A Real-time Detection Method and Device for Central Wavelength Drift of Fiber Optic Gyroscope

Abstract

The present invention relates to the field of fiber optic gyroscopes, and particularly to a method and device for real-time detection of the central wavelength drift of a fiber optic gyroscope. The present invention discloses a method and device for real-time detection of the central wavelength drift of a fiber optic gyroscope. Among them, the method for real-time detection of the central wavelength drift of a fiber optic gyroscope includes the following steps: Step S1, input the optical signal output by the fiber optic gyroscope into the FP cavity, and respectively detect the output optical power of the reflected light of the FP cavity and the output optical power of the fiber optic gyroscope; Step S2, obtain the drift situation of the central wavelength of the fiber optic gyroscope by detecting the change situation of the ratio of the output optical power of the reflected light of the FP cavity and the output optical power of the fiber optic gyroscope. The present invention can detect the drift situation of the central wavelength of the fiber optic gyroscope in real time. The detection device has a simple structure, a small volume, is easy to be directly mounted on the fiber optic gyroscope, and has a low cost and is easy to implement.

Description

Technical Field

[0001] The present invention belongs to the field of fiber optic gyroscopes, and particularly relates to a method and device for real-time detection of the central wavelength drift of a fiber optic gyroscope. Background Art

[0002] A fiber optic gyroscope is an all-optical solid-state inertial instrument based on the Sagnac principle without mechanical moving parts. Due to its inherent advantages such as small volume, low power consumption, light weight, and long life, it has been widely used in inertial navigation systems. With the improvement of the requirements for sensor accuracy in modern weapons and inertial navigation, suppressing the scale factor error of fiber optic gyroscopes in harsh environments has become the most important topic in the industry. For a digital closed-loop fiber optic gyroscope, its scale factor K can be expressed as:

[0003]

[0004] wherein, L is the length of the fiber optic loop, D is the diameter of the fiber optic loop, c is the speed of light, is the central wavelength of the optical signal, V pp is the peak-to-peak value of the feedback modulation voltage, V 2π is the 2π voltage of the integrated optical modulator (Y waveguide). It can be seen from this that the parameters affecting the scale factor K of the fiber optic gyroscope mainly include the central wavelength of the optical signal, the diameter D and length L of the fiber optic loop, and the waveguide voltage. Through the parameter design optimization of the fiber optic loop, temperature modeling, etc., and at the same time combined with the digital closed-loop feedback modulation and demodulation circuit technology, the influence of the waveguide voltage on the scale factor error of the fiber optic gyroscope has been suppressed within 10 -6 or less.

[0005] Based on the above, the central wavelength of the optical signal has become the decisive factor affecting the scale factor K error. Real-time monitoring of the change in the output spectrum of the fiber optic gyroscope, calculating the corresponding central wavelength drift, and performing feedback compensation accordingly can significantly improve the stability of the system. However, the spectrometer-type equipment used in the laboratory is too large in volume to be directly mounted on the fiber optic gyroscope. Therefore, it is of great significance to study a simpler and more effective scheme for real-time detection of the drift of the central wavelength of the fiber optic gyroscope. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and device for real-time detection of the central wavelength drift of a fiber optic gyroscope to solve the above-mentioned existing technical problems.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: a method for real-time detection of the central wavelength drift of a fiber optic gyroscope, including the following steps:

[0008] Step S1: Input the optical signal output by the fiber optic gyro into the FP cavity, and respectively detect the output optical power of the reflected light of the FP cavity and the output optical power of the fiber optic gyro.

[0009] Step S2: Obtain the drift condition of the central wavelength of the fiber optic gyro by detecting the change condition of the ratio of the output optical power of the reflected light of the FP cavity to the output optical power of the fiber optic gyro.

[0010] Further, the FP cavity is a fiber optic FP cavity.

[0011] Furthermore, Step S1 further includes: adjusting the cavity length of the fiber optic FP cavity so that the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the input optical power changes linearly with the central wavelength of the fiber optic gyro.

