CN116184559A - Femtosecond laser core selection grating engraving device and method for multi-core fiber Bragg grating - Google Patents
Femtosecond laser core selection grating engraving device and method for multi-core fiber Bragg grating Download PDFInfo
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- CN116184559A CN116184559A CN202210616596.2A CN202210616596A CN116184559A CN 116184559 A CN116184559 A CN 116184559A CN 202210616596 A CN202210616596 A CN 202210616596A CN 116184559 A CN116184559 A CN 116184559A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
- G02B6/02133—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating using beam interference
- G02B6/02138—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating using beam interference based on illuminating a phase mask
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
- G02B6/02147—Point by point fabrication, i.e. grating elements induced one step at a time along the fibre, e.g. by scanning a laser beam, arc discharge scanning
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Abstract
The invention relates to a femtosecond laser core selection grating device and a method of a multi-core fiber Bragg grating (MCFBG), wherein the femtosecond laser sequentially passes through a cylindrical lens and a phase mask plate to realize focusing and interference, the focused femtosecond laser presents interference fringes with light intensity at a focal line, the focused interference fringes expose the fiber core of the multi-core fiber, the focused interference fringes are fixed on a high-precision micro-displacement platform in the fiber adjusting process, the intensity of the femtosecond laser is firstly adjusted to be below a fiber core threshold value, the fluorescence of the fiber core excited by the irradiation of the femtosecond laser is acquired by a microscopic imaging system, the focusing position of the femtosecond laser in the fiber core is accurately judged, the fiber is accurately adjusted to focus the femtosecond laser on the selected fiber core, then the intensity of the femtosecond laser is adjusted to be above the fiber core threshold value, the fiber Bragg grating can be prepared in the fiber core, and the grating structure with set wavelength can be inscribed in different fiber cores of the multi-core fiber by rotating the fiber according to the structural parameters of the multi-core fiber. The manufacturing method and the device have the advantages of convenient operation, visual process, high precision and the like, and can be widely applied to the preparation of MCFBG in the multi-core optical fiber.
Description
Technical Field
The invention belongs to the field of manufacturing of multi-core fiber gratings, and relates to a femtosecond laser core selection grating engraving device and method of a multi-core fiber Bragg grating (MCFBG).
Background
In recent years, space division multiplexing transmission has made tremendous progress due to the limitation of single mode fiber bandwidth. The multi-core optical fiber is used as the basis of the space division multiplexing transmission system, has unique characteristics of compactness, robustness, flexibility and the like, and is widely focused in optical fiber sensing. For these reasons, multi-core optical fiber sensors based on fiber bragg gratings are increasingly being widely used in the fields of three-dimensional shape reconstruction, vector acceleration monitoring, and the like.
In 2018, hou Maoxiang et al used a modified talbot interferometer with a scanning lens to write MCFBG on a seven-core fiber based on uv laser and phase mask methods; patent CN113900176a proposes an immersion type multi-core fiber grating writing device, which eliminates or reduces the influence of the fiber cylindrical effect in the refractive index matching liquid, so as to realize the uniform writing of multiple fiber cores. In both cases, since all the cores are irradiated with the laser at the same time, FBGs are engraved in all the cores at the same period. However, many tasks require that gratings of different periods be inscribed on the core of a multi-core fiber, which requires the use of very narrow laser beams and the ability to precisely position the laser beams within the core. The femtosecond laser micromachining technology has higher machining precision and stable threshold, so that FBG (fiber Bragg Grating) can be inscribed on a single fiber core of the multi-core fiber. In 2022, xunzhou Xiao et al proposed a method of directly writing FBG arrays in seven-core optical fibers by using a point-by-point grating technique of automatic positioning with femtosecond laser, through image recognition and micro-displacement compensation. The preparation method of the fiber grating based on the point-to-point grating can accurately inscribe high-quality grating strings in the multi-core fiber, has higher flexibility, but has extremely high requirements on the stability and the precision of the system, and requires an ultra-high precision displacement platform. Compared with the point-to-point grating, the femtosecond laser grating mode based on the phase mask plate has lower system requirements and easy construction, and is suitable for preparing the multi-core fiber Bragg grating with low cost and high efficiency. However, in the preparation of the multi-core fiber bragg grating based on the method, a wider femtosecond laser beam is used for simultaneously exposing and inscribing all fiber cores of the multi-core fiber, and the uniformity of each fiber core grating is poor due to the uneven intensity distribution of the femtosecond laser beam in the multi-core fiber due to the cylindrical effect of the fiber and the different positions of each fiber core. And the traditional fiber bragg grating inscription device still has great difficulty in realizing precise focusing and control of the femtosecond laser beam and carrying out grating inscription operation on a single fiber core of the multi-core fiber under the condition of not affecting other fiber cores.