CN113686460B - Fiber bragg grating temperature sensor and sensing device based on vernier effect - Google Patents
Fiber bragg grating temperature sensor and sensing device based on vernier effect Download PDFInfo
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- G—PHYSICS
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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
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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Abstract
The invention provides a fiber bragg grating temperature sensor and a sensing device based on vernier effect; the fiber grating temperature sensor comprises an optical fiber, wherein the optical fiber comprises a first area and a second area which are cascaded, the first area is provided with two Bragg fiber grating structures as resonant cavities to form an FBG-FP cavity, the second area is provided with two long-period fiber grating structures to form a double-long-period fiber grating structure, and the FBG-FP cavity and the double-long-period fiber grating structure are cascaded to generate vernier effect; the FBG-FP cavity and the long-period fiber grating structure generate a low-sensitivity structure and a high-sensitivity structure through at least two cascading modes; wherein the structure with low sensitivity is used as a cursor fixing part and the structure with high sensitivity is used as a cursor sliding part. Compared with the traditional Mach-Zehnder interferometer, the dual-LPFG structure is easier to realize, reduces measurement errors, and has higher resolution.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a fiber bragg grating temperature sensor and a sensing device based on vernier effect.
Background
Because of the higher requirements on the sensitivity of the optical fiber temperature sensor in certain special application fields, researchers start to use the vernier effect as a sensitization means, so that the vernier effect is further applied to optical detection and achieves a certain effect.
Various optical cursor structures have been proposed in the prior art, including: the cascade structure of FPI, MZI, FSI, etc., but usually two filters have the same sensitivity, which is disadvantageous for vernier effect generation.
This problem can be solved by combining two interferometers of different sensitivities using a low sensitivity interferometer as the cursor fixed part and a high sensitivity interferometer as the cursor sliding part, but the interferometer influence as a fixed scale still exists and is amplified by the cursor effect. Thus, there are still technical problems that can be solved.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a fiber bragg grating temperature sensor and a sensing device.
In order to achieve the above object, in a first aspect of the present invention, there is provided a fiber grating temperature sensor based on vernier effect, the fiber grating temperature sensor comprising an optical fiber, wherein the optical fiber comprises a first region and a second region which are cascaded, the first region is provided with two bragg fiber grating structures as resonant cavities to form an FBG-FP cavity, the second region is provided with two long period fiber grating structures to form a dual long period fiber grating structure, and the FBG-FP cavity and the dual long period fiber grating structure are cascaded to generate vernier effect; the FBG-FP cavity and the long-period fiber grating structure generate a low-sensitivity structure and a high-sensitivity structure through at least two cascading modes; wherein the structure with low sensitivity is used as a cursor fixing part and the structure with high sensitivity is used as a cursor sliding part.
In the embodiment of the invention, the structural parameters of the two Bragg fiber grating structures are consistent and are separated by a preset distance to form an FBG-FP cavity.
In the embodiment of the invention, the two fiber bragg grating structures are a first fiber bragg grating structure and a second fiber bragg grating structure, the grating lengths of the first fiber bragg grating structure and the second fiber bragg grating structure are 1000 micrometers, the grating period is 0.5358 micrometers, the refractive index modulation depth is 0.00015, and the lengths of the first fiber bragg grating structure and the second fiber bragg grating structure are 3000 micrometers.
In the embodiment of the invention, the two long-period fiber gratings are a first long-period fiber grating and a second long-period fiber grating, the grating lengths of the first long-period fiber grating and the second long-period fiber grating are 50000 micrometers, the grating period is 670.70882 micrometers, the refractive index modulation depth is 0.00015, and the lengths of the first long-period fiber grating and the second long-period fiber grating are 50000 micrometers.
In an embodiment of the invention, the optical fiber includes any one of the following: single mode optical fibers, multimode optical fibers, photonic crystal fibers.
In the embodiment of the invention, the optical fiber is a single-mode optical fiber, the fiber core diameter is 4.15 mu m, the refractive index is 1.4492 mu m, the fiber cladding diameter is 58.35 mu m, and the refractive index is 1.4403 mu m.
