A fiber grating area coating device

Abstract

The application discloses a kind of grating area coating devices of fiber grating, including optical fiber fastening platform, coating mechanism and three-dimensional fine adjustment mechanism.Optical fiber fastening platform includes bottom plate, left fastening mechanism is fixedly connected to the left side of upper end of bottom plate, right fastening mechanism is fixedly connected to the right side of upper end of bottom plate by X-axis fine adjustment platform;Coating mechanism includes fixed table, micro-feeding mechanism is fixedly connected to the upper side of fixed table, sample feeder is fixed to the middle side of fixed table, coating and heat curing platform is fixedly connected to the lower side of fixed table;Three-dimensional fine adjustment mechanism includes X-axis moving table, YZ-axis fine adjustment platform is fixedly connected to the upper end of X-axis moving table by T-shaped connecting piece;Coating mechanism and three-dimensional fine adjustment mechanism are fixedly connected by connecting piece.The application can realize the coating of specified position and length grating area on optical fiber by longitudinal fastening and transverse pre-tightening optical fiber of optical fiber fastening platform, dropping trace amount of coating liquid on glass block by sample feeder, three-dimensional fine adjustment mechanism drives coating mechanism, and coating layer thickness is controllable and uniformity is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber coating, and particularly relates to a grating area coating device for fiber grating. BACKGROUND

[0002] About 60% of the total water consumption of the whole society is used for farmland, but only about 40% of the water used in the way of field flooding is effectively utilized. Unreasonable irrigation methods will directly affect the quality and yield of crops, and also cause serious waste of water resources. Therefore, accurate detection of soil moisture content (humidity) is of great significance for guiding precision irrigation.

[0003] Traditional soil moisture content detection methods mainly include drying method, dielectric method and neutron instrument method. These methods have problems such as large workload, poor data timeliness, and only obtaining soil surface moisture content data, and thus cannot meet the actual needs of soil moisture content detection.

[0004] With the development of optical fiber sensing technology, a soil moisture content sensor based on polyimide-fiber grating can be developed for soil moisture content detection. The working principle is that when the soil humidity changes, the polyimide in the grating area of the fiber grating expands / contracts to cause strain, resulting in a change in the Bragg wavelength. The measurement process is also affected by temperature. According to theoretical research, the effects of humidity and temperature on the Bragg wavelength are independent and linearly superimposable. Based on this principle, when detecting soil humidity, one fiber grating with a grating area coated with polyimide is used to sense temperature and humidity, and another fiber grating with a grating area not coated with polyimide is used to sense temperature only, so as to compensate for temperature. Due to the multiplexing characteristics of optical fiber transmission, if a soil moisture content sensor is made of a fiber grating with axially spaced grating areas and different center wavelengths, soil moisture content detection at different depths can be realized.

[0005] The key to developing a soil moisture content sensor based on polyimide-fiber grating lies in how to uniformly coat a certain thickness of polyimide on the specified position and length of the grating area of the optical fiber. The existing optical fiber coating equipment is mostly based on mold coating method, that is, the optical fiber is placed in a mold filled with polyimide solution, and then the mold and the optical fiber are separated after solidification. However, this method has problems such as high requirement for manufacturing precision of the mold, uncontrollable position and length of the coating layer, and cannot be effectively used for grating area coating of fiber grating. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a grating area coating device for fiber grating to solve the technical problem that the specified length and grating area on the optical fiber cannot be coated with high quality, and the thickness of the obtained coating layer is controllable and has good uniformity.

[0007] The application adopts the following technical scheme:

[0008] A fiber grating area coating device, comprising a coating mechanism for coating and heat curing of a fiber grating area, the coating mechanism being connected with a three-dimensional fine adjustment mechanism for adjusting the three-dimensional position of the coating mechanism so that the fiber is located at the center of a spherical polyimide solution formed by the coating mechanism, the fiber being fastened longitudinally on a fiber fastening platform, and the fiber fastening platform being used to apply a transverse pre-tightening force to the fiber.

[0009] Specifically, the fiber fastening platform comprises a base plate, left and right sides of the upper end of the base plate being provided with left and right fastening mechanisms of the same structure, and an X-axis fine adjustment platform being arranged between the right fastening mechanism and the base plate.

[0010] Further, the left fastening mechanism comprises a left fastening table, a left fastening nut being arranged at the center of the upper layer of the left fastening table, the left fastening nut being connected with a left fastening bolt, the lower end of the left fastening bolt being connected with the upper end of a left piston rod, the lower end of the left piston rod being connected with a left piston in sequence after passing through a left piston rod return spring and a left piston cylinder, the left piston cylinder being connected with the left fastening table through a left pressing plate, the left piston cylinder being located at the center of the middle layer of the left fastening table, and a square groove for placing the fiber being formed in the X-axis direction central axis of the lower layer of the left fastening table.

[0011] Further, the X-axis fine adjustment platform comprises an X-axis fine adjustment platform lower plate, the X-axis fine adjustment platform lower plate being provided with an X-axis fine adjustment platform upper plate above, the X-axis fine adjustment platform lower plate being provided with T-shaped grooves on both sides of the X-axis direction central axis of the upper end of the X-axis fine adjustment platform lower plate, the X-axis fine adjustment platform upper plate being provided with T-shaped bosses on both sides of the X-axis direction central axis of the lower end of the X-axis fine adjustment platform upper plate, and the X-axis direction connection being realized through the T-shaped grooves and the T-shaped bosses.

[0012] The X-axis fine adjustment platform lower plate is provided with a square boss on the right side of the front end of the X-axis fine adjustment platform lower plate, an internal thread through hole being formed in the X-axis direction central axis of the right end of the square boss, the X-axis fine adjustment platform upper plate being provided with a cylindrical boss on the left side of the front end of the X-axis fine adjustment platform upper plate, an X-axis fine adjustment platform fine adjustment column being connected with the internal thread through hole in a matched manner, the front end of the X-axis fine adjustment platform fine adjustment column being in contact connection with the right end of the cylindrical boss, the rear end of the X-axis fine adjustment platform lower plate being provided with a locking plate, the locking plate being provided with a through slot, and the X-axis fine adjustment platform upper plate being connected with the locking plate through a locking bolt passing through the through slot.

