CN112729122B - Femtosecond laser direct writing-based inclined chirped fiber grating sensor testing method - Google Patents
Femtosecond laser direct writing-based inclined chirped fiber grating sensor testing method Download PDFInfo
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- CN112729122B CN112729122B CN202011392586.2A CN202011392586A CN112729122B CN 112729122 B CN112729122 B CN 112729122B CN 202011392586 A CN202011392586 A CN 202011392586A CN 112729122 B CN112729122 B CN 112729122B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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Abstract
The invention provides a femtosecond laser direct writing based inclined chirped fiber grating displacement sensor test method, which is characterized in that a femtosecond laser of a coherent company is used and matched with a femtosecond writing platform, an optical fiber clamp is rotated to enable the optical fiber clamp to have a certain inclination angle, and a certain acceleration is set to realize the writing of the inclined chirped grating. The inclined chirped grating has a cladding mode due to the inclined grid line, a fiber core mode and a cladding mode, the cladding mode leaks due to unstable mode field, the leakage mode is received by arranging a piece of attached D-shaped optical fiber, and displacement sensing is carried out according to the change of the received leakage mode during relative displacement of the two.
Description
Technical Field
The invention belongs to the field of optical fiber devices, and particularly relates to a femtosecond laser direct writing-based inclined chirped fiber grating sensor testing method.
Background
The displacement sensor is mainly applied to the field of airborne displacement sensing, including flight attitude monitoring and structural health detection. In the field of airborne displacement sensing, the airborne displacement sensing device has limited use environment space, higher precision requirement, electromagnetic interference and certain corrosivity, and cannot be well applied to the traditional electrical sensor. The optical fiber sensor has the characteristics of small volume, high sensitivity, electromagnetic interference resistance, corrosion resistance, good electrical insulation property and the like, and can be suitable for the field of airborne displacement sensing. In the aspect of the inclined chirped fiber grating, the research on the inclined chirped grating is increased in recent years, and the special cladding mode property of the inclined chirped fiber grating can be applied to measurement in different fields. In the inclined grating writing, a phase mask method is commonly used, the invention uses the femtosecond laser direct writing method to solve the problems that the writing process is uncontrollable and cannot be monitored in real time in the traditional method, and the inclined grating with controllable characteristic wavelength can be prepared.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a femtosecond laser direct writing inclined chirped fiber grating sensor-based testing method which has the characteristics of small volume, high sensitivity, electromagnetic interference resistance, corrosion resistance, good electrical insulation and the like and can be applied to the field of airborne displacement sensing.
In order to solve the technical problems, the invention adopts the technical scheme that: a femtosecond laser direct writing based inclined chirped fiber grating sensor testing method comprises the following steps:
step a, performing laser writing on the inclined chirped fiber grating;
b, fixing the D-shaped optical fiber on an optical fiber displacement platform, and placing the inclined chirped fiber grating on the upper surface of the D-shaped optical fiber without clamping;
c, connecting a broadband light source, a first spectrometer and the left end of the inclined chirped fiber grating through a circulator;
d, connecting the right end of the inclined chirped fiber grating with a second spectrometer, and connecting the left end of the D-shaped fiber with a third spectrometer;
e, enabling the inclined chirped fiber grating and the D-type optical fiber to generate relative displacement by slowly moving the optical fiber displacement platform;
and f, detecting the light received by the D-type optical fiber through a third spectrometer, and monitoring the received light in the D-type optical fiber to achieve the purpose of displacement sensing.
An obliquely chirped fiber grating comprising a first cladding and a first core; the first fiber core is provided with a grid line, and a certain angle is formed between the grid line and the first fiber core; a cladding mode exists in the first cladding, and a fiber core mode exists in the first fiber core.
