Preparation method of polarization maintaining optical fiber preform and product

Abstract

The invention belongs to the related field of optical communication transmission technology, and discloses a preparation method of a polarization maintaining optical fiber preform, which comprises the following process steps of: firstly, respectively preparing components including a core rod, a stress rod and a sleeve according to performance design requirements of polarization maintaining optical fibers; the sleeve and a center hole of the sleeve are machined for the first time, and the difference between the inner diameter of the sleeve and the outer diameter of the core rod is controlled to meet the preset specification; secondly, secondary machining is conducted on the casing pipe, and positioning and drilling are conducted so that a plurality of stress holes can be independently formed in the casing pipe in the axial direction; and finally, the core rod is assembled into the middle hole of the sleeve, and the stress rods are assembled into the stress holes of the sleeve. The invention also discloses a corresponding polarization maintaining optical fiber preform and an optical fiber product. According to the invention, the core rod can be prevented from being influenced by internal stress generated during drilling vibration, the technical problem that various polarization maintaining optical fiber preforms are easy to crack is effectively solved, and the quality controllability and the production efficiency are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field related to optical communication transmission technology, and more specifically, relates to a method for preparing a polarization-maintaining fiber preform and a product thereof. Background Art

[0002] As a special type of optical fiber, polarization-maintaining fiber is widely used in fields such as fiber optic gyroscopes, optical communication, optical sensing, and geometric optical measurement due to its excellent polarization effect. Currently, the basic technological process for producing polarization-maintaining fiber mainly includes steps such as core rod preparation, mother rod and boron rod preparation, boron rod grinding and mother rod drilling, preform assembly, wire drawing, and testing.

[0003] In order to ensure that the polarization-maintaining fiber has excellent polarization states and other excellent optical properties, in actual production, it is often necessary to process it into a highly doped or special-structured high-stress polarization fiber. Therefore, during the preparation process of the polarization-maintaining fiber preform, mechanical processing operations such as conventional drilling are involved. However, these operations can easily cause cracks in the core rod due to vibration or internal stress effects. In the lightest case, cracks are generated, and in the worst case, the rod body breaks, which is also the main reason for the large difficulty in the preparation process of polarization-maintaining fiber, low yield, and even difficulty in production.

[0004] To solve the above technical problems, currently, the main methods adopted in the industry are annealing processes or by increasing the distance between the stress area and the core rod, etc., to reduce the internal stress effects generated during stress or vibration to a certain extent. However, it has been found in actual production that even if a large amount of time is spent on annealing treatment or increasing the distance between the stress area and the core rod, there is still a great risk of rod cracking during the production process, and at the same time, its polarization-maintaining performance will also deteriorate to a large extent, which is particularly obvious for the processing of highly doped or special-structured rod bodies.

[0005] Through novelty search, Chinese Patent CN118305905A discloses a method of drilling through multiple steps, that is, first using a small drill bit and then successively using larger-sized drill bits for drilling to ensure that the stress is gradually released during each drilling, and to prevent the core rod from cracking to the greatest extent. However, further research shows that the above existing drilling process is relatively cumbersome and requires the axis to be consistent during each drilling, otherwise it will lead to non-circular drilling or failure, resulting in limited effect of preventing the core rod from cracking ultimately. Summary of the Invention

[0006] In view of one or more of the above deficiencies or improvement requirements of the prior art, the present invention provides a method for preparing a polarization-maintaining fiber preform and a product thereof. By redesigning the overall preparation process flow of the preform and adopting the method of positioning and drilling the sleeve and then assembling it, the required preform can be obtained. At the same time, targeted improvements are made in aspects such as the processing control process and parameters of its key process steps. Accordingly, not only can the influence of internal stress generated when the core rod is subjected to drilling vibration be avoided, effectively solving the technical problem of easy cracking of various polarization-maintaining fiber preforms, but also the quality controllability and production efficiency are significantly improved. Therefore, it can be adapted to various application occasions for preparing polarization-maintaining fibers with high doping or special structures, and has good practical value and application prospects.

[0007] To achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a polarization-maintaining fiber preform, which successively includes the following steps:

[0008] Step 1: Preparation of each component

[0009] According to the performance design requirements of the polarization-maintaining fiber, each component including a core rod, a stress rod, and a sleeve is respectively prepared;

[0010] Step 2: First processing of the sleeve

[0011] The sleeve is processed so that the central hole distributed along the axial direction reaches the design size, and the difference between the inner diameter of the sleeve and the outer diameter of the core rod is controlled to meet the preset specifications;

[0012] Step 3: Second processing of the sleeve

[0013] The sleeve is positioned and drilled, and then tapered, so that a plurality of stress holes are independently formed along the axial direction of the sleeve and are parallel to the central hole;

[0014] Step 4: Assembly of each component

[0015] The core rod is assembled into the intermediate hole of the sleeve, and the stress rod is assembled into each stress hole of the sleeve, thereby obtaining the required polarization-maintaining fiber preform.

[0016] As a further preference of the present invention, in Step 1, the core rod and the stress rod are preferably processed to the design size by processing techniques such as stretching, grinding, or etching.

