Three-channel polarization-maintaining circulator for triaxial fiber-optic gyroscope

Abstract

The invention discloses a three-channel polarization-maintaining circulator for a triaxial fiber-optic gyroscope, and belongs to the technical field of inertial navigation. According to the invention, a highly-integrated integrated design is adopted, the polarization splitting prism, the Faraday rotation assembly and the three groups of optical fiber port assemblies are integrated, and the function of simultaneously processing three paths of optical signals by a single device is realized. The core is that a complex network composed of three discrete 2 * 2 optical fiber couplers is replaced by a spatial optical path, the number of welding points is remarkably reduced, and optical path loss and polarization crosstalk are effectively reduced. An active alignment cementing process based on an ultraviolet curing adhesive is also adopted, so that high stability and reliability of the device in high and low temperature environments are ensured. When the circulator is applied to the three-axis fiber-optic gyroscope, the measurement precision and the signal-to-noise ratio can be improved while miniaturization and light weight of the three-axis fiber-optic gyroscope are realized, and the requirements of a modern inertial navigation system on a high-performance and high-reliability three-axis gyroscope are met.

Description

Technical Field

[0001] This invention relates to the field of inertial navigation technology, and more specifically to a three-channel polarization-maintaining circulator for a three-axis fiber optic gyroscope. Background Technology

[0002] Fiber optic gyroscopes, as a novel type of all-solid-state gyroscope, contain no rotating parts and offer advantages such as fast start-up, wide measurement range, and high reliability, making them a key component of modern inertial navigation systems. With the increasing maturity and standardization of fiber optic gyroscope technology, small triaxial gyroscopes sharing a light source and optical components have been widely adopted. Compared to single-axis fiber optic gyroscope measuring instruments, triaxial gyroscopes offer numerous advantages, including small size, light weight, simple structure, and high efficiency, thus becoming a research hotspot in recent years.

[0003] In inertial measurement systems, gyroscopes are typically required to simultaneously measure angular rates in three mutually perpendicular directions. Traditional solutions usually employ three independent 2×2 fiber couplers to construct the optical path network for three gyroscope sensing loops. For example... Figure 1 As shown, a 1×3 fiber coupler splits the broadband light source output into three paths, each connected to a 2×2 fiber coupler. When the fiber optic gyroscope rotates relative to inertial space, a Sagnac phase shift occurs between two beams of light propagating in opposite directions in the ring optical path. The two beams meet and interfere at the Y-waveguide after passing through the fiber ring. The change in light intensity caused by the interference is detected by a photodetector, and after signal processing, the gyroscope's rotation information is output. However, this traditional architecture based on multiple 2×2 couplers has the following inherent drawbacks:

[0004] 1) The three couplers and the numerous polarization-maintaining fiber fusion splices between them increase the risk of polarization crosstalk, placing extremely high demands on polarization alignment and splicing processes. Any minute polarization state perturbation can introduce additional phase noise, reducing measurement accuracy and signal-to-noise ratio.

[0005] 2) The use of multiple discrete components increases the complexity of optical path assembly, alignment and packaging, leading to increased production costs and challenges to product consistency and reliability.

[0006] To address the aforementioned issues, the optical architecture of traditional three-axis fiber optic gyroscopes needs to be optimized to achieve extreme miniaturization while improving the system's optical performance and reliability. Summary of the Invention

[0007] To solve the above problems, the application provides a miniaturized and integrated three-channel polarization maintaining ring structure.Through the design of an optical path structure, a three-axis optical fiber gyroscope is realized, which can directly replace three separate 2x2 couplers in the traditional three-axis optical fiber gyroscope, thereby reducing the system volume and the number of fusion points, and simultaneously achieving the miniaturization of the optical module, the effective reduction of the system optical path loss, and the improvement of the overall signal-to-noise ratio of the system.

[0008] The application provides a three-channel polarization maintaining ring for a three-axis optical fiber gyroscope, comprising an integrated mounting block, and a first optical fiber port assembly, a second optical fiber port assembly, a third optical fiber port assembly, a polarization beam splitter prism and a Faraday rotation assembly arranged in the integrated mounting block.

[0009] The first optical fiber port assembly comprises a three-core capillary tube and a first collimating lens for fixing a port 1 of three-way incident polarization maintaining optical fiber.

[0010] The second optical fiber port assembly comprises a three-core capillary tube and a second collimating lens for fixing a port 2 of three-way incident polarization maintaining optical fiber.

