CN211085510U - Optical fiber temperature sensor - Google Patents
Optical fiber temperature sensor Download PDFInfo
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- CN211085510U CN211085510U CN201921128737.6U CN201921128737U CN211085510U CN 211085510 U CN211085510 U CN 211085510U CN 201921128737 U CN201921128737 U CN 201921128737U CN 211085510 U CN211085510 U CN 211085510U
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Abstract
The utility model discloses an optic fibre temperature sensor, include: an optical fiber, an inner sheath, and an outer sheath; the inner sheath is wrapped on the optical fiber and made of a low-temperature-resistant thermoplastic elastomer or a low-temperature-resistant thermosetting elastomer, so that the inner sheath still keeps elasticity at low temperature and is used for reducing the influence of shrinkage deformation of the outer sheath material on the optical fiber at low temperature; the outer sheath is wrapped on the inner sheath and used for enhancing the mechanical strength of the optical fiber temperature sensor. The optical fiber temperature sensor and the preparation method thereof provided by the utility model use low temperature resistant silica gel as the inner sheath of the optical fiber, the heat conductivity is good, the elasticity and the softness are kept at low temperature, and the influence of the shrinkage deformation of the outer sheath at low temperature on the optical fiber is effectively eliminated; the low-temperature-resistant tight-sleeved optical fiber temperature sensor is packaged in a non-metal mode, so that electromagnetic interference on devices such as a superconducting cable and a superconducting magnet is avoided, and the insulation performance of the devices is not influenced.
Description
Technical Field
The utility model relates to a low temperature sensor field, more specifically relates to an optic fibre temperature sensor.
Background
The distributed optical fiber temperature measurement method based on Raman scattering has the advantages of high voltage resistance, electromagnetic interference resistance, small optical fiber size, long-distance continuous temperature measurement and the like, so that the distributed optical fiber temperature measurement method based on Raman scattering is widely applied to temperature monitoring and fire alarm of conventional power cables, transformers, petroleum pipelines and the like. Because the optical fiber bare core is fine and easy to break, special packaging is added outside the fiber core to increase the strength of the optical fiber bare core so as to be suitable for practical engineering projects.
In large-scale superconducting power equipment such as a superconducting cable, a superconducting magnet, a superconducting maglev train and the like, a part of a superconducting strip is subjected to quench due to interference factors such as thermal disturbance, and accumulated joule heat can cause the temperature of the strip to rise so that the superconducting equipment fails, so that the temperature along the strip needs to be monitored in real time so as to find the fault of the strip in time and perform protection action. However, the conventional temperature sensors such as thermal resistors cannot be arranged at multiple points along the superconducting tape and are easily subjected to electromagnetic interference. Therefore, the optical fiber temperature sensor which is small in size, can continuously measure temperature in a long distance and is free from electromagnetic interference has obvious advantages in temperature measurement of large superconducting power equipment and receives more and more attention.
At present, the application research of the optical fiber temperature sensor for measuring the temperature distribution along the superconducting tape is still in the experimental stage and is not applied to large-scale commercialization. The reason for this is that the critical temperature (the upper limit temperature for ensuring the zero resistance characteristic) of the superconducting tape is extremely low, and is generally below the liquid nitrogen temperature (-196 ℃). The working temperature of the common temperature measuring optical fiber is more than-60 ℃, the packaging material of the common temperature measuring optical fiber is mostly suitable for high-temperature environments such as fire alarm and the like, the low-temperature resistance performance is poor, the packaging material of the optical fiber is easy to shrink, deform and embrittle under the extremely low-temperature environment of-196 ℃, the shrinkage deformation can generate force effect on the optical fiber core, the optical fiber core is slightly bent and lost and even broken, namely, the temperature measuring performance of the optical fiber at the low temperature of-196 ℃ is unstable and unreliable.
Therefore, an optical fiber temperature sensor capable of resisting extremely low temperature is needed to solve the problems and meet the temperature measurement requirement of large-scale superconducting power equipment.