In a second aspect of the present application, there is further provided a fiber bragg grating temperature sensing device based on vernier effect, including a fiber bragg grating temperature sensor as described above, the fiber bragg grating temperature sensing device further including: an optical signal emitter, an optical isolator, and a spectrometer; the optical signal transmitter is connected with the input end of the optical isolator, the output end of the optical isolator is connected with the input end of the fiber bragg grating temperature sensor, and the output end of the fiber bragg grating temperature sensor is connected with the spectrometer.
In the embodiment of the invention, the optical signal emitted by the optical signal emitter is a mutation-free continuous spectrum laser light source with the wavelength of 800-1800 nm.
In the embodiment of the invention, the spectrometer is a spectrometer for detecting the light intensity with the wavelength range of 800-1800 nm, and the detection sensitivity is less than 1nm.
In an embodiment of the invention, the optical signal emitter emits an incident optical signal at 1550 nm.
Through above-mentioned technical scheme, possess following beneficial effect: the fiber bragg grating temperature sensor provided by the embodiment of the invention adopts structures with different sensitivities to carry out cascade combination, and has higher sensitivity to temperature by generating vernier effect; fiber grating structural parameters of fiber grating temperature sensor design, such as: the length, the grating period and the refractive index modulation depth of the fiber bragg grating can be precisely controlled, the fiber bragg grating can be flexibly designed, and the sensing sensitivity and resolution can be adjusted; the fiber bragg grating temperature sensor is prepared by selecting optical fibers, and has the advantages of low cost, simplicity in preparation and the like; the fiber bragg grating temperature sensor adopts the fiber bragg grating technology, and the prepared FBG-FP cavity not only maintains the advantages of the traditional FP cavity, but also has the advantages of high physical strength and wide measurement range; compared with the traditional Mach-Zehnder interferometer, the dual-LPFG structure is easier to realize, reduces measurement errors, and has higher resolution.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain, without limitation, the embodiments of the invention. In the drawings:
FIG. 1 is a schematic diagram of a fiber grating temperature sensor based on vernier effect according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a fiber grating temperature sensor based on vernier effect according to an embodiment of the present invention;
FIG. 3 is a graph showing the transmission spectrum of an embodiment of the present invention; and
FIG. 4 is a graph showing the reflection spectrum of the embodiment of the present invention.
Description of the reference numerals
100. A fiber grating temperature sensor; 30. An optical fiber;
10. fiber bragg grating fabry-perot cavities; 20. A dual long period fiber grating structure;
101. a first fiber Bragg grating structure; 102. A second fiber Bragg grating structure;
201. a first long period fiber grating 201; 202. A second long period fiber grating;
1. an optical signal transmitter; 2. An optical isolator;
3 (100), a fiber grating temperature sensor; 4. A spectrometer;
5. and an upper computer.
Detailed Description
The following describes the detailed implementation of the embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The following describes the detailed implementation of the embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "or" appearing throughout the text is to include three side-by-side schemes, for example, "a or B", including a scheme, or B scheme, or a scheme where a and B meet at the same time. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
For a better understanding of the present solution, the present solution is described in terms of the following technical terms of the design.
Fiber bragg grating: the formation mode mainly uses various lasers to make the optical fiber produce periodic change of axial refractive index so as to form a phase grating with permanent space, and its action is that a (transmission or reflection) filter or reflecting mirror is formed in the optical fiber core, and the guided mode with defined frequency/wavelength is reflected, and its filtering wavelength is called Bragg wavelength, and under defined condition the Bragg wavelength is equal to effective refractive index of the position where the grating is positioned multiplied by geometric period of the grating, and the effective refractive index and grating period can be changed with temperature and stress state, so that it is the basis for application of optical fiber grating in stress and temperature sensing.
[ embodiment one ]
Referring to fig. 1, fig. 1 is a schematic structural diagram of a fiber grating temperature sensor 100 based on vernier effect according to an embodiment of the present invention.
