CN217877738U - Sensing structures and devices based on optical fiber coupling-induced transparency - Google Patents

Abstract

The utility model provides a sensing structure and a sensing device based on optical fiber coupling induction transparency; the sensing structure comprises an optical fiber, and the optical fiber comprises an output straight waveguide, an input straight waveguide, a first resonant cavity and a second resonant cavity; the distances between the adjacent resonant wavelengths corresponding to the first resonant cavity and the second resonant cavity are different; the first resonant cavity comprises an annular waveguide, and the first resonant cavity is in cascade connection with a second resonant cavity section in the input straight waveguide to be optically coupled, so that optical information conduction between the input straight waveguide and the first resonant cavity is realized; the first resonant cavity is a micro-ring resonant cavity, the second resonant cavity is of an F-P cavity structure, the micro-ring resonant cavity is in optical coupling connection with the F-P cavity structure and is used for free conduction of optical signals in the micro-ring resonant cavity and the F-P cavity structure, the optical signals are subjected to interference coupling in the optical fiber through the F-P cavity structure and enter the micro-ring resonant cavity through the coupling area waveguide for secondary coupling, the optical sensing volume is reduced, and the measurement accuracy of micro displacement/micro stress is further improved.

Description

Sensing structures and devices based on optical fiber coupling-induced transparency

technical field

The utility model relates to the technical field of sensor manufacturing, in particular to a sensing structure and sensing device based on optical fiber coupling induced transparency.

Background technique

Optical fiber micro-displacement sensing is a new type of sensing technology, which is widely used in mechanical manufacturing processes, bioengineering fields, and measuring physical quantities such as force, current, voltage, acceleration, refractive index, and water level. Since the determination of these factors and devices is of great significance in optical communication, micro-nano sensing detection and environmental monitoring, the research on optical fiber micro-displacement sensors has become very important. At present, the typical optical fiber micro-displacement sensing can be mainly divided into two categories: resonant ring sensing and resonant cavity sensing. Because the optical fiber ring resonator is easy to manufacture and low in cost, it is especially suitable for flammable, explosive and strictly limited space. It is used in harsh environments or in harsh environments subject to strong electromagnetic interference.

The existing technology uses optical fiber ring resonators to realize micro-displacement sensing, which has great advantages, but the resonator mostly adopts the metal cavity structure based on the plasma-induced transparency effect, and the interaction between SPPs and the light field is required to realize the light transmission. active manipulation. The above measurement accuracy is acceptable, but it cannot be compacted. In order to adapt to the development of high-precision integration, its measurement technology has certain limitations due to the influence of its own attributes.

A few days ago, a scheme of cascading epitaxial grating F-P type and microring resonator was proposed, so that compared with the previous method of multi-microring resonator cascading, the volume can be smaller, thereby reducing the cost, but the sensitivity of this method is still not enough However, there are still some restrictions on commercial use.

On the other hand, induced transparency has been gradually proposed in recent years. Electromagnetic-induced transparency is electromagnetic wave-induced transparency, which generally uses two beams of light to irradiate the atomic medium (such as a gas composed of a large number of atoms) at the same time, so that one of the beams of light can pass through the atomic medium while resonating with the atomic transition without absorption and reflection. Plasma-induced transparency is also called electromagnetically induced transparency, which is a phenomenon of electromagnetically induced transparency in the plasma direction. The coupling resonator-induced transparency effect is to realize the electromagnetic-induced transparency effect through the coherent coupling of the coupled optical resonator. The electromagnetic-induced transparency effect in this optical microcavity has potential application value in optical signal delayers, optical buffers, etc. . At the same time, microcavity has incomparable advantages for integrated optics, which is constantly developing towards integration and chip. In the existing micro-displacement/micro-stress detection technology field, there are few examples of combining the advantages of microcavities with the sensing technology based on optical fiber coupling and transparent induction.

Utility model content

In order to solve the above technical problems and realize the combination of optical fiber coupling induced transparency and microcavity, the purpose of this utility model is to provide a sensing structure and sensing device based on optical fiber coupling induced transparency.

First of all, the embodiment of the present application provides a sensing structure based on optical fiber coupling induced transparency. The sensing structure includes multiple sections of optical fiber, including an output straight waveguide and an input straight waveguide on the optical fiber, and a second straight waveguide is included between the output straight waveguide and the input straight waveguide. A resonant cavity and a second resonant cavity; the distance between adjacent resonant wavelengths corresponding to the first resonant cavity and the second resonant cavity is different, so that both the first resonant cavity and the second resonant cavity have a frequency selection function and have different Free spectral range; the first resonant cavity includes a ring waveguide, and the first resonant cavity is cascaded with the second resonant cavity segment in the input straight waveguide to optically couple to realize optical information transmission between the input straight waveguide and the first resonant cavity; The first resonator is a microring resonator, the second resonator is an F-P cavity structure, and the microring resonator and the F-P cavity structure are optically coupled and connected for the free transmission of optical signals in the microring resonator and the F-P cavity structure. Interference coupling is carried out inside the fiber through the F-P cavity structure, and the waveguide in the coupling area enters the microring resonator for secondary coupling.

