Angle sensing system based on modulation micro-ring cavity and measurement method

Abstract

The invention relates to the technical field of optical sensing, in particular to an angle sensing system based on a modulation micro-ring cavity and a measuring method.The angle sensing system based on the modulation micro-ring cavity comprises a tunable laser, a photoelectric detector, a conical optical fiber waveguide, a polarization controller, the modulation micro-ring cavity, an angular displacement platform and a computer; the shape of the inner side wall of the columnar hollow ring is a modulated wave-shaped curved surface, and a notch H penetrating through the two ends of the columnar hollow ring is further formed in the side wall of the columnar hollow ring. According to the invention, the defect that an existing angle sensing system based on a microcavity coupling mode cannot realize full-range measurement of circumferential rotation of a cavity is overcome, and the circumferential symmetry of a traditional periodic microcavity is broken, so that a standing wave mode field in non-circumferential periodic distribution is formed in the microcavity; therefore, the full-range angle measurement of the circumferential rotation of the cavity is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical sensing technology, and more particularly to an angle sensing system and a measurement method based on a modulated micro-ring cavity. Background Art

[0002] Angle sensing systems are devices used to measure the angular changes of objects or systems, and are typically used to monitor and control the angular information of rotating or rotating objects. Existing, relatively mature and widely used angular displacement sensing devices include optical gratings, magnetic gratings, and capacitive gratings. These devices, with their high precision, high resolution, wide measurement range, ease of maintenance, and reliability, are widely used in fields such as photoelectric theodolites, aerospace equipment, and CNC machine tools. However, with the increasing demand for micro- and nanoscale manufacturing, traditional angular displacement measuring instruments (such as synchronous analyzers and potentiometers) lack the measurement accuracy of angle sensing systems based on microring cavities. An optical whispering gallery mode is an optical system that confines a light field to an extremely small spatial region. A microring cavity traps light within the cavity through total internal reflection, forming a resonant mode with advantages such as an extremely high quality factor (Q factor), a very small mode volume, and extremely high energy density. This type of microcavity significantly enhances the interaction between the light field and matter within the cavity, making it an excellent platform for ultra-sensitive optical sensing. The high Q and integrability of optical whispering gallery mode microcavities have shown great potential in sensor applications. To achieve angular displacement sensing, the microcavity light field can be made to interact with external matter in a resonant mode, causing the light field within the cavity to change. These changes can then be monitored to achieve angular displacement sensing.

[0003] At present, the traditional microcavity coupling method is that the waveguide is parallel to the surface of the microresonator. By adjusting the gap between the coupler and the microresonator, the evanescent wave on the waveguide surface can be effectively coupled into the microcavity to form a stable mode field. Existing research has found that by periodically modulating the structure of the microring cavity, the coupled resonant light wave can be split into a mode in the microcavity cavity to form a stable standing wave mode field. Based on the standing wave mode field, the angle sensing of the cavity can be realized. However, since the microcavity has good circular symmetry, the standing wave field in the cavity also shows corresponding symmetry. However, when the angle changes, the light field change law obtained by the current angle sensing system based on the microcavity coupling method shows periodic repetition. It can only realize small-range angle measurement under single-cycle rotation angle, and cannot directly realize full-range measurement of the circumferential rotation of the cavity. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiency that the existing angle sensing system based on the microcavity coupling method cannot achieve full-range measurement of the circumferential rotation of the cavity, and to provide an angle sensing system based on a modulated microring cavity and an angle measurement method thereof. The present invention breaks the circumferential symmetry of the traditional periodic microcavity, so that a standing wave mode field with a non-circumferential periodic distribution is formed in the microcavity. Since the field intensity formed by the modulated microring cavity at different angles is unique, it is ensured that when analyzing the spectrum and inversely solving the angle, the corresponding angle can be obtained, and there will be no repetition with the signals at other angles, realizing full-range angle measurement of the circumferential rotation of the cavity.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is:

[0006] An angle sensing system and measurement method based on a modulated microring cavity. It includes a tunable laser for generating light waves with a specific wavelength, a photodetector for receiving optical signals and converting them into electrical signals, and a tapered fiber waveguide located between the tunable laser and the photodetector and used for transmitting light waves;

[0007] It also includes a polarization controller located on the input side of the tapered fiber waveguide and used for adjusting the polarization state of the light wave;

[0008] It further includes a modulated microring cavity with one end of the cavity close to the tapered fiber waveguide, and an angular displacement platform connected to the other end of the modulated microring cavity. The modulated microring cavity and the tapered fiber waveguide are always in a critical coupling state;

[0009] It also includes a computer respectively connected to the tunable laser and the photodetector.

