Light source self-coherence function online calibration device and method based on gain autonomous switching

Abstract

The present application relates to the technical field of fiber-optic gyroscope, and provides a light source self-coherence function online calibration device and method based on gain autonomous switching, and the test result can directly reflect the light source spectrum time coherence, which is important for analyzing the light source characteristics and determining the additional effect of the light path. The calibration device outputs the rotation speed feedback signal of the fiber-optic gyroscope under low gain and outputs the large amplitude modulation voltage signal under high gain through the gain autonomous switching module, and the signal is applied to the Y waveguide. The amplitude of the modulation voltage signal is changed by the integrated digital circuit, the phase difference of the two interference main lights is changed by the Y waveguide modulation, and the change of the light source self-coherence function is calibrated online. The present application realizes the online detection requirement of the fiber-optic gyroscope without disassembly, and the test method is simple and has high reliability.

Description

Technical Field

[0001] This invention relates to the field of fiber optic gyroscope technology, and in particular to an online calibration method for the source coherence function of light sources based on gain autonomous switching. Background Technology

[0002] Fiber optic gyroscopes are fiber optic angular velocity sensors based on the Sagnac effect. They possess advantages such as wide accuracy coverage, large measurement range, long lifespan, and high reliability, and are widely used in military fields such as missiles, aircraft, and armored vehicles, as well as civilian fields (such as oil and coal mining exploration). While fiber optic gyroscopes have demonstrated superior performance in practical applications, specific errors, such as scaling factor drift caused by variations in the average wavelength of the light source, relative intensity noise of the light source, and residual non-reciprocal errors in the optical path, limit their performance in high-precision applications. Therefore, there is an urgent need for an online error detection method capable of handling fiber optic gyroscopes under various conditions, including long-term use, storage, and operation in special environments.

[0003] Fiber optic gyroscopes commonly utilize broadband light sources, which feature wide output spectra, high power, and small divergence angles. Unlike monochromatic light sources where interference fringes are cosine functions, broadband light sources contain light of different wavelengths, resulting in varying fringe spacing for different wavelengths. As the order of the interference fringes increases, the fringes overlap, reducing contrast and eventually leading to a loss of coherence. Utilizing this finite coherence, non-reciprocal phase errors caused by polarization effects, Kerr effects, backscattering, and reflection can be eliminated to some extent, effectively improving the accuracy of the fiber optic gyroscope. The coherence of a broadband light source is determined by its spectrum, specifically the distribution of wavelengths it contains; however, spectral measurements typically require specialized instruments, i.e., spectrometers, which cannot meet the requirements for online, non-disassembly-based testing of fiber optic gyroscopes. Summary of the Invention

[0004] This invention provides an online calibration method for the optical source coherence function based on gain autonomous switching, which solves the problem of online error detection under various conditions such as long-term use, storage and operation in special environments of fiber optic gyroscopes in the prior art, and the problem that it cannot meet the requirement of online detection of fiber optic gyroscopes without disassembly.

[0005] The specific technical solution of the present invention is as follows:

[0006] The optical source coherence function online calibration device based on gain autonomous switching includes: a light source, a detector, a coupler, a Y-waveguide, an optical fiber ring, a preamplifier circuit, an analog-to-digital converter (AD), an integrated digital circuit, a dual modulation loop module, and a gain autonomous switching module; the dual modulation loop module includes a closed-loop feedback loop and a modulation signal generation loop, which are located between the integrated digital circuit and the gain autonomous switching module; the gain autonomous switching module is located between the dual modulation loop module and the Y-waveguide.

[0007] Furthermore, the input signals of the dual modulation loop module are all set by integrated digital circuits; the closed-loop feedback loop consists of a digital-to-analog converter DA1 and a DA1 driver circuit, which generates an analog voltage signal for the normal closed-loop operation of the fiber optic gyroscope; the modulation signal generation loop includes a digital-to-analog converter DA2 and a DA2 driver circuit, which generates an analog voltage signal composed of multiple sets of square waves with different amplitudes.

[0008] Furthermore, the digital-to-analog converters DA1 and DA2 convert digital signals into differential analog current signals; the DA1 drive circuit and DA2 drive circuit convert the differential analog current signals into differential analog voltage signals.