The fiber bragg grating temperature sensor 100 includes at least one optical fiber 30, a length of the optical fiber 30 of the fiber bragg grating temperature sensor 30 is taken as an example, a first bragg fiber bragg grating structure 101 and a second bragg fiber bragg grating structure 102 are inscribed on the length of the optical fiber 30, and are arranged such that the first bragg fiber bragg grating structure 101 and the second bragg fiber bragg grating structure 102 are spaced apart by a predetermined distance, whereby the first bragg fiber grating structure 101 and the second bragg fiber bragg grating structure 102 form an FBG-FP cavity 10 (FBG-FP cavity: fiber bragg grating fabry-perot cavity, hereinafter the same) so that an optical signal can be freely transmitted therebetween.
Further, in the direction along the optical path on the same optical fiber 30, the length of optical fiber 30 is further inscribed with a first long-period optical fiber grating 201 and a second long-period optical fiber grating 202, where the first long-period optical fiber grating 201 and the second long-period optical fiber grating 202 are equally spaced by a preset distance, so as to form the dual-long-period optical fiber grating structure 20.
In order to realize the vernier effect, the fiber bragg grating fabry-perot cavity 10 and the dual long period fiber bragg grating structure 20 are combined in different cascading modes to generate the vernier effect by combining two structures with different sensitivities;
it will be appreciated that the vernier effect is due to physical phenomena in the form of scales present in optics, for example, the reflection or transmission spectrum of a broad spectrum light source after having undergone a fabry-perot cavity etalon is a comb spectrum, such as the reflection spectrum of a bragg sampled grating.
The peak interval of the dressing spectrum can be adjusted by adjusting the width of the optical signal or the cavity length of the fiber bragg grating fabry-perot cavity 10 and the dual-long period fiber bragg grating structure 20, so that after the optical signal passes through the fiber bragg grating fabry-perot cavity 10 and the dual-long period fiber bragg grating structure 20, a spectrum with different peak intervals can be obtained, an optical vernier effect can be formed by mutually influencing the spectrums, one of the cavity structures (one of the fiber bragg grating fabry-perot cavity 10 and the dual-long period fiber bragg grating structure 20) is assumed to be influenced by external environment, such as temperature, pressure and strain, the spectrum of the cavity structure is slightly shifted under the condition of keeping the peak interval, and the generated minute displacement can be amplified and read by detecting the initially aligned spectrum and the current spectrum, so that sensing is realized, a larger measurement range can be kept, and the sensitivity of measurement is improved.
Further, the above-mentioned cascade manner may be a cyclic cascade, a cascade amplifier or an interface, and after the cascade, the fiber grating fabry-perot cavity 10 and the dual long period fiber grating structure 20 may change their sensitivities according to the measurement environment and the designed structural parameters, wherein the low-sensitivity structure is used as a cursor fixing portion and the high-sensitivity structure is used as a cursor sliding portion.
Furthermore, the fiber bragg grating fabry-perot cavity 10 is designed to ensure that the structural parameters of the two bragg fiber gratings (i.e., the first bragg fiber grating structure 101 and the second bragg fiber grating structure 102) are consistent and separated by a predetermined first distance (the first distance is obtained by experimental deployment according to the size structure of the optical fiber), and the first bragg fiber grating structure 101 and the second bragg fiber grating structure 102 are arranged by layout to form the FBG-FP cavity.
Meanwhile, when designing the dual long period fiber grating structure 20, it is required to ensure that the parameters of the two long period fiber grating structures (i.e. the first long period fiber grating 201 and the second long period fiber grating 202) are consistent and separated by a preset second distance, and the second distance is also determined according to the size of the optical fiber, specifically according to experiments, and then the two long period fiber grating structures are cascaded to form the dual long period fiber grating structure.
Wherein the above mentioned "structural parameters" refer to the length, width, depth and other dimensional parameters of the grating structure.
It will be appreciated that in the embodiments of the present invention, the specific shape of the optical fiber mentioned above may be not limited, and may be various, and different types of optical fibers may be selected according to the measured environmental conditions and the measured temperature ranges, materials and composition of the optical fibers may be changed, different shapes may be designed, and the optical fibers may be specifically designed according to practical situations.
