Low-loss stress-resistant optical fiber and preparation method and application thereof

Abstract

The invention discloses a low-loss stress-resistant optical fiber and a preparation method and application thereof. The optical fiber comprises a fiber core, an inner cladding, an outer cladding, an outer protection layer and a hydrophobic layer which are sequentially arranged from inside to outside. According to the invention, through the innovation of the optical fiber structure, the stress resistance and the signal fidelity are synchronously improved, especially under the extreme mechanical deformation or temperature and humidity environment, the ultra-low loss is still maintained, and the reliable operation period of the system is greatly prolonged; through cooperation of the FBG and the optical fiber, the system can carry out high-precision decoupling analysis on multiple parameters of the cable, the false alarm rate is reduced by more than 40%, and the fault positioning precision reaches + / -0.5 m; due to the double protection design of the outer protection layer and the hydrophobic layer, the optical fiber can still maintain stable sensing sensitivity in severe scenes such as burying and soaking, collaborative optimization of mechanical performance and optical performance of the optical fiber is achieved, and the low-loss and high-strain-resistance characteristics of the optical fiber provide an ideal sensing carrier for cable safety monitoring. The monitoring system has the characteristics of multi-parameter fusion analysis, remote real-time early warning, strong environmental adaptability and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fibers, and particularly relates to a low-loss stress-resistant optical fiber and a preparation method and application thereof. BACKGROUND

[0002] Optical fiber sensing technology has shown great potential in cable safety monitoring field due to its unique advantages such as intrinsic safety, anti-electromagnetic interference, long-distance monitoring and easy construction of distributed network. By monitoring the changes of parameters such as intensity, phase, wavelength or polarization state of the transmitted optical signal in the optical fiber, the system can real-time perceive the key information of the cable operation state, such as temperature anomaly, mechanical strain, potential failure of partial discharge and the like. This non-intrusive and real-time online monitoring method has become an indispensable nerve ending of modern smart grid. However, the physical performance of the sensing optical fiber itself, which is the basis of the effectiveness of this advanced technology, is facing severe challenges in the current complex and harsh engineering application environment.

[0003] When the existing conventional communication optical fiber is applied in the sensing field, especially in cable monitoring, its inherent vulnerability is exposed. When the optical fiber is laid in the cable body or the surrounding environment, it inevitably bears mechanical stress from installation tension, operation vibration, accidental extrusion or necessary bending (such as joint box, well corner) and the like, which can easily cause significant micro-bending loss or macro-bending loss, resulting in attenuation or even interruption of the transmitted optical signal, and thus causing the sensor sensitivity to drop sharply or fail. More troublesome is that the cable operation environment is usually extremely harsh: high temperature can accelerate the aging of the optical fiber coating layer, change the refractive index of the fiber core, and induce additional loss; the penetration of humid water vapor can cause the well-known "water peak" absorption loss, especially in a specific wavelength window; and the complex strong electromagnetic environment around the transformer substation and high-voltage line, although it does not directly affect the optical transmission itself, can seriously interfere with the photoelectric conversion, signal acquisition and transmission circuit of the sensing system, introduce noise, and reduce the signal-to-noise ratio and measurement accuracy. These factors are coupled with each other, which seriously weakens the reliability and accuracy of the monitoring data.

[0004] In the face of the above challenges, the industry has tried various improvement measures, such as using more tough coating materials or enhancing the bending resistance in the structural design, but the effect is often unsatisfactory. Special materials can improve the resistance to a single environment (such as high temperature), but it is difficult to systematically solve the problem of comprehensive performance degradation under the coupling effect of stress, vibration, humidity, and electromagnetic and other multi-physical fields; in terms of structure, the design of traditional step-index or simple graded-index optical fiber has physical limitations in the sensitivity of optical mode to bending and stress. Therefore, the existing improvement schemes often fall into the dilemma of "treating the headache and treating the foot pain", and cannot provide stable, durable and high-precision sensing ability in the harsh cable monitoring scene.

[0005] The requirements for the safe operation of cables in power systems are increasingly stringent, and early and accurate identification of hidden dangers is a core requirement. The performance short board of existing optical fiber sensors under complex stress and environmental disturbance has become a key bottleneck restricting their deep application and reliability improvement in the field of cable monitoring. Developing a new type of optical fiber that maintains extremely low optical transmission loss when subjected to continuous or sudden mechanical stress (including bending, vibration, and extrusion), while effectively resisting the erosion of high temperature, high humidity, and strong electromagnetic interference, and maintaining high sensing sensitivity, has become an urgent need for the development of optical fiber sensing technology and the intelligent upgrading of power facilities. SUMMARY

[0006] To solve the problems in the prior art, the purpose of the present application is to provide a low-loss stress-resistant optical fiber and its preparation method and application.