SUMMERY OF THE UTILITY MODEL
To prior art's defect, the utility model discloses an aim at solves current optic fibre temperature sensor and easy shrink deformation and the embrittlement of packaging material of optic fibre under the extremely low temperature environment, and its shrink deformation can lead to the fine bending loss of fibre core to the effect of optic fibre core production force to split even for optic fibre temperature measurement performance is unstable, unreliable technical problem under the low temperature.
In order to achieve the above object, the present invention provides an optical fiber temperature sensor, including: an optical fiber, an inner sheath, and an outer sheath;
the inner sheath is wrapped on the optical fiber and made of a low-temperature-resistant thermoplastic elastomer or a low-temperature-resistant thermosetting elastomer, so that the inner sheath still keeps elasticity at low temperature and is used for reducing the influence of shrinkage deformation of the outer sheath material on the optical fiber at low temperature;
the outer sheath is wrapped on the inner sheath and used for enhancing the mechanical strength of the optical fiber temperature sensor.
Optionally, the surface layer of the optical fiber is coated with a low temperature resistant material.
Optionally, the low temperature resistant material coated on the surface layer of the optical fiber is polyimide or acrylate.
Optionally, the thermosetting elastomer is low temperature resistant silica gel, and the low temperature resistant silica gel has the characteristics that the low temperature resistant silica gel still has elasticity and adhesive force at the temperature of-196 ℃ and below.
Optionally, the low-temperature-resistant silica gel is a single-component room-temperature vulcanized silicone rubber, namely nanda 703 silicone rubber, the single-component room-temperature vulcanized silicone rubber contains two fillers, namely silicon dioxide and polydimethylsiloxane with hydroxyl at the tail end, and the single-component room-temperature vulcanized silicone rubber still has elasticity and adhesive force at the temperature of-253 ℃.
Optionally, the outer sheath is a fiber optic plastic sleeve.
Generally, through the utility model discloses above technical scheme who conceives compares with prior art, has following beneficial effect:
1) the utility model provides an optical fiber temperature sensor, its whole optical fiber temperature sensor adopt nonmetal encapsulation, can not produce electromagnetic interference, do not influence device insulating properties to devices such as superconducting cable, superconducting magnet.
2) The utility model provides an optic fibre temperature sensor uses low temperature resistant silica gel as optic fibre inner sheath, and its heat conductivility is good, keep elasticity and compliance under the low temperature, has effectively subducted the influence of outer sheath low temperature shrinkage deformation to optic fibre.
3) The utility model provides an optical fiber temperature sensor, the plastics oversheath of secondary cladding can effectively increase optic fibre mechanical strength, can arrange on superconducting coil, superconducting cable more in a flexible way for metal package optic fibre.
Drawings
Fig. 1 is a schematic view of the packaging structure of the ultralow temperature resistant optical fiber temperature sensor provided by the present invention;
fig. 2 is a flowchart of a method for manufacturing an optical fiber temperature sensor according to the present invention;
FIG. 3 is a schematic view of the configuration structure of the optical fiber production line provided by the present invention;
FIG. 4a is a schematic view of a temperature measurement curve of a conventional Teflon tightly-sleeved optical fiber temperature sensor and the very low temperature resistant optical fiber temperature sensor of the present invention at a liquid nitrogen temperature;
FIG. 4b is a schematic view of the Raman ratio variation curve along the line of the ordinary Teflon tightly-sleeved optical fiber temperature sensor and the extreme low temperature resistant optical fiber temperature sensor of the present invention at the liquid nitrogen temperature;
fig. 5a is a schematic diagram of a temperature variation curve of the very low temperature resistant optical fiber temperature sensor of the present invention during a temperature rising process;
fig. 5b is a schematic diagram of a raman ratio-temperature curve of the very low temperature resistant optical fiber temperature sensor of the present invention during temperature rise;
throughout the drawings, the same reference numerals are used to designate the same elements or structures, wherein 1 is an optical fiber, 2 is an inner sheath, and 3 is an outer sheath.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features mentioned in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
In order to solve the problems, the utility model designs a tight-buffered optical fiber temperature sensor which can resist extremely low temperature (the temperature of liquid nitrogen is below 196 ℃ below zero), and introduces a preparation method thereof.
