Fiber Bragg Grating Temperature and Humidity Integrated Sensor Array and Temperature and Humidity Measurement Method

Abstract

The present invention relates to a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array and a temperature and humidity measurement method, comprising: a Bragg fiber Bragg grating array, a non-humidity sensitive material coating layer, a humidity sensitive material coating layer, and a mesh armor protective layer; the non-humidity sensitive material is indirectly and periodically coated on the Bragg fiber grating to form a non-humidity sensitive material coating layer, and the humidity sensitive material is fully coated on the Bragg fiber grating to form a humidity sensitive material coating layer; the non-humidity sensitive material is superimposed on a first grating coated with a humidity sensitive material and a second grating coated with a humidity sensitive material for sensing temperature and humidity signals; the mesh armor protective layer is sleeved on the non-humidity sensitive material coating layer and the humidity sensitive material coating layer to protect the non-humidity sensitive material, the humidity sensitive material and the Bragg fiber Bragg grating array. The present invention can achieve multi-parameter measurement of temperature and humidity on a single fiber Bragg grating array by alternately and periodically coating the humidity sensitive material coating and the non-humidity sensitive material coating on the upper surface of the Bragg fiber grating, and the installation and maintenance are simple and convenient.

Description

Technical Field

[0001] The present invention relates to the field of fiber grating sensing technology, and in particular to a fiber grating temperature and humidity integrated sensor array and a temperature and humidity measurement method. Background Art

[0002] The monitoring and measurement of relative humidity plays a very important role in industrial production, agricultural planting, health care, environmental protection and other fields. Traditional electronic temperature and humidity sensors are limited in use in many complex environments due to their large size, poor corrosion resistance and weak anti-electromagnetic interference ability. Compared with traditional temperature and humidity sensors, fiber optic sensors have the advantages of small size, light weight, high sensitivity and strong anti-electromagnetic interference ability, and are suitable for long-term use in some special environments. Among them, fiber grating temperature and humidity sensors not only have the advantages of fiber optic sensors but also have the characteristics of easy reuse. They can be formed into ultra-large-scale sensor networks, thereby further broadening their application areas.

[0003] With the increasing maturity of fiber optic sensing technology, fiber optic temperature and humidity sensors have begun to be used in various fields that traditional temperature and humidity sensors cannot measure. In the fields of construction, medical care, food industry, etc., fiber optic temperature and humidity sensors have also begun to replace traditional temperature and humidity sensors and show great application potential. For temperature and humidity sensors, parameters such as sensitivity, response time, measurement range, time drift and temperature drift are important indicators for evaluating the performance of the sensor. Among them, time drift and temperature drift are an inevitable problem for traditional temperature and humidity sensors because they are often affected by dust, oil and harmful gases. In some applications with harsh environments, the stability and reliability of traditional temperature and humidity sensors will be greatly reduced, and the advantages of fiber optic temperature and humidity sensors effectively solve the problem of using traditional temperature and humidity sensors in special scenarios.

[0004] Among the many fiber optic temperature and humidity sensors reported so far, some are based on interferometry to achieve temperature and humidity measurement. This type of sensor has certain advantages in response time and sensitivity in temperature and humidity measurement, but its common problems are low stability, temperature drift, and difficulty in cascading. Another part of the fiber optic temperature and humidity sensors is based on fiber grating coated with temperature-sensitive and humidity-sensitive materials to achieve temperature and humidity measurement. This type of sensor has certain advantages in stability and multi-sensor cascading in temperature and humidity measurement, and its temperature drift is solved by compensating for it through fiber grating temperature sensors, so at least two fiber grating arrays are required. The dual fiber temperature and humidity sensor is more complicated to operate during actual installation, and the gratings of the fiber grating temperature sensor and the humidity sensor need to be matched, otherwise it will cause the error of temperature and humidity decoupling. Summary of the invention

[0005] In view of this, it is necessary to provide a fiber grating temperature and humidity integrated sensor array and a temperature and humidity measurement method to solve the time drift and temperature drift problems of traditional electronic temperature and humidity sensors, and the difficult problem of using a combination of dual fiber grating sensors when measuring ambient temperature and humidity.