[0011] The third optical fiber port assembly comprises a three-core capillary tube and a third collimating lens for fixing a port 3 of three-way incident polarization maintaining optical fiber.

[0012] The polarization beam splitter prism is arranged behind the optical path of the first collimating lens.

[0013] The Faraday rotation assembly comprises a magnetic ring and a magneto-optical crystal nested in the magnetic ring, and is arranged between the polarization beam splitter prism and the second collimating lens; after the incident light passes through the cooperative action of the magnetic ring 4 and the magneto-optical crystal, the polarization plane of the light is rotated by 45°.

[0014] The optical axis of the first optical fiber port assembly and the second optical fiber port assembly is collinear, forming a first optical path axis; the optical axis of the third optical fiber port assembly is perpendicular to the first optical path axis, forming a second optical path axis; and the polarization beam splitter prism is located at the intersection of the first optical path axis and the second optical path axis.

[0015] Optionally, the magneto-optical crystal is nested in the magnetic ring, and the optical axis of the magneto-optical crystal coincides with the first optical path axis.

[0016] Optionally, the three-core capillary tube of the port 1, the first collimating lens, the polarization beam splitter prism, the Faraday rotation assembly, the second collimating lens and the three-core capillary tube of the port 2 are arranged in sequence along the first optical path axis; and the polarization beam splitter prism, the third collimating lens and the three-core capillary tube of the port 3 are arranged in sequence along the second optical path axis.

[0017] Optionally, the three-core capillary of the port 1, the three-core capillary of the port 2 and the three-core capillary of the port 3 are used to fix the polarization maintaining fiber head, and the central axes of the three optical fibers are coincided with the optical axes of the corresponding collimating lenses respectively, and the axial distance between the fiber end face and the adjacent collimating lens is equal to the focal length of the collimating lens.

[0018] Optionally, the polarization splitting prism and the Faraday rotation assembly are glued and fixed by active alignment and real-time feedback curing process through the ultraviolet curing glue.

[0019] Optionally, the ultraviolet curing glue is an epoxy resin ultraviolet curing glue with low thermal expansion coefficient and high bonding strength.

[0020] Optionally, the axis of the magneto-optical crystal is located on the first optical path axis.

[0021] Optionally, the magnetic field strength provided by the magnetic ring is configured to produce a 45-degree rotation of the polarization plane of the light wave passing through the magneto-optical crystal.

[0022] Optionally, the first fiber port assembly serves as an input port for three incident lights; the second fiber port assembly serves as a common port leading to the Y waveguide and the fiber ring; and the third fiber port assembly serves as an output port leading to the photodetector.

[0023] Optionally, it is characterized in that it is used for a three-axis fiber-optic gyroscope.

[0024] Compared with the prior art, the present application has at least the following beneficial effects:

[0025] 1) The present application successfully reduces the overall optical path loss by using a spatial optical path method. In the traditional structure, each 2x2 coupler has an insertion loss, and the fusion points between multiple devices introduce additional reflection loss and polarization-dependent loss, resulting in serious signal attenuation. The present application replaces the connection link of the traditional three 2x2 couplers through integrated optical path design, and uses the combination structure of magnetic ring and magneto-optical crystal to effectively suppress the reverse crosstalk and mixing of the measurement signal by using the non-reciprocity of Faraday effect, avoiding the interference of the crosstalk signal on the detection accuracy of Sagnac effect in the traditional structure. Experimental verification shows that the optical path loss of the new structure is successfully reduced by 6dB compared with the traditional structure, improving the measurement accuracy of the three-axis fiber-optic gyroscope.

[0026] 2) The high integration structure of the application successfully reduces the volume of the three-axis fiber-optic gyroscope. The traditional structure needs to use three independent 2x2 couplers to build the optical path. The combination of multiple 2x2 couplers not only occupies a large installation space, but also needs to reserve a complex optical path arrangement and fixing space, which is difficult to adapt to the miniaturization and engineering needs of the gyroscope. The application integrates the polarization beamsplitting prism, magneto-optical crystal, magnetic ring and three-way collimating lens into a single device through integrated design. The overall size of the polarization maintaining ring is 80mmx45mmx20mm, which is conducive to promoting the lightweight and miniaturization of the three-axis fiber-optic gyroscope.

