A roll-to-roll fiber grating and array continuous writing system

Abstract

The present invention discloses a roll-to-roll fiber grating and array continuous writing system, comprising a writing laser light source, a feeding roller, a feeding roller and a writing jig; the writing jig is arranged between the feeding roller and the feeding roller; the writing jig has a fiber channel with at least one end open, the optical fiber passes through the fiber channel, the optical fiber channel is connected to a refractive index matching liquid that maintains hydraulic pressure, so that the refractive index matching liquid fills the gap between the fiber channel and the optical fiber; the writing jig has a first optical flat surface; when laser writing is performed, the refractive index matching liquid forms a stable liquid flow in the optical fiber channel of the writing jig, so that the optical fiber is in a stable position; the laser emitted by the writing laser light source passes through the first optical flat surface of the writing jig and irradiates the optical fiber for writing. The present invention realizes automatic roll-to-roll continuous writing of fiber grating arrays without the need to manually add refractive index matching liquid or replace the writing jig.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber gratings, and more specifically, relates to a roll-to-roll optical fiber grating and array continuous writing system. Background Art

[0002] As a very important optical passive device, the main function of fiber Bragg grating is to reflect light of a specific wavelength. After decades of research, it has been widely used in the fields of communication and sensing. The factor closely related to sensing is its grating period, which is manifested as a periodic refractive index modulation distribution on the fiber core. Its effective specific wavelength is positively correlated with it. Affected by material properties, changes in external related physical quantities cause changes in the grating period, which leads to changes in specific wavelengths, and then realizes the measurement of physical quantity changes. Fiber Bragg grating array is a sensor system composed of multiple fiber Bragg gratings. Each fiber Bragg grating is a sensitive element that can measure physical quantities such as temperature, stress, and refractive index. The reflection wavelengths of multiple fiber Bragg gratings will be different to achieve the analysis of different signals.

[0003] The mature femtosecond fiber grating processing solutions at this stage are the objective lens direct writing method and the phase mask method. Objective lens direct writing method: using an oil lens for focusing, compressing the light spot to the micron level, and processing point by point to achieve the periodic distribution of the refractive index modulation on the fiber core, such as the femtosecond laser direct writing fiber grating technology provided by Chinese patent document CN111175885A; Phase mask method: the period of the phase mask determines the period of the laser interference fringe.

[0004] For fiber grating array processing: the phase mask method has poor flexibility because one phase mask can only process a fiber grating of a specific wavelength, and it is difficult to apply to the serial array processing of different fiber gratings; and the objective lens direct writing method has extremely high requirements on the laser focusing position during the processing because the fiber core size is also in the micron level, and it is difficult to achieve continuous roll-to-roll automated processing. Summary of the invention

[0005] In view of the above-mentioned defects or improvement needs in the prior art, the present invention provides a roll-to-roll fiber grating and array continuous writing system, the purpose of which is to continuously and automatically supply refractive index matching liquid during the continuous writing process of the fiber grating through a writing fixture having an optical fiber channel and an optically flat surface, thereby solving the technical problem that it is difficult to automatically and continuously realize roll-to-roll processing when laser writing fiber grating arrays.

[0006] To achieve the above-mentioned object, according to one aspect of the present invention, a roll-to-roll fiber grating and array continuous writing system is provided, comprising a writing laser light source, a loading roller, a unloading roller and a writing jig;

[0007] The feeding roller is used to release the optical fiber to be inscribed; the lower feeding roller is used to reel in the optical fiber on which the grating has been inscribed; the inscription jig is arranged between the feeding roller and the lower feeding roller;

[0008] The writing jig has an optical fiber channel with at least one end open, the optical fiber passes through the optical fiber channel, and the optical fiber channel is connected to a refractive index matching liquid that maintains hydraulic pressure, so that the refractive index matching liquid fills the gap between the optical fiber channel and the optical fiber; the writing jig has a first optical flat surface;

[0009] During laser writing, the refractive index matching liquid forms a stable liquid flow in the optical fiber channel of the writing fixture, so that the optical fiber is in a stable position; the laser emitted by the writing laser light source passes through the first optical flat surface of the writing fixture and irradiates the optical fiber for writing.

