A spiral fiber optic grating all-fiber optical path and angular rate sensor

Abstract

This invention discloses a spiral fiber grating all-fiber optical path, comprising a first 45° tilted fiber grating, a second 45° tilted fiber grating, a birefringent chirped spiral fiber grating, and an alkali metal gas cell. One end face of the birefringent chirped spiral fiber grating is connected to the alkali metal gas cell, one end face of the first 45° tilted fiber grating is connected to the other end face of the birefringent chirped spiral fiber grating, and one end face of the second 45° tilted fiber grating is connected to the alkali metal gas cell. The polarization direction of the first 45° tilted fiber grating is parallel to the major or minor axis of the birefringent chirped spiral fiber grating. This spiral fiber grating all-fiber optical path improves the integration of the angular rate sensor and realizes miniaturization of the angular rate sensor. This invention discloses an angular rate sensor including the above-described spiral fiber grating all-fiber optical path.

Description

Technical Field

[0001] This invention relates to angular rate sensor technology, and more particularly to a spiral fiber optic grating all-fiber optical path and angular rate sensor. Background Technology

[0002] As a core and sensitive component of inertial navigation systems, the gyroscope directly determines the accuracy of navigation and guidance systems and ground reconnaissance platforms, making it a crucial part of inertial navigation systems and stabilization platforms. Currently, the market mainly utilizes microelectromechanical gyroscopes, laser gyroscopes, and atomic gyroscopes to achieve high-precision autonomous navigation. However, these technologies have drawbacks such as high cost, large size, and poor resistance to electromagnetic interference, making mass production difficult and hindering continuous and reliable navigation in complex environments such as underground and underwater.

[0003] Atomic gyroscopes utilize the axis-fixed property of atomic spins to measure the angular velocity of a carrier. Currently, the pump optical path, alkali metal gas cell, and probe optical path of an atomic gyroscope are three separate components. Polarization of the atoms within the gas cell is typically achieved by adjusting the spatial optical path, thereby demodulating the rotational rate of the atomic gyroscope. However, such integrated systems are not only bulky but also susceptible to positional changes and external forces, resulting in relatively low detection accuracy. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention provides a spiral fiber optic grating all-fiber optical path that integrates the pump optical path, alkali metal gas chamber, and probe optical path onto an optical fiber, forming an all-fiber structure. This significantly improves the integration of the angular rate sensor, enabling miniaturization of the angular rate sensor. Furthermore, optical fibers possess advantages such as strong anti-electromagnetic interference capability, resistance to acid and alkali corrosion, electrical insulation, high measurement accuracy, high reliability, and long service life, giving them a significant competitive advantage even in harsh environments with strong electromagnetic interference.

[0005] The present invention provides an angular rate sensor, including the above-mentioned spiral fiber optic grating all-fiber optical path.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0007] A spiral fiber grating all-fiber optical path includes a first 45° tilted fiber grating, a second 45° tilted fiber grating, a birefringent chirped spiral fiber grating, and an alkali metal cell. One end face of the birefringent chirped spiral fiber grating is connected to the alkali metal cell, one end face of the first 45° tilted fiber grating is connected to the other end face of the birefringent chirped spiral fiber grating, and one end face of the second 45° tilted fiber grating is connected to the alkali metal cell. The polarization direction of the first 45° tilted fiber grating is parallel to the major axis or minor axis of the birefringent chirped spiral fiber grating.

[0008] Furthermore, the alkali metal gas chamber includes a first optical fiber, a second optical fiber, a third optical fiber, and an optical fiber bubble cavity. One end face of the first, second, and third optical fibers is respectively connected to the surface of the optical fiber bubble cavity. The other end face of the first optical fiber is connected to the birefringent chirped helical fiber grating, and the other end face of the second optical fiber is connected to the second 45° tilted fiber grating. The central axis of the second optical fiber coincides with the central axis of the third optical fiber, and the central axis of the first optical fiber is perpendicular to the central axes of the second and third optical fibers. The optical fiber bubble cavity is sealed and filled with at least alkali metal atoms and inert gas.