[0027] 3) The application as a whole adopts a gluing process, reducing assembly complexity. The combination of multiple couplers in the traditional structure needs to handle multiple fusion splices and multiple sections of tail fibers, resulting in complex assembly process and tedious production process. The integrated packaging design of the application reduces multiple external connection points and simplifies the assembly process. At the same time, the gluing process has the advantages of low cost, design flexibility in adapting to different shapes of components, and overall support for the core needs of miniaturization, high precision and engineering mass production of the ring. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings are for the purpose of illustrating preferred embodiments of the application and are not to be construed as limiting the application.

[0029] Figure 1 is a schematic diagram of the structure of three independent 2x2 couplers of the traditional three-axis fiber-optic gyroscope;

[0030] Figure 2 is a schematic diagram of the optical path of the three-channel polarization maintaining ring of the application;

[0031] Figure 3 is a schematic diagram of the three-channel polarization maintaining ring of the application;

[0032] Figure 4 is a schematic diagram of the optical path of the three-axis fiber-optic gyroscope of the application;

[0033] Figure 5 is a schematic diagram of the multi-core multiplexing technology optical path of the three-core capillary of the application.

[0034] REFERENCE NUMERALS:

[0035] 1. Three-core capillary of port 1, 2. Collimating lens of port 1, 3. Polarization beamsplitting prism, 4. Magnetic ring, 5. Magneto-optical crystal, 6. Collimating lens of port 2, 7. Three-core capillary of port 2, 8. Collimating lens of port 3, 9. Three-core capillary of port 3. DETAILED DESCRIPTION

[0036] In order to enable the above-mentioned objects, features and advantages of the present application to be clearer, the present application will be further described below with reference to the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict. In addition, the present application can also be implemented in other ways different from those described herein, and therefore the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0037] One specific embodiment of the present application, as Figures 2-4 disclosed a three-channel polarization maintaining ring for three-axis fiber-optic gyroscope, comprising an integrated mounting block, a three-core capillary 1 of port 1, a collimating lens 2 of port 1, a polarization beam splitter prism 3, a magnetic ring 4, a magneto-optical crystal 5, a collimating lens 6 of port 2, a three-core capillary 7 of port 2, a collimating lens 8 of port 3 and a three-core capillary 9 of port 3.

[0038] Further, the three-core capillary 1 of port 1, the collimating lens 2 of port 1, the polarization beam splitter prism 3, the magnetic ring 4, the magneto-optical crystal 5, the collimating lens 6 of port 2, the three-core capillary 7 of port 2, the collimating lens 8 of port 3 and the three-core capillary 9 of port 3 are integrally arranged in the integrated mounting block; the integrated mounting block comprises a first channel, a second channel, a third channel and a mounting slot, the three-core capillary 1 of port 1 is arranged in the first channel for fixing the three-way polarization maintaining optical fiber head entering the integrated mounting block; the collimating lens 2 of port 1 is arranged at the light outlet of the three-core capillary 1 of port 1 in the first channel; the polarization beam splitter prism 3, the magnetic ring 4 and the magneto-optical crystal 5 are arranged in the mounting slot; the polarization beam splitter prism 3 is arranged between the magneto-optical crystal 5 and the collimating lens 2 of port 1, and the magneto-optical crystal 5 is arranged close to one end of the collimating lens 6 of port 2; the collimating lens 6 of port 2 and the three-core capillary 7 of port 2 are arranged in the second channel, and the three-way polarization maintaining optical fiber head exiting the integrated mounting block is fixed by the three-core capillary 7 of port 2; the collimating lens 8 of port 3 and the three-core capillary 9 of port 3 are arranged in the third channel, and the three-way polarization maintaining optical fiber head exiting the integrated mounting block is fixed by the three-core capillary 9 of port 3.

[0039] Preferably, referring to Figure 3 , the magneto-optical crystal 5 is nested in the magnetic ring 4, the axis of the magneto-optical crystal 5 coincides with the axis of the magnetic ring 4, and the light transmitted through the polarization beam splitter prism 3 is normally incident from the surface center of the magneto-optical crystal 5.

[0040] Preferably, the first channel, the second channel, the third channel and the mounting slot of the integrated mounting block form a T shape; the mounting slot is arranged between the first channel and the second channel; the axes of the first channel and the second channel are the same, the axis of the third channel is perpendicular to the axes of the first channel and the second channel, and coincides with the reflection axis of the polarization beam splitter prism 3.

[0041] Further, the polarization beam splitter is a cube, and its transmission axis coincides with the axis of the first and second channels, and its reflection axis coincides with the axis of the third channel.