[0013] The X-axis fine adjustment platform lower plate and the X-axis fine adjustment platform upper plate are provided with a return spring for preventing X-axis sliding.

[0014] Specifically, the coating mechanism comprises a fixed table, the fixed table being vertically arranged, and a micro-feeding mechanism, a sample feeder and a coating and heat curing platform being arranged in sequence from top to bottom.

[0015] Further, the micro-feeding mechanism comprises a sample feeding nut fixing seat, one end of the sample feeding nut fixing seat is connected with the fixing table, a through hole is formed on the left side of the front end of the sample feeding nut fixing seat, a counter bore is formed on the right side of the upper end of the sample feeding nut fixing seat, a sample feeding nut is fixed in the counter bore, and a sample feeding bolt is connected with the sample feeding nut in a matched manner.

[0016] Further, the coating and heat curing platform comprises a base, a through hole for fixing an annular heating pipe is formed on the left end of the base, a square groove for fixing a glass block is formed on the right side of the upper end of the base, and the side of the optical fiber is tangent to the upper end of the glass block along the X-axis of the glass block to the central axis.

[0017] Specifically, the three-dimensional fine adjustment mechanism comprises an X-axis moving table, a T-shaped connecting piece is arranged on the X-axis moving table, the T-shaped connecting piece is connected with the coating mechanism through a YZ-axis fine adjustment platform and a connecting piece.

[0018] Further, the X-axis moving table comprises an X-axis moving table base, a guide rail is arranged on the X-axis moving table base, a sliding block is arranged on the guide rail, a lead screw is arranged on the sliding block, one end of the lead screw is connected with a left lead screw bearing, and the other end of the lead screw is connected with a stepping motor through a right lead screw bearing and a coupling.

[0019] Further, the YZ-axis fine adjustment platform comprises, from bottom to top, a YZ-axis fine adjustment platform lower plate, a YZ-axis fine adjustment platform middle plate and a YZ-axis fine adjustment platform upper plate, a lower reset spring is arranged between the YZ-axis fine adjustment platform lower plate and the YZ-axis fine adjustment platform middle plate, and an upper reset spring is arranged between the YZ-axis fine adjustment platform middle plate and the YZ-axis fine adjustment platform upper plate.

[0020] The YZ-axis fine adjustment platform upper plate and the YZ-axis fine adjustment platform middle plate are connected in the Y-axis direction and the Z-axis direction through a T-shaped boss and a groove in cooperation;

[0021] The upper reset spring and the lower reset spring prevent the YZ-axis fine adjustment platform upper plate and the YZ-axis fine adjustment platform middle plate from freely sliding in the Y-axis direction, and prevent the YZ-axis fine adjustment platform middle plate and the YZ-axis fine adjustment platform lower plate from freely sliding in the Z-axis direction.

[0022] The YZ-axis fine adjustment platform lower plate and the YZ-axis fine adjustment platform middle plate are provided with a YZ-axis fine adjustment platform lower fine adjustment column and a lower locking plate, the YZ-axis fine adjustment platform lower fine adjustment column is used to cause the YZ-axis fine adjustment platform lower plate and the YZ-axis fine adjustment platform middle plate to relatively displace in the Z-axis direction, and the lower locking plate is used to prevent the YZ-axis fine adjustment platform middle plate and the YZ-axis fine adjustment platform lower plate from relatively drifting in the Z-axis direction.

[0023] YZ axis fine adjustment platform upper fine adjustment column and an upper locking plate are arranged between the YZ axis fine adjustment platform upper plate and the YZ axis fine adjustment platform middle plate, the YZ axis fine adjustment platform upper fine adjustment column is used for causing the YZ axis fine adjustment platform upper plate and the YZ axis fine adjustment platform middle plate to produce relative displacement along the Y axis, and the upper locking plate is used for preventing the YZ axis fine adjustment platform middle plate and the YZ axis fine adjustment platform upper plate from producing relative drift along the Y axis

[0024] Compared with the prior art, the present application has at least the following beneficial effects:

[0025] A fiber grating grating region coating device, comprising a fiber fastening platform, a coating mechanism and a three-dimensional fine adjustment mechanism, wherein the bottom plate of the fiber fastening platform has a counterbore groove on the left and right sides of the lower end, the left fastening mechanism is fixed to the upper left side of the bottom plate through the left counterbore groove, the right fastening mechanism is fixed to the X-axis fine adjustment platform, the X-axis fine adjustment platform is fixed to the upper right side of the bottom plate through the right counterbore groove, and the counterbore groove can adjust the distance between the left and right fastening mechanisms along the X-axis on the bottom plate to fix different lengths of optical fibers.

[0026] Further, the grating region of the horizontally placed fiber grating is coated, so that the left and right fastening mechanisms fixed to the upper left and right sides of the bottom plate can realize longitudinal fastening of the optical fiber to prevent circumferential drift of the optical fiber during coating, thereby affecting the coating quality; at the same time, the optical fiber needs to have a certain axial pre-tightening force during coating, and the pre-tightening force is in the order of micro-newtons to prevent axial breakage of the optical fiber, so that the X-axis fine adjustment platform can realize the application of the axial pre-tightening force to the optical fiber while ensuring that the optical fiber is not damaged by transversely fine-adjusting the right fastening mechanism.

[0027] Further, the left fastening mechanism and the right fastening mechanism are similar in structure, the left (right) fastening platform is divided into three layers of upper, middle and lower, the center of the upper layer is fixed with a left (right) fastening nut matched with a left (right) fastening bolt, the center of the middle layer is provided with a left (right) piston cylinder fixed by a left (right) pressing plate, and the lower layer is provided with a square groove at the X-axis center axis for placing the optical fiber, and the lower end of the left (right) fastening bolt is smeared with lubricating oil, so that the left (right) piston can realize longitudinal fastening of the optical fiber by rotating the left (right) fastening bolt to feed and push the left (right) piston rod.