[0010] It should be noted that the computer can set the tunable laser to generate tunable-wavelength laser and input it into the tapered fiber waveguide; the polarization controller can adjust the polarization state of the optical wave and send it into the tapered fiber waveguide; the tapered fiber waveguide is close to the modulation microring cavity and is always in a critical coupling state with the modulation microring cavity. When light propagates in the tapered part of the tapered fiber waveguide, part of the optical field will leak to the outside to form an evanescent wave. In this way, part of the optical wave propagates in the tapered fiber waveguide, and part of it diffuses outward. The optical wave distributed outside the tapered fiber waveguide exists in the form of an evanescent field. The mode field of the modulation microring cavity will coincide with the evanescent field of the tapered fiber waveguide. The optical wave that satisfies the phase matching condition will generate a resonance phenomenon in the modulation microring cavity, and the optical wave that does not satisfy the phase matching condition will return to the tapered fiber waveguide to continue propagating, forming a resonant optical wave signal; when the optical wave is coupled into the modulation microring cavity and is confined in the cavity, it will propagate around the axis in a spiral shape and reflect back to the original place at the turning point. Among them, the light rays that satisfy the phase condition will form a stable optical whispering gallery mode; the angular displacement platform is used to fix the modulation microring cavity and adjust the relative angular position of the modulation microring cavity, so that the modulation microring cavity generates an angular rotation; the photodetector is used to convert the received optical signal into an electrical signal and transmit it to the computer, and the computer is used to encode and process the electrical signal; since the optical wave coupled into the modulation microring cavity forms a stable mode field distribution, and the corresponding mode optical field intensity distributions are different at different angular positions, the corresponding angular position can be reversely judged according to the different optical field intensity distributions. In the modulation microring cavity of the present invention, a stable standing wave is formed, and the angle measurement during the angular rotation of the modulation microring cavity is realized, solving the problem that the output data in the single-cavity evanescent wave coupling structure cannot directly realize the angular measurement of the full range of circumferential rotation due to the symmetric distribution of the single-microcavity standing wave mode field.

[0011] Further, the modulation microring cavity is a columnar hollow ring with both ends penetrating, the inner side wall shape of the columnar hollow ring is a modulated wavy curved surface, and a notch H that penetrates both ends of the columnar hollow ring is also provided on the side wall of the columnar hollow ring.

[0012] Further, the wavy curved surface encloses to form a microcavity cavity, and the notch H makes the microcavity cavity form a standing wave mode field with a non-circumferential periodic distribution. [[ID=,8]]

[0013] It should be noted that in the existing microcavity angle measurement methods, usually two grating cavities are required to cooperate in the measurement. Its disadvantage is poor flexibility. Without one grating cavity, angle measurement cannot be carried out. The present invention uses a single modulated microring cavity for angle measurement. In this method, a missing hole H is fabricated in the cavity of the modulated microring cavity, breaking the circular symmetry of the traditional periodic microcavity cavity, so that a standing wave mode field with a non-circumferential periodic distribution is formed in the microcavity cavity. The method of the present invention is based on the standing wave resonance mode distributed in the microring cavity and the change law of the optical signal at the output end of the tapered fiber waveguide under the change of the angle of the rotating microring cavity. For a specific angle of the microcavity cavity, a unique transmission spectrum curve can be output, which is compared with the different change trends of the transmission spectrum with the angle when the modulated microring cavity rotates, and then the corresponding rotated angle can be judged. The advantage of this method is that the field intensity formed by the modulated microring cavity at different angles is unique, ensuring that the corresponding angle can be obtained when analyzing the spectrum and inversely solving the angle, and there will be no repetition with the signals at other angles. By comparing the changes in the transmittance spectra, full-range angle measurement of the circumferential rotation of the cavity can be achieved.

[0014] Furthermore, the modulated microring cavity can be fabricated by nano-lithography technology. The modulated microring cavity is small in volume, can be mass-produced, has low cost and is suitable for micro-structure measurement occasions.

[0015] Furthermore, the modulation radius of the wavy curved surface is:

[0016] r(φ) = r0 + αsin(Tφ),

[0017] where r(φ) is the modulation radius, φ is the modulation angle, T is the modulation period, r0 is the average radius of the hollow circle of the modulated microring cavity, and α is the modulation amplitude.