[0009] Furthermore, the gain autonomous switching module consists of two operational amplifiers powered by ±15V. In low-gain mode, the output of the modulation signal generation circuit is zero, and the output voltage of the closed-loop feedback circuit is amplified by the gain autonomous switching module at low gain (typical value of 1) before being output. In high-gain mode, the output of the closed-loop feedback circuit is zero, and the output voltage of the modulation signal generation circuit is amplified by the gain autonomous switching module at high gain (typical value of 5) before being output.

[0010] The online calibration method based on the aforementioned online self-coherence function calibration device for light sources includes:

[0011] S1 is controlled by integrated digital circuit software. The input signal of the modulation signal generation loop is set to zero. The closed-loop feedback signal is applied to the Y waveguide through the closed-loop feedback loop. The gain autonomous switching module is in low gain mode. The reference voltages of the digital-to-analog converters DA1 and DA2 are automatically adjusted by the second closed loop of the fiber optic gyroscope to calibrate the relationship between the modulation voltage signal applied to the Y waveguide and the phase difference between the two interference main beams generated by the Y waveguide.

[0012] S2 adds a modulation voltage signal generation module for detecting the self-coherence function of the light source. Controlled by integrated digital circuit software, the input signal of the closed-loop feedback loop is set to zero. Based on the relationship between the modulation voltage signal applied to the Y-waveguide and the phase difference generated by the two interfering main beams from the Y-waveguide, the input signal of the modulation signal generation loop is set to a digital signal containing square waves of different amplitudes. The gain-auto-switching module is in high-gain mode. The analog voltage signal generated by the modulation signal generation loop from the digital signal is amplified by the gain-auto-switching module and applied to the Y-waveguide, causing the two interfering main beams to generate a phase difference Δφ of different amplitudes. g (t), to obtain the voltage value output by the corresponding detector;

[0013] S3 calculates the optical power reaching the detector under different phase differences based on the relationship between the voltage value output by the corresponding detector and the optical power reaching the detector, obtains the relationship between the optical power reaching the detector and the phase difference between the two interfering principal beams, and obtains the self-coherence function curve of the light source by plotting the relationship between the optical power reaching the detector and the phase difference between the two interfering principal beams.

[0014] After S4 applies the modulation voltage signal detected by the self-coherence function of the light source for one cycle, it jumps to S1, automatically adjusts to the corresponding accurate 2π voltage, and continues to S2 and generates the Y waveguide modulation voltage signal through the digital-to-analog converter DA2. Based on the test and calculation results of S3, the self-coherence function of the light source is calibrated online.

[0015] Furthermore, S2 adds a modulation voltage signal generation module for detecting the self-coherence function of the light source, which is based on a modulation signal generation circuit and a gain autonomous switching module. The modulation signal generation circuit converts digital signals containing square waves of different amplitudes into differential analog voltage signals, which are then amplified (typically by 5 times) by the gain autonomous switching module to generate the modulation voltage signal.

[0016] Furthermore, the phase difference between the two interfering main beams generated by Y-waveguide modulation is obtained by applying the modulation voltage signal output by the gain autonomous switching module to the Y-waveguide.

[0017] Furthermore, the phase difference between the two main interfering beams corresponds to the digital quantity of the input signal of the digital-to-analog converter DA2, and the amplitude of the digital quantity is set by the integrated digital circuit. The relationship between the modulation voltage signal applied to the Y-waveguide and the phase difference between the two main interfering beams generated by the Y-waveguide is calibrated by automatically adjusting the reference voltage of the digital-to-analog converters DA1 and DA2 through the second closed loop of the fiber optic gyroscope.

[0018] Furthermore, in S2, the two interfering principal beams produce a phase difference Δφ with different amplitudes. g (t), including:

[0019] Δφ g (t) is a set containing n groups of different amplitudes but the same frequency (v). k / 2, v k The phase difference signal is in square wave form (the intrinsic frequency of the fiber optic gyroscope), where the amplitude varies from 0 to φ. g The amplitude variation step size φ1 is adjusted as needed. For the detection signal Δφ g (t) contains the number of different amplitudes.

[0020] Furthermore, in step S3, the self-coherence function curve of the light source is obtained by plotting, which contains a total of 2n data points, where n is Δφ. g(t) contains different amplitude values, and the optical path difference varies within a range of -2φ. g ~2φ g The range is 4φ g , where φ g For Δφ g (t) contains the maximum magnitude.