The utility model discloses a realize through following technical scheme.
The utility model provides a resistant extremely low temperature tight tube optical fiber temperature sensor, its structure includes:
an optical fiber core, said optical fiber core being an 50/125 μm multimode, once coated optical fiber; the inner sheath is wrapped on the optical fiber, the used material has excellent low-temperature resistance, and the shrinkage deformation and embrittlement at low temperature hardly affect the fiber core of the optical fiber; the outer sheath is used for enhancing the mechanical strength of the temperature measuring optical fiber and is made of common optical fiber plastic sleeve materials.
The optical fiber is a single-core and multi-mode communication-grade 50/125 mu m optical fiber, and is coated with a special low-temperature-resistant material such as polyimide or acrylic ester, so that the optical fiber can normally measure the temperature at the liquid nitrogen temperature.
The low temperature resistant material is preferably polyimide, and can increase the temperature sensitivity of the optical fiber at low temperature.
The inner sheath is a thermoplastic or thermosetting low-temperature-resistant elastomer, can still keep certain elasticity and softness at the extremely low temperature of-196 ℃, and can effectively reduce the influence of shrinkage deformation of the optical fiber outer sheath packaging material on the optical fiber at low temperature.
The inner protective sleeve plays a role in buffering between the optical fiber and the outer sheath, and influences of expansion with heat and contraction with cold on the fiber core of the outer sheath are isolated. The inner sheath is preferably a thermoset elastomer. The thermosetting elastomer can be low-temperature-resistant silica gel, is required to have elasticity, better adhesive force and certain softness at the temperature of-196 ℃ and below, and can effectively reduce the influence of shrinkage deformation of the outer sheath on the optical fiber at low temperature.
The inner sheath is specifically low-temperature-resistant single-component room-temperature vulcanized silicone rubber, the single-component room-temperature vulcanized silicone rubber is 703 silicone rubber, and the single-component room-temperature vulcanized silicone rubber contains silicon dioxide, polydimethylsiloxane with hydroxyl at the tail end, other fillers and a curing agent. Experiments prove that the superconducting magnet can still keep better adhesion and elasticity in a superconducting magnet at-253 ℃ and extremely low temperature environment, and can be used as a low temperature resistant optical fiber inner sheath.
The outer sheath is a common optical fiber plastic sleeve and aims to enhance the mechanical strength of the optical fiber, and the shrinkage deformation and embrittlement at low temperature do not cause microbending loss of the optical fiber due to the buffering effect of the inner sheath.
The outer sheath is preferably a Teflon plastic sleeve, has a wide temperature resistance range and still has certain adhesive force at low temperature.
The preparation method of the extremely low temperature resistant tight-buffered optical fiber temperature sensor is provided by combining the components, and comprises the following steps:
1. the optical fiber on the optical fiber pay-off rack passes through an optical fiber preheating device;
2. the preheated optical fiber passes through an extruding machine, the extruding machine extrudes the melted low-temperature-resistant single-component room-temperature vulcanized silicone rubber, and the optical fiber drives the silicone fluid to leave an extruding machine head;
3. the optical fiber enters a hot/cold water tank after leaving the extrusion molding machine head to finish cooling and shaping of the silica gel fluid;
4. drying the cooled optical fiber by using a blow dryer to finish one-time coating of the optical fiber (finishing of the inner sheath);
5. detecting whether the outer diameter of the optical fiber reaches the standard by using a diameter measuring instrument, and completing optical fiber take-up by using a take-up device;
6. changing the size of a mould of the plastic extruding machine, changing the low-temperature silica gel fluid in the steps 2 and 3 into a Teflon plastic fluid, and repeating the steps 1 to 5 to finish the secondary coating of the optical fiber (finishing the outer sheath);
7. and after the take-up is finished, detecting the appearance, the size and the optical performance of the optical fiber to check whether the product is qualified.