[0018] The inner side wall of the modulated microring cavity of the present invention is a wavy curved surface. The cooperation between the wavy curved surface and the missing hole H makes the microcavity cavity form a standing wave mode field with a non-circumferential periodic distribution. To make a stable standing wave mode field formed in the single-cavity modulated microring cavity, the inner diameter modulation of its inner side wall wavy curved surface is extremely important.

[0019] Furthermore, the range of the modulation amplitude α is 0.18μm - 0.45μm. The inner side wall wavy curved surface of the modulated microring cavity of the present invention presents a sinusoidal curve fluctuation, and its modulation fluctuation amplitude is large. Only in this way can a stable standing wave mode field be formed in cooperation with the missing hole H.

[0020] Furthermore, the maximum radius R of the modulated microring cavity is greater than the sum of the modulation amplitude α and the average radius r0 of the hollow circle of the modulated microring cavity. Generally speaking, the maximum radius R can be an integer greater than the sum of the modulation amplitude α and the average radius r0 of the hollow circle of the modulated microring cavity, as long as there is a certain wall thickness to ensure the structural stability of the internal cavity.

[0021] Further, the center of the missing hole H is located on the circle where the average radius r0 of the hollow circle of the modulation micro-ring cavity lies.

[0022] Further, the diameter range of the missing hole H is 0.02 μm - 0.1 μm. The mode field distribution formed by the micro-cavity body without the missing hole is periodic. After adding the missing hole, the original mode field is destroyed to form a new non-circular symmetric mode field and is fixed. The field intensity formed by the modulation micro-ring cavity at different angles is unique, ensuring that the corresponding angle can be obtained when inversely solving the angle from the analysis spectrum, and there will be no repetition with the signals at other angles. By comparing the changes in the transmittance spectrum, the full-range angle measurement of the circumferential rotation of the cavity can be realized.

[0023] Further, the axis of the modulation micro-ring cavity is perpendicular to the axis of the tapered fiber waveguide, and the modulation micro-ring cavity is located in the tapered region of the tapered fiber waveguide. The distance between the modulation micro-ring cavity and the tapered fiber waveguide is 0.2 μm - 0.5 μm.

[0024] The present invention also discloses a measurement method for an angle sensing system based on a modulation micro-ring cavity, specifically including the following steps:

[0025] The computer controls a tunable laser to generate light waves of a specific wavelength. After the polarization state of the light waves is adjusted by a polarization controller, the light waves are input into the tapered fiber waveguide.

[0026] The light waves enter the large tapered fiber waveguide, and the light waves distributed outside the tapered fiber waveguide exist in the form of an evanescent field. When the light waves pass through the modulation micro-ring cavity arranged close to the tapered fiber waveguide, the mode field of the modulation micro-ring cavity coincides with the evanescent field of the tapered fiber waveguide. The light waves that meet the phase matching condition will generate a resonance phenomenon in the modulation micro-ring cavity to form resonance light wave signals, and the light waves that do not meet the phase matching condition will return to the tapered fiber waveguide to continue propagating.

[0027] After the light waves propagate to the photodetector, the photodetector converts the collected light wave signals into electrical signals and sends them to the computer for processing to obtain an output resonance spectrum.

[0028] When the angular displacement platform connected to the modulation micro-ring cavity rotates circumferentially, the modulation micro-ring cavity rotates in the same way, and the standing wave field in the modulation micro-ring cavity changes accordingly. The change in the coupling angle will cause a change in the resonance mode, thereby changing the output resonance spectrum. By collecting and processing the signals at the output end of the tapered fiber waveguide at different rotation angles of the angular displacement platform by the photodetector, when the modulation micro-ring cavity rotates by one angle, the light wave signals collected by the photodetector will change to a certain extent.

[0029] The computer processes the electrical signals transmitted by the photodetector, and thus n optical wave signals can be obtained. Each angle corresponds to a unique resonance spectrum diagram. By analyzing its resonance spectrum diagram, the angle measurement of the rotation of the modulation micro-ring cavity is realized.

[0030] Further, the method for angle measurement is to inversely solve the corresponding angle according to the resonance spectrum diagram.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] In the present invention, since the optical waves coupled into the modulation micro-ring cavity form a stable mode field distribution, and the mode optical field intensity distributions corresponding to different angular positions are different, the corresponding angular positions can be inversely judged according to the different optical field intensity distributions, solving the problem that in a single-cavity evanescent wave coupling structure, due to the symmetric distribution of the single micro-cavity standing wave mode field, the output data cannot directly realize the angle measurement of the full range of circumferential rotation.

