Resonant fiber-optic gyroscope driven by low-noise wide-spectrum light source and working method of resonant fiber-optic gyroscope

Abstract

The invention belongs to the field of optical gyroscopes. The invention particularly relates to a resonant fiber-optic gyroscope driven by a low-noise wide-spectrum light source and a working method of the resonant fiber-optic gyroscope. The input end of the working light source ASE and the input end of the photoelectric detector PD are connected to two left side ports of the coupler C1 respectively, two right side ports of the coupler C1 are connected with left side ports of the single polarization phase modulators SPPM1 and SPPM2 respectively, and right side ports of the single polarization phase modulators SPPM1 and SPPM2 are connected with two ports of the fiber ring resonator FRR respectively. According to the invention, while the loss of the sensing unit is fundamentally reduced by using the reflective optical fiber resonant cavity, the influence of relative intensity noise and shot noise on the performance of the gyroscope is further reduced by using an optical cancellation method, and the signal-to-noise ratio of the gyroscope is finally improved.

Description

Technical Field

[0001] The present invention belongs to the field of optical gyroscopes; specifically, it relates to a resonant fiber optic gyroscope driven by a low-noise wide-spectrum light source and its working method. Background Art

[0002] A gyroscope is an inertial device used to measure the rotational angular velocity of a carrier relative to inertial space. With the further development of unmanned systems, there is an urgent need for gyroscopes with high precision, small size, and low power consumption.

[0003] Among existing optical gyroscopes, the relatively mature ones are laser gyroscopes and interferometric fiber optic gyroscopes. However, laser gyroscopes have numerous internal components and high costs; interferometric fiber optic gyroscopes require a fiber optic loop of several kilometers to achieve navigation-level performance and are difficult to miniaturize. In contrast, resonant fiber optic gyroscopes fully combine the advantages of laser gyroscopes and interferometric fiber optic gyroscopes. They can utilize the characteristic of multiple-round transmission of light waves in a fiber optic ring resonator to enhance the Sagnac effect, thereby achieving navigation-level accuracy with a fiber length of dozens to hundreds of meters and avoiding complex mechanical components. Moreover, the shorter fiber length reduces the influence of the Shupe effect while reducing costs. Resonant fiber optic gyroscopes are of all-solid-state structure, conforming to the development trend of miniaturization of inertial devices and having potential advantages in achieving high precision, small size, and low cost.

[0004] The performance of existing resonant fiber optic gyroscopes driven by wide-spectrum light sources is fundamentally restricted by relative intensity noise and shot noise, making it difficult to further improve their accuracy. In addition, their sensitive units generally adopt a transmissive resonator structure with a double coupler, resulting in high losses in the sensitive units. Summary of the Invention

[0005] The present invention provides a resonant fiber optic gyroscope driven by a low-noise wide-spectrum light source and its working method. By using a reflective fiber optic resonator, the loss of the sensitive unit is fundamentally reduced, and at the same time, the optical cancellation method is used to break through the limit of relative intensity noise and shot noise, realizing low noise in the resonant fiber optic gyroscope.

[0006] The present invention is realized through the following technical solutions:

[0007] A resonant fiber optic gyroscope driven by a low-noise wide-spectrum light source, the gyroscope includes a working light source ASE, a photodetector PD, an optical coupler C1, a single-polarization phase modulator SPPM1, a single-polarization phase modulator SPPM2, and a fiber optic resonator FRR including an optical coupler C2;

[0008] The input ends of the working light source ASE and the photodetector PD are both connected to two left ports of the optical coupler C1. Two right ports of the optical coupler C1 are respectively connected to the left port of the single-polarization phase modulator SPPM1 and the left port of the single-polarization phase modulator SPPM2. The right ports of the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2 are respectively connected to two ports of the fiber optic resonator FRR including the optical coupler C2.

[0009] Further, the working light source ASE provides broadband laser light.

[0010] The photodetector PD is used to detect the combined laser light after passing through the optical coupler, the single-polarization phase modulator, and the fiber optic resonator.

[0011] The optical coupler C1 is used to split the broadband laser light emitted by the working light source ASE and to combine the light after passing through the fiber optic resonator.

[0012] The single-polarization phase modulator SPPM1 is used to make the modulated light beam enter the fiber optic loop resonator FRR in the counterclockwise direction.

[0013] The single-polarization phase modulator SPPM2 is used to make the modulated light beam enter the fiber optic loop resonator FRR in the clockwise direction.