Further, the above-mentioned optical fiber may include: single mode optical fibers, multimode optical fibers, photonic crystal fibers, and the like.
In one specific embodiment, the structure in the fiber grating temperature sensor 100 may be written in the form of ultraviolet lithography technology, using an ultraviolet light source, to effect transfer of the cavity structure involved to the fiber.
Ultraviolet lithography is a common technique to those skilled in the art, again without undue experimentation.
In a specific embodiment, where the grating length of the first bragg fiber grating structure 101 and the second bragg fiber grating structure 102 is 1000 μm, the grating period is 0.5358 μm, the refractive index modulation depth is 0.00015, and the length of the first bragg fiber grating structure 101 and the second bragg fiber grating structure 102 is 3000 μm, the fiber bragg grating fabry-perot cavity 10 is formed; the first long period fiber grating 10 and the second long period fiber grating 202 have a grating length of 50000 μm, a grating period of 670.70882 μm, a refractive index modulation depth of 0.00015, and a length of 50000 μm, constituting the dual long period fiber grating structure 20.
It should be understood by those skilled in the art that the above data are obtained from analysis, and that simple variations are made on the above data, such as modulating the grating periods of the first and second bragg fiber grating structures 101 and 102 to plus or minus 0.05 μm, while still falling within the scope of the embodiments of the present invention,
in the cascade connection of the fiber grating temperature sensor 100, the fiber grating fabry-perot cavity 10 with high sensitivity may be used as a vernier sliding portion, and the dual long period fiber grating structure 20 with low sensitivity may be used as a vernier fixing portion, so as to generate a vernier effect through cascade connection.
After the fiber bragg grating temperature sensor formed by the method is placed in the air, temperature adjustment is carried out on temperature change around the sensor by adopting a temperature control device. In the experiment, the temperature change is between-20 ℃ and 100 ℃, the temperature change range of-20 ℃ to 100 ℃ is recorded, and the transmission spectrum diagram of the sensor is shown in figure 3 and the reflection spectrum diagram is shown in figure 4 through a spectrometer. It is obvious that the temperature sensitivity and the measurement range of the temperature sensor of the embodiment of the invention are further improved compared with the single FBG-FP cavity structure and the dual LPFG structure.
In summary, the embodiment of the invention has the following beneficial effects through the technical scheme: the fiber bragg grating temperature sensor provided by the embodiment of the invention adopts structures with different sensitivities to carry out cascade combination, and has higher sensitivity to temperature by generating vernier effect; fiber grating structural parameters designed for the fiber grating temperature sensor 100 include: the length, the grating period and the refractive index modulation depth of the fiber bragg grating can be precisely controlled, the fiber bragg grating can be flexibly designed, and the sensing sensitivity and resolution can be adjusted; the fiber bragg grating temperature sensor 100 is prepared by selecting optical fibers, and has the advantages of low cost, simplicity in preparation and the like; the fiber bragg grating temperature sensor 100 adopts the fiber bragg grating technology, and the prepared FBG-FP cavity not only maintains the advantages of the traditional FP cavity, but also has the advantages of high physical strength and wide measurement range; compared with the traditional Mach-Zehnder interferometer, the dual-LPFG structure is easier to realize, reduces measurement errors, and has higher resolution.
[ example two ]
Referring to fig. 2, fig. 2 is a schematic structural diagram of a fiber grating temperature sensing device based on vernier effect according to an embodiment of the present invention; the embodiment provides a fiber grating temperature sensing device based on vernier effect, which comprises an optical signal emitter 1, an optical isolator 2, a fiber grating temperature sensor 3 (the same as the fiber grating temperature sensor 100 is provided with clear and continuous labels, and the fiber grating temperature sensor 3 is used for replacing), a spectrometer 4 and an upper computer 5; wherein the signal emitter 1, the optical isolator 2, the fiber bragg grating temperature sensor 3, the spectrometer 4 and the upper computer 5 are connected in sequence according to the light path.
