A fiber-optic gyroscope Y waveguide nonlinearity index measuring device and a measuring method thereof

Abstract

The application relates to a fiber-optic gyroscope Y waveguide nonlinearity index measuring device, which comprises a light source, a fiber coupler, a measured Y waveguide, a fiber ring, a photoelectric detector, a measurement algorithm operator, a high-linearity voltage signal amplifier, a data collector and an upper computer; wherein the light source, the fiber coupler, the Y waveguide and the fiber ring are sequentially connected; the photoelectric detector is connected with the fiber coupler and the measurement algorithm operator; the high-linearity voltage signal amplifier is connected with the Y waveguide and the measurement algorithm operator respectively; the measurement algorithm operator is connected with the data collector; and the data collector is connected with the upper computer. The application can solve the problems that the Y waveguide nonlinearity index of the fiber-optic gyroscope is difficult to measure and cannot be quantitatively tested, and can effectively evaluate the quantitative relationship between the Y waveguide nonlinearity index and the threshold and scale factor nonlinearity indexes of the gyroscope.

Description

Technical Field

[0001] This invention belongs to the field of Y-waveguide measurement and evaluation, and relates to a device and method for measuring the Y-waveguide performance of an optical fiber gyroscope. Background Technology

[0002] Y-waveguides are crucial optical components in fiber optic gyroscopes, enabling functions such as polarization / analysis, beam splitting / combining, and phase modulation. Their nonlinearity directly impacts the gyroscope's threshold voltage, scaling factor nonlinearity, zero-bias stability, and random walk performance. This is especially true for high-precision gyroscopes, where the Y-waveguide's nonlinearity significantly affects the threshold voltage and scaling factor linearity, becoming a major limiting factor in their development.

[0003] Traditional Y-waveguides suffer from nonlinearity due to limitations in equipment and measurement methods, making it difficult to accurately measure this indicator. This often results in poor product performance in actual gyroscope products, severely restricting the first-pass yield and consistency of indicators in gyroscope production. Summary of the Invention

[0004] The technical problem solved by this invention is that it provides a device and method for measuring the nonlinear index of a fiber optic gyroscope Y-waveguide, which solves the problem that the nonlinear index of the Y-waveguide is difficult to measure and cannot be measured accurately.

[0005] The objective of this invention is achieved through the following technical solution: a device for measuring the nonlinear index of a fiber optic gyroscope Y-waveguide, comprising: a light source, a fiber optic coupler, a fiber optic ring, a photodetector, a measurement algorithm processor, and a data acquisition unit;

[0006] The light output from the light source passes through the fiber optic coupler and then enters the Y-waveguide and the light loop under test.

[0007] The photodetector converts the optical power signal into an analog voltage signal and sends it to the measurement algorithm processor.

[0008] The measurement algorithm processor: acquires the analog voltage signal from the photodetector and converts it into a digital signal; generates a modulated state sequence voltage signal and applies it to the Y-waveguide; and measures the Y-waveguide half-wave voltage parameter V in real time. Y The interferometer's open-loop angular rate measurement value W0, and based on the Y-waveguide half-wave voltage parameter V... Y The nonlinear index value of the Y-waveguide is calculated using the open-loop angular rate measurement value W0 from the interferometer.

[0009] The data acquisition unit receives data from the measurement algorithm processor.

[0010] Furthermore, the fiber optic coupler enables both beam splitting and beam combining.

[0011] Furthermore, the Y-waveguide enables light polarization, splitting and combining, optical phase modulation, and optical interference.

[0012] Furthermore, the fiber ring extends the polarization interference time and enhances the optical interference effect.

[0013] Furthermore, the aforementioned fiber optic gyroscope Y-waveguide nonlinear index measurement device also includes a voltage signal amplifier. The modulation state sequence voltage signal generated by the measurement algorithm operator is amplified by the voltage signal amplifier and then applied to the Y-waveguide. The modulation state signal generated by the modulation state sequence voltage signal generated by the measurement algorithm operator is a four-state modulation waveform that increases with a voltage growth rate a, so that the four-state modulation waveform is cyclically scanned n times within the modulation voltage range of 0-3π, where n≥4.