[0014] The fiber optic resonator FRR is used to make the light beam propagate multiple turns to enhance the rotation angular velocity signal.

[0015] The optical coupler C2 in the fiber optic resonator FRR is used to couple light waves into and out of the fiber optic resonator FRR.

[0016] Further, the working light source ASE, the photodetector PD, the optical coupler C1, the single-polarization phase modulator SPPM1, the single-polarization phase modulator SPPM2, and the fiber optic resonator FRR including the optical coupler C2 are all components with polarization-maintaining characteristics and have the same working wavelength.

[0017] Further, the working light source ASE is a broadband laser; the fiber optic resonator FRR including the optical coupler C2 is a reflective fiber optic resonator.

[0018] A working method for driving a resonant fiber optic gyro with a low-noise broadband light source, the working method is as follows:

[0019] The broadband laser light output by the working light source ASE is split into two beams of light after passing through the optical coupler C1, and the two beams of light respectively reach the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2.

[0020] The light beam modulated by the single-polarization phase modulator SPPM1 passes through a 90° fusion splice and enters the fiber optic ring resonator FRR containing the optical coupler C2 in the counterclockwise direction. The light beam passing through the single-polarization phase modulator SPPM2 enters the fiber optic ring resonator FRR containing the optical coupler C2 in the clockwise direction;

[0021] The light beams propagating in the clockwise and counterclockwise directions inside the fiber optic ring resonator FRR output after propagating periodically for several turns; at this time, the light beam propagating in the clockwise direction passes through the optical coupler C2, then passes through the 90° fusion splice and reaches the single-polarization phase modulator SPPM1, while the light beam propagating in the counterclockwise direction reaches the single-polarization phase modulator SPPM2 after passing through C2;

[0022] After passing through the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2, the two light beams reach the optical coupler C1 again; finally, the combined light beam passing through the optical coupler C1 reaches the photodetector PD for detection.

[0023] Furthermore, the optical field expressions of the light beams propagating in the clockwise and counterclockwise directions after phase modulation are:

[0024]

[0025] Among them, P in , S(f), and f are the optical power, normalized power spectral density, and the center frequency of the ASE light source respectively; α1, α2, and γ are the additional losses of the single-polarization phase modulator SPPM1, the single-polarization phase modulator SPPM2, and the coupler C2 respectively; φ(t) is the modulation signal applied by the phase modulator; τ is the time required for the light wave to propagate one week in the FRR; θ, k C are the polarization crosstalk and coupling ratio of the coupler C2 respectively; represents the phase difference between the through and cross ports of the couplers C1 and C2; α L represents the total loss of the optical fiber, Δψ = 2πΔf sag τ represents the Sagnac phase shift generated due to the external rotation along the axis of the resonator.

[0026] Furthermore,

[0027] Δf sag = DΩ / (n eff λ)

[0028] Among them, Δf sag represents the Sagnac frequency shift, D represents the diameter of the fiber optic resonator FRR; n eff represents the refractive index of the optical fiber; λ represents the center wavelength of the ASE light source; Ω represents the angular velocity along the axis direction.

[0029] Further, the light intensity I detected by the photodetector PD PD is expressed as:

[0030] I PD = ∫(E CW + E CCW ) Τ (E CW + E CCW ) * df (4)

[0031] A resonant fiber optic gyroscope driven by a low-noise broadband light source as described above is applied to the field of microsatellite attitude control.

[0032] A resonant fiber optic gyroscope driven by a low-noise broadband light source as described above is applied to the field of UAV autonomous navigation.

[0033] The beneficial effects of the present invention are as follows:

[0034] The present invention uses a reflective fiber optic resonator to reduce the loss of light transmission in the sensing unit, improve the quality factor, and thus enhance the ultimate sensitivity of the gyroscope; while the optical cancellation method effectively reduces the optical power detected by the photodetector on the premise of keeping the slope of the gyroscope demodulation curve unchanged, thereby reducing the noise power, breaking through the original relative intensity noise and shot noise limit, and further improving the angular random walk of the gyroscope. The method used in the present invention is completely optical, with a simple structure and no need for additional signal processing and compensation circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic structural diagram of the present invention.

[0036] Figure 2 is a transmission curve graph of the gyroscope before and after the present invention uses the optical cancellation method.

