Chiral multi-core fiber grating array and preparation method thereof

Abstract

The invention relates to the technical field of fiber bragg grating array manufacturing, in particular to a chiral multi-core fiber bragg grating array and a preparation method thereof. The device is characterized by comprising a rotary fiber feeding module, a grating array fiber, a beam combining module, a coating cup and a fiber collecting device. In the preparation process of the chiral multi-core fiber grating array, 1 + N grating array fibers are sent out by the rotary fiber feeding module and then pass through the beam combining module; the rotary fiber feeding module and the beam combining module rotate at the same speed and in the same direction to increase torsion for the 1 + N grating array optical fibers, then the optical fibers are coated and cured through the coating cup to form a chiral multi-core fiber grating array, and then the chiral multi-core fiber grating array is collected into the fiber collecting disc through the fiber collecting device. According to the chiral multi-core fiber grating array and the preparation method, various indexes such as different grating wavelengths, intervals and reflectivity can be selected, the screw pitch can be freely selected, and low-cost long-distance large-scale industrial preparation and torsion monitoring and shape sensing in complex strain conditions can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber grating array manufacturing, and in particular to a chiral multi-core fiber grating array and a preparation method thereof. Background Art

[0002] With the rapid development of various fields in my country, optical fiber plays an important role as a sensing sensitive element and a transmission signal medium in various monitoring systems. As a new type of optical sensing element, fiber Bragg grating shape sensing can realize the monitoring of environmental temperature, stress strain, humidity, pressure and chemical composition changes, etc. It has the advantages of small size, resistance to harsh environment, anti-electromagnetic interference, corrosion resistance, high sensitivity and accuracy, good implantability, etc. Among them, fiber Bragg grating shape sensing technology based on stress strain monitoring plays an important role in many fields such as civil engineering, machinery, aerospace engineering and medicine. Fiber Bragg grating shape sensing technology can be used for structural monitoring, geographical environment and cable pipeline monitoring in the fields of aerospace, industrial machinery and large buildings. In the medical field, it can be used for interventional treatment tracking, medical minimally invasive interventional surgery, intelligent health monitoring, etc. In industry, it can realize the production and manufacturing of industrial robots, showing great application potential with its unique advantages.

[0003] Multi-core fiber is a special type of fiber that contains multiple cores and contains multiple cores in the same outer cladding. The multi-core fiber Bragg grating made by writing fiber Bragg grating in multi-core fiber has all the advantages of multi-core fiber and fiber Bragg grating. The multi-core fiber Bragg grating structure is small in size, resistant to harsh environments, anti-electromagnetic interference, corrosion-resistant, highly sensitive and accurate, has good implantability, and high signal-to-noise ratio. The existing centimeter-level multi-core fiber Bragg grating arrays have been applied to various fields such as medical endoscopes, minimally invasive surgery, wearable devices, and industrial robots. However, due to the small spacing of this multi-core fiber Bragg grating and the short length of the fiber Bragg grating array, shape monitoring cannot be continuous in space, so the shape of the blank area without grating between the measuring points cannot be obtained. Its accuracy is still a certain distance compared with the fiber shape sensor with large core spacing. This multi-core fiber Bragg grating cannot detect large-radius deformations over a large range. In large-scale applications such as pipeline settlement, bridge collapse, and engineering monitoring that require long-distance deformation monitoring, this multi-core fiber Bragg grating has limitations.

[0004] In the preparation process of multi-core fiber grating arrays, the existing preparation technologies use coating removal, single-point grating, non-continuous grating methods or rotating axis grating. The focusing position needs to be manually controlled during the process, which can easily cause the fiber cores at different positions to receive different incident light intensities. The process is difficult to control and has poor repeatability, resulting in inconsistent central wavelengths and reflectivities of the written gratings, which makes the quality of the multi-core fiber grating array low. At the same time, it increases the complexity of the system and the application cost. It is difficult to achieve the requirements of low-cost and efficient preparation of multi-core fiber gratings, cannot be mass-produced, cannot achieve long-distance large-scale preparation, and does not have the conditions for industrial production. At the same time, due to the limitations of the preparation method, the arrangement of the multi-core fiber grating array between different fiber cores is parallel arrangement. The multi-core fiber grating array arranged in this way can monitor a single deformation in actual application, has a small application range, and has many errors. Although it can realize the measurement of bending direction and size and complete the curvature measurement on the orthogonal axis, it is not sensitive to torsion during the deformation monitoring process. It is impossible to quickly locate the area deformed by torque and cannot complete the torsion deformation restoration, which affects the shape sensing accuracy of the multi-core fiber grating.

