Special integrated device for fiber-optic gyroscope

Abstract

The invention discloses a special integrated device for a fiber-optic gyroscope, which comprises a wide-spectrum light source, two beam shaping modules, four spot-size converters, two couplers, three polarizers, a modulation electrode, an optical path adjustment waveguide and a detector, and forms two input and output ports through a second spot-size converter and a third spot-size converter, the connector is used for connecting a fiber-optic gyroscope ring. The fiber-optic gyroscope has the advantages that the light source, the coupler, the Y waveguide and the detector which are required by a traditional fiber-optic gyroscope are integrated into one device, so that the size of the fiber-optic gyroscope is greatly reduced, and the reliability of the fiber-optic gyroscope is improved.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber sensing applications, and in particular relates to an integrated special device for optical fiber gyroscopes. Background Art

[0002] Fiber optic gyroscope is a kind of all-solid-state gyroscope based on the optical Sagnac effect. It is the basic core component for realizing autonomous navigation, positioning and attitude determination of the carrier. Compared with mechanical gyroscope, optical gyroscope has the advantages of wide accuracy range, no rotating and friction parts, small size, light weight and high reliability. After nearly sixty years of development, fiber optic gyroscope has gradually become the mainstream device of inertial navigation system. It is now widely used in aviation, aerospace, navigation, weapons, energy and other fields, forming a full coverage from commercial and tactical medium and low precision applications to navigation and strategic medium and high precision applications. Under the new situation, the new generation of inertial navigation system continues to develop towards miniaturization and low cost, which puts higher and higher requirements on the comprehensive performance of gyroscope such as volume, accuracy and cost.

[0003] The interferometric optical gyroscope is mainly composed of a wide-spectrum light source, an isolator, a coupler, a Y-waveguide that integrates beam splitting and combining, polarization generation and analysis, and phase modulation functions, a passive sensitive loop, and a detector. At present, the interferometric optical gyroscope system is mostly built with discrete devices, and the devices are coupled through optical fibers. By building a system with discrete devices, the device with the best performance can be freely selected, but it is inevitable to introduce factors such as end face reflection, coupling loss, and polarization noise caused by axis error, which reduces the performance of the device. In addition, the system built with discrete devices increases the cost of manual coupling and cannot be mass-produced. At the same time, due to the large size of independently packaged optical devices and the fiber optic loops of hundreds or thousands of meters, it is difficult to miniaturize the traditional fiber optic gyroscope. Therefore, it is urgent to explore new technical solutions to achieve the effective integration of different functions of the optical path, greatly reduce the volume of the gyroscope optical path, improve process compatibility, and reduce the manufacturing cost of the device. Summary of the invention

[0004] The present invention aims at solving the deficiencies of the prior art and proposes a fiber optic gyroscope integrated special device.

[0005] One of the above objects of the present invention is achieved by the following technical solution:

[0006] An integrated special device for optical fiber gyroscope, comprising a wide-spectrum light source, a first beam shaping module, a second beam shaping module, a first mode spot converter, a second mode spot converter, a third mode spot converter, a fourth mode spot converter, a first coupler, a second coupler, a first polarizer, a second polarizer, a third polarizer, a modulation electrode, an optical path adjustment waveguide and a detector;

[0007] Light transmission is achieved between the wide-spectrum light source and the first mode spot converter, and between the detector and the fourth mode spot converter through free space; light transmission is achieved between the first mode spot converter and the second mode spot converter, between the first mode spot converter and the third mode spot converter, between the second mode spot converter and the fourth mode spot converter, and between the third mode spot converter and the fourth mode spot converter through optical waveguides;

[0008] The broadband light source is used to generate highly polarized light;

[0009] The first beam shaping module is used to shape the high-polarization light so that the optical mode field is transformed into an optical mode field size corresponding to the mode spot converter;

[0010] The first mode spot converter is used to convert the outbound light output by the first beam shaping module into an optical mode field matching the size of the optical waveguide and then enter the optical waveguide;

[0011] The first coupler is used to transmit the outgoing light to the first polarization filter; and to couple the return light to the fourth spot converter;

[0012] The first polarization filter is used to perform polarization filtering on the outgoing light and the return light, filter out the TM mode, and retain the TE mode;

[0013] The second coupler is used to split the outbound light into two light beams with equal power for output, and to combine the two return light beams;

[0014] The modulation electrode realizes optical phase modulation on both the two outgoing light beams and the two returning light beams by applying voltage;