[0010] Preferably, the roll-to-roll fiber grating and array continuous writing system has the writing jig with a refractive index matching liquid injection pipe, which is laterally connected to the optical fiber channel. The cross-section of the optical fiber channel at the connection point has a recessed contour relative to the refractive index matching liquid injection pipe, which is used to help the optical fiber maintain a stable position in the flow of the refractive index matching liquid.

[0011] Preferably, in the roll-to-roll fiber grating and array continuous writing system, the fiber channel has an axially extending groove, and the cross-sectional profile of the groove at the access point is the depression of the cross-sectional area of ​​the fiber channel at the access point and the relative profile of the refractive index matching liquid injection pipeline; preferably, the writing jig includes an upper mold and a lower mold, and the upper mold and the lower mold are pressed together to form the fiber channel; the writing jig is preferably quartz glass.

[0012] Preferably, in the roll-to-roll fiber grating and array continuous writing system, the refractive index matching liquid injection pipeline is connected to the injection pump, and a bubble separator is provided between the refractive index matching liquid injection pipeline and the injection pump; both ends of the fiber optic channel are open, the optical fiber passes through the fiber optic channel through the open ends, and the refractive index matching liquid flows out through the open end of the fiber optic channel; preferably, the refractive index matching liquid that flows out is recovered; preferably, the loading roller and the unloading roller apply a preset tension to the optical fiber to help the optical fiber to be in a stable position.

[0013] Preferably, in the roll-to-roll fiber grating and array continuous writing system, the writing fixture has a second optical flat surface parallel to the direction in which the refractive index matching liquid is connected to the optical fiber channel, and the projection of the optical fiber for writing on the plane where the second optical flat surface is located is within the second optical flat surface; in a preferred embodiment, the second optical flat surface is orthogonal to the first optical flat surface.

[0014] Preferably, the roll-to-roll fiber grating and array continuous writing system further includes a forward imaging component for imaging the optical fiber at the writing position, and its main optical axis is perpendicular to the second optical flat surface.

[0015] Preferably, in the roll-to-roll fiber grating and array continuous writing system, the writing fixture has a third optical flat surface parallel to the second optical flat surface, the fiber channel is located between the second and third optical flat surfaces, and the projection of the fiber writing location on the plane where the third optical flat surface is located is within the third optical flat surface; the forward imaging component uses transmitted light to image the fiber writing location, and the transmitted light passes through the second and third optical flat surfaces.

[0016] Preferably, the forward imaging component of the roll-to-roll fiber grating and array continuous writing system includes an illumination light source and an imaging objective lens. The illumination light source and the imaging objective lens are located on both sides of the writing fixture at the position where the optical fiber is written. The main optical axis of the imaging objective lens is perpendicular to the second and third optical flat surfaces of the writing fixture.

[0017] Preferably, the roll-to-roll fiber grating and array continuous writing system further includes a vertical imaging component for imaging the optical fiber at the writing position, and its main optical axis is perpendicular to the first optical flat surface.

[0018] Preferably, in the roll-to-roll fiber grating and array continuous writing system, the writing fixture has a fourth optical flat surface parallel to the first optical flat surface, and the fiber channel is located between the first and fourth optical flat surfaces; the forward imaging component uses transmitted light to image the optical fiber at the writing location, and the transmitted light passes through the first and fourth optical flat surfaces.

[0019] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0020] The roll-to-roll fiber grating and array continuous writing system provided by the present invention adopts a writing fixture with an optically flat surface, loads the optical fiber to be written through the optical fiber channel, and integrates a refractive index matching liquid injection pipeline, continuously injects refractive index matching liquid into the optical fiber channel and maintains hydraulic pressure, thereby ensuring that the refractive index matching liquid is filled in the entire process of roll-to-roll writing of the fiber grating array, and there is no need to manually add refractive index matching liquid or replace the writing fixture, thereby realizing automated roll-to-roll continuous writing of the fiber grating array. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of a roll-to-roll fiber Bragg grating and array continuous writing system provided by an embodiment of the present invention;

[0022] Figure 2It is a schematic diagram of the structure of the writing jig provided in an embodiment of the present invention;

[0023] Figure 3 It is a schematic diagram of the upper mold structure of the writing jig provided by an embodiment of the present invention;

[0024] Figure 4 It is a schematic diagram of the lower mold structure of the writing jig provided in an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the upper and lower molds of the writing jig provided by the embodiment of the present invention being pressed together;

[0026] Figure 6 is a schematic diagram of an optically flat surface of a writing jig provided in an embodiment of the present invention;