In this embodiment, the position of the microring resonant cavity is fixed, the width of the F-P cavity structure is equal to the width of the input straight waveguide, and a corrugated diaphragm is arranged at the end of the F-P cavity structure.

In this embodiment, the longitudinal central axis of the F-P cavity structure is in the plane where the microring resonator is located, and the transverse central axis of the microring resonant cavity is symmetrical to the symmetry axis of the F-P cavity structure.

In this embodiment, interference coupling and secondary coupling are regarded as two kinds of excited states;

In the case of a symmetric structure, the two excited states interact to form a spectrum;

Under external influence, the structure of the microring resonator and the F-P cavity changes from a symmetrical position to an asymmetric structure, and the two excitation states of the microring resonator and the F-P cavity structure excite two modes of optical signals through the asymmetric structure. The interaction between the two modes splits the spectrum into two forbidden bands and presents a transparent window between the two forbidden bands.

In this embodiment, the medium between the microring resonant cavity and the F-P cavity structure is air, the F-P cavity structure is connected to the input straight waveguide, and the F-P cavity structure is composed of the flat end surface of the optical fiber plug and the inner surface of the corrugated diaphragm.

In this embodiment, the optical fiber includes at least one of the following: single-mode optical fiber, multi-mode optical fiber, photonic crystal optical fiber, and nanofiber.

On the other hand, the present application also provides a sensing device, including the above-mentioned sensing structure, the sensing structure is packaged in an optical fiber sensing unit, and the sensing system device also includes: an optical signal transmitter, an optical isolator, a photoelectric converter , a spectrometer and a data analysis system; wherein, the optical signal transmitter outputs the incident light, and the direction of the incident light is limited by an optical isolator, and the output end is connected to the input end of the optical fiber sensing unit through a photoelectric converter to control the optical signal. The direction is limited and sensed by the optical fiber sensing unit, and then the output light of the optical fiber sensing unit enters the spectrometer through the converter, and the modem is electrically connected to the spectrometer, and the data is analyzed by the spectrometer to obtain corresponding sensing data.

In this embodiment, the modem demodulates the optical signal through a transparent window power detection method or a dual-wavelength difference demodulation method; the optical signal emitted by the optical signal transmitter is a continuous spectrum laser light source with a wavelength of 800nm to 1800nm.

In this embodiment, the sensing device further includes a fiber laser, an optical signal transmitter connected to the fiber laser, so that the incident light of the emitted light signal is sent to the fiber laser for laser oscillation output.

Through the above technical solution, the sensing structure provided by the embodiment of the present invention, that is, the sensing structure produced by coupling and inducing transparency of the optical fiber resonator combining the advantages of the microring resonator and the F-P cavity structure, is used to detect The impact of external micro-displacement/micro-stress has high sensitivity. In particular, this technology uses an optical resonant cavity and another optical resonant cavity to achieve a symmetrical coupling condition, and uses the induced transparency effect to further improve the micro sensor while reducing the volume of the optical sensor while achieving the same sensing performance. The measurement accuracy of displacement/micro-stress can realize the miniaturization of optical sensor and integrated sensing system. This optical sensing technology can be used not only to evaluate the working accuracy and judgment error of components during mechanical manufacturing, but also to measure the pressure of deep sea water. It has a series of advantages such as standardized manufacturing process, easy integration, high sensing accuracy and wide application range. .

Other features and advantages of the embodiments of the present invention will be described in detail in the following part of specific embodiments.

Description of drawings

The accompanying drawings are used to provide a further understanding of the embodiments of the utility model, and constitute a part of the description, and are used together with the following specific embodiments to explain the embodiments of the utility model, but do not constitute a limitation to the embodiments of the utility model. In the attached picture:

Fig. 1 schematically shows a schematic structural diagram of a sensing structure provided according to an embodiment of the present invention;

Fig. 2 schematically shows a flow chart of the manufacturing process of the sensing structure provided according to the embodiment of the present invention;

Fig. 3 schematically shows a schematic structural diagram of a sensing unit provided according to an embodiment of the present invention;

Fig. 4 schematically shows the connection topology diagram of the sensing system provided according to the embodiment of the present invention; and

Fig. 5 schematically shows a schematic diagram of the output transmittance curve of the sensing structure provided by the embodiment of the present invention.

