High-sensitivity impact-resistant optical fiber and preparation method thereof

Abstract

The invention relates to the technical field of optical fiber manufacturing, in particular to a high-sensitivity impact-resistant optical fiber and a preparation method thereof, and the high-sensitivity impact-resistant optical fiber comprises an optical fiber and a shear thickening material layer; and the shear thickening material layer is wrapped outside the optical fiber. And the shear thickening material layer is formed by coating shear thickening liquid and shear hardening glue. According to the optical fiber, the shear thickening material is coated outside the coating layer, so that the impact resistance of the optical fiber is improved, and high sensitivity is kept.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber manufacturing, and in particular relates to a high-sensitivity impact-resistant optical fiber and a preparation method thereof. Background Art

[0002] Distributed fiber optic sensor (DFOS) is an advanced technology that uses optical fiber as a sensing medium and can monitor the changes of physical quantities over the entire length of the optical fiber in real time. Unlike traditional point sensors, distributed fiber optic sensors obtain data such as temperature, strain and vibration along the optical fiber path by detecting the scattering phenomenon of light in the optical fiber (such as Rayleigh scattering, Brillouin scattering and Raman scattering). By emitting light pulses and receiving echo signals transmitted along the optical fiber, analyzing their time delay or frequency changes, continuous distributed measurement of external parameters along the optical fiber can be achieved, and the physical state of each section of the optical fiber can be accurately detected in real time, and even continuous monitoring can be performed on optical fibers tens of kilometers long. DOFS not only has unique advantages in spatial distribution and high sensitivity, but also can effectively avoid electromagnetic interference. In addition, it also has the characteristics of extremely high measurement point density, controllable spacing, small mass, corrosion resistance, electrical insulation, high accuracy, and good repeatability. With the rapid development of distributed fiber optic sensing technology, it has shown broad application prospects in high resolution, long-distance monitoring, multi-functional integration and intelligent analysis.

[0003] DOFS has significant advantages in stress-strain, vibration and acoustic wave measurement, and can achieve high-resolution, long-distance real-time monitoring, which is particularly suitable for health monitoring of facilities such as tunnels and power systems. In addition, DOFS is also widely used in oil and gas exploration, transportation pipeline monitoring, aerospace equipment monitoring and perimeter security.

[0004] However, there is a certain contradiction between improving the impact resistance of DOFS and maintaining its high sensitivity. Generally, in order to improve the impact resistance of DOFS, improvements can be made in a variety of ways. First, in order to increase the impact resistance of the optical fiber, a layer of reinforced sheath material (such as metal sheath, reinforced polymer, etc.) can be added to the outer layer of the optical fiber. This sheath layer can effectively reduce the direct effect of external impact force on the optical fiber body and prevent the optical fiber from being broken or damaged due to external impact or extrusion. Secondly, the special shockproof coating can slow down the energy transmitted to the optical fiber by external vibration or impact, thereby reducing damage to the optical fiber. Some distributed optical fiber sensors use double cladding or multi-layer protection structure to enhance their impact resistance. In addition, thick materials with strong impact resistance (such as rubber, Teflon, etc.) are used on the outer sheath of the optical fiber to provide additional protection to prevent damage to the optical fiber caused by impact and vibration. Through these methods, the durability and stability of the optical fiber in complex environments can be significantly improved. However, high sensitivity requires that the optical fiber can detect small vibration changes. Excessive optical fiber protection may cause its response to vibration to become sluggish, reducing the measurement accuracy. Therefore, it is urgent to solve. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a highly sensitive impact-resistant optical fiber and a preparation method thereof. The optical fiber improves its own impact resistance and maintains its high sensitivity by coating a shear thickening material on the outside of its coating layer.

[0006] To achieve the above object, the technical solution of the present invention is implemented as follows: a highly sensitive impact-resistant optical fiber and a preparation method thereof, comprising: an optical fiber and a shear thickening material layer; the shear thickening material layer is wrapped around the outside of the optical fiber.

