Optical integrated device for biaxial optical fiber gyroscope and biaxial optical fiber gyroscope

Abstract

The invention discloses an optical integrated device for a double-axis optical fiber gyroscope and the double-axis optical fiber gyroscope. The optical integrated device comprises a first double-waveguide structure and a second double-waveguide structure, the first double-waveguide structure comprises a first waveguide and a second waveguide; the second double-waveguide structure comprises a third waveguide and a fourth waveguide, the first end of the third waveguide is coupled with the second end of the first waveguide, the second end of the third waveguide is coupled with the first optical fiber ring, the first end of the fourth waveguide is cross-coupled with the second end of the first waveguide, and the second end of the fourth waveguide is coupled with the second optical fiber ring; and the second double-waveguide structure is used for outputting the received TE polarized light from the second end of the third waveguide to the first optical fiber ring, and is used for coupling the received TM polarized light from the first end of the third waveguide into the first end of the fourth waveguide and outputting the TM polarized light from the second end of the fourth waveguide to the second optical fiber ring. By adopting the scheme, the biaxial angular velocity measurement can be realized while the polarization extinction ratio and the light utilization rate are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical devices, and particularly to an optical integrated device for a biaxial fiber optic gyroscope and a biaxial fiber optic gyroscope. Background Art

[0002] A fiber optic gyroscope is an interferometric angular velocity measuring device based on the Sagnac effect and composed of a fiber optic loop. As an all-solid-state instrument without moving parts and wearing parts, it has the characteristics of long life, light weight, small volume, large dynamic range, high precision, and anti-electromagnetic interference. Fiber optic gyroscopes are gradually replacing traditional electromechanical gyroscopes and expensive laser gyroscopes and becoming the mainstream solution for gyro manufacturing, and have important applications in inertial navigation, attitude modulation, weak rotation signal detection, etc. In a fiber optic gyroscope system, the requirement for polarization is very high, and improving the polarization extinction ratio is a key issue for improving the gyro accuracy. Then, how to better process polarized light to improve the polarization extinction ratio while enhancing the utilization rate of light is a problem worthy of focused research at present.

[0003] In the prior art, the main methods for processing polarized light in a fiber optic gyroscope system are as follows: (1) Filter out one polarization state of the input light and only retain the other polarization state (for example, filter out TM polarized light and retain TE polarized light). This processing scheme will cause nearly half of the optical power loss and greatly reduce the utilization rate of light. (2) In a polarization-maintaining fiber loop, two different polarization state polarization light transmission channels are used simultaneously, and the polarization-related errors are cancelled out by using the characteristics that the polarization errors of the two polarization states are equal in amplitude and opposite in phase. This scheme is essentially a single-axis scheme and cannot achieve biaxial angular velocity measurement. Summary of the Invention

[0004] The technical problem solved by the embodiments of the present invention is how to achieve biaxial angular velocity measurement while improving the polarization extinction ratio and the utilization rate of light.

[0005] To solve the above technical problems, an embodiment of the present invention provides an optical integrated device for a dual-axis fiber optic gyroscope, including: a first dual-waveguide structure and a second dual-waveguide structure; the first dual-waveguide structure includes a first waveguide and a second waveguide, and is configured to couple the received input light including TE polarized light and TM polarized light and input it into the second dual-waveguide structure; the second dual-waveguide structure includes a third waveguide and a fourth waveguide, a first end of the third waveguide is coupled to a second end of the first waveguide, a second end of the third waveguide is coupled to a first optical fiber loop, a first end of the fourth waveguide is staggeredly coupled to the second end of the first waveguide, and a second end of the fourth waveguide is coupled to a second optical fiber loop; the second dual-waveguide structure is configured to output the received TE polarized light from the second end of the third waveguide to the first optical fiber loop, and to couple the received TM polarized light from the first end of the third waveguide into the first end of the fourth waveguide and output it from the second end of the fourth waveguide to the second optical fiber loop.

[0006] Optionally, the first ends of the third waveguide and the fourth waveguide satisfy the following conditions:

[0007] Neff1_TM×r1 = Neff2_TM×r2;

[0008] Wherein, Neff1_TM represents the effective refractive index of TM polarized light at the first end of the third waveguide, r1 represents the bending radius of the first end of the third waveguide, Neff2_TM represents the effective refractive index of TM polarized light at the first end of the fourth waveguide, and r2 represents the bending radius of the first end of the fourth waveguide.

[0009] Optionally, the first ends of the third waveguide and the fourth waveguide are mutually parallel curved waveguide structures, and the width of the first end of the third waveguide is less than the width of the first end of the fourth waveguide.

[0010] Optionally, the distance between the first ends of the third waveguide and the fourth waveguide is less than the distance between the second ends of the third waveguide and the fourth waveguide.

[0011] Optionally, the first waveguide gradually widens from the first end to the second end, and the width of the first end of the first waveguide is equal to the width of the first end of the second waveguide.

[0012] Optionally, the shape of the first waveguide is a symmetrically widened cone, and the shape of the second waveguide is a cuboid; the symmetry axis of the first waveguide is parallel to the symmetry axis of the second waveguide.

[0013] Optionally, the optical integration device further includes a first optical combiner / splitter and a second optical combiner / splitter; a first end of the first optical combiner / splitter is coupled to a second end of the third waveguide, a second end of the first optical combiner / splitter is coupled to a first end of the first sub-waveguide, and a third end of the first optical combiner / splitter is coupled to an input end of a first photodetector; a first end of the second optical combiner / splitter is coupled to a second end of the fourth waveguide, a second end of the second optical combiner / splitter is coupled to a first end of a first third sub-waveguide, and a third end of the second optical combiner / splitter is coupled to an input end of a second photodetector.

