A sensor and sensor detection system

Abstract

The application discloses a kind of sensor and sensing detection system, it is related to optical fiber sensing device field, including: optical fiber, one end surface of the core of optical fiber is flat end surface;Cavity assembly, cavity assembly includes at flat end surface, and it is opposite flat end surface and mutually close to sensing cavity and reference cavity, sensing cavity is equipped with chamber with opening towards flat end surface, and the optical path difference between sensing cavity and reference cavity is in preset minimum range;Wherein, the inner side wall of sensing cavity and flat end surface are formed around chamber, the end surface of chamber opposite flat end surface forms first reflection surface for the light that is reflected back to core by being shot into sensing cavity via chamber, the end surface of reference cavity away from flat end surface forms second reflection surface for the light that is reflected back to core by being shot into reference cavity.The application arranges two compact FBI sensing structures in the end surface of one optical fiber, can be realized in the premise of sensing structure compact, promote the sensitivity of sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber sensing devices, in particular to a sensor and a sensor detection system. BACKGROUND

[0002] Optical fiber sensing has many advantages, such as high sensitivity, electromagnetic immunity, miniaturization and light weight, high temperature and corrosion resistance, fast response, etc. These advantages make optical fiber sensors widely used in many fields, including industry, medicine, communication, environmental monitoring and security applications. Current optical fiber sensors mainly include grating type sensors and interference type sensors. Interference type sensors have better development prospects due to their high sensitivity and the advantage of realizing diversification. Among them, the optical fiber sensor of the Fabry-Perot interferometer (FPI) is concerned in the application of optical fiber sensing due to its advantages of flexible configuration, good stability, compact structure, etc.

[0003] Optical vernier effect is often used to amplify the sensitivity of optical fiber sensors. It requires two FPIs with close optical path differences to be connected in parallel. The smaller the difference between the optical path differences of the two, the greater the amplification of the sensor sensitivity. However, the existing two optical fiber FPI parallel sensing structure is not compact enough, making the whole sensing structure too complex, and it is difficult to accurately control the optical path difference of FPI, thus affecting the amplification effect of the vernier effect on the sensitivity. SUMMARY

[0004] The present application provides a sensor and a sensor detection system, which can solve the technical problem of the existing two optical fiber FPI parallel sensing structure not being compact enough.

[0005] In a first aspect, an embodiment of the present application provides a sensor, comprising: an optical fiber, one end face of a fiber core of the optical fiber being a flat end face; a cavity assembly, the cavity assembly comprising a sensing cavity and a reference cavity located at the flat end face and facing each other and abutting each other, an inner cavity of the sensing cavity being provided with a cavity chamber with an opening facing the flat end face, and an optical path difference between the sensing cavity and the reference cavity being within a preset minimum range; wherein the inner side wall of the sensing cavity and the flat end face form the cavity chamber, and the end face of the cavity chamber facing the flat end face forms a first reflection surface for reflecting light entering the sensing cavity through the cavity chamber back to the fiber core, and the end face of the reference cavity away from the flat end face forms a second reflection surface for reflecting light entering the reference cavity back to the fiber core.

[0006] In combination with the first aspect, in an embodiment, the orthographic projection of the cavity assembly on the fiber core covers the flat end face.

[0007] With reference to the first aspect, in an embodiment, a normal projection of the sensing cavity on the fiber core covers one half of the area of the flat end face.

[0008] With reference to the first aspect, in an embodiment, a normal projection of the reference cavity on the fiber core covers one half of the area of the flat end face.

[0009] With reference to the first aspect, in an embodiment, the chamber is filled with air or solution.

[0010] With reference to the first aspect, in an embodiment, the cavity assembly further comprises a reflection part, and the reflection part extends towards the two ends of the end face of the flat end face to form an extension part, and the first reflection face is the end face of the reflection part towards the flat end face.

[0011] With reference to the first aspect, in an embodiment, the extension part and the reflection part towards the end face of the flat end face enclose the chamber.