[0027] Figure 7 It is a schematic diagram of assembling a writing jig and a forward imaging component provided by an embodiment of the present invention;

[0028] Figure 8 is a photo of an optical fiber and a writing jig taken by a vertical imaging assembly provided by an embodiment of the present invention;

[0029] Fig. 9 is a photo of an optical fiber and a writing jig taken by a forward imaging assembly provided by an embodiment of the present invention;

[0030] Fig.10 is a photo of a fiber Bragg grating in process taken by a forward imaging assembly provided by an embodiment of the present invention;

[0031] Fig.11 is a fiber grating spectrum diagram automatically processed by an embodiment of the present invention, wherein Fig.11 A is the fiber Bragg grating reflection spectrum, the horizontal axis is the center wavelength (in nm), and the vertical axis is the spectrum power (in dBm). The actual test results show that the center wavelength is 1532.345nm, the bandwidth is 0.258nm, the peak power is -32.34dBm, and the side mode suppression ratio is 30.346dB. Fig.11 B is the fiber Bragg grating transmission spectrum, the horizontal axis is the central wavelength (in nm), and the vertical axis is the relative power difference of the spectrum (in dB). The actual test results show that the power loss is -6.6 dB and the effective reflectivity is 78.122%.

[0032] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein: 1-titanium sapphire femtosecond laser; 2-electric zero-order achromatic half-wave plate device; 3-thin film polarizer; 4-beam splitter; 5-thermopile detector; 6-optical power meter; 7-low GDD reflector; 8-high-speed electronic shutter; 9-dichroic mirror; 10-tube lens; 11-color CCD; 12-adjustable aperture; 13-achromatic long working distance objective lens; 14-writing jig, 141-upper mold, 1411-upper mold groove, 142 lower mold, 1421 lower mold groove, 1422 refractive index matching liquid injection pipeline, 143-optical fiber channel, 144 first optical flat surface, 145-second optical flat surface, 146-third optical flat surface, 147-fourth optical flat surface; 15-optical fiber clamp; 16-optical fiber alignment unit; 17-optical fiber to be processed; 18- LED white light source; 19-electrically controlled θx axis; 20-electrically controlled θz axis; 21-electrically controlled Z axis; 22-electrically controlled Y axis; 23-electrically controlled X axis; 24-tension control unit; 25-unloading roller; 26-loading roller, 27 hose, 28 refractive index matching liquid injection unit, 281-bubble separation liquid pump. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Femtosecond laser point-by-point writing of fiber Bragg grating technology uses a high-power microscope objective to focus the laser beam, and the writing process needs to be carried out under the objective. Due to the surface cylindrical lens effect of the optical fiber cylinder, refraction and secondary focusing occur during the focusing process, resulting in the light spot focused on the fiber core forming a line, and there is a 100-fold size difference between the diameter of the light spot on the fiber core axis and the diameter of the core beam spot. At present, in order to solve this problem, it is necessary to fill the gap between the optical fiber writing point and the objective lens with a refractive index matching liquid. The refractive index of the refractive index matching liquid is about 1.47, which is close to the refractive index of the optical fiber cladding. Filling the refractive index matching liquid can eliminate the effect of the optical fiber cylinder, and the focused light spot also appears circular. However, when continuously writing on the optical fiber, the process of filling the refractive index matching liquid is complicated, the processing cost is high, and the automation is difficult.

[0035] The roll-to-roll fiber grating and array continuous writing system provided by the present invention adopts an open optical fiber channel to fill the refractive index matching liquid, performs continuous refractive index matching liquid injection, and realizes the roll-to-roll continuous writing of the fiber grating, including: a writing laser light source, a feeding roller, a feeding roller, and a writing jig;

[0036] The writing laser light source is preferably in the infrared band. The writing light source in the infrared band has no stray light interference on visual imaging, ensures the imaging consistency of any optical flat surface, improves the stability and accuracy of visual imaging alignment, and especially reduces the interference with the vertical imaging component, that is, the imaging optical path coaxial with the writing laser. The preferred solution is that the writing laser light source has high-precision real-time power monitoring and automatic compensation functions to achieve continuous writing of high-consistency fiber grating arrays.