[0014] Optionally, the second end of the third waveguide further outputs residual TM polarized light; the optical integration device further includes a third dual-waveguide structure, and the third dual-waveguide structure includes a single first sub-waveguide and at least one second sub-waveguide; wherein, a first end of the first sub-waveguide is coupled to the second end of the third waveguide, a second end of the first sub-waveguide is coupled to the first optical fiber loop, and the first sub-waveguide is configured to receive TE polarized light output from the second end of the third waveguide and output the TE polarized light from the second end of the first sub-waveguide; a first end of each second sub-waveguide is parallel to any waveguide segment of the first sub-waveguide, and is configured to couple the residual TM polarized light in the first sub-waveguide into the first end of the second sub-waveguide and output the residual TM polarized light from the second end of the second sub-waveguide.

[0015] Optionally, the shape of the first sub-waveguide is wavy, and a first end of each second sub-waveguide is parallel to a single curved waveguide segment of the first sub-waveguide.

[0016] Optionally, a second end of each second sub-waveguide is away from the first sub-waveguide, and the orientations of the second ends of each second sub-waveguide are the same.

[0017] Optionally, the second end of the fourth waveguide further outputs residual TE polarized light; the optical integration device further includes a fourth dual-waveguide structure, and the fourth dual-waveguide structure includes at least one third sub-waveguide and at least one fourth sub-waveguide, and the third sub-waveguides and the fourth sub-waveguides are arranged alternately; wherein, a first end of the first third sub-waveguide is coupled to the second end of the fourth waveguide, and a second end of the last fourth sub-waveguide is coupled to the second optical fiber loop; starting from the second third sub-waveguide, a first end of each third sub-waveguide is parallel to an intermediate waveguide segment of the fourth sub-waveguide arranged adjacent thereto in front, and a first end of each fourth sub-waveguide is parallel to an intermediate waveguide segment of the third sub-waveguide arranged adjacent thereto in front; wherein, the alternately arranged third sub-waveguides and fourth sub-waveguides are configured to output the residual TE polarized light from a second end of each third sub-waveguide and a second end of each fourth sub-waveguide, and are configured to cause the TM polarized light to cross-couple and output the TM polarized light from the second end of the last fourth sub-waveguide.

[0018] Optionally, the fourth dual waveguide structure satisfies one or more of the following: the lengths of the middle waveguide segments of each third sub-waveguide and their positions in the respective third sub-waveguides are the same; the lengths of the middle waveguide segments of each fourth sub-waveguide and their positions in the respective fourth sub-waveguides are the same; the orientations of the second ends of each third sub-waveguide are the same; the orientations of the second ends of each fourth sub-waveguide are the same.

[0019] Optionally, the optical integration device further includes a third optical combiner / demultiplexer and a fourth optical combiner / demultiplexer; the first end of the third optical combiner / demultiplexer is coupled to the second end of the first sub-waveguide, and the second and third ends of the third optical combiner / demultiplexer are coupled to the first optical fiber loop; the first end of the fourth optical combiner / demultiplexer is coupled to the second end of the last fourth sub-waveguide, and the second and third ends of the fourth optical combiner / demultiplexer are coupled to the second optical fiber loop.

[0020] An embodiment of the present invention further provides a dual-axis fiber optic gyroscope, including the optical integration device described in any one of the above.

[0021] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0022] In the embodiment of the present invention, by combining two dual waveguide structures, efficient coupling of the input light and effective separation of the TE polarization state and the TM polarization state in the input light are respectively achieved. Specifically, a first dual waveguide structure is provided for coupling the received input light containing TE polarized light and TM polarized light and inputting it into the second dual waveguide structure. By setting the first end of the third waveguide of the second dual waveguide structure to be coupled to the second end of the first waveguide, and the first end of the fourth waveguide to be staggeredly coupled to the second end of the first waveguide, the TE polarized light in the input light is output from the second end of the third waveguide in terms of polarization dimension, and the TM polarized light in the input light is coupled into the fourth waveguide from the first end of the third waveguide and output from the second end of the fourth waveguide. Thus, effective separation of the TE polarization state and the TM polarization state in the input light can be achieved.

[0023] Furthermore, compared with the prior art polarization scheme that removes one polarization state and retains the other, or the scheme that utilizes the characteristics of equal amplitudes and opposite signs of the two polarization state errors in a single optical fiber loop to cancel the polarization-related errors and thus improve the gyro stability, this implementation uses two transmission channels and two optical fiber loops to transmit and receive the two separated polarized lights, that is, the TE polarized light output from the second end of the third waveguide enters the first optical fiber loop, and the TM polarized light output from the second end of the fourth waveguide enters the second optical fiber loop. Thus, while improving the extinction ratio and light utilization rate through polarization beam splitting, dual-axis angular velocity measurement can be achieved.

[0024] Furthermore, in the embodiments of the present invention, the first waveguide gradually expands from the first end to the second end. Specifically, by setting the width of the first end of the first waveguide to be smaller, the purpose is to match the mode field of the optical fiber that outputs the input light, reduce the mode field matching loss, and improve the end face coupling efficiency. And by setting a gradually expanding structure, the purpose is to slowly transition the incident light into the single-mode waveguide for transmission (slowly expanding the wavelength band can reduce the loss).