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a femtosecond laser core selection grating carving device and method for a multi-core fiber Bragg grating, which are characterized in that a phase mask plate is utilized to carry out intensity modulation on femtosecond laser, a fiber core of the multi-core fiber is positioned by combining a fiber microscopic imaging system and a photo-induced fluorescence phenomenon of the fiber core after being irradiated by the femtosecond laser, the modulated femtosecond laser is focused on the positioned fiber core, a grating structure is carved, the rotating optical fiber sequentially carves other fiber cores, the fiber Bragg grating period is changed by means of changing the phase mask plates of different periods or stretching the optical fiber to two sides of a displacement platform, and the like, so that MCFBGs with different wavelengths are manufactured, and the problem of the femtosecond laser core selection grating carving in the current MCFBG manufacturing method based on the phase mask method is solved.
Technical proposal
The invention discloses a femtosecond laser core selection grating carving device and a method of a multi-core fiber Bragg grating, which are different from the traditional multi-core fiber grating carving device. The method specifically comprises the following steps:
the femtosecond laser core selection grating device consists of a femtosecond laser output module, a beam shaping module, an optical fiber micro-displacement module and a microscopic imaging module;
the femtosecond laser output module is used for generating power-adjustable femtosecond laser;
the beam shaping module is used for shaping and modulating the femtosecond laser beam to generate a femtosecond laser linear light spot with interference fringes;
the optical fiber micro-displacement module is used for fixing an optical fiber and adjusting the posture and the position of the optical fiber;
the multi-core optical fiber microscopic imaging system is composed of an illumination light source, a microscope objective, a convex lens, an optical filter and a CCD which are sequentially arranged along a light path, wherein the fluorescence intensity of a fiber core under a side microscopic image of the multi-core optical fiber under a bright field and a dark field is respectively observed, the distribution position of the fiber core in the multi-core optical fiber and the focusing position of femto-second laser in the multi-core optical fiber are monitored, the accurate positioning of the position of the multi-core optical fiber is realized, and the photoetching precision of the multi-core grating is ensured.
The beam shaping module consists of an aperture diaphragm, a cylindrical lens and a phase mask plate, wherein the femtosecond laser beam is limited by the aperture diaphragm and then focused by the cylindrical lens, the cross section of the beam is elliptical, the short axis of the elliptical beam is compressed at the focal line of the cylindrical lens to approximate a linear light spot, then the elliptical beam is modulated by the phase mask plate, the long axis of the elliptical beam is provided with interference fringe distribution with phase mask plate information, the shaped femtosecond laser beam is sequentially irradiated to the fiber cores of the multi-core optical fibers, and the fiber gratings with the periods consistent with the interference fringe intervals are respectively written.
The cylindrical lens is a short-focus cylindrical lens and is used for compressing the femtosecond laser beam to the diameter of the fiber core at the focal line of the cylindrical lens, limiting the refractive index modulation range to the inside of the fiber core of the multi-core optical fiber, and ensuring that the grid etching accuracy is improved and the grid etching process is not influenced by other fiber cores.
The interference fringe period is 1/2 of the period of the phase mask plate and is generated by + -1-order diffraction light interference of the phase mask plate.
The optical fiber micro-displacement module consists of two pairs of rotating optical fiber clamps with adjustable angles and a high-precision three-dimensional micro-displacement platform, wherein the rotating optical fiber clamps are respectively fixed on the two high-precision three-dimensional displacement platforms, so that the optical fiber can rotate along the axial direction of the optical fiber and move up and down, left and right and back and forth relative to the femtosecond laser linear light spot with high precision so as to adjust the relative position of the fiber core to be carved and the femtosecond laser linear light spot.