[0037] The feeding roller is used to release the optical fiber to be inscribed; the lower feeding roller is used to reel in the optical fiber on which the grating has been inscribed; the inscription jig is arranged between the feeding roller and the lower feeding roller;

[0038] The writing jig has an optical fiber channel with at least one end open, the optical fiber passes through the optical fiber channel, and the optical fiber channel is connected to a refractive index matching liquid that maintains hydraulic pressure so that the refractive index matching liquid fills the gap between the optical fiber channel and the optical fiber; the writing jig has a first optical flat surface.

[0039] The refractive index matching liquid injection pipeline is integrated in the writing jig to ensure the consistency of direction when the refractive index matching liquid is injected. The writing jig has a refractive index matching liquid injection pipeline, which is laterally connected to the optical fiber channel. The cross section of the optical fiber channel at the connection point has a concave relative contour to the refractive index matching liquid injection pipeline, which is used to help the optical fiber maintain a stable position in the flow of the refractive index matching liquid. Figure 3 As shown, when the optical fiber is impacted by the injected refractive index matching liquid, it moves in the opposite direction, and the optical fiber channel at the access point is recessed, so that the position of the optical fiber tends to be stable, the lateral movement of the optical fiber is reduced, and the consistency of laser writing is improved.

[0040] In order to keep the position of the optical fiber stable throughout the entire length of the optical fiber channel, the cross section of the optical fiber channel of the writing jig is in the direction opposite to the injection of the refractive index matching liquid, and the inner wall of the optical fiber channel is formed with a groove that matches the cylindrical appearance of the optical fiber, which is an effective improvement solution. Specifically, the optical fiber channel has an axially extending groove, and the cross-sectional profile of the groove at the access point is the concave relative profile of the cross section of the optical fiber channel at the access point and the refractive index matching liquid injection pipeline.

[0041] Preferably, the writing jig comprises an upper mold and a lower mold, and the upper mold and the lower mold are pressed together to form the optical fiber channel; the split writing jig is convenient for optical fiber loading.

[0042] The writing jig is preferably made of quartz glass, which has good optical properties and matches the material of the optical fiber. On the one hand, it is suitable for laser writing, and on the other hand, it is convenient for imaging technology to observe the position and posture of the optical fiber and perform automatic alignment.

[0043] Both ends of the optical fiber channel are open, the optical fiber passes through the optical fiber channel through the open ends, and the refractive index matching liquid flows out through the open ends of the optical fiber channel; preferably, the refractive index matching liquid that flows out is recovered.

[0044] The refractive index matching liquid injection pipeline is connected to the injection pump, and a bubble separator is provided between the refractive index matching liquid injection pipeline and the injection pump to help the narrow gap between the optical fiber and the optical fiber channel to be filled with refractive index matching liquid, thereby ensuring the writing quality and facilitating imaging observation.

[0045] Preferably, the loading roller and the unloading roller apply a preset tension to the optical fiber to help the optical fiber to be in a stable position.

[0046] During laser writing, the refractive index matching liquid forms a stable liquid flow in the optical fiber channel of the writing fixture, so that the optical fiber is in a stable position; the laser emitted by the writing laser light source passes through the first optical flat surface of the writing fixture and irradiates the optical fiber for writing.

[0047] To realize the fully automatic processing, the oil filling problem must be solved, as well as the problem of processing consistency caused by the slight differences in the fiber position under long processing distances due to various factors such as oil pressure, oil buoyancy, and different oil thicknesses during the oil filling process. In order to further improve the processing quality of fiber gratings, the roll-to-roll fiber grating and array continuous writing system of the present invention realizes the observation of the fiber position. The writing fixture is not only filled with refractive index matching liquid and stabilizes the fiber position, but also needs to provide a fiber position observation window. The preferred solution cooperates with the imaging system to realize automatic fiber position calibration or automatic writing parameter control. The specific scheme is as follows:

[0048] The writing jig has a second optical flat surface parallel to the direction in which the refractive index matching liquid is connected to the optical fiber channel, and the projection of the optical fiber being written on the plane where the second optical flat surface is located is within the second optical flat surface. The first optical flat surface is used to receive the writing laser, and the second optical flat surface of the writing jig can be used to continuously observe the position of the optical fiber. In a preferred solution, the second optical flat surface is orthogonal to the first optical flat surface.