[0028] Further, the upper and lower plates of the X-axis fine adjustment platform are connected through T-shaped boss groove matching, and the reset spring prevents the upper and lower plates of the X-axis fine adjustment platform from sliding freely along the X-axis. The right side of the X-axis fine adjustment platform fine adjustment column is knurled straight, which can increase the friction when being screwed. The left side of the X-axis fine adjustment platform fine adjustment column is externally threaded, which is matched with the internally threaded hole of the square boss on the right side of the front end of the lower plate of the X-axis fine adjustment platform. The matching is essentially a precision threaded pair, that is, the thread has a very small pitch. Therefore, screwing the X-axis fine adjustment platform fine adjustment column can cause a small relative displacement of the upper and lower plates of the X-axis fine adjustment platform along the X-axis, that is, the transverse pre-tightening of the optical fiber can be realized. After the fine adjustment is completed, the locking bolt is tightened to prevent the upper and lower plates of the X-axis fine adjustment platform from producing relative drift along the X-axis.

[0029] Further, the upper side of the sample feeding bolt of the coating mechanism is knurled straight, which can increase the friction when being screwed. The matching of the sample feeding bolt nut is essentially a precision threaded pair, that is, the thread has a very small pitch. The lower end of the sample feeding bolt is smeared with lubricating oil on the upper end of the sample feeder piston rod. Therefore, screwing the sample feeding bolt to feed the sample feeder piston rod on the middle side of the fixed table can realize the dropping of a small amount of coating liquid on the glass block, so as to ensure the controllable thickness of the coating layer. The sample nut fixing seat is fixed on the upper side of the fixed table through the through slot on the upper side of the fixed table, and the through slot can realize the adjustment of the height of the sample nut fixing seat in the vertical direction, so as to adapt to sample feeders of different lengths.

[0030] Further, the coating principle of the coating device is based on the improvement of the traditional horizontal pulling and lifting coating method, that is, by controlling the amount of polyimide in the solution pool, the controllable thickness of the coating layer is ensured, and the performance of the developed soil moisture sensor is excellent. Therefore, the micro-feeding mechanism can realize the dropping of a small amount of coating liquid on the glass block by screwing the sample feeding bolt to feed the sample feeder piston rod on the middle side of the fixed table, and the controllable thickness of the gate region coating layer can be realized.

[0031] Further, the through hole at the left end of the base on the lower side of the fixed table is used to fix the annular heating tube, and the annular heating tube can realize the heat curing of the coating layer. The square groove on the right side of the upper end of the base is fixed with a glass block, and the coating process occurs on the upper end of the glass block, which is conducive to the adjustment of the three-dimensional position of the coating mechanism, and also allows the operator to clearly observe the entire coating process, so as to adjust the parameters in time to ensure the coating quality.

[0032] Further, the X-axis moving table of the three-dimensional fine adjustment mechanism is essentially a ball screw sliding table, which includes an X-axis moving table base, a guide rail, a left screw rod bearing, a bearing seat, a right screw rod bearing, a sliding block, and a screw rod. The right side of the screw rod can be connected with a stepping motor through a coupling, and the coating mechanism is fixed on the sliding block through the three-dimensional fine adjustment mechanism. Therefore, by controlling the speed and direction of the stepping motor, the high-quality coating and heat curing process of the specified position and length gate region on the optical fiber can be realized.

[0033] Further, the upper and middle plates of the YZ axis fine adjustment platform and the middle and lower plates are connected in Y and Z axial directions respectively through T-shaped boss groove cooperation, the upper and lower reset springs can prevent the upper and middle plates of the YZ axis fine adjustment platform from sliding freely along the Y axial direction and the middle and lower plates of the YZ axis fine adjustment platform from sliding freely along the Z axial direction respectively, one side of the upper and lower fine adjustment columns of the YZ axis fine adjustment platform is knurled straight line, which can increase the friction when being screwed, the other side of the upper and lower fine adjustment columns of the YZ axis fine adjustment platform is external thread, which is essentially a precision threaded pair with the internal threaded through hole of the square boss of the middle and upper plates of the YZ axis fine adjustment platform, that is, the thread has very small pitch, therefore, screwing the upper and lower fine adjustment columns of the YZ axis fine adjustment platform can respectively cause the upper and middle plates of the YZ axis fine adjustment platform to produce a small relative displacement along the Y axial direction and the upper and middle plates of the YZ axis fine adjustment platform to produce a small relative displacement along the Z axial direction, that is, the two-dimensional position fine adjustment of the coating mechanism can be realized, so as to ensure that the obtained coating layer is good in uniformity, and after the fine adjustment is completed, the locking bolts are screwed tightly to prevent the upper and middle plates of the YZ axis fine adjustment platform from producing a relative drift along the Y axial direction and the middle and lower plates of the YZ axis fine adjustment platform from producing a relative drift along the Z axial direction respectively.

[0034] In summary, the application realizes the coating of the specified position and length grating area of the optical fiber through the longitudinal fastening and transverse pre-tightening of the optical fiber fastening platform, the dropping of the micro coating liquid on the glass block by the sample feeder, and the driving of the coating mechanism by the three-dimensional fine adjustment mechanism, and the obtained coating layer is good in thickness control and uniformity.