[0037] Figure 3 is a theoretical improvement effect diagram of the relative intensity noise and shot noise after the present invention uses the optical cancellation method.

[0038] Figure 4 is the experimental result of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.

[0040] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their groups.

[0041] It should also be understood that the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. As used in the specification of this application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0042] The following combines the appendix of the specification of this application Figures 1-4 , and clearly and completely describes the technical solutions in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0043] Many specific details are set forth in the following description to facilitate a thorough understanding of this application, but this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of this application. Therefore, this application is not limited by the specific embodiments disclosed below.

[0044] Embodiment 1

[0045] This embodiment provides a low-noise wide-spectrum light source-driven resonant fiber optic gyroscope, which includes a working light source ASE, a photodetector PD, an optical coupler C1, a single-polarization phase modulator SPPM1, a single-polarization phase modulator SPPM2, and a fiber optic resonator FRR including an optical coupler C2;

[0046] The input ends of the working light source ASE and the photodetector PD are both connected to the two left ports of the optical coupler C1. The two right ports of the optical coupler C1 are respectively connected to the left port of the single-polarization phase modulator SPPM1 and the left port of the single-polarization phase modulator SPPM2. The right ports of the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2 are respectively connected to the two ports of the fiber optic resonator FRR including the optical coupler C2.

[0047] Further, the working light source ASE provides wide-spectrum laser light;

[0048] The photodetector PD is used to detect the combined laser beam after passing through an optical coupler, a single-polarization phase modulator, and an optical fiber resonator;

[0049] The optical coupler C1 is used to split the broadband laser beam emitted by the working light source ASE and to combine the light beam after passing through the optical fiber resonator;

[0050] The single-polarization phase modulator SPPM1 is used to make the modulated light beam enter the fiber loop resonator FRR in the counterclockwise direction;

[0051] The single-polarization phase modulator SPPM2 is used to make the modulated light beam enter the fiber loop resonator FRR in the clockwise direction;

[0052] The optical fiber resonator FRR is used to make the light beam propagate multiple turns to enhance the rotation angular velocity signal;

[0053] The optical coupler C2 in the optical fiber resonator FRR is used to couple the light wave into and out of the optical fiber resonator FRR.

[0054] Furthermore, the working light source ASE, the photodetector PD, the optical coupler C1, the single-polarization phase modulator SPPM1, the single-polarization phase modulator SPPM2, and the optical fiber resonator FRR including the optical coupler C2 are all components with polarization-maintaining characteristics and have the same working wavelength. For example, they are all 1550 nm.

[0055] Furthermore, the working light source ASE is a broadband laser, the spectral linewidth is greater than 30 nm, and the power is greater than 10 mW; the optical fiber resonator FRR including the optical coupler C2 is a reflective optical fiber resonator with a diameter of 10 cm and a length of 107 m.

[0056] Embodiment 2

[0057] This embodiment provides a working method for driving a resonant fiber optic gyroscope with a low-noise broadband light source. The working method is as follows:

[0058] The broadband laser beam output by the working light source ASE is split into two beams of light after passing through the 3dB optical coupler C1, and the two beams of light respectively reach the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2;

[0059] The light beam modulated by the single-polarization phase modulator SPPM1 passes through a 90° fusion joint and enters the fiber loop resonator FRR including the optical coupler C2 in the counterclockwise direction, and the light beam passing through the single-polarization phase modulator SPPM2 enters the fiber loop resonator FRR including the optical coupler C2 in the clockwise direction;

[0060] The light beams propagating clockwise and counterclockwise inside the fiber ring resonator (FRR) output after propagating several cycles periodically; at this time, the light beam propagating clockwise passes through the optical coupler C2, and then reaches the single-polarization phase modulator SPPM1 through a 90° fusion splice, while the light beam propagating counterclockwise reaches the single-polarization phase modulator SPPM2 after passing through C2;

[0061] After passing through the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2, the two light beams reach the 3dB optical coupler C1 again; finally, the combined light beam after passing through the 3dB optical coupler C1 reaches the photodetector PD for detection.