[0049] The optical fiber position is observed through the second optical flat surface, and a forward imaging component is used to image the optical fiber at the writing position, and its main optical axis is perpendicular to the second optical flat surface. The forward imaging component can use reflection imaging or transmission imaging. When femtosecond laser is used for writing, transmission imaging is preferred, and the interference of femtosecond laser can be reduced by selecting the transmission light band. When the forward imaging component is used for transmission imaging to observe the optical fiber position, the writing fixture has a third optical flat surface parallel to the second optical flat surface, the optical fiber channel is between the second and third optical flat surfaces, and the projection of the optical fiber at the writing position on the plane where the third optical flat surface is located is within the third optical flat surface; the transmitted light passes through the second and third optical flat surfaces. The forward imaging component includes an illumination light source and an imaging objective lens. The illumination light source and the imaging objective lens are directly opposite to the writing position of the optical fiber, and are respectively located on both sides of the writing fixture, and the main optical axis of the imaging objective lens is perpendicular to the second and third optical flat surfaces of the writing fixture.

[0050] The preferred solution is to observe the position of the optical fiber through an orthogonal dual-axis imaging system using two orthogonal observation planes, thereby determining the spatial posture of the optical fiber, improving the consistency of the state of the optical fiber during continuous writing, and further improving the consistency of the fiber grating writing quality. In addition to the forward imaging component, the orthogonal dual-axis imaging system adds a vertical imaging component for imaging the optical fiber at the writing location, and uses the first optical flat surface of the writing fixture for imaging, and its main optical axis is perpendicular to the first optical flat surface. Similar to the forward imaging component, transmission imaging is preferably used, and the writing fixture has a fourth optical flat surface that is parallel to the first optical flat surface, and the optical fiber channel is between the first and fourth optical flat surfaces; the forward imaging component uses transmitted light to image the optical fiber at the writing location, and the transmitted light passes through the first and fourth optical flat surfaces.

[0051] In some embodiments, the entire side surface of the writing jig is an optically flat surface; in other embodiments, the optically flat surface may be a partial "window" of the writing jig.

[0052] The following are examples:

[0053] The roll-to-roll fiber grating and array continuous writing system provided in this embodiment is as follows: Figure 1 As shown, it includes a writing laser light source, a loading roller 26, a unloading roller 25 and a writing jig 14;

[0054] The writing laser light source includes a femtosecond laser unit, a laser power attenuation unit, and a laser power detection unit which are arranged in sequence. The titanium sapphire femtosecond laser 1 in the femtosecond laser system excites a near-infrared horizontally polarized Gaussian beam with a diameter of 11 mm and a central wavelength of 800 nm and a spectral width of 750-850 nm. The pulse width is 32 fs, the repetition rate is 1000 Hz, and the average power is 7.5 W. After passing through the laser power attenuation system, the femtosecond laser can achieve an extinction ratio of 1:10000, a minimum average power output of 0.75mW, and a single pulse energy of 750nj. The specific process is that the horizontally polarized femtosecond beam can be adjusted to linear polarized light in any direction after passing through the electric zero-order achromatic half-wave plate device 2. After passing through the thin-film polarizer 3, the s-polarized light and the p-polarized light can be separated, the s-polarized light can achieve 90° reflection, and the p-polarized light can achieve transmission. At this time, after passing through another thin-film polarizer 3, the p-polarized light can be almost completely filtered, achieving an ultra-high extinction ratio. At this time, by electrically controlling the glass slide position of the electric zero-order achromatic half-wave plate device 2, the s-polarized light output with any power ratio within 1:10000 can be achieved.

[0055] The laser power detection system can monitor the power of polarization and power modulated femtosecond laser in real time to ensure the consistency of fiber Bragg grating during processing. The specific process is that the modulated femtosecond laser beam splitter 4 (50:50) achieves 50% transmission and 50% reflection. The reflected part of the femtosecond laser will be incident on the thermopile detector 5, and the optical power meter 6 will realize real-time equal power display and data upload. The reflected laser energy is controlled by the PC to realize the monitoring of the transmitted femtosecond laser power.

[0056] The feeding roller 26 is used to release the optical fiber to be written; the unloading roller 25 is used to reel in the optical fiber on which the grating has been written; the writing jig 14 is arranged between the feeding roller and the unloading roller; Figure 2 As shown, optical fiber clamps 15 are provided upstream and downstream of the writing fixture to help stabilize the optical fiber.

