Resonant fiber optic gyroscope based on broadband light source

Abstract

A resonant fiber optic gyroscope based on a broadband light source includes: a broadband light source, an optical circulator, a photodetector, a fiber optic ring resonant cavity, a modulator, and a signal processing unit arranged sequentially. Light emitted from the broadband light source enters the fiber optic ring resonant cavity after passing through the optical cyclotron. After exiting from the output port of the ring resonant cavity, it is modulated by the modulator and returns along the same path. It then enters the optical resonant cavity in the opposite direction from the output port and enters the photodetector via the optical circulator. The data processing unit generates a drive signal and outputs it to the modulator. It receives the electrical signal output from the photodetector and performs demodulation operations to obtain the rotation speed and direction of the fiber optic ring resonant cavity. In closed-loop operation, this device uses the signal processing unit for feedback control to adjust the frequency shift of the returning light, achieving high-precision angular velocity measurement while significantly reducing system cost and complexity.

Description

Technical Field

[0001] This invention relates to a technology in the field of fiber optic gyroscopes, specifically to a resonant fiber optic gyroscope that uses broadband white light as a light source. Background Technology

[0002] Existing resonant fiber optic gyroscopes use narrow-linewidth laser sources to detect the resonant frequency difference between two opposing directions within the resonant cavity. However, various noises introduced by the laser pose numerous challenges to the demodulation of these gyroscopes. These noises include polarization crosstalk, backscattering and reflection in the fiber optic ring resonator, the Kerr effect caused by power imbalance in the two directions within the fiber optic ring resonator, and frequency and intensity noise from the light source. Furthermore, frequency locking technology is required to align the laser frequency to the resonant frequency of the fiber optic resonant cavity in real time, and the frequency locking loop increases the system's cost and complexity. Summary of the Invention

[0003] This invention addresses the problems of high coherence noise, complex optical path systems and control algorithms, and low measurement accuracy caused by the use of high-coherence laser sources and multiple locked feedback loops in existing resonant gyroscopes, as well as the adverse effects of backscattered signals and nonlinear Kerr effects caused by high-coherence sources. It proposes a broadband white light-based resonant fiber optic gyroscope, which adjusts the frequency shift of the returned light through feedback control via a signal processing unit in closed-loop operation. This significantly reduces system cost and complexity while achieving high-precision angular velocity measurement.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a resonant fiber optic gyroscope based on a broadband light source, comprising: a broadband light source, an optical circulator, a photodetector, a fiber optic ring resonant cavity, a modulator, and a signal processing unit arranged sequentially. The light emitted from the broadband light source enters the fiber optic ring resonant cavity after passing through the optical circulator, exits from the output port of the fiber optic ring resonant cavity, is modulated by the modulator, and returns along the same path. It then enters the optical resonant cavity in the opposite direction from the output port and enters the photodetector via the optical circulator. The signal processing unit generates a drive signal and outputs it to the modulator. It receives the electrical signal output from the photodetector and performs demodulation operations to obtain the rotation speed and direction of the fiber optic ring resonant cavity.

[0006] The fiber optic ring resonator includes two optical couplers and a fiber optic ring, wherein: the two fiber optic ports of the fiber optic ring are respectively connected to the fourth port of the second optical coupler and the fourth port of the first optical coupler; the second port of the second optical coupler is connected to the second port of the first optical coupler, thereby forming a fiber optic ring resonator; the first port of the second optical coupler is connected to the modulator, and the third port is left unused and subjected to anti-reflection treatment; the first port of the first optical coupler is connected to the optical circulator, and the third port is left unused and subjected to anti-reflection treatment.

[0007] The broadband light source is preferably an erbium-doped superfluorescent fiber optic light source.

[0008] The modulator is a combination of a reflective device or a transmissive modulator and a reflector.

[0009] The modulation mentioned above employs either frequency modulation or phase modulation.

[0010] The signal processing unit is used to generate drive signals, reference signals required for synchronous demodulation, and demodulate electrical signals; the signal processing unit is implemented using, but is not limited to, a field-programmable gate array (FPGA).

[0011] The opposite direction refers to the following: the optical signal emitted by the broadband light source is output to the first port of the optical circulator and then output through the second port. It is then input into the fiber optic ring resonator via the first optical coupler, output from the second optical coupler to the modulator for modulation, and then input into the fiber optic ring resonator in the opposite direction along the same optical path. Finally, it is output from the third port of the optical circulator to the photodetector.