[0035] The technical solutions of the application will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a general structure diagram of the grating area coating device of an optical fiber grating in the embodiment of the application;

[0037] Figure 2 It is an axonometric view of a T-shaped connecting piece in the embodiment of the application;

[0038] Figure 3 It is an axonometric view of a connecting piece in the embodiment of the application;

[0039] Figure 4 It is a bottom view of a bottom plate of an optical fiber fastening platform in the embodiment of the application;

[0040] Figure 5 It is a half-cut axonometric view of a left fastening mechanism in the embodiment of the application;

[0041] Figure 6 It is an axonometric view of a left fastening mechanism in the embodiment of the application;

[0042] Figure 7 It is a half-cut axonometric view of a left fastening mechanism in the embodiment of the application;

[0043] Figure 8Figure 1 is a half-projection axonometric view of the right fastening platform in an embodiment of the present application;

[0044] Figure 9 Figure 2 is an axonometric view of the right fastening mechanism in an embodiment of the present application;

[0045] Figure 10 Figure 3 is a half-projection axonometric view of the right fastening mechanism in an embodiment of the present application;

[0046] Figure 11 Figure 4 is a structure and assembly schematic view of the X-axis fine adjustment platform in an embodiment of the present application;

[0047] Figure 12 Figure 5 is a structure and assembly schematic view of the coating mechanism in an embodiment of the present application;

[0048] Figure 13 Figure 6 is a structure schematic view of the X-axis moving stage in an embodiment of the present application;

[0049] Figure 14 Figure 7 is a structure and assembly schematic view of the YZ-axis fine adjustment platform in an embodiment of the present application;

[0050] Figure 15 Figure 8 is a relative position schematic view of the optical fiber, polyimide droplet and glass block in the coating and heat curing process in an embodiment of the present application;

[0051] Figure 16 Figure 9 is a coating principle schematic view of the grating region coating device of a fiber grating in an embodiment of the present application.

[0052] 1. optical fiber fastening platform;

[0053] 10. bottom plate; 11. left fastening mechanism; 110. left fastening platform; 111. left fastening nut; 112. left fastening bolt; 113. left piston rod; 114. left piston; 115. left piston rod return spring; 116. left piston cylinder; 117. left pressing plate; 12. right fastening mechanism; 120. right fastening platform; 121. right fastening nut; 122. right fastening bolt; 123. right piston rod; 124. right piston; 125. right piston rod return spring; 126. right piston cylinder; 127. right pressing plate; 13. X-axis fine adjustment platform; 130. X-axis fine adjustment platform lower plate; 131. X-axis fine adjustment platform upper plate; 132. return spring; 133. X-axis fine adjustment platform fine adjustment column; 134. locking plate; 135. locking bolt;

[0054] 2. coating mechanism;

[0055] 20. fixed table; 21. micro-feeding mechanism; 210. sample feeding nut fixing seat; 211. sample feeding nut; 212. sample feeding bolt; 22. sample feeder; 220. sample feeder piston rod; 221. sample feeder piston; 222. sample feeder piston cylinder; 23. coating and thermal curing platform; 230. base; 231. annular heating tube; 232. glass block;

[0056] 3. three-dimensional fine adjustment mechanism;

[0057] 30. X-axis moving table; 301. guide rail; 302. left screw shaft bearing; 303. bearing seat; 304. right screw shaft bearing; 305. sliding block; 306. screw shaft; 31. YZ-axis fine adjustment platform; 310. YZ-axis fine adjustment platform lower plate; 311. YZ-axis fine adjustment platform middle plate; 312. YZ-axis fine adjustment platform upper plate; 313. lower reset spring; 314. YZ-axis fine adjustment platform lower fine adjustment column; 315. lower locking plate; 316. lower locking bolt; 317. upper reset spring; 318. YZ-axis fine adjustment platform upper fine adjustment column; 319. upper locking plate; 3110. upper locking bolt; 32. T-shaped connecting piece; 33. connecting piece; 4. optical fiber. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0059] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "one side", "one end", "one edge" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0060] In the description of the present application, it should be noted that unless otherwise expressly specified and limited, the terms "mounting", "connection", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, it can be the communication inside two elements, "fixed connection" means that two parts are connected through bolts and nuts, the term "fixed" means that two parts are connected through interference fit or welding, the term "X-axis direction" is the fine adjustment direction of the X-axis fine adjustment platform, the term "Y-axis direction" is the fine adjustment direction of the middle plate and the upper plate of the YZ-axis fine adjustment platform, and the term "Z-axis direction" is the fine adjustment direction of the lower plate and the middle plate of the YZ-axis fine adjustment platform. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0061] It should be understood that the terms "comprising" and "including" as used in the specification and the appended claims indicate the presence of the described features, integers, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0062] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0063] It should be further understood that the term "and / or" as used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations thereof.

[0064] Various structural diagrams according to the disclosed embodiments of the present application are shown in the accompanying drawings. These drawings are not drawn to scale, in which certain details are exaggerated for the purpose of clarity and certain details can be omitted. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are only exemplary, and in actuality, they can deviate due to manufacturing tolerances or technical limitations, and a person skilled in the art can additionally design regions / layers with different shapes, sizes and relative positions according to actual needs.

[0065] The present application provides a fiber grating area coating device. In order to obtain soil moisture data with different depths, the grating area of an optical fiber with axially spaced grating area and different center wavelengths is coated with polyimide according to the multiplexing characteristics of optical fiber transmission, which is used for developing a soil moisture sensor based on polyimide-fiber grating to detect soil moisture.

[0066] Referring to Figure 1 The present application discloses a fiber grating grating area coating device, which comprises a fiber fastening platform 1, a coating mechanism 2 and a three-dimensional fine adjustment mechanism 3. The fiber fastening platform 1 is used to realize the longitudinal fastening of the optical fiber 4 and to apply a transverse pre-tightening force to the optical fiber 4, so that the optical fiber 4 is tightly stretched along the axial direction to facilitate the coating. The coating mechanism 2 is arranged above the optical fiber 4 and is used to drop a trace of coating liquid on the optical fiber 4. The coating mechanism 2 is fixedly connected with the three-dimensional fine adjustment mechanism 3, which is used to realize the three-dimensional position adjustment of the coating and heat curing platform 23 below the optical fiber 4, so as to ensure the smooth progress of the coating and heat curing process and to obtain a coating layer with controllable thickness and good uniformity.

[0067] The fiber fastening platform 1 comprises a base plate 10. The left and right sides of the lower end of the base plate 10 are respectively provided with countersunk hole grooves. A left fastening mechanism 11 is fixedly connected to the left side of the upper end of the base plate 10 through the left countersunk hole groove. An X-axis fine adjustment platform 13 is fixedly connected to the right side of the upper end of the base plate 10 through the right countersunk hole groove. A right fastening mechanism 12 is fixedly connected to the X-axis fine adjustment platform 13.