[0009] Furthermore, a first open vent is formed on one side of the first optical fiber, a second open vent is formed on one side of the second optical fiber, and a third open vent is formed on one side of the third optical fiber. The first open vent, the second open vent, and the third open vent are aligned and fused together to form the optical fiber bubble cavity.

[0010] Furthermore, the fiber optic bubble cavity is also filled with at least one of a buffer gas and a quenching gas for sealing.

[0011] Furthermore, the first optical fiber is a polarization-maintaining fiber, while the second and third optical fibers are single-mode fibers.

[0012] Furthermore, the birefringent chirped helical fiber grating is made of polarization-maintaining fiber, and the first 45° tilted fiber grating and the second 45° tilted fiber grating are made of single-mode fiber.

[0013] Furthermore, the birefringent chirped spiral fiber grating is fabricated using elliptical core fiber, so that the birefringent chirped spiral fiber grating forms an elliptical core chirped spiral fiber grating.

[0014] Furthermore, the fiber grating period of the birefringent chirped spiral fiber grating gradually decreases along the light transmission direction, and the minimum fiber grating period of the birefringent chirped spiral fiber grating is not less than the fiber grating period of the first 45° tilted fiber grating.

[0015] An angular rate sensor includes a pump source, a probe source, a magnetic field generator, an analysis and processing device, and the aforementioned spiral fiber grating all-fiber optical path. The pump source is connected to the other end face of a first 45° tilted fiber grating in the spiral fiber grating all-fiber optical path. The probe source is connected to the other end face of a second 45° tilted fiber grating in the spiral fiber grating all-fiber optical path. The analysis and processing device is connected to an alkali metal gas cell in the spiral fiber grating all-fiber optical path. The magnetic field generator is disposed outside the alkali metal gas cell in the spiral fiber grating all-fiber optical path.

[0016] Furthermore, the angular rate sensor also includes a non-magnetic heating box and a magnetic shielding box. The non-magnetic heating box is located outside the alkali metal gas chamber of the all-fiber optical path of the spiral fiber grating, and the magnetic shielding box is located outside the magnetic field generator.

[0017] The present invention has the following beneficial effects: The spiral fiber grating all-fiber optical path of the present invention uses the first 45° tilted fiber grating and the birefringent chirped spiral fiber grating as the pump optical path, and the second 45° tilted fiber grating as the detection optical path. The pump optical path, alkali metal gas cell and detection optical path of the angular rate sensor are integrated on the optical fiber to form an all-fiber structure, which greatly improves the integration of the angular rate sensor and realizes the miniaturization of the angular rate sensor. Moreover, the optical fiber has the advantages of strong anti-electromagnetic interference capability, acid and alkali corrosion resistance, electrical insulation, high measurement accuracy, high reliability and long service life. It also has a great competitive advantage in harsh environments such as strong electromagnetic interference. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the all-fiber optical path of the spiral fiber grating provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the alkali metal gas chamber provided by the present invention.

[0020] Figure 3 This is a schematic diagram of the exploded structure of the optical fiber bubble cavity in the alkali metal gas chamber provided by the present invention.

[0021] Figure 4 This is a schematic diagram of the micro-cavity structure during the preparation of the alkali metal gas chamber provided by the present invention.

[0022] Figure 5 This is a schematic diagram of the structure of the alkali metal gas chamber after the micro-cavity is expanded during the preparation of the present invention.

[0023] Figure 6 This is a schematic diagram of the gas filling system provided by the present invention.

[0024] Figure 7This is a schematic diagram of the angular rate sensor provided by the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, "multiple" means two or more, unless otherwise explicitly specified.