[0012] When the fiber resonator moves at an angular velocity During rotation, due to the Sganca effect, the resonant frequencies propagating in the two opposite directions of the resonant cavity are no longer the same, but instead generate frequencies proportional to the rotational angular velocity. frequency difference Therefore, when light passes through the resonant cavity from two opposite directions, i.e. ,in Let be the transmission spectrum function of the fiber optic ring resonator in the clockwise direction (CW). This represents the transmission spectrum function in the counter-clockwise (CCW) direction. It describes the loss experienced by broadband light as it passes through the fiber optic resonator twice in opposite directions, varying with... The light power detected by the photodetector increases accordingly with the increase of the value of the photodetector. The decrease is due to the increase in optical power; the degree of decrease in optical power can be used to determine... The size, but cannot be determined The positive and negative signs.

[0013] The rotation speed and direction of the fiber optic ring resonator are obtained through open-loop or closed-loop methods, specifically as follows:

[0014] ① In open-loop mode, the signal processing unit generates a frequency of The periodic drive signal drives the modulator, causing the instantaneous frequency of the optical signal passing through the modulator to generate a frequency of... Periodic disturbances At this time, the signal processing unit uses the driving signal as a reference signal to synchronously detect the electrical signal output by the photodetector, and extracts the frequency of the electrical signal output by the photodetector. component signal P out According to component signal P out Demodulation yields the rotational angular velocity of the fiber optic ring resonator. The size and direction, i.e. , where k is the calibration coefficient.

[0015] The calibration coefficient k is preferably applied to the fiber optic gyroscope to be calibrated using an angular velocity already measured by a precision turntable. And according to the corresponding component signal P out Calculated.

[0016] ② In closed-loop mode (without any changes to the connection method), the signal processing unit generates a drive signal and outputs it to the modulator, generating a frequency of [frequency value missing] for the instantaneous frequency of the optical signal. Periodic disturbances At the same time, an adjustable frequency shift is generated. At this time, the signal processing unit uses a frequency of Using a periodic drive signal as a reference signal, the electrical signal is synchronously detected, and adjustments are made in real time. The magnitude and sign of the components make the frequency of the electrical signal... component signal P out Always 0, that is, using component signal P out Used for error feedback, through control The magnitude and sign of the gyroscope keep the feedback error at zero, at which point the gyroscope operates in a closed-loop state. Just enough to compensate Thus, the rotational angular velocity of the gyroscope can be obtained. Where: D is the radius of the fiber loop, and n is the refractive index of the fiber. λ is the center wavelength of the light source.

[0017] Technical effect

[0018] This invention addresses the shortcomings of existing broadband light source-based resonant fiber optic gyroscopes, which require a Y-waveguide modulator to simultaneously perform light splitting, combining, and modulation, necessitating high device integration. This invention employs a low-coherence light source and a fiber optic ring resonant cavity to implement a resonant fiber optic gyroscope. The modulator does not need to participate in light splitting or combining, avoiding the coherent noise caused by laser light sources in traditional resonant fiber optic gyroscopes, thus improving measurement accuracy. In experiments, a 100-meter-long fiber optic ring achieved near-navigation-grade measurement accuracy. Feedback control via a signal processing unit in closed-loop operation reduces system complexity and the number of modulators, lowering both cost and system non-reciprocity. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention;

[0020] In the diagram: 1. Broadband white light source, 2. Optical circulator, 3. Photodetector, 4. First optical coupler, 5. Fiber optic ring, 6. Second optical coupler, 7. Modulator, 8. Signal processing unit;

[0021] Figure 2 This is a schematic diagram illustrating the working principle of the embodiment;

[0022] In the figure: (a) is the transmission spectrum of the fiber optic ring resonator in the clockwise direction; (b) is the transmission spectrum of the fiber optic resonator in the counterclockwise direction, showing a frequency shift due to rotation compared to the clockwise spectrum. (c) shows the intensity of transmitted light after broadband white light passes through the fiber optic ring resonator twice, in counterclockwise and clockwise directions, with increasing intensity. The curve of change;

[0023] Figure 3 The time-domain measurement results are shown in the example when the object is stationary.

[0024] In the figure: (a) is the original data, and (b) is the result after a 10-second moving average;

[0025] Figure 4 The Allan standard deviation is the measurement taken at rest for the example.

