An optical path system with relative intensity noise suppression and an evaluation system and method thereof

Abstract

The present application belongs to the field of relative intensity noise suppression technology of fiber optic gyroscope, and particularly relates to an optical path system with relative intensity noise suppression and an evaluation system and method thereof. At the level of fiber optic gyroscope, a simple photoelectric system is established, which can verify and screen the relative intensity noise suppression optical path system with high noise suppression ratio in the whole working temperature range in advance at a small cost.

Description

Technical Field

[0001] This invention belongs to the field of relative intensity noise suppression technology for fiber optic gyroscopes, and particularly relates to an optical path system with relative intensity noise suppression, as well as its evaluation system and method. Background Technology

[0002] Fiber optic gyroscopes, as a new generation of all-solid-state inertial instruments, are based on the Sagnac principle and sense the rotational angular rate of a loaded object along its sensitive axis. The development of fiber optic gyroscopes relies not only on precise system architecture design and sophisticated signal processing technology, but also on the rapid advancements in fundamental technologies such as fiber optic communication and optical waveguides. Compared to mechanical gyroscopes, fiber optic gyroscopes possess inherent advantages such as long lifespan, light weight, low power consumption, low cost, and ease of manufacturing, making them promising for applications in defense fields such as aviation, aerospace, and marine engineering. In the aerospace industry, fiber optic gyroscopes have already replaced the previous generation of mechanical gyroscopes and are being mass-produced and installed in inertial navigation and attitude stabilization platforms for various aircraft.

[0003] Improving the isothermal accuracy of fiber optic gyroscopes across their entire operating temperature range is essential for their large-scale application. The three main noise components affecting fiber optic gyroscope accuracy are shot noise, thermal noise, and relative intensity noise. Shot noise and thermal noise can be effectively suppressed by increasing the optical power reaching the optical system terminal. However, relative intensity noise is independent of the optical power reaching the optical system terminal and requires specialized techniques to suppress its influence, making it the most critical factor limiting the improvement of fiber optic gyroscope accuracy.

[0004] In terms of relative intensity noise suppression for fiber optic gyroscopes, both domestic and international approaches mainly employ two types of technical methods: circuit-based and optical-based solutions. Companies like Honeywell in the US have adopted a circuit-based relative intensity noise suppression solution, achieving a high noise suppression ratio of ANR > 3.8. However, this circuit-based approach increases the circuit board area and product size, as well as the complexity of the circuit layout, leading to more signal crosstalk and affecting product performance stability. Furthermore, it requires modifications to the optical system, adding optical components such as fiber polarizers and photodetectors for relative intensity noise suppression, increasing the complexity of the optical system, product size, assembly difficulty, and deteriorating system stability. Therefore, it is not conducive to the mass production and application of the product. Companies like Exail in France have adopted a relative intensity noise optical path suppression scheme. Based on the traditional optical path, they added a fiber polarizer, a fiber non-equivalent power beam splitter, and a fiber optical path isolator. Although this increases the product size and installation difficulty, the advantage is that the circuit does not need any modification. In addition, by optimizing the matching of the optical signal power, spectrum, and extinction ratio of the main optical path and the reference optical path, the relative intensity noise of the optical signal at the optical path system terminal is completely self-subtracted. Theoretically, it can achieve a relative intensity noise suppression ratio of ANR→∞, so it has been widely used.

[0005] While the relative intensity noise suppression optical path scheme significantly improves the temperature control accuracy, the wavelength-dependent loss and polarization-dependent loss of the optical components in the main optical path and reference optical path are both functions of temperature. Therefore, under room temperature conditions, the optimally matched relative intensity noise suppression optical path system will experience a shift in the optical power, spectral shape, and extinction ratio of the optical signals transmitted through the main optical path and reference optical path when they converge at the end of the optical path system as the temperature changes. This results in a decrease in the noise suppression ratio in other temperature ranges, limiting the application temperature range.

[0006] Due to the unpredictable temperature correlation of the parameters of the main and reference optical path devices in each system, the noise suppression ratio temperature range of each product is different. Therefore, it is especially necessary to test and screen optical path systems that can have a high noise suppression ratio across the entire temperature range in advance.

[0007] The relative intensity noise suppression optical path system consists of a main optical path composed of a non-equivalent power fiber beam splitter, an integrated optical modulator, a fiber ring, and four melting points, and a reference optical path composed of a fiber isolator, a non-equivalent power fiber beam splitter, and two melting points. Establishing evaluation systems for wavelength-dependent loss, polarization-dependent loss, and temperature dependence for the above optical components and each melting point would require enormous hardware, software, and human resources costs. Therefore, based on existing conditions, it is more reasonable to directly establish an optoelectronic system at the fiber optic gyroscope level to evaluate the full-temperature suppression ratio of relative intensity noise. Summary of the Invention

[0008] The technical problem solved by this invention is that relative intensity noise suppression optical path schemes have a high noise suppression ratio at room temperature but a lower noise suppression ratio at other temperatures. At the fiber optic gyroscope level, a simple optoelectronic system can be established to test and screen relative intensity noise suppression optical path systems with high noise suppression ratios across the entire operating temperature range at a relatively low cost.

