Fiber-optic gyroscope based on 3*3 coupler as well as preparation method and measurement method of fiber-optic gyroscope

Abstract

The invention relates to a sensor as well as a preparation method and a measurement method thereof, in particular to a fiber-optic gyroscope based on a 3 * 3 coupler as well as a preparation method and a measurement method thereof, and aims to solve the problems of lower bandwidth, limited measurement range or higher cost of the conventional fiber-optic gyroscope. The fiber-optic gyroscope comprises a fiber-optic gyroscope table body, a fiber-optic ring fixing cavity arranged on the fiber-optic gyroscope table body, and a combined body of a main fiber-optic ring and a cushion fiber layer ring which are arranged in the fiber-optic ring fixing cavity, the device further comprises an erbium-doped optical fiber light source, a 2 * 2 single-mode optical fiber coupler, an integrated optical modulator, a first photoelectric detector, an optical fiber isolator, a 3 * 3 single-mode optical fiber coupler, a second photoelectric detector and a third photoelectric detector. The method has the advantages that the assembly space of the gyroscope is greatly saved, and meanwhile, the cost of the backup fiber-optic gyroscope is also reduced; and the length and the diameter of the optical fiber ring of the gyroscope for stripe correction can be flexibly adjusted according to actual use requirements.

Description

Technical Field

[0001] This invention relates to a sensor and its preparation and measurement methods, specifically to a fiber optic gyroscope based on a 3×3 coupler and its preparation and measurement methods. Background Technology

[0002] High-precision fiber optic gyroscopes require accuracy in the thousands of units, and the length of the sensing ring typically exceeds 2 km. While long rings improve gyroscope accuracy, they also reduce the gyroscope's range, failing to meet usage requirements. Therefore, a method of cross-interference fringe demodulation is needed to increase the gyroscope's range. This involves using another low-precision, high-range fringe-correcting gyroscope to correct the output of the high-precision fiber optic gyroscope. The difference between the angular rate of the fringe-correcting gyroscope and the angular rate of the high-precision fiber optic gyroscope is calculated, and this difference is used to determine the interference fringe order of the high-precision fiber optic gyroscope. This ensures the high-precision fiber optic gyroscope operates at the accurate interference order, thus outputting the correct angular rate. Fringe-correcting gyroscopes generally come in two forms:

[0003] 1) MEMS gyroscopes are used, but MEMS gyroscopes have low bandwidth and limited measurement range;

[0004] 2) Utilizing a fiber optic gyroscope with a wide single-strip measurement range typically involves adding a set of smaller fiber optic gyroscopes to an existing fiber optic gyroscope system. These are closed-loop or open-loop fiber optic gyroscopes with a working wavelength of 1310nm (the optical path structure is similar to that of a high-precision fiber optic gyroscope). Common examples include fiber optic gyroscopes based on 2×2 couplers; see [link to relevant documentation]. Figure 1 The system includes a main fiber optic gyroscope a1 and a correction fiber optic gyroscope a2, both connected to a signal processing circuit 030. Each gyroscope includes a light source, a photodetector 011, a 2×2 coupler 07 connected at one end to the light source and photodetector 011, a Y-waveguide 020 connected at the other end of the 2×2 coupler 07, and a fiber optic loop 09 connected at the other end of the Y-waveguide 020. The 2×2 coupler 07 has a back-reflection cancellation end. The light source for the main fiber optic gyroscope a1 is an erbium-doped fiber optic light source 06, and the light source for the correction fiber optic gyroscope a2 is an SLD light source 061. The disadvantage of this structure is that it increases the size and cost of the fiber optic gyroscope. Summary of the Invention

[0005] The purpose of this invention is to address the problems of low bandwidth, limited measurement range, or high cost of existing fiber optic gyroscopes, and to provide a fiber optic gyroscope based on a 3×3 coupler, as well as its fabrication and measurement methods.

[0006] To achieve the above objectives, the technical solution provided by this invention is:

[0007] A fiber optic gyroscope based on a 3×3 coupler, which is special in that:

[0008] It includes a fiber optic gyroscope platform, a fiber optic ring fixing cavity disposed on the fiber optic gyroscope platform, and a main fiber optic ring and a fiber pad ring disposed within the fiber optic ring fixing cavity; the fiber pad ring is the fiber optic ring of a gyroscope for stripe correction.

