A binary modulation deep optical path power compensation system and method for fiber optic gyroscope

Abstract

The present invention discloses a system and method for compensating the optical path power of a fiber optic gyroscope using a binary modulation depth method, and belongs to the technical field of fiber optic gyroscopes. The system includes a fiber optic gyroscope closed-loop system and a signal processing circuit. In the signal processing circuit, the photocurrent signal detected by the photodetector is amplified and converted into a digital signal. In the FPGA digital logic circuit, the signal is modulated using a binary modulation depth method, and the optical path power and angular velocity in the digital signal are demodulated using a digital operation method. The generated feedback signal is fed back to the current control port of the wide-spectrum light source and the phase modulator of the Y-waveguide integrated optical chip. The present invention uses a shared A / D detection channel for optical path power compensation and fiber optic gyroscope angular velocity detection, eliminating the need for an additional optical power detection module. Real-time compensation of the optical path power of the fiber optic gyroscope can be achieved without affecting the performance and size of the fiber optic gyroscope, thereby increasing the reliability and stability of the fiber optic gyroscope.

Description

Technical Field

[0001] The present invention relates to a binary modulation depth optical path power compensation system and method for an optical fiber gyroscope, belonging to the technical field of optical fiber gyroscopes. Background Art

[0002] The fiber optic gyroscope (FOG) is an angular velocity measurement instrument based on the Sagnac effect and a key component in the field of inertial navigation technology. The optical path power of an FOG refers to the effective optical power reaching the photodetector and is a key factor affecting the FOG's signal-to-noise ratio. Light from a light source passes through optical components such as couplers, Y-waveguides, and fiber rings before reaching the photodetector. These components exhibit varying optical power losses under complex environmental conditions, such as high and low temperatures. This causes fluctuations in the FOG's optical path power, thereby affecting the FOG's bias stability.

[0003] To enhance the reliability of fiber optic gyroscopes (FOGs) in complex environments, engineering generally employs automatic light source control to compensate for optical path power in real time. Currently, there are four commonly used methods for monitoring optical path power: First, an additional photodetector is fused to the coupler's dead end, and the optical path power is obtained through a forward amplifier circuit and A / D module; second, a detection branch is connected in parallel to the back end of the photodetector; third, the voltage across the SLD is monitored to obtain the device's output power; and fourth, the modulation and demodulation algorithm is modified, such as using four-way four-state modulation to obtain optical path power. Of these solutions, the first three require additional hardware, which is not conducive to the miniaturization of FOGs. The fourth solution changes the modulation and demodulation algorithm, affecting the FOG's response bandwidth and adversely affecting applications such as high-frequency vibration. Currently, there is no publicly available method for real-time monitoring and compensation of FOG optical path power without affecting the gyroscope's performance and size. Summary of the Invention

[0004] The purpose of the present invention is to solve the above-mentioned problems and provide a system and method for compensating the optical path power of a fiber optic gyroscope using binary modulation depth. The optical path power can be detected and compensated using a purely computational method, thereby sharing an A / D detection channel with the fiber optic gyroscope angular velocity detection. There is no need to add an additional optical power detection module, and the modulation and demodulation algorithm of the original gyroscope is not affected, and the performance of the fiber optic gyroscope is not affected.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] One of the objects of the present invention is to provide a binary modulation deep optical path power compensation system for a fiber optic gyroscope, comprising:

[0007] A fiber optic gyroscope closed-loop system, in which an optical signal emitted by a broadband light source enters a Y-waveguide integrated optical chip through a coupler, where it is converted into two clockwise and counterclockwise beams before being transmitted through a fiber optic ring. The optical signal returning from the fiber optic ring passes through the Y-waveguide integrated optical chip and the coupler in sequence, and a photocurrent signal is detected by a photodetector.

[0008] A signal processing circuit includes a forward amplifier circuit, an A / D module, an FPGA digital logic circuit, a first D / A module, a second D / A module, a first drive circuit, and a second drive circuit. The forward amplifier circuit, the A / D module, and the FPGA digital logic circuit are sequentially connected in series, and are used to amplify a photocurrent signal detected by a photodetector and convert it into a digital signal, and calculate and generate a first feedback signal containing angular velocity compensation information and a second feedback signal containing optical path power information. The first feedback signal is converted into an analog signal by the first D / A module and applied to a phase modulator of a Y-waveguide integrated optical chip through a first drive circuit. The second feedback signal is converted into an analog signal by a second D / A module and applied to a current control port of a wide-spectrum light source through a second drive circuit.