Explanation of reference signs

100. Sensing structure; 1. Input straight waveguide;

2. The first resonant cavity; 3. The second resonant cavity;

4. Output straight waveguide; 10. Optical fiber;

101. Optical fiber sensing unit; 201. Optical signal transmitter;

202. Optical isolator; 203. Photoelectric converter;

204. Spectrometer; 205. Data analysis system.

Detailed ways

The specific implementation manners of the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation manners described here are only used to illustrate and explain the embodiments of the present utility model, and are not intended to limit the embodiments of the present utility model.

The specific implementation manners of the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation manners described here are only used to illustrate and explain the embodiments of the present utility model, and are not intended to limit the embodiments of the present utility model.

It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present utility model are only used to explain the relationship between the components in a certain posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

In addition, the descriptions related to "first", "second" and so on in the present application are only for the purpose of description, and should not be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In addition, the meaning of "or" appearing in the whole text includes three parallel schemes, taking "A or B" as an example, including scheme A, scheme B, or schemes satisfying both A and B. In addition, the technical solutions of the various embodiments can be combined with each other, but it must be based on the realization of those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist , also not within the scope of protection required by the utility model.

[Example 1]: a general utility model design and principle of a sensing structure.

Referring to Fig. 1, Embodiment 1 of the present utility model firstly provides a sensing structure 100, and the sensing structure 100 sequentially includes along the optical path: an input straight waveguide 1, a first resonant cavity 2, a second resonant cavity 3 and an output straight waveguide 4, wherein both the input straight waveguide 1 and the output straight waveguide 4 are arranged in parallel optical fibers 10, so as to reduce the spatial distance between the input straight waveguide 1 and the output straight waveguide 4, and realize the compactness of the sensing structure 100.

In some embodiments, the input straight waveguide 1 and the output straight waveguide 4 can be realized by other means, and the only limitation is that the optical signal propagates stably and straightly in the input straight waveguide 1 and the output straight waveguide 4 .

In this embodiment, the first resonant cavity 2 and the second resonant cavity 3 are arranged between the input straight waveguide 1 and the output straight waveguide 4, and the second resonant cavity 3 can be a silicon-based ring resonant cavity, which can be made of SOI material (SOI Material: the abbreviation of the new silicon-based integrated circuit material) is the base material, on which a ring with a radius of nanometer is drawn, usually the bottom is the straight waveguide called in the embodiment of the utility model, and the optical signal passes through the air from the position close to the ring The gap coupling enters the waveguide ring, and the light wave with a wavelength that satisfies the resonance condition resonates in the ring, and propagates in the ring repeatedly, while the light that does not generate resonance is coupled into the straight waveguide through the air gap to complete the transmission. On the other hand, the first resonator 2 can be an F-P cavity structure (F-P cavity structure: Fabry-Perot resonator), which is a passive optical resonator, usually composed of two sheets with preset reflectivity Composed of parallel plates, that is, a plane-parallel cavity, a ray parallel to the axis of the resonant cavity, after being reflected by a parallel plane mirror, propagates in a direction parallel to the axis, and never exits the cavity.

Further, the sensing structure 100 provided by the embodiment of the present utility model will be based on cascading the microring resonant cavity 3 (the same as the second resonant cavity 3 above, the same below) to the F-P cavity structure 2 (same as the first resonant cavity mentioned above). resonant cavity 2, the same below), so that the microring resonant cavity 3 and the F-P cavity structure 2 are optically coupled in the waveguide coupling area A and the waveguide coupling area B, and the optical signal is freely transmitted in the optical fiber 10 in the sensing structure 100 Conduction, and through the coupling structure, the sensing structure 100 has the characteristics of high precision and low volume.

Specifically, the optical coupling can be realized by using technologies such as interface matching and structural docking, so as to meet the requirement of free transmission of optical signals between two optical resonators (referring to the first resonator 2 and the second resonator 3).

Among them, the material and construction structure of the base material are common technical means for those skilled in the art, and the embodiment of the utility model does not focus on this, so it will not be elaborated here.

The above scheme can form optical resonant cavities with different free spectral ranges and are connected to each other by optical coupling to form a vernier effect, so as to detect the influence of external substances on the optical signal, and the above scheme can save costs and reduce the cost of the sensing structure 100 Advantage.

Then based on the above technical solutions, how to continue to use the transparent induction sensing technology to realize the sensing structure 1 to further increase the sensing accuracy, so as to improve the measurement accuracy can be used for micro-displacement/micro-stress, which can be used as the direction of improvement of the existing technology.