[0007] To achieve the above-mentioned purposes and achieve the above-mentioned technical effects, the technical solution adopted by the present application is as follows: A low-loss stress-resistant optical fiber, comprising a core, an inner cladding, an outer cladding, an outer protective layer, and a hydrophobic layer arranged in order from the inside to the outside.

[0008] Further, the core is made of a high-refractive high-purity silica glass matrix uniformly doped with rare earth elements, and the doping concentration is 0.5%-1.5%.

[0009] Further, the rare earth element is an erbium element.

[0010] Further, the outer cladding is coated with polyimide and carbon nanotubes.

[0011] Further, the outer protective layer is a Kevlar fiber reinforced layer with a mechanical strength greater than 500MPa.

[0012] Further, the hydrophobic layer is made of a hydrophobic polymer material, and the hydrophobic polymer material has a polysiloxane backbone and a hydrophobic group as a side group.

[0013] Further, the low-loss stress-resistant optical fiber has a loss of less than 0.02dB / km under 1.5% tensile strain, an operating temperature of -40℃ to +85℃, a 1550nm wavelength loss of less than 0.18dB / km, and a loss of less than 0.1dB at a minimum bending radius of 15mm.

[0014] The present application also discloses a preparation method of a low-loss stress-resistant optical fiber, comprising the following steps: 1) a high-refractive high-purity silica glass matrix uniformly doped with rare earth elements is used to make a core; 2) a fluoride-doped quartz material is used to make an inner cladding outside the core; 3) a composite coating composed of polyimide and carbon nanotubes is coated outside the inner cladding to form an outer cladding after curing. 4) The outer protective layer is formed by using Kevlar fiber reinforced layer outside the outer cladding layer; 5) The hydrophobic layer is formed by coating hydrophobic polymer outside the outer protective layer.

[0015] The application further discloses application of the low-loss stress-resistant optical fiber in a cable safety monitoring system.

[0016] Further, the cable safety monitoring system comprises: The sensor module is constructed by using the low-loss stress-resistant optical fiber as a sensing medium and combining the fiber Bragg grating technology, and is used for sensing strain, temperature and vibration parameters of the cable. The data processing module is used for capturing the optical fiber reflection spectrum in real time and extracting cable state characteristic values. The monitoring platform is used for realizing cloud storage, remote early warning and fault positioning of data.

[0017] Compared with the prior art, the application has the following beneficial effects: The application synchronously improves the stress-resistant performance and signal fidelity by optical fiber structure innovation, especially still maintains ultra-low loss under extreme mechanical deformation or temperature and humidity environment, greatly prolongs the reliable operation period of the monitoring system; in the application level, through cooperation of the FBG and the optical fiber, the system can perform high-precision decoupling analysis on the cable multi-parameters, the false alarm rate is reduced by more than 40%, and the fault positioning accuracy is ±0.5 meters. Meanwhile, the double protection design of the outer protective layer and the hydrophobic layer enables the optical fiber to maintain stable sensing sensitivity in the buried, water immersion and other harsh scenes, realizes cooperative optimization of the mechanical performance and the optical performance of the optical fiber, and provides an ideal sensing carrier for the cable safety monitoring, the monitoring system has the characteristics of multi-parameter fusion analysis, remote real-time early warning and strong environmental adaptability, significantly improves the safety management level of key infrastructures in the power, communication and industrial fields, and has wide application value. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 Fig. 1 is a three-dimensional structural schematic diagram of the low-loss stress-resistant optical fiber of the application; Fig. 2 Fig. 2 is a sectional schematic diagram of the low-loss stress-resistant optical fiber of the application; Fig. 3 Fig. 3 is a flow chart of the application. DETAILED DESCRIPTION

[0019] The application will be described in detail below, so that the advantages and characteristics of the application can be more easily understood by those skilled in the art, and the protection scope of the application can be more clearly and explicitly defined.

[0020] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that will be provided later.

[0021] like Figs. 1-3 As shown, the present invention discloses a low-loss stress-resistant optical fiber 6, which includes a core 1, an inner cladding 2, an outer cladding 3, an outer protective layer 4 and a hydrophobic layer 5 arranged in sequence from the inside to the outside.

[0022] In some embodiments, the fiber core 1 is made of a high-refractive-index, high-purity silica glass matrix uniformly doped with rare earth elements, and high-gain signal transmission and enhanced stability can be achieved by optimizing the doping concentration.