[0028] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] Example 2

[0030] like Figure 1As shown, an all-fiber optical path of a spiral fiber grating includes a first 45° tilted fiber grating 200, a second 45° tilted fiber grating 300, a birefringent chirped spiral fiber grating 400, and an alkali metal cell 100. One end face of the birefringent chirped spiral fiber grating 400 is connected to the alkali metal cell 100, one end face of the first 45° tilted fiber grating 200 is connected to the other end face of the birefringent chirped spiral fiber grating 400, and one end face of the second 45° tilted fiber grating 300 is connected to the alkali metal cell 100. The polarization direction of the first 45° tilted fiber grating is parallel to the major axis or minor axis of the birefringent chirped spiral fiber grating.

[0031] The spiral fiber grating all-fiber optical path of the present invention uses the first 45° tilted fiber grating 200 and the birefringent chirped spiral fiber grating 400 as the pump optical path and the second 45° tilted fiber grating 300 as the detection optical path. The pump optical path, alkali metal gas cell and detection optical path of the angular rate sensor are integrated on the optical fiber to form an all-fiber structure, which greatly improves the integration of the angular rate sensor and realizes the miniaturization of the angular rate sensor. Moreover, the optical fiber has the advantages of strong anti-electromagnetic interference capability, acid and alkali corrosion resistance, electrical insulation, high measurement accuracy, high reliability and long service life. It also has a great competitive advantage in harsh environments such as strong electromagnetic interference.

[0032] The fiber grating writing plane of the first 45° tilted fiber grating 200 is set at a 45° tilt angle with its fiber axis, which can almost completely leak the p-polarized light in the pump light outside the fiber, while almost completely retaining the s-polarized light in the pump light for transmission in the fiber, thereby converting the pump light into linearly polarized light. The birefringent chirped spiral fiber grating 400 is based on the birefringence effect, and its chirped spiral structure can produce different degrees of phase delay in the linearly polarized light. When the polarization direction of the first 45° tilted fiber grating 200 is parallel to the major axis or minor axis of the birefringent chirped spiral fiber grating 400, the birefringent chirped spiral fiber grating 400 can produce different degrees of phase delay in the linearly polarized light output by the first 45° tilted fiber grating 200. The linearly polarized light with different phase delays is mixed to finally form circularly polarized light.

[0033] Whether the polarization direction of the first 45° tilted fiber grating 200 is parallel to the major axis or the minor axis of the birefringent chirped spiral fiber grating 400, it can convert the linearly polarized light into circularly polarized light. There is no substantial difference in performance or function in converting the linearly polarized light into the circularly polarized light.

[0034] The fiber grating writing plane of the second 45° tilted fiber grating 300 is set at a 45° tilt angle with its fiber axis. Like the first 45° tilted fiber grating 200, it can also leak almost all of the p-polarized light in the probe light outside the fiber, while retaining almost all of the s-polarized light in the probe light for transmission in the fiber, thereby converting the probe light into linearly polarized light.

[0035] The first 45° tilted fiber grating 200, the second 45° tilted fiber grating 300, and the birefringent chirped spiral fiber grating 400 can be made of single-mode fiber. In order to maintain the polarization state of the probe light and pump light during transmission, in this embodiment, the first 45° tilted fiber grating 200, the second 45° tilted fiber grating 300, and the birefringent chirped spiral fiber grating 400 can also be made of polarization-maintaining fiber.

[0036] Considering the difficulty in fabricating a 45° tilted fiber grating using polarization-maintaining fiber, and the fact that the birefringent chirped spiral fiber grating 400 requires a large birefringence and polarization-maintaining capability, it is preferable that the first 45° tilted fiber grating 200 and the second 45° tilted fiber grating 300 are fabricated using single-mode fiber, and the birefringent chirped spiral fiber grating 400 is fabricated using polarization-maintaining fiber.

[0037] Optimally, the birefringent chirped spiral fiber grating 400 is fabricated using elliptical core fiber, so that the birefringent chirped spiral fiber grating 400 forms an elliptical core chirped spiral fiber grating. The elliptical core fiber is a special polarization-maintaining fiber, whose core cross-section is elliptical, rather than the traditional circular. The elliptical core structure can endow the elliptical core fiber with greater birefringence and polarization maintenance capabilities.