[0025] Furthermore, since the second end of the third waveguide usually outputs residual TM polarized light in addition to TE polarized light; therefore, the optical integrated device may further include a third dual-waveguide structure, and the third dual-waveguide structure may include a single first sub-waveguide and at least one second sub-waveguide; wherein, the first sub-waveguide is configured to receive the TE polarized light output from the second end of the third waveguide and output it from the second end of the first sub-waveguide; wherein, each second sub-waveguide is configured to couple the residual TM polarized light in the first sub-waveguide into the first end of the second sub-waveguide and output it from the second end of the second sub-waveguide. Thereby, effective filtering of the residual TM polarized light can be achieved, the extinction ratio can be improved, and purer TE polarized light can be input into the first optical fiber loop to improve the device performance.

[0026] Further, the shape of the first sub-waveguide can be set to be wavy. Compared with setting the shape of the first sub-waveguide to be zigzag or other angular shapes, this embodiment adopts a wavy structure, which helps to significantly reduce the optical transmission loss. Further, in this embodiment, the first end of each second sub-waveguide can be set to be parallel to a single bent waveguide segment of the first sub-waveguide. In this way, the residual TM polarized light can be maximally coupled into the second sub-waveguide, thereby achieving effective filtering of the residual TM polarized light, improving the extinction ratio, improving the performance of the fiber optic gyroscope, and obtaining a higher-precision measurement result.

[0027] Furthermore, since the second end of the fourth waveguide usually outputs residual TE polarized light in addition to TM polarized light; therefore, the optical integrated device may further include a fourth dual-waveguide structure, and the fourth dual-waveguide structure may include at least one third sub-waveguide and at least one fourth sub-waveguide, and the third sub-waveguide and the fourth sub-waveguide are arranged in an interleaved manner; wherein, the interleaved third sub-waveguide and fourth sub-waveguide are configured to output the residual TE polarized light from the second end of each third sub-waveguide and the second end of each fourth sub-waveguide, and to cause the TM polarized light to cross-couple and output it from the second end of the last fourth sub-waveguide. Thereby, effective filtering of the residual TE polarized light can be achieved, the extinction ratio can be improved, and purer TM polarized light can be input into the second optical fiber loop to improve the device performance.

[0028] Further, by regularly setting the lengths of the intermediate waveguide segments of each third sub-waveguide and their positions in the respective third sub-waveguides to be the same, and / or the lengths of the intermediate waveguide segments of each fourth sub-waveguide and their positions in the respective fourth sub-waveguides to be the same, it helps to improve the coupling efficiency of TM polarized light and reduce the optical power loss during the coupling process. Further, by regularly setting the orientations of the second ends of each third sub-waveguide to be the same, and / or the orientations of the second ends of each fourth sub-waveguide to be the same, it helps to enhance the filtering effect of the remaining TE polarized light, reduce signal crosstalk, and improve the extinction ratio. Brief Description of the Drawings

[0029] Figure 1 is a schematic structural diagram of an optical integrated device for a biaxial fiber optic gyroscope in an embodiment of the present invention;

[0030] Figure 2 is Figure 1 a specific structural schematic diagram of the first dual-waveguide structure of the optical integrated device shown in

[0031] Figure 3 is Figure 1 a coupling structural schematic diagram of the first dual-waveguide structure and the second dual-waveguide structure of the optical integrated device shown in

[0032] Figure 4 is a schematic structural diagram of another optical integrated device for a biaxial fiber optic gyroscope in an embodiment of the present invention. Detailed Embodiments

[0033] As mentioned in the background art, how to better process polarized light and achieve improved polarization extinction ratio while enhancing the utilization rate of light is an issue worthy of focused research at present. In the prior art, a common solution for processing polarized light in a fiber optic gyro system is to remove or filter one polarization state of the input light and only retain the other polarization state.

[0034] For example, a bent waveguide optical loss polarization separation scheme disclosed in the prior art mainly designs a waveguide with a specific refractive index into a bent waveguide structure and utilizes the principle that the losses of TM polarized light and TE polarized light in the bent waveguide structure are different (where TE polarized light can maintain low-loss transmission while TM polarized light is significantly attenuated), thereby achieving the removal of TM polarized light in the input light and retaining TE polarized light. Another polarization beam splitting scheme disclosed in the prior art mainly separates TM polarized light and TE polarized light in the input light into two output paths by a separation device (such as a Y-branch structure, etc.), and then uses a metal to absorb one of the separated polarized lights and retain the other desired polarization state.

[0035] Another existing polarization light processing solution is as follows: in a polarization-maintaining fiber loop, two polarization light transmission channels with different polarization states are used simultaneously. By utilizing the characteristics that the polarization errors of the two polarization states are equal in amplitude and opposite in phase, the polarization-related errors are cancelled out.

[0036] The inventors of the present invention have found through research that the above-mentioned first processing solution will cause a large amount of loss of the input optical power, greatly reducing the utilization rate of light; while the second processing solution, although it transmits two polarization lights to the fiber loop through a dual-channel, is essentially a single-axis solution and cannot achieve dual-axis angular velocity measurement.

[0037] In the embodiments of the present invention, the efficient coupling of the input light and the effective separation of the TE polarization state and the TM polarization state in the input light are respectively realized by combining two dual-waveguide structures. Specifically, the first dual-waveguide structure is used to couple the received input light containing TE polarized light and TM polarized light and input it into the second dual-waveguide structure. By setting the first end of the third waveguide of the second dual-waveguide structure to be coupled with the second end of the first waveguide, and the first end of the fourth waveguide to be stagger-coupled with the second end of the first waveguide, the TE polarized light in the input light is output from the second end of the third waveguide in terms of polarization dimension, and the TM polarized light in the input light is coupled into the fourth waveguide from the first end of the third waveguide and output from the second end of the fourth waveguide. Thus, the effective separation of the TE polarization state and the TM polarization state in the input light can be realized.

