A reciprocal structure 3x3 fiber optic gyroscope and method of use

Abstract

The present specification relates to the technical field of fiber-optic gyroscopes, and discloses a reciprocal structure 3x3 fiber-optic gyroscope and a use method thereof, to solve the problems of poor anti-interference, complex calculation, and no consideration of the influence of temperature change on test results, poor environmental adaptability, and limited practicality of a typical non-reciprocal structure 3x3 fiber-optic gyroscope; three photoelectric detectors, a 2x2 coupler, a 3x3 coupler, a temperature sensor, and a signal processing module; the 2x2 coupler, the 3x3 coupler, the first photoelectric detector D1, the second photoelectric detector D2, and the third photoelectric detector D3 constitute a reciprocal structure 3x3 fiber-optic gyroscope optical path. The reciprocal structure 3x3 fiber-optic gyroscope extracts a reciprocal end output signal, uses the reciprocal end output signal as a reference quantity for differential demodulation, eliminates the influence of optical path loss variation and light source fluctuation on the gyroscope output signal, and greatly improves the anti-interference of the gyroscope system.

Description

Technical Field

[0001] This document relates to the field of fiber optic gyroscope technology, and in particular to a reciprocal 3×3 fiber optic gyroscope and its usage method. Background Technology

[0002] The 3×3 fiber optic gyroscope was first proposed in 1980. This scheme uses the coupling phase shift of the 3×3 coupler itself to introduce phase bias, which can form a simple all-fiber open-loop fiber optic gyroscope. It eliminates the use of phase modulation devices in typical structures, and achieves a significant reduction in gyroscope cost. It has advantages such as low cost and easy miniaturization, and is one of the main development directions of low-cost fiber optic gyroscopes, with important practical application value.

[0003] Current 3×3 fiber optic gyroscope designs are non-reciprocal structures. They demodulate angular velocity using the output signals from the backward non-reciprocal end and the forward reference end. Since the reference end signal does not contain common-mode interference information found in the non-reciprocal end signal, such as the fiber loop loss factor, it is impossible to completely eliminate the influence of common-mode interference through differential operations, resulting in poor anti-interference capabilities. Typical solutions achieve angular velocity demodulation through trigonometric function operations, which involves a large amount of computation during calibration and solution and is not suitable for digital signal processing. Therefore, typical non-reciprocal 3×3 fiber optic gyroscopes suffer from poor anti-interference capabilities, complex calculations, and do not consider the impact of temperature changes on test results, resulting in poor environmental adaptability. This is one of the main reasons hindering the practical application of 3×3 fiber optic gyroscopes.

[0004] To address the aforementioned issues, this invention proposes a 3×3 fiber optic gyroscope with a reciprocal structure. Based on the output signals from the reciprocal and non-reciprocal ends, a temperature variable is introduced to establish a polynomial demodulation model over the entire temperature range. This model meets the requirements of digital signal processing, effectively suppresses common-mode interference in fiber optic loops and the effects of temperature changes, improves the gyroscope's environmental adaptability, and constitutes a novel, low-cost, high-performance fiber optic gyroscope. Summary of the Invention

[0005] This specification provides a reciprocal 3×3 fiber optic gyroscope to address the problems of typical non-reciprocal 3×3 fiber optic gyroscopes, such as poor anti-interference capabilities, complex calculations, failure to consider the impact of temperature changes on test results, poor environmental adaptability, and limited practicality. The reciprocal 3×3 fiber optic gyroscope includes:

[0006] Broadband light source 1, first photodetector D1 2, second photodetector D2 9, third photodetector D3 8, 2×2 coupler 3, 3×3 coupler 4, depolarizer 5, single-mode fiber ring 6, temperature sensor 7, and signal processing module 10;

[0007] The broadband light source 1 is connected to port d of the 2×2 coupler 3;

[0008] Port e of 2×2 coupler 3 is connected to port a1 of 3×3 coupler 4, port f of 2×2 coupler 3 is connected to the third photodetector D3 8, and port g of 2×2 coupler 3 is left unused.

[0009] Ports b1 and c1 of the 3×3 coupler 4 are connected to the first photodetector D1 2 and the second photodetector D29, respectively. Port b2 of the 3×3 coupler 4 is connected to the first end of the single-mode fiber ring 6 through the depolarizer 5. Port c2 of the 3×3 coupler 4 is connected to the second end of the single-mode fiber ring 6. Port a2 of the 3×3 coupler 4 is left unused.