[0038] The fiber grating period of the birefringent chirped spiral fiber grating 400 gradually decreases along the light transmission direction, and the minimum fiber grating period of the birefringent chirped spiral fiber grating 400 is not less than the fiber grating period of the first 45° tilted fiber grating 200, so as to achieve a good circular polarization conversion effect.

[0039] Example 2

[0040] As an optimization of Embodiment 1, in this embodiment, such as Figure 2As shown, the alkali metal gas chamber 100 includes a first optical fiber 110, a second optical fiber 120, a third optical fiber 130, and an optical fiber bubble cavity 140. One end face of the first optical fiber 110, the second optical fiber 120, and the third optical fiber 130 is respectively connected to the surface of the optical fiber bubble cavity 140. The other end face of the first optical fiber 110 is connected to the birefringent chirped helical fiber grating 400, and the other end face of the second optical fiber 120 is connected to the second 45° tilted fiber grating 300. The central axis of the second optical fiber 120 coincides with the central axis of the third optical fiber 130, and the central axis of the first optical fiber 110 is perpendicular to the central axes of the second optical fiber 120 and the third optical fiber 130. The optical fiber bubble cavity 140 is sealed and filled with at least alkali metal atoms 150 and inert gas 160.

[0041] The alkali metal gas chamber 100 of the present invention uses the fiber bubble cavity 140 inside the optical fiber as a carrier. It is formed by filling the fiber bubble cavity 140 with alkali metal atoms 150 and inert gas 160, which can ensure high airtightness, high surface accuracy and good inner wall condition of the gas chamber. At the same time, it is relatively easy to realize the release and filling of alkali metal atoms 150 and inert gas 160 in a vacuum environment. The fiber bubble cavity 140 can solve the problems of quantitative filling of high-purity alkali metal atoms 150, precise control of inert gas 160 and structural airtightness, which can further improve the performance of the gas chamber and thus promote the development of angular rate sensors towards small size, long life, high performance, miniaturization and integration.

[0042] In use, the first optical fiber 110 is used for the incident pump light, the second optical fiber 120 is used for the incident probe light, and the third optical fiber 130 is used for the emitted probe light. The pump light is circularly polarized, and the probe light is linearly polarized. The pump light excites the alkali metal atoms 150 in the fiber optic bubble cavity 140 to undergo electronic spin polarization. The alkali metal atoms 150 induce nuclear spin polarization in the inert gas 160 through a spin-exchange collision mechanism. Under a static magnetic field, the nuclear spin-polarized inert gas 160 undergoes Larmor precession around the static magnetic field, and the precession frequency is related to the static magnetic field. When the angular rate sensor rotates around the static magnetic field along with the carrier, the precession frequency of the nuclear spins of the inert gas 160 will drift. The amount of drift is the angular rate of the angular rate sensor. The drift of the precession frequency will cause the polarization plane of the probe light to rotate, which in turn causes a change in the refractive index of the probe light in the fiber optic bubble cavity 140, ultimately resulting in a change in the intensity of the probe light. By analyzing the change in the intensity of the probe light, or by directly analyzing the change in the polarization information of the probe light, the angular rate of the angular rate sensor can be calculated.

[0043] like Figure 3 As shown, a first open vent 141 is formed on one end face of the first optical fiber 110, a second open vent 142 is formed on one end face of the second optical fiber 120, and a third open vent 143 is formed on one end face of the third optical fiber 130. The first open vent 141, the second open vent 142 and the third open vent 143 are aligned and fused together to form the optical fiber bubble cavity 140.

