A frequency characteristic measuring device for fiber coupler used in fiber optic gyroscope

Abstract

This invention provides a device for measuring the frequency characteristics of fiber optic couplers used in fiber optic gyroscopes. It mainly consists of a light source, a Y-waveguide, a detector, a signal detection and processing circuit, a light source driver, and a host computer. It is used during the manufacturing process of fiber optic gyroscopes to detect the frequency characteristics of the fiber optic couplers. By applying a frequency-sweeping periodic signal to the Y-waveguide as an excitation source, the changes in the optical signal output through the fiber optic coupler are detected, thereby obtaining the response of the fiber optic coupler to signals of different frequencies. This device eliminates resource waste and quality risks caused by trial and error and multiple rework, improves the first-pass yield of fiber optic gyroscope manufacturing, saves manufacturing costs, and increases production efficiency.

Description

Technical Field

[0001] This invention relates to a frequency characteristic measurement device, specifically to a frequency characteristic measurement device for a fiber optic coupler used in a fiber optic gyroscope. Background Technology

[0002] A fiber optic gyroscope is an angular rate sensor based on the Sagnac effect. It can be used to sense the angular motion of a carrier and output angular rate information after signal processing.

[0003] Currently, the manufacturing process of fiber optic gyroscopes suffers from a lack of fiber optic coupler frequency characteristic testing devices. This prevents the accurate detection of the fiber optic coupler's frequency characteristics, leading to a trial-and-error approach. After the gyroscope is manufactured, accuracy testing is performed to identify problems with the fiber optic coupler, resulting in rework and replacement until the issue is resolved. The inability to test the fiber optic coupler's frequency characteristics, coupled with the lack of information about its performance, easily leads to accuracy issues and rework. Furthermore, the replacement fiber optic couplers are randomly selected, often resulting in multiple reworks of the same gyroscope, which is time-consuming, labor-intensive, and carries significant quality risks, impacting product reliability. Summary of the Invention

[0004] The purpose of this invention is to provide a frequency characteristic measurement device for fiber optic couplers used in fiber optic gyroscopes, which solves the above-mentioned technical problems.

[0005] This invention proposes a device for measuring the frequency characteristics of a fiber optic coupler for a fiber optic gyroscope, comprising a light source, a Y-waveguide, a detector, a signal detection and processing circuit, a light source driver, and a host computer. The host computer controls the light source driver to provide current to the light source. The light signal output by the light source passes through the fiber optic coupler under test and enters the detector to generate an electrical signal. The electrical signal is processed by the signal detection and processing circuit. The signal terminal of the signal detection and processing circuit is connected to the pin of the Y-waveguide, and the periodic feedback signal of the signal terminal is output to the Y-waveguide, making the Y-waveguide an excitation source. By applying a frequency-sweeping periodic signal to the Y-waveguide as an excitation source, the change in the optical signal output through the fiber optic coupler is detected to obtain the measurement result of the frequency characteristics of the fiber optic coupler for the fiber optic gyroscope.

[0006] Furthermore, the signal detection and processing circuit generates a frequency-sweeping periodic square wave signal with an amplitude of 4.0V, a duty cycle of 50%, a frequency sweep from 100KHz to 300KHz, a sweep step of 0.05KHz, and a duration of 100ms for each frequency point.

[0007] Furthermore, after the square wave signal is applied to the electrodes of the Y waveguide, it forms an excitation source, and the Y waveguide will generate a parasitic interference signal of the same frequency.

[0008] Furthermore, the interference signal is coupled into the fiber optic coupler, modulating the optical signal transmitted in the fiber optic coupler, thereby allowing the detector to detect the modulated optical signal.

[0009] Furthermore, the signal detection and processing circuit collects the signal output by the detector and forms a graphic display of the device.

[0010] Furthermore, the fiber coupler to be tested is placed parallel to the Y waveguide, with a distance of 5 mm between them.

[0011] Furthermore, the host computer is connected to the light source driver, and the host computer controls the light source driver to generate an output current, forming the driving current and temperature control current required by the light source.

[0012] Furthermore, the host computer is connected to the signal detection and processing circuit, and performs calculations and graphical displays on the received data by sending reset and communication commands to the signal detection and processing circuit.

[0013] This invention provides a frequency characteristic measurement device for fiber optic couplers used in fiber optic gyroscopes. During the manufacturing process of a fiber optic gyroscope, the frequency characteristics of the fiber optic coupler are tested before assembly. This ensures that no frequency characteristic problems will occur after the fiber optic coupler is assembled into the fiber optic gyroscope, solving the problem of lacking means to test the frequency characteristics of fiber optic couplers. It eliminates resource waste and quality risks caused by trial and error and multiple rework, improves the first-pass yield of fiber optic gyroscope manufacturing, saves manufacturing costs, and increases production efficiency. Attached Figure Description

[0014] Figure 1 This is a system configuration diagram of a fiber optic coupler frequency characteristic measurement device for a fiber optic gyroscope according to the present invention;

[0015] Figure 2 This is a schematic diagram of the periodic square wave signal of the present invention.