[0014] Furthermore, the voltage signal amplifier is a bipolar, high-linearity, low-distortion analog voltage amplifier with linearity better than 30ppm and distortion <0.01%.

[0015] Furthermore, the data acquisition unit converts the received data from the measurement algorithm processor into USB interface data.

[0016] Furthermore, the aforementioned fiber optic gyroscope Y-waveguide nonlinear index measurement device also includes a host computer, which receives and stores data sent by the data acquisition unit.

[0017] The measurement method using the aforementioned fiber optic gyroscope Y-waveguide nonlinear index measurement device includes:

[0018] The measurement algorithm's arithmetic unit generates a modulated sequence voltage signal;

[0019] A high-linearity voltage signal amplifier amplifies the modulated state sequence voltage signal without distortion and increases it at a voltage growth rate 'a', causing the four-state modulation waveform to cyclically scan n times within the 0-3π modulation voltage range. The measurement and calculation unit measures the Y-waveguide half-wave voltage parameter V in real time. Y The open-loop angular rate measurement value W0 of the interferometer; n≥4;

[0020] The measured Y-waveguide half-wave voltage parameter V Y Data processing is performed by comparing the repeatability of the n scan data and fitting the data according to the first-order function to obtain the first-order functions y(x1) and y(x2) at the maximum and minimum slopes respectively, and taking the slopes K1 and K2 of the first-order functions y(x1) and y(x2);

[0021] The parameter K3 is obtained by solving the standard deviation of the open-loop angular rate measurement W0 of the interferometer;

[0022] FFT calculation is performed on the open-loop angular rate measurement value W0 of the interferometer, and the parameter K4 is obtained by solving for the amplitude of the same frequency in n scan cycles of the data and corresponding to the frequency.

[0023] Calculate the nonlinear index values ​​of the Y-waveguide based on the slopes K1 and K2 and the parameters K3 and K4.

[0024] Furthermore, the Y-waveguide nonlinear index value K NL The calculation formula is as follows:

[0025]

[0026] Where A, B, and C are the weight values ​​corresponding to the three indicator data.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) This invention can solve the problem that the nonlinearity index of Y waveguide used in fiber optic gyroscopes is difficult to measure and cannot be quantified. It can effectively evaluate the quantitative relationship between the nonlinearity index of Y waveguide and the nonlinearity of gyroscope threshold and scaling factor, which is of great significance for gyroscope research, especially the development and production of high-precision gyroscopes. At the same time, it provides effective reference data for the optimization and improvement of Y waveguides.

[0029] (2) The Y-waveguide nonlinearity measurement method involved in this invention realizes the relationship between the modulation voltage applied to the Y-waveguide and the modulation phase output by the Y-waveguide by converting the measurement of the Y-waveguide nonlinearity index into the measurement of the interference phase of the interferometer.

[0030] (3) The measurement results of the nonlinear index of the Y-waveguide involved in this invention consist of the related index of the Y-waveguide half-wave voltage measurement value, the related index of the power spectral density function of the interferometric phase demodulation data (frequency domain index), and the related index of the standard deviation of the interferometric phase demodulation data. The evaluation of multiple indexes can achieve a more accurate and scientific evaluation and measurement of this index. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the fiber optic gyroscope Y-waveguide nonlinear index measurement device according to an embodiment of the present invention. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings:

[0033] The Y-waveguide is one of the most important light source components in a fiber optic gyroscope, and its performance directly affects the overall performance of the gyroscope. Specifically, the nonlinearity of the Y-waveguide directly impacts the gyroscope's threshold voltage, scaling factor, and other parameters. Currently, there are no instruments or devices available to measure this performance parameter of the Y-waveguide, which significantly affects the consistency of gyroscope performance during mass production.

[0034] A device for measuring the nonlinear index of a fiber optic gyroscope Y-waveguide includes: a light source 1, an optical fiber coupler 2, a Y-waveguide 3, an optical fiber ring 4, a photodetector 5, a high linearity voltage signal amplifier 6, a measurement algorithm processor 7, a data acquisition unit 8, and a host computer 9.