[0009] Furthermore, the Y-waveguide integrated optical chip includes a polarizer, a Y-beam splitter and a phase modulator. One end of the polarizer is connected to the coupler, and the other end is connected to the port on one side of the Y-beam splitter. The two ports on the other side of the Y-beam splitter are respectively connected to the two ends of the optical fiber ring to form two branches; the phase modulator is located on one or both branches.

[0010] Another object of the present invention is to provide a compensation method for the binary modulation deep optical path power compensation system based on the above-mentioned fiber optic gyroscope, comprising the following steps:

[0011] Step 1: Introduce the four-state square wave signal into the phase modulator of the Y-waveguide integrated optical chip;

[0012] Step 2: Set the modulation depth of the modulation signal to A photoelectric detector is used to obtain a real-time detection signal, which is amplified by a forward amplifier circuit to obtain an amplified analog signal. The amplified analog signal is then converted into a digital signal by an A / D module and sent to the FPGA digital logic circuit.

[0013] Step 3: Register and demodulate the A / D module output signal in the FPGA digital logic circuit to obtain the digital value P1 of the optical path power;

[0014] Step 4: In the next demodulation cycle, set the modulation depth of the modulated signal to Calculated Digital value P2 of the optical path power at the modulation depth;

[0015] Step 5: Calculate the current optical path power P0 according to the following formula:

[0016]

[0017] The current optical path power P0 is compared with the preset optical path power value P t Performing a subtraction to obtain a second feedback signal k2 containing optical path power information; outputting the second feedback signal k2 to the second D / A module to convert it into an analog signal, and sending it to the second driving circuit, thereby applying the analog second feedback signal k2 to the current control port of the wide-spectrum light source, thereby realizing an optical path power feedback compensation closed loop;

[0018] Step 6: Repeat steps 2-5 to update and demodulate the optical path power of the current fiber optic gyroscope in real time and feed it back to the optical path, thereby achieving real-time optical path power feedback compensation for the fiber optic gyroscope.

[0019] Furthermore, while achieving real-time optical path power feedback compensation for the fiber optic gyroscope, a step of real-time angular velocity feedback closed-loop control of the fiber optic gyroscope is also included between step 3 and step 4, specifically:

[0020] The digital value of angular acceleration is calculated in the FPGA digital logic circuit, and the digital value of angular acceleration is accumulated every 2 cycles to obtain the current angular velocity. The angular velocity is accumulated every τ cycles to obtain the current step wave. The current step wave is added to the current four-state square wave value to generate a first feedback signal k1 containing angular velocity compensation information. The first feedback signal k1 is output to the first D / A module, converted into an analog signal, and sent to the first drive circuit. The analog form of the first feedback signal k1 is then applied to the Y-waveguide integrated optical chip for modulation, thereby realizing an angular velocity closed loop.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] The present invention adds a D / A module and a drive circuit to the light source control section to achieve real-time detection and compensation of optical path power. This system shares a common A / D detection channel with conventional fiber optic gyroscope angular velocity detection, eliminating the need for an additional optical power detection module. This system requires minimal hardware modifications to the fiber optic gyroscope, eliminates the need for additional optical components, and introduces no additional noise. Furthermore, the binary modulation depth method does not affect the existing fiber optic gyroscope's angular velocity modulation and demodulation methods, thereby maintaining the performance of the fiber optic gyroscope. This system achieves real-time compensation of the fiber optic gyroscope's optical path power without affecting the performance and size of the fiber optic gyroscope, thereby increasing the reliability and stability of the fiber optic gyroscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a schematic diagram of the binary modulation deep optical path power compensation system proposed in the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further explained and illustrated below in conjunction with the accompanying drawings.

