CN113587914B - Spectrum separation method for inhibiting back reflection error of resonant integrated optical gyroscope - Google Patents
Spectrum separation method for inhibiting back reflection error of resonant integrated optical gyroscope Download PDFInfo
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Abstract
The invention is thatThe invention discloses a frequency spectrum separation method for inhibiting back reflection errors of a resonant integrated optical gyroscope, which belongs to the field of resonant integrated optical gyroscopes, and comprises the steps of firstly, constructing a frequency spectrum separation detection device; the invention provides four triangular wave modulation signals which respectively modulate two light beams which are transmitted along a ring waveguide resonant cavity in a clockwise and anticlockwise direction; the two detectors respectively convert the received two beams of output light which are transmitted along the resonant cavity in the clockwise direction into electric signals; the sine wave is designed to demodulate two electric signals by demodulating the result De CW The invention provides an optimal strategy for modulating frequency design of the resonant integrated optical gyroscope, so that signal light and a back reflection spectrum are separated to inhibit the back light related error of the resonant integrated optical gyroscope.
Description
Technical Field
The invention belongs to the technical field of resonant integrated optical gyroscopes, and particularly relates to a frequency spectrum separation method for inhibiting back reflection errors of a resonant integrated optical gyroscope.
Background
The optical gyroscope based on the Sagnac effect is taken as an important component of an inertial navigation system, so that high-sensitivity measurement of the angular velocity can be realized. In particular, the resonant integrated optical gyroscope can be manufactured on a silicon chip, provides a promising solution for low-cost and miniaturized inertial navigation systems, and has the advantages of small size, full solid state, high sensitivity and the like.
In a resonant integrated optical gyroscope, light is circulated in a waveguide ring resonator to achieve high sensitivity of angular velocity measurement. However, the output light intensity of the waveguide ring resonator contains angular velocity information obtained by multi-beam interference, and is susceptible to multiple error sources. Therefore, the error suppression method is important for realizing high-precision detection of the resonant integrated optical gyroscope.
In a resonant integrated optical gyroscope, particularly, a back reflection error and a back dispersion error caused by back reflection are one of main error sources, and although the back reflection intensity is reduced by adopting an isolator and inclined polishing of the end face of a waveguide in the gyroscope, the end face of a detector is still the main source of the back reflection error because of obvious refractive index difference between the front side and the back side of the detector, and even if an antireflection film is arranged, the back reflection is difficult to be restrained.
The back-dispersion errors are caused by scattered light caused by scattering points randomly generated in the waveguide microstructure and inevitably present throughout the resonator. It can be seen that the back-reflected light, including back-reflected light and back-scattered light, propagates back along the resonator, eventually superimposing on the resonator output, affecting the demodulation of the angular velocity signal.
Therefore, research on the characteristics of the back reflection light and related errors is of great significance in improving the detection accuracy of the resonant integrated optical gyroscope. However, the correlation between the back light and the signal light is not analyzed in the frequency domain, which is very important for the precise separation of the back light and the signal light in the resonant integrated optical gyroscope.
Disclosure of Invention
Aiming at the problems of backscattering errors and back reflection errors caused by manufacturing processes and heterogeneous materials in optical elements of the resonant integrated optical gyroscope, the performance of the resonant integrated optical gyroscope is limited, and the like, the invention provides a frequency spectrum separation method for inhibiting the back light related errors so as to improve the detection precision of the resonant integrated optical gyroscope; in particular to a frequency spectrum separation method for inhibiting back reflection errors of a resonant integrated optical gyroscope.
The spectrum separation method for inhibiting the back reflection error comprises the following specific steps:
step one, constructing a spectrum separation detection device for inhibiting the correlation error of back reflection light, adding four triangular phase modulation waveforms for inhibiting the back reflection error, and modulating clockwise input light E in a ring waveguide resonant cavity in_CW And input light E in the counterclockwise direction in_CCW ；
The spectrum separation detection apparatus includes: the device comprises a laser, an isolator, an integrated optical phase modulator, a ring waveguide resonant cavity, a clockwise detector, a counterclockwise detector, a laser frequency locking controller and an angular velocity controller;
the laser is connected with an integrated optical phase modulator through an isolator, the integrated optical phase modulator is connected with a ring waveguide resonant cavity, and light beams in the clockwise direction and the anticlockwise direction are transmitted in the ring waveguide resonant cavity; the output end of the annular waveguide resonant cavity is respectively connected with a clockwise detector and a anticlockwise detector, the sum of output results of the two detectors is connected with a laser frequency locking controller, and the output is fed back to the laser to lock the frequency on the static resonant frequency of the annular waveguide resonant cavity, so that a closed loop of the resonant cavity center resonant frequency is formed; meanwhile, the difference of output results of the two detectors is connected with the angular velocity controller, and a sawtooth wave feedback signal is provided for the integrated optical phase modulator to counteract the resonance frequency difference of clockwise and anticlockwise light caused by the angular velocity signal, so that a closed loop of the angular velocity signal is formed.