[0009] It also includes an erbium-doped fiber light source, a 2×2 single-mode fiber coupler, an integrated optical modulator, a first photodetector, a fiber isolator, a 3×3 single-mode fiber coupler, a second photodetector, and a third photodetector;

[0010] The two pigtails of the main fiber ring are respectively connected to the two output pigtails of the integrated optical modulator; the output pigtail of the erbium-doped fiber light source is connected to one input pigtail of the 2×2 single-mode fiber coupler; the output end of the 2×2 single-mode fiber coupler is connected to the input pigtail of the integrated optical modulator; the other input pigtail of the 2×2 single-mode fiber coupler is connected to the input end of the first photodetector; the input pigtail of the fiber isolator is connected to the idle output end of the 2×2 single-mode fiber coupler; the two output pigtails of the 3×3 single-mode fiber coupler are respectively fused to the two pigtails of the fiber pad ring; the output pigtail of the fiber isolator is fused to one input pigtail of the 3×3 single-mode fiber coupler; the other two input pigtails of the 3×3 single-mode fiber coupler are respectively connected to the input ends of the second and third photodetectors.

[0011] The output terminals of the first photodetector, the second photodetector, and the third photodetector are electrically connected to the signal processing circuit of the fiber optic gyroscope, respectively.

[0012] The fiber optic isolator is used to prevent the optical signal returned by the fiber pad ring from entering the photodetector through the idle end of the 2×2 single-mode fiber coupler and interfering with the signal of the main gyroscope.

[0013] Furthermore, the main fiber ring is located outside the fiber pad ring, and the main fiber ring and the fiber pad ring have the same fiber exit direction and position.

[0014] Furthermore, the erbium-doped fiber light source is an erbium-doped fiber light source with optical power control function.

[0015] Meanwhile, this invention also provides a method for fabricating the aforementioned fiber optic gyroscope based on a 3×3 coupler, characterized by the following steps:

[0016] Step 1: Prepare fiber optic winding fixture, fiber optic winding equipment, and main fiber and pad fiber of preset length. The main fiber and pad fiber have the same operating wavelength.

[0017] Step 2: Use fiber optic winding fixtures and fiber optic winding equipment to wind and process the main fiber and the fiber pad layer fiber to obtain a combination of the main fiber ring made from the main fiber and the fiber pad layer ring made from the fiber pad layer fiber.

[0018] Step 3: Prepare a circular fiber optic ring fixing cavity with fiber outlets on the inner ring sidewalls; glue and fix the main fiber optic ring and the padding fiber ring assembly inside the fiber optic ring fixing cavity.

[0019] Step 4: Lead out the two pigtails of the main fiber ring and the two pigtails of the padding layer ring from the fiber outlet;

[0020] Step 5: Prepare the erbium-doped fiber light source, 2×2 single-mode fiber coupler, integrated optical modulator, first photodetector, fiber isolator, 3×3 single-mode fiber coupler, second photodetector and third photodetector, and connect them to the two pigtails of the main fiber ring according to the preset connection method.

[0021] Step 6: Connect the output terminals of the first photodetector, the second photodetector, and the third photodetector to the signal processing circuit of the fiber optic gyroscope, respectively.

[0022] Step 7: Install the fiber optic ring fixing cavity, erbium-doped fiber light source, 2×2 single-mode fiber coupler, integrated optical modulator, first photodetector, fiber isolator, 3×3 single-mode fiber coupler, second photodetector and third photodetector at preset positions on the fiber optic gyroscope platform to finally obtain a fiber optic gyroscope based on a 3×3 coupler.

[0023] Further, in step 1, the optical fiber winding fixture includes a circular first baffle and a second baffle, and a skeleton disposed between the first baffle and the second baffle. The radial cross-section of the skeleton is a ring, and its two ends are connected to the first baffle and the second baffle respectively. An arc-shaped first fiber guide groove and a second fiber guide groove are disposed on the inner sidewall of the second baffle between its outer edge and the skeleton. The first fiber guide groove and the second fiber guide groove are used to guide the two pigtails of the padding fiber ring.

