Miniaturized three-axis optical fiber gyroscope optical path

Abstract

The invention discloses a miniaturized three-axis optical fiber gyroscope optical path which comprises a micro-optical array module and a plurality of optical fiber interferometer modules, and the micro-optical array module and the optical fiber interferometer modules are connected through mode filtering optical fibers with a certain length. The micro-optical array module is composed of a semiconductor light-emitting chip, four microcrystal lenses with different functions and three PD light detection chips made of InGaAs materials. The optical fiber interferometer module is composed of a Y waveguide, an optical fiber ring connected with the Y waveguide, and an optical fiber ring packaging structural member. According to the design, through overall arrangement of the micro-optical array, the optical path loss of light output by the semiconductor light-emitting chip to each PD optical detection chip is about 17dB and is lower than that of a single-axis optical path, and the signal-to-noise ratio of the three-axis integrated fiber-optic gyroscope can be improved. And under the same signal-to-noise ratio requirement, the requirements on the efficiency of the semiconductor light-emitting chip and the light source driving current are also relaxed, and the optical fiber light path design of the three-axis gyroscope can be realized by using the conventional light source parameters of the current single-axis light path.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing in optoelectronic technology, and more specifically to a miniaturized three-axis fiber optic gyroscope optical path. Background Technology

[0002] Fiber optic gyroscopes are a new generation of high-performance inertial angular velocity sensors based on the optical Sagnac effect. They possess significant advantages such as high precision, all-solid-state operation, and flexible structural design, making them the preferred instrument for inertial measurement and control systems. The optical components of a fiber optic gyroscope mainly consist of five discrete optical devices: a light source, fiber optic coupler, phase modulator (Y-waveguide), fiber optic loop, and PD photodetector. These devices require optical interconnection, leading to a complex manufacturing process and difficulty in controlling product consistency. Furthermore, this approach limits further cost reduction and increases the challenge of miniaturization.

[0003] Fiber optic gyroscopes are commonly used in attitude measurement and control, and inertial navigation. They require spatially orthogonal three-axis fiber optic gyroscopes that simultaneously sense angular velocity information in three degrees of freedom. These products are used in spacecraft such as satellites, military and civilian aircraft, guided bombs, and other applications, and there is also a need for miniaturization. A three-axis fiber optic gyroscope can employ three separate fiber optic paths, such as... Figure 1 As shown, a total of 15 fiber optic or optoelectronic devices are required. The traditional single-axis fiber optic gyroscope optical path, such as... Figure 1 As shown, there is a loss of about 18dB from the light source to the PD photodetector.

[0004] To reduce the power consumption of the three-axis fiber optic gyroscope and facilitate the isolation design between the heat source and the sensitive meter, the most mature dual-fiber tapered coupling device is adopted. The three-axis integrated fiber optic path can be designed as follows: Figure 2 As shown, a total of 12 fiber optic devices or optoelectronic devices are required.

[0005] With advancements in fused biconical fiber (FBF) device technology, triaxial integrated fiber optic paths can be further modified to consist of 11 optical fibers or optoelectronic devices, such as... Figure 3 As shown. The three-axis fiber optic path of the shared light source is as follows. Figure 2 and Figure 3 As shown, there is approximately 23dB of loss when the light source reaches each PD photodetector.

[0006] Taking the three-axis integrated fiber optic path 2 with a shared light source as an example, its working principle is introduced as follows: The light emitted by the broadband light source is split into three beams of equal power by a 1:1:1 fiber coupler, which then enter three 1:1 fiber couplers respectively. The light entering 1:1 fiber coupler 1 is split into two paths. One path enters the Y-waveguide for polarization and is split into two beams, which propagate clockwise and counterclockwise along the fiber loop and return to the Y-waveguide to achieve interference. The phase difference between the two interfering beams is related to the rotational speed of the loop optical path and is called the Sagnac phase difference, which can be used... Represented as:

[0007]

[0008] In the formula, Let be the equivalent radius of the ring optical path. The length of the ring optical path, The average wavelength of the light source in a statistical sense (wavelength in vacuum). The speed of light in a vacuum. The rotational speed of the ring optical path relative to inertial space. The interference light is output through the single-ended fiber of Y waveguide 1 to 1:1 fiber coupler 1, and then to PD photodetector 1 for subsequent signal processing. The other path of light from the broadband light source, after being split by 1:1 fiber coupler 1, is the monitoring end of the fiber optic path, where anti-reflection extinction treatment is performed, and it can also be connected to the PD photodetector.

