CN210572929U - Ultra-weak fiber grating optical cable for water temperature monitoring - Google Patents
Ultra-weak fiber grating optical cable for water temperature monitoring Download PDFInfo
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- CN210572929U CN210572929U CN201921678666.7U CN201921678666U CN210572929U CN 210572929 U CN210572929 U CN 210572929U CN 201921678666 U CN201921678666 U CN 201921678666U CN 210572929 U CN210572929 U CN 210572929U
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Abstract
An ultra-weak fiber grating optical cable applied to water temperature monitoring comprises: the ultra-weak fiber grating array is positioned in the center; the grease layer is uniformly covered on the ultra-weak fiber grating array along the axial direction; a metal tube wrapping the ultra-weak fiber grating array and the periphery of the grease layer; a reinforcement member wrapped in a helical form by twisting around the metal pipe; a sensor mark coated on the exterior of the stiffener. The grating optical cable adopts the metal tube to directly package the ultra-weak fiber grating array, and a small amount of factice is filled along the grating array, so that the accumulated distribution of the excess length of the optical fiber is inhibited, and the influence of residual strain in the sensing optical fiber is reduced or eliminated while the optical fiber is prevented from being infiltrated by water vapor. The linear correlation degree of a calibrated temperature curve of the ultra-weak fiber grating temperature-sensing optical cable manufactured by the method reaches more than 0.999, and the fluctuation of the temperature sensitivity is less than 0.3 pm/DEG C.
Description
Technical Field
The utility model relates to a fiber optic cable temperature sensing field, concretely relates to super weak fiber grating optical cable for temperature monitoring.
Background
The water temperature is an important parameter for representing the water body environment. The monitoring of the change of the water temperature and the gradient distribution thereof has important guiding significance in the fields of water conservancy dispatching, environment protection, aquatic product fishing, channel maintenance, hydraulic construction site selection and the like. The optical fiber sensor has the remarkable advantages of no self-heating, electromagnetic interference resistance, high sensitivity, light weight, flexibility, multi-parameter composite sensing, large-space distributed measurement and the like, and has wide application prospect in the field of water temperature monitoring.
At present, the optical fiber sensing technology applied to water temperature monitoring mainly comprises two types, namely distributed optical fiber sensing (DTS) based on scattering (Raman scattering or Brillouin scattering) and optical fiber sensing based on high-reflectivity grating (FBG). The former has the problems of low spatial resolution, incapability of point-mode temperature measurement, complex data demodulation and the like; the sensor has less multiplexing number, and the sensing units are mostly coated after peeling and writing, so the coating uniformity is poor and the temperature linearity is poor. The ultra-weak fiber grating has extremely low reflectivity, and can realize intensive point type temperature measurement through time division/wavelength division multiplexing, thereby greatly improving the multiplexing number and the spatial resolution of the sensing units.
The common ultra-weak fiber grating array is relatively weak, and is calibrated and transported by winding a metal tubular armored packaging structure. When the optical cable is coiled, the radius of the optical fiber coiling disk positioned in the tube is slightly larger than that of the coiling disk of the inner ring of the metal tube, after the optical fiber and the metal tube with equal length are coiled for a plurality of circles, the optical fiber can be obviously elongated due to insufficient length, and the temperature characteristic of the grating is influenced due to the existence of strain caused by the elongation. If the extra length of the optical fiber is reserved before coiling, when the optical cable is straightened, the extra length needs to be released, but friction exists between the optical fiber and the tube wall, and the friction resistance can cause secondary distribution of the extra length, so that the sensitivity and the linearity of the sensing optical cable are influenced. Extensive experimental studies have shown that the cumulative temperature measurement error measured at the sensing point is greater than 1 deg.C when the residual strain on the fiber is greater than 50. mu. epsilon. In addition, the water temperature monitoring optical cable not only needs higher temperature measurement precision, but also needs to consider the problem of water vapor infiltration, and the traditional waterproof factice filling process limits the movement of the grating in the metal tube and is easy to generate strain influence. Therefore, when the ultra-weak fiber bragg grating array is cabled, how to avoid the influence of stress from the physical structure and improve the waterproof performance of the grating is a difficult problem to be solved urgently by the water temperature monitoring optical cable.
Chinese patent "a temperature sensing optical cable of stress-free grating array and its sensing method, application number: 201710457903.6, it is proposed to pre-bond the stress optical fiber and the stress-free optical fiber, and then package them into cable, and to ensure the stress-free measurement of the sensing optical fiber by the stress generated by the change of the bearing allowance of the stress optical fiber.