[0009] The technical solution of the present invention:

[0010] In a first aspect, the present invention provides an optical path system with relative intensity noise suppression. The light source of the optical path system is an erbium-doped fiber light source 100. The light source is composed of a pump source 1, a wavelength division multiplexer 2, an erbium-doped fiber 3, a reflector 4, a light source fiber isolator 5, and a fiber filter 6. The remaining optical path components are composed of a fiber polarizer 7, an equal-power fiber bundle splitter 8, a non-equal-power fiber bundle splitter 9, an optical path fiber isolator 10, an integrated optical modulator 11, a fiber ring 12, and a photodetector 13.

[0011] The optical components are connected to each other through a fusion welding process to form a complete optical path system.

[0012] Furthermore,

[0013] Pump source 1 emits a 974nm narrow-spectrum optical signal, which passes through wavelength division multiplexer 2. The 970nm to 990nm wavelength component optical signal enters the erbium-doped fiber 3 through the reflection end of wavelength division multiplexer 2, while the remaining wavelength component optical signal is dissipated into the air through wavelength division multiplexer 2.

[0014] Erbium-doped fiber 3 absorbs a 974nm optical signal and simultaneously emits a broadband optical signal of 1520nm to 1580nm in both forward and backward directions. The forward optical signal passes through mirror 4 and is reintroduced into erbium-doped fiber 3, where it is transmitted back to wavelength division multiplexer 2 along with the backward optical signal. The 1520nm to 1580nm wavelength component optical signal passes through the transmission end of wavelength division multiplexer 2 and is incident on the light source fiber isolator 5, then transmitted forward to fiber filter 6. The 1547nm to 1572nm wavelength component optical signal passes through the transmission end of fiber filter 6 and is transmitted forward to fiber polarizer 7. The 1520nm to 1547nm and 1572nm to 1580nm wavelength component optical signals pass through the reflection end of fiber filter 6 and are reintroduced into the light source fiber isolator 5, where they are dissipated into the air.

[0015] The fiber polarizer 7 takes the input optical signal from the front end, polarizes it from a low-polarization optical signal to a high-polarization optical signal, forming the initial linear polarization state, and transmits it forward to the equal-power fiber beam splitter 8. The equal-power fiber beam splitter 8 splits the optical signal into two beams of equal power. 50% of the optical signal is transmitted forward to the non-equal-power fiber beam splitter 9, and the other 50% is transmitted forward to the optical path fiber isolator 10. Then, it passes through the 90° melting point and is transmitted forward in a linear polarization state perpendicular to the polarization direction of the initial linear polarization state, returning to the non-equal-power fiber beam splitter 9.

[0016] Furthermore,

[0017] The non-equal power fiber beam splitter 9 splits the optical signal into two beams with vastly different power. A large portion is input forward to the integrated optical modulator 11, while a small portion is input backward to the optical fiber isolator 10, ultimately dissipating into the air. The integrated optical modulator 11 then splits the optical signal into two beams of equal power, which are input forward to the fiber ring 12. These two beams propagate clockwise and counterclockwise in opposite directions within the fiber ring 12, eventually converging back into the integrated optical modulator 11. The integrated optical modulator 11 outputs a reverse-polarized optical signal with the same polarization direction as the initial linearly polarized state. The linearly polarized optical signals propagate backward and return to the non-equal power fiber beam splitter 9. The two orthogonally polarized optical signals that converge at the non-equal power fiber beam splitter 9 propagate in the reverse direction and return to the equal power fiber beam splitter 8. The equal power fiber beam splitter 8 splits the optical signal into two optical signals of equal power. 50% of the optical signal propagates in the reverse direction and returns to the fiber polarizer 7 for repolarization. 25% of the optical signal propagates in the reverse direction and returns to the fiber filter 6 and the light source fiber isolator 5, and is finally dissipated into the air. The remaining 50% of the optical signal propagates in the reverse direction to the photodetector 13, and finally reaches the optical path system terminal.

[0018] Furthermore,

[0019] The optical signal is transmitted along the main optical path, passing through pump source 1, wavelength division multiplexer 2, erbium-doped fiber 3, mirror 4, erbium-doped fiber 3, wavelength division multiplexer 2, light source fiber isolator 5, fiber filter 6, fiber polarizer 7, equal power fiber bundler 8, non-equal power fiber bundler 9, integrated optical modulator 11, fiber ring 12, integrated optical modulator 11, non-equal power fiber bundler 9, equal power fiber bundler 8, and finally reaches photodetector 13;

[0020] The optical signal propagates along the reference optical path, passing successively through pump source 1, wavelength division multiplexer 2, erbium-doped fiber 3, reflector 4, erbium-doped fiber 3, wavelength division multiplexer 2, light source fiber isolator 5, fiber filter 6, fiber polarizer 7, equal-power fiber bundler 8, optical path fiber isolator 10, 90° melting point, non-equal-power fiber bundler 9, equal-power fiber bundler 8, and finally reaches photodetector 13.