[0012] With reference to the first aspect, in an embodiment, the material of the cavity assembly is a thermal expansion material.

[0013] With reference to the first aspect, in an embodiment, the thermal expansion material is a photoresist or a photosensitive resin polymer.

[0014] The second aspect, the embodiment of the present application provides a sensor detection system, comprising: the sensor provided by the above embodiment, and a circulator, a broadband light source and a spectrometer; three interfaces of the circulator are connected to the sensor, the broadband light source and the spectrometer respectively; output light of the broadband light source is input to the sensor through the circulator to cause reflection, to cause Fabry-Perot interference, to form reflected light, and the reflected light is output to the spectrometer through the circulator for detection.

[0015] The technical scheme provided by the embodiment of the present application brings the beneficial effects including:

[0016] The embodiment of the present application provides a sensor, comprising: an optical fiber, one end surface of a fiber core of the optical fiber is a flat end surface; a cavity assembly, the cavity assembly comprises a sensing cavity and a reference cavity which are located at the flat end surface and face each other and abut against each other. The embodiment of the present application arranges two compact FBI sensing structures at one end surface of an optical fiber, so that the overall structure of the sensor can be more compact, the overall volume of the sensor is smaller, and the development trend of miniaturization of the sensor is met. Meanwhile, the sensing cavity is provided with a chamber with an opening facing the flat end surface, and an optical path difference between the sensing cavity and the reference cavity is within a preset minimum range; wherein the inner side wall of the sensing cavity and the flat end surface surround the chamber, and the end surface of the chamber facing the flat end surface forms a first reflection surface for reflecting light entering the sensing cavity through the chamber back to the fiber core, and the end surface of the reference cavity away from the flat end surface forms a second reflection surface for reflecting light entering the reference cavity back to the fiber core. In this way, the optical path difference of the two FBIs can be accurately controlled, the sensitivity of the sensor is improved under the premise of compact sensing structure, and the sensitivity of the sensor is usually limited by the size reduction of the sensor in the related art. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0018] Figure 1 A perspective structural view of the sensor disclosed by the embodiment of the present application is shown in the figure.

[0019] Figure 2 A bottom view structural view of the sensor disclosed by the embodiment of the present application is shown in the figure.

[0020] Figure 3 A side view structural view of the sensor disclosed by the embodiment of the present application is shown in the figure.

[0021] Figure 4 An interference principle diagram of the sensor disclosed by the embodiment of the present application is shown in the figure.

[0022] Figure 5 A structural schematic view of a sensor detection system disclosed by the embodiment of the present application is shown in the figure.

[0023] The figure shows: 1, fiber core; 11, flat end surface; 2, sensing cavity; 3, reference cavity; 4, chamber; 5, reflection part; 6, extension part; 7, first reflection surface; 8, second reflection surface; 9, sensor; 10, circulator; 11, broadband light source; 12, optical spectrum analyzer. DETAILED DESCRIPTION

[0024] In order for those skilled in the technical field to better understand the scheme of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] Optical fiber sensing has many advantages, such as high sensitivity, electromagnetic immunity, miniaturization and light weight, high temperature and corrosion environment applicability, fast response, etc. These advantages make optical fiber sensors widely used in many fields, including industry, medicine, communication, environmental monitoring and security applications. The current optical fiber sensors mainly include grating type sensors and interference type sensors. Interference type sensors have better development prospects because of their high sensitivity and the advantage of realizing diversification.

[0026] Among them, the fiber sensor of the Fabry-Perot interferometer (FPI) is concerned in the application of optical fiber sensing because of its flexible configuration, good stability, compact structure and other advantages. The optical vernier effect is often used to amplify the sensitivity of the optical fiber sensor. It needs two FPIs with close optical path difference in parallel, and the smaller the difference between the optical path differences of the two, the greater the amplification factor of the sensor sensitivity. However, the existing two fiber FPI parallel sensing structure is not compact enough, making the whole sensing structure too complex, and it is difficult to accurately control the optical path difference of FPI, so it will affect the amplification effect of the vernier effect on the sensitivity.