[0026] Figure 5 The actual time-domain measurement results when angular velocity is applied in the example;

[0027] Figure 6 This is a schematic diagram of the closed-loop working state of an embodiment. Detailed Implementation

[0028] like Figure 1As shown in the figure, this embodiment relates to a resonant fiber optic gyroscope based on a low-coherence broadband light source, comprising: a broadband white light source 1, an optical circulator 2, a photodetector 3, a first optical coupler 4, an optical fiber ring 5, a second optical coupler 6, a modulator 7, and a signal processing unit 8; wherein: the modulator 7, the signal processing unit 8, and the photodetector 3 are connected in sequence; the optical fiber ring 5, the first optical coupler 4, and the second optical coupler 6 are fused together to form an optical fiber ring resonant cavity; the optical circulator 2 is connected to the broadband light source 1 and the first optical coupler 4 respectively; the modulator 7 is connected to the second optical coupler 6; the optical signal emitted by the broadband white light source 1 is output to the optical fiber ring resonant cavity through the optical circulator 2, forming an optical signal that propagates in a counterclockwise direction and is output to the modulator 7; the modulated light returns along the original path to the optical fiber ring resonant cavity, forming an optical signal that propagates in a clockwise direction and is output to the photodetector 3 through the optical circulator 2; the signal processing unit 8 generates a sinusoidal modulation signal to drive the modulator 7, acquires the output electrical signal of the photodetector 3, and performs synchronous demodulation.

[0029] The broadband white light source 1 is preferably an erbium-doped superfluorescent fiber light source with a center wavelength of 1550nm, a spectral bandwidth of 35nm, and an output optical power of 100mW.

[0030] All of the aforementioned circulators are polarization-maintaining circulators.

[0031] In the aforementioned fiber optic ring resonator: the fiber optic ring 5 is formed by winding a section of optical fiber into a ring shape, and its two fiber optic ports are respectively connected to the fourth port 6.4 of the second optical coupler 6 and the fourth port 4.4 of the first optical coupler 4. The second port 6.2 of the second optical coupler 6 is connected to the second port 4.2 of the first optical coupler 4, thereby forming a fiber optic ring resonator; the first port 6.1 of the second optical coupler 6 is connected to the modulator 7, and the third port 6.3 is left unused and subjected to anti-reflection treatment; the first port 4.1 of the first optical coupler 4 is connected to the optical circulator 2, and the third port 4.3 is left unused and subjected to anti-reflection treatment.

[0032] The fiber optic loop has an optical fiber length of 100 meters and a coil diameter of 14.5 cm.

[0033] The second fiber coupler 6 and the first fiber coupler 4 have the same parameters and are both polarization-maintaining couplers with a 95:5 ratio, meaning that the coupling efficiency from the first port 4.1 to the third port 4.3 of the first fiber coupler 4 or from the first port 6.1 to the third port 6.3 of the second fiber coupler 6 is 95%.

[0034] The driving signal is a sine wave with a frequency of 21.985 kHz.

[0035] The free spectral range of the fiber ring resonator is 2.01 MHz, the fineness is approximately 30, and the scaling factor is approximately 64.5 kHz / (rad / s).

[0036] The aforementioned resonant fiber optic gyroscope specifically detects the magnitude and direction of rotation of the fiber optic ring resonant cavity in the following manner:

[0037] Step 1) Calibrate and obtain the rotational angular rate The signal processing unit outputs component signal P out The proportionality coefficient is specifically calculated as follows: by applying a fixed rotation to the resonant fiber optic gyroscope using a high-precision turntable, the proportionality coefficient is 1° / h / mV.

[0038] Step 2) Perform performance testing on the resonant fiber optic gyroscope: Place the resonant fiber optic gyroscope in a stationary state and record its output for 10,000 seconds at a sampling rate of 10Sa / s. The resulting raw time-domain data is as follows: Figure 3 As shown in (a). Then a sliding average is performed with a 10-second time window, as follows: Figure 3 As shown in (b), the zero-bias instability of this resonant fiber optic gyroscope over a 10-second average time is 0.15° / h. Figure 3 Calculate the Allen standard deviation of the data in the dataset, such as Figure 4 As shown, the random walk angle of this resonant fiber optic gyroscope can be read as 0.008° / .

[0039] Step 3) Conduct experimental testing on the resonant fiber optic gyroscope: Place the fiber optic gyroscope on a high-precision turntable and apply a periodic sinusoidal rotation with an amplitude of 3600° / h and a frequency of 1Hz. Following the measurement method described above, the experimental data obtained are as follows: Figure 5 As shown, the performance of this gyroscope is verified.

