Low noise angular rate sensor based on squeezed state light field injection

Abstract

The application provides a low-noise angular rate sensor based on a squeezed light field injection, wherein a laser light source is used to generate a squeezed light field, a coherent light field and a local light field through an optical path structure; the squeezed light field and the coherent light field are coupled to form a mixed light field, and then a Sagnac effect is generated in a corresponding optical path structure, so that a light field carrying rotation speed and squeezed angle offset information is formed; the local light field is used for balanced homodyne detection together with the light field, and mixed information in the form of an electric signal is obtained; the mixed information is output to a rotation speed information and a squeezed angle control signal through a squeezed angle matching system; and the squeezed angle control signal is used for controlling a squeezed angle of the squeezed light field. The squeezed light field is injected into a vacuum end of a fiber optic gyroscope coupler, so that the limit of shot noise can be broken, the performance of the fiber optic gyroscope is optimized, and the squeezed angle can be matched with the working state of the fiber optic gyroscope in real time through a squeezed angle adjusting system, so that the fiber optic gyroscope can output a low-noise signal in real time during working, and the precision of the fiber optic gyroscope is further improved.

Description

Technical Field

[0001] This invention relates to the field of angular rate sensor technology, specifically to a low-noise angular rate sensor based on compressed state optical field injection. Background Technology

[0002] A fiber optic gyroscope is a high-precision angular rate sensor that utilizes the Sagnac interference effect and enhances interference efficiency through multi-layered fiber winding. It can measure minute angular rates and is widely used in navigation and positioning, aircraft attitude control, and flight guidance.

[0003] Fiber optic gyroscopes offer high precision and require no rotating components; however, as optical interferometric instruments, their ultimate accuracy is limited by the shot noise limit, with a phase measurement limit of Δφ ≥ 1 / √N, where N is the number of photons involved in the measurement. Although the shot noise limit accuracy can be improved by increasing the number of probe photons, various backscattering noises exist in optical fibers, thus preventing arbitrary increases in the number of photons to improve the fiber optic gyroscope's accuracy.

[0004] A squeezed-state optical field is a non-classical optical field that redistributes the noise components of the optical field through a nonlinear parametric transformation process, achieving the effect of reducing one component and increasing another. Injecting a squeezed-state optical field into the vacuum end of an interferometer can improve the interferometer's ultimate precision to the quantum limit: Δφ ≥ 1 / N, thereby enhancing the interferometer's ultimate precision. The paper "Demonstration of a quantum-enhanced fiber Sagnac interferometer, Opt. Lett. 35, 1665 (2010)" first proposed using squeezed-state optical field injection to improve the precision of fiber optic gyroscopes. However, it is worth noting that the noise distribution of the squeezed-state optical field is related to the operating state of the injected interferometer. If the compression angle is not matched with the operating state of the fiber optic gyroscope, the noise of the inverse compression component will affect the quantum enhancement effect of the squeezed light, and may even cause the fiber optic gyroscope to operate in an inverse compression state, amplifying the noise. The operating state of the Sagnac interferometer changes in real time during the operation of the fiber optic gyroscope, and the compression angle needs to be matched with it in real time to maintain a good quantum enhancement effect.

[0005] A fiber optic gyroscope is a high-precision angular rate sensor based on the Sagnac interference effect. It enhances interference efficiency by using multi-layered wound fiber optic coils, enabling precise measurement of minute angular rates. It is widely used in navigation and positioning, aircraft attitude control, and flight guidance.

[0006] This type of angular rate sensor has advantages such as high accuracy and no mechanical rotating parts. However, as an optical interferometer, its ultimate accuracy is limited by the shot noise limit, that is, the minimum uncertainty of the measured phase satisfies Δφ ≥ 1 / √N, where N represents the number of photons participating in the interference process. Theoretically, accuracy can be improved by increasing the number of photons, but due to various backscattering noises in the optical fiber, performance cannot be improved indefinitely by increasing the light intensity.