[0009] The working status of the second and third optical paths in the figure is the same as that of the first axis. Summary of the Invention

[0010] This invention, based on a modular design approach, aims to solve the production efficiency and size issues of the optical path in a three-axis integrated fiber optic gyroscope. The details and overall structural design of the fiber optic path involved constitute the inventive contribution of this invention. Addressing the problems of numerous fiber optic and optoelectronic devices in current three-axis integrated fiber optic gyroscopes, the large number of fiber optic pigtails requiring processing, splicing, and coiling, resulting in low product reliability and difficulty in controlling size and cost after assembly, this invention proposes a modular design and solution. The solution designs the optical path of the three-axis integrated fiber optic gyroscope as two types with a total of four standard optical components, requiring only simple connections, which can significantly improve production efficiency. Simultaneously, the designed micro-optical array module also makes the three-axis fiber optic gyroscope structure compact and reliable.

[0011] The technical solution of this invention is as follows:

[0012] A miniaturized three-axis fiber optic gyroscope optical path includes one micro-optical array module and multiple fiber optic interferometer modules. The micro-optical array module and the fiber optic interferometer modules are connected by a mode filtering fiber of a certain length, generally not less than 1 meter.

[0013] The micro-optical array module consists of one semiconductor light-emitting chip, four microcrystalline lenses with different functions, and three InGaAs PD photodetector chips.

[0014] The fiber optic interferometer module consists of a Y-waveguide, a fiber optic ring connected to the Y-waveguide, and a fiber optic ring encapsulation structure.

[0015] The light output from the semiconductor light-emitting chip is transmitted to the first lens 11, generating 33% transmitted light and 67% reflected light. The 67% reflected light propagates to the second lens 12, generating 50% transmitted light and 50% reflected light. The 50% transmitted light propagates to the third lens 13, generating nearly 100% transmission. The 33% transmitted light from the first lens 11 passes through the first mode-filtering fiber 21 and propagates to the first fiber optic interferometer module 31. The interference light wave returned from the first fiber optic interferometer module 31 passes through the first mode-filtering fiber 21 again, propagates to the first lens 11, and is nearly 100% reflected before propagating to the first PD photodetector chip 41 for subsequent electrical signal processing. The 50% reflected end of the second lens 12 propagates to the fourth lens 14 and is nearly 100% transmitted. The light then passes through the second mode-filtering fiber 22 with mode filtering function and propagates to the second fiber optic interferometer. Module 32; Similar to the first fiber interferometer module, the return light passes through the second mode-filtering fiber 22 with mode filtering, propagates to the fourth lens 14, and is nearly 100% reflected to the second InGaAs PD photodetector chip 42 for subsequent electrical signal processing; the 100% transmitted light from the third lens 13 also passes through the third mode-filtering fiber 23 with mode filtering function, propagates to the third single-fiber interferometer module 33, and the return light also passes through the third mode-filtering fiber 23 with mode filtering, propagates to the third lens 13, and is nearly 100% reflected to the third InGaAs PD photodetector chip 43 for subsequent electrical signal processing; a single-mode fiber is used between the micro-optical array module and the fiber interferometer module to filter out the high-order mode components during waveguide transmission, to ensure the zero-bias reciprocity characteristic of the fiber optic gyroscope and reduce zero-position error.

[0016] The optical path connection between the micro-optical array module and the fiber interferometer module is achieved by fiber optic fusion splicing or fiber optic oblique coupling followed by adhesive fixation.

[0017] The 3-axis fiber optic interferometer module is directly fixed to the three orthogonal planes of the attitude measurement system or inertial navigation system's metal structure. Alternatively, it can be non-orthogonal, but can be projected onto three orthogonal axes. The micro-optical array module and related circuitry are fixed to the attitude measurement system's base structure, or to a thermally conductive structural component of the base.

[0018] The micro-optical array module is encapsulated in a housing of approximately 40mm × 20mm × 10mm.

[0019] In the first fiber interferometer module 31, the output light from the first fiber 21 is sent to the Y waveguide. After polarization filtering, 1:1 beam splitting, and phase modulation in the Y waveguide, the light wave is transmitted clockwise and counterclockwise from the two pigtails of the Y waveguide to the fiber ring, respectively. After passing through the entire fiber ring, it is transmitted back to the two pigtails of the Y waveguide, enters the Y waveguide for secondary phase modulation and polarization filtering, and is then combined and interfered. The interference light is transmitted to the first fiber 21 through the single end of the Y waveguide.

