Immersion sensing optical fiber, manufacturing method, immersion detection device and immersion detection system

Abstract

The invention relates to a soaking sensing optical fiber and a manufacturing method thereof, a soaking detection device and a soaking detection system, and the manufacturing method comprises the steps: obtaining a to-be-processed optical fiber, and stripping at least part of a cladding and a coating layer of the optical fiber. And obtaining a solution made of a soaking sensitive material, and uniformly coating the soaking sensitive material solution on the surface of the optical fiber from which part of the cladding and the coating layer are stripped. The coated optical fiber is placed in a high-temperature drying box for thin film curing, through high-temperature drying treatment, the immersion sensitive material forms a layer of stable thin film on the surface of the optical fiber, and therefore the immersion sensing optical fiber is prepared. The sensing optical fiber manufactured by adopting the manufacturing method disclosed by the invention can be applied to accurate monitoring of water immersion conditions in underground pipelines or other application scenes, and has the advantages of high response speed, high accuracy, good stability and the like; the problems that an existing optical fiber humidity sensor is interfered by environment humidity and is prone to false alarm in underground pipeline water immersion detection can be effectively solved.

Description

Technical Field

[0001] The present application relates to the technical field of optical fiber sensing, and particularly to a water-immersion sensing optical fiber and a manufacturing method thereof, a water-immersion detection device, and a water-immersion detection system. Background Art

[0002] With the acceleration of the urbanization process, the complexity and aging problems of the underground pipeline system have become increasingly prominent, and the maintenance of pipelines, especially the detection of water-immersion problems, has become particularly difficult. Traditional underground pipeline detection technologies, such as closed-circuit television detection technology, pipeline rapid inspection detection technology, sonar detection, and ground-penetrating radar, although they can effectively detect the location and layout of pipelines, have obvious deficiencies in water-immersion detection. These technologies often cannot quickly and accurately identify the water-immersion points in pipelines, posing potential hazards to the safe operation of urban infrastructure.

[0003] In recent years, detection technologies based on optical fiber sensing have received extensive attention due to their unique advantages. However, existing optical fiber humidity sensors are too sensitive to humidity changes, resulting in false alarms easily in water-immersion detection and making it difficult to achieve accurate detection. Therefore, it is particularly important to develop an optical fiber sensor suitable for detecting water-immersion in underground pipelines. Summary of the Invention

[0004] Based on this, the purpose of the present application is to provide a water-immersion sensing optical fiber and a manufacturing method thereof, a water-immersion detection device, and a water-immersion detection system, aiming to solve the technical problems that existing optical fiber humidity sensors are too sensitive and prone to false alarms in underground pipeline water-immersion detection.

[0005] An embodiment of the present application provides a water-immersion sensing optical fiber, including a water-immersion sensing part. The water-immersion sensing part sequentially includes a core layer and a cladding layer from the inside to the outside. The cladding layer is obtained by thin-film curing of a water-immersion sensitive material. The water-immersion sensitive material has a water absorption property, and the degree of change in refractive index under water-immersion conditions is greater than the degree of change of the humidity sensitive material in a humidity environment.

[0006] An embodiment of the present application also provides a manufacturing method of a water-immersion sensing optical fiber, including the following steps:

[0007] Obtain a fiber to be processed, strip at least part of the cladding layer and the coating layer of the fiber to be processed to obtain the stripped fiber to be processed;

[0008] Obtain a solution made of a water-immersion sensitive material. The water-immersion sensitive material has a water absorption property, and the degree of change in refractive index under water-immersion conditions is greater than the degree of change of the humidity sensitive material in a humidity environment;

[0009] Uniformly coat the surface of the stripped fiber to be processed with the water-immersion sensitive material solution to obtain the coated fiber to be processed;

[0010] Place the coated optical fiber to be processed in a high-temperature drying oven for film curing to obtain a water immersion sensing optical fiber.

[0011] An embodiment of the present application further provides a water immersion detection device, including a water immersion sensing optical fiber, an optical time domain reflectometry (OTDR) device, and a data processing unit; the water immersion sensing optical fiber is connected to the OTDR device, and the OTDR device is connected to the data processing unit;

[0012] The OTDR device is configured to transmit an optical signal to the water immersion sensing optical fiber and receive the optical signal reflected back from the water immersion sensing optical fiber;

[0013] The data processing unit obtains the transmitted and received optical signals from the OTDR device, calculates the optical propagation loss of the optical signal in the water immersion sensing optical fiber, and determines the water immersion information based on the optical propagation loss.