[0038] Furthermore, this embodiment uses a dual-channel transmission path and two fiber loops to transmit and receive the two separated polarization lights, that is, the TE polarized light output from the second end of the third waveguide enters the first fiber loop, and the TM polarized light output from the second end of the fourth waveguide enters the second fiber loop. Thus, while improving the extinction ratio and the light utilization rate through polarization beam splitting, dual-axis angular velocity measurement can be achieved.

[0039] To make the above objects, features, and beneficial effects of the present invention more obvious and understandable, the following Figures 1 to 3 will give a detailed description of the specific embodiments of the present invention.

[0040] Among them, Figure 1 is a schematic structural diagram of an optical integrated device 10 for a dual-axis fiber optic gyroscope in the embodiments of the present invention; Figure 2 is Figure 1 a specific schematic structural diagram of the first dual-waveguide structure 11 of the optical integrated device 10 shown in Figure 3 is Figure 1 a schematic coupling structure diagram of the first dual-waveguide structure 11 and the second dual-waveguide structure 12 of the optical integrated device 10 shown in

[0041] Specifically, referring to Figure 1, the optical integrated device 10 includes a first dual waveguide structure 11 and a second dual waveguide structure 12.

[0042] The first dual waveguide structure 11 includes a first waveguide 111 and a second waveguide 112, and is configured to couple the received input light including TE polarized light and TM polarized light and input it into the second dual waveguide structure 12. That is to say, the first dual waveguide structure 11 is mainly used to implement the end-face coupling function.

[0043] The second dual waveguide structure 12 includes a third waveguide 121 and a fourth waveguide 122. A first end a1 of the third waveguide 121 is coupled to a second end c2 of the first waveguide 111, a second end a2 of the third waveguide 121 is coupled to a first optical fiber loop 151, a first end b1 of the fourth waveguide 122 is staggeredly coupled (also referred to as "cross-coupled") to the second end c2 of the first waveguide 111, and a second end b2 of the fourth waveguide 122 is coupled to a second optical fiber loop 152; the second dual waveguide structure 12 is configured to output the received TE polarized light from the second end a2 of the third waveguide 121 to the first optical fiber loop 151 (for example, a polarization-maintaining optical fiber loop), and to couple the received TM polarized light from the first end a1 of the third waveguide 121 into the first end b1 of the fourth waveguide 122 and output it from the second end b2 of the fourth waveguide 122 to the second optical fiber loop 152 (for example, a polarization-maintaining optical fiber loop).

[0044] That is to say, the second dual waveguide structure 12 is mainly used to implement the polarization beam splitting function. Among them, the third waveguide 121 can be referred to as a "direct waveguide", and the fourth waveguide 122 can be referred to as a "cross waveguide".

[0045] In a specific implementation, the first optical fiber loop 151 and the second optical fiber loop 152 are located on two different axes in space. Further, the first optical fiber loop 151 and the second optical fiber loop 152 are respectively located in two planes that are orthogonal (or referred to as perpendicular) to each other. In other words, the contour plane of the first optical fiber loop 151 is perpendicular to the contour plane of the second optical fiber loop 152. In this way, the angular velocity information of two orthogonal axes can be measured simultaneously. For example, in some actual application scenarios, it is necessary to collect the deflection angle information of two axes simultaneously, such as: borehole inclinometer, optoelectronic pod, north finder, etc.

[0046] Further, the first end a1 of the third waveguide 121 and the first end b1 of the fourth waveguide 122 satisfy the following condition (which can be referred to as the "phase matching condition"):

[0047] Neff1_TM×r1 = Neff2_TM×r2;

[0048] Among them, Neff1_TM represents the effective refractive index of TM polarized light at the first end a1 of the third waveguide 121, r1 represents the bending radius (which can also be called the curvature radius) of the first end a1 of the third waveguide 121, Neff2_TM represents the effective refractive index of TM polarized light at the first end b1 of the fourth waveguide 122, and r2 represents the bending radius of the first end b1 of the fourth waveguide 122.

[0049] Among them, the effective refractive index of light in a waveguide refers to the ratio of the propagation constant of light to the vacuum wave number, which can be used to describe the speed and direction of light propagation in the waveguide. The effective refractive index (neff) can be calculated by the propagation constant β and the speed of light c in vacuum: neff = c / β.

[0050] Specifically, when the above conditions are met, TM polarized light can be coupled from the first end a1 of the third waveguide 121 into the first end b1 of the fourth waveguide 122 and output from the second end b2 of the fourth waveguide 122; while when the shape, size, material, etc. of the second double-waveguide structure remain unchanged, TE polarized light under the above conditions will not be coupled into the first end b1 of the fourth waveguide 122, but will continue to be transmitted at the first end a1 of the third waveguide 121 and output from the second end a2 of the third waveguide 121. Thus, the effective separation of TM polarized light and TE polarized light is achieved.

[0051] In a specific embodiment, the first end a1 of the third waveguide 121 and the first end b1 of the fourth waveguide 122 can be set as mutually parallel curved waveguide structures, and the width H1 of the first end a1 of the third waveguide 121 is less than the width H2 of the first end b1 of the fourth waveguide 122.

[0052] As Figure 3 shown, the bending radius of the first end a1 of the third waveguide 121 is r1, and the bending radius of the first end b1 of the fourth waveguide 122 is r2, where r1 > r2. In a specific implementation, in the case of r1 > r2, if the foregoing equation conditions are to be satisfied, the effective refractive index Neff1_TM of TM polarized light at the first end a1 of the third waveguide 121 should be less than the effective refractive index Neff2_TM of the TM polarized light at the first end b1 of the fourth waveguide 121. Therefore, when other waveguide parameters are fixed, H1 < H2 should be set.