[0033] The present invention uses a single modulation micro-ring cavity for angle measurement. In this method, a hole H is created in the cavity of the modulation micro-ring cavity, breaking the circumferential symmetry of the traditional periodic micro-cavity cavity, so that a standing wave mode field with a non-circumferential periodic distribution is formed in the micro-cavity cavity. The method of the present invention is based on the standing wave resonance mode distributed in the micro-ring cavity and the change law of the optical signal at the output end of the tapered fiber waveguide under the change of the angle of the rotating micro-ring cavity. For a specific angle of the micro-cavity cavity, a unique transmission spectrum curve can be output. By comparing with the different change trends of the transmission spectrum with the angle when the modulation micro-ring cavity rotates, the corresponding rotated angle can be judged. The advantage of this method is that the field intensity formed at different angles of the modulation micro-ring cavity is unique, ensuring that the corresponding angle can be obtained when analyzing the spectrum and inversely solving the angle, and there will be no repetition with the signals at other angles. By comparing the changes of the transmittance spectra, the angle measurement of the full range of circumferential rotation of the cavity can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural connection diagram of the angle sensing system in the present invention;

[0035] Figure 2 It is a partial cross-sectional schematic diagram of the modulation micro-ring cavity in the present invention;

[0036] Figure 3 It is a modulation function diagram of the wavy surface of the modulation micro-ring cavity in the present invention;

[0037] Figure 4 It is a schematic diagram of the coupling position between the tapered fiber waveguide and the modulation micro-ring cavity in the present invention (where a is a schematic diagram of coupling under light waves of a certain wavelength, and b is a schematic diagram of coupling under light waves of another wavelength);

[0038] Figure 5 Schematic diagram of the coupling position between the rotation of the modulation micro-ring cavity to a new angle and the conical fiber wave in the present invention (where c is the schematic diagram of coupling under light waves of a certain wavelength, and d is the schematic diagram of coupling under light waves of another wavelength);

[0039] Figure 6 Variation diagram of the transmission spectrum corresponding to the output of the conical fiber waveguide when the modulation micro-ring cavity rotates at different circumferential angles in the present invention.

[0040] The illustration markings are explained as follows:

[0041] 1 - Computer, 2 - Tunable laser, 3 - Polarization controller, 4 - Modulation micro-ring cavity, 5 - Photoelectric detector, 6 - Conical fiber waveguide, 7 - Angular displacement platform. Detailed implementation manners

[0042] The present invention will be further described below in conjunction with the detailed implementation manners. Among them, the attached drawings are only for illustrative purposes, showing only schematic diagrams rather than physical diagrams, and should not be construed as a limitation to this patent; in order to better illustrate the embodiments of the present invention, some components in the attached drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0043] In the attached drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating the orientation or position relationship, it is based on the orientation or position relationship shown in the attached drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so the terms describing the position relationship in the attached drawings are only for illustrative purposes and should not be construed as a limitation to this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] Embodiment 1

[0045] As Figure 1 shown in the first embodiment of the present invention, an angle sensing system based on a modulation micro-ring cavity includes a tunable laser 2 for generating light waves of a specific wavelength, a photoelectric detector 5 for receiving optical signals and converting them into electrical signals, and a conical fiber waveguide 6 located between the tunable laser 2 and the photoelectric detector 5 and used for transmitting light waves;

[0046] It further includes a polarization controller 3 located on the input side of the conical fiber waveguide 6 and used for adjusting the polarization state of light waves;

[0047] It also includes a modulation micro-ring cavity 7 with a cavity at one end close to the tapered fiber waveguide 6, and an angular displacement platform 4 connected to the other end of the modulation micro-ring cavity 7. The modulation micro-ring cavity 7 and the tapered fiber waveguide 6 are always in a critical coupling state;

[0048] It also includes a computer 1 respectively connected to the tunable laser 2 and the photodetector 5.

[0049] In this embodiment, a triangular chuck is used for fixing between the angular displacement platform 4 and the modulation micro-ring cavity 7.