[0035] The light source 1, the fiber coupler 2, the Y-waveguide 3, and the fiber ring 4 are connected in sequence; the photodetector 5 is connected to the fiber coupler 2 and the measurement algorithm processor 7 respectively; the high linearity voltage signal amplifier 6 is connected to the Y-waveguide 3 and the measurement algorithm processor 7 respectively; and the data acquisition unit 8 is connected to the measurement algorithm processor 7 and the host computer 9 respectively.

[0036] Light source 1 outputs wavelength-stable light to fiber coupler 2, which performs the functions of splitting and combining light. Y waveguide 3 realizes light polarization, splitting and combining, optical phase modulation and optical interference. Fiber ring 4 extends the interference time of polarized light and enhances the optical interference effect. Photodetector 5 converts the optical power signal into an analog voltage signal and sends it to the measurement algorithm processor 7.

[0037] The measurement algorithm processor 7 acquires the analog voltage signal from the photodetector 5 and converts it into a digital signal. The measurement algorithm processor 7 generates a modulation sequence voltage signal via an FPGA, which is then amplified by a high-linearity voltage signal amplifier 6. The resulting modulation signal is a four-state modulation waveform that increases at a voltage growth rate of 0.1mV. This four-state modulation waveform is cyclically scanned four times within the 0-3π modulation voltage range and applied to the Y-waveguide 3. During this process, the measurement algorithm processor 7 measures the Y-waveguide half-wave voltage parameter V in real time. Y The open-loop angular rate measurement value W0 of the interferometer;

[0038] The data acquisition unit 8 receives data from the measurement algorithm processor 7 and converts it into USB interface data, which is then sent to the host computer 9. The host computer 9 then performs data acquisition and storage.

[0039] The high linearity voltage signal amplifier 6 is a bipolar, high linearity, low distortion analog voltage amplifier, which can effectively ensure the accuracy of the voltage applied to the Y waveguide.

[0040] A method for measuring the nonlinearity of a fiber optic gyroscope Y-waveguide includes the following steps:

[0041] Step 1: The measurement algorithm processor 7 generates a modulated sequence voltage signal through the FPGA;

[0042] Step 2: The high linearity voltage signal amplifier 6 amplifies the modulated state sequence voltage signal without distortion and increases it at a voltage growth rate of 0.1mV, so that the four-state modulation waveform is cyclically scanned 4 times in the modulation voltage range of 0-3π.

[0043] Step 3: During this process, the measuring unit 7 measures the Y-waveguide half-wave voltage parameter V in real time. Y The open-loop angular rate measurement value W0 of the interferometer;

[0044] Step 4: Measure the obtained Y-waveguide half-wave voltage parameter V. Y Data processing was performed by comparing the repeatability of the four scan data and fitting the data according to a first-order function to obtain the first-order functions y(x1) and y(x2) at the maximum and minimum slopes, respectively, and taking their slopes K1 and K2; the standard deviation of the interferometer open-loop angular rate measurement value W0 was calculated to obtain the parameter K3; FFT calculation was performed on the interferometer open-loop angular rate measurement value W0, and the amplitude of the same frequency in the four scan cycles was calculated to obtain the parameter K4;

[0045] Step 5: The nonlinear index value of the Y-waveguide can be calculated according to Formula 1.

[0046] Y-waveguide nonlinear index value K NL The calculation is shown in Formula 1;

[0047]

[0048] A, B, and C are the weight values ​​corresponding to the three indicator data.

[0049] Example:

[0050] Light source 1 can be selected as SLD (Superluminescent Diode). Coupler 2 is a 2*2 type dual-input dual-output polarization-maintaining coupler. The light source is fused to end A1 of coupler 2, and detector 5 is fused to end A2 of coupler 2. The Y1 and Y2 ends of the measured Y-waveguide 3 are fused to ends B1 and B2 of fiber optic ring 4 at 45 degrees, respectively. A single end of Y-waveguide 3 is fused to end A3 of fiber optic coupler 2. High linearity voltage signal amplifier 6 is connected to the positive and negative electrodes of Y-waveguide 3. Measurement algorithm processor 7 is connected to high linearity voltage signal amplifier 6 via a data bus. The host computer is developed using the LabWindows development environment.