[0006] In order to solve the above problems, in the first aspect, the present invention provides a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array, comprising: a fiber Bragg grating array, a non-humidity sensitive material coating layer, a humidity sensitive material coating layer, and a mesh armor protection layer;

[0007] A non-humidity-sensitive material is indirectly and periodically coated on the Bragg fiber grating to form the non-humidity-sensitive material coating layer, and a humidity-sensitive material is fully coated on the Bragg fiber grating to form the humidity-sensitive material coating layer;

[0008] A first grating coated with a non-humidity-sensitive material and a second grating coated with a humidity-sensitive material are used to sense temperature and humidity signals;

[0009] The mesh armor protection layer is sleeved on the non-moisture-sensitive material coating layer and the moisture-sensitive material coating layer, and is used to protect the non-moisture-sensitive material, the moisture-sensitive material and the Bragg fiber grating array.

[0010] Furthermore, the fiber Bragg grating array is prepared online via a drawing tower using a phase mask writing method.

[0011] Furthermore, when preparing the fiber Bragg grating array, the bare fiber diameter of the fiber Bragg grating array is a preset diameter;

[0012] When writing gratings through the phase mask, the interval between two adjacent gratings is a first preset distance;

[0013] Two gratings spaced apart by a first preset distance are used as a temperature and humidity measurement unit, and the distance between every two temperature and humidity measurement units is a second preset distance.

[0014] Furthermore, the sensor array further comprises:

[0015] The number of gratings in the temperature and humidity measurement unit is adjustable;

[0016] The second preset distance can be adjusted according to the actual scene.

[0017] Furthermore, the non-humidity-sensitive material is acrylate; the non-humidity-sensitive material is indirectly and periodically coated on the Bragg fiber grating, comprising:

[0018] Applying a first coating layer on the fiber Bragg grating with a first coating layer thickness by an acrylate coater;

[0019] Curing the first coating layer through a UV curing machine, wherein the UV curing machine only coats the first grating of the temperature and humidity measuring unit through sinusoidal modulation;

[0020] The uncured acrylate solution on another grating in the temperature and humidity measurement unit is washed away by hot ethanol, so that the acrylate is indirectly and periodically coated on the Bragg fiber grating.

[0021] Furthermore, the moisture-sensitive material is polyimide; the moisture-sensitive material is fully coated on the Bragg fiber grating, including:

[0022] Applying a second coating layer on the Bragg fiber grating with a single-side thickness of the second coating layer by a first polyimide coater;

[0023] Pre-curing the second coating layer in a first high-temperature tube furnace within a first furnace temperature range;

[0024] The pre-cured Bragg fiber grating is pulled by a traction wheel to a second polyimide coater and coated with a third coating layer;

[0025] The third coating layer is cured in a second high-temperature tube furnace within a second furnace temperature range, so that the polyimide is fully coated on the Bragg fiber grating.

[0026] Furthermore, the temperature and humidity measurement range of the sensor array is adjusted by adjusting the thickness of the first, second or third coating layer.

[0027] Furthermore, the outer coating diameters of the first grating and the second grating in the temperature and humidity measurement unit are the same.

[0028] In a second aspect, the present invention further provides a temperature and humidity measurement method, which is applied to the above-mentioned multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array, comprising:

[0029] determining a first temperature sensitivity of the first grating, a first humidity sensitivity of the first grating, a second temperature sensitivity of the second grating, and a second humidity sensitivity of the second grating;

[0030] The temperature and humidity to be measured are decoupled using the preset dual-parameter matrix formula:

[0031]

[0032]

[0033] Where ΔT is the measured temperature, ΔRH is the measured humidity, Δλ1 is the wavelength drift of the first grating, Δλ2 is the wavelength drift of the first grating, and α T1 is the first temperature sensitivity of the first grating, α T2is the second temperature sensitivity of the second grating, α RH1 is the first humidity sensitivity of the first grating, α RH2 is the second humidity sensitivity of the second grating.

[0034] Furthermore, the method further comprises:

[0035] The first temperature sensitivity and the second temperature sensitivity are not equal, and the first humidity sensitivity and the second humidity sensitivity are not equal.

[0036] The beneficial effects of adopting the above embodiment are:

[0037] The present invention provides a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array. Based on the coated fiber Bragg grating temperature and humidity sensor, a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array is designed. Its structure adopts a weak Bragg fiber Bragg grating array, and then the moisture-sensitive material coating and the non-moisture-sensitive material coating are alternately and periodically coated on its surface, which can realize multi-parameter measurement of temperature and humidity on a single fiber Bragg grating array without adding additional sensors for compensation and correction. The installation and maintenance are simpler, more convenient, and the cost is lower. And the fiber Bragg grating temperature and humidity sensor protected by the mesh armor structure protective layer can be flexibly applied to various harsh and extreme environments. And the sensor is easy to cascade and customize the distance, which can be applied to a variety of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic structural diagram of an embodiment of a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array provided by the present invention;