[0025] like Figure 1 As shown in the figure, the closed-loop fiber gyroscope structure includes a broadband light source, a 2×2 coupler, a Y-waveguide integrated optical chip, a fiber ring, a photodetector, and a signal processing circuit. The transmitting port of the broadband light source is connected to the first port on one side of the 2×2 coupler, the second port on one side of the 2×2 coupler is connected to the receiving end of the photodetector, the first port on the other side of the 2×2 coupler is connected to a port on one side of the Y-waveguide integrated optical chip, and the two ports on the other side of the Y-beam splitter are connected to the two ends of the fiber ring respectively. The output end of the photodetector is connected to the current control port of the broadband light source and the phase modulator of the Y-waveguide integrated optical chip through the signal processing circuit.

[0026] Light emitted by a broadband light source enters through the first port on one side of a 2×2 coupler, exits from the first port on the other side, and then enters a Y-waveguide integrated chip. The light is divided into two beams, forward and reverse, and transmitted through an optical fiber ring. The transmitted light returns to the Y-waveguide integrated optical chip, then returns to the coupler from the first port on the other side of the 2×2 coupler and exits from the second port on one side. The photocurrent is detected by a photodetector. The detection signal output by the photodetector is processed by a signal processing circuit to obtain a first feedback signal containing angular velocity compensation information and a second feedback signal containing optical path power information. The first feedback signal is sent to a phase modulator in the Y-waveguide integrated optical chip to realize an angular velocity feedback closed loop. The second feedback signal is sent to the current control port of the broadband light source to realize optical path power feedback compensation.

[0027] In a specific embodiment of the present invention, the Y-waveguide integrated optical chip includes a polarizer, a Y-beam splitter and a phase modulator. One end of the polarizer is connected to a coupler, and the other end is connected to a port on one side of the Y-beam splitter; the two ports on the other side of the Y-beam splitter are respectively connected to the two ends of the optical fiber ring to form two branches; the phase modulator is located on one or both branches.

[0028] The signal processing circuit includes a forward amplifier circuit, an A / D module, an FPGA digital logic circuit, a first D / A module, a second D / A module, a first drive circuit, and a second drive circuit; the forward amplifier circuit, the A / D module, and the FPGA digital logic circuit are connected in series in sequence, and the FPGA digital logic circuit respectively processes the optical path power feedback compensation task and the angular velocity feedback closed-loop task, generating a first feedback signal containing angular velocity compensation information and a second feedback signal containing optical path power information. The first feedback signal is converted into an analog signal by the first D / A module and applied to the phase modulator of the Y-waveguide integrated optical chip through the first drive circuit. The second feedback signal is converted into an analog signal by the second D / A module and applied to the current control port of the broadband light source through the second drive circuit.

[0029] Based on the above system, a binary modulation depth optical path power compensation method for a fiber optic gyroscope is implemented. This method shares an A / D channel with a conventional fiber optic gyroscope angular velocity demodulation, that is, a shared forward amplifier circuit, A / D module, etc. The photocurrent signal detected by the photodetector is amplified and converted into a digital signal and sent to the FPGA digital logic circuit. The optical path power feedback compensation calculation and the angular velocity feedback closed-loop calculation are simultaneously performed in the FPGA digital logic circuit, thereby solving and compensating the optical path power without adding additional optical devices.

[0030] A specific implementation process in this embodiment is as follows:

[0031] Step 1: Convert the four-state square wave signal The phase modulator of the Y-waveguide integrated optical chip is introduced, in which the four-state square wave signal The expression is:

[0032]

[0033] Among them, the four-state square wave signal is a periodic signal with a period of 2, is the modulation depth parameter, the range of modulation depth is t is time, =L*n / is the transit time of the fiber loop, L is the length of the fiber loop, n is the refractive index of the fiber loop, and c is the speed of light.

[0034] Step 2: Set the modulation depth parameters of the modulation signal A photoelectric detector is used to obtain real-time detection signals, which are amplified by a forward amplifier circuit to obtain an amplified analog signal. The amplified analog signal is then converted into a digital signal I(t) using an A / D module and sent to the FPGA digital logic circuit.

[0035] Step 3: Register and demodulate the A / D module output signal I(t) in the FPGA digital logic circuit to obtain the digital value P1 of the optical path power and the digital value a of the angular acceleration. d , where the storage and demodulation methods are as follows:

[0036] Use four registers I1, I2, I3, and I4 to store I(t) at 0<τ / 2, τ / 2≤t<τ, τ≤t<3τ / 2, and 3τ / 2≤t<2τ, respectively. The demodulation formula is P1=I1+I2+I3+I4, a d =I1+I4-I2-I3.