[0050] It should be noted that the computer 1 can set the tunable laser 2 to generate a laser with a tunable wavelength and input it into the tapered fiber waveguide 6; the polarization controller 3 can adjust the polarization state of the light wave and send it into the tapered fiber waveguide 6; the tapered fiber waveguide 6 is close to the modulation micro-ring cavity 7 and is always in a critical coupling state with the modulation micro-ring cavity 7. When light propagates in the tapered part of the tapered fiber waveguide 6, part of the light field will leak to the outside to form an evanescent wave. In this way, part of the light wave propagates in the tapered fiber waveguide 6, and part of it diffuses outward and exists in the form of an evanescent field outside the tapered fiber waveguide 6. The mode field of the modulation micro-ring cavity 7 will coincide with the evanescent field of the tapered fiber waveguide 6, and the light wave that satisfies the phase matching condition will generate a resonance phenomenon in the modulation micro-ring cavity 7, and the light wave that does not satisfy the phase matching condition will return to the tapered fiber waveguide 6 to continue propagating, forming a resonant light wave signal; when the light wave is coupled into the modulation micro-ring cavity 7 and is confined in the cavity, it will propagate around the axis in a spiral shape and reflect back to the original place at the turning point, and the light rays that satisfy the phase condition will form a stable optical whispering gallery mode; the angular displacement platform 4 is used to fix the modulation micro-ring cavity 7 and adjust the relative angular position of the modulation micro-ring cavity 7, so that the modulation micro-ring cavity 7 generates an angular rotation; the photodetector 5 is used to convert the received optical signal into an electrical signal and transmit it to the computer 1, and the computer 1 is used to encode and process the electrical signal; since the light wave coupled into the modulation micro-ring cavity 7 forms a stable mode field distribution, and the corresponding mode light field intensity distributions are different at different angular positions, the corresponding angular position can be reversely judged according to the different light field intensity distributions. In the modulation micro-ring cavity 7 of the present invention, a stable standing wave is formed, and the angle measurement during the angular rotation of the modulation micro-ring cavity 7 is realized, solving the problem that the output data in the single-cavity evanescent wave coupling structure cannot directly realize the angular measurement of the full range of circumferential rotation due to the symmetric distribution of the single micro-cavity standing wave mode field.

[0051] As Figure 2 and Figure 3 shown, the modulation micro-ring cavity 7 is a columnar hollow ring with both ends penetrating. The inner side wall shape of the columnar hollow ring is a modulated wavy curved surface, and a notch H penetrating both ends of the columnar hollow ring is also provided on the side wall of the columnar hollow ring.

[0052] In this embodiment, a wavy curved surface encloses to form a microcavity cavity, and the missing hole H enables the microcavity cavity to form a standing wave mode field with non-circumferential periodic distribution.

[0053] It should be noted that in the existing microcavity angle measurement methods, usually two grating cavities are required to cooperate in the measurement. Its disadvantage is poor flexibility. Without one grating cavity, angle measurement cannot be carried out. The present invention uses a single modulation micro-ring cavity 7 for angle measurement. In this method, a missing hole H is created in the cavity of the modulation micro-ring cavity 7, breaking the circumferential symmetry of the traditional periodic microcavity cavity, and enabling a standing wave mode field with non-circumferential periodic distribution to be formed in the microcavity cavity. The method of the present invention is based on the standing wave resonance mode distributed in the micro-ring cavity and the variation law of the optical signal at the output end of the tapered fiber waveguide 6 under the change of the rotation angle of the micro-ring cavity. For a specific angle of the microcavity cavity, a unique transmission spectrum curve can be output, which is contrasted with the different variation trends of the transmission spectrum with the angle when the modulation micro-ring cavity 7 rotates, and then the corresponding rotated angle can be judged. The advantage of this method is that the field intensity formed by the modulation micro-ring cavity 7 at different angles is unique, ensuring that the corresponding angle can be obtained when analyzing the spectrum and inversely solving the angle, and there will be no repetition with the signals at other angles. By comparing the changes in the transmittance spectra, full-range angle measurement of the circumferential rotation of the cavity can be realized.

[0054] In this embodiment, the modulation micro-ring cavity 7 can be fabricated by nano-lithography technology. The modulation micro-ring cavity 7 has a small volume, can be mass-produced, has a low cost, and is suitable for micro-structure measurement occasions.