The fiber core fluorescence is nonlinear light-induced fluorescence generated by interaction of the femtosecond laser and the doped fiber core, and the femtosecond laser does not have fluorescence effect when focused on the undoped cladding, so that the fiber core fluorescence is suitable for various fiber core doped multi-core fibers. .
The fluorescence intensity of the fiber core is positively correlated with the power density of the femtosecond laser, and the fluorescence intensity is highest when the femtosecond laser beam is completely focused in the fiber core.
The optical filter is an optical filter corresponding to the femtosecond laser wavelength, and cut-off filtering is carried out on the femtosecond laser scattered light on the optical fiber so as to improve the imaging quality of the fiber core fluorescent pattern.
A method for manufacturing a multi-core fiber Bragg grating in a multi-core fiber by using the device is characterized in that a beam shaping module is used for modulating the intensity of femtosecond laser, a fiber core of the multi-core fiber is positioned by combining a fiber microscopic imaging system and a photo-induced fluorescence phenomenon of the fiber core after being irradiated by the femtosecond laser, the modulated femtosecond laser is focused on the positioned fiber core, a grating structure is engraved, the fiber is rotated to sequentially etch other fiber cores, and the fiber Bragg grating period is changed to manufacture the MCFBG with different wavelengths.
A method for manufacturing a multi-core fiber Bragg grating in a multi-core fiber by using the device comprises the following steps:
step 1: adjusting the femtosecond laser power to be below a fiber core refractive index modulation threshold value, and outputting a femtosecond laser linear spot;
step 2: turning on an illumination light source, adjusting a rotary optical fiber clamp, and placing a fiber core to be etched on a grating etching optical path so that the axis of the fiber core to be etched is parallel to the femtosecond laser linear spot;
step 3: turning off the illumination light source, irradiating the fiber core by the femtosecond laser linear spot to excite fluorescence, and adjusting the fiber core position back and forth and up and down to make the fluorescence strongest, wherein the femtosecond laser beam is completely focused on the selected fiber core at the moment;
step 4: adjusting the energy of the femtosecond laser beam to ensure that the power exceeds the refractive index change threshold of the fiber core, and inscribing a grating structure;
step 5: and (3) adjusting a rotary optical fiber clamp according to the distribution of fiber cores, rotating the optical fiber by taking the axis of the optical fiber as the axis, sequentially placing the rest fiber cores to be carved on a grating optical path, changing the grating period, repeating the steps 1-4, and manufacturing the MCFBG in the multi-core optical fiber.
The mode of changing the grating period comprises changing phase mask plates of different periods or adjusting two high-precision displacement platforms to stretch optical fibers and the like.
Advantageous effects
The invention provides a femtosecond laser core selection grating device and a method of a multi-core fiber Bragg grating, wherein a set of microscopic imaging module and a high-precision fiber micro-displacement module for positioning and identifying a multi-core fiber core are added on the basis of grating by a traditional femtosecond laser phase mask method, the position of the multi-core fiber is accurately regulated, the intensity distribution of femtosecond laser pulses in the multi-core fiber core is intuitively displayed by utilizing a nonlinear photoluminescence principle, and the femtosecond laser can be accurately focused in the core of the multi-core fiber by combining the fiber microscopic imaging system and the micro-displacement module, so that a grating structure is inscribed in the core; by changing the phase mask plate, stretching the optical fiber and the like, the Bragg gratings with different periods can be inscribed in the fiber cores of the multi-core optical fiber, and the multi-core optical fiber Bragg grating with the multi-period grating can be manufactured. The manufacturing method and the device have the advantages of high manufacturing efficiency, easiness in construction, convenience in operation and the like, are suitable for manufacturing multi-core fiber gratings and grating strings of various structures, and can be widely applied to bending, acceleration, multi-parameter and other types of sensing.
Drawings
FIG. 1 is a block diagram of a writing apparatus for a multi-core fiber Bragg grating.