[0014] An embodiment of the present application further provides a water immersion detection system for underground pipelines, including a plurality of water immersion sensing optical fibers, an OTDR device, and a data processing unit;

[0015] The plurality of water immersion sensing optical fibers are respectively connected to the OTDR device, and the OTDR device is connected to the data processing unit;

[0016] The plurality of water immersion sensing optical fibers are respectively arranged at a plurality of water immersion detection positions of the underground pipeline;

[0017] The OTDR device is configured to transmit an optical signal to the water immersion sensing optical fiber and receive the optical signal reflected back from the water immersion sensing optical fiber;

[0018] The data processing unit obtains the transmitted and received optical signals from the OTDR device, calculates the optical propagation loss of the optical signal in the water immersion sensing optical fiber, and determines the water immersion information of the corresponding water immersion detection position based on the optical propagation loss.

[0019] An embodiment of the present application provides a water immersion sensing optical fiber that is sensitive to water immersion and not easily interfered by humidity. It includes a water immersion sensing part, and the water immersion sensing part includes a core layer and a cladding layer from the inside outwards. The cladding layer is obtained by film curing with a specific water immersion sensitive material. This specific water immersion sensitive material has a water absorption characteristic, and the degree of refractive index change under water immersion conditions is greater than that of the humidity sensitive material under humidity environment. This characteristic enables an obvious refractive index change to occur when the water immersion sensing part is immersed in water, so that it can be accurately identified by the optical fiber sensing system, and it is not easily interfered by environmental humidity. The water immersion sensing optical fiber of the embodiment of the present application is suitable for water immersion detection, especially for water immersion detection of underground pipelines in the technical scenario of the embodiment of the present application.

[0020] Meanwhile, the embodiment of the present application provides a manufacturing method for an immersion sensing optical fiber. A fiber to be processed is obtained, and at least part of the cladding and coating of the fiber are stripped to obtain the fiber to be processed after stripping. A solution made of an immersion-sensitive material is obtained, and the immersion-sensitive material solution is uniformly coated on the surface of the fiber after part of the cladding and coating are stripped. The coated fiber is placed in a high-temperature drying oven for film curing. Through high-temperature drying treatment, a stable film is formed by the immersion-sensitive material on the surface of the fiber, thereby manufacturing the immersion sensing optical fiber. The sensing optical fiber manufactured by using the manufacturing method of the immersion sensing optical fiber in the embodiment of the present application can be applied to accurately monitor the immersion situation in underground pipelines or other application scenarios. It has the advantages of fast response speed, high accuracy, good stability, etc., and can effectively solve the problems that the existing optical fiber humidity sensors are interfered by environmental humidity and are prone to false alarms in the detection of underground pipeline immersion. At the same time, the manufacturing method of the present application is simple and easy to implement, and has broad application prospects and market value.

[0021] The immersion detection device in the embodiment of the present application provides an efficient, accurate, and real-time immersion monitoring solution, which is applicable to various scenarios that need to monitor the immersion situation along the optical fiber.

[0022] The underground pipeline immersion detection system in the embodiment of the present application can realize efficient monitoring of the pipeline immersion situation by arranging a plurality of immersion sensing optical fibers at key positions of the underground pipeline.

[0023] For better understanding and implementation, the present application will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0024] Figure 1 It is a schematic flowchart of the manufacturing method of the immersion sensing optical fiber in the embodiment of the present application;

[0025] Figure 2 It is a schematic diagram of connecting the immersion sensing optical fiber with an ordinary single-mode optical fiber and using an optical time domain reflectometer for detection in the embodiment of the present application;

[0026] Figure 3 It is a schematic diagram of the change of the optical propagation loss with the immersion time of the immersion sensing optical fiber in the immersion test in the embodiment of the present application;

[0027] Figure 4 It is a schematic diagram of the change of the optical propagation loss with time of the immersion sensing optical fiber under humidity conditions in the embodiment of the present application. Detailed Embodiments

[0028] To make the purpose, technical solutions, and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings. Among them, when the following description involves the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0029] It should be clear that the embodiments described in the following embodiments do not represent all embodiments consistent with this application. On the contrary, they are only examples of devices and methods consistent with some aspects of this application as detailed in the appended claims. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0030] The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" used in this application are also intended to include the plural forms unless the context clearly indicates otherwise. In addition, in the description of this application, unless otherwise stated, "a plurality of" means two or more. It should also be understood that the term "and / or" used herein means and includes any or all possible combinations of one or more of the associated listed items. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone; the character " / " generally indicates an "or" relationship between the contextually related objects.

[0031] It should be understood that although terms such as first, second, and third may be used in this application to describe various information, such information should not be limited to these terms. Moreover, these terms are only used to distinguish similar objects and do not have to be used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances. Depending on the context, the words "if" / "when" used in this application can be interpreted as "when...", "when...", or "in response to a determination".