[0020] The technical effects and advantages of this invention are as follows:

[0021] 1) Traditional single-axis fiber optic gyroscope optical paths, such as Figure 1 As shown, there is approximately 18dB of loss from the light source to the PD photodetector. The triaxial fiber optic path sharing the light source is as follows: Figure 2 and Figure 3 As shown, the light source experiences approximately 23dB loss when reaching each PD photodetector. However, this design, through the coordinated arrangement of the micro-optical array, achieves an optical path loss of around 17dB for the light output from the semiconductor light-emitting chip to each PD photodetector chip, which is lower than that of a single-axis optical path. This improves the signal-to-noise ratio (SNR) of the triaxial integrated fiber optic gyroscope. Under the same SNR requirements, the requirements for the efficiency of the semiconductor light-emitting chip and the light source drive current are also relaxed, allowing the use of conventional light source parameters from current single-axis optical paths to achieve the fiber optic path design of the triaxial gyroscope.

[0022] 2) The micro-optical array module can be packaged in a housing of about 40mm×20mm×10mm. It is small in size and light in weight. It features a balanced three-optical-path design, a mode-filtering pigtail, and a mature manufacturing process, making it convenient for mass production.

[0023] 3) Modular fiber interferometer design: different interferometer modules can be freely combined with micro-optical array modules to realize three-axis fiber optical paths with different performance requirements. Moreover, the optical path connection is simple and highly reliable, which can greatly improve the assembly and production efficiency of three-axis fiber optic gyroscopes.

[0024] 4) The micro-optical array module and the fiber interferometer module are connected by flexible optical fiber, which realizes the physical isolation between the heat source in the optical path and the fiber interferometer module that is sensitive to rotation speed. This is beneficial to improving the power-on stability and overall temperature adaptability of the three-axis fiber optical path, and also facilitates the rational layout of the integrated design of the gyroscope and inertial navigation system. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of three separate optical fiber paths;

[0026] Figure 2 A schematic diagram of a three-axis integrated fiber optic path with a shared light source;

[0027] Figure 3Schematic diagram of a three-axis integrated fiber optic path 2 for a shared light source;

[0028] Figure 4 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] like Figure 4 As shown, the miniaturized three-axis fiber optic gyroscope of the invention comprises four parts and two types of optical modules. The two types of modules are connected by a mode-filtering fiber of a certain length, generally not shorter than 1 meter.

[0032] The two optical modules are a micro-optical array module and a fiber optic interferometer module.

[0033] The aforementioned micro-optical array module replaces the discrete components in the original optical path, such as the broadband light source, multiple fiber couplers, and PD photodetectors, with a micro-optical array that has the same function, and then packages them to form a miniaturized all-in-one optoelectronic device. The micro-optical array module includes one semiconductor light-emitting chip, four microcrystalline lenses with different functions, and three InGaAs PD photodetector chips.

[0034] The fiber optic interferometer module includes a Y-waveguide (phase modulator), a fiber optic ring of a certain size and length, and a fiber optic ring encapsulation structure (μ-alloy material or hard aluminum material).

[0035] Furthermore, the four microcrystalline lenses with different functions are: first lens 11, second lens 12, third lens 12, and fourth lens 14; the three PD photodetector chips are: first PD photodetector chip 41, second PD photodetector chip 42, and third PD photodetector chip 43; the number of fiber optic interferometer modules is three: first fiber optic interferometer module 31, second fiber optic interferometer module 32, and third fiber optic interferometer module 22; wherein:

[0036] The miniaturized three-axis fiber optic gyroscope optical path operates as follows: Light output from the semiconductor light-emitting chip is transmitted to the first lens 11, generating 33% transmitted light and 67% reflected light. The 67% reflected light propagates to the second lens 12, generating 50% transmitted light and 50% reflected light. The 50% transmitted light propagates to the third lens 13, generating nearly 100% transmission. The 33% transmitted light from the first lens 11 passes through the first mode filter fiber 21 and propagates to the first fiber interferometer module 31. The internal operation of the first fiber interferometer module 31 is similar to the original three-axis integrated fiber optic path. The returned interference light wave passes through the first mode filter fiber 21 again, propagates to the first lens 11, and is nearly 100% reflected before propagating to the first InGaAs material PD photodetector chip 41 for subsequent electrical signal processing. The 50% reflected end of the second lens 12 propagates to the fourth lens 14 and is nearly 100% transmitted. The light then passes through the second mode filter fiber 22 with mode filtering function and propagates to the fiber interferometer module 2. Similar to the first fiber interferometer module, the return light passes through the mode-filtered pigtail 22 and propagates to the fourth lens 14. It is then nearly 100% reflected and propagates to the second InGaAs PD photodetector chip 42 for subsequent electrical signal processing. The 100% transmitted light from the third lens 13 also passes through the mode-filtered third mode-filtered fiber 23 and propagates to the third single-fiber interferometer module 33. Similarly, the return light passes through the mode-filtered third pigtail 23 and propagates to the third lens 13. It is then nearly 100% reflected and propagates to the third InGaAs PD photodetector chip 43 for subsequent electrical signal processing. A single-mode fiber is used between the micro-optical array module and the fiber interferometer module to filter out high-order mode components during waveguide transmission, ensuring the zero-bias reciprocity characteristic of the fiber optic gyroscope and reducing null-position error.