[0024] Furthermore, the fiber winding equipment mentioned in step 2 is a winding machine, and the specific steps of using fiber winding fixtures and fiber winding equipment to wind and process the main fiber and the fiber pad layer are as follows:

[0025] The fiber winding fixture is fixed to the winding machine with screws. First, a fiber pad ring is wound along the outer wall of the skeleton. After the winding is completed, the two pigtails of the fiber pad ring are led out from the first fiber guide groove and the second fiber guide groove to the outer edge of the second baffle and fixed with tape. The size of the first fiber guide groove and the second fiber guide groove are adapted to the fiber of the fiber pad ring, so that the inner side of the second baffle is flat after the pigtails are put in. Then, the main fiber ring is wound on the outside of the fiber pad ring using the same method as the fiber pad ring, and the fiber exit direction and position of the main fiber ring and the fiber pad ring are the same. Finally, the main fiber ring and the fiber pad ring are cured and de-skeletonized.

[0026] Furthermore, step 5 specifically includes:

[0027] Prepare an erbium-doped fiber optic source with optical power control, a 2×2 single-mode fiber coupler, an integrated optical modulator, a first photodetector, a fiber isolator, a 3×3 single-mode fiber coupler, a second photodetector, and a third photodetector; wherein the 2×2 single-mode fiber coupler has two input pigtails, one output pigtail, and one output idle end; the integrated optical modulator has one input pigtail and two output pigtails; the 3×3 single-mode fiber coupler has three input pigtails, two output pigtails, and one output anti-return end; and the fiber isolator has one input pigtail and one output pigtail.

[0028] Then, the two pigtails of the main fiber ring are fused to the two output pigtails of the integrated optical modulator, the output pigtail of the erbium-doped fiber light source is fused to one input pigtail of the 2×2 single-mode fiber coupler, the output end of the 2×2 single-mode fiber coupler is fused to the input pigtail of the integrated optical modulator, and the other input pigtail of the 2×2 single-mode fiber coupler is connected to the input end of the first photodetector; the input pigtail of the fiber isolator is connected to the unused output end of the 2×2 single-mode fiber coupler; finally, the two output pigtails of the 3×3 single-mode fiber coupler are fused to the two pigtails of the fiber pad ring, the output pigtail of the fiber isolator is fused to one input pigtail of the 3×3 single-mode fiber coupler, and the other two input pigtails of the 3×3 single-mode fiber coupler are connected to the input ends of the second and third photodetectors, respectively.

[0029] Furthermore, this invention also provides the above-mentioned measurement method for a fiber optic gyroscope based on a 3×3 coupler, which is characterized by including the following steps:

[0030] Step 1: The main fiber loop and integrated optical modulator form the first Sagnac interferometer, which is sensitive to the Sagnac phase difference caused by the input angular velocity in real time;

[0031] Step 2: A second Sagnac interferometer is formed by a fiber pad ring and a 3×3 single-mode fiber coupler to sense the Sagnac phase difference caused by the input angular velocity in real time;

[0032] Step 3: The optical signal returned by the first Sagnac interferometer formed by the main fiber ring and the integrated optical modulator is transmitted to the first photodetector; the optical signal returned by the second Sagnac interferometer formed by the fiber pad ring and the 3×3 single-mode fiber coupler is transmitted to the second photodetector and the third photodetector.

[0033] Step 4: The first photodetector, the second photodetector, and the third photodetector convert the optical signal into an electrical signal, which is then amplified by the IV conversion circuit and the analog-to-digital conversion circuit in sequence, and transmitted to the signal processing circuit.

[0034] Step 5: The signal processing circuit calculates the angular velocity information of the gyroscope used for stripe correction and compares it with the angular velocity information of the main fiber optic gyroscope in real time. If an angular velocity error occurs, the angular velocity of the main fiber optic gyroscope is corrected.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] 1. This invention provides a method for fabricating a fiber optic gyroscope based on a 3×3 coupler. The idle end of the main fiber optic gyroscope is used as the light source input for the fringe correction gyroscope, and the fiber pad layer of the main fiber optic gyroscope's fiber ring serves as the fiber ring for the fringe correction gyroscope. Furthermore, a 3×3 coupler replaces the Y-waveguide, which not only greatly saves gyroscope assembly space but also reduces the cost of backup fiber optic gyroscopes. Moreover, the length and diameter of the fiber ring for the fringe correction gyroscope can be flexibly adjusted according to actual usage requirements.