[0068] The coating mechanism 2 comprises a fixed table 20. The upper side of the fixed table 20 is provided with a through groove. A micro-feeding mechanism 21 is fixedly connected to the upper side of the fixed table 20 through the through groove. A sample feeder 22 is fixed to the middle side of the fixed table 20. The sample feeder 22 is essentially a trace syringe. A coating and heat curing platform 23 is fixedly connected to the lower side of the fixed table 20.

[0069] Referring to Figure 2 and Figure 3 The three-dimensional fine adjustment mechanism 3 comprises an X-axis moving table 30. The X-axis moving table 30 is a ball screw sliding table. The lower end of a T-shaped connecting piece 32 is fixedly connected to the upper end of the X-axis moving table 30. The upper side of the T-shaped connecting piece 32 is fixedly connected with the lower end of a YZ-axis fine adjustment platform 31. The upper end of the YZ-axis fine adjustment platform 31 is fixedly connected with one side of a connecting piece 33. The other side of the connecting piece 33 is fixedly connected with the rear end of the fixed table 20.

[0070] The fiber fastening platform 1 realizes the longitudinal fastening of the optical fiber through the left fastening mechanism 11 and the right fastening mechanism 12. The X-axis fine adjustment platform 13 applies a transverse pre-tightening force to the optical fiber 4, so that the optical fiber 4 is tightly stretched along the axial direction to facilitate the coating.

[0071] The coating mechanism 2 realizes the vertical feeding of the sample feeder piston rod 220 by screwing the sample feeding bolt 212, so as to drop a trace of coating liquid on the glass block 232. The coating process occurs on the upper end of the glass block. Meanwhile, the left end through hole of the base 230 is fixedly provided with a ring-shaped heating tube 231, which can realize the heat curing of the coating layer.

[0072] The coating mechanism 2 is fixed with the three-dimensional fine adjustment mechanism 3, the three-dimensional fine adjustment mechanism 3 is used for adjusting the three-dimensional position of the coating and heat curing platform 23, the coating and heat curing process is ensured to be smoothly carried out, and a coating layer with controllable thickness and good uniformity is obtained.

[0073] Please refer to Figure 4 , the bottom plate 10 is provided with a counterbore groove at the left and right sides of the lower end, the left fastening mechanism 11 is fixed to the left side of the upper end of the bottom plate 10 through the left end counterbore groove, the right fastening mechanism 12 is fixed to the X-axis fine adjustment platform 13, the X-axis fine adjustment platform 13 is fixed to the right side of the upper end of the bottom plate 10 through the right end counterbore groove, and the counterbore groove is designed to adjust the distance between the left fastening mechanism 11 and the right fastening mechanism 12 along the X-axis on the bottom plate 10, so that the optical fiber of different lengths is fixed.

[0074] Please refer to Figure 5 , Figure 6 and Figure 7 , the left fastening table 110 of the left fastening mechanism 11 is divided into upper, middle and lower layers, the left fastening nut 111 is fixed to the center of the upper layer of the left fastening table 110, the left fastening bolt 112 is connected with the left fastening nut 111, the upper side of the left fastening bolt 112 is a star-shaped handle, so as to facilitate the rotation of the left fastening bolt 112, the upper end of the left piston rod 113 is in contact with the lower end of the left fastening bolt 112, and the contact part is coated with lubricating oil, the left piston rod 113 passes through the left piston rod return spring 115 and the left piston cylinder 116 from top to bottom, the lower end of the left piston rod 113 is fixed with the left piston 114, and the left piston cylinder 116 is vertically fixed to the center of the middle layer of the left fastening table 110 by the left compression plate 117; the left fastening table 110 is provided with a square groove at the X-axis central axis of the lower layer for placing the optical fiber 4, before the coating and heat curing process starts, the groove bottom surface and the two side surfaces of the lower layer of the left fastening table 110 are tangent to the side surface of the optical fiber, the longitudinal fastening of the optical fiber by the left piston 114 can be realized by rotating the star-shaped handle of the left fastening bolt 112 to feed the left piston rod 113, and the left piston 114 is made of rubber material, so as to avoid damage to the optical fiber in the longitudinal fastening; after the coating and heat curing process is completed, the star-shaped handle of the left fastening bolt 112 is rotated in the opposite direction, and under the action of the left piston rod return spring 115, the longitudinal fastening force of the optical fiber by the left piston 114 disappears.

[0075] Please refer to Figure 8 , Figure 9 and Figure 10 , the structure and part connection mode of the right fastening mechanism 12 are the same as those of the left fastening mechanism 11.

[0076] Please refer to Figure 11 , the X-axis fine adjustment platform 13 comprises an X-axis fine adjustment platform lower plate 130, an X-axis fine adjustment platform upper plate 131, a return spring 132, an X-axis fine adjustment platform fine adjustment column 133, a locking plate 134 and a locking bolt 135.

[0077] The left end of the X-axis fine adjustment platform lower plate 130 is provided with a square boss, the right end of the square boss is provided with a cylindrical boss, the upper end of the X-axis fine adjustment platform lower plate 130 is provided with T-shaped grooves on both sides of the X-axis, the right side of the front end of the X-axis fine adjustment platform lower plate 130 is provided with a square boss, and the right end of the square boss is provided with an internal threaded hole along the X-axis; the right lower end of the X-axis fine adjustment platform upper plate 131 is provided with a square boss, the left end of the square boss is provided with a cylindrical boss, the lower end of the X-axis fine adjustment platform upper plate 131 is provided with T-shaped bosses on both sides of the X-axis, and the left side of the front end of the X-axis fine adjustment platform upper plate 131 is provided with a square boss, and the right end of the square boss is provided with a cylindrical boss; the X-axis fine adjustment platform lower plate 130 and the X-axis fine adjustment platform upper plate 131 are connected along the X-axis through the cooperation of the T-shaped boss grooves, and the two ends of the reset spring 132 pass through the cylindrical bosses at the X-axis central axes of the X-axis fine adjustment platform lower plate 130 and the X-axis fine adjustment platform upper plate 131 and are fixed to the square bosses at the two ends, so that the X-axis fine adjustment platform lower plate 130 and the X-axis fine adjustment platform upper plate 131 are prevented from freely sliding along the X-axis.