Further, the optical signal transmitter 1 may output incident light, after the incident light passes through the optical isolator 2, the incident light passing through the optical isolator 2 enters the fiber bragg grating temperature sensor 3, interference occurs when the incident light passes through the fiber bragg grating temperature sensor 3, the incident light after interference by the fiber bragg grating temperature sensor 3 enters the spectrometer 4, the spectrometer 4 is connected to the upper computer 5, and finally, corresponding data is analyzed in the upper computer 5.
The upper computer 5 can be a PC terminal, a mobile phone, a tablet or a microcomputer.
Referring to fig. 2, by adjusting the incident light output by the optical signal emitter 1 multiple times, the wavelength of the incident light output by the optical signal emitter 1 in this example is 1550nm, the wavelength range of detection by the spectrometer 4 is 1545 to 1555nm, and in this detection experiment, the optical fiber in the fiber grating temperature sensor 3 is a conventional single-mode fiber, the fiber core diameter is 4.15 μm, the refractive index is 1.4492 μm, the fiber cladding diameter is 58.35 μm, and the refractive index is 1.4403 μm.
When the external temperature is simulated to change through the temperature controller, the temperature controller acts on the fiber grating temperature sensor 3 in a certain mode to cause corresponding change of interference output signals, and the change parameters of the external temperature can be obtained by analyzing the data of the spectrometer 4, so that temperature sensing is realized. Through regulating and controlling the signal lights of different wavelength ranges of the optical signal transmitter 1 and the structural parameters of the FPG-FP cavity and the double-long period fiber grating in the fiber grating temperature sensor 3, temperature measurement in different environments can be realized, and simultaneously, the sensitivity of the sensor to temperature measurement in different environments can be further improved.
According to the different environments where the measurement temperature is located and the different requirements of the optical wavelength range of the incident light required by the fiber grating design, the optical signal transmitter 1 can be a mutation-free continuous spectrum laser source with the wavelength continuously changing within the range of 800-1800 nm, and the spectrometer 4 can be a spectrometer for detecting the light intensity within the wavelength range of 800-1800 nm, and the detection sensitivity is less than 1nm.
Referring to fig. 1 and 2, the working principle of the sensing device of the embodiment of the invention is as follows: the 1550nm incident light signal emitted by the optical signal emitter 1 enters the optical isolator 2 through the single-mode optical fiber, the optical isolator 2 can greatly reduce the adverse effect of the reflected light generated by the Bragg grating on the spectral output power stability of the light source, the incident light enters the fiber bragg grating temperature sensor 3 after passing through the optical isolator 2, part of the incident light is reflected back after passing through the first Bragg fiber bragg grating structure 101, the other part of the incident light passes through, the light passing through the Bragg fiber bragg grating structure 10 continues to be transmitted forward to the second Bragg fiber bragg grating structure 102, part of the light still passes through, and the light reflected by the second Bragg fiber bragg grating structure 102 can interfere in the fiber bragg grating Fabry-Perot cavity 10 formed by the first Bragg fiber bragg grating structure 101 and the second Bragg fiber bragg grating structure 102;
further, when the transmitted light passing through the second bragg fiber grating structure 102 continues to propagate forward and encounters the first long period fiber grating 201, part of energy is coupled into the cladding layer to continue to propagate forward, when the transmitted light encounters the second long period fiber grating 202, part of energy transmitted in the cladding layer is consumed, the rest of energy is coupled into the fiber core, interference fringes are formed in the transmission spectrum when coupled again, which is equivalent to the formation of a Mach-Zehnder effect (Mach-Zehnder effect: mach-Zehnder effect, referring to the Mach-Zehnder interferometer), an optical signal passing through the fiber grating temperature sensor 3 enters the spectrometer 4, the spectrometer 4 is connected to the upper computer 5, and finally, temperature data is analyzed in the upper computer.
In summary, the embodiment of the invention can derive a fiber grating temperature sensing device based on the fiber grating temperature sensor 3, and the device combines the original devices such as an optical signal emitter, an optical isolator, a spectrometer and the like based on the fiber grating temperature sensor, and the fiber grating temperature sensing device can not limit the size and the outline, only needs to use the elements corresponding to the sensing elements to realize the same or similar functions, and is also within the scope of the invention.