[0010] Temperature sensor 7 is located in the same temperature field as 3×3 coupler 4 and single-mode fiber ring 6;

[0011] The first photodetector D12, the second photodetector D29, the third photodetector D38, and the temperature sensor 7 are respectively connected to different input ports of the signal processing module 10; the output port of the signal processing module 10 is connected to the broadband light source 1.

[0012] In some preferred embodiments, the 2×2 coupler 3, the 3×3 coupler 4, the first photodetector D12, the second photodetector D2 9, and the third photodetector D3 8 constitute a reciprocal 3×3 fiber optic gyroscope optical path.

[0013] A second aspect of the present invention provides a method for using a reciprocal 3×3 fiber optic gyroscope, implemented based on the aforementioned reciprocal 3×3 fiber optic gyroscope, the method comprising:

[0014] Step S100: Obtain the measured values ​​of the first photodetector D12, the second photodetector D29, and the third photodetector D38 in the reciprocal 3×3 fiber optic gyroscope;

[0015] Step S200: Based on the measurement values ​​of the first photodetector D1 2, the second photodetector D2 9 and the third photodetector D3 8, input the polynomial signal solution model and calculate the angular velocity;

[0016] The polynomial signal calculation model is a calculation model obtained by repeatedly measuring the measured values ​​of the first photodetector D12, the second photodetector D29, and the third photodetector D38 at different temperatures and preset angular velocities, and then fitting the data.

[0017] In some preferred embodiments, the method specifically includes:

[0018] Control the broadband light source 1 to output the first light source signal;

[0019] The first light source signal is decomposed into a first beam and a second beam via the 2×2 coupler 3 and the 3×3 coupler 4;

[0020] The first beam and the second beam are simultaneously input into the first end of the single-mode fiber ring 6 / the second end of the single-mode fiber ring 6 in clockwise / counterclockwise directions, respectively. After circling once, the third beam and the fourth beam are obtained from the second end of the single-mode fiber ring / the first end of the single-mode fiber ring, respectively.

[0021] The third and fourth beams return to the 3×3 coupler 4 and interfere with each other. The first interference beam P1 and the second interference beam P2 are output at ports b1 and c1 of the 3×3 coupler 4, respectively. The interference signal output at the first port a1 of the 3×3 coupler 4 passes through port e of the 2×2 coupler 3 and outputs the third interference beam P3.

[0022] The first interference light P1, the second interference light P2, and the third interference light P3 are transmitted to the signal processing module 10 via the first photodetector D12, the second photodetector D29, and the third photodetector D38, respectively.

[0023] Temperature sensor 7 collects the temperature T of 3×3 coupler 4 and single-mode fiber ring 6 in real time and transmits it to signal processing module 10;

[0024] The signal processing module 10 establishes a polynomial signal solution model based on the first interference light P1, the second interference light P2, the third interference light P3 and the temperature T to calculate the angular velocity.

[0025] In some preferred embodiments, the polynomial signal solution model is specifically as follows:

[0026]

[0027] Where Ω′ represents the calculated value of the angular velocity sensed by the gyroscope, c1, c2, c3, c4, c5 and c6 are coefficients obtained through calibration statistics, where c2, c4 and c6 are temperature-independent term coefficients, c1, c3 and c5 are temperature-dependent term compensation coefficients, T0 represents the first reference temperature value, and T represents the temperature measurement value.

[0028] In some preferred embodiments, the method further includes a step of calibrating the polynomial signal solution model, specifically:

[0029] At a set first reference temperature T0, the first interference light P1, the second interference light P2, and the third interference light P3 are measured by recording multiple known angular velocity inputs within the measurement range using the reciprocal structure 3×3 fiber optic gyroscope.

[0030] Set T = T0, input the first interference light P1, the second interference light P2, and the third interference light P3 into the polynomial signal solution model, use the known angular velocity as Ω, and obtain the calibration values ​​of the temperature-independent term coefficients c2, c4, and c6 by least squares fitting;

[0031] At a set second reference temperature T1, the first interference light P1', the second interference light P2', and the third interference light P3' at T1 are measured by the reciprocal 3×3 fiber optic gyroscope when multiple known angular velocity inputs are recorded within the measurement range.

[0032] Set T = T1, input the first interference light P1', the second interference light P2', and the third interference light P3' under T1 to the polynomial signal solution model, use the known angular velocity as Ω, and obtain the calibration values ​​of the temperature-related term compensation coefficients c1, c3, and c5 by least squares fitting;

[0033] The measured temperature-independent term coefficient, temperature-dependent term compensation coefficient, and first reference temperature T0 are substituted into the polynomial signal solution model to complete the model calibration.