[0012] Further, Step S2 is specifically: obtain in advance the change curve of the ratio of the output optical power of the reflected light of the FP cavity to the output optical power of the fiber optic gyro with the central wavelength of the fiber optic gyro through experiments, and then obtain the drift condition of the central wavelength of the fiber optic gyro according to the detected ratio of the output optical power of the reflected light of the FP cavity to the output optical power of the fiber optic gyro in combination with the change curve.

[0013] The present invention also discloses a real-time detection device for the drift of the central wavelength of a fiber optic gyro, which uses the above real-time detection method for the drift of the central wavelength of a fiber optic gyro to perform real-time detection.

[0014] Further, it includes a light source, a circulator, a Y waveguide, an optical fiber loop, a 2×2 coupler, an FP cavity, a first optical signal detector, a second optical signal detector, and a processor. The light source is connected to the a port of the circulator, the b port of the circulator is connected to the head end of the Y waveguide, the tail end of the Y waveguide is connected to the optical fiber loop, the c port of the circulator is connected to the a port of the 2×2 coupler, the b port of the 2×2 coupler is connected to the FP cavity, the c port of the 2×2 coupler is connected to the first optical signal detector, the d port of the 2×2 coupler is connected to the second optical signal detector, and the first optical signal detector and the second optical signal detector are respectively connected to the processor.

[0015] Furthermore, the light source is a broadband light source.

[0016] Further, the FP cavity is a fiber optic FP cavity.

[0017] Furthermore, the fiber optic FP cavity includes a single-mode optical fiber, a capillary tube, and a glass diaphragm. One end of the single-mode optical fiber is fusion-fixed to the first end of the capillary tube, and the glass diaphragm is fixedly arranged on the second end of the capillary tube.

[0018] Furthermore, the outer diameter of the single-mode optical fiber is the same as the outer diameter of the capillary tube.

[0019] Further, the glass diaphragm is formed by fusing another single-mode optical fiber to the second end of the capillary and then cutting off the unnecessary part of the single-mode optical fiber.

[0020] Further, the first optical signal detector and the second optical signal detector are implemented by using photodiodes.

[0021] Advantageous technical effects of the present invention:

[0022] The present invention can detect the drift of the central wavelength of the fiber optic gyro in real time. The detection device has a simple structure, a small volume, is easy to be directly mounted on the fiber optic gyro, and only requires common optical devices such as optical signal detectors and FP cavities, with low cost and easy to implement. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a flowchart of the method for real-time detection of the central wavelength drift of the fiber optic gyro in a specific embodiment of the present invention;

[0025] Figure 2 It is a spectral diagram of the light source, the output spectrum of the fiber optic ring, and the reflected light spectrum of the fiber optic FP cavity in a specific embodiment of the present invention;

[0026] Figure 3 It is a curve graph showing the change of the ratio of the reflected light output optical power of the fiber optic FP cavity to the output optical power of the fiber optic gyro with the central wavelength of the fiber optic gyro in a specific embodiment of the present invention;

[0027] Figure 4 It is a structural diagram of the device for real-time detection of the central wavelength drift of the fiber optic gyro in a specific embodiment of the present invention;

[0028] Figure 5 It is a structural diagram of the fiber optic FP cavity in a specific embodiment of the present invention. Detailed Embodiments

[0029] To further illustrate the embodiments, the present invention provides drawings. These drawings are a part of the disclosure of the present invention, mainly used to illustrate the embodiments, and can be used to explain the operating principle of the embodiments in combination with the relevant descriptions in the specification. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] As Figure 1 shown, a real-time detection method for the central wavelength drift of an optical fiber gyroscope includes the following steps:

[0032] Step S1: Input the optical signal output by the optical fiber gyroscope into the FP cavity, and respectively detect the output optical power of the reflected light of the FP cavity and the output optical power of the optical fiber gyroscope.