[0027] The embodiments of the present application provide a sensor and a sensor detection system, which can solve the technical problem of the existing two fiber FPI parallel sensing structure not being compact enough.

[0028] Figure 1 A perspective view of the sensor disclosed in the embodiments of the present application. Figure 4 An interference principle diagram of the sensor disclosed in the embodiments of the present application. Combined with reference Figure 1 and Figure 4The embodiment of the present application provides a sensor, which comprises: an optical fiber, one end surface of a fiber core 1 of the optical fiber is a flat end surface 11; a cavity assembly, the cavity assembly comprises a sensing cavity 2 and a reference cavity 3 which are located at the flat end surface 11 and face each other and are in close contact with each other, an inner side wall of the sensing cavity 2 and the flat end surface 11 form a chamber 4, and an optical path difference between the sensing cavity 2 and the reference cavity 3 is within a preset minimum range; wherein an end surface of the sensing cavity 2 opposite to the flat end surface 11 forms a first reflecting surface 7 for reflecting light entering the sensing cavity 2 through the chamber 4 back to the fiber core 1, and an end surface of the reference cavity 3 away from the flat end surface 11 forms a second reflecting surface 8 for reflecting light entering the reference cavity 3 back to the fiber core 1.

[0029] Specifically, in the embodiment of the present application, after the single-mode optical fiber is cut to have the flat end surface, the cavity assembly is arranged on the flat end surface 11, the cavity assembly comprises the sensing cavity 2 and the reference cavity 3 which face the flat end surface 11 and are in close contact with each other, and the development trend of gradual miniaturization and compactness of the optical fiber sensor can be met.

[0030] Wherein, the first reflecting surface and the second reflecting surface are both smooth and flat planes, and the reflected light is also parallel when the parallel light is incident on the smooth surface, so that the reflection effect of the light can be ensured.

[0031] The optical vernier effect is usually applied to the amplification of the sensitivity of the optical fiber sensor, and two FPIs with similar optical path differences are connected in parallel, and the smaller the difference between the optical path differences of the two FPIs, the greater the amplification multiple of the sensitivity of the sensor.

[0032] Figure 2 The bottom structure diagram of the sensor disclosed by the embodiment of the present application is shown. It is combined with reference Figure 1 And Figure 2 In the embodiment of the present application, the preset minimum range can be 1m-5m. Specifically, since the optical path of the sensing cavity 2 and the reference cavity 3 is affected by the length and the refractive index of the sensing cavity 2 and the reference cavity 3. Therefore, the optical path difference between the sensing cavity 2 and the reference cavity 3 can be controlled by controlling the length or the refractive index of the sensing cavity 2 and the length or the refractive index of the reference cavity 3, and then different amplification multiples of the sensitivity of the sensor are obtained.

[0033] Specifically, the ratio of the length of the sensing cavity 2 to the optical path of the reference cavity 3 can be 1.1-1.2. Thus, the sensor disclosed by the embodiment of the present application can accurately control the optical path difference between the sensing cavity 2 and the reference cavity 3 while meeting the requirement of setting the volume of the sensor to be minimum, and the amplification of the sensitivity of the sensor through the vernier effect is realized.

[0034] Figure 3 The side structure diagram of the sensor disclosed by the embodiment of the present application is shown. It is combined with reference Figure 3In the embodiments of the present disclosure, the normal projection of the cavity assembly on the fiber core 1 covers the flat end face 11. In this way, the reflection effect of the cavity assembly on the input light can be guaranteed.

[0035] In the embodiments of the present disclosure, the normal projection of the cavity assembly on the fiber core 1 covers the flat end face 11. In this way, the reflection effect of the cavity assembly on the input light can be guaranteed.