Preferably, the writing of the obliquely chirped fiber grating comprises the following steps: a1, placing the inclined chirped fiber grating on a clamping platform of the writing platform; step a2, turning on the femtosecond laser, connecting the femtosecond laser with a computer, and setting the shape and related parameters of the inscription; step a3, writing the inclined chirped fiber grating by adjusting the acceleration and the inclination angle of the platform; and a4, connecting the two ends of the inclined chirped fiber grating with a spectrometer and a light source respectively, and observing parameters.
Preferably, the tilted chirped fiber grating and the D-type fiber are both prepared by a common single mode fiber.
Compared with the prior art, the invention has the beneficial effects that:
1. the sensor of the invention can be suitable for the field of airborne displacement sensing due to the characteristics of small volume, high sensitivity, electromagnetic interference resistance, corrosion resistance, good electrical insulation and the like;
2. the special cladding mode property of the sensor can be applied to measurement in different fields;
3. the sensor of the invention uses the femtosecond laser direct writing method to solve the problems of uncontrollable writing process and uncontrollable real-time monitoring in the traditional method, and can prepare the inclined grating with controllable characteristic wavelength.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
Further objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention, with reference to the accompanying drawings, in which:
FIG. 1 schematically illustrates a schematic diagram of the principle of the femtosecond laser writing of an obliquely chirped grating according to the present invention;
FIG. 2 schematically illustrates a displacement sensor testing method of the present invention;
FIG. 3 is a schematic diagram of the structure of the displacement sensor of the present invention;
fig. 4 schematically shows a test process diagram of the displacement sensor test method of the invention.
In the figure:
10. objective lens 20 and femtosecond laser
30. First cladding 40, first core
50. Second cladding 60, second core
101. Broadband light source 102, first spectrometer
103. Circulator 104 and optical fiber clamping displacement platform
105. D-type optical fiber 106, and tilted chirped fiber grating
107. Third spectrometer 108, second spectrometer
Detailed Description
The objects and functions of the present invention and methods for accomplishing the same will be apparent by reference to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in different forms. The nature of the description is merely to assist those skilled in the relevant art in a comprehensive understanding of the specific details of the invention.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar components, or the same or similar steps.
A femtosecond laser direct writing based inclined chirped fiber grating sensor testing method comprises the following steps:
step a, performing laser writing on the inclined chirped fiber grating;
b, fixing the D-shaped optical fiber 105 on an optical fiber displacement platform, and placing the inclined chirped fiber grating 106 on the upper surface of the D-shaped optical fiber 105 without clamping;
step c, connecting the broadband light source 101, the first spectrometer 102 and the left end of the inclined chirped fiber grating 106 through a circulator 103;
d, connecting the right end of the inclined chirped fiber grating 106 with a second spectrometer 108, and connecting the left end of the D-shaped fiber 105 with a third spectrometer 107;
e, enabling the inclined chirped fiber grating 106 and the D-type optical fiber 105 to generate relative displacement by slowly moving the fiber displacement platform;
and f, detecting the light received by the D-shaped optical fiber 105 through the third spectrometer 107, and monitoring the received light in the D-shaped optical fiber 105 to achieve the purpose of displacement sensing.
An obliquely chirped fiber grating 106, the obliquely chirped fiber grating 106 comprising a first cladding 30 and a first core 40; wherein, a grid line is arranged in the first fiber core 40, and a certain angle is formed between the grid line and the first fiber core 40; a cladding mode exists within the first cladding 30 and a core mode exists within the first core 40.
The writing of the obliquely chirped fiber grating 106 includes the steps of: a1, placing the inclined chirped fiber grating 106 on a clamping platform of the writing platform; step a2, turning on the femtosecond laser, connecting the femtosecond laser with a computer, and setting the shape and related parameters of the inscription; step a3, writing the inclined chirped fiber grating by adjusting the acceleration and the inclination angle of the platform; and a4, connecting the two ends of the inclined chirped fiber grating 106 with a spectrometer and a light source respectively, and observing parameters.