[0037] 2. The present invention provides a method for fabricating a fiber optic gyroscope based on a 3×3 coupler, which can flexibly change the assembly method according to the actual gyroscope platform structure. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a correction system for an existing fiber optic gyroscope based on a 2×2 coupler;

[0039] Figure 2 This is a schematic diagram of the fiber optic gyroscope fabrication method based on a 3×3 coupler and the fiber optic winding tooling in an embodiment of the fiber optic gyroscope fabricated using this method, according to the present invention.

[0040] Figure 3 This is a schematic diagram illustrating the principle of a method for fabricating a fiber optic gyroscope based on a 3×3 coupler and an embodiment of a fiber optic gyroscope fabricated using this method, according to the present invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] a1-Main fiber optic gyroscope, a2-Correction fiber optic gyroscope, 06-Erbium-doped fiber optic light source, 061-SLD light source, 07-2×2 coupler, 09-Fiber optic ring, 011-Photodetector, 020-Y waveguide, 030-Signal processing circuit;

[0043] 1-First baffle, 2-Frame, 3-Second baffle, 4-First fiber guide groove, 5-Second fiber guide groove, 6-Erbium-doped fiber light source, 7-2×2 single-mode fiber coupler, 8-Integrated optical modulator, 9-Main fiber ring, 10-Fiber pad layer fiber ring, 11-First photodetector, 12-Fiber isolator, 13-3×3 single-mode fiber coupler, 14-Output anti-return end, 15-Second photodetector, 16-Third photodetector. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0045] A fiber optic gyroscope based on a 3×3 coupler, see [link / reference]. Figure 3 ;

[0046] The system includes a fiber optic gyroscope platform, a fiber optic ring fixing cavity mounted on the platform, and a main fiber optic ring 9 and a fiber pad ring 10 disposed within the fixing cavity. The system satisfies the following conditions: a) the main fiber optic ring 9 is located outside the fiber pad ring 10; b) the main fiber optic ring 9 and the fiber pad ring 10 have the same fiber exit direction and position, ensuring that subsequent bonding and sealing operations on the main fiber optic ring 9 or the fiber pad ring 10 are not affected. The fiber pad ring 10 is the fiber optic ring for a gyroscope used for stripe correction.

[0047] It also includes an erbium-doped fiber light source 6 with optical power control function, a 2×2 single-mode fiber coupler 7, an integrated optical modulator 8, a first photodetector 11, a fiber isolator 12, a 3×3 single-mode fiber coupler 13, a second photodetector 15, and a third photodetector 16; wherein the 2×2 single-mode fiber coupler 7 has two input pigtails, one output pigtail, and one output idle end; the integrated optical modulator 8 has one input pigtail and two output pigtails; the 3×3 single-mode fiber coupler 13 has three input pigtails, two output pigtails, and one output anti-return end 14; and the fiber isolator 12 has one input pigtail and one output pigtail.

[0048] The two pigtails of the main fiber ring 9 are respectively connected to the two output pigtails of the integrated optical modulator 8. The output pigtail of the erbium-doped fiber light source 6 is connected to one input pigtail of the 2×2 single-mode fiber coupler 7. The output end of the 2×2 single-mode fiber coupler 7 is connected to the input pigtail of the integrated optical modulator 8. The other input pigtail of the 2×2 single-mode fiber coupler 7 is connected to the input end of the first photodetector 11. The input pigtail of the fiber isolator 12 is connected to the idle output end of the 2×2 single-mode fiber coupler 7. The two output pigtails of the 3×3 single-mode fiber coupler 13 are respectively fused to the two pigtails of the fiber pad ring 10. The output pigtail of the fiber isolator 12 is fused to one input pigtail of the 3×3 single-mode fiber coupler 13. The other two input pigtails of the 3×3 single-mode fiber coupler 13 are respectively connected to the input ends of the second photodetector 15 and the third photodetector 16.