[0044] During preparation, first take a section of optical fiber A, and then... Figure 4 As shown, a femtosecond laser is used to form a micro-cavity 144 at the center of fiber segment A. The micro-cavity 144 is located within the core of fiber segment A. Then, the micro-cavity 144 within fiber segment A is heated by discharge in a fiber fusion splicer, causing localized softening of the fiber segment A near the micro-cavity 144, and so on. Figure 5 The microcavity 144 is expanded to form the fiber bubble cavity 140. During heating, the microcavity 144 can be heated by multiple discharges, gradually increasing the discharge power, and adjusting the discharge position, so that the microcavity 144 gradually expands to the required roundness and size through multiple thermal expansions. At the same time, a weak stress and coaxial rotation are applied to the fiber segment A to ensure that the microcavity 144 is heated uniformly. The microcavity 144 should expand to at least the cladding of the fiber segment A. Then, a femtosecond laser is used to expand the fiber bubble cavity of the fiber segment A. 140 is cut into open vents to form a first optical fiber 110 with a first open vent 141; then two optical fiber segments A are taken and the above steps are repeated to form a first optical fiber 110 with a second open vent 142 and a third optical fiber 130 with a third open vent 143 respectively; finally, after filling the first open vent 141, the second open vent 142 and the third open vent 143 with the alkali metal atoms 150 and the inert gas 160, the first open vent 141, the second open vent 142 and the third open vent 143 are fused and fixed.

[0045] The curvature of the first open vent 141, the second open vent 142, and the third open vent 143 may be the same or different. The key requirement is that when the first optical fiber 110, the second optical fiber 120, and the third optical fiber 130 are combined in such a manner that the second optical fiber 120 and the third optical fiber 130 are parallel, and the first optical fiber 110 is perpendicular to the second optical fiber 120 and the third optical fiber 130, the first open vent 141, the second open vent 142, and the third open vent 143 can form a complete fiber optic bubble cavity 140. Preferably, the fiber optic bubble cavity 140 is a spherical bubble cavity.

[0046] During the gas filling process, a self-built gas filling system is used to align, fill, and splice the first optical fiber 110, the second optical fiber 120, and the third optical fiber 130. For example... Figure 6 As shown, the gas filling system includes a sealed chamber 1, a carbon dioxide laser 2, a first displacement platform 3, a second displacement platform 4, a third displacement platform 5, an ultraviolet laser 6, an alkali metal element 7, a vacuum pumping device 8, a first gas cylinder 9 filled with inert gas 160, and a host computer 12. The carbon dioxide laser 2, the first displacement platform 3, the second displacement platform 4, the third displacement platform 5, the ultraviolet laser 6, and the alkali metal element 7 are all disposed inside the sealed chamber 1. The vacuum pumping device 8, the first gas cylinder 9, and the host computer 12 are all disposed outside the sealed chamber 1. The vacuum pumping device 8 and the first gas cylinder 9 are connected to the sealed chamber 1, and the host computer 12 is connected to control the carbon dioxide laser 2, the first displacement platform 3, the second displacement platform 4, the third displacement platform 5, and the ultraviolet laser 6.

[0047] The vacuum pumping device 8 is used to evacuate the sealed chamber 1 to provide a vacuum environment; the first gas cylinder 9 is used to introduce the inert gas 160 into the sealed chamber 1; the ultraviolet laser 6 is used to vaporize the alkali metal element 7 to form alkali metal atoms 150; the first displacement platform 3, the second displacement platform 4, and the third displacement platform 5 are used to drive the first optical fiber 110, the second optical fiber 120, and the third optical fiber 130 to move respectively; the carbon dioxide laser 2 is used to weld the first open vent 141, the second open vent 142, and the third open vent 143.

[0048] Preferably, the gas filling system further includes at least one of a second gas cylinder 10 filled with buffer gas 170 and a third gas cylinder 11 filled with quenching gas 180, wherein both the second gas cylinder 10 and the third gas cylinder 11 are located outside the sealed chamber 1 and communicate with the sealed chamber 1. The second gas cylinder 10 is used to introduce the buffer gas 170 into the sealed chamber 1, and the third gas cylinder 11 is used to introduce the quenching gas 180 into the sealed chamber 1.