[0021] Furthermore,

[0022] When the two optical signals transmitted from the main optical path and the reference optical path reach the photodetector 13, their optical power is completely equal, their spectral shape is exactly the same, and their polarization states are completely orthogonal, thus completely suppressing the relative intensity noise of the fiber optic gyroscope.

[0023] In a second aspect, the present invention provides a method for evaluating the relative intensity noise suppression effect of an optical path system, the method being used to evaluate the noise suppression effect of the optical path system, the method comprising:

[0024] Step 1: Connect pump source 1 to light source control circuit board 14. Adjust the resistance of the potentiometer on light source control circuit board 14 so that the DC voltage signal of the light signal converted to photodetector 13 is close to 2V, and ensure that the DC voltage signal of photodetector 13 is not saturated.

[0025] Step 2: Connect the integrated optical modulator 11 to the main control circuit board 15, and apply an adjustable modulation depth voltage signal to the integrated optical modulator 11 through the main control circuit board 15.

[0026] Step 3: Break the melting point between the equal power fiber splitter 8, the photodetector 13, and the optical fiber isolator 10. Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the optical power meter 17 and record the first optical signal power value.

[0027] Step 4: Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape. The spectrum should be smooth and continuous, and there should be no faulty spectra.

[0028] Step 5: Re-splice the equal power fiber splitter 8 with the optical fiber isolator 10. Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the optical power meter 17 and record the second optical power value. It should be twice the first optical power value. If the two recorded values ​​do not meet the requirements, fine-tune the modulation depth of the main control circuit board 15 and monitor the second optical power. If it meets the requirements, it is the optimal modulation depth.

[0029] Step 6: Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape again. The spectrum should still be smooth and continuous, and there should be no faulty spectral problems. This indicates that there are no obvious abnormalities in the main optical path and the reference optical path, and the polarization states of the two paths are basically perpendicular.

[0030] Step 7: Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the extinction ratio measuring instrument 19, and record the extinction ratio value of the optical signal. The extinction ratio should be close to 0.

[0031] If all the above results are met, it indicates that the optical power, spectral shape, and polarization state of the main optical path and the reference optical path are basically matched under room temperature conditions, and the accuracy of the fiber optic gyroscope is significantly improved under room temperature conditions.

[0032] Furthermore, the method also includes:

[0033] Step 8: At the photodetector end of the equal power fiber splitter 8, another equal power fiber splitter 20 is fused together. Both equal power fiber splitters are polarization-maintaining pigtails and are fused at 0° axially. The optical path system is placed in the high and low temperature test chamber 16. The two bare fibers at the output ends of the second equal power fiber splitter are extended out of the high and low temperature test chamber 16. One is connected to the fiber optic spectrometer 18 and the other is connected to the extinction ratio measuring instrument 19.

[0034] Step 9: Set up and turn on the high and low temperature test chamber, so that its temperature covers the entire working temperature range. Connect the fiber optic spectrometer 18 to the extinction ratio measuring instrument 19, and continuously collect the raw spectral data. Continuously record the extinction ratio value and plot the extinction ratio temperature change curve.

[0035] Thirdly, the present invention also provides a system for evaluating the relative intensity noise suppression effect of an optical path system, the system being used to perform the method described above, the system comprising:

[0036] Connect pump source 1 to light source control circuit board 14. By adjusting the resistance of potentiometer on light source control circuit board 14, make the DC voltage signal of the light signal converted to photodetector 13 close to 2V, and ensure that the DC voltage signal of photodetector 13 is not saturated.

[0037] The integrated optical modulator 11 is connected to the main control circuit board 15, and the main control circuit board 15 loads an adjustable modulation depth voltage signal onto the integrated optical modulator 11.

[0038] Break the melting point between the equal power fiber splitter 8, the photodetector 13, and the optical fiber isolator 10. Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the optical power meter 17 and record the first optical signal power value.

[0039] Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape. The spectrum should be smooth and continuous, and there should be no faulty spectra.

[0040] Re-fuse the equal-power fiber optic bundle splitter 8 with the optical fiber isolator 10. Insert the bare fiber at the photodetector end of the equal-power fiber optic bundle splitter 8 into the optical power meter 17 and record the second optical power value. It should be twice the first optical power value. If the two recorded values ​​do not meet the requirements, fine-tune the modulation depth of the main control circuit board 15 and monitor the second optical power. If it meets the requirements, it is the optimal modulation depth.

[0041] Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape again. The spectrum should still be smooth and continuous, and there should be no faulty spectral problems. This indicates that there are no obvious abnormalities in the main optical path and the reference optical path, and the polarization states of the two paths are basically perpendicular.

[0042] Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the extinction ratio measuring instrument 19, and record the extinction ratio value of the optical signal. The extinction ratio should be close to 0.

[0043] Furthermore,

[0044] At the photodetector end of the equal power fiber splitter 8, another equal power fiber splitter 20 is fused together. Both equal power fiber splitters are polarization-maintaining pigtails and are fused together at 0° axially. The optical path system is installed in the high and low temperature test chamber 16. The output pigtail of the second equal power splitter extends out from the high and low temperature test chamber 16, with one end connected to the fiber optic spectrometer 18 and the other end connected to the extinction ratio measuring instrument 19.