The four triangular phase modulation waveforms have the same initial phase and the same amplitude V ppj (j=1, 2,3, 4) corresponds to a phase shift 2 pi of the integrated optical phase modulator and the different frequencies are f, respectively B_CW 、f B_CCW 、f S_CW And f S_CCW ；
Light generated by the laser enters the integrated optical phase modulator through the isolator and is separated into two beams of light; the two separated light beams are respectively and jointly subjected to phase modulation by four triangular phase modulation waveforms to obtain input light E in clockwise and anticlockwise directions in_CW And E is in_CCW ；
f B_CW And f S_CW The modulated wave is added to the light propagating along the clockwise direction of the annular waveguide resonant cavity for modulating the clockwise input light E in the annular waveguide resonant cavity in_CW Expressed as:
wherein E is 0 e i2πft An output electric field of the laser; m is M j (m k )(j,k＝1,2,3,4,m k E Z) m for each triangular wave phase modulation respectively k The Fourier expansion coefficients; θ CW Is the initial phase of the clockwise input light.
f B_CCW And f S_CCW The modulated wave is added on the light propagating along the anticlockwise direction of the annular waveguide resonant cavity and used for modulating the input light E of the anticlockwise direction of the annular waveguide resonant cavity in_CCW Expressed as:
θ CCW is the initial phase of the input light counter-clockwise.
In the present invention, the fundamental modulation frequency f B_CW And f B_CCW Designed to be equal, forms a fundamental carrier rejection frequency for maintaining maximum demodulation gain and minimum optical effect nonlinearity of the resonant integrated optical gyroscope.
By designing triangular wave f S_CW And f S_CCW The optimum frequency value of (2) is such that the back reflection is spectrally separated from the signal light to suppress errors caused by the back light.
In the resonant integrated optical gyroscope, the end face of the detector is a main source of back reflection error, because there is a significant refractive index difference between the front side and the rear side of the detector, and even if an antireflection film is provided, it is difficult to suppress the occurrence of back reflection.
The back-dispersion errors are caused by scattered light caused by scattering points randomly generated in the waveguide microstructure and inevitably present throughout the resonator.
The back reflection inhibited in the invention comprises back reflection light at the detector and back scattering light in the resonant cavity, which are all light back propagating along the resonant cavity, and finally are overlapped on the output of the resonant cavity, so that the demodulation result of the angular velocity signal is affected. By means of the characteristic that the back reflection and the back dispersion generated in the paths with the same light propagation direction of the annular waveguide resonant cavity have the same frequency and the phase difference is fixed, the signal light and the back reflection/back dispersion are skillfully separated on the frequency domain by a frequency spectrum separation method so as to inhibit errors generated by the back light, and simultaneously inhibit back reflection errors and back dispersion errors.