[0049] During gas filling, the first optical fiber 110, the second optical fiber 120, the third optical fiber 130, and the alkali metal element 7 are first placed in the sealed chamber 1, wherein the first open vent 141, the second open vent 142, and the third open vent 143 are arranged opposite to each other; then, the ultraviolet laser 6 emits a high-power ultraviolet laser onto the alkali metal element 7 to excite the alkali metal, causing it to vaporize and release the alkali metal atoms 150. Simultaneously, the inert gas 160, the buffer gas 170, and the quenching gas 180 are respectively introduced into the sealed chamber 1 through the first gas cylinder 9, the second gas cylinder 10, and the third gas cylinder 11, so that the sealed chamber 1 is filled with a mixed gas of the alkali metal atoms 150, the inert gas 160, the buffer gas 170, and the quenching gas 180; then, the first displacement platform 3 and the second displacement platform 4 are used. The third displacement platform 5 adjusts the relative positions of the first optical fiber 110, the second optical fiber 120, and the third optical fiber 130, so that the first open vent 141, the second open vent 142, and the third open vent 143 are aligned with each other and abut against each other to form an unfused fiber bubble cavity 140. Finally, the carbon dioxide laser 2 emits a high-power carbon dioxide laser onto the abutting surfaces between the first open vent 141, the second open vent 142, and the third open vent 143, so that the abutting surfaces between the first open vent 141, the second open vent 142, and the third open vent 143 melt and connect together, thereby sealing the mixture of alkali metal atoms 150, inert gas 160, buffer gas 170, and quenching gas 180 between the first open vent 141, the second open vent 142, and the third open vent 143.

[0050] In this embodiment, the first displacement platform 3, the second displacement platform 4, and the third displacement platform 5 are all three-axis displacement platforms.

[0051] The first optical fiber 110 includes a first core 111 and a first cladding 112, the first cladding 112 surrounding the outer peripheral sidewall of the first core 111; the first core 111 is aligned with the center of the optical fiber bubble cavity 140 to improve the polarization uniformity of the probe light on the alkali metal atoms 150 and the inert gas 160.

[0052] The second optical fiber 120 includes a second fiber core 121 and a second cladding 122, with the second cladding 122 surrounding the outer peripheral sidewall of the second fiber core 121. The third optical fiber 130 includes a third fiber core 131 and a third cladding 132, with the third cladding 132 surrounding the outer peripheral sidewall of the third fiber core 131. The second fiber core 121 is aligned with the third fiber core 131, and the second cladding 122 is aligned with the third cladding 132, so that the probe light transmitted in the second fiber core 121 can be incident into the third fiber core 131 for continued transmission after passing through the fiber bubble cavity 140.

[0053] The diameter of the fiber bubble cavity 140 is at least larger than the diameters of the first fiber core 111, the second fiber core 121, and the third fiber core 131. Preferably, the diameter of the fiber bubble cavity 140 can be slightly larger than the outer diameters of the first cladding 112, the second cladding 122, and the third cladding 132, and the center of the fiber bubble cavity 140 is at the intersection of the central axes of the second fiber 120 and the third fiber 130.

[0054] The first optical fiber 110, the second optical fiber 120, and the third optical fiber 130 can be single-mode optical fibers, while the probe light is linearly polarized light and the pump light is circularly polarized light. In order to maintain the polarization state of the probe light and the pump light during transmission, the first optical fiber 110, the second optical fiber 120, and the third optical fiber 130 can also be polarization-maintaining optical fibers.

[0055] In this embodiment, the first optical fiber 110 is a polarization-maintaining optical fiber, and the second optical fiber 120 and the third optical fiber 130 are single-mode optical fibers.

[0056] The fiber optic bubble chamber 140 is also filled with at least one of a buffer gas 170 (an inert gas without nuclear spin) and a quenching gas 180 (a diatomic molecule).