[0055] Embodiment 2

[0056] This embodiment is similar to Embodiment 1, the difference is that:

[0057] In this embodiment, the operating wavelength of the tunable laser 2 is between 1090.0 nm and 1091.4 nm, and the line width is 300 kHz;

[0058] In this embodiment, the diameter of the coupling thin end of the tapered region of the tapered fiber waveguide 6 is 10 μm, which is obtained by pulling a single-mode fiber with a hydrogen-oxygen flame;

[0059] In this embodiment, the modulation radius of the wavy curved surface is:

[0060] r(φ) = r0 + αsin(Tφ),

[0061] where r(φ) is the modulation radius, φ is the modulation angle, T is the modulation period, r0 is the average radius of the hollow circle of the modulation micro-ring cavity 7, and α is the modulation amplitude.

[0062] In this embodiment, the radius of the hole H is 0.05 μm, the diameter is 0.1 μm; the maximum diameter R is 6 μm, the average radius of the modulation center circle in the modulation microring cavity is 5.6 μm, and the modulation period T is The modulation amplitude is 0.35 μm. According to the above data, a modulated wavy surface can be obtained.

[0063] like Figure 2 and Figure 3 As shown, the inner sidewall of the modulated micro-ring cavity 7 of the present invention is a wavy surface. The combination of the wavy surface and the hole H enables the micro-cavity to form a standing wave mode field with a non-circular periodic distribution. In order to form a stable standing wave mode field in the single-cavity modulated micro-ring cavity 7, it is very important to modulate the inner diameter of the wavy surface of the inner sidewall.

[0064] In this embodiment, the modulation amplitude α ranges from 0.18 μm to 0.45 μm. The inner sidewall wavy surface of the modulated micro-ring cavity 7 of the present invention presents sinusoidal fluctuations, and the modulation fluctuation amplitude is large, so that a stable standing wave mode field can be formed by combining with the hole H.

[0065] In this embodiment, the maximum radius R of the modulated micro-ring cavity 7 is greater than the sum of the modulation amplitude α and the average radius r0 of the hollow circle of the modulated micro-ring cavity 7, and the maximum diameter R is 6 μm. Generally speaking, the maximum radius R can be an integer greater than the sum of the modulation amplitude α and the average radius r0 of the hollow circle of the modulated micro-ring cavity 7, as long as a certain wall thickness is maintained to ensure structural stability of the internal cavity.

[0066] like Figure 2 As shown, the center of the hole H is located on the circle where the average radius r0 of the hollow circle of the modulation micro-ring cavity 7 is located.

[0067] In this embodiment, the axis of the modulation micro-ring cavity 7 is perpendicular to the axis of the tapered optical fiber waveguide 6, and the modulation micro-ring cavity 7 is located in the tapered region of the tapered optical fiber waveguide 6. The distance between the modulation micro-ring cavity 7 and the tapered optical fiber waveguide 6 is 0.3 μm. The purpose of maintaining the distance between the tapered optical fiber waveguide 6 and the modulation micro-ring cavity within this range is to minimize coupling loss, avoid over-coupling and under-coupling, and enhance the stability of the standing wave. When the distance between the modulation micro-ring cavity and the tapered optical fiber waveguide 6 is 0.3 μm, the evanescent wave coupling efficiency between the tapered optical fiber and the micro-ring cavity can be guaranteed to a certain extent, achieving a good coupling effect.

[0068] like Figure 4 The a and b in the figure show the mode field distribution when the tapered fiber waveguide 6 is coupled with the micro-ring cavity 7 at a certain angle. By changing the circumferential angular position of the micro-ring cavity 7 by changing the rotating angular displacement platform 4, the new mode field distribution is obtained as shown in FIG. Figure 5 As shown in Figures c and d, by comparing the mode field distribution before and after the rotation, it can be seen that the mode field distribution inside the microcavity rotates accordingly as the microring cavity rotates.

[0069] During system operation, laser light emitted from the tunable laser 2 enters the modulated micro-ring cavity 7 via the tapered fiber waveguide 6. Light waves that meet the resonance conditions couple into the modulated micro-ring cavity and form a stable standing wave within the cavity. When the angular displacement platform 4 drives the modulated micro-ring cavity 7 to angularly rotate, the light wave signal collected at the output end of the tapered fiber waveguide 6 changes. The collected light wave signal is processed by the photodetector 5, converted into an electrical signal, and input into the computer 1. The collected data is analyzed, processed, and plotted as a two-dimensional change curve. A data mapping relationship can be established between the probe's direction of rotation and the output signal. Based on this mapping relationship, the angle of the modulated micro-ring cavity 7 can be measured as it rotates along its circumferential direction.