[0023] In some more specific embodiments, the fiber core 1 is made of a high-refractive-index, high-purity silica glass matrix uniformly doped with 0.5%-1.5% (by weight) erbium. The core advantages of erbium doping are primarily reflected in optical amplification and suitability for long-distance communication scenarios.

[0024] In some embodiments, the inner cladding 2 is made of fluorine-doped quartz material. Fluorine doping causes optical anisotropy in the inner cladding 2, causing light to produce different refractive index responses (i.e., birefringence effect) during transmission, thereby suppressing mode coupling loss caused by bending.

[0025] In some embodiments, the outer cladding 3 is coated with polyimide and carbon nanotubes to enhance high temperature resistance and mechanical strength.

[0026] In some embodiments, the outer protective layer 4 is a Kevlar fiber reinforced layer with a mechanical strength greater than 500 MPa, which is used to improve impact resistance and mechanical strength.

[0027] In some embodiments, the hydrophobic layer 5 is made of a hydrophobic polymer material to enhance moisture resistance, block moisture erosion, and ensure stable optical performance in a high humidity environment.

[0028] In some more specific embodiments, the hydrophobic polymer material has polysiloxane as the main chain, and the side groups are hydrophobic groups such as methyl or phenyl.

[0029] The low-loss stress-resistant optical fiber provided by the present invention is manufactured by a drawing-coating integrated technology under a vacuum environment, and the preparation method comprises the following steps: 1) A high-refractive-index, high-purity silica glass matrix is ​​uniformly doped with rare earth elements to form a fiber core 1; 2) The inner cladding 2 is made of fluoride-doped quartz material outside the fiber core 1; 3) The outer cladding 3 is formed by coating a composite coating consisting of polyimide and carbon nanotubes outside the inner cladding 2 and curing; 4) The outer protective layer 4 is formed by a Kevlar fiber reinforced layer outside the outer cladding 3; 5) The hydrophobic layer 5 is formed by coating a hydrophobic polymer outside the outer protective layer 4 and curing; The core of the above preparation method is to optimize the drawing speed and cladding thickness distribution parameters multiple times, control the drawing speed to be 50-100 m / min, and the cladding thickness uniformity error to be less than ±2%, so that the optical fiber forms a uniform stress buffer structure at the micro level, and the stress distribution optimization effect is formed, thereby achieving low loss and high strain resistance characteristics.

[0030] The low-loss stress-resistant optical fiber 6 provided by the application has a loss of less than 0.02 dB / km under 1.5% tensile strain, a working temperature of -40℃ to +85℃, a loss of less than 0.18 dB / km at a wavelength of 1550 nm, and a loss of less than 0.1 dB when the minimum bending radius is 15 mm, and the comprehensive performance is significantly better than that of a conventional optical fiber.

[0031] The low-loss stress-resistant optical fiber provided by the application significantly improves the mechanical stress resistance, environmental interference resistance and signal transmission stability through the innovative five-layer structure design, and solves the problems of high loss and poor reliability of existing optical fibers under complex working conditions.

[0032] The application also discloses an application of the low-loss stress-resistant optical fiber in a cable safety monitoring system.

[0033] In some embodiments, the cable safety monitoring system comprises a sensor module, a data processing module, a monitoring platform and a visualization module. The sensor module uses the low-loss stress-resistant optical fiber 6 as a sensing medium, is constructed in combination with a fiber Bragg grating (FBG) technology, and is used for sensing parameters such as strain, temperature and vibration of the cable. The data processing module is connected with the sensor module, is used for capturing an optical fiber reflection spectrum in real time, and extracts cable state characteristic values through an existing demodulation algorithm. The monitoring platform is connected with the data processing module, adopts a distributed architecture, is used for transmitting the data processed by the data processing module to the cloud, and realizes data cloud storage, remote real-time early warning and fault positioning and diagnosis (accuracy < 50 m). The monitoring platform is internally provided with a fault diagnosis engine. For power cables, the fault diagnosis engine predicts mechanical damage or overload risk by analyzing tensile strain mutation and temperature rise gradient. For submarine communication cables, the fault diagnosis engine identifies anchor damage or water flow impact in combination with vibration spectrum characteristics. For oil and gas pipelines in industrial scenarios, the fault diagnosis engine diagnoses third-party construction damage in association with a temperature-strain coupling change model. All early warning signals are displayed in real time through a visualization module and trigger a grading alarm mechanism of a three-level response of early warning, emergency and fault.

[0034] In some embodiments, the sensor module inscribes gratings with a period of 500-600 nm on the low-loss stress-resistant optical fiber 6 through ultraviolet writing technology, to realize multi-parameter monitoring.