[0057] The buffer gas 170 is used to collide with the alkali metal atoms 150 to reduce the collision between the alkali metal atoms 150 and the cavity wall of the fiber bubble cavity 140, thereby reducing the depolarization rate of the alkali metal atoms 150 and reducing the photon energy required for the polarization of the alkali metal atoms 150, thus increasing the polarizability of the alkali metal atoms 150. The quenching gas 180 is used to absorb the resonant photons spontaneously emitted when the alkali metal atoms 150 recover from the excited state to the ground state, so as to avoid the resonant photons causing other alkali metal atoms 150 to re-jump from the ground state to the excited state and cause depolarization, thereby reducing the depolarization rate of the alkali metal atoms 150.

[0058] The alkali metal atom 150 may be, but is not limited to, cesium (Cs) or rubidium (Rb) atoms, and the inert gas 160 may be, but is not limited to, xenon, neon, or helium. 3 The buffer gas 170 may be, but is not limited to, helium (He), etc. 4 The quenching gas 180 may be, but is not limited to, nitrogen.

[0059] Example 3

[0060] like Figure 7 As shown, an angular rate sensor includes a pump light source 13, a probe light source 14, a magnetic field generator 15, an analysis and processing device 16, and a spiral fiber optic grating all-fiber optical path as described in Embodiment 1 or Embodiment 2. The pump light source 13 is connected to the other end face of the first 45° tilted fiber grating 200 of the spiral fiber optic grating all-fiber optical path. The probe light source 14 is connected to the other end face of the second 45° tilted fiber grating 300 of the spiral fiber optic grating all-fiber optical path. The analysis and processing device 16 is connected to the alkali metal gas cell 100 of the spiral fiber optic grating all-fiber optical path (the other end face of the third fiber 130). The magnetic field generator 15 is disposed outside the alkali metal gas cell 100 of the spiral fiber optic grating all-fiber optical path.

[0061] The pump light source 13 is used to emit pump light. The pump light passes sequentially through the first 45° tilted fiber grating 200 and the birefringent chirped spiral fiber grating 400 in the all-fiber optical path of the spiral fiber grating and is converted into circularly polarized light, which is then incident into the fiber bubble cavity 140 of the alkali metal gas chamber 100, causing electron spin polarization of the alkali metal atoms 150 and nuclear spin polarization of the inert gas 160. The magnetic field generator 15 is used to provide static magnetic fields in the X, Y, and Z directions of the alkali metal gas chamber 100 to induce nuclear spin polarization. The inert gas 160 undergoes Larmor precession around the static magnetic field; the detection light source 14 is used to emit detection light, which is converted into linearly polarized light after passing through the second 45° tilted fiber grating 300 of the all-fiber optical path of the spiral fiber grating, and then incident into the fiber bubble cavity 140 of the alkali metal gas chamber 100, where its polarization state is modulated by the inert gas 160 of the nuclear spin polarized inert gas 160; the analysis and processing device 16 is used to collect and process the detection light emitted from the alkali metal gas chamber 100 to calculate the angular rate of the angular rate sensor.

[0062] Depending on the demodulation method, the analysis and processing device 16 can also be different. If the angular rate of the angular rate sensor is calculated based on the change in the polarization state of the probe light, then the analysis and processing device 16 can be a polarization analyzer; if the angular rate of the angular rate sensor is calculated based on the change in the light intensity of the probe light, then the analysis and processing device 16 can be a photodetector + host computer.

[0063] The pump light has the same frequency as the natural frequency of the alkali metal atom 150, allowing it to resonate with the alkali metal atom 150 and thereby induce electron spin polarization of the alkali metal atom 150. The probe light has a frequency as far away as possible from the natural frequency of the alkali metal atom 150 to avoid affecting the electron spin polarization of the alkali metal atom 150.