Preferably, the preheating device of the optical preheating device in the step 1 needs to be slightly lower than the melting temperature of the extrusion molding materials (low-temperature silica gel and teflon);
preferably, the extruder used in step 2 is a conventional single-screw extruder, and the screw is a conventional three-stage screw.
It should be noted that the temperature setting of the extruder in step 2 is determined according to the specific materials used, i.e. the temperature setting of the extruder is different when the inner sheath (primary coating) and the outer sheath (secondary coating) are coated, see the examples.
Preferably, in the steps 2 and 3, in order to reduce the shrinkage of the inner jacket material and the outer jacket material after molding and to suppress excessive residual stress, the air gap between the extrusion molding machine head and the hot/cold water tank is appropriately increased by about 250 mm.
Preferably, in step 3, in order to reduce the stress of the material during cooling shrinkage, the hot/cold water tank is cooled in stages by using hot water and cold water, and the temperature of the hot water is not lower than 60 ℃.
Preferably, the pulling speed of the take-up device in the step 5 is set according to the packaging material, the pulling speed after the first coating is set to 370/200 (revolutions per minute), and the pulling speed after the second coating is set to 382/230 (revolutions per minute).
As shown in fig. 1, the structure of the optical fiber temperature sensor provided in this embodiment includes: the optical fiber 1 is coated with a special low-temperature resistant material and can normally transmit optical signals at low temperature of liquid nitrogen; the inner sheath 2 is directly bonded with the fiber core of the optical fiber and serves as a buffer layer between the fiber core 1 and the outer sheath 3, so that the influence of the shrinkage deformation of the outer sheath 3 on the fiber core 1 at low temperature is reduced; the outer sheath 3, whose main function is to reinforce the mechanical strength of the optical fiber.
The optical fiber 1 is a single-core and multi-mode communication-grade 50/125 μm optical fiber, polyimide is preferably used as a coating material in the embodiment, and the temperature sensitivity of the optical fiber at low temperature can be increased.
The inner sheath 2 is a thermoplastic or thermosetting elastomer, keeps elasticity and softness at low temperature, and plays a buffering role between the outer sheath and the optical fiber, and in the embodiment, low-temperature-resistant single-package room-temperature vulcanized silica gel is preferably selected, and is composed of filler such as polydimethylsiloxane, silicon dioxide and the like with hydroxyl at the tail end and a special curing agent.
The outer sheath 3 is a plastic sleeve, so that the mechanical strength of the temperature measuring optical fiber can be effectively enhanced, and in the embodiment, Teflon is preferably used as the outer sheath.
Fig. 2 is a flowchart of a method for manufacturing an optical fiber temperature sensor, as shown in fig. 2, including the following steps:
s101, preheating an optical fiber;
s102, coating the preheated optical fiber with a molten low-temperature-resistant thermoplastic elastomer or a low-temperature-resistant thermosetting elastomer to serve as an inner sheath wrapped on the optical fiber;
s103, coating the melted material of the outer sheath on the inner sheath to obtain the optical fiber temperature sensor, wherein the outer sheath is used for enhancing the mechanical strength of the optical fiber temperature sensor.
In one example, the present embodiment provides a very low temperature resistant optical fiber temperature sensor, which is prepared by the following steps:
1. an optical fiber 1 on the optical fiber pay-off rack passes through an optical fiber preheating device;
since the temperature of the thermoplastic polymer in the extruder is high during extrusion, the polymer is cooled too early if it is in direct contact with the optical fiber 1 without preheating, and the polymer is unevenly shrunk on the surface of the optical fiber 1 to cause stress. Therefore, the optical fiber 1 needs to be subjected to a preheating process at a temperature slightly lower than the melting temperature of the material.