[0036] In the embodiments of the present disclosure, the normal projection of the cavity assembly on the fiber core 1 covers the flat end face 11. In this way, the reflection effect of the cavity assembly on the input light can be guaranteed.

[0037] In an alternative embodiment, specifically, the ratio of the sum of the projection areas of the normal projection of the sensing cavity 2 on the fiber core 1 and the normal projection of the reference cavity 3 on the fiber core 1 to the area of the flat end face 11 is 4 / π. In this way, the cavity assembly is set to the minimum volume within a feasible range, and the sensing cavity 2 and the reference cavity 3 are only dependent on each other, so that the volume of the sensor is smaller, the structure is more compact, and the stability is better.

[0038] In an embodiment, the cavity 4 is filled with air or solution.

[0039] Specifically, in combination with the above description Figure 1 and Figure 4 The light incident from the fiber core 1 into the cavity assembly is mainly reflected at two places, i.e., the flat end face 11 and the first reflecting face 7 or the second reflecting face 8, and the two parts of the reflected light are reversely transmitted in the fiber core 1 and interfere with each other, which makes the sensing cavity 2 or the reference cavity 3 constitute an interferometer.

[0040] When the cavity 4 is filled with air, for the sensing cavity 2, the incident light is first reflected by the flat end face 11 (fiber-air interface), the remaining light is propagated in the cavity 4, and then is reflected by the first reflecting face 7 (air-solid structure interface of the sensing cavity 2), so that the optical path of the cavity 4 is air. For the reference cavity 3, the incident light is first reflected by the flat end face 11 (fiber-solid structure interface of the reference cavity 3), the remaining light is propagated in the solid structure, and then is reflected by the second reflecting face 8 (solid structure-air interface of the reference cavity 3), so that the optical path of the reference cavity 3 is the solid structure of the reference cavity 3.

[0041] Specifically, the sensing cavity 2 and the reference cavity 3 of the embodiments of the present disclosure have different optical path differences. The light of the mode field is incident into the sensing cavity 2 and the reference cavity 3 respectively, and the reflected light of the different reflecting faces is superimposed in the fiber, so that the parallel connection of two FPIs can be realized on one fiber end face, and the structure of the sensor is more compact.

[0042] When sensing, the refractive index inside the sensing cavity 2 changes, which leads to the change of the optical path difference. The inside of the reference cavity 3 is solid structure, which does not change the optical path difference. According to the vernier effect, when the reflection spectrum of the sensing cavity 2 moves, the envelope of the combined spectrum of the two cavities moves by a multiple, thereby realizing the amplification of the sensing sensitivity of the sensing cavity 2.

[0043] When the chamber 4 is filled with a solution, for the sensing cavity 2, the incident light is first reflected by the flat end face 11 (fiber-solution interface), the remaining light propagates in the chamber 4, and is then reflected by the first reflecting face 7 (solution-solid structure interface of the sensing cavity 2), so the optical path of the chamber 4 becomes the solution. For the reference cavity 3, the incident light is first reflected by the flat end face 11 (fiber-solid structure interface of the reference cavity 3), the remaining light propagates in the solid structure, and is then reflected by the second reflecting face 8 (solid structure-solution interface of the reference cavity 3), so the optical path of the reference cavity 3 is the solid structure of the reference cavity 3.

[0044] When the refractive index of the solution changes, the optical path difference of the sensing cavity 2 also changes. The change of the refractive index can be measured by the wavelength of the reflection spectrum. In addition, by filling the chamber 4 with a special material sensitive to the refractive index of the sensing substance, the detection of substances such as special ions in the solution, harmful gases in the air, etc. can also be realized.

[0045] In the embodiment of the present application, the cavity assembly further comprises a reflecting part 5, and the reflecting part 5 extends towards both ends of the end face of the flat end face 11 to form an extension part 6, and the first reflecting face 7 is the end face of the reflecting part 5 towards the flat end face 11.