The tilted chirped fiber grating 106 and the D-type fiber 105 are both fabricated from a common single mode fiber.
The invention provides a femtosecond laser direct writing-based inclined chirped fiber grating 106(TCFBG) displacement sensor, which uses a femtosecond laser of a coherent company, is matched with a femtosecond writing platform, has a certain inclination angle by rotating an optical fiber clamp, and sets a certain acceleration to realize the writing of the inclined chirped grating. The inclined chirped grating has a cladding mode besides a fiber core mode due to inclined grid lines, the cladding mode leaks due to unstable mode field, the leakage mode is received by arranging a jointed D-shaped optical fiber 105, and displacement sensing is carried out according to the received leakage mode change during relative displacement of the two.
The invention provides a method for preparing an inclined chirped grating by femtosecond laser direct writing, and an inclined chirped fiber grating displacement sensor based on the femtosecond laser direct writing is prepared on the basis of the method and is tested. Because a certain angle exists between the grid line of the inclined grating and the first fiber core 40, the coupling between the fiber core mold in forward transmission and the cladding mold in backward transmission exist, the cladding mold can leak due to unstable mode field, the leakage mold is received by arranging the attached D-shaped optical fiber 105, and displacement sensing is carried out according to the change of the received leakage mold when the two are relatively displaced.
The tilted chirped fiber grating 106(TCFBG) used in the present invention is fabricated using a standard single mode fiber. Cladding modes are present in the first cladding 30 and core modes are present in the first core 40.
As shown in fig. 1, which illustrates a schematic diagram of the principle of the femtosecond laser writing of the inclined chirped grating according to the present invention, in the operation process, firstly, the femtosecond laser 20 is turned on, the inclined chirped fiber grating 106 is placed on the holder of the writing platform, the femtosecond laser 20 is connected to a computer, and the writing shape and related parameters are set; in order to observe some characteristics of the written fiber grating in the writing process, the two ends of the tilted chirped fiber grating 106 are respectively connected with a spectrometer and a light source for parameter observation. The moving direction of the arrow in the first core 40 indicates the moving track of the laser writing, and the periphery of the arrow indicates the grating line.
Firstly, as shown in fig. 2, a broadband light source 101, an obliquely chirped fiber grating 106 and a spectrometer are connected, a D-type optical fiber 105 is fixed on a fiber clamping displacement platform 104, the obliquely chirped fiber grating 106 is not clamped, a second spectrometer 108 is connected with the right end of the obliquely chirped fiber grating 106, a third spectrometer 107 is connected with the left end of the D-type optical fiber 105, and the fiber clamping displacement platform 104 is moved slowly to generate relative displacement between the obliquely chirped fiber grating 106 and the two optical fibers, as shown in fig. 4, due to the chirping characteristics, reflected lights in different regions are different, so that cladding modes formed are also different, lights received in the D-type optical fiber 105 are also different, and the purpose of displacement sensing can be achieved by monitoring the received lights in the D-type optical fiber 105.
Fig. 4 is a diagram showing the testing process of the displacement sensor testing method according to the present invention, in which the arrows tilted vertically downwards indicate a process of leakage of the cladding mode in the tilted chirped fiber grating 106(TCFBG) to the D-type fiber 105.