2. The preheated optical fiber 1 passes through an extruding machine, the extruding machine extrudes the melted low-temperature-resistant silica gel fluid, and the optical fiber 1 drives the silica gel fluid to leave an extruding machine head;
when once coating low temperature resistant silica gel, the temperature of each position of extruding machine sets up to:
when the secondary is coated with the teflon, the temperature of each part of the extruding machine is set as follows:
3. the optical fiber enters a hot/cold water tank after leaving the extrusion molding machine head to finish cooling and shaping of the silica gel fluid;
in order to reduce the stress of the material during cooling shrinkage, the hot/cold water tank is cooled by hot water and cold water in a sectional manner, and the temperature of the hot water is not lower than 60 ℃.
4. Drying the cooled optical fiber by using a blow dryer to finish one-time coating of the optical fiber (finishing of the inner sheath);
5. detecting whether the outer diameter of the optical fiber reaches the standard by using a diameter measuring instrument, and completing optical fiber take-up by using a take-up device;
at the time of one coating, the drawing speed was set to 370/200 (revolutions per minute);
at the time of the second coating, the drawing speed was set to 382/230 (revolutions per minute).
6. Changing the size of a mould of the plastic extruding machine, changing the low-temperature silica gel fluid in the steps 2 and 3 into a Teflon plastic fluid, and repeating the steps 1 to 5 to finish the secondary coating of the optical fiber (finishing the outer sheath);
7. and after the take-up is finished, detecting the appearance, the size and the optical performance of the optical fiber to check whether the product is qualified.
Will the utility model provides a tight set of optical fiber temperature sensor of resistant utmost point low temperature and ordinary teflon tightly cover optical fiber temperature sensor together place and carry out temperature measurement in liquid nitrogen (-196 ℃), and the raman ratio variation curve along the line of gained temperature measurement curve and optic fibre is shown as figure 4a and figure 4b, will be resistant utmost point low temperature optical fiber temperature sensor and ordinary teflon tightly cover optic fibre and respectively get 28m (33 ~ 62m region) and place in the liquid nitrogen: in fig. 4a, the temperature measurement value of the ordinary teflon tight-buffered optical fiber at the position 31m is suddenly changed to-273 ℃, and the temperature measurement value is seriously deviated from the accurate value (-196 ℃), while the corresponding raman ratio value of the optical fiber at the position 31m in fig. 4b is suddenly changed to 0, which indicates that the ordinary teflon optical fiber at the position 31m is broken, and the optical signal cannot be transmitted, so that the temperature measurement value is seriously deviated. The reason for causing the severe deviation of the broken optical fiber is mainly that the Teflon can shrink violently in the low-temperature environment of-196 ℃ and produce shrinkage stress on the optical fiber, so that the optical fiber is bent to generate cracks and even is broken; and the utility model provides a resistant utmost point low temperature optic fibre temperature sensor is normal temperature measurement then, in this sensor, because inner sheath-resistant low temperature silica gel have certain elasticity and softer at low temperature, subducted the shrink deformation of oversheath-teflon effectively and to the influence of optic fibre, guarantee that optic fibre can normal temperature measurement at low temperature.
As shown in FIG. 5a, in the dynamic temperature rise process of-196-24 ℃, the temperature measurement effect of the extreme low temperature resistant tightly-sleeved optical fiber temperature sensor produced by the design is consistent with that of a PT100 platinum resistor, and the temperature measurement precision is higher; fig. 5b shows that the raman ratio of the optical signal in the cryogenic-resistant tight-buffered optical fiber temperature sensor produced by the design changes with the change of temperature and has higher temperature sensitivity, which indicates that the cryogenic-resistant optical fiber temperature sensor produced by the design has stable and reliable temperature measurement performance and meets the requirement of temperature monitoring of devices such as superconducting cables and superconducting magnets under cryogenic temperature.