[0033] The FP cavity is preferably an optical fiber FP cavity, which has a simple structure and is easy to implement. However, it is not limited thereto. In some embodiments, the FP cavity can also be implemented using other existing FP cavities. Specifically, the two optical signals output by the optical fiber loop of the optical fiber gyroscope are coupled by a Y waveguide and then proportionally divided into two optical signals, namely the first optical signal and the second optical signal. The first optical signal is output to an optical signal detector for power detection, thereby detecting the optical power output by the optical fiber loop, that is, the output optical power of the optical fiber gyroscope.

[0034] The second optical signal is output to the optical fiber FP cavity, and after being reflected by the optical fiber FP cavity, it is output to an optical signal detector for power detection, thereby detecting the output optical power of the reflected light of the optical fiber FP cavity. The output optical power I of the reflected light of the optical fiber FP cavity out and the input optical power I in have the following relationship:

[0035]

[0036] where R is the reflectivity of the optical fiber FP cavity, and δ is the phase difference of the optical fiber FP cavity. In this embodiment, δ = 4πL1 / λ, L1 is the cavity length of the optical fiber FP cavity, and λ is the wavelength of the optical signal transmitted in the optical fiber FP cavity. Therefore, the change in the wavelength λ is reflected in the phase change and ultimately in the power change of the optical signal detector. By adjusting the size of the cavity length L1 of the optical fiber FP cavity, the position of the filtered wavelength can be changed, so that the ratio of the output optical power of the reflected light of the optical fiber FP cavity to the input optical power changes linearly with the central wavelength of the optical fiber gyroscope, that is, the ratio of the output optical power of the reflected light of the optical fiber FP cavity to the output optical power of the optical fiber gyroscope changes linearly with the central wavelength of the optical fiber gyroscope. Figure 2 shows the reflected light spectrum output by the preferred optical fiber FP cavity in this embodiment, where the light source spectrum is the output optical spectrum of the light source that provides the optical signal for the optical fiber loop.

[0037] Step S2: Obtain the drift condition of the central wavelength of the optical fiber gyroscope by detecting the change condition of the ratio of the output optical power of the reflected light of the FP cavity to the output optical power of the optical fiber gyroscope.

[0038] Specifically, the detected output optical power of the reflected light of the fiber optic FP cavity and the output optical power of the fiber optic gyroscope are processed and calculated in the processor to obtain the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the output optical power of the fiber optic gyroscope. Since the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the output optical power of the fiber optic gyroscope varies linearly with the central wavelength of the fiber optic gyroscope, in this embodiment, the variation curve is as Figure 3 shown. When the central wavelength of the fiber optic gyroscope changes (drifts), the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the output optical power of the fiber optic gyroscope will also change. Moreover, when the central wavelength of the fiber optic gyroscope increases, the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the output optical power of the fiber optic gyroscope decreases, showing good linearity. Therefore, by detecting the change in the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the output optical power of the fiber optic gyroscope in real time, the drift of the central wavelength of the fiber optic gyroscope can be obtained, realizing real-time detection of the drift of the central wavelength of the fiber optic gyroscope.

[0039] Furthermore, the variation curve of Figure 3 can be obtained through experiments in advance and stored in the processor. During the detection process, by detecting the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the output optical power of the fiber optic gyroscope in real time, and then according to the Figure 3 variation curve, the real-time central wavelength of the fiber optic gyroscope can be obtained, which can be used in combination with subsequent wavelength compensation methods to improve the accuracy of the fiber optic gyroscope.

[0040] The present invention also provides a device for real-time detection of the drift of the central wavelength of a fiber optic gyroscope, which uses the above-mentioned method for real-time detection of the drift of the central wavelength of a fiber optic gyroscope to detect the drift of the central wavelength of a fiber optic gyroscope in real time.