[0007] Compressed optical fields are a type of nonclassical optical field that can redistribute noise components through nonlinear parametric processes, thereby compressing one noise component and amplifying another. Injecting this type of optical field into the vacuum input port of an interferometer can improve the measurement accuracy to the Heisenberg limit, i.e., Δφ ≥ 1 / N, significantly better than traditional fiber optic gyroscopes. In the paper "Demonstration of a quantum-enhanced fiber Sagnac interferometer, Opt. Lett. 35, 1665 (2010)," researchers first proposed injecting compressed light into a fiber Sagnac interferometer to improve its accuracy.

[0008] However, the noise distribution characteristics of the compressed optical field are closely related to the operating state of the interferometer. If the compression angle fails to match the actual operating point of the fiber optic gyroscope in real time, the additional noise introduced by its anti-compression component will weaken or even completely cancel the quantum enhancement effect, leading to a decrease in the actual performance of the interferometer. Since the Sagnac phase of the fiber optic gyroscope changes in real time during operation, the compression angle must be adjusted and matched in real time to achieve stable and effective quantum enhancement. Summary of the Invention

[0009] To address the limitations in improving the ultimate accuracy of fiber optic gyroscopes under classical optical fields, and the issue that the compression angle mismatch with the gyroscope's operating state affects the enhancement effect in practical applications, this invention proposes a low-noise angular rate sensor (i.e., a fiber optic gyroscope) based on compressed-state optical field injection. By injecting the compressed-state optical field into the vacuum input port of the fiber optic gyroscope coupler, the ultimate measurement accuracy of the interferometer is effectively improved, thereby significantly enhancing the performance of the fiber optic gyroscope. Simultaneously, this invention employs a compression angle matching system based on a two-state square wave modulation open-loop gyroscope architecture to achieve real-time tracking of the fiber optic gyroscope's operating state and dynamic matching of the compression angle, ensuring the stability of the quantum enhancement effect in practical operation.

[0010] The technical solution of this invention is as follows:

[0011] A low-noise angular rate sensor based on compressed state light field injection includes a laser source, a compressed light field generation component, a coherent state light field generation component, a local light field generation component, a Sagnac effect generation component, a balanced zero-beat detection system, and a compressed angle matching system.

[0012] The continuous single-frequency laser generated by the laser source enters the compressed light field generating component, the coherent light field generating component, and the local light field generating component through the optical path, generating a compressed light field, a coherent light field, and a local light field, respectively. The mixed light field formed by the coupling of the compressed light field and the coherent light field enters the Sagnac effect generating component to generate the Sagnac effect, forming a light field carrying rotational speed and compression angle offset information. This light field, together with the local light field, is injected into the balanced zero-beat detection system to obtain mixed information in the form of an electrical signal, which is then input into the compression angle matching system.

[0013] The compression angle matching system includes a rotational speed information generation branch, a compression angle control signal generation branch, and a signal generator. The mixed information first filters out the compression angle scanning signal in the rotational speed information generation branch, and then demodulates it with the square wave signal generated by the signal generator to obtain the rotational speed information. The mixed information filters out the rotational speed information in the compression angle control signal generation branch, and then mixes it with the sine wave signal generated by the signal generator and removes noise to obtain the compression angle control signal.

[0014] The compression angle matching system outputs the rotation speed information, the compression angle control signal, the square wave signal, and the sine wave signal; the square wave signal is input to the Sagnac effect generation component to apply step wave modulation to the mixed optical field so that the fiber optic gyroscope's operating point is set to π / 2; the compression angle control signal is input to the compression optical field generation component to control the compression angle of the compressed light; the compression angle control signal and the sine wave signal are superimposed and then input to the local optical field generation component to adjust the relative phase of the local optical field.

[0015] A further preferred embodiment is that the frequency f of the square wave signal m Based on the intrinsic frequency values ​​of the two-state modulation of the optical fiber ring square wave; the frequency f of the sinusoidal signal. c Greater than f m .

[0016] In a further preferred embodiment, the mixed information enters the compression angle matching system, and after passing through a preamplifier, it is split into two paths: one path enters the speed information generation branch, and the other path enters the compression angle control signal generation branch. In the speed information generation branch, the mixed information first passes through a bandpass filter to filter out the high-frequency compression angle scanning signal, and then is connected to a lock-in amplifier together with the square wave signal generated by the first signal generator for demodulation to obtain the speed information. In the compression angle control signal generation branch, the mixed information first passes through a high-pass filter to filter out the speed information, and is mixed with the sine wave signal generated by the second signal generator in a mixer. The generated signal is then denoised by a low-pass filter to retain the compression angle offset information, and then passes through a PID control circuit to generate the compression angle control signal.