[0053] As a non-limiting example, the wavelength λ of the input light can be selected from the range [1.26 nm, 1.36 nm]; r1 can be selected from the range [115 μm, 125 μm], for example, r1 = 120 μm; r2 can be selected from the range [115 μm, 120 μm], for example, r2 = 118 μm; the width H1 of the first end a1 of the third waveguide 121 can be selected from the range [0.8 μm, 1.2 μm], for example, H1 = 1 μm, and the width H2 of the first end b1 of the fourth waveguide 122 can be selected from the range [1.4 μm, 1.8 μm], for example, H2 = 1.6 μm.

[0054] In another specific embodiment, the first end a1 of the third waveguide 121 and the first end b1 of the fourth waveguide 122, in addition to being set as a bent waveguide structure, can also be set as other appropriate structures on the premise of satisfying the above equation conditions. For example, they can be set as straight waveguide structures parallel to each other.

[0055] Further, the distance gap1 between the first end a1 of the third waveguide 121 and the first end b1 of the fourth waveguide 122 is smaller than the distance gap2 between the second end a2 of the third waveguide 121 and the second end b2 of the fourth waveguide 122. For example, the distance gap1 to the distance gap2 can be set to gradually increase.

[0056] In the embodiment of the present invention, by setting gap1 to be smaller than gap2, the TE polarized light and TM polarized light split by the second dual waveguide structure 12 can be further separated, avoiding the TM polarized light that has been coupled into the fourth waveguide 122 from being coupled into the third waveguide 121 again, causing optical signal interference and reducing the splitting effect.

[0057] Further, as Figure 2 shown, the first waveguide 111 of the first dual waveguide structure 11 gradually widens from the first end c1 to the second end c2, and the width of the first end c1 of the first waveguide 111 is equal to the width of the first end c0 of the second waveguide 112.

[0058] Further, the lengths of the first waveguide 111 and the second waveguide 112 are the same.

[0059] Non-limitingly, the wavelength λ of the input light can be selected from the range [1.28 nm, 1.3 nm], the width of the first end c1 of the first waveguide 111 can be selected from the range [0.15 μm, 0.17 μm], for example, 0.16 μm, the second end c2 of the first waveguide 111 can be selected from the range [0.55 μm, 0.65 μm], for example, 0.6 μm, and the width of the first end c0 of the second waveguide 111 can be selected from the range [0.15 μm, 0.17 μm].

[0060] In the embodiment of the present invention, by setting the width of the first end c1 of the first waveguide 111 to be smaller, the purpose is to match the mode field of the optical fiber that outputs the input light, reduce the mode field matching loss, and improve the end face coupling efficiency; and by setting the first waveguide 111 to gradually widen from the first end c1 to the second end c2, the purpose is to slowly transition the incident light into the single-mode waveguide for transmission (slowly widening the wavelength band can reduce the loss).

[0061] Furthermore, the shape of the first waveguide 111 is a symmetrically widened cone, and the shape of the second waveguide 112 is a cuboid; the symmetry axis of the first waveguide 111 is parallel to the symmetry axis of the second waveguide 112. Thus, compared with setting the first waveguide 111 as an asymmetrically widened structure (for example, a right trapezoid structure), or compared with setting both the first waveguide 111 and the second waveguide 112 as long strips with inconsistent widths, the present implementation adopts a dual-waveguide structure of a symmetrically widened conical waveguide combined with a cuboid waveguide for input light coupling, which helps to improve the extinction ratio and reduce the introduction of noise.

[0062] Further, the optical integrated device may further include a first optical multiplexer / demultiplexer 131 and a second optical multiplexer / demultiplexer 132; the first end d1 of the first optical multiplexer / demultiplexer 131 is coupled to the second end a2 of the third waveguide 121, the second end d2 of the first optical multiplexer / demultiplexer 131 is coupled to the first optical fiber loop 151, and the third end d3 of the first optical multiplexer / demultiplexer 131 is coupled to the input end of the first photodetector 141; the first end e1 of the second optical multiplexer / demultiplexer 132 is coupled to the second end b2 of the fourth waveguide 122, the second end e2 of the second optical multiplexer / demultiplexer 132 is coupled to the second optical fiber loop 152, and the third end e3 of the second optical multiplexer / demultiplexer 132 is coupled to the input end of the second photodetector 142.

[0063] Refer to Figure 4 , Figure 4 which is a schematic structural diagram of another optical integrated device 20 for a dual-axis fiber optic gyroscope in the embodiment of the present invention.

[0064] In specific implementation, in addition to outputting TE polarized light, the second end a2 of the third waveguide 121 usually also outputs residual TM polarized light; therefore, in addition to the device structures shown in Figure 1 the optical integrated device 20 may further include a third dual-waveguide structure 16 to further effectively remove the residual TM polarized light.

[0065] Specifically, the third dual-waveguide structure 16 may include a single first sub-waveguide 161 and at least one second sub-waveguide. As Figure 4As shown, by way of non - limitation, the third dual - waveguide structure 16 includes three second sub - waveguides, namely 1621, 1622, and 1623 in the figure.

[0066] Wherein, the first end f1 of the first sub - waveguide 161 is coupled to the second end a2 of the third waveguide 121, the second end f2 of the first sub - waveguide 161 is coupled to the first optical fiber loop 151, and the first sub - waveguide 161 is configured to receive the TE - polarized light output from the second end a2 of the third waveguide 121 and output it from the second end f2 of the first sub - waveguide 161.