[0070] The modulated micro-ring cavity 7 in this embodiment rotates circumferentially at a uniform angle at the circumferential position to obtain light wave signals at different angular positions. After signal processing, the following is obtained: Figure 5 The transmittance changes with wavelength at different angles as shown.

[0071] By changing the coupling angle between the micro-ring cavity and the tapered optical fiber, the transmission spectrum of the output light wave signal changes as the micro-ring cavity rotates. Figure 6 As can be seen from the transmittance variation curve, when the angular displacement platform 4 is rotated, the corresponding output signal curve also undergoes a corresponding phase shift or amplitude change. The two maximum transmittance peaks of the transmission spectrum curve show significant changes, and the amplitudes of the maximum transmittance peaks are significantly different. That is, after the modulated micro-ring cavity 7 is circumferentially rotated, the transmission spectrum curve changes accordingly with the change in the coupled micro-ring cavity angle. Therefore, based on the different transmittance spectra at different angles, the angle of the micro-cavity can be determined inversely through the transmission spectrum curve. That is, each transmission spectrum curve corresponds to a certain angle and does not completely overlap with the transmission spectrum curves at other angles. Therefore, the current angular position of the modulated micro-ring cavity can be determined based on the transmission spectrum curve.

[0072] The other structures and principles of this embodiment are the same as those of Example 1.

[0073] Example 3

[0074] The present invention also discloses an angle measurement method based on an angle sensing system with a modulated micro-ring cavity, which specifically includes the following steps:

[0075] Computer 1 controls the tunable laser 2 to generate a light wave of a specific wavelength. The light wave is input into the tapered optical fiber waveguide 6 after the polarization state of the light wave is adjusted by the polarization controller 3.

[0076] Light waves enter the large conical fiber optic waveguide 6. The light waves distributed outside the conical fiber optic waveguide 6 exist in the form of an evanescent field. When the light waves pass through the modulation micro-ring cavity 7 arranged close to the conical fiber optic waveguide 6, the mode field of the modulation micro-ring cavity 7 will coincide with the evanescent field of the conical fiber optic waveguide 6. The light waves that meet the phase matching condition will generate a resonance phenomenon in the modulation micro-ring cavity 7, forming a resonant light wave signal, and the light waves that do not meet the phase matching condition will return to the conical fiber optic waveguide 6 and continue to propagate;

[0077] After the light waves propagate to the photodetector 5, the photodetector 5 converts the collected light wave signal into an electrical signal and sends it to the computer 1 for processing to obtain the output resonance spectrum;

[0078] When the angular displacement platform 4 connected to the modulation micro-ring cavity 7 rotates circumferentially, the modulation micro-ring cavity 7 rotates in the same way, and the standing wave field in the modulation micro-ring cavity 7 also changes accordingly. The change in the coupling angle will cause a change in the resonance mode, thereby changing the output resonance spectrum. By collecting and processing the signals at the output end of the conical fiber optic waveguide 6 at different rotation angles of the angular displacement platform 4 by the photodetector 5, every time the modulation micro-ring cavity 7 rotates by an angle, the light wave signal collected by the photodetector 5 will change to a certain extent;

[0079] The computer 1 processes the electrical signals sent by the photodetector 5, and thus n light wave signals can be obtained. Each angle corresponds to a unique resonance spectrum. By analyzing its resonance spectrum, the measurement of the rotation angle of the modulation micro-ring cavity 7 is realized.

[0080] In this embodiment, the method for angle measurement is to inversely solve the corresponding angle according to the resonance spectrum.

[0081] In summary, the advantage of this embodiment is that by setting the rotation of the micro-ring cavity at different angles to couple with the conical waveguide, a stable standing wave with a phase deviation but the same number of modes is formed in the micro-cavity of the modulation micro-ring cavity 7. By collecting the output signal of the fiber optic waveguide to obtain the transmittance spectrum and combining the angle change for processing and analysis, the measurement of the rotation angle of the modulation micro-ring cavity 7 is realized, and the full-range rotation angle measurement is achieved.