[0045] Edit the temperature curve of the high and low temperature test chamber. Set the temperature range to cover the working temperature range of the fiber optic gyroscope and turn it on. Use the software system of the fiber optic spectrometer 18 and the extinction ratio measuring instrument 19 to continuously collect the raw spectral data, continuously record the extinction ratio value and plot the extinction ratio temperature change curve.

[0046] The present invention provides an optical path system with relative intensity noise suppression capability, and a photoelectric detection system for testing the relative intensity noise suppression capability. This system is used to test and screen out optical path systems with relative intensity noise suppression capabilities for fiber optic gyroscopes that can maintain a high noise suppression ratio across the entire operating temperature range. A simple photoelectric system is built at the gyroscope level to eliminate optical path systems with relative intensity noise suppression capabilities that cannot meet the requirements of the entire operating temperature range. Attached Figure Description

[0047] Figure 1 For relative intensity noise suppression optical path system;

[0048] Figure 2 This is a relative intensity noise suppression optical path system for evaluating the room temperature noise suppression effect of an optoelectronic system;

[0049] Figure 3 This is a relative intensity noise suppression optical path system for evaluating the full-temperature noise suppression effect of an optoelectronic system. Detailed Implementation

[0050] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0051] The fiber optic gyroscope with relative intensity noise suppression function provided in the embodiments of the present invention, such as... Figure 1As shown, the light source is an erbium-doped fiber light source 100, which consists of a pump source 1, a wavelength division multiplexer 2, an erbium-doped fiber 3, a reflector 4, a light source fiber isolator 5, and a fiber filter 6. The remaining optical path components consist of a fiber polarizer 7, an equal-power fiber bundler 8, a non-equal-power fiber bundler 9, an optical path fiber isolator 10, an integrated optical modulator 11, a fiber ring 12, and a photodetector 13. These optical components are interconnected through a fusion splicing process to form a complete optical path system.

[0052] Pump source 1 emits a 974nm narrow-spectrum optical signal, which passes through wavelength division multiplexer 2. The 970nm to 990nm wavelength components pass through the reflection end of wavelength division multiplexer 2 and enter erbium-doped fiber 3. The remaining wavelength components are dissipated into the air through wavelength division multiplexer 2. Erbium-doped fiber 3 absorbs a 974nm optical signal and simultaneously emits a broadband optical signal of 1520nm to 1580nm in both forward and backward directions. The forward optical signal passes through mirror 4 and is reintroduced into erbium-doped fiber 3, where it is transmitted back to wavelength division multiplexer 2 along with the backward optical signal. The 1520nm to 1580nm wavelength component optical signal passes through the transmission end of wavelength division multiplexer 2 and is incident on the light source fiber isolator 5, then transmitted forward to fiber filter 6. The 1547nm to 1572nm wavelength component optical signal passes through the transmission end of fiber filter 6 and is transmitted forward to fiber polarizer 7. The 1520nm to 1547nm and 1572nm to 1580nm wavelength component optical signals pass through the reflection end of fiber filter 6 and are reintroduced into the light source fiber isolator 5, where they are dissipated into the air.

[0053] The fiber polarizer 7 takes the input optical signal from the low polarization degree and polarizes it into a high polarization degree optical signal, forming an initial linear polarization state. This initial linear polarization state is then transmitted forward to the equal-power fiber beam splitter 8. The equal-power fiber beam splitter 8 splits the optical signal into two beams of approximately equal power. 50% of the optical signal is transmitted forward to the non-equal-power fiber beam splitter 9, and the other 50% is transmitted forward to the optical path fiber isolator 10. The beams then pass through the 90° melting point and are transmitted forward in a linear polarization state perpendicular to the initial linear polarization state, returning to the non-equal-power fiber beam splitter 9. The non-equal-power fiber beam splitter 9 splits the optical signal into two beams of significantly different polarization. A large portion is transmitted forward to the integrated optical modulator 11, and a small portion is transmitted backward to the optical path fiber isolator 10, ultimately dissipating into the air. The integrated optical modulator 11 splits the optical signal into two beams of approximately equal power. These beams are input forward to the fiber optic ring 12, and propagate clockwise and counterclockwise towards each other within the ring, eventually converging back into the integrated optical modulator 11. The optical signal output from the integrated optical modulator 11, with a linear polarization parallel to its initial polarization direction, propagates backward back to the non-equal power fiber optic beam splitter 9. The two beams, converged at the non-equal power fiber optic beam splitter 9, with orthogonal polarization states, propagate backward back to the equal power fiber optic beam splitter 8. The equal power fiber optic beam splitter 8 splits the optical signal into two beams of approximately equal power. 50% of the optical signal propagates backward back to the fiber polarizer 7 for repolarization, 25% propagates backward back to the fiber filter 6 and the light source fiber isolator 5, ultimately dissipating into the air, and the remaining 50% propagates backward to the photodetector 13, finally reaching the optical system terminal.