[0017] In a further preferred embodiment, the laser source is a continuous single-frequency laser source. The light emitted by the laser source passes through a first mode cleaner to filter out high-order noise, and then passes through a first half-wave plate and a first polarization coupler. After passing through the first polarization coupler, the beam is split into two paths at a certain ratio. One path enters the compressed light field generating component, and the other path is split into two paths again at a certain ratio by a beam splitter. One path enters the coherent state light field generating component, and the other path enters the local light field generating component.

[0018] A further preferred embodiment involves changing the ratio of the light field intensity of the injected compressed light field generating component and the local light field generating component by rotating the angle of the first half-wave plate; the transmission and reflectivity of the beam splitter is set to 1:1.

[0019] In a further preferred embodiment, the compressed optical field generating component includes a frequency doubling cavity, a second-mode cleaner, a first phase modulator, a first optical isolator, and a nonlinear parametric amplifier. The frequency doubling cavity converts continuous single-frequency laser light into pump light, which is then filtered out for higher-order noise by the second-mode cleaner. After the compression angle of the compressed light is adjusted by the first phase modulator, it is injected into the nonlinear parametric amplifier after passing through the first optical isolator. The nonlinear parametric amplifier performs parametric down-conversion, and the pump light generates a compressed optical field. The first phase modulator controls the compression angle of the compressed light according to the compression angle control signal.

[0020] In a further preferred embodiment, the coherent optical field generating component includes a second half-wave plate and a third optical isolator. One path of light after passing through the beam splitter passes through the second half-wave plate to change the polarization state of the optical field and aligns with the polarization-maintaining fiber to maintain the optical axis as a coherent optical field.

[0021] In a further preferred embodiment, the local light field generating component includes a first reflecting mirror and a piezoelectric ceramic reflecting mirror. The other light after passing through the beam splitter is first reflected by the first reflecting mirror, and then the phase is adjusted by the piezoelectric ceramic reflecting mirror to become the local light field. The piezoelectric ceramic reflecting mirror adjusts the phase according to the superposition signal of the compression angle control signal and the sine wave signal.

[0022] In a further preferred embodiment, the mixed optical field formed by the coupling of the compressed optical field and the coherent optical field enters the Sagnac effect generating component to generate the Sagnac effect; the Sagnac effect generating component includes an optical fiber ring, a second phase modulator, a coupler, a dichroic mirror, a second optical isolator, a first optical fiber coupler, a third optical isolator, and a second optical fiber coupler; the compressed optical field generated by the compressed optical field generating component, after the pump light is filtered out by the dichroic mirror, enters the 2×2 coupler after passing through the second optical isolator and the first optical fiber coupler; the coherent optical field generated by the coherent optical field generating component passes through the second optical isolator and the first optical fiber coupler. After the three optical isolators and the second fiber coupler, the light enters the 2×2 coupler; the second phase modulator is connected in series in the fiber loop and also connected to the 2×2 coupler; the compressed optical field and the coherent optical field entering from the 2×2 coupler form a mixed optical field, which generates the Sagnac effect in the fiber loop and adjusts the initial operating phase of the fiber optic gyroscope through the second phase modulator. The optical field generated in the fiber loop, carrying the rotation speed and compression angle offset information, is injected into the balanced zero-beat detection system through the reflection port of the third optical isolator; wherein the second phase modulator adjusts the initial operating phase of the fiber optic gyroscope according to the square wave signal.

[0023] In a further preferred embodiment, the balanced zero-beat detection system includes a third half-wave plate, a fourth half-wave plate, a second polarization coupler, a first photodetector, a second photodetector, and a subtractor. The local light field generated by the local light field generating component enters the second polarization coupler after passing through the third half-wave plate. The light field carrying rotational speed and compression angle offset information generated by the Sagnac effect generating component enters the second polarization coupler after passing through the second mirror and the fourth half-wave plate. The local light field and the light field carrying rotational speed and compression angle offset information are mixed in the second polarization coupler. After local light field amplification and balanced zero-beat detection, they are split into two paths, which are then photoelectrically converted by the first and second photodetectors, respectively. The results are then processed in the subtractor to obtain mixed electrical signal information, which is then input into the compression angle matching system.