[0005] In view of the various deficiencies existing in the above-mentioned multi-core fiber grating preparation method, first, the existing preparation technology has high costs in all aspects. Not only do various devices need to be completed to complete the core coupling and grating area calibration, but also the fiber coating needs to be stripped, which increases the preparation steps, time and labor consumption. The required devices are numerous, the preparation system is complex, it is difficult to form industrial preparation and the grating consistency is difficult to control. Second, the multi-core fiber grating spacing is small, the fiber grating array length is short, and there is a blind spot in the measurement point for shape monitoring. The accuracy is not as good as the multi-core fiber grating shape sensor with a large core spacing, and it is impossible to detect long-distance, large-range, and large-radius deformations. Third, the deformation conditions that can be monitored by the parallel-arranged multi-core fiber grating array in actual applications are single, the application range is small, the errors are large, and torsional strain cannot be monitored. Fourth, the prepared multi-core fiber grating is not flexible enough, and it is difficult to flexibly configure the number of gratings and the core spacing according to actual conditions. The invention relates to a method for preparing a chiral multi-core fiber grating array. The method is based on completing fixed-point grating in the process of preparing optical fiber by a drawing tower. The method takes advantage of the ability of the drawing tower to prepare optical fiber gratings over long distances. The preparation method of the invention can realize the preparation of large-scale multi-core fiber grating arrays over long distances ranging from meters to kilometers. The process is simple and smooth, and the need for low-cost industrial production can be met. The prepared multi-core fiber grating array can be used for long-distance monitoring of stress and strain in macroscopic areas, filling the application gap of long-distance monitoring of stress and strain in engineering applications without integrity and large-scale. The grating array optical fiber prepared by the method is combined with a beam to increase torque, so as to realize the helical sensitization of the multi-core fiber grating in the process of optical fiber combining. In practical applications, the influence of torque in the deformation process can be monitored, the torsion error can be eliminated, the shape sensing accuracy can be improved, and the degree of helical sensitization can be controlled, the torque can be controlled, and multi-dimensional shape sensing with fast positioning and high precision can be realized. The method for preparing a chiral multi-core fiber grating array can flexibly configure the number and spacing of gratings according to actual conditions, so as to complete shape monitoring with more flexible sensing distances and more diverse shape change spans.

[0006] The present invention proposes a method for preparing a chiral multi-core fiber grating array. The preparation method prepares long-distance optical fiber based on a drawing tower. During the drawing process, the fiber grating writing with consistent reflectivity and customized grating spacing is completed, and the fiber core distance is determined. The long-distance grating array optical fiber passes through a rotating fiber delivery module and a beam combining module, and is subjected to torsion under the rotation of the rotating fiber delivery module and the beam combining module to form a chiral multi-core fiber grating array. The spiral torque of the chiral multi-core fiber grating array can be controlled by the rotation speed of the rotating fiber delivery module and the beam combining module. The chiral multi-core fiber grating array prepared according to the method has low preparation cost, meets industrial production conditions, and can achieve the purpose of large-scale long-distance preparation of multi-core fiber grating arrays. The fiber gratings on each fiber core have high consistency, consistent central wavelength, the same reflectivity, and high quality of the multi-core fiber grating array. When monitoring complex strain conditions, strain monitoring of torsion can be achieved. Summary of the invention

[0007] The present invention provides a method for preparing a multi-core fiber grating array, which solves the problems that the general multi-core fiber grating preparation cost is high, takes a long time, cannot realize industrial production and long-distance large-range strain monitoring, and cannot distinguish whether the structural deformation is caused by torque. The preparation process is simple, the preparation steps are concise, the preparation cost is low, and industrial production can be realized. In practical applications, it can fill the gap in engineering monitoring. The chiral multi-core fiber grating array preparation method provided by the present invention can not only enrich the types of monitored stress and strain in structural monitoring applications, but also realize large-scale long-distance monitoring and rapid positioning of complex torsional strain conditions, and has significant advantages in large-scale engineering structure health monitoring.