[0015] The second polarizer and the third polarizer are respectively used for performing a second polarization filtering on the two outgoing light beams after the optical phase modulation and for performing a second polarization filtering on the two returning light beams;

[0016] The optical path adjustment waveguide is used to adjust the optical path of a beam of outgoing light after the second polarization filtering and to adjust the optical path of a beam of return light;

[0017] The second mode spot converter is used to convert a beam of outgoing light after optical path modulation into an optical mode field matching the optical fiber mode field to output the outgoing light, and to input a beam of return light; it is provided with an outgoing light output interface and a return light input interface for connecting to the fiber optic gyroscope ring;

[0018] The third mode spot converter is used to convert another beam of outbound light after the second polarization filtering into an optical mode field matching the optical fiber mode field to achieve the output of the outbound light, and to achieve the input of another beam of return light; it is provided with an outbound light output interface and a return light input interface for connecting to the fiber optic gyroscope ring;

[0019] The fourth mode spot converter is used to perform optical mode field conversion on the return light output by the first coupler;

[0020] The second beam shaping module is used to further shape the return light output by the fourth spot converter;

[0021] The detector is used to detect the light intensity information of the return light output by the second beam shaping module.

[0022] Moreover, the wide spectrum light source is a high polarization light source, the TE mode power is greater than the TM mode power, the polarization degree is greater than 10 dB, and the spectrum width is greater than 40 nm.

[0023] Furthermore, the first beam shaping module is composed of two micro lenses placed in parallel, and the second beam shaping module is composed of one micro lens.

[0024] Moreover, the first polarizer is a bent waveguide polarizer, which is used to realize the polarization filtering function and optical waveguide steering of the device.

[0025] Moreover, the second polarizer and the third polarizer are waveguide coupled polarizers, whose two ends are strip waveguide input and output ends, and the middle is a hybrid waveguide coupled polarization section. The hybrid waveguide coupled polarization section is a three-layer structure, the bottom layer of the waveguide high refractive index material is lithium niobate, the middle layer of low refractive index material is silicon dioxide, and the upper metal layer is made of metal chromium.

[0026] Moreover, the difference between the optical path of the optical path adjustment waveguide and the optical path of the straight waveguide is greater than the coherence length of the wide-spectrum light source.

[0027] Moreover, the coupler is a multimode interference coupler or a Y-branch coupler.

[0028] Moreover, the modulation electrode adopts a push-pull structure.

[0029] Moreover, the pattern spot converter adopts a conical structure.

[0030] Moreover, the optical waveguide, the two couplers, the first polarizer, and the four spot converters are all made of lithium niobate material.

[0031] The advantages and positive effects of the present invention are:

[0032] 1. Compared with the traditional discrete fiber optic gyroscope system, the fiber optic gyroscope integrated dedicated device of the present invention integrates the four discrete optical devices required by the fiber optic gyroscope in the traditional technical solution into one device, greatly reducing the size of the device while maintaining the original function.

[0033] 2. The fiber optic gyroscope integrated special device of the present invention realizes the fiber-free device, avoids the end face reflection, coupling loss introduced by the fiber connection between devices, and polarization noise caused by axis error, thereby improving performance.

[0034] 3. The fiber optic gyroscope integrated special device of the present invention reduces the cost of manual coupling and can be mass-produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the structure of the integrated special device of the fiber optic gyroscope of the present invention;

[0036] Figure 2 It is a schematic diagram of the structure of the bent waveguide polarizer of the present invention;

[0037] Figure 3 It is a schematic diagram of the structure of the waveguide-coupled polarizer of the present invention;

[0038] Figure 4 It is a schematic diagram of the structure of the Y-branch coupler of the present invention;

[0039] Figure 5 It is a schematic diagram of the structure of the pattern spot converter of the conical structure of the present invention. DETAILED DESCRIPTION

[0040] The structure of the present invention is further described below with reference to the accompanying drawings and by way of examples. It should be noted that the present examples are descriptive rather than restrictive.

[0041] The present invention provides a fiber optic gyroscope integrated special device, see Figure 1-Figure 4 The invention point is: it includes a broadband light source 1, a first beam shaping module 2, a second beam shaping module 14, a first spot converter 3, a second spot converter 11, a third spot converter 12, a fourth spot converter 13, a first coupler 4, a second coupler 6, a first polarizer 5, a second polarizer 8, a third polarizer 9, a modulation electrode 7, an optical path adjustment waveguide 10 and a detector 15.