[0035] In some embodiments, the data processing module injects low-loss stress-resistant optical fiber 6 through a high-sensitivity ultra-wideband light source via a coupler, and collects reflected spectra by a fiber spectrometer. The system realizes multi-parameter high-precision decoupling analysis in cooperation with FBG and composite low-loss stress-resistant optical fiber 6, reduces false alarm rate by more than 40%, and achieves fault positioning accuracy of ±0.5 meters.

[0036] In some embodiments, the arrangement of the low-loss stress-resistant optical fiber 6 in the cable includes arranging FBG sensor arrays every 50 meters along the axial direction of the underground cable, or spirally winding in the outer sheath of the submarine cable. The system realizes fault prediction and positioning (accuracy < 50 m) by real-time acquisition of signals by a demodulator and feedback to the monitoring platform in combination with historical data.

[0037] The cable safety monitoring system is suitable for power cables (such as underground power transmission line stress monitoring), communication cables (such as submarine optical cable fiber breakage early warning), industrial facilities (such as oil and gas pipeline safety monitoring), etc., realizes early identification of hidden faults, reduces false alarm rate by more than 40% through multi-parameter fusion analysis, and can optimize the fiber arrangement according to the scene, breaks through the traditional fiber environmental adaptability bottleneck, solves the problem that existing fibers are easily affected by mechanical stress, temperature and humidity environment and electromagnetic interference, resulting in high loss and poor reliability. The cable safety monitoring system constructed by the present application has high reliability and strong environmental tolerance, provides core technical support for the whole life cycle safety management of key infrastructure in the fields of power, communication and industry, and has wide engineering application value.

[0038] Parts or structures not specifically described in the present application can adopt existing technologies or existing products, which are not described here.

[0039] The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which are made by using the content of the present application, are also included in the patent protection scope of the present application.

Claims

1. A low-loss stress-resistant optical fiber, characterized in that: The fiber comprises a fiber core, an inner cladding, an outer cladding, an outer protective layer and a hydrophobic layer which are arranged in sequence from the inside to the outside.

2. The low-loss stress-resistant optical fiber according to claim 1, characterized in that: The fiber core is made of a high-refractive-index, high-purity silica glass matrix uniformly doped with rare earth elements, with a doping concentration of 0.5%-1.5%.

3. The low-loss stress-resistant optical fiber according to claim 2, characterized in that: The rare earth element is erbium.

4. The low-loss stress-resistant optical fiber according to claim 1, characterized in that: The outer cladding is formed by coating polyimide and carbon nanotubes.

5. The low-loss stress-resistant optical fiber according to claim 1, characterized in that: The outer protective layer is a Kevlar fiber reinforced layer with a mechanical strength greater than 500 MPa.

6. The low-loss stress-resistant optical fiber according to claim 1, characterized in that: The hydrophobic layer is made of a hydrophobic polymer material, wherein the hydrophobic polymer material has polysiloxane as the main chain and the side groups are hydrophobic groups.

7. The low-loss stress-resistant optical fiber according to claim 1, characterized in that: The low-loss stress-resistant optical fiber has a loss of less than 0.02dB / km under a tensile strain of 1.5%, an operating temperature of -40°C to +85°C, a loss of less than 0.18dB / km at a wavelength of 1550nm, and a loss of less than 0.1dB at a minimum bending radius of 15mm.

8. The method for preparing a low-loss stress-resistant optical fiber according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) The fiber core is made of a high refractive index and high purity silica glass matrix uniformly doped with rare earth elements; 2) Using fluoride-doped quartz material to make the inner cladding outside the core; 3) coating the outer surface of the inner cladding with a composite coating composed of polyimide and carbon nanotubes and curing the coating to form an outer cladding; 4) A Kevlar fiber reinforcement layer is used outside the outer cladding to form an outer sheath; 5) Coating a hydrophobic polymer on the outside of the outer protective layer and curing it to form a hydrophobic layer.

9. Use of the low-loss stress-resistant optical fiber according to any one of claims 1 to 7 in a cable safety monitoring system.

10. A cable safety monitoring system according to claim 9, characterized in that: include: A sensor module, wherein the sensor module is constructed using a low-loss stress-resistant optical fiber as a sensing medium in combination with fiber Bragg grating technology, and is used to sense strain, temperature, and vibration parameters of the cable; Data processing module, used to capture the optical fiber reflection spectrum in real time and extract the cable status characteristic value; The monitoring platform is used to realize cloud data storage, remote early warning and fault location.

Images