Step two, two input light E modulated by triangle phase modulation waveform in_CW And E is in_CCW Respectively adding the two light beams to the annular waveguide resonant cavity and propagating along the clockwise and counterclockwise directions to obtain clockwise output light E out_CW And counterclockwise output light E out_CCW ；
Wherein light E is output clockwise out_CW Expressed as:
wherein S is 13 (2 pi f) is from E in_CW To E out_CW Light propagation model S of (2) 23 (2 pi f) is from E in_CCW To E out_CW Is a model of light propagation;
wherein the counter-clockwise output E of the annular waveguide resonant cavity out_CCW Expressed as:
step three, clockwise detector PD CW And a counter-clockwise detector PD CCW Respectively receive clockwise output light E out_CW And counterclockwise output light E out_CCW Converting into an electrical signal;
step four, designing and f B_CW And f B_CCW The sine waves with the same frequency and phase are demodulated to obtain a demodulation result De CW ；
Outputting clockwise light E of annular waveguide resonant cavity out_CW Multiplying the demodulation sine wave and the whole period T of the demodulation sine wave to obtain a demodulation result De CW By De CW1 ,De CW21 ,De CW22 And De CW23 The composition was calculated as follows:
step five, for the demodulation result De CW Analyzing the various items to obtain the optimal frequency value f of two triangular waves for inhibiting the back error S_CW And f S_CCW Separating the signal light from the back reflection light to inhibit the back light related error of the resonant integrated optical gyroscope;
the specific analysis process is as follows:
demodulation result De CW Middle De CW1 Is a useful signal about the resonant frequency in the clockwise direction that contains angular velocity information and does not contain any back-reflection related terms.
De CW23 Only back-reflected light is contained and is negligible due to its low intensity.
De CW21 Is the direct current component of the back reflection error, and is formed by the frequency f B_CW Is generated with an intensity that is only equal to the basic delta-modulated residual component M 2 (0)，M 4 (0) And (5) correlation. When modulating voltage V ppj When the peak-to-peak value of (2) pi phase of the integrated optical phase modulator is accurately adjusted to the voltage corresponding to the 2 pi phase of the integrated optical phase modulator j (0) De for accurately eliminating back reflection errors with zero amplitude CW21 An item.
For De CW22 Model, when modulating frequency f B_CW And I out_CW The minimum value Γ=min [ | (m) of the frequency difference between the frequency components of (c) 1 +1)f B_CW +m 2 f S_CW -m 3 f B_CCW -m 4 f S_CCW |]When as large as possible, these two triangular waves f are obtained S_CW And f S_CCW Separating the signal light from the back light in the frequency domain to obtain an optimal back reflection error De CW22 Is effective in inhibiting the occurrence of a disease.
And step six, the laser frequency locking controller locks the output frequency of the laser on the static resonance frequency of the annular waveguide resonant cavity according to the sum of demodulation results of the clockwise detector and the anticlockwise detector, and the locked frequency is independent of whether the gyroscope rotates or not. Meanwhile, the angular velocity controller provides sawtooth wave feedback signals according to the demodulation result difference of the clockwise detector and the anticlockwise detector, and the sawtooth wave feedback signals are respectively and differentially added to the clockwise pointer and the anticlockwise light through the integrated optical phase modulator to generate resonance frequency movement so as to offset resonance frequency difference generated by the angular velocity.
In the present invention, four triangular phase modulated waveforms, f B_CW And f S_CW The modulated wave is added on two beams of light which are transmitted clockwise in the annular waveguide resonant cavity, f B_CCW And f S_CCW The modulated wave is applied to two beams of light propagating in the counterclockwise direction of the annular waveguide resonator. By designing triangular wave f S_CW And f S_CCW The optimum frequency value of (2) is such that the back reflection is spectrally separated from the signal light to suppress errors caused by the back light.
The invention has the advantages that:
1) The invention relates to a frequency spectrum separation method for inhibiting back reflection errors of a resonant integrated optical gyroscope, wherein the back reflection inhibited in the invention comprises back reflection light at a detector and back scattering light in a resonant cavity, and the back reflection light is light which propagates back along the resonant cavity. When the annular waveguide resonant cavity is used, by virtue of the characteristics that the back reflection and the back scattering generated in the path of the waveguide annular resonator cavity with the same light propagation direction have the same frequency and have fixed phase difference, signal light and the back reflection/back scattering are skillfully separated on the frequency domain by a frequency spectrum separation method to inhibit errors generated by the back light.
2) A frequency spectrum separation method for inhibiting back reflection errors of a resonant integrated optical gyroscope ensures maximum demodulation gain and minimum optical effect nonlinearity of the resonant integrated optical gyroscope and inhibits back reflection errors and back scattering errors.
3) A frequency spectrum separation method for inhibiting back reflection error of resonant integrated optical gyroscope is disclosed, which optimizes modulation frequency f S_CW And f S_CCW So that the modulation frequency f B_CW And I out_CW The minimum value Γ of the frequency difference between the frequency components of (a) is as large as possible to ensure that the signal light and the back light are separated in the frequency domain to obtain an optimal back reflection error De CW22 Inhibition effect of the term.