[0024] Beneficial effects

[0025] The present invention has the following advantages:

[0026] 1. This invention injects a compressed optical field into the vacuum end of the fiber optic gyroscope coupler, which can break through the shot noise limit and optimize the performance of the fiber optic gyroscope.

[0027] 2. To address the problem of noise amplification caused by the mismatch between the compression angle of the compressed optical field and the working state of the fiber optic gyroscope during operation, this invention proposes a compression angle adjustment system. This system enables the compression angle to match the working state of the fiber optic gyroscope in real time, allowing the fiber optic gyroscope to output a low-noise signal in real time during operation, thereby further improving the accuracy of the fiber optic gyroscope.

[0028] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0030] Figure 1 This is a schematic diagram of the connection of a fiber optic gyroscope instrument;

[0031] Figure 2 This is a schematic diagram of the compression angle adjustment system;

[0032] Figure 3 This is a schematic diagram of the fiber optic gyroscope testing process;

[0033] Figure 4 A schematic diagram illustrating the process for adjusting the compression angle and the phase of the local optical field.

[0034] Figure 1 In the middle: Laser source 1, first mode cleaner 2, first half-wave plate 3, first polarization coupler 4, frequency doubling cavity 5, second mode cleaner 6, first phase modulator 7, first optical isolator 8, nonlinear parametric amplifier 9, dichroic mirror 10, second optical isolator 11, first fiber coupler 12, 2×2 coupler 13, fiber ring 14, second fiber coupler 15, third optical isolator 16, second half-wave plate 17, beam splitter 18, first reflector 19, piezoelectric ceramic reflector 20, third half-wave plate 21, second reflector 22, fourth half-wave plate 23, first photodetector 24, second polarization coupler 25, second photodetector 26, subtractor 27, second phase modulator 28.

[0035] Figure 2 In the middle: lock-in amplifier 111, bandpass filter 112, preamplifier 113, high-pass filter 114, mixer 115, low-pass filter 116, proportional-integral-derivative control circuit 117, first signal generator 118, second signal generator 119. Detailed Implementation

[0036] To address the limitations in improving the accuracy of fiber optic gyroscopes under classical optical fields, and the problem that the compression angle of compressed optical fields affects the enhancement effect in practical applications due to the mismatch between the compression angle and the working state of the fiber optic gyroscope, this invention proposes a low-noise angular rate sensor based on compressed optical field injection, including a laser source, a compressed optical field generation component, a coherent optical field generation component, a local optical field generation component, a Sagnac effect generation component, a balanced zero-beat detection system, and a compression angle matching system.

[0037] The continuous single-frequency laser generated by the laser source enters the compressed light field generating component, the coherent light field generating component, and the local light field generating component through the optical path, generating a compressed light field, a coherent light field, and a local light field, respectively. The mixed light field formed by the coupling of the compressed light field and the coherent light field enters the Sagnac effect generating component to generate the Sagnac effect, forming a light field carrying rotational speed and compression angle offset information. This light field, together with the local light field, is injected into the balanced zero-beat detection system to obtain mixed information in the form of an electrical signal, which is then input into the compression angle matching system.

[0038] The compression angle matching system includes a rotation speed information generation branch, a compression angle control signal generation branch, and a signal generator. The mixed information is first filtered out of the compression angle scanning signal in the rotation speed information generation branch, and then demodulated with a square wave signal generated by the signal generator to obtain the rotation speed information. The mixed information is then filtered out of the rotation speed information in the compression angle control signal generation branch, mixed with a sine wave signal generated by the signal generator, and denoised to obtain the compression angle control signal. The compression angle matching system outputs the rotation speed information, the compression angle control signal, the square wave signal, and the sine wave signal. The square wave signal is input to the Sagnac effect generation component, applying step-wave modulation to the mixed optical field to set the fiber optic gyroscope's operating point to π / 2. The compression angle control signal is input to the compression optical field generation component to control the compression angle of the compressed light. The compression angle control signal is superimposed with the sine wave signal and input to the local optical field generation component to adjust the relative phase of the local optical field. Under constant fiber loop angular velocity, this allows scanning the noise levels of each noise component of the compressed optical field. Finally, the compression angle is matched with the fiber optic gyroscope through the compression angle matching system.