[0067] It should be noted that when the optical integrated device 20 includes the first optical splitter / combiner 131, the second end a2 of the third waveguide 121 is coupled to the first end d1 of the first optical splitter / combiner 131, and the first end f1 of the first sub - waveguide 161 is coupled to the second end d2 of the first optical splitter / combiner 131.

[0068] Wherein, the first end of each second sub - waveguide (as Figure 4 shown, the first end of the second sub - waveguide 1621 is g1 and the second end is g2) is parallel to any waveguide segment of the first sub - waveguide 161, and is configured to couple the remaining TM - polarized light in the first sub - waveguide 161 into the first end of this second sub - waveguide and output it from the second end of this second sub - waveguide.

[0069] Furthermore, the shape of the first sub - waveguide 161 can be set to be wavy, and the first end of each second sub - waveguide is parallel to a single curved waveguide segment of the first sub - waveguide 161 (which can also be called a single "raised waveguide segment" of the wavy first sub - waveguide 161).

[0070] Furthermore, the first end of each second sub - waveguide and the waveguide segment of the first sub - waveguide 161 parallel to the first end of this second sub - waveguide (abbreviated as the "first parallel waveguide segment") satisfy the following condition:

[0071] Neff3_TM×r3 = Neff4_TM×r4;

[0072] Wherein, Neff3_TM represents the effective refractive index of the TM - polarized light in the "first parallel waveguide segment", r3 represents the bending radius of the "first parallel waveguide segment", Neff4_TM represents the effective refractive index of the TM - polarized light at the first end of the second sub - waveguide, and r4 represents the bending radius of the first end of the second sub - waveguide.

[0073] Even further, the width of the first end of the second sub - waveguide is greater than the width of the "first parallel waveguide segment" parallel to it.

[0074] Compared with setting the shape of the first sub-waveguide 161 as a broken line or other angular shapes, in this embodiment, the first sub-waveguide 161 adopts a wavy structure, which helps to significantly reduce the optical transmission loss. Further, by setting the first end of each second sub-waveguide to be parallel to a single bent waveguide segment of the first sub-waveguide 161, the remaining TM polarized light can be maximally coupled into the second sub-waveguide, thereby effectively filtering the remaining TM polarized light, improving the extinction ratio, enhancing the performance of the fiber optic gyroscope, and obtaining a higher-precision measurement result.

[0075] Furthermore, the second end of each second sub-waveguide is far from the first sub-waveguide 161, and the orientations of the second ends of each second sub-waveguide are the same. For example, the distance between the second end of each second sub-waveguide and the first sub-waveguide 161 can be set to be greater than the distance between the first end of the second sub-waveguide and the first sub-waveguide 161. In this way, the effective separation of TE polarized light and the remaining TM polarized light can be further achieved, avoiding optical signal interference and improving the extinction ratio. Further, by setting the second ends of the second sub-waveguides to have the same orientation, it helps to reduce the crosstalk of the remaining TM polarized light to the required TE polarized light and obtain a purer TE polarized light.

[0076] It can be understood that the longer the length of the first sub-waveguide 161 and the more the number of second sub-waveguides, the more conducive to the filtering of the remaining TM polarized light. However, correspondingly, it will also increase the process cost and device size. Therefore, in practical applications, the length of the first sub-waveguide 161 and the number of second sub-waveguides should be controlled within an appropriate range in combination with the actual scenario requirements.

[0077] In a specific implementation, the second end b2 of the fourth waveguide 122 usually outputs not only TM polarized light but also the remaining TE polarized light. Therefore, the optical integration device 20 can further include a fourth double-waveguide structure 17 to effectively remove the remaining TE polarized light.

[0078] Specifically, the fourth double-waveguide structure 17 can include at least one third sub-waveguide and at least one fourth sub-waveguide, and the third sub-waveguide and the fourth sub-waveguide are arranged alternately. As Figure 4 shown, without limitation, the fourth double-waveguide structure 17 includes two third sub-waveguides (1711 and 1712 in Figure 4 respectively), and includes two fourth sub-waveguides (1721 and 1722 in Figure 4 respectively).

[0079] Among them, the first end h1 of the first third sub-waveguide 1711 is coupled to the second end b2 of the fourth waveguide 122, and the second end h3 of the last fourth sub-waveguide 1722 is coupled to the second optical fiber loop 152; starting from the second third sub-waveguide 1711, the first end of each third sub-waveguide is parallel to the middle waveguide section of the fourth sub-waveguide arranged adjacent in front, and the first end of each fourth sub-waveguide is parallel to the middle waveguide section of the third sub-waveguide arranged adjacent in front.

[0080] It should be noted that when the optical integrated device 20 includes the second optical splitter / combiner 132, the second end b2 of the fourth waveguide 122 is coupled to the first end e1 of the second optical splitter / combiner 132, and the first end h1 of the first third sub-waveguide 1711 is coupled to the second end e2 of the second optical splitter / combiner 132.

[0081] Among them, the alternately arranged third sub-waveguides and fourth sub-waveguides are used to output the remaining TE polarized light from the second end of each third sub-waveguide and the second end of each fourth sub-waveguide, and to cause the TM polarized light to undergo a cross-coupling phenomenon (or called an interleaved coupling phenomenon) and output from the second end h3 of the last fourth sub-waveguide 1722.

[0082] Furthermore, the first end of each third sub-waveguide and the middle waveguide section of the fourth sub-waveguide arranged adjacent in front and parallel to it (abbreviated as the "second parallel waveguide section") satisfy the following conditions:

[0083] Neff5_TM × r5 = Neff6_TM × r6;

[0084] Among them, Neff5_TM represents the effective refractive index of TM polarized light at the first end of the third sub-waveguide, r5 represents the bending radius of the first end of the third sub-waveguide, Neff6_TM represents the effective refractive index of TM polarized light in the "second parallel waveguide section", and r6 represents the bending radius of the "second parallel waveguide section".