[0017] As a further preference of the present invention, in Step 2, the sleeve is preferably processed by a pre-fusion and shrinkage process so that the central hole shrinks to the design size, and the difference between the inner diameter of the sleeve and the outer diameter of the core rod is controlled between 0.2 mm and 5 mm.

[0018] As a further preference of the present invention, in step three, the operation process of the positioning drilling is preferably designed as follows: First, according to the birefringence or beat length requirements of the polarization maintaining fiber, a stress rod with a refractive index meeting the requirements is selected; then, combining the refractive index and size of the stress rod, the hole pitch and the drilling position of the mother tube are calculated and confirmed; then, the mother tube is directly cut without inserting the core rod and the flatness of its end face is ensured, and at the same time, the mother tube is positioned; finally, positioning drilling is performed on the mother tube according to the positioning.

[0019] As a further preference of the present invention, in step three, the stress holes preferably meet the following performance and dimensional specifications: The stress rod preferably has a stress rod with a refractive index difference from pure silicon of 3×10 -3 ~12×10 -3 and the diameter of the stress rod is preferably 5 mm to 15 mm, and the length of the stress rod is preferably 150 mm to 600 mm.

[0020] As a further preference of the present invention, in step four, before assembly, it preferably includes cleaning and drying the core rod, stress rod and sleeve.

[0021] According to another aspect of the present invention, a corresponding polarization maintaining fiber preform product is also provided.

[0022] According to still another aspect of the present invention, a corresponding polarization maintaining fiber product is also provided.

[0023] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following technical advantages are mainly possessed:

[0024] (1) By re-studying and designing the preparation process flow of the polarization maintaining fiber preform, the present invention adopts the method of performing sub-processing on the sleeve to form different through holes and then assembling different components respectively. In this way, not only can the influence of internal stress generated when the core rod is subjected to vibrations such as drilling be completely avoided, effectively preventing the preform from cracking, but also the quality controllability and production efficiency of the whole process are significantly improved, and various polarization maintaining fiber preforms and fiber products with required performance can be ensured to be obtained;

[0025] (2) The present invention further optimizes the design of the performance index requirements for some key operation steps such as the first processing and the second processing of the sleeve. A large number of actual tests show that it can not only ensure that the core rod is smoothly inserted into the central hole of the sleeve and ensure good concentricity, but also enable the stress rods accommodated in each stress hole to generate stronger birefringence, thereby more effectively eliminating the influence of stress on the polarization state of the incident light;

[0026] (3) The polarization-maintaining optical fiber preform and optical fiber product of the present invention are easy to process, can be manufactured using existing production equipment and materials, have good quality controllability, and greatly reduce the phenomenon of preform cracking, significantly improving the overall quality of the optical fiber product. Therefore, it is particularly suitable for various applications of preparing polarization-maintaining optical fibers with high doping or special structures, and has good practical value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a process flow chart for preparing the polarization-maintaining optical fiber preform according to the present invention;

[0028] Figure 2 is a schematic diagram of the production scenario of the polarization-maintaining optical fiber preform according to a preferred embodiment of the present invention;

[0029] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0030] 1 - mandrel; 2 - stress rod; 3 - sleeve after the first processing; 4 - sleeve after the second processing; 5 - preform. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. 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 invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention.

[0033] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0034] In the present invention, unless otherwise clearly specified or limited, terms such as "installed", "connected", "joined", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the present invention, unless otherwise clearly specified or limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0036] Figure 1 is the process flow chart of the preparation of the polarization maintaining fiber preform according to the present invention, Figure 2 is a schematic diagram of the production scenario of the polarization maintaining fiber preform according to a preferred embodiment of the present invention. Hereinafter, reference will be made to Figure 1 and Figure 2 to more specifically explain and illustrate the present invention.

[0037] As Figure 1 and Figure 2 shown, in the method for preparing the polarization maintaining fiber preform of the present invention, the following steps are sequentially included:

[0038] First, it is the preparation step of each component.

[0039] In this step, according to the performance design requirements of the polarization maintaining fiber, each component including the core rod 1, the stress rod 2 and the sleeve is respectively prepared. Specifically, the core rod and the stress rod can be processed to the designed dimensions by means such as stretching, grinding or etching.

[0040] Next, it is the first processing step of the sleeve.

[0041] In this step, the sleeve is processed alone so that the central hole distributed along the axis reaches the designed dimensions, thereby obtaining the sleeve 3 after the first processing, wherein the difference between the inner diameter of the sleeve and the outer diameter of the core rod 1 is controlled to meet the preset specifications.

[0042] More specifically, according to a preferred embodiment of the present invention, the sleeve to be fused and shrunk can be pre-fused and shrunk to the designed size. Among them, it is preferred to control the size difference between the inner diameter of the sleeve and the outer diameter of the mandrel to be between 0.2 mm and 5 mm. This size difference can enable the mandrel to be smoothly inserted into the inner hole of the sleeve and ensure good concentricity.

[0043] Next, it is the secondary processing step of the sleeve.

[0044] In this step, the sleeve 3 after the first processing is continuously and separately positioned and drilled, and then a tapering process is carried out to obtain the sleeve 4 after the secondary processing; wherein, the sleeve independently forms a plurality of stress holes along the axial direction and these stress holes are respectively parallel to the central hole.