[0032] With the acceleration of the urbanization process, the complexity and aging problems of the underground pipeline system have become increasingly prominent, and the maintenance of pipelines, especially the detection of waterlogging problems, has become particularly difficult. Traditional underground pipeline detection technologies, such as closed-circuit television detection technology, pipeline rapid inspection detection technology, sonar detection, and ground-penetrating radar, although they can effectively detect the location and layout of pipelines, have obvious deficiencies in waterlogging detection. These technologies often cannot quickly and accurately identify waterlogging points in pipelines, posing a hidden danger to the safe operation of urban infrastructure.

[0033] In recent years, detection technologies based on fiber optic sensing have received extensive attention due to their unique advantages. However, existing fiber optic humidity sensors are too sensitive to humidity changes, resulting in false alarms in waterlogging detection and making it difficult to achieve accurate detection. Therefore, it is particularly important to develop a fiber optic sensor suitable for detecting waterlogging in underground pipelines.

[0034] The embodiments of the present application provide a water-immersion sensing optical fiber, a manufacturing method thereof, a water-immersion detection device, and a water-immersion detection system, aiming to solve the technical problems of high sensitivity and easy false alarms of existing optical fiber humidity sensors in the detection of water immersion in underground pipelines.

[0035] The embodiments of the present application provide a water-immersion sensing optical fiber, including a water-immersion sensing part. The water-immersion sensing part sequentially includes a core layer and a cladding layer from the inside out. The cladding layer is obtained by thin-film curing of a water-immersion sensitive material; the water-immersion sensitive material has a water absorption characteristic, and the degree of change in refractive index under water-immersion conditions is greater than the degree of change in humidity-sensitive materials under a humidity environment.

[0036] Among them, the water-immersion sensing part is the part of the water-immersion sensing optical fiber responsible for sensing moisture. When the water-immersion sensing part is immersed in water, it can undergo a change in optical properties, thereby transmitting a water-immersion signal.

[0037] The core layer is one of the basic components of the optical fiber and is located at the center of the optical fiber. In the water-immersion sensing optical fiber, the core layer is usually used to transmit optical signals. The material selection of the core layer has an important impact on its optical performance, but in this embodiment, the main focus is on the outer cladding structure.

[0038] The cladding layer is the outer structure surrounding the core layer and plays a crucial role in the water-immersion sensing optical fiber. In this embodiment, the cladding layer is obtained by thin-film curing of a water-immersion sensitive material. The cladding layer not only protects the core layer from external environmental interference but also realizes the response to water molecules through its special material properties.

[0039] The water-immersion sensitive material is a material that can significantly change its optical properties after interacting with water molecules. This change in optical properties can be manifested as changes in optical parameters such as refractive index, absorption coefficient, and light transmittance. Therefore, in this embodiment, the water-immersion sensitive material is used to make the cladding layer of the water-immersion sensing optical fiber. When the water-immersion sensitive material absorbs water, its optical properties will change significantly. This change can be used to detect whether the optical fiber is immersed in water. Compared with humidity-sensitive materials, the water-immersion sensitive material has a greater degree of change in refractive index under water-immersion conditions, so its response to humidity is relatively much smaller, and thus when detecting water-immersion conditions, it can be free from or ignore the interference of environmental humidity.

[0040] Thin-film curing is the process of forming the cladding layer with the water-immersion sensitive material. Usually, this involves coating a liquid or plastic material on the core layer and then curing it into a solid thin film by heating, ultraviolet irradiation, or other methods. This process ensures the stability and consistency of the cladding layer, thereby guaranteeing the reliability of the water-immersion sensing optical fiber.

[0041] The water-immersion sensing optical fiber of this embodiment uses a unique water-immersion sensitive material as the cladding. The water-immersion sensing optical fiber is hardly affected by humidity, or this influence is very small compared to water immersion and has no significant impact. Therefore, the requirements for the measurement environment are relatively low, and it can be free from the interference of environmental humidity, yet can accurately measure the water-immersion situation. The water-immersion sensing optical fiber of this embodiment can be applied to accurately monitor the water-immersion situation in underground pipelines or other application scenarios. This kind of optical fiber has the advantages of simple structure, easy layout and maintenance, etc., providing a new solution for water-immersion monitoring.