[0085] Furthermore, the width of the first end of the third sub-waveguide is smaller than the width of the "second parallel waveguide section" parallel to it.

[0086] Similarly, the first end of each fourth sub-waveguide and the middle waveguide section of the third sub-waveguide arranged adjacent in front and parallel to it also satisfy the phase matching condition, which will not be elaborated here.

[0087] Further, the fourth dual waveguide structure 17 satisfies one or more of the following: the lengths of the intermediate waveguide segments of each third sub-waveguide and their positions in the respective third sub-waveguides are the same; the lengths of the intermediate waveguide segments of each fourth sub-waveguide and their positions in the respective fourth sub-waveguides are the same; the orientations of the second ends of each third sub-waveguide are the same; the orientations of the second ends of each fourth sub-waveguide are the same.

[0088] In the embodiments of the present invention, by regularly setting the lengths of the intermediate waveguide segments of each third sub-waveguide and their positions in the respective third sub-waveguides to be the same, and / or the lengths of the intermediate waveguide segments of each fourth sub-waveguide and their positions in the respective fourth sub-waveguides to be the same, it helps to improve the coupling efficiency of TM polarized light and reduce the optical power loss during the coupling process.

[0089] Furthermore, by regularly setting the orientations of the second ends of each third sub-waveguide to be the same, and / or the orientations of the second ends of each fourth sub-waveguide to be the same, it helps to enhance the filtering effect of the remaining TE polarized light, reduce signal crosstalk, and improve the extinction ratio.

[0090] It can be understood that the more the number of third sub-waveguides and fourth sub-waveguides, the more conducive to the filtering of the remaining TE polarized light. However, correspondingly, it will also increase the loss of TM polarized light, as well as increase the process cost and device size. Therefore, in practical applications, the number of third sub-waveguides and fourth sub-waveguides should be controlled within an appropriate range in combination with the actual scenario requirements.

[0091] Further, the optical integrated device 20 further includes a third optical combiner / splitter 181 and a fourth optical combiner / splitter 182; the first end j1 of the third optical combiner / splitter 181 is coupled to the second end f2 of the first sub-waveguide 161, and the second end j2 and the third end j3 of the third optical combiner / splitter 181 are coupled to the first optical fiber loop 151; the first end k1 of the fourth optical combiner / splitter 182 is coupled to the second end h3 of the last fourth sub-waveguide 172', and the second end k2 and the third end k3 of the fourth optical combiner / splitter 182 are coupled to the second optical fiber loop 152.

[0092] In specific implementations, the first optical combiner / splitter 131, the second optical combiner / splitter 132, the third optical combiner / splitter 181, and the fourth optical combiner / splitter 182 can all adopt existing conventional optical combiner / splitter devices, which are not limited in the embodiments of the present invention.

[0093] Further, for Figure 1 the shown optical integrated device 10, the device structures other than the first optical fiber loop 151 and the second optical fiber loop 152 can all be integrated on a single chip (chip). For Figure 2For the optical integrated device 10 shown, device structures other than the first optical fiber loop 151 and the second optical fiber loop 152 can also be integrated on a single chip. In this way, a high degree of integration of device structures can be achieved, saving production costs and production time, and also reducing the complexity of subsequent process assembly to a certain extent.

[0094] In a specific implementation, the materials of the waveguides in this application can be selected from one or more of the following: waveguide materials used in the field of integrated optics such as silicon, silicon dioxide, silicon nitride, thin-film lithium niobate, group III-V materials, polymers, etc., for example, silicon nitride.

[0095] The embodiment of the present invention also provides a biaxial fiber optic gyroscope, including Figure 1 the optical integrated device 10 shown or Figure 4 the optical integrated device 20 shown.

[0096] It should be noted that the first optical fiber loop 151 and the second optical fiber loop 152 can be components of the optical integrated device 10 and / or 20, or can be devices independent of the optical integrated device 10 and / or 20.

[0097] In some non-limiting embodiments, the biaxial fiber optic gyroscope can be selected from, but not limited to: north finder of biaxial fiber optic gyro, wellbore inclinometer of biaxial fiber optic gyro, optoelectronic pod, north finder, etc.

[0098] By applying the optical integrated device 10 or 20 provided in the embodiment of the present invention to a biaxial fiber optic gyroscope, a high-precision biaxial measurement (for example, realizing angular velocity measurement in two axial directions) scheme can be achieved.

[0099] It should be understood that the term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article indicates that the associated objects before and after are in an "or" relationship.

[0100] The term "a plurality of" appearing in the embodiments of this application refers to two or more.

[0101] The descriptions such as the first and the second appearing in the embodiments of this application are only for schematic and distinguishing the described objects, without an order, and do not represent a special limitation on the number of devices in the embodiments of this application, and cannot constitute any limitation to the embodiments of this application.

[0102] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. An optical integrated device for a biaxial fiber optic gyroscope, characterized in that, Comprising: A first dual waveguide structure and a second dual waveguide structure; The first dual waveguide structure includes a first waveguide and a second waveguide, and is configured to couple the received input light including TE polarized light and TM polarized light and input it into the second dual waveguide structure; The second dual waveguide structure includes a third waveguide and a fourth waveguide. A first end of the third waveguide is coupled to a second end of the first waveguide, a second end of the third waveguide is coupled to a first optical fiber loop, a first end of the fourth waveguide is staggeredly coupled to the second end of the first waveguide, and a second end of the fourth waveguide is coupled to a second optical fiber loop; The second dual waveguide structure is configured to output the received TE polarized light from the second end of the third waveguide to the first optical fiber loop, and to couple the received TM polarized light from the first end of the third waveguide into the first end of the fourth waveguide and output it from the second end of the fourth waveguide to the second optical fiber loop.