[0078] The left side of the X-axis fine adjustment platform fine adjustment column 133 is externally threaded, and cooperates with the internal threaded hole of the square boss on the right side of the front end of the X-axis fine adjustment platform lower plate 130 to form a precise threaded pair, that is, the thread has a small pitch, the left end of the X-axis fine adjustment platform fine adjustment column 133 is in contact with the right end of the cylindrical boss on the left side of the front end of the X-axis fine adjustment platform upper plate 131, the right side of the X-axis fine adjustment platform fine adjustment column 133 is knurled straight, which can increase the friction when being screwed, the locking plate 134 is fixed to the rear end of the X-axis fine adjustment platform lower plate 130, the locking plate 134 is provided with a through slot, and the locking bolt 135 passes through the through slot and is fixed to the X-axis fine adjustment platform upper plate 131.

[0079] Since the right fastening table 120 is fixed to the upper end of the X-axis fine adjustment platform upper plate 131, and the X-axis fine adjustment platform lower plate 130 is fixed to the right side of the upper end of the bottom plate 10 through the counterbore hole groove on the right side of the bottom plate 10, the X-axis fine adjustment platform upper plate and the X-axis fine adjustment platform lower plate can be slightly relatively displaced along the X-axis by screwing the X-axis fine adjustment platform fine adjustment column 133, so as to exert a transverse pre-tightening force on the optical fiber, the optical fiber is tightly stretched along the axis to facilitate coating, and after the fine adjustment is completed, the locking bolt 135 is screwed tightly to prevent the X-axis fine adjustment platform upper plate and the X-axis fine adjustment platform lower plate from relatively drifting along the X-axis, that is, the transverse pre-tightening force exerted on the optical fiber during coating and heat curing is constant, and the coating and heat curing process is ensured to be smoothly performed.

[0080] Please refer to Figure 12 , the coating mechanism 2 comprises a fixed table 20, a micro-feeding mechanism 21, a sample feeder 22, and a coating and heat curing platform 23, the micro-feeding mechanism 21 comprises a sample feeding nut fixing seat 210, a sample feeding nut 211, and a sample feeding bolt 212, and the coating and heat curing platform 23 comprises a base 230, an annular heating tube 231, and a glass block 232.

[0081] The fixed table 20 has a through slot on the upper side, and the sample injection nut fixing seat 210 is fixed to the upper part of the fixed table 20 through the through slot on the upper side of the fixed table 20. The design of the through slot can realize the adjustment of the height of the sample injection nut fixing seat in the vertical direction, so it can adapt to different lengths of the sample injector. The sample injection nut fixing seat 210 has a through hole on the left side of the front end and a counterbore on the right side of the upper end. The sample injection nut 211 is fixed in the counterbore. The sample injection bolt 212 and the sample injection nut 211 are essentially a precision threaded pair. The thread has a very small pitch. The upper side of the sample injection bolt 212 is knurled straight, which can increase the friction when rotating.

[0082] The fixed table 20 has a counterbore on the middle side in the vertical direction. The sample injector 22 is essentially a micro syringe, which is fixed in the counterbore on the middle side of the fixed table 20. The lower end of the sample injector plunger rod 220 is fixed with the sample injector plunger 221. The upper end of the sample injector plunger rod 220 is in contact with the lower end of the sample injection bolt 212, and the contact is coated with lubricating oil. The lower side of the fixed table 20 is fixed with the coating and heat curing platform 23. The base 230 has a through hole on the left end for fixing the annular heating tube 231. The annular heating tube 231 can realize the heat curing of the coating layer, and the annular heating tube 231 can be connected to the pressure regulating device to realize the slow heating in the heat curing process, preventing the occurrence of thermal stress in the coating layer to affect the quality of the coating layer. The base 230 has a square groove on the right side of the upper end. The glass block 232 is fixed in the square groove. In the coating and heat curing process, the side surface of the optical fiber along the X-axis of the glass block 232 is tangent to the upper end of the glass block 232. Therefore, by rotating the sample injection bolt 212 to feed and push the sample injector plunger rod 220, a small amount of polyimide solution can be dropped on the glass block 232. The amount of polyimide solution depends on the thickness of the coating layer to be obtained. Due to the surface tension of the liquid, a small amount of polyimide solution forms a spherical shape on the upper end of the glass block 232.

[0083] The coating process occurs on the upper end of the glass block, which is beneficial to the adjustment of the three-dimensional position of the coating mechanism, and also allows the operator to clearly observe the entire coating process, so as to adjust the parameters in time to ensure the coating quality.

[0084] Please refer to Figure 13 , the X-axis moving table 30 of the three-dimensional fine adjustment mechanism 3 is essentially a ball screw sliding table, which includes an X-axis moving table base 300, a guide rail 301, a left screw bearing 302, a bearing seat 303, a right screw bearing 304, a sliding block 305, and a screw rod 306. The right side of the screw rod 306 can be connected to the stepping motor through a coupling. The coating mechanism 2 is fixed to the sliding block 305 through the three-dimensional fine adjustment mechanism 3. Therefore, by controlling the speed and direction of the stepping motor, the specified position and length of the grating area on the optical fiber can be coated and heat cured with high quality.

[0085] Please refer to Figure 14The YZ-axis fine adjustment platform 31 comprises a YZ-axis fine adjustment platform lower plate 310, a YZ-axis fine adjustment platform middle plate 311 and a YZ-axis fine adjustment platform upper plate 312, and the structures and the connecting modes of the parts of the YZ-axis fine adjustment platform lower plate 310 and the YZ-axis fine adjustment platform upper plate 312 are similar to those of the X-axis fine adjustment platform lower plate 130, and the structures and the connecting modes of the parts of the YZ-axis fine adjustment platform middle plate 311 are similar to those of the X-axis fine adjustment platform upper plate 131.