[0007] Furthermore, the shear thickening material layer includes a shear thickening liquid and / or a shear hardening glue.

[0008] Furthermore, the optical fiber includes a core, a cladding and a coating; the core is used for optical signal transmission and is made of high-purity glass or plastic; the cladding is wrapped around the outside of the core and is made of a glass material with a lower refractive index than the core; the coating is wrapped around the outside of the cladding and is made of a plastic material.

[0009] Furthermore, the preparation method comprises the following steps:

[0010] 1) Dip the optical fiber in the STF solution and dry the dipped optical fiber in a vacuum drying oven;

[0011] 2) Dipping the dried optical fiber in the SSG solution and drying the dipped optical fiber in a vacuum drying oven;

[0012] 3) Repeating the process of step 1) and step 2) to achieve alternating coating and form a shear thickening material layer, thereby obtaining a highly sensitive impact-resistant optical fiber.

[0013] In specific applications, steps 1) and 2) are repeated 6 times. After six coatings, the diameter of the optical fiber coated with STF and SSG increases by 38.433 μm compared with the original optical fiber. Cyclic coating 6 times can make the optical fiber not only have higher sensitivity but also have certain impact resistance.

[0014] Furthermore, the immersion time of the optical fiber in the STF solution and in the SSG solution are both 3 minutes; the drying temperature of the vacuum drying oven is 60° C., and the drying time is 3 minutes.

[0015] Further, the preparation steps of the STF solution in step 1) are:

[0016] 11) 65% silica particles (6.5 g) and 35% PEG200 (3.5 g) polyethylene glycol 200 were placed in a container, and the container was placed in a ball mill to obtain a preliminary STF solution after ball milling for 24 hours;

[0017] 12) Dilute the preliminary STF solution:

[0018] Add 2 volumes of anhydrous ethanol to the preliminary STF solution and place it in a ball mill for 20 minutes;

[0019] Then use a pipette to transfer the liquid to a 500 ml beaker and record the total volume V. Add 2 V of anhydrous ethanol to dilute it, and ultrasonicate for 30 minutes to obtain the STF solution for optical fiber immersion.

[0020] Further, the preparation steps of the SSG solution in step 2) are:

[0021] 21) Add 5 g of boric acid to 150 g of dimethylhydroxy silicone oil and mix well, react at 180-200° C., and add 375 μL of n-octanoic acid for catalytic reaction; and keep stirring during the catalytic reaction to allow the materials to react fully until a shear-hardening glue is formed;

[0022] 22) SSG and ethanol in a mass ratio of 1:1 are mixed evenly to form an SSG solution for optical fiber impregnation.

[0023] Furthermore, the mass ratio of the boric acid to the dimethylhydroxysilicone oil is 1:30.

[0024] Furthermore, the amount of octanoic acid added is 2.5 μL of octanoic acid added to 1 g of dimethylhydroxysilicone oil.

[0025] The beneficial effects of the present invention are embodied in:

[0026] (1) The present invention coats STF and SSG on the optical fiber, thereby improving the impact resistance of the optical fiber and maintaining its high sensitivity.

[0027] (2) The method provided by the present invention coats STF and SSG on the optical fiber, thereby solving the problem that coating only STF and coating STF multiple times will cause the STF on the optical fiber after drying to fall off in the form of powder. By coating STF and SSG, the entire shear thickening material layer is stable and will not fall off.

[0028] (3) The method of coating STF and SSG on optical fiber in the present invention provides a new solution to the problem that optical fiber requires both high sensitivity and certain impact resistance under certain circumstances. When the optical fiber is not subjected to external force, the elastic modulus of the optical fiber coating is low and does not affect the sensitivity of the optical fiber; when the optical fiber is subjected to external force, the elastic modulus of the optical fiber coating increases, playing a role in protecting the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a cross-sectional view of the structure of the highly sensitive and impact-resistant optical fiber of the present invention;

[0030] Figure 2 A flow chart of the method provided by the present invention;

[0031] Figure 3 It is a schematic diagram of the drop hammer tester for high-sensitivity impact-resistant optical fiber of the present invention.