[0046] In the embodiment of the present application, the extension part 6 and the end face of the reflecting part 5 towards the flat end face 11 jointly form the chamber 4. With reference to the foregoing Figure 1 and Figure 2 , the chamber 4 penetrates the sensing cavity 2, the length of the reference cavity 3 is less than the length of the sensing cavity 2, and the length of the chamber 4 is also greater than the length of the reference cavity 3, and the chamber 4 protrudes from the reference cavity 3. Therefore, the liquid or gas in the outside world can enter the chamber 4, thereby realizing the difference between the optical path difference of the sensing cavity 2 and the optical path difference of the reference cavity 3.

[0047] In the embodiment of the present application, the material of the cavity assembly is a thermal expansion material. That is, the solid structure of the sensing cavity 2 and the solid structure of the reference cavity 3 are both made of a thermal expansion material.

[0048] Specifically, the thermal expansion material is photoresist or photosensitive resin polymer. In some other embodiments of the present application, other materials can also be used to prepare the cavity assembly, as long as the sensing cavity 2 and the reference cavity 3 have different optical path differences, which are not limited herein.

[0049] In an embodiment of the present application, the cavity assembly can be printed by 3D printing technology. Specifically, after a single-mode cut out a flat end face, it is fixed on the printing table, and the high-power objective lens of the 3D printer is used to find the position of the fiber core 1 on the flat end face 11, and the cavity assembly is printed on the flat end face 11. Since 3D printing technology has the advantages of high customization and high precision, it can accurately control the optical path difference between the sensing cavity 2 and the reference cavity 3 in the cavity assembly. Since the 3D printed structure has high repeatability, it can achieve rapid and repeated printing of the cavity assembly, thereby improving the production efficiency of the sensor. At the same time, the use of 3D printing to prepare the cavity assembly can improve the structural stability of the sensor and reduce the production cost of the sensor.

[0050] An embodiment of the present application provides a sensor comprising: an optical fiber having a flat end face at one end of its core; and a cavity assembly comprising a sensing cavity and a reference cavity located at, facing, and in close proximity to the flat end face. This embodiment of the present application arranges two compact FBI sensing structures on the end face of a single optical fiber, thereby making the overall sensor structure more compact and reducing its overall size, in line with the trend of sensor miniaturization. Furthermore, the sensing cavity comprises a chamber opening toward the flat end face, and the optical path difference between the sensing cavity and the reference cavity is within a predetermined minimum range. The inner sidewall of the sensing cavity and the flat end face enclose the chamber, and the end face of the chamber facing the flat end face forms a first reflective surface for reflecting light entering the sensing cavity through the chamber back to the fiber core. The end face of the reference cavity, facing away from the flat end face, forms a second reflective surface for reflecting light entering the reference cavity back to the fiber core. With this setting, the optical path difference between the two FBIs can be precisely controlled, thereby improving the sensitivity of the sensor while maintaining a compact sensor structure, solving the problem in related technologies that the sensitivity of the sensor is usually limited by the reduction of the sensor size.

[0051] Figure 5 This is a schematic diagram of the structure of the sensor 9 detection system disclosed in the embodiment of this application. Figure 5 The embodiment of the present application also provides a sensor detection system, comprising: a sensor 9 as provided in the above embodiment, as well as a circulator 10, a broadband light source 11 and a spectrometer 12; the three interfaces of the circulator 10 are respectively connected to the sensor 9, the broadband light source 11 and the spectrometer 12; the output light of the broadband light source 11 is input to the sensor 9 through the circulator 10 and reflected, causing Fabry-Perot interference to form reflected light, and the reflected light is output to the spectrometer 12 through the circulator 10 for detection.

