High-precision fiber optic gyroscope with stable scale factor

Abstract

This invention relates to the field of fiber optic gyroscope technology and discloses a high-precision fiber optic gyroscope with a stable calibration factor to achieve the purpose of stabilizing the gyroscope's calibration factor. The gyroscope includes a broadband light source generator, a three-terminal fiber optic circulator with a filter inserted at its second port, a multifunctional optical chip, a fiber optic sensing ring, a photodetector, and a signal processing unit. The broadband light source generator outputs an optical signal to the first port of the three-terminal fiber optic circulator. The second port of the three-terminal fiber optic circulator is coupled to the input port of the multifunctional optical chip. The multifunctional optical chip integrates a polarizer, a Y-type beam splitter, and a phase modulator. The two output ports of the Y-type beam splitter are coupled to the two input ports of the fiber optic sensing ring. The third port of the three-terminal fiber optic circulator is coupled to the input port of the photodetector. The output port of the photodetector is electrically connected to the phase modulator of the multifunctional optical chip through the signal processing unit. The signal processing unit outputs an angular velocity signal. This gyroscope has a stable calibration factor.

Description

Technical Field

[0001] The invention relates to the technical field of fiber optic gyroscopes, and in particular discloses a high-precision fiber optic gyroscope with a stable scale factor. Background Art

[0002] Traditional high-precision fiber optic gyroscope structures such as Figure 3 He Ru Figure 4 shown. Figure 3 It is a backward pumping method. Figure 3 The light emitted by the pump laser 10 excites the active optical fiber 30 to emit amplified spontaneous emission ASE light through the wavelength division multiplexing coupler 20 (the tail end of the active optical fiber 30 may contain a Faraday reflector or an ordinary reflector); Figure 4 It is forward pumping mode. Figure 4 The light emitted by the pump laser 10 excites the active optical fiber 30 to emit amplified spontaneous emission ASE light through the wavelength division multiplexing WDM coupler 20 (one end of the wavelength division multiplexing coupler 20 contains a Faraday reflector or a common reflector 20-1); Figure 3 or Figure 4 The ASE light emitted by the active optical fiber 30 passes through the isolator 90 and the filter 100, and is split into two by the coupler 110, one of which enters the input end of the multifunctional lithium niobate integrated optical chip 50. The chip 50 is integrated with a polarizer, a Y-type beam splitter and a phase modulator. The Y-type beam splitter in the chip 50 splits the light beam into two and outputs them. The upper light beam passes through the optical fiber sensor ring 60 in a clockwise direction and then returns to the chip 50; the lower light beam passes through the optical fiber sensor ring 60 in a counterclockwise direction and then returns to the chip 50; the two clockwise and counterclockwise lights are synthesized by the Y-type beam splitter in the chip 50 to form interference, and then pass through the input end of the chip 50 to the coupler 110 to split the light into two, one of which is converted into an electrical signal by the photodetector 70, and is fed back to the phase modulator in the chip 80 through the signal processing unit 80, and the angular velocity signal of the gyroscope relative to the inertial reference system is output at the same time.

[0003] Because the scale factor of the fiber optic gyroscope is closely related to the average wavelength of the optical signal receiving end, the gyroscope needs to obtain a stable scale factor under a wide range of temperature conditions, so the filter 100 plays a role in stabilizing the average wavelength of the light source. However, it is noted that what the fiber optic gyroscope needs to obtain a stable scale factor is the average wavelength of the light at the optical signal receiving end, rather than the average wavelength of the light from the light source output end. Therefore, this traditional method of stabilizing the average wavelength of the optical signal at the receiving end by stabilizing the wavelength of the light source with the filter 100 has major defects; and the ASE light loses 3 / 4 of the light energy when passing through the coupler 110 for the second time. In order to overcome the above problems, the present invention intends to provide a high-precision fiber optic gyroscope that can accurately control the average wavelength of the light at the optical signal receiving end, thereby achieving the purpose of stabilizing the gyroscope scale factor, and greatly reducing the light energy loss to effectively improve the signal-to-noise ratio of the gyroscope. Summary of the invention

[0004] The purpose of the present invention is to solve the problem in the prior art that the average wavelength of light at the receiving end of a high-precision fiber optic gyroscope is unstable within a wide operating temperature range, thereby causing an unstable scale factor, and to provide a high-precision fiber optic gyroscope that can stabilize the average wavelength of light at the receiving end, i.e., the scale factor, and effectively improve the gyroscope signal-to-noise ratio.