4) The frequency spectrum separation method for inhibiting the back reflection error of the resonant integrated optical gyroscope comprises the steps of performing ingenious separation on signal light and back reflection/back scattering light on a frequency domain through frequency spectrum separation by virtue of the characteristics that the generated back reflection light and back scattering light have the same frequency and a fixed phase difference in the same path of the light propagation direction of the annular waveguide resonant cavity, so as to inhibit the error generated by the back light.
Drawings
FIG. 1 is a flow chart of a method for spectrum separation of a resonant integrated optical gyroscope to suppress back reflection errors;
FIG. 2 is a schematic diagram of a spectrum separation detection device for suppressing errors associated with back reflection light according to the present invention;
fig. 3 shows the optimal modulation frequency of the spectrum separation method according to the present invention.
Fig. 4 shows experimental results of back light intensity of the spectral separation method according to the present invention.
Fig. 5 is a spectrum of a detector output signal of the spectrum separation method according to the present invention, a) a simulation diagram of a spectrum of a clockwise detector output signal, b) actual measurement spectrums of two paths of detector output signals, namely, clockwise and counterclockwise.
FIG. 6 is a graph showing the results of bias stability experiments for a resonant integrated optical gyroscope of the present invention with and without the use of spectral separation methods.
Detailed Description
Embodiments of the present invention will be described in detail and explicitly with reference to the examples and the accompanying drawings.
The invention designs a frequency spectrum separation method for inhibiting back reflection errors of a resonant integrated optical gyroscope, which is used for improving the detection precision of the resonant integrated optical gyroscope. By separating the angular velocity signal from the error associated with the back light in the frequency domain, an optimal strategy for modulating the frequency of the resonant integrated optical gyroscope is obtained, which can maximize the spectral gap of the clockwise and counterclockwise light to suppress the error associated with the back light and achieve maximum demodulation gain and minimum optical effect nonlinearity. The method for suppressing the back light related errors can greatly improve the detection precision of the resonant integrated optical gyroscope based on the photon chip, and is beneficial to the application of the resonant integrated optical gyroscope in the fields of novel micro-inertial navigation such as clustered unmanned aerial vehicles, micro-nano satellites and the like.
The spectrum separation method for inhibiting the back reflection error of the resonant integrated optical gyroscope is shown in fig. 1, and comprises the following specific steps:
step one, constructing a spectrum separation detection device for inhibiting the correlation error of back reflection light, adding four triangular phase modulation waveforms for inhibiting the back reflection error, and modulating clockwise input light E in a ring waveguide resonant cavity in_CW And input light E in the counterclockwise direction in_CCW ；
As shown in fig. 2, the spectrum separation detection apparatus includes: the device comprises a laser, an isolator, an integrated optical phase modulator, a ring waveguide resonant cavity, a clockwise detector, a counterclockwise detector, a laser frequency locking controller and an angular velocity controller;
the laser is connected with an integrated optical phase modulator through an isolator, the integrated optical phase modulator is connected with a ring waveguide resonant cavity, and light beams in the clockwise direction and the anticlockwise direction are transmitted in the ring waveguide resonant cavity; the output end of the annular waveguide resonant cavity is respectively connected with a clockwise detector and a anticlockwise detector, the sum of output results of the two detectors is connected with a laser frequency locking controller, and the output is fed back to the laser to lock the frequency on the static resonant frequency of the annular waveguide resonant cavity, so that a closed loop of the resonant cavity center resonant frequency is formed; meanwhile, the difference of output results of the two detectors is connected with the angular velocity controller, and a sawtooth wave feedback signal is provided for the integrated optical phase modulator to counteract the resonance frequency difference of clockwise and anticlockwise light caused by the angular velocity signal, so that a closed loop of the angular velocity signal is formed.