[0042] Preferably, the three-core capillary 1 of the port 1, the collimating lens 2 of the port 1, the polarization beam splitter 3, the magnetic ring 4, the magneto-optical crystal 5, the collimating lens 6 of the port 2, the three-core capillary 7 of the port 2 are all located on the axis of the first and second channels; the polarization beam splitter 3, the collimating lens 8 of the port 3, and the three-core capillary 9 of the port 3 are all located on the axis of the third channel, and the optical axes of all components are the same height; wherein all the three-core capillaries are used to fix the position of the fiber head, so that the central axes of the three optical fibers coincide with the optical axes of the collimating lenses, and the axial distance between the fiber end face and the adjacent collimating lens is equal to the focal length of the collimating lens, thereby forming a multi-core fiber multiplexing technology.

[0043] In the implementation of the multi-core fiber multiplexing technology of the three-core capillary, the three-core capillary structure is as shown in Figure 5 which is composed of a central optical fiber and two side optical fibers symmetrically distributed, and the axial distance between the two adjacent optical fibers is d, and the optical axis of the central optical fiber naturally coincides with the main optical axis of the collimating lens, so that the divergent light emitted by the central optical fiber becomes approximately ideal parallel light after passing through the collimating lens; and the optical axes of the two side optical fibers are laterally spaced apart from the main optical axis of the central optical fiber by a distance d, so that the divergent light emitted by the two side optical fibers forms a small offset angle θ with the main optical axis after passing through the collimating lens.

[0044] Further, the expression of the offset angle θ is:

[0045] θ≈arctan(d / f), wherein f is the focal length of the collimating lens.

[0046] For example, in the process of light beam propagating from the first channel to the second channel, due to the small polarization angle θ between the light beams emitted from the two sides and the main optical axis, when the non-parallel light beams of the two sides reach the collimating lens 6 in the second channel during the transmission process, the non-parallel light beams of the two sides have a lateral offset with the main optical axis, and after the action of the collimating lens 6, the originally non-parallel light beams of the two sides will be coupled into the two side optical fibers of the three-core capillary 7 respectively. In order to solve the aforementioned multi-dimensional alignment problem, the present application adopts the following calibration method: by accurately controlling the spacing d between the three optical fibers in the capillary of the three channels, and then controlling the offset angle θ between the non-parallel light of the two side optical fibers and the main optical axis of the central optical fiber, the process of light emission from the optical fiber, entering the spatial light, and then coupling into the optical fiber can be accurately coupled each time, thereby improving the coupling efficiency of the present application. In the assembly link of the present application, a precise six-dimensional pose adjustment and real-time online monitoring feedback method is introduced. Specifically, for example, in the process of light beam propagating from the first channel to the second channel, under the light transmission state, the three-core capillary 1 of the port 1 and the three-core capillary 7 of the port 2 are controlled by two six-dimensional adjustment frames respectively, three photoelectric detectors are connected to the three optical fibers of the three-core capillary 7 of the port 2 respectively, which are used for real-time monitoring of the light emission state of the three optical fibers. By adjusting the knobs of the six-dimensional adjustment frame to fine-tune the spacing d between the adjacent optical fibers in the three-core capillary assembly, the change of the reading of the photoelectric detector at the light emission end of each optical fiber is observed during the fine-tuning process, and when the reading of the detector reaches the maximum, the best state of the spacing of the three-core capillary assembly is obtained, thereby successfully controlling the overall insertion loss of the three channels to a low level. This series of special alignment process for multi-core fiber multiplexing is the key to realizing the high performance and high consistency of the present application. After determining the first channel capillary spacing d1 and the second channel capillary spacing d2, the photoelectric detector in the second channel during debugging is replaced by a y waveguide and an optical fiber ring, so that the third channel can transmit light. Similarly, three photoelectric detectors are connected to the third channel respectively, which are used for real-time monitoring of the light emission state, and then the six-dimensional adjustment frame is used to fine-tune the capillary spacing d3 of the third channel, so that the reading of the photoelectric detector reaches the maximum, that is, the best position is adjusted.

[0047] Another embodiment of the present application is as follows: Figure 4 A three-axis fiber optic gyroscope is also disclosed, which is provided with the foregoing three-channel polarization maintaining ring, can simultaneously measure the angular velocities of three orthogonal axes, can meet the demand of the system for multi-dimensional angular rate sensing, and can improve the autonomy and anti-interference ability of navigation.

[0048] It comprises a wide spectrum light source, a 1*3 coupler, a three-channel polarization maintaining ring, a photoelectric detector, three Y waveguides and three optical fiber rings.