[0051] In this embodiment, the PFGA model is Xilinx XC6SLX16-2CSG324I. The digital-to-analog converter in the high linearity voltage signal amplifier 6 is ADI's 18-bit DA chip LTC2757A. The data acquisition unit 8 is connected to the host computer 9 via USB cable. After the host computer 9 collects data and performs calculations, it gives the measured value of the Y-waveguide nonlinearity index.

[0052] In this embodiment, a method for measuring the nonlinearity of a fiber optic gyroscope Y-waveguide is as follows:

[0053] according to Figure 1The test equipment is connected, and the measurement algorithm processor 7 generates a modulation voltage signal through the FPGA, which is then applied to the Y-waveguide 3 through the high linearity voltage signal amplifier 6. The resulting modulation state is a four-state modulation waveform that increases at a voltage growth rate of 0.1mV, causing the four-state modulation waveform to cycle and scan 4 times within the modulation voltage range of 0-3π. During this process, the measurement algorithm processor 7 measures the half-wave voltage parameter V of the Y-waveguide in real time. Y And the open-loop angular rate measurement value W0 of the interferometer.

[0054] For the half-wave voltage parameter V of the Y-waveguide Y Data processing was performed by comparing the repeatability of the four scan data and fitting the data according to a first-order function to obtain the first-order functions y(x1) and y(x2) at the maximum and minimum slopes, respectively, and taking their slopes K1 and K2; the parameter K3 was obtained by solving the standard difference of the interferometer open-loop angular rate measurement value W0; the parameter K4 was obtained by performing FFT calculation on the interferometer open-loop angular rate measurement value W0 and solving for the amplitude of the same frequency in the four scan cycles.

[0055] Y-waveguide nonlinear index value K NL The calculation is shown in Formula 1;

[0056]

[0057] Where A, B, and C are the weight values ​​corresponding to the three indicator data. In this embodiment, A is 0.7, B is 0.1, and C is 0.2.

[0058] The above-described measuring device and method can be used to measure the nonlinear properties of the Y-waveguide, achieving the following objectives:

[0059] (1) Solving the problem that the nonlinear index of Y waveguide is difficult to measure and cannot be quantitatively evaluated is of great importance for the development and optimization of Y waveguide and the development and production of fiber optic gyroscope.

[0060] (2) It provides an important basis for the research of higher precision gyroscopes and is of great significance for solving the dead zone problem of gyroscopes and improving the linearity of gyroscope scaling factors.

[0061] The measurement of Y-waveguide nonlinearity is evaluated using multiple metrics, including the half-wave voltage measurement, the power spectral density function of the interferometric phase demodulation data, and the standard deviation of the open-loop angular rate measurement, thereby improving measurement accuracy. This method transforms the measurement of Y-waveguide nonlinearity into an indirect measurement of related metrics by measuring the open-loop angular rate using an interferometer, thus addressing the challenge of measuring these metrics when they are difficult or impossible to measure. Simultaneously, it converts the evaluation of Y-waveguide nonlinearity into a frequency domain evaluation (power spectral density function of the interferometric phase demodulation data), resolving the problem of difficult or inaccurate time-domain evaluation of Y-waveguide metrics at high operating frequencies, thus better achieving the target measurement.

[0062] The high linearity voltage signal amplifier involved in this invention has good linearity, low distortion, and zero crossover distortion, and can generate a simulated voltage change rate of less than 0.1mV, effectively avoiding test result errors caused by nonlinear factors introduced by external circuits. The high linearity voltage signal amplifier and the measurement algorithm processor involved in this invention can accurately scan the modulation state applied on the Y-waveguide within the 0-3π modulation voltage range, and the scanning range covers the 0-2π modulation voltage, effectively solving the problem of evaluating the nonlinear index of the Y-waveguide caused by the reset error during the 2π reset of the Y-waveguide in existing measurement methods.