Chinese patent "a skeleton fiber grating temperature sensing optical cable, application number: 201821650447.3 "; "a fiber grating temperature strain hybrid optical cable, application No.: 201811185773.6' to alleviate the influence of stress by adhering optical fibers to special structures in sections, which are feasible but difficult to be automatically produced, and complicated special structures can reduce the response speed of temperature and influence the temperature measurement precision. In addition, when the sensing optical cable is used in a water environment for a long time, the stability of the sensor can be influenced by the moisture infiltration, and the design of the optical cable can not meet the requirement of water environment monitoring.
Disclosure of Invention
The temperature-sensing optical cable aims at solving the problems that the existing temperature-sensing optical cable is complex in structure, low in temperature-sensing precision, poor in waterproofness and the like. The utility model provides a be applied to super weak fiber grating optical cable of temperature monitoring, this grating optical cable adopt the direct encapsulation of tubular metal resonator to surpass weak fiber grating array, through filling a small amount of oleamen along the grating array, restrain the accumulation distribution of the extra length of optic fibre, when preventing that steam from infiltrating optic fibre, reduce or eliminate the influence of residual strain in the sensing optic fibre. The ultra-weak fiber grating temperature-sensing optical cable manufactured by the method has the advantages that the linear correlation degree of a calibrated temperature curve reaches more than 0.999, the temperature sensitivity fluctuation is less than 0.3 pm/DEG C, the absolute temperature in a water body can be reliably measured for a long time, and the ultra-weak fiber grating temperature-sensing optical cable has a good application prospect in the field of water temperature monitoring.
The utility model discloses the technical scheme who takes does:
an ultra-weak fiber grating optical cable applied to water temperature monitoring comprises:
the ultra-weak fiber grating array is positioned in the center;
the grease layer is uniformly covered on the ultra-weak fiber grating array along the axial direction;
a metal tube wrapping the ultra-weak fiber grating array and the periphery of the grease layer;
a reinforcement member wrapped in a helical form by twisting around the metal pipe;
a sensor mark coated on the exterior of the stiffener.
The ultra-weak fiber grating array comprises a single-layer coating layer, and the thickness of the single-layer coating layer is less than 30um
The ultra-weak fiber grating array comprises a plurality of wavelength division/time division multiplexing ultra-weak fiber grating sensing units with the reflectivity lower than 0.1%, the full width at half maximum of the grating spectrum is less than 0.3nm, and the grating interval is less than 1 meter.
The ointment layer adopts waterproof ointment, and the filling height is 1/3 of the radius height of the metal pipe.
Compared with a metal tube, the ultra-weak fiber grating array is reserved with a certain length.
The metal tube is made of stainless steel and is formed by laser seamless welding.
The reinforcing piece is preferably made of spring stainless steel wires for long-distance heavy-load occasions; for short distance light load applications with high linearity requirements, soft stainless steel wires are preferred.
Sensor marks with the length of 20mm and the diameter of 5mm are coated on the outer diameter of the optical cable at the position of the grating sensing point and are used for identifying the position and the wavelength of the sensor.
The utility model discloses an ultra-weak fiber grating optical cable for temperature monitoring has following beneficial effect:
1) reduce or eliminate the influence of meeting an emergency to the temperature, promote the temperature sensing precision:
by filling a small amount of ointment along the grating array, the accumulated distribution of the excess length of the optical fiber is inhibited, the influence of residual strain in the sensing optical fiber is reduced or eliminated, the technical problem of stress concentration caused by excess length redistribution is overcome, the uniform stress-free packaging of the grating is really realized, and the temperature measurement precision is ensured. In addition, the metal package has large heat conductivity coefficient and small diameter, so that the sensor has higher response speed and thermal sensitivity and can be used for measuring dynamic temperature.
2) Good water resistance, and is easy to be used in water environment for a long time:
the ultra-weak fiber grating array is welded by metal pipes in a seamless mode, and direct contact with a water body is avoided. The metal tube is filled with factice, so that the optical fiber is prevented from being exposed in the air, the infiltration of water vapor can be resisted for a long time, and the service life of the optical fiber is prolonged.