Fig. 2 is a schematic structural diagram of a femtosecond laser manufacturing experiment device of the multi-core fiber bragg grating.
Fig. 3 is a schematic diagram of a fiber microscopic imaging module and a fiber micro-displacement platform.
Fig. 4 is a schematic diagram of a fabricated dual-core fiber grating structure.
FIG. 5 is a schematic diagram of the relationship between the focusing position of the femtosecond laser and the core position of the multi-core fiber during the writing of the grating.
Fig. 6 is a schematic fluorescence diagram of the core of the multicore fiber under the dark field irradiated by the femtosecond laser.
FIG. 7 is a reflection spectrum of the inner and outer cores of a inscribed dual-core fiber grating of the present invention.
FIG. 8 shows the number of each core and the grating order of the seven-core optical fiber.
FIG. 9 is a reflection spectrum of each core of a seven-core fiber grating according to the present invention.
Wherein: 1-femtosecond laser output module, 11-femtosecond laser beam, 12-microscopic imaging light path; the device comprises a 2-beam shaping module, a 21-aperture diaphragm, a 22-cylindrical lens and a 23-phase mask plate; the device comprises a 3-microscopic imaging module, a 31-microscopic objective lens, a 32-convex lens, a 33-filter and a 34-CCD; 4-optical fiber micro-displacement module, 41-micro-displacement platform, 42-rotating optical fiber clamp, 43-illumination light source; 5-multicore optical fiber; 6-double-core optical fiber, 61-double-core optical fiber cladding, 62-double-core optical fiber inner core, 63-double-core optical fiber outer core.
Detailed Description
The invention will now be further described with reference to the examples, figures:
examples of the invention: the femtosecond laser output from the titanium-doped sapphire femtosecond laser system is shaped by an aperture diaphragm, focused by a cylindrical lens, diffracted and split by a phase mask plate, and two coherent + -1-order diffracted lights interfere in a near field behind the mask plate to form a femtosecond laser linear spot with sine distribution of light intensity, and focused on a multi-core optical fiber by the cylindrical lens. In the open field, the distribution position of the cores of the multi-core optical fibers is observed through an optical fiber microscopic imaging system, the three-dimensional micro-displacement platform and the rotary optical fiber clamp are combined, the optical fiber posture is adjusted, the axes of the cores are parallel to the focal line of the cylindrical lens, and the cores to be engraved are rotationally moved to the vicinity of the focal line of the cylindrical lens. In a dark field, a fiber core irradiated by the femtosecond laser linear spot excites blue fluorescence due to a nonlinear photoluminescence effect, the luminous condition of the fiber core is observed, the position of the fiber core is finely adjusted, the blue fluorescence intensity is highest, at the moment, the femtosecond laser linear spot is accurately focused in a selected fiber core, the femtosecond laser energy is regulated to be above a refractive index change threshold, and finally, core selection grating is completed in the multi-core optical fiber. According to the distribution of fiber cores, the fiber cores are sequentially adjusted to the femto-second laser focusing position, the grating period is changed, and the preparation of the multi-core fiber grating is completed.
Specific embodiment As shown in FIG. 2, a femtosecond laser with a center wavelength of 800nm, a pulse width of 35fs, a repetition frequency of 1KHz, and a beam diameter of 8mm was generated by the femtosecond laser output module 1.
The femtosecond laser beam 11 is focused by a cylindrical lens 22 with a focal length of 20mm, the width of the femtosecond laser beam is compressed to about 2.5 μm at the focal line, and then the two beams of coherent + -1-order diffraction light are diffracted and split by a phase mask plate 23, so that two beams of coherent + -1-order diffraction light interfere, a femtosecond laser linear light spot with sine distribution light intensity is formed in the near field behind the phase mask plate 23, and the light is focused on a multi-core optical fiber 5 under the action of the cylindrical lens 22, wherein the optical fiber can be a dual-core optical fiber, a three-core optical fiber, a four-core optical fiber, a seven-core optical fiber and the like, and the dual-core optical fiber and the seven-core optical fiber are adopted in the example so as to illustrate the principle and the flow of core selection grating.