[0016] Figure 3 This is a schematic diagram of the sweep time and frequency of the present invention.

[0017] Figure 4 This is a typical measurement result of the frequency characteristics of a certain device. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention will be further described below with reference to the embodiments.

[0019] Currently, interferometric fiber optic gyroscopes primarily employ a digital closed-loop detection scheme, consisting of a detection circuit and a sensitive optical path. The sensitive optical path utilizes a mixed-polarity optical path design, mainly comprising an SLD light source, fiber coupler, Y-waveguide, PIN-FET detector, and polarization-maintaining fiber ring. The detection circuit detects and processes the electrical signal output from the PIN-FET detector, generating a closed-loop feedback signal, which is applied to the electrodes of the Y-waveguide. The electro-optic effect of the Y-waveguide then modulates the optical signal, achieving feedback modulation of the sensitive optical path. The closed-loop feedback signal is a periodic signal with a frequency consistent with the eigenfrequency of the fiber optic gyroscope, primarily determined by the length of the polarization-maintaining fiber ring. When this periodic signal is applied to the Y-waveguide electrodes, the lithium niobate material used to manufacture the Y-waveguide exhibits piezoelectric, acousto-optic, and photoelastic effects in addition to the electro-optic effect, thus generating periodic parasitic interference signals. In practical fiber optic gyroscope design, fiber optic couplers, Y-waveguides, and polarization-maintaining fiber loops are usually assembled together as components. At this time, the periodic interference signal generated by the Y-waveguide will affect the fiber optic coupler and affect the accuracy of the fiber optic gyroscope.

[0020] This invention designs a fiber optic coupler frequency characteristic measurement device for fiber optic gyroscopes. It is used to test the frequency characteristics of the fiber optic coupler in advance during the manufacturing process of fiber optic gyroscopes, ensuring that frequency characteristic problems will not occur after the fiber optic coupler is assembled into the fiber optic gyroscope. This solves the problem of lacking fiber optic coupler frequency characteristic testing methods, eliminates resource waste and quality risks caused by trial and error and multiple rework, and improves the first-pass yield of fiber optic gyroscope manufacturing.

[0021] like Figure 1As shown, a fiber optic coupler frequency characteristic measurement device for fiber optic gyroscopes mainly consists of a light source, a Y-waveguide, a detector, a signal detection and processing circuit, a light source driver, and a host computer. The host computer is connected to the light source driver, controlling its output current. The light source driver is connected to the light source, providing driving current and temperature control current. The fiber optic coupler under test is placed parallel to the Y-waveguide, with a spacing of approximately 5mm. One input end of the fiber optic coupler is connected to the light source, and the other output end is connected to the detector. The optical signal output by the light source passes through the fiber optic coupler under test, enters the detector for reception, and is converted into an electrical signal. The signal detection and processing circuit is connected to the detector, sampling and processing the electrical signal output by the detector. The signals V+ and V- of the signal detection and processing circuit are connected to pins ③ and ② of the Y-waveguide, respectively, outputting the generated periodic feedback signal to the Y-waveguide, making the Y-waveguide the excitation source. The host computer is connected to the signal detection and processing circuit, sending reset and communication commands to the signal detection and processing circuit, and performing calculations and graphical display on the received data.

[0022] In this system, the host computer connects and controls all components. Through its connection to the light source driver, the host computer can control the driver's output current, thus providing the necessary drive current and temperature control current to the light source. Simultaneously, the connection between the driver and the light source ensures its normal operation. The fiber optic coupler under test (DUT) is placed parallel to the Y-waveguide, with a spacing of approximately 5 mm between them. One input end of the DUT is connected to the light source, and the other output end is connected to the detector. Thus, the optical signal output from the light source, after passing through the DUT, can enter the detector for reception and conversion into an electrical signal. This design enables the DUT to transmit the optical signal to the detector. The signal detection and processing circuit is connected to the detector, sampling and processing the electrical signal output from the detector. The signals V+ and V- of the signal detection and processing circuit are connected to pins ③ and ② of the Y-waveguide, respectively. The generated periodic feedback signal can then be output to the Y-waveguide, making it an excitation source. The host computer is also connected to the signal detection and processing circuit. By sending reset and communication commands to the signal detection and processing circuit, the host computer can perform calculations and graphical displays on the received data. In this way, the host computer can control and monitor the entire system. Through the connection between the host computer and the light source driver, the fiber optic coupler under test, and the signal detection and processing circuit, we can achieve the control, transmission, and detection of optical signals. This system has high reliability and stability, and can meet the needs of various optical experiments and applications.