[0082] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. An angle sensing system based on a modulated microring resonator, characterized in that, It includes a tunable laser (2) for generating light waves of a specific wavelength, a photodetector (5) for receiving an optical signal and converting it into an electrical signal, and a tapered fiber waveguide (6) located between the tunable laser (2) and the photodetector (5) and for transmitting light waves; It further includes a polarization controller (3) located on the input side of the tapered fiber waveguide (6) for adjusting the polarization state of the light wave; It further includes a modulation microring cavity (7) with a cavity at one end close to the tapered fiber waveguide (6), and an angular displacement platform (4) connected to the other end of the modulation microring cavity (7). The modulation microring cavity (7) and the tapered fiber waveguide (6) are always in a critically coupled state; the modulation microring cavity (7) is a columnar hollow ring with both ends penetrating. The inner sidewall shape of the columnar hollow ring is a modulated wavy surface. There is also a notch H penetrating both ends of the columnar hollow ring on the sidewall of the columnar hollow ring; It further includes a computer (1) respectively connected to the tunable laser (2) and the photodetector (5).

2. The angle sensing system based on a modulated microring cavity according to claim 1, wherein The wavy surface encloses to form a microcavity cavity, and the notch H makes the microcavity cavity form a standing wave mode field with non-circumferential periodic distribution.

3. The angle sensing system based on a modulated microring cavity according to claim 1, characterized in that, The modulation radius of the wavy surface is: r(φ) = r0 + αsin(Tφ), where r(φ) is the modulation radius, φ is the modulation angle, T is the modulation period, r0 is the average radius of the hollow circle of the modulation microring cavity (7), and α is the modulation amplitude.

4. The angle sensing system based on a modulated microring cavity according to claim 3, wherein The range of the modulation amplitude α is 0.18 μm - 0.45 μm.

5. The angle sensing system based on a modulated microring cavity according to claim 3, characterized in that, The maximum radius R of the modulation microring cavity (7) is greater than the sum of the modulation amplitude α and the average radius r0 of the hollow circle of the modulation microring cavity (7).

6. The angle sensing system based on a modulated microring cavity according to claim 3, wherein The center of the notch H is located on the circle where the average radius r0 of the hollow circle of the modulation microring cavity (7) is located.

7. The angle sensing system based on a modulated microring cavity according to claim 6, characterized in that, The diameter range of the notch H is 0.02 μm - 0.1 μm.

8. The angle sensing system based on a modulated microring cavity according to claim 1, wherein The axis of the modulation microring cavity (7) is perpendicular to the axis of the tapered fiber waveguide (6), and the modulation microring cavity (7) is located in the tapered region of the tapered fiber waveguide (6). The distance between the modulation microring cavity (7) and the tapered fiber waveguide (6) is 0.2 μm - 0.5 μm.

9. The measurement method of an angle sensing system based on a modulated microring cavity according to any one of claims 1-8, characterized in that, Specifically, it includes the following steps: The computer (1) controls the tunable laser (2) to generate light waves of a specific wavelength. After the polarization state of the light wave is adjusted by the polarization controller (3), the light wave is input into the tapered fiber waveguide (6); The light wave enters the large tapered fiber waveguide (6). The light wave distributed outside the tapered fiber waveguide (6) exists in the form of an evanescent field. When the light wave passes through the modulation microring cavity (7) arranged close to the tapered fiber waveguide (6), the mode field of the modulation microring cavity (7) and the evanescent field of the tapered fiber waveguide (6) will overlap. The light wave that satisfies the phase matching condition will generate a resonance phenomenon in the modulation microring cavity (7) to form a resonant light wave signal, and the light wave that does not satisfy the phase matching condition will return to the tapered fiber waveguide (6) and continue to propagate; After the light wave propagates to the photodetector (5), the photodetector (5) converts the collected light wave signal into an electrical signal and sends it to the computer (1) for processing to obtain an output resonance spectrum diagram; When the angular displacement platform (4) connected to the modulation micro-ring cavity (7) rotates circumferentially, the modulation micro-ring cavity (7) rotates accordingly, and the standing wave field in the modulation micro-ring cavity (7) also changes. The change in the coupling angle will cause a change in the resonance mode, thereby changing the output resonance spectrum diagram. By collecting and processing the signals at the output end of the tapered fiber waveguide (6) at different rotation angles of the angular displacement platform (4) through the photodetector (5), every time the modulation micro-ring cavity (7) rotates by an angle, the light wave signal collected by the photodetector (5) will change to a certain extent; The computer (1) processes the electrical signal transmitted by the photodetector (5), and n light wave signals can be obtained. Each angle corresponds to a unique resonance spectrum diagram. By analyzing its resonance spectrum diagram, the rotation angle of the modulation micro-ring cavity (7) can be measured.

10. The measurement method of an angle sensing system based on a modulated microring cavity according to claim 9, characterized in that, The method for angle measurement is to inversely solve the corresponding angle according to the resonance spectrum diagram.

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