[0034] In some preferred embodiments, the theoretical output values ​​of the first interference beam P1, the second interference beam P2, and the third interference beam P3 are:

[0035]

[0036]

[0037] P3=[a3+b3cos(KΩ)]·d s ·I0

[0038] Where a1, a2, and a3 represent the DC amplitudes of the first, second, and third interference lights, respectively, and b1, b2, and b3 represent the AC amplitudes of the first, second, and third interference lights, respectively. and The additional coupling phase shift introduced by the 3×3 coupler 4 is represented by K, which represents the gyroscope sensitivity, Ω represents the known angular velocity of the input gyroscope, and d represents the gyroscope's angular velocity. s I0 represents the attenuation coefficient of the fiber optic loop, and I0 represents the input power of the light source.

[0039] In some preferred embodiments, after one revolution, the third beam and the fourth beam are obtained from the second end / first end of the single-mode fiber ring 6, respectively, specifically as follows:

[0040] The first beam and the second beam are simultaneously input to the first end of the single-mode fiber ring 6 and the second end of the single-mode fiber ring 6 in clockwise and counterclockwise directions, respectively.

[0041] The Sagnac phase shift between the two beams is caused by the rotation of the fiber optic ring plane. The third and fourth beams are obtained.

[0042] In some preferred embodiments, the third and fourth beams return to the 3×3 coupler 4 and interfere, specifically including:

[0043] The third and fourth beams interfere within the 3×3 coupler 4 and are simultaneously affected by an inherent phase shift. The phase difference between the outputs from ports b1 and c1 and the output from port a1 is [missing information]. and Interference light;

[0044] The three interferometric optical signals contain the same common-mode interference factor. Since the third interferometric light P3, output from port a1 (the reciprocal terminal), has the lowest sensitivity at zero and is not affected by coupling phase shift interference, the third interferometric light P3 is used as the reference. By using differential operations to eliminate the influence of the common-mode factor, the transition term is obtained as follows:

[0045]

[0046]

[0047] After differential operation, the transition term is related to the light source input power I0 and the attenuation coefficient d of the fiber loop. s Regardless, the solution of the polynomial signal model is completed through the aforementioned transition term.

[0048] In some preferred embodiments, the and Controlled by a coupled phase shift-temperature model, which is:

[0049]

[0050]

[0051] This indicates the coupling phase shift at a measured temperature of T. The value, This indicates the coupling phase shift at a measured temperature of T. The value, Indicates the coupled phase shift at the first reference temperature T0 The value, Indicates the coupled phase shift at the first reference temperature T0 The value of .

[0052] The above-described at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0053] (1) The reciprocal structure 3×3 fiber optic gyroscope proposed in this invention extracts the output signal of the reciprocal end and uses it as a reference quantity for differential demodulation, which eliminates the influence of optical path loss changes and light source fluctuations on the gyroscope output signal and greatly improves the anti-interference capability of the gyroscope system.

[0054] (2) The reciprocal structure 3×3 fiber optic gyroscope proposed in this invention only involves four arithmetic operations, which has low computational complexity and fast computation speed, improves demodulation efficiency, and reduces hardware and software costs.

[0055] (3) The reciprocal structure 3×3 fiber optic gyroscope proposed in this invention establishes a polynomial signal solution model based on the temperature variation law of coupling phase shift, realizes accurate demodulation of the gyroscope in the whole temperature range, and has low computational complexity and fast speed, which is suitable for digital signal processing, further reduces the cost of the gyroscope, constitutes a new type of low-cost and high-performance fiber optic gyroscope, and improves the practicality of the 3×3 fiber optic gyroscope scheme.

[0056] (4) The reciprocal 3×3 fiber optic gyroscope proposed in this invention only requires two sets of calculations at two temperatures to complete the calibration of the demodulation formula over the entire temperature range, which improves the preparation efficiency and broadens the application scenarios. Attached Figure Description

[0057] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0058] Figure 1 This is a schematic diagram illustrating the structural principle of a reciprocal 3×3 fiber optic gyroscope provided in one embodiment of this specification.

[0059] Figure 2 This is a flowchart illustrating the usage of the reciprocal 3×3 fiber optic gyroscope provided in the second embodiment of this specification.

[0060] Figure 3 This is a schematic diagram illustrating the principle of a fiber optic gyroscope in the current technology.

[0061] Figure 4 This is a graph showing the coupling phase shift-temperature variation law of two embodiments in this specification;

[0062] Figure 5 This is a graph showing the theoretical error curve of the polynomial signal solving model in the second embodiment of this specification.