[0037] Step 4: The digital value a of the angular acceleration signal d It is necessary to accumulate once every 2 cycles to get the current angular velocity v d ; The current angular velocity v d It is necessary to accumulate once every τ period to get the current step wave Set the current step wave and the current four-state square wave value The angular velocity compensation information is added to generate a feedback signal k1; the feedback signal k1 is output to the first D / A module to be converted into an analog signal, and sent to the first driving circuit, so that the analog feedback signal k1 is applied to the Y-waveguide integrated optical chip for modulation, thereby realizing an angular velocity closed loop.

[0038] Step 5: Set the modulation depth parameters of the modulation signal According to the above method, we can calculate The digital value of optical path power P2 under modulation depth. According to the formula Obtain the current optical path power P0 and compare it with the preset optical path power value P t The difference is calculated to obtain the optical path power compensation feedback signal k2. The feedback signal k2 is output to the second D / A module, converted into an analog signal, and sent to the second drive circuit. The analog feedback signal k2 is then applied to the current control port of the wide-spectrum light source, thus completing the optical path power feedback compensation closed loop.

[0039] Step 6: Repeat steps 2-5 to update and demodulate the optical path power and angular velocity of the current fiber optic gyroscope in real time, and feed it back to the optical path, thereby realizing real-time angular velocity feedback closed loop and optical path power feedback compensation for the fiber optic gyroscope.

[0040] The optical path power compensation method proposed in this invention shares a common A / D detection channel with conventional fiber optic gyroscope angular velocity detection, eliminating the need for an additional optical power detection module. This optical path power compensation system requires no major hardware modifications to the fiber optic gyroscope, no additional optical components, and no additional noise. Furthermore, the method for changing the modulation depth does not affect the existing fiber optic gyroscope's angular velocity modulation and demodulation methods, thereby maintaining the performance of the fiber optic gyroscope. This invention simultaneously achieves real-time optical path power compensation and angular velocity closed-loop control for the fiber optic gyroscope at a low cost, thereby increasing the reliability and stability of the fiber optic gyroscope.

[0041] The above examples are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and many variations are possible. All variations that can be directly derived or imagined by a person skilled in the art from the contents disclosed in the present invention should be considered as within the scope of protection of the present invention.

Claims

1. A binary modulation deep optical path power compensation system for a fiber optic gyroscope, characterized in that: include: A fiber optic gyroscope closed-loop system, in which an optical signal emitted by a broadband light source enters a Y-waveguide integrated optical chip through a coupler, where it is converted into two clockwise and counterclockwise beams before being transmitted through a fiber optic ring. The optical signal returning from the fiber optic ring passes through the Y-waveguide integrated optical chip and the coupler in sequence, and a photocurrent signal is detected by a photodetector. A signal processing circuit includes a forward amplifier circuit, an A / D module, an FPGA digital logic circuit, a first D / A module, a second D / A module, a first drive circuit, and a second drive circuit. The forward amplifier circuit, the A / D module, and the FPGA digital logic circuit are sequentially connected in series and are used to amplify the photocurrent signal detected by the photodetector and convert it into a digital signal, and to calculate and generate a first feedback signal containing angular velocity compensation information and a second feedback signal containing optical path power information. The first feedback signal is converted into an analog signal by the first D / A module and applied to the phase modulator of the Y-waveguide integrated optical chip through the first drive circuit. The second feedback signal is converted into an analog signal by the second D / A module and applied to the current control port of the broadband light source through the second drive circuit. The generation process of the first feedback signal and the second feedback signal includes: The four-state square wave signal is introduced into the phase modulator of the Y-waveguide integrated optical chip; Set the modulation depth of the modulation signal to A photoelectric detector is used to obtain a real-time detection signal, which is amplified by a forward amplifier circuit to obtain an amplified analog signal. The amplified analog signal is then converted into a digital signal by an A / D module and sent to the FPGA digital logic circuit. The output signal of the A / D module is stored and demodulated in the FPGA digital logic circuit to obtain the digital value P1 of the optical path power; the digital value of the angular acceleration is calculated in the FPGA digital logic circuit, and the digital value of the angular acceleration is accumulated every 2τ period to obtain the current angular velocity; the angular velocity is accumulated every τ period to obtain the current step wave; the current step wave is added to the current four-state square wave value to generate a first feedback signal k1 containing angular velocity compensation information; In the next demodulation cycle, set the modulation depth of the modulated signal to Calculated Digital value P2 of the optical path power at the modulation depth; Calculate the current optical path power P0 according to the following formula: The current optical path power P0 is compared with the preset optical path power value P t The difference is performed to obtain a second feedback signal k2 containing optical path power information.