[0005] The specific technical scheme adopted by the present invention is as follows: a high-precision fiber optic gyroscope with a stable scale factor, comprising a wide-spectrum light source generator, a three-terminal fiber optic circulator with a filter inserted in the second port, a multifunctional optical chip, a fiber optic sensing ring, a photodetector and a signal processing unit; the wide-spectrum light source generator outputs an optical signal to the first port of the three-terminal fiber optic circulator, the second port of the three-terminal fiber optic circulator is coupled with the input end of the multifunctional optical chip, a polarizer, a Y-type beam splitter and a phase modulator are integrated on the multifunctional optical chip, two output ports of the Y-type beam splitter are coupled with two input ports of the fiber optic sensing ring, the third port of the three-terminal fiber optic circulator is coupled with the input end of the photodetector, the output end of the photodetector is electrically connected to the phase modulator of the multifunctional optical chip through the signal processing unit, and the signal processing unit outputs an angular velocity signal.

[0006] Through the above technical solution, the light emitted by the pump laser is self-amplified and radiated ASE light by the wide-spectrum light source generator, and is input to the first port of a special three-terminal fiber circulator with a filter. The ASE light passes through the birefringence and Faraday element inside the three-terminal fiber circulator, and then passes through the internal filter and is output from the second port of the three-terminal fiber circulator. The light enters the input end of the multifunctional lithium niobate integrated optical chip. The chip is sequentially integrated with a polarizer, a Y-type beam splitter and a phase modulator from the input end to the output end. The Y-type beam splitter in the chip splits the light beam into two and then outputs it, wherein the upper light beam is output in a clockwise direction. After passing through the fiber optic sensor ring, it returns to the chip; the lower light beam passes through the fiber optic sensor ring in a counterclockwise direction and returns to the chip; the two clockwise and counterclockwise light beams are synthesized by the Y-shaped beam splitter in the chip to form interference, and return to the second port of the special circulator through the chip input end. When entering the second port of the special circulator, the light first passes through the internal filter, and then passes through the internal Faraday element and birefringence element, and is output from the third port of the circulator, converted into an electrical signal by the photodetector, and fed back to the phase modulator in the chip through the signal processing unit, and the angular velocity signal of the gyroscope relative to the inertial reference system is output at the same time. Because the scale factor of the fiber optic gyroscope is closely related to the average wavelength of the light source, the gyroscope needs to obtain a stable scale factor under a wide range of temperature conditions. Therefore, when the ASE light passes through the special circulator for the first time, the internal filter near the second port of the circulator plays a role in stabilizing the average wavelength of the output light source. When the ASE light returns from the chip and passes through the circulator for the second time, the internal filter near the second port plays a role in reducing the change of the average wavelength caused by the wavelength filtering characteristics of the chip and the fiber ring with the temperature change, that is, it plays a role in stabilizing the average wavelength of the output light source again. The ASE spectrum is shaped into a Gaussian spectrum by the circulator with integrated filters for the second time, which effectively improves the zero-bias stability of the gyroscope. In addition, because there is no need to lose 3 / 4 of the energy by passing through the coupler for the second time, the use of a three-terminal fiber circulator can theoretically increase the optical receiving power by four times. Therefore, a high-precision fiber optic gyroscope that accurately controls the average wavelength of the light at the receiving end of the optical signal can be provided, thereby achieving the purpose of stabilizing the gyroscope scale factor and improving the signal-to-noise ratio.

[0007] Furthermore, the broadband light source generator includes a pump laser, a wavelength division multiplexing coupler and an active optical fiber coupled in sequence, and the optical signal is output from the wavelength division multiplexing coupler to the first port of the three-terminal optical fiber circulator.

[0008] Furthermore, a Faraday reflector or a common reflector is arranged at the tail end of the active optical fiber, which reflects the light at the starting point to improve the output efficiency of the ASE light.