As shown in fig. 3, the fiber image is expanded and amplified by the microscope eye piece 31 under the irradiation of the illumination light source 43, focused and collimated by the convex lens 32, received by the infrared filter 33 and then received by the CCD34, and the distribution position of the fiber cores in the multi-core fiber is observed.
The optical fiber holder 42 is rotated until two cores with consistent boundary width and definition can be observed, and the three-dimensional micro-displacement stage 41 with high precision is adjusted, so that the selected core is adjusted to be near the same level as the focal line of the cylindrical lens as shown in fig. 5 (the state of adjusting from a to b in fig. 5).
Turning off the illumination light source 43, turning on the femtosecond laser, adjusting the light power to be lower than the refractive index change threshold of the fiber core, observing the focusing position of the femtosecond laser in a dark field, emitting blue fluorescence by the germanium-doped fiber core under the irradiation of the femtosecond laser due to the nonlinear photoluminescence effect, increasing the fluorescence intensity along with the increase of the power density of the femtosecond laser, adjusting the micro-displacement platform, moving the multi-core fiber back and forth and up and down, observing the blue fluorescence (b in fig. 6) of the outer fiber core from a microscopic system, so that only one blue fluorescence has the highest intensity, and completely focusing the femtosecond laser on the selected fiber core at the moment; the multi-core optical fiber moves back and forth and up and down under the dark field to make the fluorescence strongest, so that errors caused by limited position regulation and control precision of the fiber cores under the bright field can be made up.
The femtosecond laser power is regulated to be above the refractive index change threshold of the fiber core, the periodic refractive index modulation is formed on the selected fiber core, and a grating structure is formed, because the width of a linear light spot of the femtosecond laser focused on the fiber core is about 2.5 mu m, the width of a refractive index modulation area in the fiber core is about 2.5 mu m, in order to ensure the quality of the grating, a micro-displacement platform can be regulated, and a multi-core optical fiber is moved up and down by 5 mu m to enable the refractive index modulation range to cover the fiber core, so that the core selection engraving of one fiber core is completed.
And (3) repeating the core checking step, focusing the femtosecond laser on other fiber cores, and when FBGs are inscribed on different fiber cores, inscribing grating structures of different periods on the fiber cores by means of replacing phase mask plates of different periods or prestretching the multi-core fiber to different degrees and the like, so as to finally manufacture the MCFBGs in the multi-core fiber. FIG. 7 shows the reflection spectrum of the dual-core fiber grating engraved in the present invention, where the reflection spectrum of the inner and outer fiber gratings has no wavelength information of the gratings in the remaining fiber cores, which indicates that the wavelength information of the gratings in the remaining fiber cores is not affected during the engraving process of the selected core, and the control accuracy of the focusing position of the femtosecond laser beam is high.
The seven cores of the seven-core optical fiber are numbered as shown in fig. 8 and the grating is performed in the order of 1-2-3-4-5-6-0.
First, the core 1 is positioned. And (3) moving the axis of the multi-core optical fiber to the grating optical path, namely keeping the same height with the optical path. Turning on the illumination source, rotating the multi-core optical fiber under bright field microscope, and rotating the fiber core 1 to the vicinity of the grating light path.
And (3) turning off the illumination light source, turning on the femtosecond laser, finely adjusting the micro-displacement platform to ensure that blue fluorescence on the fiber core 1 is strongest and no fluorescence effect exists on other fiber cores, adjusting the laser power, adjusting the micro-displacement platform, and moving the multi-core optical fiber up and down by 5 mu m to ensure that the fiber core 1 is completely engraved with a grating structure.
The phase mask plate is replaced or the optical fiber is stretched, the femtosecond laser power is adjusted to be lower than the refractive index change threshold value of the fiber core, the femtosecond laser power rotates 60 degrees around the axis of the optical fiber according to the distribution of the fiber core in the multi-core optical fiber, at the moment, the femtosecond laser spot is just focused near the fiber core 2, the micro-displacement platform is finely adjusted, the blue fluorescence on the fiber core 2 is strongest, the laser power is adjusted, and gratings with different periods are engraved in the fiber core 2. The above operation is repeated until the cores 1 to 6 are engraved with the grating structure.