[0041] As Figure 4 shown, the device for real-time detection of the drift of the central wavelength of the fiber optic gyroscope in this specific embodiment includes a light source 1, a circulator 2, a Y waveguide 3, a fiber optic loop 4, a 2×2 coupler 5, an FP cavity 6, a first optical signal detector 7, a second optical signal detector 8, and a processor (not shown in the figure). The light source 1 is connected to the a port of the circulator 2. In this specific embodiment, the light source 1 is a broadband light source with better adaptability. The light source 1 can be an LED light source, a laser light source, etc. The output end of the light source 1 is connected to the a port of the circulator 2 through an optical fiber.

[0042] The circulator 2 is a multi-port device that transmits the incident wave entering any of its ports in the direction determined by the static bias magnetic field to the next port in sequence. It is a non-reversible device with several ports and can unidirectionally transmit high-frequency signal energy. The b port of the circulator 2 is connected to the head end of the Y waveguide 3, and the tail end of the Y waveguide 3 is connected to the two ports of the fiber optic loop 4.

[0043] The Y waveguide 3 integrates a polarizer, a beam splitter, and a phase modulator, has good amplitude-frequency characteristics, can achieve high-frequency and multi-harmonic modulation, and has high integration and small volume, which not only reduces the volume of the fiber optic gyroscope, but also improves the stability and reliability of the fiber optic gyroscope.

[0044] Preferably, in this specific embodiment, the Y waveguide 3 is a lithium niobate Y waveguide, which can not only reduce the size of the fiber optic gyroscope, but also facilitate mass production and cost reduction, while increasing the modulation bandwidth, but not limited thereto.

[0045] The c port of the circulator 2 is connected to the a port of the 2×2 coupler 5. The 2×2 coupler 5 has two input ports a and c and two output ports b and d. The optical signal input from the input port a or c is distributed by the coupling region and output from the output ports b and d; the optical signal input from the output port b or d is distributed by the coupling region and output from the input ports a and c. The distribution ratio is called the coupling ratio, and the coupling ratio can be selected between 1% and 99%.

[0046] The b port of the 2×2 coupler 5 is connected to the FP cavity 6, the c port of the 2×2 coupler is connected to the first optical signal detector 7, the d port of the 2×2 coupler 5 is connected to the second optical signal detector 8, and the first optical signal detector 7 and the second optical signal detector 8 are respectively connected to the processor.

[0047] Preferably, in this specific embodiment, the FP cavity 6 is a fiber optic FP cavity, which has a simple structure, is easy to implement, and has low cost, but not limited thereto. In some embodiments, the FP cavity 6 can also be implemented using other existing FP cavities.

[0048] Specifically, as Figure 5 shown, the FP cavity 6 includes a single-mode optical fiber 61, a capillary 62, and a glass diaphragm 63. One end of the single-mode optical fiber 61 is fixedly fused to the first end of the capillary 62, and the glass diaphragm 63 is fixedly arranged on the second end of the capillary 62.

[0049] Preferably, in this specific embodiment, the outer diameter of the single-mode optical fiber 61 is the same as the outer diameter of the capillary 62, which is convenient for the two to be fused and has a more compact structure, but not limited thereto. In some embodiments, the outer diameter of the single-mode optical fiber 61 can also be slightly smaller than the outer diameter of the capillary 62; or the outer diameter of the single-mode optical fiber 61 can also be slightly larger than the outer diameter of the capillary 62.

[0050] The cavity length of the FP cavity 6 must match the optical path difference of the Y waveguide 3. In this specific embodiment, the manufacturing process of the FP cavity 6 is as follows: The flat end of the single-mode optical fiber 61 with a cut flat end face is fusion-spliced to the first end of a capillary 62 with the same outer diameter; according to the matching cavity length, a flat end face (the second end face) is cut on the capillary 62 at a certain distance along the fusion-splicing surface; the cut flat end face is fusion-spliced to another single-mode optical fiber; the unnecessary part of the other single-mode optical fiber is cut off to obtain a glass diaphragm 63, that is, the structure of the FP cavity 6 is obtained. Using this manufacturing process, the process is simple, easy to implement, and has low cost, but it is not limited thereto.