[0037] Example 2

[0038] 1) Micro-optical array module

[0039] according to Figure 4 The micro-optical array module shown is constructed and manufactured. Its internal optical path propagation and working process are as follows:

[0040] Optical path 1:

[0041] Forward optical path: The light wave output by the semiconductor light-emitting chip is given to the first lens 11, and after 33% of the light wave is transmitted, it is output to the first mode filter fiber 21;

[0042] Reverse optical path: The light wave returned by the first mode filter fiber 21 is transmitted to the first lens 11 and reflected to the first PD photoelectric detection chip 41, which converts it into an electrical signal (for subsequent signal processing).

[0043] Optical path 2:

[0044] Forward optical path: The light wave output by the semiconductor light-emitting chip is reflected by the first lens 11, and then output to the second lens 12. After 50% of the light wave is reflected, it is output to the second mode filter fiber 22.

[0045] Reverse optical path: The light wave returned by the second mode filter fiber 22 is transmitted to the fourth lens 14 and reflected to the second PD photodetector chip 42, which converts it into an electrical signal (for subsequent signal processing).

[0046] Optical path 3:

[0047] Forward optical path: The light wave output by the semiconductor light-emitting chip is reflected by the first lens 11, and then output to the second lens 12. After 50% of the light wave is transmitted, it is output to the third mode filter fiber 23.

[0048] Reverse optical path: The light wave returned by the mode filter fiber 23 is transmitted to the third lens 13 and reflected to the third PD photodetector chip 43, which converts it into an electrical signal (for subsequent signal processing).

[0049] The entire optical path is built and fixed on an insulating substrate, and the semiconductor light-emitting chip and PD photodetector are connected to the module's response pins via gold wire bonding leads.

[0050] 2) Fiber Optic Interferometer Module

[0051] according to Figure 4 The fiber optic interferometer module shown has three identical optical paths. Taking the first fiber optic interferometer module 31 as an example, the optical wave transmission and operation process is as follows:

[0052] Taking the first fiber interferometer module 31 as an example, the output light of the first mode filter fiber 21 is sent to the Y waveguide. After polarization filtering, 1:1 beam splitting and phase modulation are performed in the Y waveguide, the light wave is transmitted to the fiber ring from the two pigtails of the Y waveguide in clockwise and counterclockwise directions, respectively. After passing through the entire fiber ring, it is transmitted back to the two pigtails of the Y waveguide, enters the Y waveguide for secondary phase modulation and polarization filtering, and is then combined and interfered. The interference light is transmitted to the first mode filter fiber 21 through the single end of the Y waveguide.

[0053] The interference light signal at this time contains the rotational speed information of the module relative to the inertial space.

[0054] The second and third fiber optic interferometer modules operate on similar principles.

[0055] The fiber optic ring is bonded to the encapsulated metal bracket using adhesives such as epoxy resin. The Y-waveguide is fixed to the integrated metal base structure using nylon screws. The pigtail is fixed to the upper edge of the fiber optic ring or the surface of the metal bracket using UV-cured adhesive. The metal bracket can be a laser-welded closed structure or an open structure.

[0056] 3) Overall implementation of the three-axis fiber optic gyroscope optical path

[0057] like Figure 4 The optical path of the three-axis fiber optic gyroscope shown is connected between the micro-optical array module and the fiber optic interferometer module by fiber optic fusion splicing or fiber optic oblique coupling and then fixing with adhesive.

[0058] Among them, the 3-axis fiber interferometer module is directly fixed on the three orthogonal planes of the attitude measurement system or the metal structure of the inertial navigation system (it can also be non-orthogonal, but it can be projected onto the three orthogonal axes, such as the northeast sky), while the micro-optical array module (and related circuits) is generally fixed on the base structure of the attitude measurement system, or on the base structure with good thermal conductivity, so as to facilitate direct heat dissipation of the carrier. After power-on, it can also achieve rapid temperature balance.