[0054] The optical signal propagates along the main optical path, passing successively through pump source 1, wavelength division multiplexer 2, erbium-doped fiber 3, mirror 4, erbium-doped fiber 3, wavelength division multiplexer 2, source fiber isolator 5, fiber filter 6, fiber polarizer 7, equal-power fiber bundler 8, non-equal-power fiber bundler 9, integrated optical modulator 11, fiber ring 12, integrated optical modulator 11, non-equal-power fiber bundler 9, equal-power fiber bundler 8, and finally reaches photodetector 13. The optical signal propagates along the reference optical path, passing successively through pump source 1, wavelength division multiplexer 2, erbium-doped fiber 3, mirror 4, erbium-doped fiber 3, wavelength division multiplexer 2, source fiber isolator 5, fiber filter 6, fiber polarizer 7, equal-power fiber bundler 8, optical path fiber isolator 10, 90° melting point, non-equal-power fiber bundler 9, equal-power fiber bundler 8, and finally reaches photodetector 13. When the two optical signals transmitted from the main optical path and the reference optical path reach the photodetector 13, their optical power is completely equal, their spectral shape is exactly the same, and their polarization states are completely orthogonal, thus completely suppressing the relative intensity noise of the fiber optic gyroscope.

[0055] Based on the aforementioned optical path system, a simplified evaluation system for assessing the relative intensity noise suppression effect of the optical path system across the entire operating temperature range is established, such as... Figure 2 and Figure 3 As shown.

[0056] 1. Connect pump source 1 to light source control circuit board 14. By adjusting the resistance of the potentiometer on light source control circuit board 14, make the DC voltage signal converted from the light signal reaching photodetector 13 close to 2V, and ensure that the DC voltage signal of photodetector 13 is not saturated.

[0057] 2. Match the insertion loss of the main optical path and the reference optical path. Connect the integrated optical modulator 11 to the main control circuit board 15. Through the main control circuit board 15, apply an adjustable modulation depth voltage signal to the integrated optical modulator so that the total insertion loss of the main optical path is equal to the sum of the insertion loss of all optical devices in the main optical path and the modulation loss of the integrated optical modulator 11. The total insertion loss of the reference optical path is equal to the sum of the insertion losses of all optical devices in the reference optical path. The principle of matching the insertion loss of the two paths is that the total insertion loss of the main optical path is equal to the total insertion loss of the reference optical path.

[0058] 3. Break the fusion point between the equal-power fiber optic splitter 8 and the photodetector 13, so that the optical path system does not include the photodetector 13. Break the fusion point between the equal-power fiber optic splitter 8 and the optical path fiber optic isolator 10. Insert the bare fiber at the photodetector end of the equal-power fiber optic splitter 8 into the optical power meter 17 and record the optical signal power value. Then, insert the bare fiber at the photodetector end of the equal-power fiber optic splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape. The spectrum should be smooth and continuous, without ripple, lasing, or other faulty spectral problems. Then, re-fuse the equal-power fiber optic splitter 8 and the optical path fiber optic isolator 10. Insert the bare fiber at the photodetector end of the equal-power fiber optic splitter 8 into the optical power meter 17 and record the optical signal power value. The second recorded optical power value should be twice the first recorded optical power value. If the two recorded values ​​do not meet the requirements, fine-tune the modulation depth of the main control circuit board 15. The optimal modulation depth is when the second recorded optical power meets the requirements. Next, insert the bare fiber at the photodetector end of the equal-power fiber splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape again. The spectrum should still be smooth and continuous, without any ripples, lasing, or other spectral problems. This indicates that there are no obvious abnormalities in the main optical path and the reference optical path, and that the polarization states of the two paths are basically perpendicular. Finally, insert the bare fiber at the photodetector end of the equal-power fiber splitter 8 into the extinction ratio measuring instrument 19 and record the extinction ratio of the optical signal. The extinction ratio should be close to 0. If all the above results are met, it indicates that under room temperature conditions, the optical power, spectral shape, and polarization state of the main optical path and the reference optical path are basically matched, and the accuracy of the fiber optic gyroscope is significantly improved under room temperature conditions.

[0059] To simultaneously monitor the spectral shape and real-time changes in extinction ratio of the optical signal, another equal-power fiber optic splitter 20 is fused to the photodetector end of the equal-power fiber optic splitter 8. Both fiber optic splitters are polarization-maintaining pigtails and fused at 0° axial alignment. The optical path system is installed in the high and low temperature test chamber 16. The output pigtail of the second equal-power splitter extends from the high and low temperature test chamber 16, with one path connected to the fiber optic spectrometer 18 and the other path connected to the extinction ratio measuring instrument 19. The temperature curve of the high and low temperature test chamber is edited, and the temperature range is set to cover the operating temperature range of the fiber optic gyroscope and enabled. Using the software system built into the fiber optic spectrometer 18 and the extinction ratio measuring instrument 19, raw spectral data is continuously acquired, extinction ratio values ​​are continuously recorded, and the extinction ratio temperature change curve is plotted.

[0060] After the high and low temperature tests, the raw spectral data were imported into the edited MATLAB program, and the extinction ratio temperature curve was observed. This served two purposes: firstly, to determine whether the optical signal spectrum at the optical path system terminal was smooth and free of significant ripple and lasing throughout the entire temperature change range; and secondly, to determine whether the extinction ratio of the optical signal at the optical path terminal was close to zero throughout the entire temperature change range. If ripple or lasing exceeding 0.1 dB appears in the spectrum across the entire operating temperature range, or if the extinction ratio exceeds 2 dB, this relative intensity noise suppression optical path system is not suitable for the entire operating temperature range.