[0008] The object of the present invention is achieved in that:

[0009] A method for preparing a chiral multi-core fiber grating array is disclosed, which requires selecting a set of rotating fiber feeding modules (1), 1+N grating array optical fibers (2), a beam combining module (3), a coating cup (4), and a fiber collecting device (5).

[0010] The purpose of the rotating fiber delivery module is to complete the fiber delivery of multiple optical fiber gratings, and it has the ability to rotate automatically. The grating array optical fiber is prepared by a drawing tower, and the grating inscription is completed during the preparation process. The grating spacing and the outer diameter of the optical fiber are adjusted during the preparation of the grating array optical fiber by the drawing tower. The outer diameter of the optical fiber is the core distance of the multi-core optical fiber; the beam combining module rotates together with the rotating fiber delivery module, driving the grating array optical fiber to combine in a chiral manner; the coating cup has a certain length to ensure that the chiral grating array multi-core optical fiber is fully cured; finally, the chiral multi-core optical fiber grating array is arranged on a fiber collection disk to reasonably protect the prepared chiral grating array multi-core optical fiber.

[0011] The beam combining module is formed by a large diameter hole and N small diameter holes around it, wherein the central grating array optical fiber is sent out from the large diameter hole located at the center of the beam combining module, and the N grating array optical fibers are sent out from the small diameter holes; when preparing a chiral multi-core fiber grating array, 1+N grating array optical fibers are inserted into the beam combining module at the same speed from the rotating fiber feeding module, and are subjected to torsion under the rotation of the rotating fiber feeding module to be combined into a single multi-core fiber grating array, and the internal structure of this single multi-core fiber grating array is a chiral multi-core fiber grating array formed by 1+N grating array optical fibers spirally.

[0012] 1+N grating array optical fibers are sent out from the rotating fiber delivery module and then passed into the beam combining module. The small holes correspond to the optical fibers one by one. The 1+N grating array optical fibers passing through the beam combining module are sent into the coating cup. The coating cup is fixed in position and does not rotate. The coating cup has a certain length to ensure that the chiral grating array multi-core optical fiber is fully cured.

[0013] 1+N grating array optical fiber disks are placed on the rotating fiber delivery module, and the rotating fiber delivery module automatically rotates and delivers the fiber. The rotating fiber delivery module drives the beam combining module to rotate together, and the coating cup is fixed in position. The 1+N grating array optical fibers passing through the beam combining module are combined in a spiral state around the central fiber grating due to the rotational torque to form a single multi-core fiber grating. The spiral sensitization effect of determining the torque can be achieved by controlling the rotation speed. According to different rotation speeds, the range and sensitivity of the torsional strain of the chiral multi-core fiber grating monitoring structure system can be determined.

[0014] The rotating fiber delivery module and the beam combining module rotate at the same speed and in the same direction, so that 1+N grating array optical fibers are subjected to torsion in the same direction to form a chiral multi-core fiber grating, which is then coated and solidified in the coating cup.

[0015] The coated and cured chiral multi-core fiber grating array is collected into a fiber collection disk through a fiber collection device.

[0016] The fiber collection device is driven by two large rollers and a small roller, which is finally connected to a fiber collection disk; the chiral multi-core fiber grating array coated and cured is collected into the fiber collection disk through the fiber collection device.