Therefore, the embodiment of the present invention provides a sensing structure 100 , and the present invention will describe the structure involved in the embodiment of the present invention. Because in the theory of optical waveguide, the propagation of light in the waveguide is based on the principle of total emission of light, in the expected effect of the embodiment of the present utility model, the optical signal first passes through the F-P cavity structure 2, and then enters the microring resonant cavity through a coupling 3, and then output from the microring resonator 3 to complete a complete conduction. In short, in the overall utility model concept provided by the embodiment of the present utility model, the F-P cavity structure 2 and the microring resonant cavity 3 in the sensing structure 100 will produce reflection and projection under the irradiation of light . As long as the F-P cavity structure 2 and the microring resonator 3 are designed as a unique structure, a part of light can be transmitted, but because the F-P cavity structure 2 and the microring resonator 3 have different transmission conditions for different optical signals, or for The absorption of different optical signals is different. An optical signal of a certain frequency cannot be transmitted at all, or is completely absorbed, and the light causes the material to resonate. At this time, other light is not absorbed at all, or all of it is transmitted through, and the induced transparency can be realized, thereby completely retaining the optical signal and improving the measurement accuracy.

In order to realize the above utility model concept, the embodiment of the utility model provides one of the solutions: continue to refer to FIG. 1, fix the position of the microring resonator 3, that is, ensure that the position of the microring resonator 3 does not change under the external environment (such as external force) , the width of the F-P cavity structure 2 is equal to the waveguide width of the input straight waveguide 1, the end of the F-P cavity structure 2 is provided with a corrugated diaphragm (fine parts, not shown in the figure) as an elastic sensitive element, when the two sides of the diaphragm are subjected to different When the pressure (or force) acts on the diaphragm, the diaphragm moves to the side with low pressure, so that its center produces a displacement that has a certain relationship with the pressure difference. Similarly, the pressure displacement characteristics of the corrugated diaphragm affect the static and dynamic performance of the pneumatic pressure valve. It has a great influence, among which the thickness of the corrugated diaphragm, the material of the sandwich core, the hardness of the rubber and other factors. The details are set according to the required degree of precision.

The longitudinal central axis of the F-P cavity structure 2 is in the plane where the microring resonator 3 is located, and the transverse central axis of the microring resonator 3 is symmetrical to the symmetry axis of the F-P cavity structure 2, and the microring resonator 3 and the F-P cavity structure 2 are optically coupled connected to be used for the free conduction of the optical signal in the microring resonator 3 and the F-P cavity structure 2, the optical signal undergoes interference coupling inside the optical fiber 10 through the F-P cavity structure 2, and enters the microring resonator 3 through the coupling region waveguide for two Secondary coupling, interference coupling and secondary coupling are regarded as two kinds of excited states;

In the case of a symmetric structure, the two excited states interact to form a spectrum;

Under external influence, the corrugated diaphragm of the F-P cavity structure 2 contacts the external force, so that the F-P cavity structure 2 and the micro-ring resonator 3 break the symmetrical position and become an asymmetric structure. The excited state excites two modes of optical signals through the asymmetric structure, and the interaction between the two modes splits the spectrum into two forbidden bands, and presents a transparent window between the two forbidden bands; thus using the induced transparency effect, Under the condition of achieving the same sensing performance, the volume of the optical sensor can be reduced while further improving the measurement accuracy of the micro-displacement/micro-stress, and the miniaturization of the optical sensor and the integrated sensing system can be realized.

In the same way, as long as the F-P cavity structure 2 and the microring resonator 3 are arranged in a reasonable manner according to the above-mentioned structure, the advantages of both the F-P cavity structure 2 and the microring resonator 3 can be realized, and due to the arrangement , the volume of the microring resonant cavity 3 itself is small, which can realize the miniaturization of the volume of the sensing structure 100 .

Further, with reference to the schematic structural diagram of the sensing structure 100 based on optical fiber coupling-induced transparency shown in Figure 1; through the cascade F-P cavity structure 2 of the microring resonator cavity 3, the sensing structure 100 is also provided with a waveguide coupling region A and a waveguide coupling Area B, waveguide coupling area A and waveguide coupling area B are arranged at the laterally symmetrical ends of microring resonator 3; waveguide coupling area A is used for optical coupling between microring resonator 3 and F-P cavity structure 2, and waveguide coupling area A can It is the interface between the microring resonator 3 and the F-P cavity structure 2. Similarly, the waveguide coupling region B can be the interface between the output straight waveguide 4 and the microring resonator 3, so as to be used for optical signals in the sensing structure 100 free conduction.

Wherein, the optical fiber includes at least one of the following: single-mode optical fiber, multi-mode optical fiber, photonic crystal optical fiber, and nano-fiber.