2. The binary modulation depth optical path power compensation system of the fiber optic gyroscope according to claim 1, characterized in that: The Y-waveguide integrated optical chip includes a polarizer, a Y-beam splitter and a phase modulator. One end of the polarizer is connected to a coupler, and the other end is connected to a port on one side of the Y-beam splitter. The two ports on the other side of the Y-beam splitter are respectively connected to the two ends of the optical fiber ring to form two branches; the phase modulator is located on one or both branches.

3. A compensation method for the binary modulation deep optical path power compensation system of the fiber optic gyroscope according to claim 1, characterized in that: The following steps are involved: Step 1: Introduce the four-state square wave signal into the phase modulator of the Y-waveguide integrated optical chip; Step 2: Set the modulation depth of the modulation signal to A photoelectric detector is used to obtain a real-time detection signal, which is amplified by a forward amplifier circuit to obtain an amplified analog signal. The amplified analog signal is then converted into a digital signal by an A / D module and sent to the FPGA digital logic circuit. Step 3: Register and demodulate the A / D module output signal in the FPGA digital logic circuit to obtain the digital value P1 of the optical path power; Step 4: In the next demodulation cycle, set the modulation depth of the modulated signal to Calculated Digital value P2 of the optical path power at the modulation depth; Step 5: Calculate the current optical path power P0 according to the following formula: The current optical path power P0 is compared with the preset optical path power value P t Performing a subtraction to obtain a second feedback signal k2 containing optical path power information; outputting the second feedback signal k2 to the second D / A module to convert it into an analog signal, and sending it to the second driving circuit, thereby applying the analog second feedback signal k2 to the current control port of the wide-spectrum light source, thereby realizing an optical path power feedback compensation closed loop; Step 6: Repeat steps 2-5 to update and demodulate the optical path power of the current fiber optic gyroscope in real time and feed it back to the optical path, thereby achieving real-time optical path power feedback compensation for the fiber optic gyroscope.

4. The compensation method according to claim 3, characterized in that: The four-state square wave signal described in step 1 is expressed as: in, is a four-state square wave signal, is the modulation depth parameter of the modulation signal, t is the time, and τ is the transit time of the fiber ring.

5. The compensation method according to claim 3, characterized in that: The step 3 includes: Four registers are used to store the digital signals sent to the FPGA digital logic circuit in the range of 0≤t<τ / 2, τ / 2≤t<τ, τ≤t<3τ / 2, and 3τ / 2≤t<2τ. Calculate the digital value P1 of the optical path power according to the following formula: P1=I1+I2+I3+I4 Among them, I1, I2, I3, and I4 are the storage results of four registers respectively.

6. The compensation method according to claim 5, characterized in that: While achieving real-time optical path power feedback compensation for the fiber optic gyroscope, a step of real-time angular velocity feedback closed-loop control of the fiber optic gyroscope is also included between step 3 and step 4, specifically: The digital value of angular acceleration is calculated in the FPGA digital logic circuit, and the digital value of angular acceleration is accumulated every 2τ cycles to obtain the current angular velocity. The angular velocity is accumulated every τ cycle to obtain the current step wave. The current step wave is added to the current four-state square wave value to generate a first feedback signal k1 containing angular velocity compensation information. The first feedback signal k1 is output to the first D / A module, converted into an analog signal, and sent to the first drive circuit, so that the analog form of the first feedback signal k1 is applied to the Y-waveguide integrated optical chip for modulation, thereby realizing an angular velocity closed loop.

7. The compensation method according to claim 6, characterized in that: The calculation formula of the digital value of angular acceleration is as follows: a d =I1+I4-I2-I3 Among them, a d is the digital value of angular acceleration.

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