[0042] Please refer to Figure 1 , this application embodiment also provides a manufacturing method of the water-immersion sensing optical fiber, including the following steps:

[0043] S101: Obtain the optical fiber to be processed, strip at least part of the cladding and coating layer of the optical fiber to be processed, and obtain the stripped optical fiber to be processed;

[0044] This step does not limit the specific type of the optical fiber. To manufacture the water-immersion sensing optical fiber, at least part of the cladding and coating layer of the optical fiber needs to be stripped. The process of stripping the cladding and coating layer is usually completed using a special optical fiber stripper or stripping knife. The stripped optical fiber to be processed includes the fiber core and part of the cladding wrapped outside the fiber core. After stripping, the surface of the optical fiber needs to be cleaned to ensure it is clean and free of impurities for subsequent coating with the water-immersion sensitive material.

[0045] S102: Obtain a solution made of the water-immersion sensitive material; wherein, the water-immersion sensitive material has the property of absorbing water, and the degree of change in refractive index under water-immersion conditions is greater than the degree of change of the humidity-sensitive material in a humidity environment;

[0046] In this step, a solution made of the water-immersion sensitive material needs to be prepared. When making the solution, the water-immersion sensitive material needs to be dissolved in an appropriate solvent to form a uniform solution. The concentration and viscosity of the solution are adjusted according to the specific material and coating process.

[0047] S103: Uniformly coat the surface of the stripped optical fiber to be processed with the water-immersion sensitive material solution to obtain the coated optical fiber to be processed;

[0048] In this step, the water-immersion sensitive material solution is uniformly coated on the surface of the optical fiber exposed after stripping the coating layer and part of the cladding. The coating process can be completed using methods such as drop coating, dip coating, spraying or brushing, and the specific method depends on the nature of the solution and the availability of coating equipment. The key to coating is to ensure that the solution is evenly distributed on the surface of the optical fiber and the coating thickness is consistent. An overly thick coating may lead to a decrease in sensitivity, while an overly thin coating may not provide sufficient protection or response. Therefore, parameters such as the concentration, viscosity and coating speed of the solution need to be strictly controlled during the coating process.

[0049] S104: Place the coated optical fiber to be processed in a high-temperature drying oven for film curing to obtain a water-immersion sensing optical fiber.

[0050] In this step, the coated optical fiber to be processed needs to be placed in a high-temperature drying oven for film curing. The purpose of curing is to form a stable film of the water-immersion sensitive material on the surface of the optical fiber, thereby ensuring the reliability and stability of the water-immersion sensing optical fiber. The temperature and time of the high-temperature drying oven are adjusted according to the specific material and coating thickness. During the curing process, it is necessary to ensure that the optical fiber remains stationary to avoid cracks or peeling of the coating. After curing is completed, the optical fiber should be carefully taken out and its surface should be checked for flatness and no defects.

[0051] In summary, the sensing optical fiber prepared by the method for manufacturing a water-immersion sensing optical fiber according to the embodiment of the present application has the advantages of fast response speed, high accuracy, good stability, etc., and can effectively solve the problems of too high sensitivity and easy false alarm of existing optical fiber humidity sensors in the detection of water immersion in underground pipelines. At the same time, the manufacturing method of the present application is simple and easy to implement, and has broad application prospects and market value.

[0052] In one embodiment, after the step of removing at least a part of the cladding and coating layer of the optical fiber to be processed in step S101, the following steps are further included:

[0053] Wipe the surface of the optical fiber to be processed with a cleaning solution to remove impurities on the surface.

[0054] In this embodiment, after removing a part of the cladding and coating layer, some tiny impurities, dust or oil stains may remain on the surface of the optical fiber. If these impurities are not removed, they may affect the bonding force between the subsequent coated water-immersion sensitive material and the surface of the optical fiber, and may even introduce additional optical losses or noise. Therefore, before coating the water-immersion sensitive material, it is necessary to ensure the cleanliness of the optical fiber surface. The choice of the cleaning solution is determined according to the nature of the optical fiber surface material and the type of impurities. For example, for some optical fiber materials, anhydrous ethanol, acetone or a special optical fiber cleaner can be used as the cleaning solution. In one embodiment, the cleaning solution is alcohol. When wiping, soft cotton swabs, lens paper or special optical fiber wiping cloth should be used to avoid scratching or damaging the surface of the optical fiber. The wiping process should be gentle and uniform to ensure that every part of the optical fiber surface is fully cleaned. After wiping, clean air or nitrogen should be used to dry the surface of the optical fiber to remove the residual cleaning solution and any possible moisture.

[0055] In summary, in this embodiment, by adding the step of wiping the surface of the optical fiber with a cleaning solution, the cleanliness of the optical fiber surface is ensured, thereby improving the manufacturing quality and performance of the immersion sensing optical fiber. This helps to enhance the bonding force between the immersion-sensitive material and the optical fiber surface, reduce optical loss and noise, and enable the immersion sensing optical fiber to produce more accurate and stable optical property changes when immersed in water.