It can be understood that when affected by external factors, that is, under the sensing state of the sensor, such as when the pressure sensor is under pressure and the water level sensor is immersed in water, the microring resonant cavity 3 and the F-P cavity structure 2 will form an asymmetry due to environmental factors structure, and the two excited states excite two modes of light through the asymmetric structure, the coupling between the two modes performs the excitation, and at the same time the interaction between the two modes makes the absorption spectra of the two states Splitting into two absorption spectra, a low-loss highly transparent window will appear between the two absorption spectra.

Furthermore, the microring resonator 3 is formed by a ring waveguide, the F-P cavity structure 2 is input by a straight waveguide, and when the optical signal is input from the straight waveguide, it is vertically incident on the F-P cavity structure. Specifically, the F-P cavity structure 2 can be connected to the input straight waveguide fiber (single-mode fiber), and the F-P cavity structure (that is, the F-P cavity structure 2) is composed of the flat end surface of the fiber plug and the inner surface of the corrugated diaphragm.

Wherein, the medium between the microring resonator 3 and the F-P cavity structure 2 can be air or other gaseous medium; the F-P cavity structure 2 is connected with the input straight waveguide fiber 1 (single-mode fiber), and the F-P cavity structure 2 is formed by the flattening of the fiber plug. The end face is formed with the inner surface of the corrugated diaphragm.

Referring to FIG. 2, according to the above description, a manufacturing process for the sensing structure is also provided in Embodiment 1, wherein the manufacturing process may include the following steps:

Step S101, setting a microring resonant cavity at a fixed position on the substrate;

Step S102, selecting a single-mode optical fiber, stripping off the coating layer from one end of the single-mode optical fiber, and wiping the optical fiber with alcohol;

Step S103, use a cutting knife to cut the end of the stripped coating layer flat to form a flat end surface, and groove the F-P cavity structure on the flat end surface, wherein the longitudinal central axis of the F-P cavity structure is on the plane where the micro-ring resonator is located, and the micro-ring The transverse central axis of the resonant cavity is symmetrical to the symmetrical axis of the F-P cavity structure;

Step S104, the microring resonator and the F-P cavity structure are optically coupled and connected by structural docking and interface matching.

It can be understood that the base material, that is, the base material, can be the SOI material mentioned above, and the microring resonator 3 can be processed on the base material in a manner of drawing or etching, and the F-P cavity structure 2 can choose the treatment method of flat end surface In order to strip one end of the single-mode optical fiber 10 (a choice of optical fiber) from the coating, wipe the optical fiber clean with alcohol, and cut the end of the stripped coating flat with a cutting knife; the above-mentioned reasons for preferably using the corrugated diaphragm Under the same pressure, the deformation is greater than that of the non-corrugated diaphragm, which amplifies the pressure change, improves the sensitivity and enhances the anti-pressure effect of seawater.

After the optical signal is vertically incident on the optical fiber 10, part of the light is reflected by the end face of the optical fiber, and the other part of the light passes through the F-P cavity structure 2 and is reflected by the lower surface of the corrugated diaphragm. The two beams of light interfere inside the optical fiber to obtain the reflection spectrum of the light.

Subsequently, the microring resonator 3 and the F-P cavity structure 2 are optically coupled and connected by structural docking and interface matching.

The terms "corrugated diaphragm" and "single-mode optical fiber" appearing above are technologies known to those skilled in the art, and this feature will not be elaborated here. It should be noted that the above process of flattening the end surface and the The selection is obtained by intellectual labor required by those skilled in the art during the experiment, and therefore should belong to the scope of protection covered by the embodiments of the present invention.

It can be understood that since the microring resonator 3 and the F-P cavity structure 2 in the input straight waveguide are symmetrically arranged, the two are optically coupled to realize optical information transmission between the microring resonator 3 and the input straight waveguide; at the same time, the microring resonator The resonant cavity 3 and the F-P cavity structure 2 are both optical resonant cavities, both of which have the function of frequency selection. The above two optical resonant cavities have different free spectral ranges, and the microring resonant cavity 3 and the F-P cavity structure 2 correspond to The spacing between adjacent resonant wavelengths is different. The purpose is that when the two optical resonant cavities are coupled and connected, the sensing range can be increased and the measurement accuracy of the sensor can be improved by means of the vernier effect. And the two are coupled separately, because the coupling modes of the two optical resonators meet the phase matching, thereby realizing the inter-mode coupling; the microring resonator 3 and the F-P cavity structure 2 are coupled and connected through the coupling region 12, thereby realizing the direct output The coupling between the waveguide and the microring resonator 3 conducts optical information.