[0039] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] like Figure 1 As shown, in this embodiment, the laser source is a 1550nm continuous single-frequency laser source 1. The light emitted by the laser source passes through a first mode cleaner 2 to filter high-order noise, and then through a first half-wave plate 3 and a first polarization coupler 4. After passing through the first polarization coupler 4, the beam is split into two paths at a certain ratio. One path enters the compressed light field generating component, and the other path is split into two paths again at a certain ratio by a beam splitter 18. One path enters the coherent state light field generating component, and the other path enters the local light field generating component. In this embodiment, the ratio of the light field intensity injected into the compressed light field generating component and the local light field generating component is changed by rotating the angle of the first half-wave plate 3, while the transmittance and reflectance of the beam splitter 18 are set to 1:1.

[0041] The compressed optical field generating component includes a frequency doubling cavity 5, a second mode cleaner 6, a first phase modulator 7, a first optical isolator 8, and a nonlinear parametric amplifier 9. The frequency doubling cavity 5 converts 1550nm continuous single-frequency laser light into 775nm pump light. After passing through the second mode cleaner 6 to filter out high-order noise, the compression angle of the compressed light is adjusted by the first phase modulator 7, and then injected into the nonlinear parametric amplifier 9 after passing through the first optical isolator 8. After passing through the nonlinear parametric amplifier 9, parametric down-conversion occurs, and the 775nm pump light generates a 1550nm compressed optical field.

[0042] The coherent optical field generating component includes a second half-wave plate 17 and a third optical isolator 16. One path of light after passing through the beam splitter 18 passes through the second half-wave plate 17 to change the polarization state of the optical field and aligns with the polarization-maintaining fiber to maintain the optical axis as a coherent optical field.

[0043] The local light field generating component includes a first reflector 19 and a piezoelectric ceramic reflector 20. The other light after passing through the beam splitter 18 is first reflected by the first reflector 19, and then the phase is adjusted by the piezoelectric ceramic reflector 20 to become the local light field.

[0044] The mixed optical field formed by the coupling of the compressed optical field and the coherent optical field enters the Sagnac effect generating component to generate the Sagnac effect. The Sagnac effect generating component includes an optical fiber ring 14, a second phase modulator 28, a coupler 13, a dichroic mirror 10, a second optical isolator 11, a first optical fiber coupler 12, a third optical isolator 16, and a second optical fiber coupler 15. The 1550nm compressed optical field generated by the compressed optical field generating component, after the pump light is filtered out by the dichroic mirror 10, enters the 2×2 coupler 13 after passing through the second optical isolator 11 and the first optical fiber coupler 12. The coherent optical field generated by the coherent optical field generating component enters the 2×2 coupler 13 after passing through the third optical isolator 16 and the second optical fiber coupler 15. The second phase modulator 28, which is connected in series in the optical fiber ring 14, is also connected to the 2×2 coupler 13. The compressed optical field and the coherent optical field entering from the 2×2 coupler 13 form a mixed optical field, generating the Sagnac effect in the fiber optic loop. This effect is then used to adjust the initial operating phase of the fiber optic gyroscope via the second phase modulator 28. The optical field generated in the fiber optic loop, carrying information about the rotational speed and compression angle offset, is injected into the balanced zero-beat detection system through the reflection port of the third optical isolator 16. In this embodiment, the fiber optic loop 14 is wound with a 500m long polarization-maintaining fiber with a center wavelength of 1550nm.

