the wavelength of the interference peak along with the temperature is shown in figure 7.
Claims (8)
1. A temperature sensor based on a double-core single-hole optical fiber. The light source 1 is used as an incident end and is connected with a port 1 of an optical circulator 3 through a single mode fiber 2-1, the port 2 of the optical circulator 3 is connected with an optical fiber sensing probe 5 through the single mode fiber 2-2, and the port 3 of the optical circulator 3 is used as an output end and is connected with a spectrum analyzer 4 through the single mode fiber 2-3. The optical fiber sensing probe 5 is composed of a Michelson interferometer, and the Michelson interferometer comprises a single-mode optical fiber, an optical fiber cone, a double-core optical fiber, a double-core single-hole optical fiber filled with high thermo-optic coefficient liquid in a hole and a reflecting film. The two ends of the double-core single-hole optical fiber are respectively welded with a section of double-core optical fiber in a core-to-core mode, the double-core optical fiber at one end is welded with the single-mode optical fiber in a core-to-core mode, the end face of the double-core optical fiber at the other end is plated with a reflecting film, high-thermal-optical-coefficient liquid is filled in an air hole of the double-core single-hole optical fiber, and the manufacturing of the Michelson interferometer is completed through fusion tapering at the welding position of the single-mode optical fiber. When the temperature changes, the refractive index of liquid filled in the hole changes, so that the effective refractive index of the fiber core of the double-core single-hole optical fiber close to the hole changes, the light transmitted along the two fiber cores generates optical path difference, the interference spectrum changes, and the temperature detection is realized by measuring the drift amount of the interference peak.
2. The dual-core single-hole optical fiber-based temperature sensor according to claim 1, wherein the dual-core optical fiber and the dual-core single-hole optical fiber have the same fiber-core distance, that is, after core-to-core welding, the light energy transmitted along the two fiber cores of the dual-core optical fiber is transmitted along the two fiber cores of the dual-core single-hole optical fiber.
3. The dual-core single-hole optical fiber-based temperature sensor according to claim 1, wherein the liquid filled in the dual-core single-hole optical fiber hole is a liquid with a high thermo-optic coefficient, such as a refractive index matching liquid, a solution of ethanol, glycerol, and the like, and a mixed solution thereof with water.
4. The dual core-single hole fiber based temperature sensor of claim 1, wherein the air holes of the dual core-single hole fiber are sufficiently close to one core that the liquid in the air holes can effectively affect the transmission of light in the fiber core without affecting the other light transmitted along the other fiber core.
5. The dual core single hole fiber based temperature sensor of claim 1, wherein the air holes of the dual core single hole fiber can be in any direction of its adjacent fiber core.
6. The dual core single hole fiber based temperature sensor according to claim 1, wherein the distance between the two fiber cores of the dual core single hole fiber is greater than 10 μm.
7. The dual core single hole optical fiber based temperature sensor according to claim 1, wherein the light source is a broadband light source.
8. The temperature sensor based on the twin-core single-hole optical fiber of claim 1, wherein the reflecting film is a well-cut end face of the optical fiber or a metal reflecting film plated on the end face.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112629704A (en) * | 2020-12-02 | 2021-04-09 | 上海金智晟东电力科技有限公司 | Honeycomb type polarization-maintaining photonic crystal fiber and temperature sensor |
| CN112697339A (en) * | 2020-11-26 | 2021-04-23 | 桂林电子科技大学 | High-strength high-temperature-resistant quick-response optical fiber air pressure sensing probe |
| CN113514164A (en) * | 2021-04-12 | 2021-10-19 | 武汉工程大学 | Michelson interference type temperature sensor based on ultraviolet glue filled core-suspended optical fiber |
| CN113916326A (en) * | 2021-10-05 | 2022-01-11 | 桂林电子科技大学 | Inclined to one side double-core optic fibre level gauge |
| CN114815039A (en) * | 2022-03-30 | 2022-07-29 | 中国船舶重工集团公司第七0七研究所 | Method for manufacturing optical fiber optical fluid channel |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112697339A (en) * | 2020-11-26 | 2021-04-23 | 桂林电子科技大学 | High-strength high-temperature-resistant quick-response optical fiber air pressure sensing probe |
| CN112629704A (en) * | 2020-12-02 | 2021-04-09 | 上海金智晟东电力科技有限公司 | Honeycomb type polarization-maintaining photonic crystal fiber and temperature sensor |
| CN113514164A (en) * | 2021-04-12 | 2021-10-19 | 武汉工程大学 | Michelson interference type temperature sensor based on ultraviolet glue filled core-suspended optical fiber |
| CN113916326A (en) * | 2021-10-05 | 2022-01-11 | 桂林电子科技大学 | Inclined to one side double-core optic fibre level gauge |
| CN114815039A (en) * | 2022-03-30 | 2022-07-29 | 中国船舶重工集团公司第七0七研究所 | Method for manufacturing optical fiber optical fluid channel |
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