[0057] The writing jig includes an upper mold 141 and a lower mold 142. The top view and side view of the upper mold 141 are as shown in FIG. Figure 3 As shown, the upper mold 141 has a through groove 1411 in the length direction of the optical fiber, and the lower mold 142 has a through groove 1421 and a refractive index matching liquid injection pipe 1422 in the length direction of the optical fiber. Figure 4 As shown, the upper mold 141 and the lower mold 142 are pressed together. Figure 5 As shown, groove 1411 and groove 1421 form an optical fiber channel 143 with open ends, whose inner wall is cylindrical. When the refractive index matching liquid is injected through the refractive index matching liquid injection pipe 1422 and impacts the optical fiber, the optical fiber is affected by the fiber of the groove 1411 of the upper mold 141, thereby maintaining a stable position.

[0058] refer to Figure 7 The refractive index matching liquid injection unit 28 includes: a bubble separation liquid pump 281. The top cover of the refractive index matching container connects the bubble separation liquid pump 281 and the refractive index matching liquid through a three-port annular valve. The refractive index matching liquid in the container is extracted by the bubble separation liquid pump 281 (peristaltic pump design, the lower part of which is an injection pump connected to the bubble separator in the upper part) and flows to the writing fixture through a hose.

[0059] Orthogonal dual-axis imaging system, including forward imaging components ( Figure 7 ) and vertical imaging components ( Figure 1 Reference Figure 1 , Figures 5 to 7 The writing jig 14 includes a first optical flat surface 144, a second optical flat surface 145, a third optical flat surface 146, and a fourth optical flat surface 147. The first optical flat surface is 15 mm away from the achromatic long working distance objective lens 13 which is also a laser light source writing objective lens, so as to ensure that the optical fiber channel 143 is 18 mm away from the achromatic long working distance objective lens 13 which is also a vertical imaging component of the laser light source writing objective lens. The lower mold 142 has an integrated refractive index matching liquid injection tube 1422, and its opening is connected to the refractive index matching liquid injection unit 28 through a hose 27.

[0060] Vertical imaging components, such as Figure 1 As shown, it is composed of an LED light source 18, a dichroic mirror 9, a sleeve lens 10, a color CCD 11, and an achromatic long working distance objective lens 13, wherein the 9-dichroic mirror can achieve high reflection of the near-infrared band 750-850nm. After high reflection, the femtosecond laser passes through the 13-achromatic long working distance objective lens to achieve spot focusing compression. The size of the compressed focal spot is about 0.5um, realizing the writing optical path function. Then, the visible white light is emitted by the 18-LED white light source, enters through the fourth optical flat surface, passes through the 17-optical fiber to be processed, and outputs through the first optical flat surface. After passing through the 13-achromatic long working distance objective lens, the imaging spot is about 10mm, and after passing through the 9-dichroic mirror, a high transmittance of 400-750nm is achieved. Through the 10-sleeve lens, infinity-corrected visual imaging is achieved, and finally a high-definition imaging area of ​​the optical fiber to be processed is obtained in the 11-color CCD, realizing the vertical imaging component function. Reference Figure 8 .

[0061] Forward imaging components, such as Figure 7As shown: It is composed of an LED light source 18, a color CCD 11, and an achromatic long working distance objective lens 13. The LED light source 18 emits a white light beam, enters through the second optical flat surface 145, passes through the optical fiber to be processed in the writing fixture, and then outputs through the third optical flat surface 146, enters the achromatic long working distance objective lens 13 for imaging, and finally obtains a forward high-definition imaging area of ​​the optical fiber to be processed in the color CCD 11. Fig. 9 .

[0062] Combined with the dual-axis imaging system, laser writing optical path, high-precision displacement system, refractive index matching liquid injection system and optical fiber transmission system, the writing process of fiber gratings and arrays is completed:

[0063] Through the coordinated work of the engraving fixture 14 and the orthogonal dual-axis imaging system, the bubble separation liquid pump 281 realizes bubble-free processing of the matching liquid, and the refractive index matching liquid is continuously injected into the optical fiber channel 143 with open ends formed by the combination of the grooves of the quartz glass upper mold 141 and the grooves of the quartz glass lower mold 142, filling the gap between the optical fiber 17 and the optical fiber channel 143, thereby achieving high degrees of freedom and high repeatability of the optical fiber 17 in the middle area, and the relative position confirmation and high repeatability adjustment of the optical fiber and the quartz mold are realized through the detection unit in the automatic refractive index matching liquid injection system.