[0063] Figure 6This is a schematic diagram of the calibration process for the polynomial signal solving model in the second embodiment of this specification;

[0064] Figure 7 This is a graph showing the actual output signal curve of the reciprocal 3×3 fiber optic gyroscope in the second embodiment of this specification;

[0065] Figure 8 This is a flowchart of the test of the reciprocal 3×3 fiber optic gyroscope polynomial demodulation model in the second embodiment of this specification;

[0066] Figure 9 The figure shows the test results of the reciprocal 3×3 fiber optic gyroscope polynomial demodulation model in the second embodiment of this specification.

[0067] Figure 10 This is a graph showing the actual demodulation error curve of the reciprocal 3×3 fiber optic gyroscope polynomial demodulation model in the second embodiment of this specification. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0069] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0070] Figure 1 This is a schematic diagram illustrating the structural principle of a reciprocal 3×3 fiber optic gyroscope according to one embodiment of this specification. (See attached diagram.) Figure 1 The gyroscope may specifically include the following structure:

[0071] Broadband light source 1, first photodetector D1 2, second photodetector D2 9, third photodetector D3 8, 2×2 coupler 3, 3×3 coupler 4, depolarizer 5, single-mode fiber ring 6, temperature sensor 7, and signal processing module 10.

[0072] The broadband light source 1 is connected to port d of the 2×2 coupler 3. The broadband light source can be any wavelength SLD light source, ASE light source, or other broadband light source, used to output broadband light to the depolarized single-mode fiber ring;

[0073] Port e of 2×2 coupler 3 is connected to port a1 of 3×3 coupler 4, port f of 2×2 coupler 3 is connected to the third photodetector D3 8, and port g of 2×2 coupler 3 is left unused.

[0074] Ports b1 and c1 of the 3×3 coupler 4 are connected to the first photodetector D12 and the second photodetector D29, respectively. Port b2 of the 3×3 coupler 4 is connected to the first end of the single-mode fiber ring 6 through the depolarizer 5, and port c2 of the 3×3 coupler 4 is connected to the second end of the single-mode fiber ring 6. Port a2 of the 3×3 coupler 4 is left unused. The depolarizer 5 can be connected to either the first or second end of the single-mode fiber ring 6 as needed.

[0075] A 3x3 coupler consists of three optical fibers coupled together, with a corresponding relationship between its input and output ports. Typically, it is used as shown in the attached diagram. Figure 1 The output ports (b2, c2) corresponding to the two non-reciprocal ports (b1, c1) other than the light source input port a1 (called the reciprocal port in the gyroscope) are used to connect the fiber optic ring.

[0076] In this embodiment, the 2×2 coupler 3, the 3×3 coupler 4, the first photodetector D1 2, the second photodetector D2 9, and the third photodetector D3 8 constitute a reciprocal 3×3 fiber optic gyroscope optical path. Port a1, where the 3×3 coupler 4 and the 2×2 coupler 3 are interconnected, is a common port for both light source input and signal output. The clockwise and counterclockwise beam transmission paths from this port are completely identical, exhibiting reciprocity. The output interference signal P3 is unaffected by the added phase shift of the coupler and is therefore called a reciprocal port. Correspondingly, ports b1 and c1 of the 3×3 coupler 4 are called non-reciprocal ports. The combined output signals from the three ports demodulate the gyroscope speed, thus forming a reciprocal 3×3 fiber optic gyroscope optical path.

[0077] Temperature sensor 7 is positioned within the same temperature field of the 3×3 coupler 4 and the single-mode fiber optic ring 6. Standard platinum resistance thermometers and other similar instruments are used to measure the temperature of the 3×3 coupler 4 and the single-mode fiber optic ring 6.

[0078] The first photodetector D12, the second photodetector D29, the third photodetector D38, and the temperature sensor 7 are respectively connected to different input ports of the signal processing module 10; the output port of the signal processing module 10 is connected to the broadband light source 1. The signal processing module 10 is used to drive and control the broadband light source 1, collect the interference light received by the photodetectors and the temperature returned by the temperature sensor, and calculate the angular velocity. The signal processing module can be a computer, a microcontroller, or other microprocessor module.

[0079] The reciprocal fiber optic gyroscope proposed in this embodiment is compared to... Figure 3The existing non-reciprocal 3×3 fiber optic gyroscope shown adds a 2×2 coupler to extract the reciprocal end output signal and adds a temperature sensor to detect and compensate for temperature changes, achieving high adaptability and high performance angular velocity detection while ensuring low cost.