[0021] The advantages of this invention compared to the prior art are:

[0022] 1. A method for online calibration of the self-coherence function of fiber optic gyroscopes without disassembly is proposed. Accurate measurement of the self-coherence function of broadband light sources is of great significance for analyzing light source characteristics and determining additional errors in the optical path.

[0023] 2. It does not rely on additional equipment such as spectrometers, white light interferometers, or turntables, and requires no complex mechanical or optical components. The hardware circuit configuration is simple and does not affect the normal operation of the fiber optic gyroscope. Compared with typical fiber optic gyroscope operating schemes, the hardware only requires the addition of one digital-to-analog converter (DA) and its drive circuit and adder. The measurement results are not limited by the turntable resolution, maximum turntable speed, or the measurement accuracy of spectrometers, white light interferometers, etc. The testing process is simple and highly reliable.

[0024] 3. The added self-coherent function detection signal can be manually programmed and added at any time, which can meet the needs of power-on self-test or periodic calibration. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart of the online calibration method for light source coherence function based on gain autonomous switching provided by the present invention;

[0027] Figure 2a This is a schematic diagram of the normalized spectral intensity distribution of the ASE light source;

[0028] Figure 2b This is a schematic diagram of the normalized light intensity of the interference signal;

[0029] Figure 3 The self-coherence function detection signal Δφ provided by this invention g Timing diagram;

[0030] Figure 4 This is a schematic diagram of the online calibration device for self-coherence functions provided by the present invention;

[0031] Figure 5 This is a circuit diagram of a dual DA and driving circuit module for self-coherence function detection provided by the present invention;

[0032] Figure 6 This is the detector output diagram provided by the present invention under the application of detection square waves of different amplitudes on the Y-waveguide. Detailed Implementation

[0033] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0034] The following will describe in detail, with reference to the accompanying drawings, the online calibration method for the source coherence function of the light source based on gain autonomous switching according to the present invention.

[0035] An online self-coherence function calibration device based on gain autonomous switching includes a light source, detector, coupler, Y-waveguide, fiber optic ring, preamplifier circuit, analog-to-digital converter (AD), integrated digital circuit, dual modulation loop module, and gain autonomous switching module. The dual modulation loop module consists of an AD converter (DA1), an AD converter (DA2), a DA1 driver circuit, and a DA2 driver circuit. The gain autonomous switching module is implemented using an adder circuit. In low-gain mode, the AD converter (DA2) and its driver circuit generate a phase difference between two interferometric main beams equivalent to their rotational speed, used for online self-coherence function calibration.

[0036] The coupler is used to split the light emitted by the light source into two, with one beam output to the air head and the other output to the Y waveguide;

[0037] The Y-waveguide and fiber optic ring are used to polarize the light output from the coupler and entering the Y-waveguide, splitting it into two beams that propagate clockwise and counterclockwise through the fiber optic ring, respectively, generating a Sagnac phase difference proportional to the rotational angular velocity. Based on the electro-optic modulation effect of the Y-waveguide, a modulation voltage signal used for fiber optic ring operation and self-coherence function detection is applied to the Y-waveguide, adding a modulation phase difference to the two interfering beams and converting the optical phase change into an optical intensity change. After the two interfering beams propagate one revolution along the fiber optic ring, they are combined into one beam after interfering through the Y-waveguide and reach the detector via the coupler.

[0038] The detector is used for photoelectric detection, converting light intensity signals into voltage signals;

[0039] The preamplifier circuit is used to filter and amplify the voltage signal before inputting it into the analog-to-digital converter (AD).

[0040] The analog-to-digital converter (AD) is used to convert the received voltage signal into a digital signal and output it to the integrated digital circuit.

[0041] The digital-to-analog converter DA1 is used to convert a signal containing the sum of a 2π reset modulation signal and a feedback signal; the digital-to-analog converter DA2 is used to convert a self-coherent function detection signal composed of multiple sets of square waves with different amplitudes.

[0042] The integrated digital circuit demodulates the digital signal to obtain the rotational speed result; the integrated digital circuit outputs a digital signal for normal operation of the fiber optic ring to the digital-to-analog converter DA1, and outputs a digital signal for self-coherence function detection of the light source to the digital-to-analog converter DA2. The current signals output by the digital-to-analog converters DA1 and DA2 are respectively converted into differential voltages by the DA1 driving circuit and the DA2 driving circuit, and then amplified by the gain autonomous switching module and applied to the Y waveguide.