Light generated by the tunable semiconductor laser passes through the isolator, enters the integrated optical phase modulator and is separated into two beams of light; the two separated light beams are respectively and simultaneously subjected to phase modulation by four triangular phase modulation waveforms to obtain input light E in clockwise and anticlockwise directions in_CW And E is in_CCW ；
Four triangular phase modulation waveforms having the same initial phase and the same amplitude V ppj (j=1, 2,3, 4) corresponds to a phase shift 2 pi of the integrated optical phase modulator and the different frequencies are f, respectively B_CW 、f B_CCW 、f S_CW And f S_CCW 。
f B_CW And f B_CCW The modulated wave is applied to two beams of light propagating in the clockwise and counterclockwise directions of the annular waveguide resonator, respectively. In the present invention, the fundamental modulation frequency f B_CW And f B_CCW Designed to be equal, forms a fundamental carrier rejection frequency for maintaining maximum demodulation gain and minimum optical effect nonlinearity of the resonant integrated optical gyroscope.
And propose two other frequencies f S_CW And f S_CCW Is added to two beams of light propagating clockwise and counterclockwise of the annular waveguide resonant cavity respectively to suppress errors generated by the back light. In the spectrum separation method, the frequency f B_CW And f S_CW For modulating clockwise input light E in annular waveguide resonator in_CW Expressed as:
wherein E is 0 e i2πft An output electric field of the laser; m is M j (m k )(j,k＝1,2,3,4,m k E Z) m for each triangular wave phase modulation respectively k The Fourier expansion coefficients; θ CW Is the initial phase of the clockwise input light.
Frequency f B_CCW And f S_CCW Input light E for modulating counter-clockwise direction of annular waveguide resonant cavity in_CCW Expressed as:
θ CCW is the initial phase of the input light counter-clockwise.
Step two, two modulated input light E in_CW And E is in_CCW Respectively adding the two light beams to the annular waveguide resonant cavity and propagating along the clockwise and counterclockwise directions to obtain clockwise output light E out_CW And counterclockwise output light E out_CCW ；
The back-reflected light and the back-scattered light are generated by the same light frequency in the same light propagation direction of the annular waveguide resonator. If the signal light energy is separated from the back-reflected light in the frequency domain, it can naturally also be separated from the back-scattered light. Therefore, only the spectral characteristics of the back-reflected light in the resonant integrated optical gyroscope need be analyzed.
Firstly, a propagation model of light in a ring waveguide resonant cavity is established, and due to symmetry of two light beam propagation paths, input light E in a clockwise direction is considered in_CW To analyze the back reflection error model, and to consider the back reflection error, the clockwise output light E of the annular waveguide resonant cavity out_CW Expressed as:
wherein S is 13 (2 pi f) is from E in_CW To E out_CW Light propagation model S of (2) 23 (2 pi f) is from E in_CCW To E out_CW Is a model of light propagation:
S 13 (2πf)＝T CW (f)(1-γ 2 )σ 2 e i4πfτ ，
S 23 (2πf)＝e iπ γ(1-γ 2 ) 1/2 σ 4 e i8πfτ (T CCW (f)R CW (f)+T CW (f)R CCW (f))
where γ is the back reflectivity of the reflection point. T (T) CW (f) And T CCW (f) The transmission transfer functions of the annular waveguide resonant cavity are respectively clockwise and anticlockwise obtained by using multi-beam interference theory, and R CW (f) And R is CCW (f) Respectively, the transmission functions of clockwise and anticlockwise light in the annular waveguide resonant cavity, and tau is the transmission time of the light from the coupler to the reflection point in the annular waveguide resonant cavity; sigma is the transmission loss of the waveguide from the coupler to the reflection point;
R CW,CCW (f)＝(1-k C /(1-qe -i2πfτ ))(1-α C ) 1/2 /(1-k C ) 1/2 ,
T CW,CCW (f)＝k C (1-α c )(1-α L/2 ) 1/2 /(1-qe -i2πfτ ),
wherein alpha is C Is the cross-coupling ratio of losses, k C Is the cross-coupling ratio of the waveguide coupler, alpha L/2 The transmission loss is half-length of the waveguide resonant cavity, and q is total optical path loss of the waveguide ring resonator cavity.
Counterclockwise output E of annular waveguide resonant cavity out_CCW Expressed as:
step three, clockwise detector PD CW And a counter-clockwise detector PD CCW Respectively receive clockwise output light E out_CW And counterclockwise output light E out_CCW And converting the light containing the angular velocity information into an electrical signal;
clockwise detector PD CW Received theIs composed of forward light carrying an angular velocity signal and back reflected light. PD (potential difference) device CW The received clockwise output light intensity with back reflection is I out_CW ＝Re(E out_CW E * out_CW ) The method comprises the steps of carrying out a first treatment on the surface of the And I out_CW The frequency component of (2) comprises m 1 f B_CW 、m 2 f S_CW 、m 3 f B_CCW 、m 4 f S_CCW . In the gyroscope, f S_CW And f S_CCW Far below f B_CW The demodulation process is not affected. E (E) out_CW From and f B_CW The demodulated sine waves of the same frequency and phase are demodulated.