[0080] A second embodiment of the present invention provides a method for using a reciprocal 3×3 fiber optic gyroscope. The method is based on the aforementioned reciprocal 3×3 fiber optic gyroscope and includes:

[0081] Step S100: Obtain the measured values ​​of the first photodetector D12, the second photodetector D29, and the third photodetector D38 in the reciprocal 3×3 fiber optic gyroscope; specifically:

[0082] The broadband light source 1 is controlled to output the first light source signal; in this embodiment, a 1310nm SLD light source is selected.

[0083] The first light source signal is decomposed into a first beam and a second beam via the 2×2 coupler 3 and the 3×3 coupler 4;

[0084] The first beam and the second beam are simultaneously input into the first end / second end of the single-mode fiber ring 6 in clockwise / counterclockwise directions, respectively. After circling once, the third beam and the fourth beam are obtained from the second end / first end of the single-mode fiber ring 6, respectively.

[0085] In this embodiment, the third beam and the fourth beam are obtained from the second end / first end of the single-mode fiber ring 6 after one revolution, respectively, as follows:

[0086] The first beam and the second beam are simultaneously input to the first end of the single-mode fiber ring 6 and the second end of the single-mode fiber ring 6 in clockwise and counterclockwise directions, respectively.

[0087] The Sagnac phase shift between the two beams is caused by the rotation of the fiber optic ring plane. The third and fourth beams are obtained.

[0088] The third and fourth beams return to the 3×3 coupler 4 and interfere with each other. The first interference beam P1 and the second interference beam P2 are output at ports b1 and c1 of the 3×3 coupler 4, respectively. The interference signal output at port a1 of the 3×3 coupler 4 passes through port e of the 2×2 coupler 3 and outputs the third interference beam P3.

[0089] The first interference light P1, the second interference light P2, and the third interference light P3 are transmitted to the signal processing module 10 via the first photodetector D12, the second photodetector D29, and the third photodetector D38, respectively. In this embodiment, the photodetectors used are all PIN-FET photodetectors for photoelectric conversion.

[0090] Temperature sensor 7 collects the temperature T of 3×3 coupler 4 and single-mode fiber ring 6 in real time and transmits it to signal processing module 10.

[0091] Step S200: Based on the measurement values ​​of the first photodetector D1 2, the second photodetector D2 9 and the third photodetector D3 8, input the polynomial signal solution model and calculate the angular velocity;

[0092] The polynomial signal calculation model is a calculation model obtained by repeatedly measuring the measured values ​​of the first photodetector D12, the second photodetector D29, and the third photodetector D38 at different temperatures and preset angular velocities, and then fitting the data.

[0093] Specifically:

[0094] The signal processing module 10 establishes a polynomial signal solution model based on the first interference light P1, the second interference light P2, the third interference light P3 and the temperature T to calculate the angular velocity.

[0095] In this embodiment, the polynomial signal solution model is specifically as follows:

[0096]

[0097] Where Ω′ represents the calculated value of the angular velocity sensed by the gyroscope, c1, c2, c3, c4, c5 and c6 are coefficients obtained through calibration statistics, where c2, c4 and c6 are temperature-independent term coefficients, c1, c3 and c5 are temperature-dependent term compensation coefficients, T0 represents the first reference temperature, and T represents the temperature measurement value.

[0098] In this embodiment, the method further includes a step of calibrating the polynomial signal solution model, such as... Figure 6 As shown, specifically:

[0099] At a set first reference temperature T0, the first interference light P1, the second interference light P2, and the third interference light P3 are measured when multiple known angular velocities are input within the measurement range using the reciprocal 3×3 fiber optic gyroscope. In this embodiment, a standard platinum resistance thermometer is used to detect the temperature of the environment in which the fiber optic gyroscope structure is located. The ambient temperature of the entire reciprocal 3×3 fiber optic gyroscope is controlled at T0 = 25℃ using a temperature chamber and a platinum resistance temperature sensor. Multiple known angular velocities within the ±100° / s measurement range are recorded, and the corresponding outputs of each interference light are as follows: Figure 7As shown;

[0100] In this embodiment, the theoretical output values ​​of the first interference beam P1, the second interference beam P2, and the third interference beam P3 are:

[0101]

[0102]

[0103] P3=[a3+b3cos(KΩ)]·d s ·I0

[0104] Where a1, a2, and a3 represent the DC amplitudes of the first, second, and third interference lights, respectively, and b1, b2, and b3 represent the AC amplitudes of the first, second, and third interference lights, respectively. and The additional coupling phase shift introduced by the 3×3 coupler 4 is represented by K, where K represents the gyroscope sensitivity, Ω represents the known angular velocity of the input gyroscope, and d s I0 represents the attenuation coefficient of the fiber optic loop, and I0 represents the input power of the light source.