Finally, the multi-core optical fiber is horizontally moved along the optical path direction, so that the focusing position of the femtosecond laser beam is moved from the fiber core 6 to the fiber core 0, the blue fluorescence at the fiber core 6 is observed to be gradually weakened under the dark field of a microscopic system, the blue fluorescence at the fiber core 0 is gradually strengthened until the blue fluorescence is only observed on the fiber core 0 and reaches the strongest, the grating carving operation is carried out, and the manufacture of the seven-core optical fiber Bragg grating is completed. FIG. 9 shows the reflection spectrum of the seven-core fiber grating of the present invention, the reflection intensity of each fiber core grating is similar, the uniformity is good, and the difference of the reflection intensity in each fiber core is lower than 4%.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but the equivalent structural changes made by the description of the invention and the accompanying drawings or other related technical fields are included in the scope of the invention.
Claims (11)
1. The utility model provides a femtosecond laser selection core of multicore optic fibre Bragg grating carves bars device which characterized in that:
the femtosecond laser core selection grating device comprises a femtosecond laser output module, a beam shaping module, an optical fiber micro-displacement module and a microscopic imaging module;
the femtosecond laser output module is used for generating power-adjustable femtosecond laser;
the beam shaping module is used for shaping and modulating the femtosecond laser beam to generate a femtosecond laser linear light spot with interference fringes;
the optical fiber micro-displacement module is used for fixing an optical fiber and adjusting the posture and the position of the optical fiber;
the multi-core optical fiber microscopic imaging system is composed of an illumination light source, a microscope objective, a convex lens, an optical filter and a CCD which are sequentially arranged along a light path, wherein the fluorescence intensity of a fiber core under a side microscopic image of the multi-core optical fiber under a bright field and a dark field is respectively observed, the distribution position of the fiber core in the multi-core optical fiber and the focusing position of femto-second laser in the multi-core optical fiber are monitored, the accurate control of the position of the multi-core optical fiber is realized, and the photoetching precision of the multi-core grating is ensured.
2. The femtosecond laser core selection grating device of the multi-core fiber bragg grating according to claim 1, wherein: the beam shaping module consists of an aperture diaphragm, a cylindrical lens and a phase mask plate, wherein the femtosecond laser beam is limited by the aperture diaphragm and then focused by the cylindrical lens, the cross section of the beam is elliptical, the short axis of the elliptical beam is compressed at the focal line of the cylindrical lens to approximate a linear light spot, then the elliptical beam is modulated by the phase mask plate, the long axis of the elliptical beam is provided with interference fringe distribution with phase mask plate information, the shaped femtosecond laser beam is sequentially irradiated to the fiber cores of the multi-core optical fibers, and the fiber gratings with the periods consistent with the interference fringe intervals are respectively written.
3. The femtosecond laser core selection grating device of the multi-core fiber bragg grating according to claim 2, wherein: the cylindrical lens is a short-focus cylindrical lens and is used for compressing the femtosecond laser beam to the diameter of the fiber core at the focal line position of the cylindrical lens, so that the refractive index modulation range is limited inside the fiber core of the multi-core optical fiber, and the grating etching precision is improved while the influence on other fiber cores in the grating etching process is avoided.
4. The femtosecond laser core selection grating device of the multi-core fiber bragg grating according to claim 2, wherein: the interference fringe period is 1/2 of the period of the phase mask plate and is generated by + -1-order diffraction light interference of the phase mask plate.
5. The femtosecond laser core selection grating device of the multi-core fiber bragg grating according to claim 1, wherein: the optical fiber micro-displacement module consists of a pair of angle-adjustable rotary optical fiber clamps and a high-precision three-dimensional micro-displacement platform, wherein the rotary optical fiber clamps are respectively fixed on the two high-precision three-dimensional displacement platforms, so that the optical fiber can rotate along the axial direction of the optical fiber and move up and down, left and right and back and forth relative to the femtosecond laser linear light spot at high precision so as to adjust the relative position of the fiber core to be carved and the femtosecond laser linear light spot.