[0045] The balanced zero-beat detection system includes a third half-wave plate 21, a fourth half-wave plate 23, a second polarization coupler 25, a first photodetector 24, a second photodetector 26, and a subtractor 27. The local light field generated by the local light field generating component enters the second polarization coupler 25 after passing through the third half-wave plate 21. The light field carrying rotational speed and compression angle offset information generated by the Sagnac effect generating component enters the second polarization coupler 25 after passing through the second reflector 22 and the fourth half-wave plate 23. The local light field and the light field carrying rotational speed and compression angle offset information are mixed in the second polarization coupler 25. After local light field amplification and balanced zero-beat detection, the mixture is split into two paths. These paths are then photoelectrically converted by the first photodetector 24 and the second photodetector 26, respectively. The results are then processed in the subtractor 27 to obtain mixed electrical signal information, which is then input into the compression angle matching system.

[0046] like Figure 2 As shown, the compression angle matching system includes a rotational speed information generation branch, a compression angle control signal generation branch, a first signal generator 118, and a second signal generator 119; the first signal generator 118 generates a signal with a frequency of f. m The square wave, the second signal generator 119 generates a frequency of f c A high-frequency sine wave, where the square wave frequency f m Based on the value of the intrinsic frequency c / 2nl of the two-state modulation of the square wave in fiber ring 14, where c is the speed of light, n is the refractive index of the fiber, and l is the length of fiber ring 14, the required square wave frequency f is... mThe intrinsic frequency c / 2nl of the square wave two-state modulation of fiber ring 14 is close to that of fiber ring 14. Since the length of fiber ring 14 in this embodiment is 500m, f is approximately taken as f. m =200kHz, while the frequency of a high-frequency sine wave is f c Greater than f m More than 100 times, to ensure that the high-frequency compressed angle scanning signal can be filtered out by the bandpass filter 112 to prevent interference with the fiber optic gyroscope output signal. Therefore, in this embodiment, f is taken as... c =50MHz.

[0047] After the mixed information enters the compression angle matching system, it is split into two paths by the preamplifier 113. One path enters the speed information generation branch, and the other path enters the compression angle control signal generation branch. In the speed information generation branch, the mixed information first passes through the bandpass filter 112 to filter out the high-frequency compression angle scanning signal. Then, it is combined with the square wave signal generated by the first signal generator 118 and fed into the lock-in amplifier 111 for demodulation to obtain the speed information. In this embodiment, the passband of the bandpass filter 112 is 0.1f. m ~10f m The mixed information is first filtered by a high-pass filter 114 to remove rotational speed information in the compression angle control signal generation branch, and then mixed with a sinusoidal signal generated by the second signal generator 119 in a mixer 115. The resulting signal carries high-frequency noise and low-frequency compression angle offset information. After passing through a low-pass filter 116 to remove the high-frequency noise and retaining the compression angle offset information, the signal is then processed by a PID control circuit 117 to generate the compression angle control signal. In this embodiment, the pass frequency of the high-pass filter 114 is 0.1f. c The cutoff frequency of the low-pass filter 116 is 10f. m .

[0048] The compression angle matching system outputs the rotational speed information, the compression angle control signal, the square wave signal, and the sine wave signal. The square wave signal is input to the second phase modulator 28 in the Sagnac effect generation component to apply step wave modulation to the mixed optical field, setting the fiber optic gyroscope's operating point to π / 2. The compression angle control signal is input to the first phase modulator 7 in the compressed optical field generation component to control the compression angle of the compressed light. Since the compression angle control signal is a DC signal, it is superimposed with the sine wave signal and input to the piezoelectric ceramic reflector 20 in the local optical field generation component to adjust the relative phase of the local optical field. Under the condition of constant fiber ring angular velocity, it can scan the noise level of each noise component of the compressed optical field. Finally, the compression angle is matched with the fiber optic gyroscope through the compression angle matching system.

[0049] In this embodiment, the nonlinear parametric amplifier 9 in the compressed light field generation component consists of a nonlinear crystal and a resonant cavity. The nonlinear crystal employs type I matching to adjust the incident angle of the pump light, ensuring that the pump light, signal light, and idle light meet the matching conditions. The nonlinear crystal is placed in a temperature-controlled furnace with a temperature control accuracy of no less than 0.01℃, ensuring stable parametric conversion. Furthermore, in this embodiment, the mode cleaner consists of input / output mirrors and a piezoelectric ceramic concave mirror.