[0039] Figure 2 A schematic diagram of a flow chart of an embodiment of a temperature and humidity measurement method provided by the present invention;

[0040] Figure 3 A schematic diagram of the structure of a temperature and humidity measurement unit provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0042] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. Reference to "embodiments" in this article means that the specific features, structures or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0043] The specific embodiments are described in detail below:

[0044] See also Figure 1 , Figure 1 The present invention provides a schematic structural diagram of an embodiment of a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array. A specific embodiment of the present invention discloses a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array 100, comprising:

[0045] Fiber Bragg grating array 101, non-moisture-sensitive material coating layer 102, moisture-sensitive material coating layer 103, mesh armor protection layer 104;

[0046] The non-humidity-sensitive material is indirectly and periodically coated on the Bragg fiber grating array 101 to form a non-humidity-sensitive material coating layer 102, and the humidity-sensitive material is fully coated on the Bragg fiber grating array 101 to form a humidity-sensitive material coating layer 103;

[0047] A first grating coated with a non-humidity-sensitive material and a second grating coated with a humidity-sensitive material are used to sense temperature and humidity signals;

[0048] The mesh armor protection layer 104 is sleeved on the non-moisture-sensitive material coating layer 102 and the moisture-sensitive material coating layer 103 , and is used to protect the non-moisture-sensitive material, the moisture-sensitive material and the Bragg fiber grating array 101 .

[0049] The present invention provides a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array. Based on the coated fiber Bragg grating temperature and humidity sensor, a multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array is designed. Its structure adopts a weak Bragg fiber Bragg grating array, and then the moisture-sensitive material coating and the non-moisture-sensitive material coating are alternately and periodically coated on its surface, which can realize multi-parameter measurement of temperature and humidity on a single fiber Bragg grating array without adding additional sensors for compensation and correction. The installation and maintenance are simpler, more convenient, and the cost is lower. And the fiber Bragg grating temperature and humidity sensor protected by the mesh armor structure protective layer can be flexibly applied to various harsh and extreme environments. And the sensor is easy to cascade and customize the distance, which can be applied to a variety of application scenarios.

[0050] In one embodiment of the present invention, the fiber Bragg grating array is prepared online via a drawing tower using a phase mask writing method.

[0051] When preparing the fiber Bragg grating array, the bare fiber diameter of the fiber Bragg grating array is a preset diameter;

[0052] When writing gratings through the phase mask, the interval between two adjacent gratings is a first preset distance;

[0053] Two gratings spaced apart by a first preset distance are used as a temperature and humidity measurement unit, and the distance between every two temperature and humidity measurement units is a second preset distance.

[0054] It is understandable that the fiber Bragg grating array in the present application is prepared online via a drawing tower using a phase mask writing method to achieve the preparation of a large-scale reflectivity grating array optical fiber.

[0055] Specifically, the diameter of the drawn bare fiber is first stably controlled to a preset diameter, such as about 125 μm, and the grating is engraved through a phase mask, and the spacing between two adjacent gratings is a first preset distance. The spacing between two adjacent gratings cannot be too large, and the temperature and humidity of the environment in which the two are located must be consistent, which can be 10 cm.

[0056] In addition, the number of gratings in the temperature and humidity measurement unit is adjustable, and by accurately customizing the number and spacing of sensors, it can be applied to different scenarios.

[0057] The second preset distance can be adjusted according to the actual scenario, and the distance between each two temperature and humidity measurement units can be set according to the actual application scenario, such as 1m.

[0058] In one embodiment of the present invention, the non-humidity sensitive material is acrylate; the non-humidity sensitive material is indirectly and periodically coated on the Bragg fiber grating, comprising:

[0059] Applying a first coating layer on the fiber Bragg grating with a first coating layer thickness by an acrylate coater;

[0060] The first coating layer is cured by a UV curing machine, wherein the UV curing machine only coats the first grating of the temperature and humidity measuring unit through sinusoidal modulation;

[0061] The uncured acrylate solution on another grating in the temperature and humidity measurement unit is washed away by hot ethanol, so that the acrylate is indirectly and periodically coated on the Bragg fiber grating.

[0062] It can be understood that in the process of indirectly and periodically coating the Bragg fiber grating with a non-moisture-sensitive material to form a coating layer of the non-moisture-sensitive material, a first coating layer with a thickness of 25 μm can be coated on the Bragg fiber grating by an acrylate coater, and then cured by a UV curing machine, wherein the UV curing machine only coats the first grating of the temperature and humidity measurement unit through sinusoidal modulation, and then the uncured acrylate solution is washed away with hot ethanol, so that the acrylate can be indirectly and periodically coated on the Bragg fiber grating.