[0061] Based on the established model of spectral ripple value, extinction ratio value and relative intensity noise suppression ratio value, optical path systems with relative intensity noise suppression that do not meet the full operating temperature range can be eliminated in advance.

[0062] Based on the relative intensity noise suppression optical path system, a photoelectric system is established to evaluate the relative intensity noise suppression effect of the optical path system across the entire operating temperature range.

[0063] Step 1: Connect pump source 1 to light source control circuit board 14. Adjust the resistance of the potentiometer on light source control circuit board 14 so that the DC voltage signal of the light signal converted to photodetector 13 is close to 2V, and ensure that the DC voltage signal of photodetector 13 is not saturated (saturation voltage of DC voltage signal of photodetector 13 is -0.2V).

[0064] Step 2: Connect the integrated optical modulator 11 to the main control circuit board 15, and apply an adjustable modulation depth voltage signal to the integrated optical modulator 11 through the main control circuit board 15.

[0065] Step 3: Break the melting point between the equal power fiber splitter 8, the photodetector 13, and the optical fiber isolator 10. Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the optical power meter 17 and record the first optical signal power value.

[0066] Step 4: Insert the bare fiber at the photodetector end of the equal-power fiber splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape. The spectrum should be smooth and continuous, without any ripples, lasing, or other spectral problems.

[0067] Step 5: Re-fusion the equal power fiber splitter 8 with the optical fiber isolator 10. Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the optical power meter 17 and record the second optical power value. It should be twice the first optical power value. If the two recorded values ​​do not meet the requirements, fine-tune the modulation depth of the main control circuit board 15 and monitor the second optical power. If it meets the requirements, it is the optimal modulation depth.

[0068] Step 6: Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the fiber optic spectrometer 18 and observe the spectral shape again. The spectrum should still be smooth and continuous, without any faulty spectral problems such as ripples or lasing. This indicates that there are no obvious abnormalities in the main optical path and the reference optical path, and the polarization states of the two paths are basically perpendicular.

[0069] Step 7: Insert the bare fiber at the photodetector end of the equal power fiber splitter 8 into the extinction ratio measuring instrument 19, and record the extinction ratio value of the optical signal. The extinction ratio should be close to 0.

[0070] If all the above results are met, it indicates that the optical power, spectral shape, and polarization state of the main optical path and the reference optical path are basically matched under room temperature conditions, and the accuracy of the fiber optic gyroscope is significantly improved under room temperature conditions.

[0071] Step 8: To simultaneously monitor the real-time changes in the spectral shape and extinction ratio of the optical signal, another equal-power fiber optic splitter 20 is fused to the photodetector end of the equal-power fiber optic splitter 8. Both equal-power fiber optic splitters are polarization-maintaining pigtails and are fused at 0° to the axis. The optical path system is placed in the high and low temperature test chamber 16. The two bare fibers at the output ends of the second equal-power splitter are extended out of the high and low temperature test chamber 16, with one end connected to the fiber optic spectrometer 18 and the other end connected to the extinction ratio measuring instrument 19.

[0072] Step 9: Set up and turn on the high and low temperature test chamber, so that its temperature covers the entire working temperature range. Connect the fiber optic spectrometer 18 to the extinction ratio measuring instrument 19, and continuously collect the raw spectral data. Continuously record the extinction ratio value and plot the extinction ratio temperature change curve.

[0073] Step 10: Observe the extinction ratio temperature curve. On one hand, determine whether the optical signal spectrum at the optical path system terminal is smooth and free of obvious ripple and lasing throughout the entire temperature change range. On the other hand, determine whether the extinction ratio of the optical signal at the optical path terminal is close to zero throughout the entire temperature change range. If ripple or lasing exceeding 0.1dB appears in the spectrum across the entire operating temperature range, or if the extinction ratio exceeds 2dB, this relative intensity noise suppression optical path system is not suitable for the entire operating temperature range.

[0074] The present invention provides an optical path system with relative intensity noise suppression capability, and a photoelectric detection system for testing the relative intensity noise suppression capability. This system is used to test and screen out optical path systems with relative intensity noise suppression capabilities for fiber optic gyroscopes that can maintain a high noise suppression ratio across the entire operating temperature range. A simple photoelectric system is built at the gyroscope level to eliminate optical path systems with relative intensity noise suppression capabilities that cannot meet the requirements of the entire operating temperature range.

Claims

1. An optical path system with relative intensity noise suppression, characterized in that, The light source of the optical path system is an erbium-doped fiber light source (100). The light source consists of a pump source (1), a wavelength division multiplexer (2), an erbium-doped fiber (3), a reflector (4), a light source fiber isolator (5), and a fiber filter (6). The remaining optical path consists of a fiber polarizer (7), an equal-power fiber bundle splitter (8), a non-equal-power fiber bundle splitter (9), an optical path fiber isolator (10), an integrated optical modulator (11), a fiber ring (12), and a photodetector (13). The optical components are connected to each other through a fusion welding process to form a complete optical path system.