The utility model provides a tight set optic fibre temperature sensor of resistant utmost point low temperature, including optic fibre, low temperature silica gel inner sheath, teflon oversheath. The extreme low temperature resistant tight-buffered optical fiber temperature sensor can be used for monitoring the temperature of large superconducting power equipment such as superconducting cables, superconducting magnets and the like in an extreme low temperature environment below 196 ℃. The preparation method comprises the steps of firstly introducing the preheated optical fiber into an extruding machine to be coated with low-temperature silica gel fluid, then enabling the optical fiber to enter a hot/cold water tank to finish cooling and shaping of the inner sheath-low-temperature silica gel, and then using a diameter gauge to check the size of the optical fiber to finish the packaging of the primary coating-low-temperature silica gel inner sheath; and (3) filling a Teflon fluid into the extruding machine, changing the temperature setting of the extruding machine, and repeating the steps to finish the packaging of the secondary coating-Teflon outer sheath. The low-temperature-resistant tight-sleeved optical fiber temperature sensor is packaged in a non-metal manner, so that electromagnetic interference on devices such as a superconducting cable and a superconducting magnet is avoided, and the insulation performance of the devices is not influenced; the low-temperature-resistant silica gel is used as the optical fiber inner sheath, the thermal conductivity is good, the elasticity and the softness are kept at low temperature, and the influence of the shrinkage deformation of the outer sheath at low temperature on the optical fiber is effectively reduced; the Teflon plastic outer sheath coated for the second time can effectively increase the mechanical strength of the optical fiber, and can be more flexibly arranged on a superconducting coil and a superconducting cable compared with a metal-encapsulated optical fiber.
It will be understood by those skilled in the art that the foregoing is merely a preferred embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A fiber optic temperature sensor, comprising: an optical fiber, an inner sheath, and an outer sheath;
the inner sheath is wrapped on the optical fiber and made of a low-temperature-resistant thermoplastic elastomer or a low-temperature-resistant thermosetting elastomer, so that the inner sheath still keeps elasticity at low temperature and is used for reducing the influence of shrinkage deformation of the outer sheath material on the optical fiber at low temperature;
the outer sheath is wrapped on the inner sheath and used for enhancing the mechanical strength of the optical fiber temperature sensor.
2. The optical fiber temperature sensor according to claim 1, wherein the surface layer of the optical fiber is coated with a low temperature resistant material.
3. The optical fiber temperature sensor according to claim 2, wherein the low temperature resistant material coated on the surface of the optical fiber is polyimide or acrylate.
4. The optical fiber temperature sensor according to any one of claims 1 to 3, wherein the thermosetting elastomer is a low temperature resistant silicone rubber having such properties that the low temperature resistant silicone rubber has elasticity and adhesive force at a temperature of-196 ℃ or less.
5. The optical fiber temperature sensor according to claim 4, wherein the low temperature resistant silicone rubber is a one-component room temperature vulcanized silicone rubber, also known as Nada 703 silicone rubber, which comprises two fillers of silica and polydimethylsiloxane with hydroxyl group at the terminal, and the one-component room temperature vulcanized silicone rubber still has elasticity and adhesion at a temperature of-253 ℃.
6. The fiber optic temperature sensor of claim 4, wherein the outer jacket is a fiber optic plastic sleeve.
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| CN201921128737.6U CN211085510U (en) | 2019-07-17 | 2019-07-17 | Optical fiber temperature sensor |
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| CN201921128737.6U CN211085510U (en) | 2019-07-17 | 2019-07-17 | Optical fiber temperature sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110307914A (en) * | 2019-07-17 | 2019-10-08 | 华中科技大学 | A kind of fibre optic temperature sensor and preparation method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110307914A (en) * | 2019-07-17 | 2019-10-08 | 华中科技大学 | A kind of fibre optic temperature sensor and preparation method thereof |
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