[0042] During operation, the high polarization light (constituting the outbound light) emitted by the wide-spectrum light source 1 is shaped by the first beam shaping module 2, and the optical mode field is transformed into the optical mode field size corresponding to the mode spot converter. The shaped outbound light is converted by the first mode spot converter 3 into an optical mode field matching the size of the optical waveguide and then enters the optical waveguide. After passing through the first coupler 4, the first polarizer 5 performs polarization filtering to filter out the TM mode and retain the TE mode, thereby improving the extinction ratio of the light. Subsequently, the light is divided into two outbound lights of equal power through the second coupler 6. After applying a voltage to the modulation electrode 7, the optical phases of the two outbound lights are modulated. The two modulated outbound lights are respectively passed through the second polarizer 8 and the third polarizer 9 to achieve a second polarization filtering, thereby further improving the extinction ratio. One of the outbound lights is converted by the second mode spot converter 11 into an optical mode field matching the optical fiber mode field after passing through the optical path adjustment waveguide 10 to achieve optical path adjustment. In the application of this integrated special device, the second mode spot converter 11 will be connected to one end of the optical fiber loop of the optical fiber gyroscope. Another outbound light beam is converted into an optical mode field matching the optical fiber mode field by the third spot mode converter 12. In the application of the present integrated special device, the third spot mode converter 12 will be connected to the other end of the optical fiber ring of the optical fiber gyroscope. After the two outbound light beams are transmitted in the optical fiber ring, they return and enter the optical waveguide light path again through the third spot mode converter 12 and the second spot mode converter 11 respectively. After passing through the third polarizer 9, the second polarizer 8 and the modulation electrode 7 respectively, the two light beams are combined into a return light beam by the second coupler 6. The combined return light passes through the first polarizer 5 and is coupled to the fourth spot mode converter 13 by the first coupler 4. After the fourth spot mode converter 13 performs optical mode field conversion, it enters the second beam shaping module 14 for further shaping, and finally the light intensity information is detected by the detector 15. Among them, the light between the wide-spectrum light source 1 and the first mode spot converter 3, and between the detector 15 and the fourth mode spot converter 14 is transmitted in the free space, and the light between the first mode spot converter 3 and the second mode spot converter 11, between the first mode spot converter 3 and the third mode spot converter 12, between the second mode spot converter 11 and the fourth mode spot converter 13, and between the third mode spot converter 12 and the fourth mode spot converter 13 is transmitted in the optical waveguide;

[0043] In this embodiment, the first beam shaping module 2 is composed of two parallel placed micro lenses, and the second beam shaping module 14 is composed of one micro lens, which adjusts the shape of the outgoing light spot to improve the coupling efficiency;

[0044] In this embodiment, a high polarization light source is used as a wide spectrum light source, the TE mode power is greater than the TM mode power, the polarization degree is greater than 10dB, and the spectrum width is greater than 40nm, providing a light source basis for the high extinction ratio of the entire device;

[0045] In this embodiment, the first polarizer 5 is a curved waveguide type polarizer, as shown in FIG. (2), by utilizing the different effective refractive indexes of the TM mode and the TE mode, a polarization waveguide is added outside the transmission waveguide to realize the polarization filtering function of the device, thereby improving the extinction ratio on the basis of a high extinction ratio light source, and at the same time, the curved waveguide is used for optical waveguide steering to reduce the volume of the entire device;

[0046] In this embodiment, the second polarizer 8 and the third polarizer 9 are waveguide-coupled polarizers, as shown in Figure (3), the waveguide has a high refractive index material at the bottom, silicon dioxide is a low refractive index material in the middle, and the metal layer on the top is chromium, which has a large absorption loss. The whole can be divided into three parts, with the two ends being the input / output ends of the strip waveguide and the middle being the hybrid waveguide coupling polarization section. Due to the special waveguide structural parameters, when the signal light is transmitted, the TE mode is transmitted along the strip waveguide, the TM mode is efficiently separated from the TE mode, and is completely coupled into the hybrid waveguide on both sides, where it is completely absorbed and lost. Finally, only the TE mode can pass through, achieving the polarization effect, realizing polarization filtering, and further improving the extinction ratio of the device;

[0047] In this embodiment, the difference between the optical path adjustment waveguide optical path between the second polarizer and the second spot converter and the straight waveguide optical path between the third polarizer and the third spot converter exceeds 200 μm, which is much larger than the coherence length of the light source, effectively reducing the backscattering noise generated when the device is applied to the gyroscope; the coupler adopts a multimode interference coupling structure or a Y-branch coupler to realize the beam splitting / combining function, as shown in Figure (4); the modulation electrode adopts a push-pull structure to reduce the modulation driving voltage; the spot converter adopts a conical structure to achieve mode field matching, as shown in Figure (5). The optical waveguide, coupler, polarizer, and spot converter are all made of lithium niobate material.