[0064] In the high-precision displacement system and the refractive index matching liquid injection system, the optical fiber 17 to be processed can be freely moved in five directions by the optical fiber alignment unit 16, and the optical fiber position at this time can be visually identified, such as Fig.10 As shown, algorithm compensation is performed with the input standard processing position, and the electrically controlled θx axis 19; electrically controlled θz axis 20; electrically controlled Z axis 21; electrically controlled Y axis 22; and electrically controlled X axis 23 automatically control the position correction of the optical fiber to be processed to achieve high consistency of the processing positions X, Y, Z, θx, and θz.

[0065] In the optical fiber transmission system, the optical fiber 17 to be processed is placed on the loading roller 26 through a large plate, passes through the optical fiber pulling guide wheel, passes through the optical fiber clamp 15 and the writing fixture 14, and then passes through the 16-optical fiber alignment unit and the 24-tension control unit to achieve the alignment of the optical fiber θz and the control of the tension to ensure the consistency of the central wavelength of the processed optical fiber grating. After passing through the optical fiber pulling guide wheel, it is wound onto the large plate of the unloading unit 25 to realize the automated processing of the optical fiber grating array.

[0066] The specific processing steps of this system are as follows:

[0067] Step 1: Install the large disk of optical fiber to be processed onto the loading roller 26, lead the head optical fiber to the optical fiber guide wheel, and then pass it through the optical fiber clamp 15 and the writing fixture 14, and then pass through the optical fiber alignment unit 16 and the tension control unit 24, and then pass through the optical fiber pulling guide wheel, and wrap it around the large disk on the unloading roller 25.

[0068] Step 2: Input the specific indicators of the fiber grating to be processed (including core NA, grating area length, central wavelength, reflectivity, bandwidth, side mode suppression ratio, grating spacing, grating order) on the computer, and the computer will automatically calculate the processing energy, processing method, processing time, displacement speed and processing tension. The laser power attenuation system is used to modulate the processing energy through the laser power detection system, and the fiber position, processing method (toe-cut or non-toe-cut) and displacement speed are controlled through the high-precision displacement system. The processing tension and processing spacing are controlled through the optical fiber transmission system, and the processing position and processing time are controlled through the visual system.

[0069] Step 3: After the optical fiber transmission system moves to a specific position, a pre-processing instruction is given, the tension control unit 24 moves to the calculated tension value, the optical fiber clamp 15 completes the optical fiber clamping, the writing fixture 14 injects the refractive index matching liquid, and the current optical fiber position is identified through the visual system (x1, y1, z1), (x2, y2, z2) and (x3, y3, z3), and the matrix calculation is performed with the set processing position (x, y, z), and the high-precision displacement system is controlled to perform position compensation of X, Y, Z, θx, θz, and then the optical fiber alignment unit 16 performs external force alignment on the optical fiber in the Z direction.

[0070] Step 4: After the processing position is positioned, the computer gives a processing instruction. The processing time T and displacement uniform speed Vx, Vy, and Vz are calculated by the input fiber grating indicators. The high-precision displacement system is controlled to move to the set uniform speed Vx, Vy, and Vz, and the high-speed electronic shutter 8 is synchronously controlled to open for T time to input femtosecond laser. After a single fiber grating processing is realized, refer to Fig.10 , turn off the high-speed electronic shutter.

[0071] Step 5: After completing the processing of a single fiber Bragg grating, the computer controls the fiber clamp 15 and the fiber alignment unit 16 to relax, gives fiber movement instructions, controls the fiber transmission system to move the set grating spacing, and repeats steps 1-5 to achieve fully automated processing of the fiber Bragg grating array.

[0072] After the fiber grating is processed, the optical index test is carried out by using a spectrometer. Fig.11 The specific processing indicators of the fiber Bragg grating input on the PC end are: polyimide fiber (core NA=1.44), grating length 8mm, center wavelength 1532nm, reflectivity 70%, bandwidth 0.25nm, side mode suppression ratio>15dB, grating spacing 2000mm, grating order 1. The actual test results are: center wavelength 1532.345nm, reflectivity 78.122%, bandwidth 0.258nm, side mode suppression ratio 30.346dB.