2. The optical path system with relative intensity noise suppression according to claim 1, characterized in that, The pump source (1) emits a 974nm narrow-spectrum optical signal. The 970nm to 990nm wavelength component optical signal passes through the wavelength division multiplexer (2) and enters the erbium-doped fiber (3) through the reflection end of the wavelength division multiplexer (2). The remaining wavelength component optical signals are dissipated into the air through the wavelength division multiplexer (2). Erbium-doped fiber (3) absorbs 974nm optical signal and simultaneously emits 1520nm~1580nm broadband optical signal in both forward and backward directions. The forward optical signal passes through mirror (4) and is reintroduced into erbium-doped fiber (3), and is transmitted back to wavelength division multiplexer (2) together with the backward optical signal. The 1520nm~1580nm wavelength component optical signal passes through the transmission end of wavelength division multiplexer (2) and is incident on the light source fiber isolator (5), and is transmitted forward to fiber filter (6). The 1547nm~1572nm wavelength component optical signal passes through the transmission end of fiber filter (6) and is transmitted forward to fiber polarizer (7). The 1520nm~1547nm and 1572nm~1580nm wavelength component optical signals pass through the reflection end of fiber filter (6) and are reintroduced into light source fiber isolator (5), and dissipated into the air. The fiber polarizer (7) takes the input optical signal from the front end, and polarizes it from a low polarization degree optical signal to a high polarization degree optical signal, forming the initial linear polarization state. It is then transmitted forward to the equal power fiber beam splitter (8). The equal power fiber beam splitter (8) splits the optical signal into two optical signals with equal power. 50% of the optical signal is transmitted forward to the non-equal power fiber beam splitter (9), and the other 50% of the optical signal is transmitted forward to the optical path fiber isolator (10). The signal then passes through the 90° melting point and is transmitted forward in a linear polarization state perpendicular to the polarization direction of the initial linear polarization state, returning to the non-equal power fiber beam splitter (9).

3. The optical path system with relative intensity noise suppression according to claim 2, characterized in that, The non-equal power fiber beam splitter (9) splits the optical signal into two beams with extremely different power. A large portion is input forward to the integrated optical modulator (11), and a small portion is input backward to the optical fiber isolator (10), and is eventually dissipated into the air. The integrated optical modulator (11) splits the optical signal into two beams of equal power, which are input forward to the fiber ring (12). The two beams are transmitted clockwise and counterclockwise in the fiber ring (12) and eventually converge back into the integrated optical modulator (11). The integrated optical modulator (11) outputs the optical signal in the reverse direction, so that the polarization direction is parallel to the initial linear polarization state. The linearly polarized state of the optical signal is transmitted backward and returns to the non-equal power fiber splitter (9). The two orthogonally polarized optical signals that converge in the non-equal power fiber splitter (9) are transmitted in reverse and return to the equal power fiber splitter (8). The equal power fiber splitter (8) splits the optical signal into two optical signals with equal power. 50% of the optical signal is transmitted in reverse and returns to the fiber polarizer (7) for repolarization. 25% of the optical signal is transmitted in reverse and returns to the fiber filter (6) and the light source fiber isolator (5), and is finally dissipated into the air. 50% of the optical signal is transmitted in reverse to the photodetector (13) and finally reaches the optical path system terminal.

4. The optical path system with relative intensity noise suppression according to claim 3, characterized in that, The optical signal is transmitted along the main optical path, passing through the pump source (1), wavelength division multiplexer (2), erbium-doped fiber (3), mirror (4), erbium-doped fiber (3), wavelength division multiplexer (2), light source fiber isolator (5), fiber filter (6), fiber polarizer (7), equal power fiber splitter (8), non-equal power fiber splitter (9), integrated optical modulator (11), fiber ring (12), integrated optical modulator (11), non-equal power fiber splitter (9), equal power fiber splitter (8), and finally reaches the photodetector (13); The optical signal is transmitted along the reference optical path, passing through the pump source (1), wavelength division multiplexer (2), erbium-doped fiber (3), mirror (4), erbium-doped fiber (3), wavelength division multiplexer (2), light source fiber isolator (5), fiber filter (6), fiber polarizer (7), equal power fiber splitter (8), optical path fiber isolator (10), 90° melting point, non-equal power fiber splitter (9), equal power fiber splitter (8), and finally reaches the photodetector (13).

5. An optical path system with relative intensity noise suppression according to claim 4, characterized in that, When the two optical signals transmitted from the main optical path and the reference optical path reach the photodetector (13), the optical power is completely equal, the spectral shape is exactly the same, and the polarization state is completely orthogonal, so the relative intensity noise of the fiber optic gyroscope is completely suppressed.