[0086] The upper plate and the middle plate of the YZ-axis fine adjustment platform and the middle plate and the lower plate are connected in the Y-axis direction and the Z-axis direction respectively through T-shaped boss groove cooperation, the upper reset spring and the lower reset spring prevent the YZ-axis fine adjustment platform upper plate and the YZ-axis fine adjustment platform middle plate from sliding freely along the Y-axis direction and the YZ-axis fine adjustment platform middle plate and the YZ-axis fine adjustment platform lower plate from sliding freely along the Z-axis direction respectively, one side of the YZ-axis fine adjustment platform upper adjusting column and the YZ-axis fine adjustment platform lower adjusting column is knurled straight line, which can increase the friction when being screwed, the other side of the YZ-axis fine adjustment platform upper adjusting column and the YZ-axis fine adjustment platform lower adjusting column is external thread, which is essentially a precision threaded pair with the internal threaded through hole of the square boss of the YZ-axis fine adjustment platform middle plate and the YZ-axis fine adjustment platform upper plate, that is, the thread has very small pitch, therefore, screwing the YZ-axis fine adjustment platform upper adjusting column and the YZ-axis fine adjustment platform lower adjusting column can respectively make the YZ-axis fine adjustment platform upper plate and the YZ-axis fine adjustment platform middle plate produce a small relative displacement along the Y-axis direction and the YZ-axis fine adjustment platform upper plate and the YZ-axis fine adjustment platform middle plate produce a small relative displacement along the Z-axis direction, that is, the two-dimensional position fine adjustment of the coating mechanism can be realized, so as to ensure that the obtained coating layer is uniform, and after the fine adjustment is completed, the locking bolt is screwed tightly to prevent the YZ-axis fine adjustment platform upper plate and the YZ-axis fine adjustment platform middle plate from producing a relative drift along the Y-axis direction and the YZ-axis fine adjustment platform middle plate and the YZ-axis fine adjustment platform lower plate from producing a relative drift along the Z-axis direction respectively.

[0087] Please refer to Figure 15 The coating principle of the grating region coating device for the fiber grating is similar to the traditional horizontal pulling coating method, that is, the fiber is inserted from one side of the solution pool containing polyimide and is pulled out from the other side, but the thickness, position and length of the obtained coating layer are uncontrollable. In view of the problems existing in the traditional horizontal pulling coating method, the coating device is improved, that is, the amount of polyimide in the solution pool is controlled through the sample injector, due to the surface tension of the liquid, a small amount of polyimide solution presents a spherical shape, and the three-dimensional fine adjustment mechanism drives the coating mechanism, so that the fiber is located at the center of the spherical polyimide solution during the coating and heat curing process, thereby realizing the coating of the specified position and length of the grating region on the fiber, and the obtained coating layer has controllable thickness and good uniformity.

[0088] Please refer to Figure 16 The use method of the grating region coating device for the fiber grating comprises the following steps:

[0089] S1, according to the design requirements of the polyimide-fiber grating-based soil moisture sensor, the length of the fiber to be coated, the grating region length and the axial distribution interval thereof are determined, so that the distance between the left fastening mechanism 11 and the right fastening mechanism 12 is adjusted through the countersunk hole groove on both sides of the bottom plate 10;

[0090] S2, the optical fiber 4 is placed in the groove at the left fastening platform 110 and the X-axis central axis of the lower layer of the left fastening platform 110, and the optical fiber 4 is longitudinally fastened and transversely pre-tightened;

[0091] S3, the sample injector 22 drops a quantitative polyimide solution on the glass block 231 according to needs;

[0092] S4, the three-dimensional fine adjustment mechanism 3 adjusts the three-dimensional position of the coating mechanism 2, so that the optical fiber 4 is at the center of the spherical polyimide solution formed on the glass block 231, so as to ensure that the obtained coating layer is uniform in thickness;

[0093] S5, the X-axis moving platform 30 drives the coating mechanism 2 to realize the coating and heat curing of the grating area on the optical fiber 4;

[0094] S6, after the whole coating process is completed, the three-dimensional fine adjustment mechanism 2 drives the coating mechanism 3 to move away from the optical fiber 4, and then the longitudinal fastening force and the transverse pre-tightening force of the optical fiber fastening platform 1 on the optical fiber 4 are eliminated, at this time, the optical fiber 4 can be taken out.

[0095] In summary, the grating area coating device of the optical fiber grating can realize the coating of the specified position and length grating area on the optical fiber through the longitudinal fastening and transverse pre-tightening of the optical fiber fastening platform, the dropping of the trace coating liquid on the glass block by the sample injector, and the driving of the coating mechanism by the three-dimensional fine adjustment mechanism, the coating layer thickness is controllable and the uniformity is good.

[0096] The above content is only for describing the technical idea of the present application, and cannot limit the protection scope of the present application, any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A grating region coating apparatus for fiber Bragg gratings, characterized in that, The coating mechanism (2) includes a coating mechanism (2) for coating and thermal curing the grid region on the optical fiber (4). The coating mechanism (2) is connected to a three-dimensional fine-tuning mechanism (3). The three-dimensional fine-tuning mechanism (3) is used to adjust the three-dimensional position of the coating mechanism (2) so that the optical fiber (4) is at the center of the spherical polyimide solution formed by the coating mechanism (2). The optical fiber (4) is longitudinally fastened on the optical fiber fastening platform (1). A transverse pre-tightening force is applied to the optical fiber (4) through the optical fiber fastening platform (1). The coating mechanism (2) includes a fixed stage (20). The fixed stage (20) is vertically arranged and has a micro-feeding mechanism (21), a sampler (22), and a coating and thermal curing platform (23) arranged sequentially from top to bottom. The micro-feeding mechanism (21) includes a sampler (22), a sampler (23), and a coating and thermal curing platform (23). The sample nut fixing seat (210) is connected to the fixing platform (20) at one end. The front left side of the sample nut fixing seat (210) has a through hole and the upper right side has a countersunk hole. The sample nut (211) is fixed in the countersunk hole. The sample nut (211) is fitted with a sample bolt (212). The coating and thermosetting platform (23) includes a base (230). The left end of the base (230) has a through hole for fixing the annular heating tube (231). The upper right side of the base (230) has a square groove for fixing the glass block (232). The side of the optical fiber (4) is tangent to the upper end of the glass block (232) along the X-axis of the glass block (232).