[0032] Reference numerals and descriptions:

[0033] 1. Fiber core; 2. Cladding; 3. Coating layer; 4. Shear thickening material layer. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] like Figure 1-3 As shown:

[0036] Example 1

[0037] A highly sensitive impact-resistant optical fiber and a preparation method thereof;

[0038] like Figure 2As shown in the optical fiber coating process diagram, after the STF solution and the SSG solution are prepared, the common optical fiber is first immersed in the STF solution for 3 minutes, and the immersed optical fiber is dried in a vacuum drying oven; then the dried optical fiber is immersed in the SSG solution for 3 minutes, and the immersed optical fiber is dried in a vacuum drying oven. The above process is repeated at least 6 times until a shear thickening material layer 4 is formed on the outside of the common optical fiber, thereby obtaining a highly sensitive and impact-resistant optical fiber.

[0039] Example 2

[0040] The detection sensitivity experiment of the high-sensitivity impact-resistant optical fiber obtained in Example 1 was carried out

[0041] The sensitivity of the optical fiber determines whether the Φ-OTDR can detect its weak signal changes. High sensitivity enables the system to detect very small changes in the optical fiber (such as temperature fluctuations, pressure changes, etc.), or even weak mechanical vibrations. In order to compare the sensitivity of optical fibers coated with STF and SSG with uncoated optical fibers, a Φ-OTDR system based on Mach-Zehnder interferometer was built.

[0042] In the specific operation, three different optical fibers are fixed on the piezoelectric ceramic. Using the above experimental device, the sensitivity of the optical fiber coated with STF and SSG, i.e. the high-sensitivity impact-resistant optical fiber obtained in Example 1, the optical fiber not coated with STF and SSG, and the jumper are tested.

[0043] The results show that the sensitivity of the fiber coated with STF and SSG is 177.1% of that of the uncoated fiber and 255.9% of that of the patch cord. The collected signal is processed by a 3×3 coupler demodulation algorithm, which is widely used in distributed fiber sensor systems to extract physical quantity information by utilizing the interference of the fiber coupler and the mode conversion of the optical signal. It can also be concluded from the demodulation results that the sensitivity of the fiber coated with STF and SSG is greatly improved.

[0044] Example 3

[0045] The impact resistance test of the high-sensitivity impact-resistant optical fiber obtained in Example 1

[0046] like Figure 3 As shown, in order to test the protection and impact resistance of optical fibers coated with STF and SSG, a drop hammer tester equipped with a force sensor is used for protection testing. In actual operation, the high-sensitivity impact-resistant optical fiber obtained in Example 1 is used as a sample, and the mass of the hammer head of the drop hammer is set to 0.3 kg. The impact hammer head acts on the sample in the form of free fall under the guidance of the guide rail. The sample is fixed on the force sensor by bonding, and then the force sensor is installed on the metal substrate. The electrical signal of the force sensor is collected by the charge amplifier to perform relevant test analysis.

[0047] The drop height of the hammer head ranges from 0 to 3 cm. After multiple drop hammer experiments, the force on the optical fiber coated with STF and SSG is increased by 40.63% compared with the uncoated optical fiber.

[0048] As can be seen from the above, the sensitivity of optical fiber is closely related to its physical parameters, including the geometric structure and material properties of the optical fiber. The optical fiber coating has a great influence on the performance of the optical fiber. Usually, the optical fiber coating has two layers, the inner coating is softer, and has a low elastic modulus (1.00MPa), which acts as a buffer layer to improve the bending resistance of the optical fiber. The outer coating is harder, has a high elastic modulus (600MPa), and is wear-resistant. It serves as a protective layer to enhance the mechanical properties of the optical fiber. The elastic modulus of the shear thickening material introduced in the present invention increases with the increase of the shear rate. Generally speaking, at lower shear rates, the elastic modulus is relatively small; at higher shear rates, the elastic modulus may increase by several orders of magnitude.