[0009] Furthermore, the broadband light source generator includes a pump laser, a wavelength division multiplexing coupler and an active optical fiber coupled in sequence, and the optical signal is output from the active optical fiber to the first port of the three-terminal optical fiber circulator.

[0010] Furthermore, a Faraday reflector or a common reflector is arranged at the free end of the wavelength division multiplexing coupler, which reflects the light at the starting point to improve the output efficiency of the ASE light.

[0011] Furthermore, the second port of the three-terminal optical fiber circulator is coupled to the input end of the multifunctional optical chip through a polarization-maintaining optical fiber. The use of polarization-maintaining optical fiber reduces the influence of polarization-dependent loss of various components of the gyroscope.

[0012] Furthermore, the three-terminal optical fiber circulator with a filter inserted at the second port is replaced by an independent circulator plus an independent filter, and the independent filter is connected between the second port of the independent circulator and the multifunctional optical chip.

[0013] Furthermore, the three-terminal fiber circulator with a filter inserted in the second port is replaced by an isolator, a coupler and a filter. The isolator is connected between the broadband light source generator and the coupler, the filter is connected between the first output port of the coupler and the multifunctional chip, and the second output port of the coupler is coupled to the input end of the photodetector.

[0014] The beneficial effects of the present invention are as follows: since the light beam passes through the three-terminal fiber circulator integrated with a filter twice, the change of the spectrum distribution of the optical signal receiving end with the temperature is effectively reduced, the scale factor of the gyroscope is stabilized, and the spectrum is shaped into a Gaussian spectrum, providing the zero-bias stability of the gyroscope, while increasing the light receiving power and improving the gyroscope signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 1 is a schematic structural diagram of a high-precision fiber optic gyroscope with a stable scale factor according to the first embodiment;

[0016] Figure 2 is a schematic structural diagram of a high-precision fiber optic gyroscope with a stable scale factor according to Embodiment 2;

[0017] Figure 3 and Figure 4 There are two traditional high-precision fiber optic gyroscopes.

[0018] In the figure, 1, pump laser; 2, wavelength division multiplexing coupler; 3, active optical fiber; 4, three-terminal optical fiber circulator; 4-1, first port; 4-2, second port; 4-3, third port; 4-4, filter; 5, multifunctional optical chip; 6, optical fiber sensor ring; 7, photodetector; 8, signal processing unit; 10, pump laser; 20, wavelength division multiplexing coupler; 20-1, reflector; 30, active optical fiber; 50, chip; 60, optical fiber sensor ring; 70, photodetector; 80, signal processing unit; 90, isolator; 100, filter; 110, coupler. DETAILED DESCRIPTION

[0019] Embodiment 1

[0020] like Figure 1 As shown, a high-precision fiber optic gyroscope with a stable scale factor includes a wide-spectrum light source generator, a three-terminal fiber circulator 4 with a filter 4-4 inserted into the second port 4-2, a multifunctional optical chip 5, a fiber optic sensor ring 6, a photodetector 7, and a signal processing unit 8. The three-terminal fiber optic circulator has a first port 4-1, a second port 4-2, and a third port 4-3, and the second port 4-2 is inserted with a filter 4-4 (located on the side of the second port 4-2). The wide spectrum light source generator outputs an optical signal to the first port 4-1 of the three-terminal optical fiber circulator 4, the second port 4-2 of the three-terminal optical fiber circulator 4 is coupled to the input end of the multifunctional optical chip 5, the multifunctional optical chip 5 integrates a polarizer, a Y-type beam splitter and a phase modulator, the two output ports of the Y-type beam splitter are coupled to the two input ports of the optical fiber sensor ring 6, the third port 4-3 of the three-terminal optical fiber circulator is coupled to the input end of the photodetector 7; the output end of the photodetector 7 is input to the signal processing unit 8, the modulation of the signal processing unit 8 and the superposition of the feedback signal are electrically connected to the phase modulator of the multifunctional optical chip 5, and the signal processing unit 8 outputs an angular velocity signal. The second port 4-2 of the three-terminal optical fiber circulator 4 is coupled to the input end of the multifunctional optical chip 5 using a polarization-maintaining optical fiber.