The above-mentioned "optical coupling" connection refers to the realization of two optical resonators, that is, the microring resonator 3 and the F-P cavity structure 2, to meet the requirements of free transmission of optical signals between the two through interface matching and structural docking. . When the optical signal is input from the straight waveguide, it is vertically incident on the F-P cavity structure 2, a part of the light is reflected by the smooth end face of the fiber, and the other part passes through the F-P cavity structure and is reflected by the corrugated diaphragm. The two beams of light are interfered and coupled inside the fiber; The waveguide through the coupling region 12 enters the microring resonant cavity 3, and the coupling is performed in the cavity, and then the optical signal is output from the output straight waveguide through the waveguide through the coupling region 12. The two coupling processes can be regarded as a kind of excited state. Under the symmetric structure, the two excited states interact with each other to form an absorption spectrum.

When affected by external factors, the wave-shaped diaphragm changes, resulting in a corresponding change in the F-P cavity structure 2, the symmetrical structure is destroyed, and the two excited states excited by the straight waveguide excite two modes of light through the asymmetric structure, The coupling between the two modes is excited, and at the same time, the interaction between the two modes splits the absorption spectrum into two absorption spectra, and a low-loss high-transparency window will appear between the two absorption spectra. In the transparent window, the transparent valley is gradually split into two, and the wavelength of the two split valleys is compared with the single transparent valley of the symmetrical structure without the influence of external factors, which can vividly reflect the structural deformation of the F-P cavity structure 2 , that is, the deformation of the corrugated diaphragm. This highly transparent window phenomenon is achieved by fiber coupling induced transparency technology.

As the pressure increases, the asymmetry of the FP cavity also increases, and the transparent window gradually widens. The wavelength of the forbidden band on both sides of the window is compared with the single peak of the symmetrical structure without the influence of external factors, which can vividly reflect the structure of the FP cavity. The structural deformation, that is, the optical fiber coupling-induced transparency effect when the corrugated diaphragm is deformed, achieves high-sensitivity measurement under the tiny size of the device.

In summary, through the above method, the sensing structure 100 produced by combining the advantages of the microring resonator and the F-P cavity structure by coupling the optical fiber resonator to induce transparency is used to detect the influence of external micro-displacement/micro-stress, Has a high sensitivity. In particular, this technology uses an optical resonant cavity and another optical resonant cavity to achieve a symmetrical coupling condition, and uses the induced transparency effect to further improve the micro sensor while reducing the volume of the optical sensor while achieving the same sensing performance. The measurement accuracy of displacement/micro-stress can realize the miniaturization of optical sensor and integrated sensing system. This optical sensing technology can be used not only to evaluate the working accuracy and judgment error of components during mechanical manufacturing, but also to measure the pressure of deep sea water. It has a series of characteristics such as standardized manufacturing process, easy integration, high sensing accuracy and wide application range. .

[Embodiment 2]: An optical fiber sensing unit 101 applied to ocean depth pressure.

Based on the above concept of the utility model, the following embodiments of the utility model also provide a specific optical fiber sensing unit 101, which is applied to pressure sensing. It can be understood that pressure sensing is the most commonly used type in industrial practice. Widely used in various industrial automatic control environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, production automatic control, aerospace, military industry, petrochemical, oil wells, electric power, ships, machine tools, pipelines and many other industries. Below in conjunction with specific application (ocean depth pressure sensing) the embodiment of the utility model is described in further detail (based on the utility model embodiment above, this embodiment is not shown):

Please refer to Fig. 2, the optical fiber sensing unit 101 provided in the embodiment of the utility model includes the above-mentioned sensing structure 100, and the sensing structure 100 is encapsulated in the optical fiber sensing unit 101, wherein the optical fiber of the sensing structure 100 can optionally Adopt single-mode optical fiber, the structural characteristics of two optical resonant cavities that above-mentioned embodiment provides, i.e. the structural characteristic arrangement of microring resonant cavity 3 and F-P cavity structure 2, in application, need the length of F-P cavity structure 2 and micro The diameter of the ring resonator 3 should be matched according to the principle of optical coupling, and the width of the F-P cavity structure 2 should be strictly equal to the width of the input straight waveguide 1 .

For the selection of the corrugated diaphragm on the F-P cavity structure 2, considering the Young's modulus and Poisson's ratio of various materials and other related factors, the preferred material is 316L stainless steel, whose Young's modulus is 200GPa, and Poisson's ratio is 0.3, and it is suitable for small pressure measurement of corrosive and viscous media. After the CoventorWare software simulation experiment, it is finally determined that the thickness of the corrugated diaphragm is 30 μm, the wave height is 60 μm, and the corrugation width is 750 μm. At this time, when a pressure of 0.1 MPa is applied to the diaphragm, the deflection of the corrugated membrane is 55 μm.