[0049] The output terminals of the first photodetector 11, the second photodetector 15 and the third photodetector 16 are respectively electrically connected to the signal processing circuit 30 of the fiber optic gyroscope.

[0050] The fiber optic isolator 12 is used to prevent the optical signal returned from the fiber pad ring 10 from entering the photodetector 11 through the idle end of the output of the 2×2 single-mode fiber coupler 7, thereby interfering with the signal of the main gyroscope.

[0051] This embodiment also provides a method for fabricating the aforementioned fiber optic gyroscope based on a 3×3 coupler, including the following steps:

[0052] Step 1: Prepare the fiber optic winding fixture, fiber optic winding equipment, and pre-length main fiber and padding fiber, wherein the main fiber and padding fiber have the same operating wavelength; see [link to fiber optic winding fixture] for details. Figure 2 It includes a circular first baffle 1 and a second baffle 3, and a skeleton 2 disposed between the first baffle 1 and the second baffle 3. The skeleton 2 is a ring, and its two ends are connected to the first baffle 1 and the second baffle 3 respectively. An arc-shaped first fiber guide groove 4 and a second fiber guide groove 5 are disposed on the inner side wall of the second baffle 3 between its outer edge and the skeleton 2. The first fiber guide groove 4 and the second fiber guide groove 5 are used to guide out the two tail fibers of the padding fiber ring 10.

[0053] Step 2: Fix the fiber winding fixture to the winding machine with screws. First, wind the fiber padding ring 10 along the outer wall of the skeleton 2. After winding, lead the two pigtails of the fiber padding ring 10 out from the first fiber guide groove 4 and the second fiber guide groove 5 respectively to the outer edge of the second baffle 3 and fix them with tape. The size of the first fiber guide groove 4 and the second fiber guide groove 5 is adapted to the fiber of the fiber padding ring 10 so that the inner side of the second baffle 3 is flat after the pigtails are put in. Then, use the same method as winding the fiber padding ring 10 to wind the main fiber ring 9 on the outside of the fiber padding ring 10, and make the fiber exit direction and position of the main fiber ring 9 and the fiber padding ring 10 the same. Finally, cure and remove the skeleton from the main fiber ring 9 and the fiber padding ring 10 to obtain the combination of the main fiber ring 9 made of the main fiber and the fiber padding ring 10 made of the fiber padding ring.

[0054] Step 3: Prepare a circular fiber optic ring fixing cavity with fiber outlets on the inner ring sidewall; glue and fix the assembly of the main fiber optic ring 9 and the fiber pad ring 10 inside the fiber optic ring fixing cavity.

[0055] Step 4: Lead out the two pigtails of the main fiber ring 9 and the two pigtails of the padding layer ring 10 from the fiber outlet;

[0056] Step 5: Prepare an erbium-doped fiber light source 6 with optical power control function, a 2×2 single-mode fiber coupler 7, an integrated optical modulator 8, a first photodetector 11, a fiber isolator 12, a 3×3 single-mode fiber coupler 13, a second photodetector 15, and a third photodetector 16; wherein the 2×2 single-mode fiber coupler 7 has two input pigtails, one output pigtail, and one output idle end; the integrated optical modulator 8 has one input pigtail and two output pigtails; the 3×3 single-mode fiber coupler 13 has three input pigtails, two output pigtails, and one output anti-return end 14; and the fiber isolator 12 has one input pigtail and one output pigtail.

[0057] Then, the two pigtails of the main fiber ring 9 are fused to the two output pigtails of the integrated optical modulator 8, the output pigtail of the erbium-doped fiber light source 6 is fused to one input pigtail of the 2×2 single-mode fiber coupler 7, the output end of the 2×2 single-mode fiber coupler 7 is fused to the input pigtail of the integrated optical modulator 8, and the other input pigtail of the 2×2 single-mode fiber coupler 7 is connected to the input end of the first photodetector 11; the input pigtail of the fiber isolator 12 is connected to the unused output end of the 2×2 single-mode fiber coupler 7, and finally, the two output pigtails of the 3×3 single-mode fiber coupler 13 are fused to the two pigtails of the fiber pad ring 10, the output pigtail of the fiber isolator 12 is fused to one input pigtail of the 3×3 single-mode fiber coupler 13, and the other two input pigtails of the 3×3 single-mode fiber coupler 13 are connected to the input ends of the second photodetector 15 and the third photodetector 16, respectively.