[0021] See also Figure 1The wide spectrum light source generator includes a pump laser 1, a wavelength division multiplexing coupler 2 and an active optical fiber 3 coupled in sequence. The optical signal is output from the wavelength division multiplexing coupler 2 to the first port 4-1 of the three-terminal optical fiber circulator 4. The tail end of the active optical fiber 3 may or may not contain a Faraday reflector or an ordinary reflector. The light emitted by the pump laser 1 excites the active optical fiber 3 to emit amplified spontaneous emission ASE light through the wavelength division multiplexing coupler 2; the ASE light is input to the first port 4-1 of the three-terminal optical fiber circulator with a filter 4-4, and the ASE light passes through the birefringence and Faraday element inside the three-terminal optical fiber circulator, and then passes through the filter 4-4 and is output from the second port 4-2 of the three-terminal optical fiber circulator, thereby entering the input end of the multifunctional optical chip 5. The multifunctional optical chip 5 is integrated with a polarizer, a Y-type beam splitter and a phase modulator. The Y-type beam splitter in the multifunctional optical chip 5 splits the light beam into two and then outputs it, wherein the upper light beam passes through the optical fiber sensor ring 6 in a clockwise direction and then returns to the multifunctional optical chip 5; the lower light beam passes through the optical fiber sensor ring 6 in a clockwise direction and then returns to the multifunctional optical chip 5; The light beam passes through the optical fiber sensor ring 6 in a counterclockwise direction and then returns to the multifunctional optical chip 5; the two clockwise and counterclockwise light beams are synthesized by the Y-type beam splitter in the multifunctional optical chip 5 to form interference, and return to the second port 4-2 of the special three-terminal optical fiber circulator through the input end of the multifunctional optical chip 5. The light enters the second port 4-2 of the three-terminal optical fiber circulator and first passes through the internal filter 4-4, then passes through the internal Faraday element and birefringence element, and is output from the third port 4-3 of the three-terminal optical fiber circulator, and then is converted into an electrical signal by the photodetector 7, and is produced by the signal processing unit 8 and fed back to the phase modulator in the multifunctional optical chip 5, and at the same time outputs the angular velocity signal of the gyroscope relative to the inertial reference system.

[0022] When the ASE light passes through the special three-terminal fiber circulator for the first time, the internal filter 4-4 near the second port 4-2 stabilizes the average wavelength of the output light source. When the ASE light returns from the waveguide and passes through the special three-terminal fiber circulator for the second time, the internal filter 4-4 near the second port 4-2 reduces the change in the average wavelength caused by the change in the filtering characteristics of the multifunctional optical chip 5 and the fiber sensor ring 6 with the temperature, thereby stabilizing the scale factor of the gyroscope. The ASE spectrum coupled output by the pump laser 1, the active optical fiber 3 and the wavelength division multiplexing coupler 2 is shaped into a Gaussian spectrum by the three-terminal fiber circulator 4 integrated with the filter 4-4, effectively improving the zero-bias stability of the gyroscope. At the same time, the optical power output from the second port 4-2 of the three-terminal fiber circulator is several times larger than that of the traditional solution (theoretically 4 times larger), so the gyroscope output of the present application has a higher signal-to-noise ratio.

[0023] Alternatively, the three-terminal fiber circulator 4 integrated with the filter 4-4 can be replaced by an independent circulator plus an independent filter to achieve the same function, that is, the three-terminal fiber circulator 4 with the filter 4-4 inserted in the second port 4-2 is replaced by an independent circulator plus an independent filter, and the independent filter is connected between the second port 4-2 of the independent circulator and the multifunctional optical chip 5. Or an isolator, a coupler and a filter are used to achieve the same function, wherein the filter is inserted between the coupler and the multifunctional chip, that is, the three-terminal fiber circulator 4 with the filter 4-4 inserted in the second port 4-2 is replaced by an isolator, a coupler and a filter, the isolator is connected between the wide spectrum light source generator and the coupler, the filter is connected between the first output port of the coupler and the multifunctional chip, and the second output port of the coupler is coupled to the input end of the photodetector 7.