[0105] In this embodiment, the third beam and the fourth beam return to the 3×3 coupler 4 and interfere, specifically including:

[0106] The third and fourth beams interfere within the 3×3 coupler 4 and are simultaneously affected by an inherent phase shift. The phase difference between the outputs from ports b1 and c1 and the output from port a1 is [missing information]. and Interference light;

[0107] The three interferometric optical signals contain the same common-mode interference factor. Since the third interferometric light P3, output from port a1 (the reciprocal terminal), has the lowest sensitivity at zero and is not affected by coupling phase shift interference, the third interferometric light P3 is used as the reference. By using differential operations to eliminate the influence of the common-mode factor, the transition term is obtained as follows:

[0108]

[0109]

[0110] After differential operation, the transition term is related to the light source input power I0 and the attenuation coefficient d of the fiber loop. s The solution to the polynomial signal model is completed through the aforementioned transition term. Demodulating the angular velocity using the two variables described above avoids the influence of light source fluctuations and optical path loss fluctuations on the gyroscope output signal, thereby improving the anti-interference capability of the gyroscope system.

[0111] Set T = T0, input the first interference light P1, the second interference light P2, and the third interference light P3 into the polynomial signal solution model, use the known angular velocity as Ω, and obtain the calibration values ​​of the temperature-independent term coefficients c2, c4, and c6 by least squares fitting;

[0112] In this embodiment, the and Controlled by a coupled phase shift-temperature model, which is:

[0113]

[0114]

[0115] This indicates the coupling phase shift at a measured temperature of T. The value, This indicates the coupling phase shift at a measured temperature of T. The value, Indicates the coupled phase shift at the first reference temperature T0 The value, Indicates the coupled phase shift at the first reference temperature T0 The value of . The law curve of coupling phase shift-temperature change is as follows: Figure 4 As shown;

[0116] Within the small signal range After simplification and calculation, a polynomial signal solution model for the input angular velocity Ω with respect to the first interference beam P1, the second interference beam P2, the third interference beam P3, and T is obtained, resulting in:

[0117]

[0118]

[0119]

[0120] It can be seen that the parameters of the coupler at room temperature and the temperature variation factor k of the coupling phase shift are... T Once determined, all coefficients c1 to c6 in formula (6) are constants. Therefore, the values ​​of all coefficients in the polynomial model can be determined by calibration, and the angular velocity demodulation formula can be obtained. The output signal of the gyroscope at any temperature can be demodulated to complete the angular velocity test.

[0121] At the set second reference temperature T1, the first interference light P1', the second interference light P2', and the third interference light P3' at T1 are measured when multiple known angular velocities are input within the measurement range using the reciprocal structure 3×3 fiber optic gyroscope. The temperature is changed, for example, the temperature of the reciprocal structure 3×3 fiber optic gyroscope is controlled at 30℃, and the measurement is repeated. The multiple sets of interference light input signals are then calibrated by the processor 8.

[0122] Set T = T1, input the first interference beam P1', the second interference beam P2', and the third interference beam P3' under T1 to the polynomial signal solution model. Using the known angular velocity as Ω, obtain the calibration values ​​of the temperature-dependent term compensation coefficients c1, c3, and c5 through least squares fitting. In this embodiment, the measured temperature-independent term coefficients c2 = 1.73, c4 = -334.06, and c6 = 362.23, and the temperature-dependent term coefficients c1 = 0.73, c3 = -0.31, and c5 = -0.38, resulting in the calibrated demodulation formula:

[0123]

[0124] The theoretical error curves of the demodulation model at different temperatures are attached. Figure 5 As shown, at φ S Within the range of (-0.5, 0.5) rad, the maximum theoretical error is 171 ppm, which is negligible compared to the 2000 ppm nonlinear error required in practical applications of 3×3 fiber optic gyroscopes. Therefore, the proposed polynomial demodulation scheme can greatly simplify the calculation while ensuring accuracy, and realize low-cost, high-performance angular velocity detection across the entire temperature range.

[0125] The demodulation results of a reciprocal 3×3 fiber optic gyroscope under random temperature were verified using the calibrated demodulation formula. Figure 8 As shown, the demodulation results at various speeds are as follows: Figure 9 As shown, the actual demodulation error curve is as follows: Figure 10 As shown, the maximum demodulation error in the experiment was 1206 ppm, which meets the requirement of nonlinear error less than 2000 ppm, verifying the effectiveness of the reciprocal 3×3 fiber optic gyroscope structure and its temperature-compensated polynomial demodulation scheme.