[0043] On the other hand, the present invention also provides an online calibration method for the source coherence function of light based on gain autonomous switching. Figure 1 This is a flowchart of the online calibration method for the source coherence function of light source based on gain-autonomous switching Y-waveguide modulation disclosed in this invention, including the following steps:

[0044] S1 is controlled by integrated digital circuit software. The input signal of the modulation signal generation loop is set to zero. The closed-loop feedback signal is applied to the Y waveguide through the closed-loop feedback loop. The gain autonomous switching module is in low gain mode. The reference voltages of the digital-to-analog converters DA1 and DA2 are automatically adjusted by the second closed loop of the fiber optic gyroscope to calibrate the relationship between the modulation voltage signal applied to the Y waveguide and the phase difference between the two interference main beams generated by the Y waveguide.

[0045] S2 adds a modulation voltage signal generation module for detecting the self-coherence function of the light source. Controlled by integrated digital circuit software, the input signal of the closed-loop feedback loop is set to zero. Based on the relationship between the modulation voltage signal applied to the Y-waveguide and the phase difference generated by the two interfering main beams from the Y-waveguide, the input signal of the modulation signal generation loop is set to a digital signal containing square waves of different amplitudes. The gain-auto-switching module is in high-gain mode. The analog voltage signal generated by the modulation signal generation loop from the digital signal is amplified by the gain-auto-switching module and applied to the Y-waveguide, causing the two interfering main beams to generate a phase difference Δφ of different amplitudes. g (t), to obtain the voltage value output by the corresponding detector;

[0046] S3 calculates the optical power reaching the detector under different phase differences based on the relationship between the voltage value output by the corresponding detector and the optical power reaching the detector, obtains the relationship between the optical power reaching the detector and the phase difference between the two interfering principal beams, and obtains the self-coherence function curve of the light source by plotting the relationship between the optical power reaching the detector and the phase difference between the two interfering principal beams.

[0047] After S4 applies the modulation voltage signal detected by the self-coherence function of the light source for one cycle, it jumps to S1, automatically adjusts to the corresponding accurate 2π voltage, and continues to S2 and generates the Y waveguide modulation voltage signal through the digital-to-analog converter DA2. Based on the test and calculation results of S3, the self-coherence function of the light source is calibrated online.

[0048] The S2 module adds a modulation voltage signal generation module, which is based on the modulation signal generation circuit and the gain autonomous switching module. It includes a digital-to-analog converter DA2 and a DA2 driver circuit, as well as a ±15V powered gain autonomous switching module. The digital-to-analog converter DA2 converts digital signals containing square waves of different amplitudes into differential analog current signals. The differential analog current signals are converted into differential analog voltage signals by the digital-to-analog converter DA2 driver circuit. The configuration of the digital-to-analog converter DA2 and the DA2 driver circuit is the same as that of the digital-to-analog converter DA1 and the DA1 driver circuit. The gain autonomous switching module amplifies the signal (typically 5 times) to generate a modulation voltage signal, which is applied to the Y waveguide. The relationship between the modulation voltage signal applied to the Y waveguide calibrated in S1 and the phase difference generated by the two interfering main beams produced by the Y waveguide is used as the reference voltage reference for the digital-to-analog conversion of DA2.

[0049] The phase difference between the two interfering main beams generated by Y-waveguide modulation is obtained by generating modulation voltage signals of different amplitudes through the digital-to-analog converter DA2 and DA2 driving circuit, which can meet the measurement requirements of the self-coherence function under large phase difference, and simultaneously applying the modulation voltage signal for detecting the self-coherence function of the light source to the Y-waveguide.

[0050] The gain-auto-switching module, powered by ±15V, superimposes the voltages output from the DA1 and DA2 driving circuits to generate an equivalent large phase difference between two high-speed interferometric main beams, which is used for online calibration of the self-coherence function.

[0051] The phase difference of the interferometric principal beam in S2 corresponds to the amplitude of the self-coherence function detection signal, and is generated by modulation voltage signals of different amplitudes.

[0052] The phase difference Δφ between the two interferometric principal beams generated by the Y waveguide in S2 g Modulation voltage signal ΔV applied to the Y waveguide g The relationship is as follows:

[0053]

[0054] Where, k Y L is the refractive index variation coefficient of the Y-waveguide crystal, expressed in parts per volt; Y λ is the length of the area affected by the refractive index change, in meters; λ is the average wavelength of the light source, in meters.