[0049] In use, the whole light path is: the SLD wide spectrum light source emits low coherence light, which is divided into three paths through a 1*3 coupler, and input into the input port 1 of a three-channel polarization maintaining ring, and enters the first channel. The three-core capillary 1 of the port 1 fixes the position of the incident optical fiber head, and the spatial light is converted through the collimating lens 2 of the port 1, enters the polarization beam splitter prism 3, and the e light is directly transmitted, enters the magneto-optical crystal 5, and is deflected in the polarization direction under the action of the magnetic ring 4, and enters the second channel. Here, the design is that after the incident light cooperates with the magnetic ring 4 and the magneto-optical crystal 5, the rotation angle of the polarization plane of the light is 45°.

[0050] The present application sets the rotation angle of the polarization plane of the light to 45°, so that the return light can accurately exhibit o light characteristics in the polarization beam splitter prism 3, reduce the loss, improve the measurement accuracy, and achieve the target rotation angle (i.e. the rotation angle of the polarization plane of the light) by adjusting the magnetic induction intensity of the magnetic ring 4 and the length of the magneto-optical crystal 5.

[0051] It can be understood that the e light exhibits as transmitted light in the polarization beam splitter prism 3, and the vibration direction is parallel to the incident plane; the o light exhibits as reflected light in the polarization beam splitter prism 3, and the vibration direction is perpendicular to the incident plane.

[0052] The spatial light is coupled into the three polarization maintaining optical fibers of the port 2 through the collimating lens 6 of the port 2, and the position of the optical fiber head is fixed by the three-core capillary 7 of the port 2. The three polarization maintaining optical fibers of the second channel are output from the ring, and are respectively connected to three Y waveguides, and then are respectively connected to three optical fiber rings. Each path of light is divided into clockwise and counterclockwise light, and propagates along the two directions of the respective optical fiber ring. The Y waveguide has a phase modulation function, which is used for bias modulation and phase compensation of the fiber optic gyroscope. When the optical fiber ring rotates around its sensitive axis, due to the Sagnac effect, the two beams of light propagating clockwise and counterclockwise produce an optical path difference, and then form a phase difference proportional to the angular velocity. After the two beams of light propagate through the optical fiber ring and return to the Y waveguide, interference occurs, and the interference light intensity changes with the phase difference. The interference light carrying the angular velocity information is reversely transmitted into the second channel of the three-channel polarization maintaining ring again, and the return light cooperates with the magnetic ring 4 and the magneto-optical crystal 5. According to the non-reciprocity principle of the Faraday effect, the rotation direction of the polarization plane is only determined by the magnetic field direction, and is independent of the propagation direction of the light, so at this time the return light of the second channel reaches the polarization beam splitter prism 3, the polarization direction is rotated by 45° again, and the initial direction is deflected by 90° to become o light, which is reflected to the third channel by the polarization beam splitter prism 3. The spatial light is coupled into the polarization maintaining optical fiber of the port 3 through the collimating lens 8 of the port 3, and the output optical fiber head is also fixed by the three-core capillary 9 of the port 3. Finally, the polarization maintaining optical fiber of the third channel is output from the ring, and is respectively connected to three photodetectors. The photodetector of each channel converts the optical signal into an electrical signal, and after demodulation and signal processing, the angular velocity measurement value corresponding to the axial direction can be obtained, and finally the simultaneous measurement of the three-axis angular rate is realized.

[0053] Further, when the integrated mounting block is processed, the positioning accuracy of each element in it is very high. In order to realize the extremely low insertion loss and high consistency of the three-channel circulator, the present application adopts the active alignment and real-time feedback curing process based on ultraviolet (UV) curing glue. When the polarization maintaining optical fiber, three-core capillary and collimating lens are assembled, instead of using the traditional static curing method after dispensing, the UV curing glue is first dispensed in a trace on the interface to be bonded; then, test light is introduced into the port 1 end of the circulator, and an optical power meter is connected to the port 2 or port 3 end to monitor the output optical power in real time. The spatial six-dimensional pose of the optical fiber or lens is adjusted by a precision adjustment mechanism, and when the monitored optical power reaches the maximum value, it indicates that the optical alignment is in the optimal state. At this time, the glue is irradiated with a specific wavelength of ultraviolet light to make it rapidly cured within a few seconds, thereby ensuring that the optical elements are in the best alignment position. This process ensures that the insertion loss of each channel is minimized and has high consistency, which is significantly better than the passive alignment method which relies on the experience of the operator. At the same time, in order to ensure the long-term stability and reliability of the circulator within -40℃ to +85℃, the present application particularly selects the epoxy resin type UV curing glue with low thermal expansion coefficient and high bonding strength. The thermal expansion coefficient of this adhesive material matches the thermal expansion coefficients of the key materials such as quartz optical fiber, glass lens and ceramic packaging shell. It can effectively suppress the internal stress caused by the expansion difference of different materials during temperature cycling. Thus, the optical elements are prevented from being affected by stress, causing micro-bending or angular deflection, and introducing additional optical path loss and polarization crosstalk.