[0051] In this specific embodiment, the first optical signal detector 7 and the second optical signal detector 8 are preferably implemented using photodiodes, which have a simple structure, small volume, and low cost. Of course, in some embodiments, the first optical signal detector 7 and the second optical signal detector 8 can also be implemented using other optical sensors such as CCD sensors.

[0052] The processor can be implemented using programmable logic devices such as MCU processors and field-programmable gate arrays (FPGAs). Preferably, the processor can be implemented using the processor of the fiber optic gyroscope, without the need to additionally increase a processor, which not only saves cost, but also has a simple structure and small volume.

[0053] The optical fiber loop 4 is formed by winding glass optical fibers. The light source 1, the circulator 2, the Y waveguide 3, the optical fiber loop 4, the 2×2 coupler 5, the FP cavity 6, the first optical signal detector 7, and the second optical signal detector 8 are all connected using optical fibers, which is not only easy to connect, but also has low optical transmission loss and low cost.

[0054] Detection process:

[0055] The broadband optical signal emitted by the light source 1 is input from port a of the circulator 2 and output from port b of the circulator 2 to the Y waveguide 3. After being subjected to phase modulation, beam splitting, etc. by the Y waveguide 3, it is split into two optical signals and output to the two ports of the optical fiber loop 4. The two optical signals output by the optical fiber loop 4 are coupled by the Y waveguide 3 and input to port b of the circulator 2. After passing through the circulator 2, it is output from port c of the circulator 2 to port a of the 2×2 coupler 5. After being distributed by the 2×2 coupler 5, one path is output from port b of the 2×2 coupler 5 to the FP cavity 6, and the other path is output from port d of the 2×2 coupler 5 to the second optical signal detector 8 for optical power detection (output optical power detection of the fiber optic gyroscope).

[0056] The reflected light of the FP cavity 6 is input from the b port of the 2×2 coupler 5. After being distributed by the 2×2 coupler 5, one path is output from the c port of the 2×2 coupler 5 to the first optical signal detector 7 for optical power detection (the reflected light output optical power detection of the FP cavity 6). The first optical signal detector 7 and the second optical signal detector 8 transmit the detected optical power to the processor. The processor processes and calculates the optical power detected by the first optical signal detector 7 and the second optical signal detector 8, obtains the ratio of the reflected light output optical power of the FP cavity 6 to the output optical power of the fiber optic gyroscope (i.e., the fiber optic loop 4), and then determines whether the ratio of the reflected light output optical power of the FP cavity 6 to the output optical power of the fiber optic gyroscope has changed. If it has changed, it indicates that the center wavelength of the fiber optic gyroscope has drifted; if it has not changed, it indicates that the center wavelength of the fiber optic gyroscope has not drifted, that is, the real-time detection of the drift of the center wavelength of the fiber optic gyroscope is realized.

[0057] Further, after the processor obtains the ratio of the reflected light output optical power of the FP cavity 6 to the output optical power of the fiber optic gyroscope (i.e., the fiber optic loop 4), and then according to Figure 3 the change curve, the real-time center wavelength of the fiber optic gyroscope can be obtained, which can be used in combination with subsequent wavelength compensation methods to improve the accuracy of the fiber optic gyroscope.

[0058] The present invention can detect the drift of the center wavelength of the fiber optic gyroscope in real time. The detection device has a simple structure, a small volume, is easy to be directly mounted on the fiber optic gyroscope, and only requires common optical devices such as optical signal detectors and FP cavities, with low cost and easy to implement.

[0059] Although the present invention is specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes can be made to the present invention in terms of form and details without departing from the spirit and scope of the present invention defined by the appended claims, and all are within the protection scope of the present invention.