[0017] The device adopted by the present invention to solve the technical problem is:

[0018] The invention is characterized in that it is composed of a rotating fiber delivery module (1), a grating array optical fiber (2), a beam combining module (3), a coating cup (4), and a fiber collection device (5); the beam combining module (3) is composed of a large diameter hole surrounded by N small diameter holes; 1+N grating array optical fibers (2) are delivered from the rotating fiber delivery module (1), penetrate into the beam combining module (3), and then flow into the coating cup (4); the rotating fiber delivery module (1) and the beam combining module (3) rotate at the same speed and in the same direction, so that the 1+N grating array optical fibers (2) are subjected to torsion in the same direction to form a chiral multi-core optical fiber grating, and are coated and solidified in the coating cup (4), and finally collected by the fiber collection device (5) to a fiber collection disk.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention proposes a method for preparing a chiral multi-core fiber grating array. The present invention selects a grating array fiber prepared by a drawing tower, completes point grating in the process of preparing the fiber by the drawing tower, and performs a beam combining operation with increased torque on the grating array fiber prepared by the method, thereby realizing the preparation of a multi-core fiber grating array with flexible configuration of grating quantity and spacing. The process is simple and smooth. The multi-core fiber grating array preparation method is used to replace the multi-core fiber grating array preparation method of engraving gratings on the existing multi-core fiber. There is no need to position the grating point by point on the fiber core, and there is no need for complex fiber fan-in and fan-out devices, etc., which greatly reduces the preparation cost of the multi-core fiber grating array, ensures grating consistency and writing efficiency, and realizes low-cost industrial production needs, meeting industrial preparation conditions.

[0021] (2) The present invention selects 1+N grating array optical fibers as the multiple cores of the multi-core optical fiber, and can select a certain core spacing and grating spacing in the core according to different application requirements. It is flexible in application and can not only prepare multi-core fiber grating arrays with small core spacing for shape sensing of tiny devices, such as medical endoscopes, robot arms, etc., but also prepare multi-core fiber grating arrays with large core spacing to achieve large-scale and long-distance deformation monitoring. It has significant advantages in the field of large-scale strain monitoring of engineering structures, roads and bridges, such as geological subsidence, bridge collapse, pipeline sinking, etc., and can achieve high-sensitivity and high-accuracy long-distance deformation measurement.

[0022] (3) The rotating fiber delivery device and beam combining device selected by the present invention can complete the fiber delivery work in an orderly manner. At the same time, due to its own rotation, it can perform spiral sensitivity enhancement for the multi-core fiber grating array. During the sensitivity enhancement process, the rotation torque of the multi-core optical fiber can be controlled by controlling the rotation speed, thereby realizing the measurement of torque during the deformation process, eliminating torsional errors, improving shape sensing accuracy, and realizing multi-dimensional shape sensing with fast positioning, wide range, and high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall device structure of the present invention.

[0024] Figure 2 It is a schematic diagram of a chiral multi-core fiber grating array of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings.

[0026] See attached Figure 1 The present invention discloses a chiral multi-core fiber grating array and a preparation method thereof, comprising a rotating fiber delivery module (1), 1+N grating array optical fibers (2), a beam combining module (3), a coating cup (4), and a fiber receiving device (5); wherein the beam combining module (3) is composed of a large diameter hole surrounded by N small diameter holes; the rotating fiber delivery device (1) serves as a fiber delivery positioning device and rotates automatically, and the beam combining module (3) completes the chiral grating array optical fiber beam combining work and rotates at the same speed as the rotating fiber delivery device (1), and forms a chiral multi-core fiber grating array during the rotation process.

[0027] See attached Figure 2 , is a schematic diagram of a chiral multi-core fiber grating array involved in the present invention, 1+N grating array fibers, taking N as 4 as an example, are a chiral multi-core fiber grating array formed by 4 grating array fibers surrounding 1 central grating array fiber, 1 grating array fiber is located at the central core, and 4 grating array fibers are coiled around the central core in a chiral spiral to form a chiral multi-core fiber grating array (6).

[0028] The working mode of the present invention is as follows: the rotating fiber delivery module (1) delivers 1+N grating array optical fibers (2) at the same speed, and then passes through the beam combining module (3) in a one-to-one correspondence with the small holes. The beam combining module (3) is formed by a large diameter hole and N small diameter holes around it, wherein the central fiber grating is delivered from the large diameter hole, and the N grating array optical fibers are delivered from the small diameter holes. When preparing the chiral multi-core fiber grating array, the 1+N grating array optical fibers (2) are subjected to torsion under the rotation of the rotating fiber delivery module (1) and are bundled into a single multi-core fiber grating array. The internal structure of this single multi-core fiber grating array is a chiral multi-core fiber grating array formed by the spiral of 1+N grating array optical fibers (2). The chiral multi-core fiber grating array is delivered into the coating cup (4) to complete coating and curing, and finally is collected into the fiber collecting disk through the fiber collecting device (5).