It should also be understood by those skilled in the art that if the fiber bragg grating temperature sensor or the fiber bragg grating temperature sensor provided by the present invention is simply changed, functions added to the method are combined, or replaced on the device thereof, such as replacement on model materials of each component, replacement on use environment, simple replacement on the positional relationship of each component, etc.; or the products formed by the two are integrally arranged; or a removable design; the combined components may constitute a method/apparatus/device with specific functions, and it is within the scope of the present invention to replace the method and apparatus of the present invention with such a method/apparatus/device.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises an element.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. which are within the spirit and principles of the present application are intended to be included within the scope of the claims of the present application.
Claims (8)
1. The fiber bragg grating temperature sensor based on the vernier effect is characterized by comprising an optical fiber, wherein the optical fiber comprises a first cascaded region and a second cascaded region, the first region is provided with two Bragg fiber bragg grating structures as resonant cavities to form FBG-FP cavities, the second region is provided with two long-period fiber bragg grating structures to form a double-long-period fiber bragg grating structure, and the FBG-FP cavities and the double-long-period fiber bragg grating structure are cascaded to generate the vernier effect; the FBG-FP cavity and the double long period fiber grating structure are in cascade connection in at least two modes, so that the FBG-FP cavity and the double long period fiber grating structure generate a low-sensitivity structure and a high-sensitivity structure; wherein the low-sensitivity structure is used as a cursor fixing part, and the high-sensitivity structure is used as a cursor sliding part;
the two fiber Bragg grating structures are a first fiber Bragg grating structure and a second fiber Bragg grating structure, the grating lengths of the first fiber Bragg grating structure and the second fiber Bragg grating structure are 1000 micrometers, the grating period is 0.5358 micrometers, the refractive index modulation depth is 0.00015, and the lengths of the first fiber Bragg grating structure and the second fiber Bragg grating structure are 3000 micrometers;
the two long-period fiber gratings are a first long-period fiber grating and a second long-period fiber grating, the grating lengths of the first long-period fiber grating and the second long-period fiber grating are 50000 micrometers, the grating period is 670.70882 micrometers, the refractive index modulation depth is 0.00015, and the lengths of the first long-period fiber grating and the second long-period fiber grating are 50000 micrometers.
2. The fiber grating temperature sensor based on vernier effect of claim 1, wherein the two bragg fiber grating structures have identical structural parameters and are spaced apart by a predetermined distance to form an FBG-FP cavity.
3. The fiber bragg grating temperature sensor based on vernier effect of claim 1 or 2, wherein the optical fiber comprises any one of the following: single mode optical fibers, multimode optical fibers, or photonic crystal fibers.
4. A vernier effect based fiber grating temperature sensor as defined in claim 3, wherein the fiber is a single mode fiber, the core diameter is 4.15 μm, the refractive index is 1.4492 μm, the cladding diameter is 58.35 μm, and the refractive index is 1.4403 μm.
5. A fiber grating temperature sensing device based on vernier effect, comprising the fiber grating temperature sensor based on vernier effect as set forth in any one of claims 1 to 4, further comprising:
an optical signal emitter, an optical isolator, and a spectrometer;
the optical signal transmitter is connected with the input end of the optical isolator, the output end of the optical isolator is connected with the input end of the fiber bragg grating temperature sensor, and the output end of the fiber bragg grating temperature sensor is connected with the spectrometer.
6. The vernier effect based fiber grating temperature sensing device of claim 5, wherein the optical signal emitted by the optical signal emitter is a mutation-free continuous spectrum laser light source with a wavelength of 800 to 1800 nm.
7. The vernier effect based fiber grating temperature sensing device according to claim 5, wherein the spectrometer is a spectrometer for detecting light intensity in a wavelength range of 800 to 1800nm, and the detection sensitivity is less than 1nm.
8. The vernier effect based fiber grating temperature sensing device of claim 5, wherein the optical signal emitter emits an incident optical signal of 1550 nm.
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