[0023] After one input end of the fiber optic coupler under test (FT-D) is connected to the light source, the optical signal output from the light source enters the FT-D. The FT-D has a beam splitting function; a portion of the light is output through the FT-D's output end and enters the detector. The signal detection and processing circuit generates a frequency-sweeping periodic square wave signal with an amplitude of 4.0V and a duty cycle of 50% (e.g., ...). Figure 2 As shown), the square wave signal frequency is swept from 100kHz to 300kHz, with a sweep step size of 0.05kHz, and the duration of each frequency point is 100ms (e.g.). Figure 3 (As shown). After the square wave signal is applied to the electrodes of the Y-waveguide, the Y-waveguide generates a parasitic interference signal of the same frequency, which couples into the fiber coupler, modulating the optical signal transmitted in the fiber coupler. The modulated optical signal can be detected by the detector. The signal detection and processing circuit acquires the signal output from the detector and performs detection using a relevant detection algorithm; the host computer performs calculations and displays the data detected by the signal detection and processing circuit graphically. A typical figure of the measurement results of a certain device is shown below. Figure 4 As shown, the fiber optic coupler output is abnormal when the sweep frequency is 180KHz.

[0024] After a square wave signal is applied to the electrodes of the Y-waveguide, a parasitic interference signal at the same frequency is generated in the Y-waveguide and coupled into the fiber optic coupler. This modulates the optical signal transmitted in the fiber optic coupler. After detection by a detector, the modulated optical signal can be further analyzed and processed. The signal detection and processing circuit acquires the signal output from the detector and uses relevant detection algorithms for detection. These algorithms help extract useful information and perform analysis and judgment. Finally, the host computer performs calculations and graphical displays on the data detected by the signal detection and processing circuit, allowing users to intuitively understand the operating status and transmission performance of the fiber optic coupler. Through this workflow, we can perform comprehensive testing and evaluation of the fiber optic coupler under test. This helps ensure the normal operation of the fiber optic coupler and provides reliable optical signal transmission and modulation functions.

[0025] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0026] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device for measuring the frequency characteristics of an optical fiber coupler for an optical fiber gyroscope, characterized in that: The system includes a light source, a Y-waveguide, a detector, a signal detection and processing circuit, a light source driver, and a host computer. The host computer controls the light source driver to provide current to the light source. The light signal output by the light source passes through the fiber optic coupler to be detected and enters the detector to generate an electrical signal. The electrical signal is processed by the signal detection and processing circuit. The signal terminal of the signal detection and processing circuit is connected to the pin of the Y-waveguide. The periodic feedback signal of the signal terminal is output to the Y-waveguide, making the Y-waveguide an excitation source. By applying a frequency-sweeping periodic signal to the Y-waveguide as an excitation source, the changes in the light signal output through the fiber optic coupler are detected to obtain the frequency characteristic measurement results of the fiber optic coupler for fiber optic gyroscopes. The signal detection and processing circuit generates a frequency-sweeping periodic square wave signal. After the square wave signal is applied to the electrodes of the Y-waveguide, it forms an excitation source. The Y-waveguide will generate parasitic interference signals of the same frequency.

2. The fiber optic coupler frequency response measurement device for fiber optic gyroscopes as described in claim 1, characterized in that: The square wave signal has an amplitude of 4.0V and a duty cycle of 50%. The square wave signal frequency is swept from 100KHz to 300KHz with a sweep step size of 0.05KHz and a duration of 100ms for each frequency point.

3. The fiber optic coupler frequency characteristic measurement device for fiber optic gyroscopes as described in claim 2, characterized in that: The interference signal is coupled into the fiber optic coupler, modulating the optical signal transmitted in the fiber optic coupler, so that the detector can detect the modulated optical signal.

4. The fiber optic coupler frequency response measurement device for fiber optic gyroscopes as described in claim 3, characterized in that: The signal detection and processing circuit collects the signal output by the detector and then forms a graphic display of the device.

5. The fiber optic coupler frequency response measurement device for fiber optic gyroscopes as described in claim 4, characterized in that: The fiber coupler to be tested is placed parallel to the Y waveguide, with a distance of 5 mm between them.

6. The fiber optic coupler frequency response measurement device for fiber optic gyroscopes as described in claim 1, characterized in that: The host computer is connected to the light source driver, and the host computer controls the light source driver to generate output current, forming the driving current and temperature control current required by the light source.

7. The fiber optic coupler frequency response measurement device for fiber optic gyroscopes as described in claim 1, characterized in that: The host computer is connected to the signal detection and processing circuit. By sending reset and communication commands to the signal detection and processing circuit, it performs calculations and displays graphics on the received data.

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