[0062] Furthermore, the optical field expressions of the light beams propagating clockwise and counterclockwise after phase modulation are as follows:

[0063]

[0064] Among them, P in , S(f), and f are the optical power, the normalized power spectral density, and the center frequency of the ASE light source respectively; α1, α2, and γ are the additional losses of the single-polarization phase modulator SPPM1, the single-polarization phase modulator SPPM2, and the coupler C2 respectively; φ(t) is the modulation signal applied by the phase modulator; τ is the time required for the light wave to propagate one week in the FRR

[0065] transmission; θ, k C are the polarization crosstalk and the coupling ratio of the coupler C2 respectively; represents the phase difference between the through-port and the cross-port of the couplers C1 and C2; α L represents the total loss of the optical fiber, Δψ = 2πΔf sag τ represents the Sagnac phase shift generated due to the external rotation along the axis of the resonator;

[0066] Δf sag = DΩ / (n eff λ)

[0067] Among them, Δf sag represents the Sagnac frequency shift, D represents the diameter of the fiber resonator FRR; n eff represents the refractive index of the optical fiber; λ represents the center wavelength of the ASE light source; Ω represents the angular velocity along the axis direction.

[0068] Furthermore, the light intensity I detected by the photodetector PD PD can be expressed as:

[0069] I PD = ∫(E CW + E CCW ) Τ (ECW +E CCW ) * df (4)

[0070] According to Equations (1) to (4), when the phase difference between the input end and the cross end of coupler C1 is π / 2, at Δf sag = 0

[0071] nearby, the transmission curve changes from a resonance peak to a resonance valley as Figure 2 shown. Therefore, after adopting the optical cancellation method and the reflective resonator, the slope of the demodulation curve is not affected while the interference light intensity is significantly reduced, and its sensitivity is improved as Figure 3 、 4 shown.

[0072] Furthermore, for a resonant fiber optic gyro driven by a broadband light source, under the limitation of relative intensity noise and shot noise, its ultimate accuracy can be expressed as:

[0073]

[0074] where I out represents the interference light intensity, R PD is the responsivity of the detector, R f is the transimpedance gain of the detector, and e is the electron charge. R(f m ) represents the relative intensity noise amplitude at the modulation frequency, and K d represents the slope of the demodulation curve.

[0075] Figure 1 : This scheme uses an all-optical method to implement a resonant fiber optic gyro driven by a low-noise broadband light source, and does not require an additional signal processing compensation circuit, having the advantages of simple structure, low cost, and high accuracy.

[0076] Figure 2 : After adopting the optical cancellation method, the transmission curve of the gyro changes from a Lorentz peak shape to a Lorentz valley shape. When the gyro is stationary, the light intensity detected by the PD is 0, indicating that the intensity of the polarization-coupled optical wave introduced by coupler C2 is 0, and no additional intensity noise is introduced to the gyro, demonstrating that the optical cancellation method can reduce the influence of C2 polarization crosstalk. Moreover, the optical cancellation method will significantly reduce the optical power received by the PD, thereby reducing the noise of the gyro.

[0077] Figure 3: Figure (a) shows the improvement effect of the angular random walk of the gyroscope limited by relative intensity noise with the change of modulation frequency under different modulation coefficients. It can be seen that the proposed method improves the angular random walk limited by relative intensity noise, especially at low frequencies, and the improvement effect is more than 20 times. Figure (b) shows the improvement effect of the angular random walk of the gyroscope limited by shot noise with the change of modulation frequency under different modulation coefficients. It can be seen that the proposed method improves the angular random walk limited by shot noise, and the improvement effect can reach more than 5 times at low frequencies.

[0078] Figure 4 : The proposed scheme was experimentally verified, and the experimental results show that the improvement effect of the angular random walk of the gyroscope is 7.5 dB.

[0079] Embodiment 3

[0080] The low-noise wide-spectrum light source-driven resonant fiber optic gyroscope according to Embodiment 1 is applied to the field of small satellite attitude control.

[0081] Embodiment 4

[0082] The low-noise wide-spectrum light source-driven resonant fiber optic gyroscope according to Embodiment 1 is applied to the field of UAV autonomous navigation.

Claims

1. A low-noise wide-spectrum light source-driven resonant fiber optic gyroscope, characterized in that, The gyroscope includes a working light source ASE, a photodetector PD, an optical coupler C1, a single-polarization phase modulator SPPM1, a single-polarization phase modulator SPPM2, and an optical fiber resonator FRR including an optical coupler C2; The input ends of the working light source ASE and the photodetector PD are both connected to two left ports of the optical coupler C1. The two right ports of the optical coupler C1 are respectively connected to the left port of the single-polarization phase modulator SPPM1 and the left port of the single-polarization phase modulator SPPM2. The right ports of the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2 are respectively connected to two ports of the optical fiber resonator FRR including the optical coupler C2.