[0126] The measured temperature-independent term coefficient, temperature-dependent term compensation coefficient, and first reference temperature T0 are substituted into the polynomial signal solution model to complete the model calibration.

[0127] Compared to the 2×2 reciprocal structure used in traditional fiber optic gyroscopes, this embodiment does not require an optoelectronic modulator to demodulate the final rotation speed signal, reducing manufacturing costs and eliminating the precision threshold of optoelectronic modulators.

[0128] Existing 3×3 fiber optic gyroscopes all adopt a "non-reciprocal structure" and pay little attention to the reciprocal end signal. This embodiment uniquely applies a reciprocal structure to the 3×3 fiber optic gyroscope, utilizing the reciprocal end signal to improve the anti-interference capability of the 3×3 gyroscope system. Furthermore, it achieves solution over the entire temperature range through a polynomial signal solution model, reducing computational complexity, lowering gyroscope costs, and improving temperature adaptability.

[0129] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A reciprocal 3×3 fiber optic gyroscope, characterized in that, The gyroscope includes: Broadband light source (1), first photodetector D1 (2), second photodetector D2 (9), third photodetector D3 (8), 2 2 Coupler (3), 3 3 Coupler (4), depolarizer (5), single-mode fiber ring (6), temperature sensor (7) and signal processing module (10); The broadband light source (1) and 2 2. The port d of the coupler (3) is connected; 2 2. The port e of the coupler (3) is connected to 3.

3. Ports a1, 2 of coupler (4) 2. Port f of coupler (3) is connected to the third photodetector D3 (8), 2 2. Port g of coupler (3) is left unused; 3 Ports b1 and c1 of coupler (4) are connected to the first photodetector D1 (2) and the second photodetector D2 (9) respectively. Port b2 of coupler (4) is connected to the first end of single-mode fiber ring (6) via depolarizer (5). Port c2 of coupler (4) is connected to the second end of single-mode fiber ring (6), 3 Port a2 of coupler (4) is unused; Temperature sensor (7), set at 3 3. Coupler (4) and single-mode fiber ring (6) are in the same temperature field; The first photodetector D1 (2), the second photodetector D2 (9), the third photodetector D3 (8) and the temperature sensor (7) are respectively connected to different input ports of the signal processing module (10); the output port of the signal processing module (10) is connected to the broadband light source (1).

2. The reciprocal 3×3 fiber optic gyroscope according to claim 1, characterized in that, The 2 2 Coupler (3), 3 The three couplers (4), the first photodetector D1 (2), the second photodetector D2 (9) and the third photodetector D3 (8) constitute a reciprocal 3×3 fiber optic gyroscope optical path.

3. A method for using a reciprocal 3×3 fiber optic gyroscope, characterized in that, The method is implemented based on a reciprocal 3×3 fiber optic gyroscope as described in any one of claims 1 or 2, and the method includes: Step S100: Obtain the measured values ​​of the first photodetector D1 (2), the second photodetector D2 (9), and the third photodetector D3 (8) in the reciprocal 3×3 fiber optic gyroscope; Step S200: Based on the measured values ​​of the first photodetector D1 (2), the second photodetector D2 (9) and the third photodetector D3 (8), input the polynomial signal solution model and calculate the angular velocity; The polynomial signal calculation model is a calculation model obtained by repeatedly measuring the measured values ​​of the first photodetector D1 (2), the second photodetector D2 (9), and the third photodetector D3 (8) at different temperatures and preset angular velocities, and then fitting the results.

4. The method of using the reciprocal 3×3 fiber optic gyroscope according to claim 3, characterized in that, The method is specifically as follows: Control the broadband light source (1) to output the first light source signal; The first light source signal is transmitted via the 2 2 Coupler (3), 3 3. Coupler (4) is decomposed into a first beam and a second beam; The first beam and the second beam are simultaneously input into the first end / second end of the single-mode fiber ring (6) in clockwise / counterclockwise directions, respectively. After circling around once, the third beam and the fourth beam are obtained from the second end / first end of the single-mode fiber ring (6) respectively. The third and fourth beams return to the 3 The 3×3 coupler (4) generates interference, and the first interference light P1 and the second interference light P2 are output from ports b1 and c1 of the 3×3 coupler (4) respectively. The interference signal is output from port a1 of the 3×3 coupler (4) and passes through 2 The third interference beam P3 is output from port e of coupler (3); The first interference light P1, the second interference light P2 and the third interference light P3 are transmitted to the signal processing module (10) via the first photodetector D1 (2), the second photodetector D2 (9) and the third photodetector D3 (8), respectively. Temperature sensor (7) collects data in real time. The temperature T of the coupler (4) and the single-mode fiber ring (6) is transmitted to the signal processing module (10). The signal processing module (10) establishes a polynomial signal solution model based on the first interference light P1, the second interference light P2, the third interference light P3 and the temperature T to calculate the angular velocity.