Through the principle of optical fiber coupling to induce transparency, combined with the absorption spectrum splitting and transparency phenomenon of the coupling phenomenon of two optical resonators, using the calculation relationship between the center disturbance and pressure of the corrugated diaphragm, the conversion relationship between seawater depth and seawater pressure, and the two transparent valleys of the absorption spectrum The calculation relationship between the wavelength position distance and the deformation of the corrugated diaphragm realizes high-precision ocean depth measurement under the tiny size of the device. According to calculations, this structure ideally increases the measurement sensitivity to 3108.12μm/MPa, which is much higher than the measurement sensitivity of a single diaphragm optical fiber Fabry-Perot pressure sensor; the minimum change range that can be measured is ±0.013m, which is much higher Compared with the measurement accuracy of traditional CTD technology.

The sensing device provided by the embodiment of the utility model is to use the optical fiber resonant cavity coupling to induce the sensitivity of the transparency to the asymmetric structure, so that the pressure sensing measurement is more accurate. In addition, the pressure sensor made based on the micro-displacement sensing technology based on optical fiber double resonant cavity coupling-induced transparency has good hysteresis and repeatability; it is resistant to harsh environments, anti-electromagnetic interference, and has low temperature cross-sensitivity; full-scale cavity length changes Small measurement error, stable work, good linearity; simple manufacturing process, convenient material acquisition, small size, low cost, suitable for mass production.

[Embodiment 3]: a specific sensing system.

In order to obtain the parameters described in Embodiment 2, a specific sensing system 200 is also provided below in the embodiment of the present invention; the sensing system 200 first includes the above optical fiber sensing unit 101, and may also include: an optical signal transmitter 201 , optical isolator 202, photoelectric converter 203, modem (not shown), and spectrometer 204 and data analysis system 205;

Wherein, the optical signal transmitter 201 can be a broadband light source, which is configured so that the incident light of the broadband light source is sent to the optical isolator 202, and the output end of the optical isolator 202 is connected to the input end of the optical fiber sensing unit 101 through the photoelectric converter 203, To limit the direction of the optical signal and perform sensing through the optical fiber sensing unit 101, the output light of the optical fiber sensing unit 101 enters the spectrometer through the photoelectric converter 203, the modem is electrically connected to the spectrometer 205, and the data is analyzed by the spectrometer 205 to Get the corresponding sensor data.

In some embodiments, it can be connected to an optical isolator through a fiber laser (not shown), the output end of the optical isolator 202 is connected to the input end of the optical fiber sensing unit 101 through a photoelectric converter 203, and the optical fiber sensing unit 101 The output end is connected to a modem (not shown in the figure) through the photoelectric converter 203, and the modem is electrically connected to the spectrometer. Wherein, the optical signal transmitter is connected with the fiber laser to transmit the incident light of the optical signal to the fiber laser for laser oscillation output.

Referring to FIG. 4, FIG. 4 schematically shows a schematic diagram of the output transmittance curve of the sensing structure according to an embodiment of the present invention, and analyzes the output transmittance curve of the sensing structure according to the wavelength of the optical signal, To determine a reasonable wavelength.

Further, if there is a modem, the modem can demodulate the optical signal through a transparent window power detection method or a dual-wavelength difference demodulation method. For the demodulation scheme, the small-range displacement/stress can be detected through the transparent window power detection method, and the large-range displacement/stress can be demodulated through the dual-wavelength difference method.

Further, the optical signal emitted by the optical signal transmitter is a continuous spectrum laser light source with a wavelength of 800-1800 nm.

To sum up, the embodiment of the present utility model is based on the above sensing structure, the sensing structure is packaged, and combined with other sensing periods, a pressure sensing system can be derived for the pressure sensing unit For verification, the device combines original optical signal transmitters, fiber lasers, optical isolators, photoelectric converters, modems, and spectrometers on the basis of sensors. In order to adapt to the unique characteristics and configuration of sensors in Embodiment 2 The modem demodulates the optical signal through a transparent window power detection method or a dual-wavelength difference demodulation method, and the optical signal emitted by the optical signal transmitter is limited to a continuum laser light source with a wavelength of 800-1800nm. The pressure sensing device may not be limited in size and outline, and only needs to utilize the corresponding elements of the sensing element to realize the same or similar functions, and all of them shall also fall within the protection scope of the present invention.

Those skilled in the art should also understand that if the sensing structure or sensor provided by the utility model is simply changed, the functions added in the above-mentioned method are combined, or replaced on the device, such as the model materials of each component Replacement, replacement of the use environment, simple replacement of the positional relationship of each component, etc.; or the product formed by it is integrated; or detachable design; where the combined components can form a method/equipment/device with specific functions, use Such method/equipment/device can replace the method and device of the present utility model and all fall within the protection scope of the present utility model.