[0059] Example 3

[0060] Based on the design principles, this design can also be easily extended to a 4-axis or more axis optical path redundancy design.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A miniaturized three-axis fiber optic gyroscope optical path, characterized in that: It includes one micro-optical array module and multiple fiber interferometer modules. The micro-optical array module and the fiber interferometer modules are connected by a mode filtering fiber of a certain length. The micro-optical array module consists of one semiconductor light-emitting chip, four microcrystalline lenses with different functions, and three PD photodetector chips; The fiber optic interferometer module consists of a Y-waveguide, a fiber optic ring connected to the Y-waveguide, and a fiber optic ring encapsulation structure.

2. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: The four microcrystalline lenses with different functions are: the first lens, the second lens, the third lens, and the fourth lens; the three PD photodetector chips are: the first PD photodetector chip, the second PD photodetector chip, and the third PD photodetector chip; the three fiber optic interferometer modules are: the first fiber optic interferometer module, the second fiber optic interferometer module, and the third fiber optic interferometer module; wherein: The light output from the semiconductor light-emitting chip is transmitted to the first lens, generating 33% transmitted light and 67% reflected light. The 67% reflected light propagates to the second lens, generating 50% transmitted light and 50% reflected light. The 50% transmitted light propagates to the third lens, generating nearly 100% transmission. The 33% transmitted light from the first lens passes through the first mode filter fiber and propagates to the first fiber optic interferometer module. The interference light wave returned from the first fiber optic interferometer module passes through the first mode filter fiber again, propagates to the first lens, and is nearly 100% reflected before propagating to the first PD photodetector chip for subsequent electrical signal processing. The 50% reflected end of the second lens propagates to the fourth lens and is nearly 100% transmitted. The transmitted light passes through a second mode-filtered fiber with mode filtering function and propagates to the second fiber interferometer module. Similar to the first fiber interferometer module, the returned light passes through the second mode-filtered fiber with mode filtering function and propagates to the fourth lens. It is nearly 100% reflected and propagates to the second PD photodetector chip made of InGaAs material for subsequent electrical signal processing. The 100% transmitted light from the third lens also passes through a third mode-filtered fiber with mode filtering function and propagates to the third single-fiber interferometer module 33. Similarly, the returned light passes through the third mode-filtered fiber with mode filtering function and propagates to the third lens. It is nearly 100% reflected and propagates to the third PD photodetector chip for subsequent electrical signal processing.

3. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: The optical path connection between the micro-optical array module and the fiber interferometer module is achieved by fiber optic fusion splicing or fiber optic oblique coupling followed by adhesive fixation.

4. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: The 3-axis fiber interferometer module is directly fixed on the three orthogonal planes of the attitude measurement system or the metal structure of the inertial navigation system; it can also be non-orthogonal, but can be projected onto three orthogonal axes. The micro-optical array module and related circuits are fixed on the base structure of the attitude measurement system, or on a structural component with good thermal conductivity to the base.

5. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: The micro-optical array module is encapsulated in a housing of approximately 40mm × 20mm × 10mm.

6. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: In the first fiber interferometer module, the output light from the first fiber is fed to the Y-waveguide. After polarization filtering, 1:1 beam splitting, and phase modulation in the Y-waveguide, the light wave is transmitted clockwise and counterclockwise from the two pigtails of the Y-waveguide to the fiber ring, respectively. After passing through the entire fiber ring, it is transmitted back to the two pigtails of the Y-waveguide, enters the Y-waveguide for secondary phase modulation and polarization filtering, and is then combined and interfered. The interference light is transmitted to the first fiber through the Y-waveguide at one end.

7. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: A single-mode fiber is used between the micro-optical array module and the fiber interferometer module to filter out the high-order mode components during waveguide transmission, thereby ensuring the zero-bias reciprocity characteristic of the fiber optic gyroscope and reducing zero-position error.

8. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: The entire optical path is built and fixed on an insulating substrate, and the semiconductor light-emitting chip and PD photodetector are connected to the module's response pins via gold wire bonding leads.

9. The optical path of a miniaturized three-axis fiber optic gyroscope according to claim 1, characterized in that: The fiber optic ring is bonded to the encapsulated metal bracket using adhesives such as epoxy resin. The Y-waveguide is fixed to the integrated metal base structure with nylon screws. The pigtail is fixed to the upper edge of the fiber optic ring or the surface of the metal bracket with UV-cured adhesive. The metal bracket can be a closed structure welded by laser or an open structure.

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