Claims

1. A real-time detection method for the central wavelength drift of an optical fiber gyroscope, characterized in that, It includes the following steps: Step S1: Input the optical signal output by the fiber optic gyro into the FP cavity, and respectively detect the output optical power of the reflected light of the FP cavity and the output optical power of the fiber optic gyro; Step S2: Obtain the drift condition of the central wavelength of the fiber optic gyro by detecting the change condition of the ratio of the output optical power of the reflected light of the FP cavity and the output optical power of the fiber optic gyro; Couple the two optical signals output by the fiber optic loop of the fiber optic gyro through a Y waveguide and then divide them into two optical signals proportionally, which are the first optical signal and the second optical signal respectively. The first optical signal is output to an optical signal detector for power detection, so as to detect the optical power output by the fiber optic loop; The second optical signal is output to the FP cavity. After being reflected by the FP cavity, it is output to the optical signal detector for power detection, so as to detect the output optical power of the reflected light of the FP cavity. The output optical power I of the reflected light of the FP cavity out and the input optical power I in are related as follows: Wherein, R is the reflectivity of the FP cavity, δ is the phase difference of the FP cavity, L1 is the cavity length of the fiber optic FP cavity, and λ is the wavelength of the optical signal transmitted in the FP cavity.

2. The real-time detection method for the central wavelength drift of an optical fiber gyroscope according to claim 1, characterized in that: The FP cavity is a fiber optic FP cavity.

3. The real-time detection method for the central wavelength drift of an optical fiber gyroscope according to claim 2, wherein The step S1 further includes: adjusting the cavity length of the fiber optic FP cavity so that the ratio of the output optical power of the reflected light of the fiber optic FP cavity to the input optical power changes linearly with the central wavelength of the fiber optic gyro.

4. The real-time detection method for the central wavelength drift of an optical fiber gyroscope according to claim 1, characterized in that, The step S2 specifically is: pre-obtain the change curve of the ratio of the output optical power of the reflected light of the FP cavity and the output optical power of the fiber optic gyro with the central wavelength of the fiber optic gyro through experiments, and then obtain the drift condition of the central wavelength of the fiber optic gyro by combining the detected ratio of the output optical power of the reflected light of the FP cavity and the output optical power of the fiber optic gyro with the change curve.

5. A real-time detection device for the central wavelength drift of an optical fiber gyroscope, characterized in that, Adopt the real-time detection method for the drift of the central wavelength of the fiber optic gyro described in any one of claims 1-4 to detect the drift of the central wavelength of the fiber optic gyro in real time.

6. The real-time detection device for the central wavelength drift of the fiber optic gyroscope according to claim 5, characterized in that: It includes a light source, a circulator, a Y waveguide, a fiber optic loop, a 2×2 coupler, an FP cavity, a first optical signal detector, a second optical signal detector and a processor. The light source is connected to the a port of the circulator, the b port of the circulator is connected to the head end of the Y waveguide, the tail end of the Y waveguide is connected to the fiber optic loop, the c port of the circulator is connected to the a port of the 2×2 coupler, the b port of the 2×2 coupler is connected to the FP cavity, the c port of the 2×2 coupler is connected to the first optical signal detector, the d port of the 2×2 coupler is connected to the second optical signal detector, and the first optical signal detector and the second optical signal detector are respectively connected to the processor.

7. The real-time detection device for the central wavelength drift of the fiber optic gyroscope according to claim 6, characterized in that: The light source is a broadband light source.

8. The real-time detection device for the central wavelength drift of the fiber optic gyroscope according to claim 6, characterized in that: The FP cavity is a fiber optic FP cavity. The fiber optic FP cavity includes a single-mode fiber, a capillary tube and a glass diaphragm. One end of the single-mode fiber is fixedly fused to the first end of the capillary tube, and the glass diaphragm is fixedly arranged on the second end of the capillary tube.

9. The real-time detection device for the central wavelength drift of an optical fiber gyroscope according to claim 8, characterized in that: The glass diaphragm is formed by fusing another single-mode fiber to the second end of the capillary tube and then cutting off the unnecessary part of the single-mode fiber.

10. The real-time detection device for the central wavelength drift of the fiber optic gyroscope according to claim 6, characterized in that: The first optical signal detector and the second optical signal detector are implemented by photodiodes.

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