[0054] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A three-channel polarization-maintaining circulator for a three-axis fiber optic gyroscope, characterized in that, Includes an integrated mounting block, and a first fiber optic port assembly, a second fiber optic port assembly, a third fiber optic port assembly, a polarizing beam splitter (3), and a Faraday rotation assembly disposed within the integrated mounting block: The first fiber optic port assembly includes a three-core capillary tube (1) for fixing port 1 of three incident polarization-maintaining fibers and a first collimating lens (2). The second fiber optic port assembly includes a three-core capillary tube (7) for fixing the port 2 of the three-way outgoing polarization-maintaining fiber and a second collimating lens (6). The third fiber optic port assembly includes a three-core capillary tube (9) for fixing the three output polarization-maintaining fibers and a third collimating lens (8). A polarizing beam splitter (3) is disposed behind the optical path of the first collimating lens (2); The Faraday rotation component, including a magnetic ring (4) and a magneto-optical crystal (5) nested therein, is disposed between the polarizing beam splitter (3) and the second collimating lens (6); after the incident light passes through the magnetic ring 4 and the magneto-optical crystal (5) in synergy, the polarization plane of the light rotates by 45°. Wherein, the optical axes of the first optical fiber port assembly and the second optical fiber port assembly are collinear, forming the first optical path axis; The optical axis of the third optical fiber port assembly is perpendicular to the first optical path axis, forming the second optical path axis; the polarizing beam splitter (3) is located at the intersection of the first optical path axis and the second optical path axis.

2. The three-channel polarization-maintaining circulator according to claim 1, characterized in that, The magneto-optical crystal (5) is nested in the magnetic ring (4), and its optical axis coincides with the first optical path axis.

3. The three-channel polarization-maintaining circulator according to claim 1, characterized in that, The three-core capillary tube (1), the first collimating lens (2), the polarizing beam splitter (3), the Faraday rotation assembly, the second collimating lens (6), and the three-core capillary tube (7) of port 1 are arranged sequentially along the first optical path axis; the polarizing beam splitter (3), the third collimating lens (8), and the three-core capillary tube (9) of port 3 are arranged sequentially along the second optical path axis.

4. The three-channel polarization-maintaining circulator according to claim 1, characterized in that, The three-core capillary tube (1) at port 1, the three-core capillary tube (7) at port 2, and the three-core capillary tube (9) at port 3 are used to fix the polarization-maintaining fiber head and make the central axis of the three optical fibers coincide with the optical axis of the corresponding collimating lens, and the axial distance between the fiber end face and the adjacent collimating lens is equal to the focal length of the collimating lens.

5. The three-channel polarization-maintaining circulator according to claim 1, characterized in that, The polarizing beam splitter (3) and the Faraday rotation component are fixed by UV curing adhesive through active alignment and real-time feedback curing process.

6. The three-channel polarization-maintaining circulator according to claim 5, characterized in that, The UV-curing adhesive is an epoxy resin-based UV-curing adhesive with a low coefficient of thermal expansion and high bonding strength.

7. The three-channel polarization-maintaining circulator according to claim 1, characterized in that, The axis of the magneto-optical crystal is located on the first optical path axis.

8. The three-channel polarization-maintaining circulator according to claim 1, characterized in that, The magnetic field strength provided by the magnetic ring (4) is configured to cause a 45-degree rotation of the polarization plane of the light wave passing through the magneto-optical crystal (5).

9. The three-channel polarization-maintaining circulator according to claim 1, characterized in that, The first fiber optic port assembly serves as the input port for the three incident beams; the second fiber optic port assembly serves as the common port leading to the Y-waveguide and the fiber optic loop; and the third fiber optic port assembly serves as the output port leading to the photodetector.

10. The three-channel polarization-maintaining circulator according to any one of claims 1-9, characterized in that, It was used in a three-axis fiber optic gyroscope.

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