[0045] More specifically, according to another preferred embodiment of the present invention, the operation process of the positioning drilling is preferably designed as follows: First, according to the birefringence or beat length requirements of the polarization-maintaining fiber, a stress rod with a refractive index meeting the requirements is selected; then, combining the refractive index and size of the stress rod, the hole spacing and the drilling position of the mother tube are calculated and confirmed; then, the mother tube is directly cut without inserting the mandrel and the flatness of its end face is ensured, and at the same time the mother tube is positioned; finally, the positioning drilling is performed on the mother tube according to the positioning.

[0046] Correspondingly, the stress holes preferably meet the following performance and size specifications: the stress rod preferably has a refractive index difference from the pure silicon ratio of 3×10 -3 ~12×10 -3 and the diameter of the stress rod is preferably 5 mm to 15 mm, and the length of the stress rod is preferably 150 mm to 600 mm.

[0047] Next, it is the assembly step of each component.

[0048] In this step, the mandrel 1, the stress rod 2 and the tapered sleeve are cleaned and dried, and then the mandrel 1 is assembled into the middle hole of the sleeve, and the stress rod 2 is assembled into each of the stress holes parallel to the middle hole on both sides of the sleeve, thereby obtaining the required polarization-maintaining fiber preform.

[0049] Finally, the assembled preform is evacuated and drawn into a fiber to the designed size. The fiber is, for example, a panda-type polarization-maintaining fiber and is particularly suitable for various polarization-maintaining fibers with high doping or special structures.

[0050] In summary, according to the above technical solution of the present invention, by adopting the method of performing separate processing on the sleeve to form different through holes and then assembling different components respectively, not only can the influence of internal stress generated when the mandrel is subjected to vibrations such as drilling be completely avoided, effectively preventing the preform from cracking, but also the quality controllability and production efficiency of the entire process are significantly improved, ensuring that various polarization-maintaining fiber preforms and fiber products with the required performance can be obtained. This process can be manufactured using existing production equipment and materials, greatly reducing the phenomenon of preform cracking and significantly improving the overall quality of fiber products. Therefore, it is particularly suitable for various applications of preparing polarization-maintaining fibers with high doping or special structures and has good practical value and application prospects.

[0051] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a polarization-maintaining optical fiber preform, characterized in that The method sequentially includes the following steps: Step 1: Preparation of each component According to the performance design requirements of the polarization-maintaining optical fiber, each component including the core rod (1), stress rod (2) and sleeve (3) is respectively prepared; Step 2: First processing of the sleeve The sleeve (3) is processed so that the central hole axially distributed therein reaches the design size, and the difference between the inner diameter of the sleeve (3) and the outer diameter of the core rod (1) is controlled to meet the preset specification; Step 3: Second processing of the sleeve The sleeve (3) is positioned and drilled, and then tapered, so that a plurality of stress holes are independently formed in the sleeve (3) along the axial direction and are parallel to the central hole; Step 4: Assembly of each component The core rod (1) is assembled into the central hole of the sleeve (3), and the stress rod (2) is assembled into each stress hole of the sleeve (3), thereby obtaining the required polarization-maintaining optical fiber preform.

2. The preparation method according to claim 1, characterized in that, In Step 1, preferably, the core rod (1) and stress rod (2) are processed to the design size through processing techniques such as stretching, polishing or corrosion.

3. The preparation method according to claim 1 or 2, characterized in that, In Step 2, preferably, the sleeve (3) is processed through a pre-fusion shrinkage process so that the central hole shrinks to the design size, and the difference between the inner diameter of the sleeve (3) and the outer diameter of the core rod (1) is controlled between 0.2 mm and 5 mm.

4. The preparation method according to any one of claims 1 to 3, characterized in that, In Step 3, the operation process of the positioning drilling is preferably designed as follows: First, according to the birefringence or beat length requirements of the polarization-maintaining optical fiber, a stress rod with a refractive index meeting the requirements is selected; then, in combination with the refractive index and size of the stress rod, the hole pitch and the drilling position of the mother tube are calculated and confirmed; then, the mother tube is directly cut without inserting the core rod and the flatness of its end face is ensured, and at the same time, the mother tube is positioned; finally, the positioning drilling is performed on the mother tube according to the positioning.

5. The preparation method according to claim 4, characterized in that, In step three, the stress hole preferably meets the following performance and dimensional specifications: the stress bar preferably has a stress bar with a refractive index difference of 3*10 -3 ~12*10 -3 with the pure silicon, and the diameter of the stress bar is preferably 5 mm to 15 mm, and the length of the stress bar is preferably 150 mm to 600 mm.

6. The preparation method according to any one of claims 1-5, characterized in that, In Step 4, preferably, before assembly, the core rod, stress rod and sleeve are cleaned and dried.

7. A polarization-maintaining optical fiber preform product, characterized in that, It is prepared by using the method according to any one of claims 1-6.

8. A polarization maintaining optical fiber product, characterized in that, Its preform is prepared by using the method according to any one of claims 1-6.

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