3) The optical cable is calibrated conveniently and is easy to transport in a coil:
for the temperature sensing optical cable, the linearity and the sensitivity are calibrated after the full-array winding is needed before the temperature sensing optical cable is used, after the traditional optical cable is wound, the surplus length can be redistributed, and the problems of nonlinearity, hysteresis, repeatability and the like can be caused by the generated stress strain. After the waterproof factice is filled, the optical cable is matched with a proper extra length, so that the optical cable is not subjected to large strain during winding, and the calibration accuracy is further ensured. In addition, the optical cable can be coiled by adopting a common process, the linearity and the precision of temperature measurement are not influenced after the optical cable is wound, and the transportation is convenient.
4) Simplify the optical cable structure, easily automatic batch:
aiming at the characteristics of the ultra-weak fiber bragg grating, the optical cable is optimally designed, the structure is simple, the mass production is convenient, the production efficiency is high, the cost is low, the cost performance is high, and the popularization and the application in water temperature monitoring occasions are convenient.
Drawings
Fig. 1 is a schematic cross-sectional structure view of the ultra-weak fiber grating optical cable of the present invention;
wherein: 1 is an ultra-weak fiber grating array; 2 is an ointment layer; 3 is a metal tube; 4 is a reinforcing member; and 5, a sensor mark.
Fig. 2 is a schematic cross-sectional structure diagram of the temperature-sensing ultra-weak fiber grating array of the present invention;
wherein: 6 is an ultra-weak fiber grating sensing unit; 7 is an optical fiber cladding; and 8 is a single coating layer.
FIG. 3 is a graph showing the temperature characteristics of the fiber grating according to the present invention;
in fig. 3, the linearity of the randomly extracted grating is 0.9999 or more.
FIG. 4 is a graph showing the consistency of the temperature-sensitive coefficients of the grating according to the present invention;
in FIG. 4, the temperature sensitivity coefficient of 10 randomly extracted gratings is 10.4-11.0 pm/deg.C.
Detailed Description
An ultra-weak fiber grating optical cable applied to water temperature monitoring comprises:
the ultra-weak fiber grating array 1 is positioned in the center;
a small amount of grease layers 2 uniformly cover the ultra-weak fiber grating array 1 along the axial direction;
a metal pipe 3 wrapping the ultra-weak fiber grating array 1 and the periphery of the ointment layer 2;
a reinforcing member 4 wrapped in a helical form by twisting around the metal pipe 3;
a sensor mark 5 coated on the outside of the reinforcement 4.
The ultra-weak fiber grating array 1 comprises a single-layer coating layer 8 with low elastic modulus, the thickness of the coating layer is less than 30um, modified acrylate is preferably selected, and no obvious glass transition temperature point exists at-25-100 ℃. The traditional fiber grating adopts double-layer coating, the temperature nonlinear characteristic of a coating layer material influences the temperature sensing characteristic of the grating, a single-layer coating layer 8 with low elastic modulus is adopted, the thickness of the coating layer is reduced to 30um, and experiments prove that the influence of the coating layer can be effectively overcome, so that the ultra-weak fiber grating array 1 obtains excellent linearity.
The ultra-weak fiber grating array 1 comprises a plurality of wavelength division/time division multiplexing ultra-weak fiber grating sensing units 6 with the reflectivity lower than 0.1%, the full width at half maximum of the grating spectrum is less than 0.3nm, and the grating interval is less than 1 meter. The design combines the time division/wavelength division technology of the fiber bragg grating, the space of the sensing units can be flexibly customized according to the space interval requirement of temperature measurement, and a long-distance high-spatial-resolution temperature chain can be formed. For example, when the reflected signal of the ultra-weak fiber grating array is demodulated, the signal resolution in the time domain is only 1.5 m-2 m limited by the response speed of the acquisition card, but by interleaving different wavelengths in the space, i.e. frequency division multiplexing is performed, if 10 wavelengths are inserted, the spatial resolution of time division/frequency division can reach the precision of 0.15-0.2 m, which can meet the requirements of most high-precision and high-resolution monitoring. The reflectivity of the ultra-weak fiber grating array 1 is lower than 0.1%, the full width at half maximum of the grating spectrum is smaller than 0.3nm, the optimal wavelength demodulation effect can be obtained, the wavelength demodulation precision reaches 0.5pm, and the temperature demodulation precision of 0.05 ℃ is obtained.
The ointment layer 2 is waterproof ointment, preferably ointment with medium viscosity, and the filling height is about 1/3 of the radius height of the metal pipe 3. If the metal tube 3 is filled with the factice to be overfilled, additional tension is generated on the grating after the factice is heated and expanded, and the temperature measurement precision is influenced.