[0058] The full-temperature optical power stability of the erbium-doped fiber light source 6 is generally less than 1%, which avoids monitoring optical power fluctuations by splicing a photodetector at the output anti-return end 14, thus reducing the overall complexity of the system. The fiber isolator 12 prevents the optical signal returned from the fiber pad ring 10 from entering the photodetector 11 through the idle end of the 2×2 single-mode fiber coupler 7, thus preventing interference with the main gyroscope signal.

[0059] Step 6: Connect the output terminals of the first photodetector 11, the second photodetector 15, and the third photodetector 16 to the signal processing circuit 30 of the fiber optic gyroscope, respectively.

[0060] Step 7: Install the fiber optic ring fixing cavity, erbium-doped fiber light source 6, 2×2 single-mode fiber coupler 7, integrated optical modulator 8, first photodetector 11, fiber optic isolator 12, 3×3 single-mode fiber coupler 13, second photodetector 15 and third photodetector 16 at preset positions on the fiber optic gyroscope platform, and finally obtain the fiber optic gyroscope based on the 3×3 coupler.

[0061] The current signals output by the second photodetector 15 and the third photodetector 16 pass through the IV conversion circuit and the analog-to-digital conversion circuit in sequence. The signal processing circuit calculates the angular velocity information of the correction fiber optic gyroscope and compares it with the angular velocity information of the main fiber optic gyroscope in real time. If there is a difference in angular velocity, the angular velocity of the main fiber optic gyroscope is corrected.

[0062] Furthermore, this embodiment also provides the above-mentioned measurement method for a fiber optic gyroscope based on a 3×3 coupler, including the following steps:

[0063] Step 1: The main fiber loop 9 and the integrated optical modulator 8 form the first Sagnac interferometer, which is sensitive to the Sagnac phase difference caused by the input angular velocity in real time;

[0064] Step 2: The fiber pad ring 10 and the 3×3 single-mode fiber coupler 13 form a second Sagnac interferometer to sense the Sagnac phase difference caused by the input angular velocity in real time;

[0065] Step 3: The optical signal returned by the first Sagnac interferometer formed by the main fiber ring 9 and the integrated optical modulator 8 is transmitted to the first photodetector 11, and the optical signal returned by the second Sagnac interferometer formed by the fiber pad ring 10 and the 3×3 single-mode fiber coupler 13 is transmitted to the second photodetector 15 and the third photodetector 16.

[0066] Step 4: The first photodetector 11, the second photodetector 15, and the third photodetector 16 convert the optical signal into an electrical signal, which is then amplified by the IV conversion circuit and the analog-to-digital conversion circuit in sequence, and transmitted to the signal processing circuit 30.

[0067] Step 5: The signal processing circuit 30 calculates the angular velocity information of the gyroscope used for stripe correction and compares it with the angular velocity information of the main fiber optic gyroscope in real time. If an angular velocity error occurs, the angular velocity of the main fiber optic gyroscope is corrected.