It should also be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes Other elements not expressly listed, or elements inherent in the process, method, commodity, or apparatus are also included. Without further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

The above are only examples of the present application, and are not intended to limit the present application. For those skilled in the art, various modifications and changes may occur in this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims (10)

1. A transparent sensing structure based on optical fiber coupling, characterized in that, the sensing structure comprises a multi-section optical fiber, comprising an output straight waveguide, an input straight waveguide on the optical fiber, and the output straight waveguide, the input straight waveguide A first resonant cavity and a second resonant cavity are also included between them; the distance between adjacent resonant wavelengths corresponding to the first resonant cavity and the second resonant cavity is different, so that the first resonant cavity and the second resonant cavity The cavities all have a frequency selection effect and have different free spectral ranges; the first resonant cavity includes a ring waveguide, and the first resonant cavity is cascaded with the second resonant cavity segment in the input straight waveguide to optically couple to realize Optical information conduction between the input straight waveguide and the first resonant cavity; the first resonant cavity is a micro-ring resonant cavity, the second resonant cavity is an F-P cavity structure, and the micro-ring resonant cavity and the F-P The optical coupling connection of the cavity structure is used for the free transmission of optical signals in the microring resonant cavity and the F-P cavity structure, and the optical signal undergoes interference coupling inside the optical fiber through the F-P cavity structure, and enters the micro-ring through the coupling region waveguide. The secondary coupling is carried out in the ring resonator. 2. The sensing structure based on optical fiber coupling induced transparency according to claim 1, wherein the position of the microring resonator is fixed, the width of the F-P cavity structure is equal to the width of the input straight waveguide, and the F-P A corrugated diaphragm is arranged at the end of the cavity structure. 3. the transparent sensing structure based on optical fiber coupling according to claim 2, wherein the longitudinal central axis of the F-P cavity structure is at the plane where the micro-ring resonator is located, and the micro-ring resonator of the micro-ring resonator The transverse central axis is symmetrical to the axis of symmetry of the F-P cavity structure. 4. The sensing structure based on optical fiber coupling-induced transparency according to claim 3, wherein the interference coupling and the secondary coupling are regarded as two excited states of a class; In the case of a symmetrical structure, two said excited states interact to form a spectrum; Under external influence, the structure of the microring resonator and the F-P cavity changes from a symmetrical position to an asymmetric structure, and the two excitation states of the microring resonator and the F-P cavity structure excite two modes of light through the asymmetric structure signal, the interaction between these two modes splits the spectrum into two forbidden bands and presents a transparent window between the two forbidden bands. 5 . The sensing structure based on optical fiber coupling induced transparency according to claim 3 , wherein when the optical signal is input from the input straight waveguide, it is vertically incident on the second resonant cavity. 6. the transparent sensing structure based on optical fiber coupling according to claim 3, is characterized in that, the medium between the microring cavity and the F-P cavity structure is air, and the F-P cavity structure and the The input straight waveguide is connected, and the F-P cavity structure is composed of the flat end surface of the optical fiber plug and the inner surface of the corrugated diaphragm. 7. The sensing structure based on optical fiber coupling-induced transparency according to any one of claims 1 to 6, wherein the optical fiber comprises at least one of the following: single-mode optical fiber, multi-mode optical fiber, photonic crystal optical fiber, nano optical fiber. 8. A sensing device, which is applied to pressure sensing, is characterized in that it comprises a sensing structure based on optical fiber coupling-induced transparency as described in any one of claims 1 to 7 above, and the sensing structure is encapsulated in an optical fiber Sensing unit, described sensing device also comprises: Optical signal transmitters, optical isolators, photoelectric converters, spectrometers, modems and data analysis systems; Wherein, the optical signal transmitter outputs incident light, the direction of the incident light is limited by the optical isolator, and the output end is connected to the input end of the optical fiber sensing unit through the photoelectric converter, so as to The direction of the optical signal is limited and sensed by the optical fiber sensing unit, and then the output light of the optical fiber sensing unit enters the spectrometer through the photoelectric converter, and the modem is electrically connected to the spectrometer , analyzing the data by the spectrometer to obtain corresponding sensing data. 9. The sensing device according to claim 8, wherein the modem demodulates the optical signal through a transparent window power detection mode or a dual-wavelength difference demodulation mode; The optical signal is a continuous spectrum laser light source with a wavelength of 800nm to 1800nm. 10. The sensing device according to claim 8, characterized in that, the sensing device further comprises a fiber laser, and the optical signal transmitter is connected to the fiber laser so that the incidence of the optical signal transmitter Light to the fiber laser is output by laser oscillation.

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