[0055] The optical power reaching the detector in S3 is directly proportional to the intensity of the broadband light source interference signal. The relationship between the intensity of the broadband light source interference signal and the Gaussian envelope of the self-coherence function is as follows:

[0056] I(τ d ) = I bg [1+γg(τ d cos(2πτ) d v0)]

[0057] Among them, I bg Let γ be the background light intensity, γ be the fringe visibility, g(z) be the Gaussian envelope of the self-coherence function, and τ be the background light intensity. d v0 is the time delay between the two interfering beams and the center frequency of the light source.

[0058] The step S4 involves applying a modulation voltage signal detected by the self-coherence function of the light source onto the Y-waveguide, including:

[0059] Based on the push-pull structure of the Y-waveguide, Δφ g (t)=Δφ g1 (t)-Δφ g2 (t), Δφ g1 (t) and Δφ g2 (t) represents the phase values ​​of the two beams of light propagating clockwise and counterclockwise through the Y-waveguide to the gyroscope, respectively, Δφ. g (t) is a phase difference signal consisting of n sets of square wave forms with different amplitudes but the same frequency, and the amplitude range is 0 to φ. g The frequency of the square wave signal corresponding to each amplitude is v. k / 2(v k (where Δφ is the intrinsic frequency of the fiber optic gyroscope), and the square wave signals of different amplitudes added correspond to a set of interference phase differences; g1 (t) and Δφ g2 The step size φ1 of the amplitude change of (t) is adjusted as needed. For the detection signal Δφ g (t) contains different amplitude values, which are detected by the signal Δφ. g The self-coherence function described by (t) contains 2n data points, and the optical path difference varies from -2φ. g ~2φ g The range is 4φg .

[0060] Example 1

[0061] A specific embodiment of the present invention, such as Figure 3-6 This paper discloses an online calibration method for the self-coherence function of an optical source based on gain autonomous switching. In this embodiment, the modulation voltage applied to the Y waveguide includes the sum of the modulation signal and the feedback signal converted by DA1 (which is the same as the scheme in mainstream closed-loop fiber optic gyroscopes), and the self-coherence function detection signal ΔV composed of multiple sets of square waves with different amplitudes converted by DA2. g .

[0062] Before online calibration of the self-coherent function, firstly, the output of DA1 contains the sum of the modulation signal and the feedback signal of the 2π reset, the output of DA2 is 0, the gain auto-switching module is in low gain mode, and the 2π voltage is automatically adjusted to an accurate value through the second closed loop of the gyroscope to calibrate Δφ. g With ΔV g The relationship.

[0063] Then, DA1 output is set to 0, DA2 outputs the autocoherence function detection signal, the gain autonomous switching module is in high-gain mode, and the autocoherence function detection signal Δφ is added to the Y waveguide. g (t), its timing diagram is as follows Figure 3 As shown. Where, Δφ g1 (t) and Δφ g2 (t) The signals represent the phase values ​​of the two beams of light propagating clockwise and counterclockwise on the gyroscope, respectively, generated by the Y-waveguide. Based on the push-pull structure of the Y-waveguide, Δφ g (t)=Δφ g1 (t)-Δφ g2 (t). Δφ g (t) is a detection signal containing n sets of square wave signals with different amplitudes but the same frequency (1 / 2τ). Where Δφ g (t) The frequency of amplitude change is v amp (v amp = 1 / t, where t is the period of amplitude variation, and the amplitude variation range is 0 to φ. g The frequency of the square wave signal corresponding to each amplitude is v. k / 2(v k =1 / (2τ) is the intrinsic frequency of the fiber optic gyroscope. Each added square wave signal of different amplitudes corresponds to a set of interference phase differences (e.g., the square wave signal voltage value is V). 2π The corresponding interference phase difference is 2π; the square wave signal voltage is -V. 2π Corresponding interference phase difference -2π). By detecting the signal Δφ g (t) depicts the self-coherence function, containing 2n data points, with the optical path difference varying from -2φ.g ~2φ g The range is 4φ g .