6. A method for evaluating the relative intensity noise suppression effect of an optical path system, characterized in that, The method is used to evaluate the noise suppression effect of the optical path system as described in claims 1-5, and the method includes: Step 1: Connect the pump source (1) to the light source control circuit board (14). By adjusting the resistance of the potentiometer on the light source control circuit board (14), make the DC voltage signal of the light signal converted to the photodetector (13) close to 2V, and ensure that the DC voltage signal of the photodetector (13) is not saturated. Step 2: Connect the integrated optical modulator (11) to the main control circuit board (15), and load an adjustable modulation depth voltage signal onto the integrated optical modulator (11) through the main control circuit board (15); Step 3: Break the melting point between the equal power fiber splitter (8), the photodetector (13), and the optical fiber isolator (10), insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the optical power meter (17), and record the first optical signal power value. Step 4: Insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the fiber optic spectrometer (18) and observe the spectral shape. The spectrum should be smooth and continuous, and there should be no faulty spectra. Step 5: Re-fuse the equal power fiber splitter (8) and the optical fiber isolator (10), insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the optical power meter (17), and record the second optical power value. It should be twice the first optical power value. If the two recorded values ​​do not meet the requirements, fine-tune the modulation depth of the main control circuit board (15), monitor the second optical power, and the optimal modulation depth is the one that meets the requirements. Step 6: Insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the fiber optic spectrometer (18) and observe the spectral shape again. The spectrum should still be smooth and continuous, and there should be no faulty spectral problems. This indicates that there are no obvious abnormalities in the main optical path and the reference optical path, and the polarization states of the two paths are basically perpendicular. Step 7: Insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the extinction ratio measuring instrument (19), record the extinction ratio value of the optical signal, and the extinction ratio should be close to 0; If all the above results are met, it indicates that the optical power, spectral shape, and polarization state of the main optical path and the reference optical path are basically matched under room temperature conditions, and the accuracy of the fiber optic gyroscope is significantly improved under room temperature conditions.

7. The method for evaluating the relative intensity noise suppression effect of an optical path system according to claim 6, characterized in that, The method further includes: Step 8: At the photodetector end of the equal power fiber splitter (8), another equal power fiber splitter (20) is fused together. Both equal power fiber splitters are polarization-maintaining pigtails and are fused together at 0° axially. The optical path system is placed in the high and low temperature test chamber (16). The two bare fibers at the output ends of the second equal power splitter are extended out of the high and low temperature test chamber (16). One is connected to the fiber optic spectrometer (18) and the other is connected to the extinction ratio measuring instrument (19). Step 9: Set up and turn on the high and low temperature test chamber, so that its temperature covers the entire working temperature range. Connect the fiber optic spectrometer (18) and the extinction ratio measuring instrument (19) to continuously collect the original spectral data, continuously record the extinction ratio value and draw the extinction ratio temperature change curve.

8. A system for evaluating the relative intensity noise suppression effect of an optical path system, characterized in that, The system is used to perform the method as described in any one of claims 6-7, and the system is: Connect the pump source (1) to the light source control circuit board (14). By adjusting the resistance of the potentiometer on the light source control circuit board (14), make the DC voltage signal of the light signal arriving at the photodetector (13) close to 2V, and ensure that the DC voltage signal of the photodetector (13) is not saturated. Connect the integrated optical modulator (11) to the main control circuit board (15), and load an adjustable modulation depth voltage signal onto the integrated optical modulator (11) through the main control circuit board (15); Break the melting point between the equal power fiber splitter (8), the photodetector (13), and the optical fiber isolator (10), insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the optical power meter (17), and record the first optical signal power value. Insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the fiber optic spectrometer (18) and observe the spectral shape. The spectrum should be smooth and continuous, and there should be no faulty spectra. Re-fuse the equal power fiber splitter (8) with the optical fiber isolator (10), insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the optical power meter (17), and record the second optical power value. It should be twice the first optical power value. If the two recorded values ​​do not meet the requirements, fine-tune the modulation depth of the main control circuit board (15), monitor the second optical power, and the optimal modulation depth is the one that meets the requirements. Insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the fiber optic spectrometer (18) and observe the spectral shape again. The spectrum should still be smooth and continuous, and there should be no faulty spectral problems. This indicates that there are no obvious abnormalities in the main optical path and the reference optical path, and the polarization states of the two paths are basically perpendicular. Insert the bare fiber at the photodetector end of the equal power fiber splitter (8) into the extinction ratio measuring instrument (19) and record the extinction ratio of the optical signal. The extinction ratio should be close to 0.

9. The system for evaluating the relative intensity noise suppression effect of an optical path system according to claim 8, characterized in that, At the photodetector end of the equal power fiber splitter (8), another equal power fiber splitter (20) is fused together. Both equal power fiber splitters are polarization-maintaining pigtails and are fused together at 0° axially. The optical path system is installed in the high and low temperature test chamber (16). The output pigtail of the second equal power splitter extends out from the high and low temperature test chamber (16), one of which is connected to the fiber optic spectrometer (18) and the other is connected to the extinction ratio measuring instrument (19). Edit the temperature curve of the high and low temperature test chamber, set the temperature range to cover the working temperature range of the fiber optic gyroscope and turn it on, and continuously collect the original spectral data through the software system of the fiber optic spectrometer (18) and extinction ratio measuring instrument (19), continuously record the extinction ratio value and draw the extinction ratio temperature change curve.

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