5. The method of using the reciprocal 3×3 fiber optic gyroscope according to claim 3, characterized in that, The polynomial signal solution model is specifically as follows: ； in, This represents the calculated value of the angular velocity that the gyroscope is sensitive to. , , , , and Let be the coefficients obtained through calibration statistics, where , and Here is the coefficient for the temperature-independent term. , and This is the compensation coefficient for temperature-related terms. Indicates the first reference temperature value. This indicates the measured temperature value.

6. The method of using the reciprocal 3×3 fiber optic gyroscope according to claim 5, characterized in that, The method also includes a step of calibrating the polynomial signal solution model, specifically: At the set first reference temperature value Below, the first interference light P1, the second interference light P2, and the third interference light P3 are measured when multiple known angular velocities are input within the measurement range using the reciprocal 3×3 fiber optic gyroscope. set up The first interference beam P1, the second interference beam P2, and the third interference beam P3 are input into the polynomial signal solution model, and the known angular velocity is used as... The coefficients of the temperature-independent term were obtained by fitting using the least squares method. , and The calibration value; In setting Second reference temperature Below, the measured values ​​are obtained by recording multiple known angular velocities within the measurement range using the reciprocal structure 3×3 fiber optic gyroscope. The first interference light , The second interference light , The third interference light ; set up Input to the polynomial signal solution model The first interference light , The second interference light , The third interference light Using the known angular velocity as The compensation coefficients for temperature-related terms were obtained by fitting using the least squares method. , and The calibration value; The measured temperature-independent term coefficient, temperature-dependent term compensation coefficient, and first reference temperature are used to... Substitute the polynomial signal solution model into the given model to complete the model calibration.

7. The method of using the reciprocal 3×3 fiber optic gyroscope according to claim 6, characterized in that, The theoretical output values ​​of the first interference beam P1, the second interference beam P2, and the third interference beam P3 are: ； ； ； in, , and These represent the DC amplitudes of the first, second, and third interference beams, respectively. , and These represent the AC amplitudes of the first, second, and third interference beams, respectively. and Indicates 3 3. The additional coupling phase shift introduced by the coupler (4), Indicates the gyroscope's sensitivity. This indicates the known angular velocity of the input gyroscope. This represents the attenuation coefficient of the fiber optic loop. This indicates the input power of the light source.

8. The method of using the reciprocal 3×3 fiber optic gyroscope according to claim 4, characterized in that, After one revolution, the third beam and the fourth beam are obtained from the second end of the single-mode fiber ring (6) and the first end of the single-mode fiber ring (6), respectively, as follows: The first beam and the second beam are simultaneously input into the first end of the single-mode fiber ring (6) and the second end of the single-mode fiber ring (6) in clockwise and counterclockwise directions, respectively. The Sagnac phase shift between the two beams is caused by the rotation of the fiber optic ring plane. The third and fourth beams are obtained.

9. The method of using the reciprocal 3×3 fiber optic gyroscope according to claim 8, characterized in that, The third and fourth beams return to the 3 3. Coupler (4) and interference occurs, specifically including: The third and fourth beams are at 3 Interference occurs in coupler (4), and is simultaneously affected by the inherent phase shift. The phase difference between the outputs of ports b1 and c1 and the output of port a1 is... and Interference light; The three interferometric optical signals contain the same common-mode interference factor. Since the third interferometric light P3, output from port a1 (the reciprocal terminal), has the lowest sensitivity at zero and is not affected by coupling phase shift interference, the third interferometric light P3 is used as the reference. By using differential operations to eliminate the influence of the common-mode factor, the transition term is obtained as follows: ； ； After differential operation, the transition term and the light source input power Attenuation coefficient of fiber optic loop Regardless, the solution of the polynomial signal model is completed through the aforementioned transition term.

10. The method of using the reciprocal 3×3 fiber optic gyroscope according to claim 9, characterized in that, The and It is controlled by a coupled phase shift-temperature model, which is: ； ； This indicates the coupling phase shift at a measured temperature of T. The value, This indicates the coupling phase shift at a measured temperature of T. The value, Indicated at the first reference temperature Down-coupled phase shift The value, Indicated at the first reference temperature Down-coupled phase shift The value, This is the temperature variation factor for the coupling phase shift.

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