[0056] In one embodiment, the step of obtaining the solution for making the immersion-sensitive material in step S102 includes:

[0057] Step S1021, obtain the immersion-sensitive material;

[0058] In this step, an immersion-sensitive material with water absorption characteristics and a significant refractive index change under immersion conditions needs to be selected. The selection of this material should be comprehensively considered based on factors such as its chemical stability, optical properties, and compatibility with the optical fiber core. Common immersion-sensitive materials can include certain specific polymers, gels, or composite materials, etc.

[0059] Step S1022, configure the immersion-sensitive material into an immersion-sensitive material solution according to the solution concentration and viscosity conditions required for optical fiber coating.

[0060] After obtaining the immersion-sensitive material, this step configures it into a solution suitable for optical fiber coating. This includes determining the concentration and viscosity of the solution, and these two parameters have an important impact on the subsequent coating effect and the performance of the cured film. The selection of the concentration should ensure that a uniform and continuous film can be formed during the coating process, while avoiding a too thick coating that may lead to a decrease in sensitivity or a too thin coating that cannot provide sufficient protection. The adjustment of the viscosity helps to control the fluidity of the solution, enabling it to better adhere to the optical fiber surface and form a stable film structure during the curing process.

[0061] In one embodiment, the immersion-sensitive material includes a polyimide material;

[0062] The step of placing the coated optical fiber to be processed in a high-temperature drying oven for film curing to obtain an immersion sensing optical fiber in step S104 includes:

[0063] Step S1041, place the coated optical fiber to be processed in a high-temperature drying oven, slowly heat the temperature in the high-temperature drying oven to 100 °C and hold for 30 minutes, then slowly raise the temperature to 150 °C and hold for 40 minutes; then raise the temperature to 280 °C and hold for 30 minutes; cool down naturally in the high-temperature drying oven, and form a polyimide film on the surface of the coated optical fiber to be processed; obtain the immersion sensing optical fiber.

[0064] In this embodiment, polyimide material is selected as the water immersion sensitive material. Polyimide is a type of high-performance polymer with excellent thermal stability, chemical stability, and mechanical strength. In addition, the optical properties (such as refractive index) of polyimide change significantly after absorbing water, making it an ideal material for fabricating water immersion sensing optical fibers.

[0065] Step S104 details the process of curing the coated optical fiber to be processed in a high-temperature drying oven, which is specifically divided into the following sub-steps:

[0066] Preheating stage: Place the coated optical fiber to be processed in a high-temperature drying oven. Slowly heat the temperature inside the high-temperature drying oven to 100 °C and maintain it for 30 minutes. This stage is mainly to allow the solvent in the coating layer to gradually volatilize, and at the same time, the polyimide material starts to soften, preparing for the subsequent curing process.

[0067] Heating and curing stage: Then slowly raise the temperature to 150 °C and maintain it for 40 minutes. This stage further promotes the volatilization of the solvent and the rearrangement of polyimide molecules, enhancing the denseness and mechanical strength of the film. Then raise the temperature to 280 °C and maintain it for 30 minutes. This is the key stage of the curing process. At high temperatures, polyimide molecules undergo cross-linking reactions to form a stable network structure, thereby endowing the film with excellent thermal stability and chemical stability.

[0068] Cooling stage: Naturally cool down in the high-temperature drying oven. This stage is to avoid internal stress or cracks in the film caused by rapid temperature changes.

[0069] Result: A polyimide film is formed on the exposed surface of the optical fiber to be processed. This film has excellent water immersion sensitivity and can respond to changes in moisture around the optical fiber, thereby realizing the water immersion sensing function.

[0070] Final product: A water immersion sensing optical fiber is obtained. This optical fiber not only has excellent sensing performance but also maintains good mechanical strength and thermal stability, and is suitable for water immersion monitoring tasks in various harsh environments.

[0071] Principle explanation:

[0072] As a water-absorbing material, the refractive index of polyimide changes after absorbing water. Since it is coated on the optical fiber, when the optical fiber is immersed in water, the polyimide absorbs water and its refractive index changes, causing the refractive index of the optical fiber cladding to change. When the optical fiber sensing region is placed in a medium with a refractive index different from that of the cladding, the mode field distribution will change. The mode field overlap factor T between the cladding region and the sensing region can be expressed as:

[0073] where, ψ e and ψ respectively represent the electric field distributions of the evanescent wave and the fundamental mode. The mode field factor T can also be expressed as:

[0074]

[0075] Therefore, when the optical fiber is immersed in water, the output power P changes and the optical fiber loss changes. When the optical fiber is immersed in water, due to the different concentration differences inside and outside the polyimide film, according to Fick's second law:

[0076]