[0064] The angular rate sensor also includes a non-magnetic heating box 17 and a magnetic shielding box 18. The non-magnetic heating box 17 is disposed outside the alkali metal gas chamber 100 of the all-fiber optical path of the spiral fiber grating to increase the number density of the alkali metal atoms 150 and improve the detection accuracy of the angular rate. The magnetic shielding box 18 is disposed outside the magnetic field generator 15 to isolate the external magnetic field and reduce the disturbance of the external magnetic field to the spin polarization.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and not to limit them. Although the embodiments of the present invention have been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the embodiments of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spiral fiber optic grating all-fiber optical path, characterized in that, The fiber includes a first 45° tilted fiber grating, a second 45° tilted fiber grating, a birefringent chirped spiral fiber grating, and an alkali metal cell. One end face of the birefringent chirped spiral fiber grating is connected to the alkali metal cell, one end face of the first 45° tilted fiber grating is connected to the other end face of the birefringent chirped spiral fiber grating, and one end face of the second 45° tilted fiber grating is connected to the alkali metal cell. The polarization direction of the first 45° tilted fiber grating is parallel to the major axis or minor axis of the birefringent chirped spiral fiber grating. The alkali metal gas chamber includes a first optical fiber, a second optical fiber, a third optical fiber, and an optical fiber bubble cavity. One end face of the first, second, and third optical fibers is respectively connected to the surface of the optical fiber bubble cavity. The other end face of the first optical fiber is connected to the birefringent chirped helical fiber grating, and the other end face of the second optical fiber is connected to the second 45° tilted fiber grating. The central axis of the second optical fiber coincides with the central axis of the third optical fiber, and the central axis of the first optical fiber is perpendicular to the central axes of the second and third optical fibers. The optical fiber bubble cavity is sealed and filled with at least alkali metal atoms and an inert gas.

2. The all-fiber optical path of the spiral fiber grating according to claim 1, characterized in that, The birefringent chirped spiral fiber grating is made of polarization-maintaining fiber, and the first 45° tilted fiber grating and the second 45° tilted fiber grating are made of single-mode fiber.

3. The all-fiber optical path of the spiral fiber grating according to claim 1, characterized in that, The birefringent chirped spiral fiber grating is made of elliptical core fiber so that the birefringent chirped spiral fiber grating forms an elliptical core chirped spiral fiber grating.

4. The all-fiber optical path of the spiral fiber grating according to claim 1, characterized in that, The fiber grating period of the birefringent chirped spiral fiber grating gradually decreases along the direction of light transmission, and the minimum fiber grating period of the birefringent chirped spiral fiber grating is not less than the fiber grating period of the first 45° tilted fiber grating.

5. The alkali metal gas chamber according to claim 1, characterized in that, A first open vent is formed on one end face of the first optical fiber, a second open vent is formed on one end face of the second optical fiber, and a third open vent is formed on one end face of the third optical fiber. The first open vent, the second open vent, and the third open vent are aligned and fused together to form the optical fiber bubble cavity.

6. The alkali metal gas chamber according to claim 1, characterized in that, The fiber optic bubble cavity is also filled with at least one of a buffer gas and a quenching gas.

7. The alkali metal gas chamber according to claim 1, characterized in that, The first optical fiber is a polarization-maintaining fiber, while the second and third optical fibers are single-mode fibers.

8. An angular rate sensor, characterized in that, The device includes a pump source, a probe source, a magnetic field generator, an analysis and processing device, and the spiral fiber grating all-fiber optical path as described in claim 1. The pump source is connected to the other end face of the first 45° tilted fiber grating of the spiral fiber grating all-fiber optical path. The probe source is connected to the other end face of the second 45° tilted fiber grating of the spiral fiber grating all-fiber optical path. The analysis and processing device is connected to the other end face of the third fiber of the alkali metal gas cell of the spiral fiber grating all-fiber optical path. The magnetic field generator is disposed outside the alkali metal gas cell of the spiral fiber grating all-fiber optical path.

9. The angular rate sensor according to claim 8, characterized in that, The angular rate sensor also includes a non-magnetic heating box and a magnetic shielding box. The non-magnetic heating box is located outside the alkali metal gas chamber of the all-fiber optical path of the spiral fiber grating, and the magnetic shielding box is located outside the magnetic field generator.

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