[0040] In the closed-loop experimental design, the gyroscope structure remains unchanged. The modulated signal generated by the signal processing unit consists of two parts: one part is a frequency of... The waveform consists of a 21.985kHz sine wave and a sawtooth voltage waveform signal. The change in optical frequency generated by the modulator under the action of the sawtooth voltage is... ,in: The half-wave voltage of the modulator. This represents the rate of change of the sawtooth wave voltage. The signal processing unit uses a frequency of... The periodic drive signal is used as a reference signal to synchronously detect the electrical signal output by the photodetector and adjust it in real time. The magnitude and sign of the components make the frequency of the electrical signal... component signal P outThe value remains 0, indicating the system is operating in a closed-loop state. This fiber optic gyroscope is placed on a high-precision turntable and subjected to a periodic sinusoidal rotation with an amplitude of 36° / h and a frequency of 1Hz. Following the measurement method described above, the experimental data obtained are as follows: Figure 6 As shown, the performance of this gyroscope is verified.

[0041] Compared with existing technologies, the resonant fiber optic gyroscope based on a broadband light source in this embodiment achieves an accuracy of 0.008° / Furthermore, its system complexity and cost are significantly reduced, making it highly practical.

[0042] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A resonant fiber optic gyroscope based on a broadband light source, characterized in that, include: The system comprises a broadband light source, an optical circulator, a photodetector, a fiber optic ring resonator, a modulator, and a signal processing unit arranged sequentially. The light emitted from the broadband light source enters the fiber optic ring resonator after passing through the optical circulator. After exiting from the output port of the fiber optic ring resonator, it is modulated by the modulator and returns along the same path. It then enters the optical resonator in the opposite direction from the output port and enters the photodetector via the optical circulator. The signal processing unit generates a drive signal and outputs it to the modulator. It receives the electrical signal output from the photodetector and performs demodulation operations to obtain the rotation speed and direction of the fiber optic ring resonator. The rotation speed and direction of the fiber optic ring resonator are obtained through open-loop or closed-loop methods, specifically as follows: ① In open-loop mode, the signal processing unit generates a frequency of The periodic drive signal drives the modulator, causing the instantaneous frequency of the optical signal passing through the modulator to generate a frequency of... Periodic disturbances At this time, the signal processing unit uses the driving signal as a reference signal to synchronously detect the electrical signal output by the photodetector, and extracts the frequency of the electrical signal output by the photodetector. component signal P out According to component signal P out Demodulation yields the rotational angular velocity of the fiber optic ring resonator. The size and direction, i.e. Where: k is the calibration coefficient; ② In closed-loop mode, the signal processing unit generates a drive signal and outputs it to the modulator, generating a frequency of [frequency value missing] for the instantaneous frequency of the optical signal. Periodic disturbances At the same time, an adjustable frequency shift is generated. At this time, the signal processing unit uses a frequency of Using a periodic drive signal as a reference signal, the electrical signal is synchronously detected, and adjustments are made in real time. The magnitude and sign of the components make the frequency of the electrical signal... component signal P out Always 0, that is, using component signal P out Used for error feedback, through control The magnitude and sign of the gyroscope keep the feedback error at zero, at which point the gyroscope operates in a closed-loop state. Just enough to compensate Thus, the rotational angular velocity of the gyroscope can be obtained. Where: D is the radius of the fiber loop, and n is the refractive index of the fiber. λ is the center wavelength of the light source.

2. The resonant fiber optic gyroscope based on a broadband light source according to claim 1, characterized in that, The fiber optic ring resonator includes two optical couplers and a fiber optic ring, wherein: the two fiber optic ports of the fiber optic ring are respectively connected to the fourth port of the second optical coupler and the fourth port of the first optical coupler; the second port of the second optical coupler is connected to the second port of the first optical coupler, thereby forming a fiber optic ring resonator; the first port of the second optical coupler is connected to the modulator, and the third port is left unused and subjected to anti-reflection treatment; the first port of the first optical coupler is connected to the optical circulator, and the third port is left unused and subjected to anti-reflection treatment.

3. The resonant fiber optic gyroscope based on a broadband light source according to claim 1, characterized in that, The modulator is a combination of a reflective device or a transmissive modulator and a reflector; the modulation is frequency modulation or phase modulation.

4. The resonant fiber optic gyroscope based on a broadband light source according to claim 1, characterized in that, The opposite direction refers to the following: the optical signal emitted by the broadband light source is output to the first port of the optical circulator and then output through the second port. It is then input into the fiber optic ring resonator via the first optical coupler, output from the second optical coupler to the modulator for modulation, and then input into the fiber optic ring resonator in the opposite direction along the same optical path. Finally, it is output from the third port of the optical circulator to the photodetector.

5. The resonant fiber optic gyroscope based on a broadband light source according to claim 1, characterized in that, The calibration coefficient k is obtained by applying an angular velocity, measured by a precision turntable, to the fiber optic gyroscope to be calibrated. And according to the corresponding component signal P out Calculated.

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