[0063] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for measuring the nonlinear index of a fiber optic gyroscope Y-waveguide, characterized in that, include: Light source (1), fiber optic coupler (2), fiber optic ring (4), photodetector (5), measurement algorithm processor (7), data acquisition unit (8); The light source (1) outputs light, which enters the Y waveguide (3) and the light ring (4) under test after passing through the fiber coupler (2); The photodetector (5) converts the optical power signal into an analog voltage signal and sends it to the measurement algorithm processor (7); The measurement algorithm processor (7) acquires the analog voltage signal from the photodetector (5) and converts it into a digital signal; generates a modulated state sequence voltage signal and applies it to the Y-waveguide (3); and measures the Y-waveguide half-wave voltage parameter V in real time. Y The interferometer's open-loop angular rate measurement value W0, and based on the Y-waveguide half-wave voltage parameter V... Y The nonlinear index value of the Y-waveguide is calculated using the open-loop angular rate measurement value W0 from the interferometer. The data acquisition unit (8) receives data from the measurement algorithm processor (7); The fiber optic gyroscope Y-waveguide nonlinear index measurement device further includes a voltage signal amplifier (6). The modulation state sequence voltage signal generated by the measurement algorithm operator (7) is applied to the Y-waveguide (3) after being amplified by the voltage signal amplifier (6). The modulation state signal generated by the modulation state sequence voltage signal generated by the measurement algorithm operator (7) after being amplified by the voltage signal amplifier (6) is a four-state modulation waveform that increases with a voltage growth rate a, so that the four-state modulation waveform is cyclically scanned n times in the modulation voltage range of 0-3π, where n≥4.

2. The fiber optic gyroscope Y-waveguide nonlinear index measurement device according to claim 1, characterized in that, The fiber optic coupler (2) performs the functions of splitting and combining light.

3. The fiber optic gyroscope Y-waveguide nonlinear index measurement device according to claim 1, characterized in that, The Y-waveguide (3) enables light polarization, splitting and combining, phase modulation and interference.

4. The fiber optic gyroscope Y-waveguide nonlinear index measurement device according to claim 1, characterized in that, The fiber ring (4) extends the polarization interference time and enhances the optical interference effect.

5. The fiber optic gyroscope Y-waveguide nonlinear index measurement device according to claim 1, characterized in that: The voltage signal amplifier (6) is a bipolar, high linearity, low distortion analog voltage amplifier with linearity better than 30ppm and distortion <0.01%.

6. The fiber optic gyroscope Y-waveguide nonlinear index measurement device according to claim 1, characterized in that, The data acquisition unit (8) converts the received data from the measurement algorithm processor (7) into USB interface data.

7. The fiber optic gyroscope Y-waveguide nonlinear index measurement device according to claim 1, characterized in that, It also includes a host computer (9), which receives and stores the data sent by the data collector (8).

8. A measurement method using a fiber optic gyroscope Y-waveguide nonlinear index measurement device as described in any one of claims 1 to 7, characterized in that, include: The measurement algorithm arithmetic unit (7) generates a modulated state sequence voltage signal; The voltage signal amplifier (6) amplifies the modulated voltage signal without distortion and increases it at a voltage growth rate a, so that the four-state modulated waveform is cyclically scanned n times within the 0-3π modulation voltage range. The measurement arithmetic unit (7) measures the Y-waveguide half-wave voltage parameter V in real time. Y The open-loop angular rate measurement value W0 of the interferometer; n≥4; The measured Y-waveguide half-wave voltage parameter V Y Data processing is performed by comparing the repeatability of the n scan data and fitting the data according to the first-order function to obtain the first-order functions y(x1) and y(x2) at the maximum and minimum slopes respectively, and taking the slopes K1 and K2 of the first-order functions y(x1) and y(x2); The parameter K3 is obtained by solving the standard deviation of the open-loop angular rate measurement W0 of the interferometer; FFT calculation is performed on the open-loop angular rate measurement value W0 of the interferometer, and the parameter K4 is obtained by solving for the amplitude of the same frequency in n scan cycles of the data and corresponding to the frequency. Calculate the nonlinear index values ​​of the Y-waveguide based on the slopes K1 and K2 and the parameters K3 and K4.

9. The measurement method according to claim 8, characterized in that, The nonlinear index value K of the Y-waveguide NL The calculation formula is as follows: Where A, B, and C are the weight values ​​corresponding to the three indicator data.

Images