2. The fiber optic grating coating apparatus according to claim 1, characterized in that, The fiber optic fastening platform (1) includes a base plate (10). The left and right sides of the upper end of the base plate (10) are respectively provided with a left fastening mechanism (11) and a right fastening mechanism (12) with the same structure. An X-axis fine adjustment platform (13) is provided between the right fastening mechanism (12) and the base plate (10).

3. The fiber optic grating grating coating apparatus according to claim 2, characterized in that, The left fastening mechanism (11) includes a left fastening platform (110). A left fastening nut (111) is provided at the center of the upper layer of the left fastening platform (110). The left fastening nut (111) is connected to the left fastening bolt (112). The lower end of the left fastening bolt (112) is connected to the upper end of the left piston rod (113). The lower end of the left piston rod (113) passes through the left piston rod return spring (115) and the left piston cylinder (116) in sequence and is connected to the left piston (114). The left piston cylinder (116) is connected to the left fastening platform (110) through the left pressure plate (117). The left piston cylinder (116) is located at the center of the middle layer of the left fastening platform (110). A square groove for placing optical fiber (4) is opened at the X-axis centerline of the lower layer of the left fastening platform (110).

4. The fiber optic grating coating apparatus according to claim 2, characterized in that, The X-axis fine-tuning platform (13) includes a lower plate (130) of the X-axis fine-tuning platform and an upper plate (131) of the X-axis fine-tuning platform above the lower plate (130). T-shaped grooves are provided on both sides of the X-axis center axis at the upper end of the lower plate (130), and T-shaped bosses are provided on both sides of the X-axis center axis at the lower end of the upper plate (131). The X-axis connection is achieved through the T-shaped grooves and T-shaped bosses. A square boss is provided on the right side of the front end of the lower plate (130) of the X-axis fine adjustment platform, and an internal threaded through hole is opened along the X-axis at the center of the right end of the square boss. A cylindrical boss is provided on the left side of the front end of the upper plate (131) of the X-axis fine adjustment platform, and an X-axis fine adjustment platform fine adjustment column (133) is connected in the internal threaded through hole. The front end of the X-axis fine adjustment platform fine adjustment column (133) is in contact with the right end of the cylindrical boss. A locking plate (134) is provided at the rear end of the lower plate (130) of the X-axis fine adjustment platform, and a through groove is opened on the locking plate (134). A locking bolt (135) passes through the through groove and is connected to the upper plate (131) of the X-axis fine adjustment platform. A return spring (132) is provided between the lower plate (130) and the upper plate (131) of the X-axis fine-tuning platform to prevent X-axis sliding.

5. The fiber optic grating grating coating apparatus according to claim 1, characterized in that, The three-dimensional fine-tuning mechanism (3) includes an X-axis moving stage (30), on which a T-shaped connector (32) is provided. The T-shaped connector (32) is connected to the coating mechanism (2) via the YZ axis fine-tuning platform (31) and the connector (33).

6. The fiber optic grating coating apparatus according to claim 5, characterized in that, The X-axis moving stage (30) includes an X-axis moving stage base (300), a guide rail (301) is provided on the X-axis moving stage base (300), a slider (305) is provided on the guide rail (301), and a lead screw (306) is provided on the slider (305). One end of the lead screw (306) is connected to the left lead screw bearing (302), and the other end is connected to the stepper motor via the right lead screw bearing (304) and the coupling.

7. The fiber optic grating coating apparatus according to claim 5, characterized in that, The YZ axis fine adjustment platform (31) includes, from bottom to top, a lower plate (310), a middle plate (311), and an upper plate (312). A lower reset spring (313) is provided between the lower plate (310) and the middle plate (311), and an upper reset spring (317) is provided between the middle plate (311) and the upper plate (312). The upper plate (312) of the YZ axis fine adjustment platform and the middle plate (311) of the YZ axis fine adjustment platform, as well as the middle plate (311) of the YZ axis fine adjustment platform and the lower plate (310) of the YZ axis fine adjustment platform, are connected in the Y-axis and Z-axis directions respectively by T-shaped bosses and grooves. The upper reset spring (317) and the lower reset spring (313) prevent the upper plate (312) and the middle plate (311) of the YZ axis fine adjustment platform from sliding freely along the Y axis, and the middle plate (311) and the lower plate (310) of the YZ axis fine adjustment platform from sliding freely along the Z axis, respectively. A lower fine-tuning column (314) and a lower locking plate (315) of the YZ axis fine-tuning platform are provided between the lower plate (310) and the middle plate (311) of the YZ axis fine-tuning platform. The lower fine-tuning column (314) of the YZ axis fine-tuning platform is used to make the lower plate (310) and the middle plate (311) of the YZ axis fine-tuning platform relative to each other along the Z axis. The lower locking plate (315) is used to prevent the middle plate (311) and the lower plate (310) of the YZ axis fine-tuning platform from drifting relative to each other along the Z axis. A fine adjustment column (318) and an upper locking plate (319) are provided between the middle plate (311) and the upper plate (312) of the YZ axis fine adjustment platform. The fine adjustment column (318) is used to make the upper plate (312) and the middle plate (311) of the YZ axis fine adjustment platform generate relative displacement along the Y axis. The upper locking plate (319) is used to prevent relative drift between the middle plate (311) and the upper plate (312) of the YZ axis fine adjustment platform along the Y axis.

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