[0050] The principle of this invention is given below:

[0051] According to Heisenberg's uncertainty principle, the two noise components of the optical field satisfy the following relationship:

[0052]

[0053] The above equation defines the minimum uncertainty of the orthogonal components of the optical field. In a classical optical field, coherent states have minimum orthogonal uncertainty components:

[0054]

[0055] Due to the limitations imposed by Heisenberg's uncertainty principle, the accuracy of classical optical field measurements cannot exceed the shot noise limit. Therefore, we introduce a squeezed optical field, and the uncertainty of the orthogonal components of the squeezed optical field is expressed as:

[0056]

[0057] In the formula, r represents the range of values ​​for the compression factor: , The compression angle is controlled by the relative phase of the pump light and the signal light.

[0058] After the light field passes through the fiber optic gyroscope, it is incident on the balanced zero-beat detection system. The noise output of the detection system is given by the following formula:

[0059]

[0060] In the formula This represents the phase difference generated by the fiber optic gyroscope along the forward and reverse optical paths at this time. The relative phase of the local optical field is considered. It can be seen that matching the compression angle, the phase difference between the forward and reverse light of the fiber optic gyroscope, and the relative phase of the local optical field of the balanced zero-beat detector are necessary to minimize output noise. Therefore, this invention employs the compression angle adjustment system proposed in this invention, which allows the compression angle to be matched in real-time with the operating state of the fiber optic gyroscope, enabling the fiber optic gyroscope to output a low-noise signal in real-time during operation, thereby further improving the accuracy of the fiber optic gyroscope.

[0061] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A low-noise angular rate sensor based on squeezed state light field injection, characterized by: The application relates to an optical fiber angular rate sensor, which comprises a laser light source, a compressed light field generating assembly, a coherent state light field generating assembly, a local light field generating assembly, a Sagnac effect generating assembly, a balanced homodyne detection system and a compressed angle matching system; and the angular rate sensor is an optical fiber gyroscope. Continuous single-frequency laser generated by the laser light source enters the compressed light field generating assembly, the coherent state light field generating assembly and the local light field generating assembly through an optical path to generate compressed light field, coherent state light field and local light field respectively; the mixed light field formed by coupling of the compressed light field and the coherent state light field enters the Sagnac effect generating assembly to generate Sagnac effect, forms light field carrying rotation speed and compressed angle offset information, is injected into the balanced homodyne detection system together with the local light field, obtains mixed information in the form of an electric signal, and is input into the compressed angle matching system. The compressed angle matching system comprises a rotation speed information generating branch, a compressed angle control signal generating branch and a signal generator; the mixed information is filtered to remove the compressed angle scanning signal in the rotation speed information generating branch, and then is demodulated with a square wave signal generated by the signal generator to obtain rotation speed information; the mixed information is filtered to remove the rotation speed information in the compressed angle control signal generating branch, is mixed with a sine wave signal generated by the signal generator, and is de-noised to obtain the compressed angle control signal. The compression angle matching system outputs the rotation speed information, the compression angle control signal, the square wave signal and the sine wave signal; the square wave signal is input into the Sagnac effect generating component, and the step wave modulation is applied to the mixed light field to set the working point of the fiber optic gyroscope at ; the compression angle control signal is input into the compressed light field generating component to control the compression angle of the compressed light; and the compression angle control signal and the sine wave signal are superimposed and input into the local light field generating component to adjust the relative phase of the local light field.

2. The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: Frequency of the square wave signal Frequency of the square wave signal Greater than .

3. The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: The mixed information enters the compressed angle matching system, is divided into two paths through a preamplifier, one path enters the rotation speed information generating branch, and the other path enters the compressed angle control signal generating branch; the mixed information is filtered to remove the high-frequency compressed angle scanning signal through a band-pass filter in the rotation speed information generating branch, and then is demodulated with a square wave signal generated by a first signal generator to obtain rotation speed information; the mixed information is filtered to remove the rotation speed information through a high-pass filter in the compressed angle control signal generating branch, is mixed with a sine wave signal generated by a second signal generator in a frequency mixer, the generated signal is de-noised through a low-pass filter to retain the compressed angle offset information, and then the compressed angle control signal is generated through a PID control circuit.