[0049] The method of coating STF and SSG on optical fiber in the present invention provides a new solution to the problem that optical fiber needs both high sensitivity and certain impact resistance under certain circumstances. When the optical fiber is not subjected to external force, the elastic modulus of the optical fiber coating is low and does not affect the sensitivity of the optical fiber; when the optical fiber is subjected to external force, the elastic modulus of the optical fiber coating increases, playing a role in protecting the optical fiber.

[0050] The present invention coats STF and SSG on optical fiber, and tests the sensitivity and impact resistance of coated optical fiber and uncoated optical fiber respectively by using a built Φ-OTDR system and a drop hammer tester. The experimental results show that the diameter of the optical fiber coated with STF and SSG increases by 38.433 μm compared with the uncoated optical fiber, and the sensitivity and impact resistance are significantly improved. Therefore, the present invention has certain practicality and has certain development prospects in the actual field of optical fiber monitoring.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A highly sensitive and impact-resistant optical fiber, characterized in that: include: Optical fiber and a shear thickening material layer (4); the shear thickening material layer (4) is wrapped around the outside of the optical fiber.

2. A highly sensitive impact-resistant optical fiber according to claim 1, characterized in that: The shear thickening material layer (4) comprises a shear thickening liquid and / or a shear hardening glue.

3. A highly sensitive impact-resistant optical fiber according to claim 1, characterized in that: The optical fiber comprises a core (1), a cladding (2) and a coating (3); the core (1) is used for optical signal transmission and is made of high-purity glass or plastic; the cladding (2) is wrapped around the outside of the core (1) and is made of a glass material with a lower refractive index than the core (1); the coating (3) is wrapped around the outside of the cladding (2) and is made of a plastic material.

4. A method for preparing a highly sensitive impact-resistant optical fiber according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: 1) Dip the optical fiber in the STF solution and dry the dipped optical fiber in a vacuum drying oven; 2) Dipping the dried optical fiber in the SSG solution and drying the dipped optical fiber in a vacuum drying oven; 3) Repeating the processes of step 1) and step 2) to achieve alternating coating and form a shear thickening material layer (4) to obtain a highly sensitive impact-resistant optical fiber.

5. The method for preparing a highly sensitive impact-resistant optical fiber according to claim 4, characterized in that: The immersion time of the optical fiber in the STF solution and in the SSG solution were both 3 minutes; the drying temperature of the vacuum drying oven was 60° C., and the drying time was 3 minutes.

6. The method for preparing a highly sensitive impact-resistant optical fiber according to claim 4, characterized in that: The preparation steps of the STF solution in step 1) are: 11) Put 65% by mass of silica particles and 35% by mass of PEG200 into a container, put the container into a ball mill and mill for 24 hours to obtain a preliminary STF solution; 12) Dilute the preliminary STF solution: Add 2 volumes of anhydrous ethanol to the preliminary STF solution and place it in a ball mill for 20 minutes; Then use a pipette to transfer the liquid to a 500 ml beaker and record the total volume V. Add 2 V of anhydrous ethanol to dilute it, and ultrasonicate for 30 minutes to obtain the STF solution for optical fiber immersion.

7. The method for preparing a highly sensitive impact-resistant optical fiber according to claim 4, characterized in that: The preparation steps of the SSG solution in step 2) are: 21) Add boric acid to dimethylhydroxy silicone oil and mix well, react at 180-200° C. and add octanoic acid for catalytic reaction; and keep stirring during the catalytic reaction to allow the materials to react fully until a shear-hardening glue is formed; 22) SSG and ethanol are mixed evenly in a mass ratio of 1:1 to form an SSG solution for optical fiber impregnation.

8. The method for preparing a highly sensitive impact-resistant optical fiber according to claim 7, characterized in that: The mass ratio of the boric acid to the dimethyl hydroxy silicone oil is 1:

30.

9. The method for preparing a highly sensitive impact-resistant optical fiber according to claim 7, characterized in that: The amount of n-octanoic acid added is 2.5 μL of n-octanoic acid added to 1 g of dimethylhydroxysilicone oil.

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