Step four, designing and f B_CW And f B_CCW The sine waves with the same frequency and phase are demodulated to obtain a demodulation result De CW ；
Fundamental modulation frequency f B_CW And f B_CCW Designed to be equal to obtain the optimum demodulation gain for a high signal-to-error ratio for closed loop detection.
Outputting clockwise light E of annular waveguide resonant cavity out_CW Multiplying the demodulation sine wave and the whole period T of the demodulation sine wave to obtain a demodulation result De CW By De CW1 ,De CW21 ,De CW22 And De CW23 The composition was calculated as follows:
step five, for the demodulation result De CW Analyzing the various items to obtain the optimal frequency value f of two triangular waves for inhibiting the back error S_CW And f S_CCW Separating the signal light from the back reflection light to inhibit the frequency spectrum of the back light related error of the resonant integrated optical gyroscope;
the specific analysis process is as follows:
demodulation result De CW Middle De CW1 Is a useful signal about the resonant frequency in the clockwise direction that contains angular velocity information and does not contain any back-reflection related terms.
De CW23 Only back-reflected light is contained and is negligible due to its low intensity.
De CW21 And De CW22 The back-reflected light and the signal light cannot be eliminated by demodulation integration. De CW21 Is the direct current component of the back reflection error, and is formed by the frequency f B_CW Is generated with an intensity that is only equal to the basic delta-modulated residual component M 2 (0)，M 4 (0) And (5) correlation. When modulating voltage V ppj When the peak-to-peak value of (2) pi phase of the integrated optical phase modulator is accurately adjusted to the voltage corresponding to the 2 pi phase of the integrated optical phase modulator j (0) De for accurately eliminating back reflection errors with zero amplitude CW21 An item.
De CW22 Is I out_CW Near demodulation frequency f B_CW A demodulation result of the frequency component of (a); thus, de CW22 Is slow and cannot eliminate De in a limited demodulation integration time CW22 。De CW22 Is of the amplitude of M j (m k ) And demodulation frequency f B_CW And I out_CW Is determined by taking into account f B_CW Frequency multiplication signal within 15 times of m k M is higher than 15 j (m k ) Smaller ones can be ignored. Thus, the spectral separation method is achieved by optimizing the modulation frequency f S_CW And f S_CCW So that f B_CW And I out_CW The minimum value Γ=min [ | (m) of the frequency difference between the frequency components of (c) 1 +1)f B_CW +m 2 f S_CW -m 3 f B_CCW -m 4 f S_CCW |]The maximum can be used for optimally separating the back reflection error and the gyroscope signal in the frequency domain so as to obtain the optimal back reflection error De CW22 Is effective in inhibiting the occurrence of a disease. Modulation frequency f B_CW And I out_CW The minimum value Γ of the frequency difference between the frequency components of (a) is as large as possible to ensure that the signal light and the back light are separated in the frequency domain. Furthermore, the output filter of the resonant integrated optical gyroscope can further inhibit De of back error CW22 A component. Setting a basic modulation frequency f according to definition of the resonant cavity B_CW And f B_CCW To obtain maximum demodulation gain and minimum optical effect nonlinearity. And, in order to maximize Γ to separate the back error and the gyroscope signal in the frequency domain, an optimal f is selected S_CW And f S_CCW 。
And step six, the laser frequency locking controller locks the output frequency of the laser on the static resonance frequency of the annular waveguide resonant cavity according to the sum of demodulation results of the clockwise detector and the anticlockwise detector, and the locked frequency is independent of whether the gyroscope rotates or not. Meanwhile, the angular velocity controller provides sawtooth wave feedback signals according to the demodulation result difference of the clockwise detector and the anticlockwise detector, and the sawtooth wave feedback signals are respectively and differentially added to the clockwise pointer light beam and the anticlockwise light beam through the integrated optical phase modulator to generate resonance frequency movement so as to offset resonance frequency difference generated by the angular velocity.