[0029] The present invention relates to a method for preparing a chiral multi-core fiber grating array. A grating array optical fiber prepared by a drawing tower is selected, and fixed-point grating is completed in the process of preparing the optical fiber by the drawing tower. The method for preparing the multi-core fiber grating array replaces the multi-core fiber grating array preparation method of grating on an existing multi-core optical fiber. There is no need to position the grating point by point on the core, and the loss caused by the coupling between the single-mode optical fiber and the multi-core optical fiber is avoided. The preparation cost of the multi-core fiber grating array is greatly reduced, and the grating consistency and writing efficiency are ensured while achieving low-cost industrial production needs and meeting industrial preparation conditions.

[0030] The grating array optical fiber (2) selected in the present invention can be selected according to different application requirements, and has suitable optical fiber outer diameter, grating spacing, reflectivity intensity and other indicators. When the grating array optical fiber (2) is inserted into the rotating fiber delivery module (1) and the beam combining module (3), the grating array optical fiber (2) corresponds to the hole one by one, ensuring that the position of each core of the multi-core optical fiber grating is fixed and known, and the core spacing of the multi-core optical fiber grating can be freely adjusted, which can not only realize the monitoring and recovery of small deformation, but also fill the gap of deformation monitoring of large bending radius, large range and long distance structure. The rotating fiber delivery module (1) and the beam combining module (3) rotate at the same speed and in the same direction, so that 1+N grating array optical fibers form a chiral multi-core optical fiber grating array under the action of torque. The chiral multi-core optical fiber grating array can monitor the influence of torque on deformation during the process of monitoring stress and strain due to its special structure. At the same time, the control of the rotation speed can realize the control of the torque of the chiral multi-core optical fiber grating array, thereby realizing the range and sensitivity control of torque monitoring, and the application is flexible and wide.

[0031] In a specific embodiment of the present invention, the five grating array optical fibers delivered by the rotating fiber delivery module at a speed of 50 m / min are made of conventional common single-mode optical fibers (G625) to form a Figure 2A chiral multi-core fiber grating array is shown. The core diameter of the conventional single-mode optical fiber used for preparation is 8.2μm, and the cladding diameter is 125μm. The corresponding central wavelengths of each grating array are λ1, λ2, λ3, λ4, and λ5, respectively, and the corresponding values ​​are 1530nm, 1535nm, 1540nm, 1545nm, and 1550nm. The bandwidth of each wavelength is 0.15nm, the reflectivity is 0.1%, and the interval between the fiber gratings is 2m. The power of the rotating fiber delivery module is 500w, and the rotation speed is 30r / min. According to the formula torque = 9550*power / speed (torque unit is Nm, power unit is kw, and speed unit is r / min), the torque is 159N.m. When preparing the chiral multi-core fiber grating array, the central fiber among the five optical fibers is used as the central core to always maintain vertical fiber delivery, and the other four optical fibers are subjected to torsion around the central core under the rotation of the rotating fiber delivery module to form a single multi-core fiber grating array. The coating cup length is 15cm, and the fiber diameter of the chiral multi-core fiber grating array formed after coating and curing by the coating cup is 3mm, and the total length is 1km. The chiral fiber grating array preparation method proposed by the present invention can effectively realize long-distance industrial production at the meter level or even the kilometer level, with low cost and simple system; the inner and outer diameter cores have a large difference in wavelength change when deformed, and compared with traditional multi-cores, it is more suitable for large-span and long-distance deformation monitoring; the chiral characteristics of the fiber grating array can realize the monitoring of torsion in complex strain conditions.

[0032] The basic principles and main features of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, which all fall within the scope of the present invention to be protected.