Claims

1. A fiber optic gyroscope based on a 3×3 coupler, characterized in that: It includes a fiber optic gyroscope platform, a fiber optic ring fixing cavity disposed on the fiber optic gyroscope platform, and a main fiber optic ring (9) and a fiber pad ring (10) disposed in the fiber optic ring fixing cavity; the fiber pad ring (10) is the fiber optic ring of a gyroscope for stripe correction; It also includes an erbium-doped fiber light source (6), a 2×2 single-mode fiber coupler (7), an integrated optical modulator (8), a first photodetector (11), a fiber isolator (12), a 3×3 single-mode fiber coupler (13), a second photodetector (15), and a third photodetector (16); The two pigtails of the main fiber ring (9) are respectively connected to the two output pigtails of the integrated optical modulator (8), the output pigtail of the erbium-doped fiber light source (6) is connected to one input pigtail of the 2×2 single-mode fiber coupler (7), the output end of the 2×2 single-mode fiber coupler (7) is connected to the input pigtail of the integrated optical modulator (8), and the other input pigtail of the 2×2 single-mode fiber coupler (7) is connected to the input end of the first photodetector (11); the fiber isolator (12) The input pigtail of the 3×3 single-mode fiber coupler (13) is connected to the output idle end of the 2×2 single-mode fiber coupler (7); the two output pigtails of the 3×3 single-mode fiber coupler (13) are respectively fused to the two pigtails of the fiber pad ring (10); the output pigtail of the fiber isolator (12) is fused to one input pigtail of the 3×3 single-mode fiber coupler (13); and the other two input pigtails of the 3×3 single-mode fiber coupler (13) are respectively connected to the input ends of the second photodetector (15) and the third photodetector (16). The output terminals of the first photodetector (11), the second photodetector (15) and the third photodetector (16) are electrically connected to the signal processing circuit (30) of the fiber optic gyroscope, respectively. The fiber optic isolator (12) is used to prevent the optical signal returned by the fiber pad ring (10) from entering the photodetector (11) through the idle end of the output of the 2×2 single-mode fiber coupler (7) and interfering with the signal of the main gyroscope.

2. The fiber optic gyroscope based on a 3×3 coupler according to claim 1, characterized in that: The main fiber ring (9) is located outside the fiber pad ring (10), and the main fiber ring (9) and the fiber pad ring (10) have the same fiber output direction and position.

3. A fiber optic gyroscope based on a 3×3 coupler according to claim 2, characterized in that: The erbium-doped fiber light source (6) is an erbium-doped fiber light source with optical power control function.

4. A method for fabricating a fiber optic gyroscope based on a 3×3 coupler as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Prepare fiber optic winding fixture, fiber optic winding equipment, and main fiber and pad fiber of preset length. The main fiber and pad fiber have the same operating wavelength. Step 2: Use fiber optic winding fixtures and fiber optic winding equipment to wind and process the main fiber and the fiber pad layer fiber to obtain a combination of the main fiber ring (9) made from the main fiber and the fiber pad layer ring (10) made from the fiber pad layer fiber. Step 3: Prepare a circular fiber optic ring fixing cavity with fiber outlets on the inner ring sidewalls; glue and fix the combination of the main fiber optic ring (9) and the fiber pad ring (10) inside the fiber optic ring fixing cavity. Step 4: Lead out the two pigtails of the main fiber ring (9) and the two pigtails of the padding layer ring (10) from the fiber outlet; Step 5: Prepare an erbium-doped fiber light source (6), a 2×2 single-mode fiber coupler (7), an integrated optical modulator (8), a first photodetector (11), a fiber isolator (12), a 3×3 single-mode fiber coupler (13), a second photodetector (15), and a third photodetector (16), and connect them to the two pigtails of the main fiber ring (10) according to the preset connection method. Step 6: Connect the output terminals of the first photodetector (11), the second photodetector (15) and the third photodetector (16) to the signal processing circuit (30) of the fiber optic gyroscope, respectively. Step 7: Install the fiber optic ring fixing cavity, erbium-doped fiber light source (6), 2×2 single-mode fiber coupler (7), integrated optical modulator (8), first photodetector (11), fiber isolator (12), 3×3 single-mode fiber coupler (13), second photodetector (15) and third photodetector (16) at preset positions on the platform of the fiber optic gyroscope, and finally obtain the fiber optic gyroscope based on the 3×3 coupler.

5. The preparation method according to claim 4, characterized in that: In step 1, the optical fiber winding fixture includes a circular first baffle (1) and a second baffle (3), and a skeleton (2) disposed between the first baffle (1) and the second baffle (3). The radial cross section of the skeleton (2) is a ring, and its two ends are connected to the first baffle (1) and the second baffle (3) respectively. An arc-shaped first fiber guide groove (4) and a second fiber guide groove (5) are disposed on the inner side wall of the second baffle (3) between its outer edge and the skeleton (2). The first fiber guide groove (4) and the second fiber guide groove (5) are used to guide the two pigtails of the fiber pad ring (10).