[0064] The publicly available schematic diagram of the online calibration device for the coherence function of the light source is shown below. Figure 4 As shown, the light emitted from the source is split into two by a 2×2 coupler. One beam is output to the air head, while the other beam, after being polarized by the Y-waveguide, is split into two coherent beams with opposite propagation directions. Based on the electro-optic modulation effect of the Y-waveguide, a modulation voltage signal, used for the closed-loop operation and self-coherence function detection of the fiber optic gyroscope, is applied to the Y-waveguide, introducing a modulation phase difference into the two interfering beams. The two beams propagate through the fiber optic loop in clockwise and counterclockwise directions, respectively, generating a Sagnac phase difference proportional to the rotational angular velocity. After entering the Y-waveguide and interfering, they merge into one beam, converting the phase change into an intensity change. Then, they reach the detector via the coupler for photoelectric detection. The detector converts the intensity signal into an analog voltage signal, which is then processed by the subsequent preamplifier circuit for filtering and amplification. Finally, the signal undergoes an AD conversion, converting the analog signal into a digital signal, which is output to the integrated digital circuit for modulation and demodulation to obtain the rotational speed result. Meanwhile, the integrated digital circuit outputs a digital signal for the normal closed-loop operation of the gyroscope at DA1, and an additional digital signal for the detection of the self-coherence function of the light source at DA2. After being converted into analog current signals, they are respectively converted into differential analog voltages by the drive circuit. After being amplified by the gain autonomous switching module, they are applied to the Y waveguide to modulate the phase of the light passing through the Y waveguide.

[0065] Figure 4 The device within the solid box is consistent with mainstream fiber optic gyroscope solutions, used for speed testing and automatic adjustment of the closed-loop and second closed-loop circuits, achieving digital closed-loop adjustment. To achieve online calibration of the self-coherence function, a module for measuring the self-coherence function of the light source, within the dashed box, was added to the original hardware. This includes adding an additional DA circuit and driver circuit to implement a dual modulation loop, as well as a gain-auto-switching module based on an adder circuit powered by ±15V. The circuit schematics for the two DA circuits are shown below. Figure 5 As shown, the DA2 output, controlled by an integrated digital circuit, generates a square wave modulation signal with varying amplitude to change the input phase difference of the optical path. The DA2 converts the input digital signal into a differential analog current signal; this differential analog current signal is then converted into a differential analog voltage signal by a differential amplifier (such as AD8138). The two differential conversion circuits are completely identical. After being amplified by a gain-switching module, the signal is applied to the Y-waveguide.

[0066] When a square wave of different amplitude is applied to the Y-waveguide using DA2 and its driving circuit, the detector output diagrams under different amplitude square waves are shown below. Figure 6As shown, the self-coherent function detection signal contains multiple sets of square wave signals with different amplitudes but the same frequency. Each set of square waves has a frequency of 1 / 2τ. Taking a detection signal amplitude variation frequency of 1Hz as an example, each set of square waves contains 1 / 2τ periods. The amplitude of the square waves starts from zero and varies in a set step size (e.g., 100mV) until the square wave amplitude equals the half-wave voltage of the Y-waveguide. At this point, the light intensity reaching the detector is 0.

[0067] The detection circuit was used to detect different output voltage values ​​V of the detector under different square wave detection signals (corresponding to different phase differences of the interferometric principal beams). D .according to The optical power P of the detector can be obtained. D Phase difference Δφ between the two interfering principal beams g The function curve is given by η, where η is the photoelectric conversion efficiency of the detector, and R is the function curve. f This represents the detector's resistance value.

[0068] All of the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments of this application, and will not be described in detail here.