2. The gyroscope according to claim 1, characterized in that, The working light source ASE provides broadband laser; The photodetector PD is used to detect the combined laser beam after passing through the optical coupler, the single-polarization phase modulator, and the optical fiber resonator; The optical coupler C1 is used to split the broadband laser emitted by the working light source ASE and to combine the light beam after passing through the optical fiber resonator; The single-polarization phase modulator SPPM1 is used to make the modulated light beam enter the optical fiber ring resonator FRR in the counterclockwise direction; The single-polarization phase modulator SPPM2 is used to make the modulated light beam enter the optical fiber ring resonator FRR in the clockwise direction; The optical fiber resonator FRR is used to make the light beam propagate multiple circles to enhance the rotation angular velocity signal; The optical coupler C2 in the optical fiber resonator FRR is used to couple light waves into and out of the optical fiber resonator FRR.

3. The gyroscope according to claim 1, wherein The working light source ASE, the photodetector PD, the optical coupler C1, the single-polarization phase modulator SPPM1, the single-polarization phase modulator SPPM2, and the optical fiber resonator FRR including the optical coupler C2 are all elements with polarization-maintaining characteristics and have the same working wavelength.

4. The gyroscope according to claim 1, wherein The working light source ASE is a broadband laser; the optical fiber resonator FRR including the optical coupler C2 is a reflective optical fiber resonator.

5. A working method for driving a resonant fiber optic gyroscope with a low-noise wide-spectrum light source, characterized in that The working method is as follows: The broadband laser output by the working light source ASE is split into two beams of light after passing through the optical coupler C1, and the two beams of light respectively reach the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2; The light beam modulated by the single-polarization phase modulator SPPM1 passes through a 90° fusion joint and enters the optical fiber ring resonator FRR including the optical coupler C2 in the counterclockwise direction, and the light beam passing through the single-polarization phase modulator SPPM2 enters the optical fiber ring resonator FRR including the optical coupler C2 in the clockwise direction; The light beams propagating in the clockwise and counterclockwise directions inside the optical fiber ring resonator FRR are output after propagating periodically for several circles; at this time, the light beam propagating in the clockwise direction passes through the optical coupler C2, then passes through a 90° fusion joint and reaches the single-polarization phase modulator SPPM1, and the light beam propagating in the counterclockwise direction reaches the single-polarization phase modulator SPPM2 after passing through C2; After passing through the single-polarization phase modulator SPPM1 and the single-polarization phase modulator SPPM2, the two beams of light reach the optical coupler C1 again; finally, the combined light after being combined by the optical coupler C1 reaches the photodetector PD for detection.

6. The working method according to claim 5, wherein, For the light beams propagating in the clockwise and counterclockwise directions, after passing through phase modulation, their optical field expressions are: where P in , S(f), and f are the optical power, the normalized power spectral density, and the center frequency of the ASE light source, respectively; α1, α2, and γ are the additional losses of the single-polarization phase modulator SPPM1, the single-polarization phase modulator SPPM2, and the coupler C2, respectively; φ(t) is the modulation signal applied by the phase modulator; τ is the time required for the light wave to travel one round in the FRR; θ, k C are the polarization crosstalk and the coupling ratio of the coupler C2, respectively; denotes the phase difference between the through-port and the cross-port of the couplers C1 and C2; α L denotes the total loss of the optical fiber, Δψ = 2πΔf sag τ represents the Sagnac phase shift generated due to the external rotation along the axis of the resonator.

7. The working method according to claim 6, characterized in that Δf sag = DΩ / (n eff λ) where, Δf sag represents the Sagnac frequency shift, D represents the diameter of the fiber optic resonator FRR; n eff represents the refractive index of the optical fiber; λ represents the central wavelength of the ASE light source; Ω represents the angular velocity along the axial direction.

8. The working method according to claim 7, characterized in that, The light intensity I detected by the photodetector PD PD is expressed as: I PD = ∫(E CW + E CCW ) Τ (E CW + E CCW ) * df (4).

9. A low-noise wide-spectrum light source driving a resonant fiber optic gyroscope according to any one of claims 1-4 is applied to the field of micro-satellite attitude control.

10. A low-noise wide-spectrum light source driving a resonant fiber optic gyroscope according to any one of claims 1-4 is applied to the field of unmanned aerial vehicle autonomous navigation.

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