2. The optical integrated device according to claim 1, wherein The first end of the third waveguide and the first end of the fourth waveguide satisfy the following condition: Neff1_TM×r1 = Neff2_TM×r2; Wherein, Neff1_TM represents the effective refractive index of TM polarized light at the first end of the third waveguide, r1 represents the bending radius of the first end of the third waveguide, Neff2_TM represents the effective refractive index of TM polarized light at the first end of the fourth waveguide, and r2 represents the bending radius of the first end of the fourth waveguide.

3. The optical integrated device according to claim 1 or 2, characterized in that, The first end of the third waveguide and the first end of the fourth waveguide are parallel curved waveguide structures, and the width of the first end of the third waveguide is smaller than the width of the first end of the fourth waveguide.

4. The optical integration device according to any one of claims 1, characterized in that The distance between the first end of the third waveguide and the first end of the fourth waveguide is smaller than the distance between the second end of the third waveguide and the second end of the fourth waveguide.

5. The optical integrated device according to claim 1, characterized in that, The first waveguide gradually widens from the first end to the second end, and the width of the first end of the first waveguide is equal to the width of the first end of the second waveguide.

6. The optical integrated device according to claim 5, characterized in that, The shape of the first waveguide is a symmetrically widened cone, and the shape of the second waveguide is a cuboid; The symmetry axis of the first waveguide is parallel to the symmetry axis of the second waveguide.

7. The optical integrated device according to claim 1, characterized in that, The optical integrated device further includes a first optical combiner / splitter and a second optical combiner / splitter; A first end of the first optical combiner / splitter is coupled to the second end of the third waveguide, a second end of the first optical combiner / splitter is coupled to the first optical fiber loop, and a third end of the first optical combiner / splitter is coupled to an input end of a first photodetector; A first end of the second optical combiner / splitter is coupled to the second end of the fourth waveguide, a second end of the second optical combiner / splitter is coupled to the second optical fiber loop, and a third end of the second optical combiner / splitter is coupled to an input end of a second photodetector.

8. The optical integration device according to claim 1 or 7, characterized in that, The second end of the third waveguide also outputs the residual TM polarized light; The optical integrated device further includes a third dual waveguide structure, and the third dual waveguide structure includes a single first sub-waveguide and at least one second sub-waveguide; Wherein, the first end of the first sub-waveguide is coupled to the second end of the third waveguide, the second end of the first sub-waveguide is coupled to the first optical fiber loop, and the first sub-waveguide is configured to receive the TE polarized light output from the second end of the third waveguide and output it from the second end of the first sub-waveguide; The first end of each second sub-waveguide is parallel to any waveguide segment of the first sub-waveguide, and is configured to couple the residual TM polarized light in the first sub-waveguide into the first end of the second sub-waveguide and output it from the second end of the second sub-waveguide.

9. The optical integrated device according to claim 8, wherein The first sub-waveguide is in a wavy shape, and the first end of each second sub-waveguide is parallel to a single bent waveguide segment of the first sub-waveguide.

10. The optical integrated device according to claim 9, wherein, The second end of each second sub-waveguide is away from the first sub-waveguide, and the orientations of the second ends of each second sub-waveguide are the same.

11. The optical integrated device according to claim 8, characterized in that, The second end of the fourth waveguide also outputs the residual TE polarized light; The optical integrated device further includes a fourth dual-waveguide structure, which includes at least one third sub-waveguide and at least one fourth sub-waveguide, and the third sub-waveguides and the fourth sub-waveguides are arranged in an interleaved manner; Wherein, the first end of the first third sub-waveguide is coupled to the second end of the fourth waveguide, and the second end of the last fourth sub-waveguide is coupled to the second optical fiber loop; Starting from the second third sub-waveguide, the first end of each third sub-waveguide is parallel to the middle waveguide segment of the fourth sub-waveguide arranged adjacent thereto in front, and the first end of each fourth sub-waveguide is parallel to the middle waveguide segment of the third sub-waveguide arranged adjacent thereto in front; Wherein, the interleaved third sub-waveguides and fourth sub-waveguides are configured to output the residual TE polarized light from the second end of each third sub-waveguide and the second end of each fourth sub-waveguide, and to cause the TM polarized light to cross-couple and output it from the second end of the last fourth sub-waveguide.

12. The optical integrated device according to claim 11, wherein The fourth dual-waveguide structure satisfies one or more of the following: The lengths of the middle waveguide segments of each third sub-waveguide and their positions in the respective third sub-waveguides are the same; The lengths of the middle waveguide segments of each fourth sub-waveguide and their positions in the respective fourth sub-waveguides are the same; The orientations of the second ends of each third sub-waveguide are the same; The orientations of the second ends of each fourth sub-waveguide are the same.

13. The optical integrated device according to claim 11, wherein, The optical integrated device further includes a third optical splitter / combiner and a fourth optical splitter / combiner; The first end of the third optical splitter / combiner is coupled to the second end of the first sub-waveguide, and the second end and the third end of the third optical splitter / combiner are coupled to the first optical fiber loop; The first end of the fourth optical splitter / combiner is coupled to the second end of the last fourth sub-waveguide, and the second end and the third end of the fourth optical splitter / combiner are coupled to the second optical fiber loop.

14. A dual-axis fiber optic gyroscope, characterized in that, Including the optical integrated device according to any one of claims 1 to 13.

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