A High-Precision Fiber Optic Gyroscope Using a Relative Intensity Noise Optical Cancellation Scheme

Abstract

A high-precision fiber optic gyroscope using a relative intensity noise optical cancellation scheme. It adopts an all-fiber structure and utilizes the correlation between the optical signal at the idle end of the coupler and the relative intensity of the interference signal to perform noise cancellation, thereby improving the accuracy of the fiber optic gyroscope. A relative intensity noise suppression technology for the optical cancellation scheme is proposed to reduce the process difficulty and production cost of realizing the high-precision fiber optic gyroscope.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber optic gyroscopes, and particularly relates to a high-precision fiber optic gyroscope using a relative intensity noise optical cancellation scheme. Background Art

[0002] Optical signal noise exists throughout the entire process of signal detection. The main reasons for its generation are the fluctuations in light intensity and the volatility of the number of photons. The noise generated due to the fluctuations in light intensity is called relative intensity noise; the noise generated due to the fluctuations in the number of photons is called photon noise, which becomes shot noise after photoelectric conversion; the noise generated by the transimpedance amplifier's conversion resistance in the photoelectric converter is thermal noise.

[0003] When the optical power is small, shot noise is the main noise of the fiber optic gyroscope; as the optical power increases, the relative intensity noise increases linearly and gradually becomes the main noise of the fiber optic gyroscope. The angular random walk generated by shot noise and thermal noise decreases as the optical power increases, while the angular random walk generated by relative intensity noise is independent of the optical power. Therefore, as Figure 1 (Schematic diagram of the optical path of an ultra-high-precision fiber optic gyroscope), the used ASE light source has the advantages of high power, good wavelength stability, relatively weak coherence, etc. Its optical power can reach more than 10 mW. Under such high optical power conditions, to reduce its angular random walk and improve the accuracy of the detected signal, it is necessary to suppress its relative intensity noise.

[0004] Some RIN suppression technologies and new optical path structure suppression technologies have been proposed in domestic and foreign patents. However, with a deeper understanding of fiber optic gyroscopes, a noise subtraction method, that is, an optical path cancellation method, has been proposed. The optical path cancellation method uses the correlation between the optical signal at the idle end of the coupler and the relative intensity of the interference signal to perform noise cancellation. This method adopts an all-fiber structure, reduces the circuit noise factor, and has relatively simple technology and lower cost. Summary of the Invention

[0005] The present invention adopts an all-fiber structure, uses the correlation between the optical signal at the idle end of the coupler and the relative intensity of the interference signal to perform noise cancellation, thereby improving the accuracy of the fiber optic gyroscope, proposing a relative intensity noise suppression technology for an optical cancellation scheme, and reducing the process difficulty and production cost of realizing a high-precision fiber optic gyroscope.

[0006] The technical solution of the present invention is described in detail as follows:

[0007] A high-precision fiber optic gyro relative intensity noise optical cancellation scheme, the optical components include an ASE light source, a 2×2 fiber optic coupler (50:50), a 1×2 fiber optic coupler (1:99), a Y waveguide, a detector, and a polarization-maintaining fiber optic loop. A 1×2 fiber optic coupler (1:99) is provided between the detector and the 2×2 fiber optic coupler (50:50). The ASE light source is divided into two paths by the 2×2 fiber optic coupler. One path is connected to the Y waveguide (the length of the pigtail fiber between the coupler and the waveguide is L1), and the other path is connected to the 1 end of the ×2 end of the 1×2 fiber optic coupler (1:99) (this length is set as L3). The light connected to the Y waveguide passes through the Y waveguide and is divided into two paths to enter the polarization-maintaining fiber optic loop. The interference light coming out of the polarization-maintaining fiber optic loop passes through two couplers (the length of the feedback end of the 2×2 fiber optic coupler connected to the 99 end of the ×2 end of the 1×2 fiber optic coupler is L2).

[0008] The relationship among L1, L2, and L3 is 2L1 + L2 = L3, so that the optical path difference between the light passing through the coupler and the Y waveguide and the light passing through the pigtail fiber of the other coupler is equal to the transit time of the light passing through the polarization-maintaining fiber optic loop.

[0009] The advantages and positive effects of the present invention are as follows:

[0010] In the optical path of the fiber optic gyro of the present invention, a 1:99 fiber optic coupler of 1×2 is added. By using the correlation between the optical signal at the idle end of the coupler and the relative intensity of the interference signal, and by adjusting the optical path traveled by the light of the ASE light source to compensate for the optical path difference, the relative intensity noise of the light after the light of the ASE light source passes through the optical path is canceled, thereby improving the accuracy of the fiber optic gyro. This scheme does not require additional noise suppression techniques, nor does it require an increase in the design of the modulation and demodulation circuit and the gyro debugging difficulty. Its implementation method is simple and the cost is lower. Description of the Drawings

[0011] Figure 1 It is the optical path diagram of the existing standard high-precision fiber optic gyro;

[0012] Figure 2 It is the optical path scheme of the present invention. Detailed Embodiment

[0013] The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0014] 1) Design and add a 1 / 99 fiber optic coupler and a polarization-maintaining fiber L3 for compensating the optical path difference.

[0015] 2) Match the optical device and the pigtail according to the actual optical path difference, and calculate the optical path difference in the actual optical path according to the length of the optical fiber loop, the length of the pigtail of the optical fiber loop, and the length of the pigtail of the Y waveguide.

[0016] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the protection scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-precision fiber optic gyroscope using a relative intensity noise optical cancellation scheme, mainly including: Noise cancellation is performed by using the correlation between the optical signal at the idle end of the coupler and the relative intensity of the interference signal; The optical components include an ASE light source, a 2×2 fiber coupler, a 1×2 fiber coupler, a Y waveguide, a detector, and a polarization-maintaining fiber loop. A 1×2 fiber coupler is provided between the detector and the 2×2 fiber coupler. The ASE light source is split into two paths by the 2×2 fiber coupler. One path is connected to the Y waveguide, and the length of the pigtail fiber between the coupler and the waveguide is set as L1. The other path is connected to the 1 end of the ×2 end of the 1×2 fiber coupler, and this length is set as L3. The light passing through the Y waveguide is split into two paths and enters the polarization-maintaining fiber loop. The interference light coming out of the polarization-maintaining fiber loop passes through two couplers. The length of the feedback end of the 2×2 fiber coupler connected to the 99 end of the ×2 end of the 1×2 fiber coupler is set as L2; The relationship among L1, L2, and L3 is 2L1 + L2 = L3, such that the optical path difference between the light passing through the coupler and the Y waveguide and the light passing through the pigtail fiber of the coupler is equal to the transit time after the light passes through the polarization-maintaining fiber loop; The design adds a 1 / 99 fiber coupler and a polarization-maintaining fiber L3 for compensating the optical path difference; Match the optical devices and pigtail fibers according to the actual optical path difference, and calculate the optical path difference in the actual optical path according to the length of the fiber loop, the length of the pigtail fiber of the fiber loop, and the length of the pigtail fiber of the Y waveguide.

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