[0077] where C is the water molecule concentration in the film, D is the diffusion coefficient, and t is the diffusion time. Therefore, the loss of the water-immersed sensing optical fiber is related to time after being immersed in water. The OTDR (Optical Time Domain Reflectometer) is used to detect the loss change, and the detection method is as Figure 2 , connect the water-immersed sensing optical fiber (i.e., the water-sensitive optical fiber in the figure) to the ordinary single-mode optical fiber through an FC / PC connector, and use the OTDR for detection. When the water-immersed sensing optical fiber is in water, the polyimide absorbs water and the refractive index increases. The polyimide acts as a cladding, making the output light intensity increase and the optical loss decrease. The OTDR detects the loss every 10 minutes, and the experiment is repeated multiple times to verify the repeatability and stability of the water-immersed sensing optical fiber. The experimental results are as Figure 3 , when the optical fiber is immersed in water, as the immersion time increases, the loss becomes smaller and remains stable subsequently, showing good repeatability and stability.

[0078] In addition, verify that when the water-immersed sensing optical fiber is placed in different humidity environments, the results of its loss change are as Figure 4 , the optical fiber loss decreases with the increase of humidity, but compared with being immersed in water, this loss is very small and can be ignored.

[0079] In summary, this embodiment provides a specific and feasible method for fabricating a water-immersed sensing optical fiber. This helps to ensure that the obtained water-immersed sensing optical fiber has stable performance and reliable sensing functions. At the same time, by precisely controlling the temperature and time parameters during the curing process, the yield and consistency of the water-immersed sensing optical fiber can be further improved. The water-immersed sensing optical fiber obtained in this embodiment is hardly affected by humidity, or this influence is very small compared with being immersed in water and has no significant impact. Therefore, the requirements for the measurement environment are relatively low, and it can be free from the interference of environmental humidity but can accurately measure the immersion situation.

[0080] In one embodiment, after the step of forming a polyimide film on the surface of the coated optical fiber to be processed in step S1041, the following steps are further included:

[0081] Fuse the optical fiber to be processed with a single-mode fiber jumper to obtain a water-immersed sensing optical fiber.

[0082] In step S1041 of the above embodiment, the process of forming a polyimide film on the exposed surface of the optical fiber to be processed has been completed. Next, in order to integrate this optical fiber with the function of detecting water immersion into the optical fiber network, it is necessary to splice it with a single-mode fiber jumper. The splicing process is usually completed using an optical fiber splicer. First, a section of the cladding and coating of the optical fiber to be processed (i.e., the part with the polyimide film) and the single-mode fiber jumper are respectively stripped off to expose the clean fiber core. Then, the fiber cores of the two optical fibers are aligned and placed into the splicing chamber of the optical fiber splicer. During the splicing process, the optical fiber splicer will use a high-temperature electric arc or laser beam to melt and butt the fiber cores of the two optical fibers together.

[0083] In summary, this embodiment provides a more complete and practical method for manufacturing an optical fiber for detecting water immersion by adding the step of splicing the optical fiber to be processed with a single-mode fiber jumper. This helps to integrate the optical fiber for detecting water immersion into the existing optical fiber network and realize remote monitoring and control functions.

[0084] The embodiment of the present application also provides a water immersion detection device, including the water immersion sensing optical fiber, an optical time domain reflectometry (OTDR) device, and a data processing unit in the above embodiment; the water immersion sensing optical fiber is connected to the OTDR device, and the OTDR device is connected to the data processing unit;

[0085] The OTDR device is used to emit an optical signal to the water immersion sensing optical fiber and receive the optical signal reflected from the water immersion sensing optical fiber;

[0086] The data processing unit obtains the emitted and received optical signals from the OTDR device, calculates the optical propagation loss of the optical signal in the water immersion sensing optical fiber, and determines the water immersion information according to the optical propagation loss.

[0087] This embodiment provides a water immersion detection device based on a water immersion sensing optical fiber. This device combines a water immersion sensing optical fiber, an OTDR device, and a data processing unit to jointly achieve precise detection of the water immersion situation along the optical fiber.

[0088] Among them, the water immersion sensing optical fiber is the core part of the device and is made of a water immersion sensitive material (such as polyimide) film in the above embodiment. When water immersion occurs along the optical fiber, the optical properties (such as refractive index) of the water immersion sensitive film will change, resulting in a change in the optical propagation loss of the optical signal in the optical fiber.

[0089] The OTDR device is a commonly used optical fiber testing instrument. It can emit a high-power pulsed optical signal into the optical fiber and receive the optical signals reflected from various positions of the optical fiber. By measuring the intensity and delay time of the reflected optical signal, the OTDR can accurately locate the abnormal points (such as breakpoints, bends, water immersion, etc.) in the optical fiber.