4. The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: The laser light source adopts a continuous single-frequency laser light source, the light emitted by the laser light source is filtered to remove high-order noise through a first mode cleaner, and then passes through a first half-wave plate and a first polarization coupler; the light beam is divided into two paths through the first polarization coupler according to a certain proportion, one light enters the compressed light field generating assembly, and the other light passes through a beam splitter and is divided into two paths again according to a certain proportion, one light enters the coherent state light field generating assembly, and the other light enters the local light field generating assembly.

5. The low-noise angular rate sensor based on squeezed state light field injection of claim 4, wherein: The intensity ratio of the light fields injected into the compressed light field generating assembly and the local light field generating assembly is changed by rotating the first half-wave plate; and the transmission reflectivity of the beam splitter is set to 1:

1.

6. The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: The compression light field generating assembly comprises a frequency doubling cavity, a second mode cleaner, a first phase modulator, a first optical isolator, and a nonlinear parametric amplifier; the frequency doubling cavity converts continuous single-frequency laser into pump light, then the high-order noise is filtered out by the second mode cleaner, the compression light compression angle is adjusted by the first phase modulator, then the pump light is injected into the nonlinear parametric amplifier after passing through the first optical isolator, parametric down-conversion occurs in the nonlinear parametric amplifier, and the pump light generates the compression light field, wherein the first phase modulator controls the compression light compression angle according to the compression angle control signal.

7. The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: The coherent state light field generating assembly comprises a second half-wave plate and a third optical isolator; one light passing through the beam splitter passes through the second half-wave plate to change the polarization state of the light field, and the polarization maintaining optical fiber polarization maintaining optical axis is aligned as the coherent state light field. 8.The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: The local light field generating assembly comprises a first mirror and a piezoelectric ceramic mirror; the other light passing through the beam splitter is reflected by the first mirror first, then adjusted in phase by the piezoelectric ceramic mirror, and finally used as the local light field; wherein the piezoelectric ceramic mirror adjusts the phase according to the superposition signal of the compression angle control signal and the sinusoidal signal. 9.The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: The mixed optical field formed by the coupling of the compressed optical field and the coherent optical field enters the Sagnac effect generating component to generate the Sagnac effect. The Sagnac effect generating component includes an optical fiber ring, a second phase modulator, a coupler, a dichroic mirror, a second optical isolator, a first optical fiber coupler, a third optical isolator, and a second optical fiber coupler. The compressed optical field generated by the compressed optical field generating component, after the pump light is filtered out by the dichroic mirror, enters the Sagnac effect after passing through the second optical isolator and the first optical fiber coupler. Coupler; the coherent optical field generated by the coherent optical field generating component enters the optical field after passing through the third optical isolator and the second fiber coupler. Coupler; a second phase modulator is also connected after being inserted into the fiber optic loop. Coupler; from The compressed optical field and the coherent optical field entering through the coupler form a mixed optical field, which generates the Sagnac effect in the fiber optic loop. The initial working phase of the fiber optic gyroscope is adjusted by the second phase modulator. The optical field carrying the rotation speed and compression angle offset information generated in the fiber optic loop is injected into the balanced zero-beat detection system through the reflection port of the third optical isolator. The second phase modulator adjusts the initial working phase of the fiber optic gyroscope according to the square wave signal.

10. The low-noise angular rate sensor based on squeezed state light field injection of claim 1, wherein: The balanced homodyne detection system comprises a third half-wave plate, a fourth half-wave plate, a second polarization coupler, a first photodetector, a second photodetector, and a subtracter; the local light field generated by the local light field generating assembly enters the second polarization coupler after passing through the third half-wave plate, the light field carrying the rotation speed and compression angle offset information generated by the Sagnac effect generating assembly enters the second polarization coupler after passing through the second mirror and the fourth half-wave plate, the local light field and the light field carrying the rotation speed and compression angle offset information are mixed in the second polarization coupler, then divided into two paths after local light field amplification and balanced homodyne detection, and then converted into electrical signals by the first photodetector and the second photodetector, respectively; the electrical signals are operated in the subtracter to obtain the electrical signal mixed information, and then input into the compression angle matching system.

Images