[0063] In one embodiment of the present invention, the moisture sensitive material is polyimide; the moisture sensitive material is fully coated on the Bragg fiber grating, including:

[0064] Applying a second coating layer on the fiber Bragg grating with a single-side thickness of the second coating layer by a first polyimide coater;

[0065] Pre-curing the second coating layer in a first high-temperature tube furnace within a first furnace temperature range;

[0066] The pre-cured Bragg fiber grating is pulled by a traction wheel to a second polyimide coater and coated with a third coating layer;

[0067] The third coating layer is cured in a second high-temperature tube furnace within a second furnace temperature range, so that the polyimide is fully coated on the Bragg fiber grating.

[0068] It is understandable that in the process of using the moisture-sensitive material to fully coat the Bragg fiber grating to form a moisture-sensitive material coating layer, a second coating layer can be coated on the Bragg fiber grating through the first polyimide coater, wherein the single-side thickness of the second coating layer is about 6 μm, and then passed through the first high-temperature tube furnace, the furnace temperature range of the first high-temperature tube furnace is 150-250°C, to achieve the separation and pre-curing of the first layer of polyimide solvent. Then the optical fiber is pulled by the traction wheel to the second polyimide coater, and the surface of the optical fiber is coated with a uniform layer of polyimide coating again, that is, the third coating layer. After two-stage coating, the optical fiber is heated in two stages and finally passed through the second high-temperature tube furnace to achieve cyclization, further improving the mechanical properties of polyimide. Among them, the furnace temperature range of the second high-temperature tube furnace is 250-300°C.

[0069] By alternately coating the moisture-sensitive material coating and the non-moisture-sensitive material coating on the surface of the Bragg fiber grating array, multi-parameter measurement of temperature and humidity is achieved on a single fiber grating array without adding additional sensors for compensation and correction, and installation and maintenance are simpler and more convenient, and the cost is lower. In addition, the present invention can also adjust the temperature and humidity measurement range of the sensor array by adjusting the thickness of the first, second or third coating layer, so as to facilitate application in more application scenarios.

[0070] It should also be noted that, in one embodiment of the present invention, the outer coating diameters of the first grating and the second grating in the temperature and humidity measurement unit are the same, thereby ensuring that the surface of the entire optical fiber is smooth and uniform, thereby improving the measurement accuracy of temperature and humidity.

[0071] In order to better implement the multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array in the embodiment of the present invention, based on the multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array, correspondingly, please refer to Figure 2 , Figure 2 This is a flow chart of an embodiment of a temperature and humidity measurement method provided by the present invention. The embodiment of the present invention provides a temperature and humidity measurement method, which is applied to the above-mentioned multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array 100, comprising:

[0072] Step S201: determining a first temperature sensitivity of the first grating, a first humidity sensitivity of the first grating, a second temperature sensitivity of the second grating, and a second humidity sensitivity of the second grating;

[0073] Step S202: Decouple the temperature and humidity to be measured using a preset dual-parameter matrix formula:

[0074]

[0075]

[0076] Where ΔT is the measured temperature, ΔRH is the measured humidity, Δλ1 is the wavelength drift of the first grating, Δλ2 is the wavelength drift of the first grating, and α T1 is the first temperature sensitivity of the first grating, α T2 is the second temperature sensitivity of the second grating, α RH1 is the first humidity sensitivity of the first grating, α RH2 is the second humidity sensitivity of the second grating.

[0077] First of all, please refer to Figure 3 , Figure 3 A schematic diagram of the structure of a temperature and humidity measurement unit provided by an embodiment of the present invention. 1-1 The first grating of a temperature and humidity measurement unit, FBG 1-2 The second grating of the temperature and humidity measurement unit; FBG 2-1 The first grating of another temperature and humidity measurement unit, FBG 2-2 It is the second grating of the temperature and humidity measurement unit.

[0078] Due to FBG 1-1 The outer coating of FBG is acrylate plus polyimide, both of which are linear to temperature. The inner acrylate is insensitive to humidity, while the outer polyimide is sensitive to humidity and changes linearly. Therefore, 1-1 The temperature sensitivity caused by the two coating layers is α T1 , only the humidity sensitivity caused by the outer coating is α RH1 . Due to FBG 1-2 The outer coating of FBG is only polyimide, which is sensitive to temperature and humidity and changes linearly. 1-2 The temperature sensitivity caused by the single coating alone is α T2 , the humidity sensitivity is α RH2 , the two can establish the following formula:

[0079]

[0080] By further simplifying, the temperature and humidity at the temperature and humidity measurement unit are obtained:

[0081]

[0082]

[0083] It should be noted that in the multi-layer coated fiber Bragg grating integrated temperature and humidity sensor array of the present invention, the first temperature sensitivity and the second temperature sensitivity are not equal, and the first humidity sensitivity and the second humidity sensitivity are not equal, so the temperature and humidity can be decoupled using the dual parameter matrix method.