Claims

1. A chiral multi-core fiber grating array and a preparation method thereof, characterized in that: It includes a rotating fiber feeding module, 1+N grating array optical fibers, a beam combining module, a coating cup, and a fiber receiving device, wherein: The rotating fiber feeding module is characterized in that it can simultaneously complete the fiber feeding work of multiple grating array optical fibers, and at the same time control the fiber feeding speed to be reasonable and consistent, and can rotate in the horizontal direction along the longitudinal axis to realize the preparation of a chiral multi-core fiber grating array; The 1+N grating array optical fiber is characterized by being a single-mode optical fiber that prepares the grating array online based on a drawing tower, and can select grating arrays of different wavelengths, different spacings, different reflectivities, etc. according to different needs; The beam combining module is characterized in that it can complete the beam combining of multiple grating array optical fibers, rotates at the same speed and in the same direction as the rotating fiber feeding module during the preparation process of the chiral multi-core fiber grating array, and the central grating array optical fiber always maintains a vertical fiber feeding state during the beam combining process. During the beam combining process, N grating array optical fibers are subjected to torsion around the central grating array optical fiber under the rotation of the beam combining module to complete helical sensitization, thereby realizing the preparation of the chiral multi-core fiber grating array; The coating cup is characterized in that it is fixed during the preparation process of the chiral multi-core fiber grating array and does not rotate with the rotating fiber feeding module and the beam combining module. The coating cup can fully ensure the coating work of the chiral multi-core fiber grating array and ensure the mechanical integrity of the optical fiber; The fiber collection device is characterized in that the chiral multi-core fiber grating array is wound neatly and orderly on a fiber collection disk to complete the preparation of the chiral multi-core fiber grating array.

2. The device required for the chiral multi-core fiber grating array and the preparation method according to claim 1, characterized in that: It includes a rotating fiber feeding module, 1+N grating array optical fibers, a beam combining module, a coating cup, and a fiber receiving device, wherein: The rotating fiber feeding module is in the shape of a disk as a whole, placed horizontally, and has a plurality of hanging rings on its lower surface for carrying the grating array optical fiber disk, and completing the fiber feeding work during the preparation process of the chiral multi-core optical fiber grating array; The 1+N grating array optical fibers correspond to the grating array optical fiber disk carried by the rotating fiber feeding module, and grating arrays with different coating thicknesses, different wavelengths, different grating spacings and numbers can be selected for the preparation of the chiral multi-core optical fiber grating array; The beam combining module includes a large diameter hole and N small diameter holes. The large diameter hole is located at the center of the beam combining module, and the N small diameter holes are evenly distributed around the large diameter hole. The central grating array optical fiber passes through the large diameter hole and always maintains a vertical state at the center position. N grating array optical fibers pass through the N small diameter holes and enter the coating cup together after beam combining. The coating cup is cylindrical, including coating glue and ultraviolet curing lamp, the diameter of the circular hole can ensure that the chiral multi-core fiber grating array and the coating glue pass through together, and the length of the coating cup can ensure that the chiral multi-core fiber grating array is fully coated and cured; The fiber collection device comprises two large rollers, a small roller and a fiber collection tray, and the chiral multi-core fiber grating array is connected to the small roller via the two large rollers and finally collected in the fiber collection tray; The rotating fiber feeding module, 1+N grating array optical fibers, beam combining module, and coating cup involved in the chiral multi-core fiber grating array preparation device are arranged in sequence in the vertical direction.

3. A chiral multi-core fiber grating array prepared by the method according to claim 1, characterized in that: A chiral multi-core fiber grating array, wherein the multiple cores are multiple grating array optical fibers, the grating array fiber grating wavelength, grating spacing, and grating reflectivity are the same or different, the core diameters of the cores are the same or different, the number of cores is 1+N, 1 is the central core, located in the central vertical position in the chiral multi-core fiber grating array, N is N side cores uniformly distributed around the central core, located around the central core in a spirally coiled manner, the 1+N cores form a chiral multi-core fiber grating array in a chiral manner, the spiral pitch of the chiral multi-core fiber grating array can be freely adjusted, and the appropriate spiral degree and pitch can be selected according to different strain monitoring, torque monitoring, shape sensing, etc.

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