6. The preparation method according to claim 5, characterized in that: The fiber optic winding equipment mentioned in step 2 is a winding machine. The specific steps of using fiber optic winding fixtures and fiber optic winding equipment to wind and process the main fiber and the fiber pad layer are as follows: The fiber winding fixture is fixed to the winding machine with screws. First, the fiber padding ring (10) is wound along the outer wall of the skeleton (2). After the winding is completed, the two pigtails of the fiber padding ring (10) are led out from the first fiber guide groove (4) and the second fiber guide groove (5) to the outer edge of the second baffle (3) and fixed with tape. The size of the first fiber guide groove (4) and the second fiber guide groove (5) is adapted to the fiber of the fiber padding ring (10) so that the inner side of the second baffle (3) is flat after the pigtails are put in. Then, the main fiber ring (9) is wound on the outside of the fiber padding ring (10) in the same way as the fiber padding ring (10), and the fiber output direction and position of the main fiber ring (9) and the fiber padding ring (10) are the same. Finally, the main fiber ring (9) and the fiber padding ring (10) are cured and de-skeletonized.

7. The preparation method according to claim 6, characterized in that: Step 5 specifically involves: Prepare an erbium-doped fiber light source (6) with optical power control function, a 2×2 single-mode fiber coupler (7), an integrated optical modulator (8), a first photodetector (11), a fiber isolator (12), a 3×3 single-mode fiber coupler (13), a second photodetector (15), and a third photodetector (16); wherein the 2×2 single-mode fiber coupler (7) has two input pigtails, one output pigtail, and one output idle end; the integrated optical modulator (8) has one input pigtail and two output pigtails; the 3×3 single-mode fiber coupler (13) has three input pigtails, two output pigtails, and one output anti-return end (14); and the fiber isolator (12) has one input pigtail and one output pigtail. Then, the two pigtails of the main fiber ring (9) are fused to the two output pigtails of the integrated optical modulator (8), the output pigtail of the erbium-doped fiber light source (6) is fused to one input pigtail of the 2×2 single-mode fiber coupler (7), the output end of the 2×2 single-mode fiber coupler (7) is fused to the input pigtail of the integrated optical modulator (8), and the other input pigtail of the 2×2 single-mode fiber coupler (7) is connected to the input end of the first photodetector (11); the fiber isolator (12) is connected to the input end of the first photodetector (11). The input pigtail is connected to the idle output end of the 2×2 single-mode fiber coupler (7); finally, the two output pigtails of the 3×3 single-mode fiber coupler (13) are fused to the two pigtails of the fiber pad ring (10), the output pigtail of the fiber isolator (12) is fused to one input pigtail of the 3×3 single-mode fiber coupler (13), and the other two input pigtails of the 3×3 single-mode fiber coupler (13) are connected to the input ends of the second photodetector (15) and the third photodetector (16), respectively.

8. A measurement method for a fiber optic gyroscope based on a 3×3 coupler as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: The main fiber loop (9) and the integrated optical modulator (8) form the first Sagnac interferometer, which is sensitive to the Sagnac phase difference caused by the input angular velocity in real time; Step 2: The fiber pad ring (10) and the 3×3 single-mode fiber coupler (13) form a second Sagnac interferometer to sense the Sagnac phase difference caused by the input angular velocity in real time; Step 3: The optical signal returned by the first Sagnac interferometer formed by the main fiber ring (9) and the integrated optical modulator (8) is transmitted to the first photodetector (11), and the optical signal returned by the second Sagnac interferometer formed by the padding fiber ring (10) and the 3×3 single-mode fiber coupler (13) is transmitted to the second photodetector (15) and the third photodetector (16). Step 4: The first photodetector (11), the second photodetector (15) and the third photodetector (16) convert the optical signal into an electrical signal, which is then amplified by the IV conversion circuit and the analog-to-digital conversion circuit in sequence and transmitted to the signal processing circuit (30). Step 5: The signal processing circuit (30) calculates the angular velocity information of the gyroscope used for stripe correction and compares it with the angular velocity information of the main fiber optic gyroscope in real time. If an angular velocity error occurs, the angular velocity of the main fiber optic gyroscope is corrected.

Images