[0024] Embodiment 2

[0025] See also Figure 2 The difference between this embodiment and the first embodiment is that the broadband light source generator in this embodiment includes a pump laser 1, a wavelength division multiplexing coupler 2 and an active optical fiber coupled in sequence, and the optical signal is output from the active optical fiber 3 to the first port 4-1 of the three-terminal optical fiber circulator 4. A Faraday reflector or an ordinary reflector is arranged at the other end of the wavelength division multiplexing coupler 2.

[0026] The following are example application parameters of the fiber optic gyroscope of the present application: the pump laser 1 adopts a 980nm semiconductor laser, the wavelength division multiplexing coupler 2 adopts 980 / 1550nm, the active optical fiber 3 adopts a 10-meter erbium-doped optical fiber, the three-terminal optical fiber circulator has a filter 4-4 inside, the second port 4-2 is a polarization-maintaining pigtail, and the spectrum of the light after passing through the filter 4-4 twice is guaranteed to be Gaussian distributed, the multifunctional optical chip 5 adopts a lithium niobate integrated chip, which is a 1550nm band device, the optical fiber sensor ring 6 adopts 1200 meters of polarization-maintaining optical fiber to form an optical fiber ring with an average diameter of 92mm, the photodetector 7 is a PIN-FET, and the signal processing unit 8 is composed of a preamplifier, an AD converter, an FPGA chip and a DA converter. The gyroscope of the present application measures a long-term zero drift of 0.001 degrees / hour for 24 hours, and a scale factor change of 1ppm.

Claims

1. A high-precision fiber optic gyroscope with a stable scale factor, characterized in that: It comprises a broadband light source generator, a three-terminal optical fiber circulator (4) with a filter (4-4) inserted into the second port (4-2), a multifunctional optical chip (5), an optical fiber sensor ring (6), a photodetector (7) and a signal processing unit (8); The wide spectrum light source generator outputs an optical signal to the first port (4-1) of the three-terminal optical fiber circulator (4). The second port (4-2) of the three-terminal optical fiber circulator (4) is coupled to the input end of the multifunctional optical chip (5). A polarizer, a Y-type beam splitter and a phase modulator are integrated on the multifunctional optical chip (5). The two output ports of the Y-type beam splitter are coupled with the two input ports of the optical fiber sensing ring (6). The third port (4-3) of the three-terminal optical fiber circulator is coupled to the input end of the photodetector (7). The output end of the photodetector (7) is connected to a signal processing unit (8), and the modulation and feedback superposition output end of the signal processing unit (8) is electrically connected to a phase modulator of the multifunctional optical chip (5). At the same time, the signal processing unit (8) outputs an angular velocity signal; The wide spectrum light source generator comprises a pump laser (1), a wavelength division multiplexing coupler (2) and an active optical fiber (3) which are coupled in sequence. Wherein, the optical signal is output from the wavelength division multiplexing coupler (2) to the first port (4-1) of the three-terminal optical fiber circulator (4), and a Faraday reflector or a common reflector is arranged at the tail end of the active optical fiber (3); or, The optical signal is output from the active optical fiber (3) to the first port (4-1) of the three-terminal optical fiber circulator (4), and a Faraday reflector or a common reflector is arranged at one end of the wavelength division multiplexing coupler (2); The second port (4-2) of the three-terminal optical fiber circulator (4) is coupled to the input end of the multifunctional optical chip (5) via a polarization-maintaining optical fiber.

2. The high-precision fiber optic gyroscope with stable scale factor according to claim 1, characterized in that: The three-terminal optical fiber circulator (4) with a filter (4-4) inserted in the second port (4-2) is replaced by an independent circulator plus an independent filter, and the independent filter is connected between the second port (4-2) of the independent circulator and the multifunctional optical chip (5).

3. The high-precision fiber optic gyroscope with stable scale factor according to claim 1, characterized in that: A three-terminal optical fiber circulator (4) having a filter (4-4) inserted into the second port (4-2) is replaced by an isolator, a coupler and a filter. The isolator is connected between a wide-spectrum light source generator and the coupler, the filter is connected between a first output port of the coupler and a multifunctional chip, and the second output port of the coupler is coupled to an input end of a photodetector (7).

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