[0090] A data processing unit is responsible for obtaining the optical signal data transmitted and received from the optical time domain reflectometry (OTDR) device, and calculating the optical propagation loss of the optical signal in the water immersion sensing optical fiber through a specific algorithm. According to the change of the optical propagation loss, the data processing unit can determine the water immersion information along the optical fiber, such as the water immersion position, the degree of water immersion, etc.

[0091] Working principle: When the device is working, the OTDR device first emits an optical pulse signal into the water immersion sensing optical fiber. When this optical pulse signal propagates in the optical fiber, it will encounter the optical propagation loss caused by the water immersion sensitive film. When the optical pulse signal reaches the end of the optical fiber or encounters other abnormal points, it will be reflected back and received by the OTDR device. The data processing unit obtains the reflected optical signal data from the OTDR device and processes and analyzes it. By comparing the intensity difference between the transmitted optical signal and the received optical signal, the data processing unit can calculate the optical propagation loss of the optical signal in the optical fiber. Then, according to a preset threshold or algorithm, the data processing unit can determine the water immersion information along the optical fiber.

[0092] In summary, the water immersion detection device of the present application provides an efficient, accurate and real-time water immersion monitoring solution, which is applicable to various scenarios that require monitoring of water immersion along the optical fiber.

[0093] The embodiment of the present application also provides a water immersion detection system for underground pipelines, including a plurality of the water immersion sensing optical fibers, an OTDR device and a data processing unit in the above embodiments;

[0094] The plurality of water immersion sensing optical fibers are respectively connected to the OTDR device, and the OTDR device is connected to the data processing unit;

[0095] The plurality of water immersion sensing optical fibers are respectively arranged at a plurality of water immersion detection positions of the underground pipeline;

[0096] The OTDR device is used to emit an optical signal to the water immersion sensing optical fiber and receive the optical signal reflected from the water immersion sensing optical fiber;

[0097] The data processing unit obtains the transmitted and received optical signals from the OTDR device, calculates the optical propagation loss of the optical signal in the water immersion sensing optical fiber, and determines the water immersion information of the corresponding water immersion detection position according to the optical propagation loss.

[0098] The detection system of this embodiment employs several immersion sensing optical fibers in the above-mentioned embodiment. These optical fibers are respectively arranged at several immersion detection positions of the underground pipeline to sense and respond to the immersion conditions around the pipeline. Of course, these optical fibers, as bare fibers, usually cannot be directly arranged. In practical applications, a protection device can be added to the optical fiber according to the situation, and the protection device has holes for immersion. The immersion detection positions of the underground pipeline usually include areas prone to water accumulation such as joints, bends, and low-lying areas of the pipeline. Therefore, immersion sensing optical fibers can be arranged at these places respectively. These optical fibers should be laid along the pipeline direction and ensure good contact with the soil or water body around the pipeline to accurately sense the immersion situation.

[0099] When the system works, the optical time domain reflectometry device sequentially emits optical signals to each immersion sensing optical fiber. When the optical signal propagates in the optical fiber, it will encounter optical propagation losses caused by immersion. When the optical signal reaches the end of the optical fiber or encounters other abnormal points, it will be reflected back and received by the optical time domain reflectometry device. The data processing unit obtains the data of these reflected optical signals from the optical time domain reflectometry device and processes and analyzes them. By comparing the intensity differences between the transmitted optical signal and the received optical signal, the data processing unit can calculate the propagation loss of the optical signal in each optical fiber. Then, according to the preset threshold or algorithm, the data processing unit can determine the immersion information of each immersion detection position corresponding to the optical fiber, such as the immersion position, the degree of immersion, etc.

[0100] In summary, the underground pipeline immersion detection system of this embodiment can achieve efficient monitoring of the pipeline immersion situation by arranging several immersion sensing optical fibers at key positions of the underground pipeline. Whether it is single-point immersion or multi-point immersion, the system can identify and locate in a timely and accurate manner, providing timely warning and alarm information for users. This helps users discover and handle potential immersion problems in a timely manner, avoiding safety accidents and property losses caused thereby. Moreover, there is good compatibility and scalability among the various components of the system (immersion sensing optical fibers, optical time domain reflectometry device, data processing unit). Users can increase the number and arrangement positions of immersion sensing optical fibers according to actual needs to adapt to underground pipeline networks of different scales and complexities. In conclusion, the underground pipeline immersion detection system of this application provides an efficient, accurate, and real-time immersion monitoring solution, which is applicable to various scenarios that require monitoring of the immersion situation of underground pipelines.

[0101] The above embodiments only represent several implementation manners of this application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and this application also intends to include these modifications and deformations.