Compared with the metal tube 3, the ultra-weak fiber grating array 1 has the extra length of 0.1 to 0.6 percent according to different coiled diameters. The extra length is 0.1 to 0.6 percent of the total length of the metal tube 3, and is uniformly distributed in the whole metal tube 3 to avoid that the ultra-weak fiber grating array 1 bears overlarge stress when the optical cable is coiled or laid. For arrays with small coil diameters, a small margin is preferred.
The metal pipe 3 is made of stainless steel or other materials, adopts laser seamless welding, and has a diameter smaller than 2.0 mm.
The reinforcing piece 4 is preferably made of stainless steel wires according to the requirements of tensile strength and bending strength, and is preferably made of spring stainless steel wires for long-distance heavy-load occasions; for short distance light load applications with high linearity requirements, soft stainless steel wires are preferred.
The outer diameter of the optical cable at the position of the grating sensing point is coated with a sensor mark 5 with the length of 20mm and the diameter of 5mm, and the sensor mark 5 is used for identifying the position and the wavelength of the sensor, and the sensor mark 5 is preferably red, blue, green and other striking colors.
The utility model provides a simple, the temperature sensing is effectual, easily mark, the optical fiber cable that the temperature monitoring that water-proof effects is good of preparation technology used, through covering a small amount of oleamen along the super weak fiber grating array 1, restraines the cumulative distribution of optic fibre extra length, when preventing that steam from infiltrating optic fibre, reduces or eliminates the influence of residual strain in the sensing optic fibre. The ultra-weak fiber grating temperature-sensing optical cable manufactured by the method has the advantages that the linear correlation degree of a calibrated temperature curve reaches more than 0.999, the temperature sensitivity fluctuation is less than 0.3 pm/DEG C, the absolute temperature in a water body can be reliably measured for a long time, and the ultra-weak fiber grating temperature-sensing optical cable has a good application prospect in the field of water temperature monitoring.
Claims (8)
1. The utility model provides an ultra-weak fiber grating optical cable for temperature monitoring which characterized in that includes:
the ultra-weak fiber grating array (1) is positioned in the center;
the grease layer (2) is uniformly covered on the ultra-weak fiber grating array (1) along the axial direction;
a metal pipe (3) wrapping the ultra-weak fiber grating array (1) and the periphery of the ointment layer (2);
a reinforcement (4) which is wrapped around the metal tube (3) by twisting in a spiral;
a sensor mark (5) coated on the outside of the reinforcement (4).
2. The ultra-weak fiber grating optical cable applied to water temperature monitoring according to claim 1, wherein: the ultra-weak fiber grating array (1) comprises a single-layer coating layer (8), and the thickness of the single-layer coating layer is smaller than 30 um.
3. The ultra-weak fiber grating optical cable applied to water temperature monitoring according to claim 1, wherein: the ultra-weak fiber grating array (1) comprises a plurality of wavelength division/time division multiplexing ultra-weak fiber grating sensing units (6) with the reflectivity lower than 0.1%, the full width at half maximum of a grating spectrum is less than 0.3nm, and the grating interval is less than 1 meter.
4. The ultra-weak fiber grating optical cable applied to water temperature monitoring according to claim 1, wherein: the ointment layer (2) adopts waterproof ointment, and the filling height is 1/3 of the radius height of the metal pipe (3).
5. The ultra-weak fiber grating optical cable applied to water temperature monitoring according to claim 1, wherein: compared with the metal tube (3), the ultra-weak fiber grating array (1) is reserved with a certain length.
6. The ultra-weak fiber grating optical cable applied to water temperature monitoring according to claim 1, wherein: the metal tube (3) is made of stainless steel and is formed by laser seamless welding.
7. The ultra-weak fiber grating optical cable applied to water temperature monitoring according to claim 1, wherein: the reinforcing piece (4) adopts a spring stainless steel wire for long-distance heavy-load occasions; for short-distance light-load occasions with high linear requirements, soft stainless steel wires are adopted.
8. The ultra-weak fiber grating optical cable applied to water temperature monitoring according to claim 1, wherein: and a sensor mark (5) with the length of 20mm and the diameter of 5mm is coated on the outer diameter of the optical cable at the position of the grating sensing point and is used for identifying the position and the wavelength of the sensor.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113503983A (en) * | 2021-07-05 | 2021-10-15 | 山东飞博赛斯光电科技有限公司 | Fiber grating temperature measurement optical cable |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113503983A (en) * | 2021-07-05 | 2021-10-15 | 山东飞博赛斯光电科技有限公司 | Fiber grating temperature measurement optical cable |
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