[0069] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An online calibration method for a light source autocoherence function online calibration device based on gain autonomous switching, wherein the light source autocoherence function online calibration device comprises: The system comprises a light source, a detector, a coupler, a Y-waveguide, an optical fiber ring, a preamplifier circuit, an analog-to-digital converter (AD), an integrated digital circuit, a dual modulation loop module, and a gain-autonomous switching module. The dual modulation loop module includes a closed-loop feedback loop and a modulation signal generation loop, positioned between the integrated digital circuit and the gain-autonomous switching module. The gain-autonomous switching module is positioned between the dual modulation loop module and the Y-waveguide. The online calibration method includes: S1 is controlled by integrated digital circuit software. The input signal of the modulation signal generation loop is set to zero. The closed-loop feedback signal is applied to the Y waveguide through the closed-loop feedback loop. The gain autonomous switching module is in low gain mode. The reference voltages of the digital-to-analog converters DA1 and DA2 are automatically adjusted by the second closed loop of the fiber optic gyroscope to calibrate the relationship between the modulation voltage signal applied to the Y waveguide and the phase difference between the two interference main beams generated by the Y waveguide. S2 adds a modulation voltage signal generation module for detecting the self-coherence function of the light source. Controlled by integrated digital circuit software, the input signal of the closed-loop feedback loop is set to zero. Based on the relationship between the modulation voltage signal applied to the Y-waveguide and the phase difference generated by the two interfering main beams from the Y-waveguide, the input signal of the modulation signal generation loop is set to a digital signal containing square waves of different amplitudes. The gain-auto-switching module is in high-gain mode. The analog voltage signal generated by the modulation signal generation loop from the digital signal is amplified by the gain-auto-switching module and applied to the Y-waveguide, causing the two interfering main beams to generate phase difference signals of different amplitudes. To obtain the voltage value output by the corresponding detector; S3 Based on the relationship between the voltage value output by the corresponding detector and the optical power reaching the detector, calculate the optical power reaching the detector under different phase differences, obtain the relationship between the optical power reaching the detector and the phase difference between the two interfering principal beams, and obtain the self-coherence function curve of the light source by plotting the relationship between the optical power reaching the detector and the phase difference between the two interfering principal beams. S4 automatically adjusts to the corresponding accurate 2 π After voltage measurement, S2 continues and the Y-waveguide modulated voltage signal is generated through the digital-to-analog converter DA2. Based on the test and calculation results of S3, the online calibration of the light source's autocoherence function is achieved.

2. The online calibration method according to claim 1, characterized in that, The S2 module adds a modulation voltage signal generation module for detecting the self-coherence function of the light source, which is based on the modulation signal generation circuit and the gain autonomous switching module. The modulation signal generation circuit converts the digital signal containing square waves of different amplitudes into a differential analog voltage signal, which is then amplified by the gain autonomous switching module to generate the modulation voltage signal.

3. The online calibration method according to claim 1, characterized in that, The phase difference between the two interfering main beams generated by Y-waveguide modulation is obtained by applying the modulation voltage signal output by the gain autonomous switching module to the Y-waveguide.

4. The online calibration method according to claim 1, characterized in that, The phase difference between the two main interfering beams corresponds to the digital value of the input signal of the digital-to-analog converter DA2, and the amplitude of the digital value is set by the integrated digital circuit. The relationship between the modulation voltage signal applied to the Y-waveguide and the phase difference between the two main interfering beams generated by the Y-waveguide is calibrated by automatically adjusting the reference voltage of the digital-to-analog converters DA1 and DA2 through the second closed loop of the fiber optic gyroscope.

5. The online calibration method according to claim 1, characterized in that, In S2 For a containing n A set of phase difference signals in square wave form with different amplitudes but the same frequency, wherein the frequency is half the intrinsic frequency of the fiber optic gyroscope, and the amplitude varies from 0 to... Amplitude change step size Adjust as needed. n is It includes different amplitude values.

6. The online calibration method according to claim 1, characterized in that, The graph obtained in S3 is the self-coherence function curve of the light source, which contains 2n data points, and the range of optical path difference is... The range is ,in, for The maximum amplitude included.

7. The online calibration method according to claim 1, characterized in that, The input signals of the dual modulation loop module are all set by integrated digital circuits; the closed-loop feedback loop consists of a digital-to-analog converter DA1 and a DA1 driver circuit, which generates an analog voltage signal for the normal closed-loop operation of the fiber optic gyroscope; the modulation signal generation loop includes a digital-to-analog converter DA2 and a DA2 driver circuit, which generates an analog voltage signal composed of multiple sets of square waves with different amplitudes.

8. The online calibration method according to claim 7, characterized in that, Digital-to-analog converters DA1 and DA2 convert digital signals into differential analog current signals; DA1 driver circuit and DA2 driver circuit convert differential analog current signals into differential analog voltage signals.

9. The online calibration method according to claim 8, characterized in that, The gain-auto-switching module consists of two operational amplifiers powered by ±15V. In low-gain mode, the output of the modulation signal generation circuit is zero, and the output voltage of the closed-loop feedback circuit is amplified by the gain-auto-switching module at low gain before being output. In high-gain mode, the output of the closed-loop feedback circuit is zero, and the output voltage of the modulation signal generation circuit is amplified by the gain-auto-switching module at high gain before being output.

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