Claims

1. An immersion sensing optical fiber, characterized in that, It includes a water immersion sensing part, and the water immersion sensing part includes a core layer and a cladding layer from the inside outwards in sequence. The cladding layer is obtained by film curing with a water immersion sensitive material; the water immersion sensitive material has a water absorption property, and the degree of change in refractive index under water immersion conditions is greater than that of the humidity sensitive material under humidity environment conditions.

2. The manufacturing method of the water immersion sensing optical fiber according to claim 1, characterized in that, It includes the following steps: Obtain the optical fiber to be processed, strip at least part of the cladding layer and coating layer of the optical fiber to be processed to obtain the stripped optical fiber to be processed; Obtain a solution made of a water immersion sensitive material; wherein, the water immersion sensitive material has a water absorption property, and the degree of change in refractive index under water immersion conditions is greater than that of the humidity sensitive material under humidity environment conditions; Uniformly coat the surface of the stripped optical fiber to be processed with the water immersion sensitive material solution to obtain the coated optical fiber to be processed; Place the coated optical fiber to be processed in a high-temperature drying oven for film curing to obtain a water immersion sensing optical fiber.

3. The manufacturing method of the immersion sensing optical fiber according to claim 2, characterized in that, After the step of stripping at least part of the cladding layer and coating layer of the optical fiber to be processed, it further includes the step: Wipe the surface of the stripped optical fiber to be processed with a cleaning solution to remove surface impurities.

4. The manufacturing method of the water immersion sensing optical fiber according to claim 3, wherein, The cleaning solution uses alcohol.

5. The method for manufacturing an immersion sensing optical fiber according to claim 2, wherein, The step of obtaining a solution made of a water immersion sensitive material includes: Obtain a water immersion sensitive material; According to the solution concentration and viscosity conditions required for optical fiber coating, configure the water immersion sensitive material to obtain a water immersion sensitive material solution.

6. The manufacturing method of the immersion sensing optical fiber according to claim 5, characterized in that, The water immersion sensitive material includes a polyimide material; The step of placing the coated optical fiber to be processed in a high-temperature drying oven for film curing to obtain a water immersion sensing optical fiber includes: Place the coated optical fiber to be processed in a high-temperature drying oven, slowly heat the temperature in the high-temperature drying oven to 100 °C and hold for 30 minutes, then slowly raise the temperature to 150 °C and hold for 40 minutes; then raise the temperature to 280 °C and hold for 30 minutes; cool down naturally in the high-temperature drying oven, and form a polyimide film on the surface of the coated optical fiber to be processed; obtain a water immersion sensing optical fiber.

7. The manufacturing method of the immersion sensing optical fiber according to claim 6, characterized in that, After the step of forming a polyimide film on the surface of the coated optical fiber to be processed, it further includes the step: Fuse the optical fiber to be processed with a single-mode optical fiber jumper to obtain a water immersion sensing optical fiber.

8. An immersion detection device, characterized in that, It includes the water immersion sensing optical fiber described in claim 1 or the water immersion sensing optical fiber obtained by the method described in any one of claims 2 to 7, an optical time domain reflectometry device, and a data processing unit; the water immersion sensing optical fiber is connected to the optical time domain reflectometry device, and the optical time domain reflectometry device is connected to the data processing unit; The optical time domain reflectometry device is used to emit an optical signal to the water immersion sensing optical fiber and receive the optical signal reflected back from the water immersion sensing optical fiber; The data processing unit obtains the emitted and received optical signals from the optical time domain reflectometry device, calculates the optical propagation loss of the optical signal in the water immersion sensing optical fiber, and determines the water immersion information according to the optical propagation loss.

9. An immersion detection system for underground pipelines, characterized in that, It includes several water immersion sensing optical fibers, an optical time domain reflectometry device, and a data processing unit; the water immersion sensing optical fiber is the water immersion sensing optical fiber described in claim 1 or the water immersion sensing optical fiber obtained by the method described in any one of claims 2 to 7; The several water immersion sensing optical fibers are respectively connected to the optical time domain reflectometry device, and the optical time domain reflectometry device is connected to the data processing unit; The several water immersion sensing optical fibers are respectively arranged at several water immersion detection positions of the underground pipeline; The optical time domain reflectometry device is used to transmit an optical signal to the water immersion sensing optical fiber and receive the optical signal reflected from the water immersion sensing optical fiber; The data processing unit obtains the transmitted and received optical signals from the optical time domain reflectometry device, calculates the optical propagation loss of the optical signal in the water immersion sensing optical fiber, and determines the water immersion information of the corresponding water immersion detection position according to the optical propagation loss.

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