[0048] In summary, the fiber optic gyroscope integrated dedicated device in the embodiment of the present invention realizes the full integration of the fiber optic gyroscope optical path devices, and has the functions of light emission, beam splitting, polarization, modulation, detection, etc. of discrete devices, which helps to realize a miniaturized, low-cost, and highly reliable micro-fiber gyroscope.

Claims

1. A fiber optic gyroscope integrated special device, characterized in that: It includes a broadband light source, a first beam shaping module, a second beam shaping module, a first spot converter, a second spot converter, a third spot converter, a fourth spot converter, a first coupler, a second coupler, a first polarizer, a second polarizer, a third polarizer, a modulation electrode, an optical path adjustment waveguide and a detector; Light transmission is achieved between the wide-spectrum light source and the first mode spot converter, and between the detector and the fourth mode spot converter through free space; light transmission is achieved between the first mode spot converter and the second mode spot converter, between the first mode spot converter and the third mode spot converter, between the second mode spot converter and the fourth mode spot converter, and between the third mode spot converter and the fourth mode spot converter through optical waveguides; The broadband light source is used to generate highly polarized light; The first beam shaping module is used to shape the high-polarization light so that the optical mode field is transformed into an optical mode field size corresponding to the mode spot converter; The first mode spot converter is used to convert the outbound light output by the first beam shaping module into an optical mode field matching the size of the optical waveguide and then enter the optical waveguide; The first coupler is used to transmit the outgoing light to the first polarizer filter; and to couple the return light to the fourth spot converter; The first polarization filter is used to perform polarization filtering on the outgoing light and the return light, filter out the TM mode, and retain the TE mode; The second coupler is used to split the outbound light into two light beams with equal power for output, and to combine the two return light beams; The modulation electrode realizes optical phase modulation on both the two outgoing light beams and the two returning light beams by applying voltage; The second polarizer and the third polarizer are respectively used for performing a second polarization filtering on the two outgoing light beams after the optical phase modulation and for performing a second polarization filtering on the two returning light beams; The optical path adjustment waveguide is used to adjust the optical path of a beam of outgoing light after the second polarization filtering and to adjust the optical path of a beam of return light; The second mode spot converter is used to convert a beam of outgoing light after optical path modulation into an optical mode field matching the optical fiber mode field to output the outgoing light, and to input a beam of return light; It is provided with an outbound optical output interface and a return optical input interface for connecting the fiber optic gyroscope ring; The third mode spot converter is used to convert another beam of outbound light after the second polarization filtering into an optical mode field matching the optical fiber mode field to achieve the output of the outbound light, and to achieve the input of another beam of return light; it is provided with an outbound light output interface and a return light input interface for connecting to the fiber optic gyroscope ring; The fourth mode spot converter is used to perform optical mode field conversion on the return light output by the first coupler; The second beam shaping module is used to further shape the return light output by the fourth spot converter; The detector is used to detect the light intensity information of the return light output by the second beam shaping module.

2. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The wide spectrum light source is a high polarization light source, the TE mode power is greater than the TM mode power, the polarization degree is greater than 10dB, and the spectrum width is greater than 40nm.

3. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The first beam shaping module is composed of two micro lenses placed in parallel, and the second beam shaping module is composed of one micro lens.

4. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The first polarizer is a curved waveguide polarizer, which is used to realize the polarization filtering function and optical waveguide steering of the device.

5. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The second polarizer and the third polarizer are waveguide coupled polarizers, whose two ends are strip waveguide input and output ends, and the middle is a hybrid waveguide coupled polarization section. The hybrid waveguide coupled polarization section is a three-layer structure, the bottom layer of the waveguide with a high refractive index material is lithium niobate, the middle layer with a low refractive index material is silicon dioxide, and the top metal layer is made of metal chromium.

6. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The difference between the optical path of the optical path adjustment waveguide and the optical path of the straight waveguide is greater than the coherence length of the wide-spectrum light source.

7. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The coupler is a multimode interference coupler or a Y-branch coupler.

8. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The modulation electrode adopts a push-pull structure.

9. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The pattern spot converter adopts a conical structure.

10. The fiber optic gyroscope integrated special device according to claim 1, characterized in that: The optical waveguide, two couplers, a first polarizer, and four spot converters are all made of lithium niobate material.

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