[0084] The temperature and humidity measurement method provided by the present invention facilitates the use of a dual parameter matrix method to decouple temperature and humidity, thereby improving the accuracy of temperature and humidity measurement, by setting the temperature sensitivity and humidity sensitivity in different measurement units.

[0085] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array, characterized in that: include: Fiber Bragg grating array, non-moisture-sensitive material coating, moisture-sensitive material coating, mesh armor protection layer; A non-humidity-sensitive material is indirectly and periodically coated on the Bragg fiber grating to form the non-humidity-sensitive material coating layer, and a humidity-sensitive material is fully coated on the Bragg fiber grating to form the humidity-sensitive material coating layer; A first grating coated with a non-humidity-sensitive material and a second grating coated with a humidity-sensitive material are used to sense temperature and humidity signals; The mesh armor protection layer is sleeved on the non-moisture-sensitive material coating layer and the moisture-sensitive material coating layer, and is used to protect the non-moisture-sensitive material, the moisture-sensitive material and the Bragg fiber grating array; The fiber Bragg grating array is prepared online via a drawing tower by using a phase mask writing method; When preparing the fiber Bragg grating array, the bare fiber diameter of the fiber Bragg grating array is a preset diameter; When writing gratings through the phase mask, the interval between two adjacent gratings is a first preset distance; Two gratings separated by a first preset distance are used as a temperature and humidity measurement unit, and the interval between every two temperature and humidity measurement units is a second preset distance; The non-moisture-sensitive material is acrylate; The non-humidity sensitive material is indirectly and periodically coated on the Bragg fiber grating, comprising: Applying a first coating layer on the fiber Bragg grating with a first coating layer thickness by an acrylate coater; Curing the first coating layer through a UV curing machine, wherein the UV curing machine only coats the first grating of the temperature and humidity measuring unit through sinusoidal modulation; Washing off the uncured acrylate solution on another grating in the temperature and humidity measurement unit by hot ethanol, so that the acrylate is indirectly and periodically coated on the Bragg fiber grating; The humidity sensitive material is polyimide; the humidity sensitive material is fully coated on the Bragg fiber grating, including: Applying a second coating layer on the Bragg fiber grating with a single-side thickness of the second coating layer by a first polyimide coater; Pre-curing the second coating layer in a first high-temperature tube furnace within a first furnace temperature range; The pre-cured Bragg fiber grating is pulled by a traction wheel to a second polyimide coater and coated with a third coating layer; The third coating layer is cured in a second high-temperature tube furnace within a second furnace temperature range, so that the polyimide is fully coated on the Bragg fiber grating.

2. The fiber Bragg grating temperature and humidity integrated sensor array according to claim 1, characterized in that: The number of gratings in the temperature and humidity measurement unit is adjustable; the second preset distance is adjusted according to the actual scene.

3. The fiber Bragg grating temperature and humidity integrated sensor array according to claim 1, characterized in that: The temperature and humidity measurement range of the sensor array can be adjusted by adjusting the thickness of the first, second or third coating layer.

4. The fiber Bragg grating temperature and humidity integrated sensor array according to claim 1, characterized in that: The outer coating diameters of the first grating and the second grating in the temperature and humidity measurement unit are the same.

5. A temperature and humidity measurement method, applied to the multi-layer coated fiber Bragg grating temperature and humidity integrated sensor array as claimed in any one of claims 1 to 4, characterized in that: include: determining a first temperature sensitivity of the first grating, a first humidity sensitivity of the first grating, a second temperature sensitivity of the second grating, and a second humidity sensitivity of the second grating; The temperature and humidity to be measured are decoupled using the preset dual-parameter matrix formula: ， ， in, is the measured temperature, is the measured humidity, is the wavelength shift of the first grating, is the wavelength shift of the second grating, is the first temperature sensitivity of the first grating, is the second temperature sensitivity of the second grating, is the first humidity sensitivity of the first grating, is the second humidity sensitivity of the second grating.

6. The temperature and humidity measurement method according to claim 5, characterized in that: The method further comprises: The first temperature sensitivity and the second temperature sensitivity are not equal, and the first humidity sensitivity and the second humidity sensitivity are not equal.

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