[0052] Specifically, since the reference cavity and the sensing cavity in the sensor 9 form a parallel structure, the broadband light source 11 opens the supercontinuum spectrum light source, which is input to the reference cavity and the sensing cavity through the circulator 10, and the output spectrum of the parallel structure of the reference cavity and the sensing cavity is composed of a series of high-frequency interference fringes arranged periodically in amplitude, and a low-frequency envelope is superimposed on the peak value of the high-frequency signal. Among them, the low-frequency envelope in the combined reflection spectrum of the sensing cavity and the reference cavity is used as the reference for measuring parameters such as temperature or pressure. The low-frequency envelope is given by the difference between the optical path differences of the two, which is clearly visible in the combined reflection spectrum. By observing the wavelength shift of the wave crest and trough of the low-frequency envelope, high-sensitivity sensing is achieved.

[0053] A chamber is arranged in the sensing cavity. When the chamber is filled with air, the refractive index inside the sensing cavity changes during sensing, causing the optical path difference to change, so that the output spectrum of the parallel structure of the reference cavity and the sensing cavity will obviously drift. The reference cavity is a solid structure and will not change the optical path difference. According to the vernier effect, when the reflection spectrum of the sensing cavity moves, the envelope of the combined spectrum of the two cavities will move by a multiple, thereby realizing the amplification of the sensing sensitivity of the sensing cavity, and the sensitivity of the sensor 9 can also be significantly improved.

[0054] In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication between two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0055] It should be noted that, in the present application, the relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0056] The foregoing is considered as illustrative only of the principles of the application. Numerous modifications and changes will readily occur to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sensor, characterized in that: include: An optical fiber, wherein one end face of the core (1) of the optical fiber is a flat end face (11); A cavity assembly, the cavity assembly comprising a sensing cavity (2) and a reference cavity (3) located at the flat end surface (11), facing the flat end surface (11) and close to each other, a chamber (4) with an opening facing the flat end surface (11) is provided in the sensing cavity (2), and an optical path difference between the sensing cavity (2) and the reference cavity (3) is within a preset minimum range, the preset minimum range being 1 m to 5 m, the sensing cavity (2) and the reference cavity (3) are located at the flat end surface (11) of the same fiber core (1), and the ratio of the sum of the projection areas of the positive projection of the sensing cavity (2) on the fiber core (1) and the positive projection of the reference cavity (3) on the fiber core (1) to the area of ​​the flat end surface (11) is 4 / π; The inner side wall of the sensing cavity (2) and the flat end surface (11) are arranged to form the cavity (4); the end surface of the cavity (4) facing the flat end surface (11) forms a first reflection surface (7) for reflecting light incident into the sensing cavity (2) via the cavity (4) back to the fiber core (1); and the end surface of the reference cavity (3) away from the flat end surface (11) forms a second reflection surface (8) for reflecting light incident into the reference cavity (3) back to the fiber core (1).

2. The sensor according to claim 1, wherein The chamber (4) is filled with air or solution.

3. The sensor according to claim 1, wherein The cavity assembly further comprises a reflecting portion (5), and both ends of the end surface of the reflecting portion (5) facing the flat end surface (11) extend toward the flat end surface (11) to form extending portions (6), and the first reflecting surface (7) is the end surface of the reflecting portion (5) facing the flat end surface (11).

4. The sensor according to claim 3, wherein The extension portion (6) and the end surface of the reflection portion (5) facing the flat end surface (11) together form the cavity (4).

5. The sensor according to claim 1, wherein The cavity component is made of a thermally expandable material.

6. The sensor according to claim 5, wherein The thermally expandable material is photoresist or photosensitive resin polymer.

7. A sensor detection system, characterized in that: include: A sensor (9) as claimed in any one of claims 1 to 6, and a circulator (10), a broadband light source and a spectrometer (12); The three interfaces of the circulator (10) are respectively connected to the sensor (9), the broadband light source and the spectrometer (12); the output light of the broadband light source is input to the sensor (9) through the circulator (10) for reflection, causing Fabry-Perot interference to form reflected light, and the reflected light is output to the spectrometer (12) for detection through the circulator (10).

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