The beneficial effects of the invention are: the sensor of the invention can be suitable for the field of airborne displacement sensing due to the characteristics of small volume, high sensitivity, electromagnetic interference resistance, corrosion resistance, good electrical insulation and the like; the special cladding mode property of the sensor can be applied to measurement in different fields; the sensor of the invention uses the femtosecond laser direct writing method to solve the problems of uncontrollable writing process and uncontrollable real-time monitoring in the traditional method, and can prepare the inclined grating with controllable characteristic wavelength.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
Claims (3)
1. A femtosecond laser direct writing based inclined chirped fiber grating sensor test method is characterized by comprising the following steps:
step a, performing laser writing on the inclined chirped fiber grating;
the inclined chirped fiber grating comprises a first cladding and a first fiber core;
the first fiber core is provided with a grid line, and a certain angle is formed between the grid line and the first fiber core;
a cladding mode exists in the first cladding, and a fiber core mode exists in the first fiber core;
b, fixing the D-shaped optical fiber on an optical fiber displacement platform, and placing the inclined chirped fiber grating on the upper surface of the D-shaped optical fiber without clamping;
c, connecting a broadband light source, a first spectrometer and the left end of the inclined chirped fiber grating through a circulator;
d, connecting the right end of the inclined chirped fiber grating with a second spectrometer, and connecting the left end of the D-shaped fiber with a third spectrometer;
e, enabling the inclined chirped fiber grating and the D-type optical fiber to generate relative displacement by slowly moving the optical fiber displacement platform;
and f, detecting the light received by the D-type optical fiber through a third spectrometer, and monitoring the received light in the D-type optical fiber to achieve the purpose of displacement sensing.
2. The method of claim 1, wherein the writing of the obliquely chirped fiber grating comprises the steps of:
a1, placing the inclined chirped fiber grating on a clamping platform of the writing platform;
step a2, turning on the femtosecond laser, connecting the femtosecond laser with a computer, and setting the shape and related parameters of the inscription;
step a3, writing the inclined chirped fiber grating by adjusting the acceleration and the inclination angle of the platform;
and a4, connecting two ends of the inclined chirped fiber grating with a spectrometer and a light source respectively, and observing parameters.
3. The method of claim 1, wherein the tilted chirped fiber grating and the D-type fiber are both prepared from a common single mode fiber.
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| WO2006107278A1 (en) * | 2005-04-05 | 2006-10-12 | Agency For Science, Technology And Research | Fiber bragg grating sensor |
| CN110715901A (en) * | 2019-10-09 | 2020-01-21 | 温州大学 | Resonance excitation method of comb-shaped leakage mode of inclined fiber bragg grating, polarization filter and sensing system |
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| CA2504765C (en) * | 2004-04-14 | 2012-11-13 | Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of Industry, Through The Communications Research Centre Canada | Optical fiber sensor based on retro-reflective fiber bragg gratings |
| KR100651714B1 (en) * | 2004-08-11 | 2006-12-01 | 한국전자통신연구원 | Optical transmitting- receiving method and apparatus using in-line chirped and tilted fiber grating |
| US8554024B2 (en) * | 2006-10-25 | 2013-10-08 | Lxdata Inc. | Tilted grating sensor |
| CN105044030B (en) * | 2015-07-30 | 2017-08-08 | 暨南大学 | Evanscent field coupling coefficient meter and its detection method between optical fiber is fine |
| CN205655926U (en) * | 2016-05-11 | 2016-10-19 | 中国计量大学 | Sensing system based on slope fiber grating |
| CN108106533A (en) * | 2017-12-21 | 2018-06-01 | 北京信息科技大学 | Realize the long chirped fiber grating sensor-based system of distributed location identification |
| CN109375124B (en) * | 2018-11-30 | 2019-12-17 | 华中科技大学 | Magnetic field vector sensor based on large-angle inclined fiber bragg grating |
| CN110567379B (en) * | 2019-09-26 | 2021-03-30 | 合肥工业大学 | Spectrum confocal displacement sensor based on chirped fiber bragg grating |
| CN111856643A (en) * | 2020-07-28 | 2020-10-30 | 中国人民解放军国防科技大学 | Ultra-wideband chirped inclined fiber grating writing device, writing method and laser system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2006107278A1 (en) * | 2005-04-05 | 2006-10-12 | Agency For Science, Technology And Research | Fiber bragg grating sensor |
| CN110715901A (en) * | 2019-10-09 | 2020-01-21 | 温州大学 | Resonance excitation method of comb-shaped leakage mode of inclined fiber bragg grating, polarization filter and sensing system |
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