[0073] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A roll-to-roll fiber Bragg grating and array continuous writing system, characterized in that: It includes a writing laser light source, a loading roller, a unloading roller and a writing jig; The feeding roller is used to release the optical fiber to be inscribed; the lower feeding roller is used to reel in the optical fiber on which the grating has been inscribed; the inscription jig is arranged between the feeding roller and the lower feeding roller; The writing jig has an optical fiber channel with at least one end open, the optical fiber passes through the optical fiber channel, and the optical fiber channel is connected to a refractive index matching liquid that maintains hydraulic pressure, so that the refractive index matching liquid fills the gap between the optical fiber channel and the optical fiber; the writing jig has a first optical flat surface; the writing jig has a refractive index matching liquid injection pipeline, the refractive index matching liquid injection pipeline is laterally connected to the optical fiber channel, and the cross-section of the optical fiber channel at the connection point has a concave relative profile to the refractive index matching liquid injection pipeline, which is used to help the optical fiber maintain a stable position in the flow of the refractive index matching liquid; the optical fiber channel has an axially extending groove, and the cross-sectional profile of the groove at the connection point is the concave relative profile of the cross-section of the optical fiber channel at the connection point and the refractive index matching liquid injection pipeline; the writing jig includes an upper mold and a lower mold, and the upper mold and the lower mold are pressed together to form the optical fiber channel; During laser writing, the refractive index matching liquid forms a stable liquid flow in the optical fiber channel of the writing fixture, so that the optical fiber is in a stable position; the laser emitted by the writing laser light source passes through the first optical flat surface of the writing fixture and irradiates the optical fiber for writing.

2. The roll-to-roll fiber Bragg grating and array continuous writing system according to claim 1, characterized in that: The writing jig is made of quartz glass.

3. The roll-to-roll fiber grating and array continuous writing system according to claim 1, characterized in that: The refractive index matching liquid injection pipeline is connected to the injection pump, and a bubble separator is provided between the refractive index matching liquid injection pipeline and the injection pump; both ends of the optical fiber channel are open, the optical fiber passes through the optical fiber channel through the open ends, and the refractive index matching liquid flows out through the open end of the optical fiber channel; The outflowing refractive index matching liquid is recovered; the upper material roller and the lower material roller apply a preset tension to the optical fiber to help the optical fiber to be in a stable position.

4. The roll-to-roll fiber Bragg grating and array continuous writing system according to any one of claims 1 to 3, characterized in that: The writing fixture has a second optical flat surface parallel to the direction in which the refractive index matching liquid is connected to the optical fiber channel, and the projection of the optical fiber for writing on the plane where the second optical flat surface is located is within the second optical flat surface; the second optical flat surface is orthogonal to the first optical flat surface.

5. The roll-to-roll fiber Bragg grating and array continuous writing system according to claim 4, characterized in that: It also includes a forward imaging component for imaging the optical fiber at the writing position, and its main optical axis is perpendicular to the second optical flat surface.

6. The roll-to-roll fiber grating and array continuous writing system according to claim 5, characterized in that: The writing jig has a third optical flat surface parallel to the second optical flat surface, the optical fiber channel is located between the second and third optical flat surfaces, and the projection of the optical fiber at the writing location on the plane where the third optical flat surface is located is within the third optical flat surface; the forward imaging component uses transmitted light to image the optical fiber at the writing location, and the transmitted light passes through the second and third optical flat surfaces.

7. The roll-to-roll fiber grating and array continuous writing system according to claim 6, characterized in that: The forward imaging component includes an illumination light source and an imaging objective lens. The illumination light source and the imaging objective lens are directly facing the optical fiber where writing is performed, and are located on both sides of the writing fixture. The main optical axis of the imaging objective lens is perpendicular to the second and third optical flat surfaces of the writing fixture.

8. The roll-to-roll fiber grating and array continuous writing system according to claim 1, characterized in that: It also includes a vertical imaging component for imaging the optical fiber at the writing position, and its main optical axis is perpendicular to the first optical flat surface.

9. The roll-to-roll fiber grating and array continuous writing system according to claim 8, characterized in that: The writing jig has a fourth optical flat surface parallel to the first optical flat surface, and the optical fiber channel is located between the first and fourth optical flat surfaces; the vertical imaging component uses transmitted light to image the optical fiber at the writing location, and the transmitted light passes through the first and fourth optical flat surfaces.

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