6. The femtosecond laser core selection grating device of the multi-core fiber bragg grating according to claim 1, wherein: the fiber core fluorescence is nonlinear light-induced fluorescence generated by interaction of the femtosecond laser and the doped fiber core, and the femtosecond laser does not have fluorescence effect when focused on the undoped cladding, so that the fiber core fluorescence is suitable for various fiber core doped multi-core fibers.
7. The femtosecond laser core selection grating device of the multi-core fiber bragg grating according to claim 6, wherein: the fluorescence intensity of the fiber core is positively correlated with the power density of the femtosecond laser, and the fluorescence intensity is highest when the femtosecond laser beam is completely focused in the fiber core.
8. The femtosecond laser core selection grating device of the multi-core fiber bragg grating according to claim 1, wherein: the optical filter is an optical filter corresponding to the femtosecond laser wavelength, and cut-off filtering is carried out on the femtosecond laser scattered light on the optical fiber so as to improve the imaging quality of the fiber core fluorescent pattern.
9. The femtosecond laser core selection grating method of the multi-core fiber Bragg grating according to claims 1-8 is characterized in that a beam shaping module is utilized to carry out intensity modulation on femtosecond laser, a fiber core of the multi-core fiber is positioned by combining a fiber microscopic imaging system and a photo-induced fluorescence phenomenon of the fiber core after being irradiated by the femtosecond laser, the modulated femtosecond laser is focused on the positioned fiber core, a grating structure is engraved, the fiber is rotated to sequentially etch other fiber cores, and then the fiber Bragg grating period is changed, so that MCFBGs with different wavelengths are manufactured.
10. The femtosecond laser core selection grating method of the multi-core fiber bragg grating according to claim 9, which comprises the following steps:
step 1: adjusting the femtosecond laser power to be below a fiber core refractive index modulation threshold value, and outputting a femtosecond laser linear light spot;
step 2: turning on an illumination light source, adjusting a rotary optical fiber clamp, and placing a fiber core to be etched on a grating etching optical path so that the axis of the fiber core to be etched is parallel to the femtosecond laser linear spot;
step 3: turning off the illumination light source, exciting fluorescence by the fiber core under the irradiation of the femtosecond laser linear spot, and adjusting the position of the fiber core back and forth to make the fluorescence strongest, wherein the femtosecond laser beam is completely focused on the selected fiber core at the moment;
step 4: adjusting the energy of the femtosecond laser beam to ensure that the power exceeds the refractive index change threshold of the fiber core, and inscribing a grating structure;
step 5: and (3) adjusting a rotary optical fiber clamp according to the distribution of fiber cores, rotating the optical fiber by taking the axis of the optical fiber as the axis, sequentially placing the rest fiber cores to be carved on a grating optical path, changing the grating period, repeating the steps 1-4, and manufacturing the MCFBG in the multi-core optical fiber.
11. The method for femtosecond laser core selection grating of a multicore fiber bragg grating according to claim 9, wherein the mode of changing the grating period comprises changing phase mask plates of different periods or adjusting two high-precision displacement platforms to stretch the optical fiber, etc.
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| CN117572559A (en) * | 2024-01-05 | 2024-02-20 | 中国航空工业集团公司北京长城计量测试技术研究所 | Preparation device and preparation method of short fiber grating |
| CN118090145A (en) * | 2024-04-16 | 2024-05-28 | 南方海洋科学与工程广东省实验室(珠海) | Optical fiber core identification method for coupling encapsulation |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117572559A (en) * | 2024-01-05 | 2024-02-20 | 中国航空工业集团公司北京长城计量测试技术研究所 | Preparation device and preparation method of short fiber grating |
| CN117572559B (en) * | 2024-01-05 | 2024-05-17 | 中国航空工业集团公司北京长城计量测试技术研究所 | Preparation device and preparation method of short fiber grating |
| CN118090145A (en) * | 2024-04-16 | 2024-05-28 | 南方海洋科学与工程广东省实验室(珠海) | Optical fiber core identification method for coupling encapsulation |
| CN118090145B (en) * | 2024-04-16 | 2024-08-20 | 南方海洋科学与工程广东省实验室(珠海) | Optical fiber core identification method for coupling encapsulation |
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