In the present invention, four triangular phase modulated waveforms, f B_CW And f S_CW The modulated wave is added to two beams of light propagating clockwise along the annular waveguide resonant cavity, f B_CCW And f S_CCW The modulated wave is applied to two beams of light propagating in the counterclockwise direction of the annular waveguide resonator. By designing triangular wave f S_CW And f S_CCW The optimum frequency value of (2) is such that the back reflection is spectrally separated from the signal light to suppress errors caused by the back light.
The double closed-loop control method is realized by a laser frequency locking controller and an angular velocity controller.
Examples:
specific parameters of the integrated optical gyro are as follows:
the tunable 1550nm semiconductor laser is used as a light source for experiments, and the output frequency of the tunable 1550nm semiconductor laser can be adjusted within 2 GHz. The Y-branch integrated optical phase modulator performs phase modulation including triangular wave f B_CW 、f B_CCW 、f S_CW And f S_CCW And angular velocity closed loop feedback sawtooth signals. Two PDs act as clockwise and counterclockwise probes for monitoring the resonator output. The ring waveguide cavity in the experiment was made of silica with a radius of 50mm and a definition of 130.
In the spectrum separation scheme of this embodiment, the FPGA generates a plurality of frequency-tunable waveforms f B_CW 、f B_CCW 、f S_CW And f S_CCW . In an experiment, step five according to the present invention set the fundamental modulation frequency f according to the definition 130 of the resonant cavity B_CW And f B_CCW Set to 1MHz; and, in order to maximize Γ to separate the back error and the gyroscope signal in the frequency domain, an optimal f is selected S_CW And f S_CCW f S_CW Set to 13kHz, f S_CCW 19kHz, as shown in figure 3. The modulation phase is [ -pi, pi]Internal variation.
The experimental verification is carried out on a frequency spectrum separation method for inhibiting the back light related error by the resonance type integrated optical gyroscope: the back-light intensity in the cavity is first measured as shown in fig. 4. When only the clockwise light is modulated at a fixed frequency, the back light intensity spectrum, including back reflection and back scattering, can be measured by comparing the clockwise and counter-clockwise outputs. From experiments, the back-light intensity of the resonant integrated optical gyroscope system was estimated to be 2% of the input light. It is known that the errors associated with the backlight are the main errors that lead to the fluctuation of the deviation of the resonant integrated optical gyroscope. Therefore, the back-light related error suppression method is important to improve the detection accuracy of the resonant integrated optical gyroscope.
The present embodiment further verifies the suppression effect of the back-light related error. Will modulate the fundamental frequency f B_CW And f B_CCW Set to 1MHz; and, best f S_CW And f S_CCW f S_CW Set to 13kHz, f S_CCW Is 19kHz. V (V) ppj (j=1, 2,3, 4) is set to 2pi phase of the integrated optical phase modulator. Fig. 5 shows the spectrum of the detector modulated signal in a resonant integrated optical gyroscope, and with the proposed spectral separation scheme it can be seen that the signals obtained by the two detectors do not have components of the same frequency, which satisfies the condition of spectral separation between the back light and the signal light. The back reflection is different from the frequency of the signal light, so that the DC term De in the back reflection error cannot be generated CW21 . Experiments prove that the direct-current term De capable of eliminating the backlight error by the scheme CW21 。
In addition, the bias stability experiment of the resonant integrated optical gyroscope is utilized to test the alternating current component De of the back light correlation error of the resonant integrated optical gyroscope through the proposed spectrum separation optimal strategy CW22 Is a natural product of the inhibition ability of the above-mentioned compound.
In the bias stability experiment of the resonant integrated optical gyroscope, the gyroscope is placed on a marble platform. The angular velocity sensed by the gyroscope is a component of the earth's rotational velocity perpendicular to the ground, which is approximately 9.6/h in the 40 ° N region of beijing. Fig. 6 shows the bias stability experimental results for the resonant integrated optical gyroscope with and without the spectral separation method. The output data of the resonant integrated optical gyroscope was smoothed for 10s and 100s, respectively, within 20000s to evaluate the performance of the gyroscope, as shown in fig. 6 a. After application of the proposed method, fig. 6a shows that the bias stability of the resonant integrated optical gyroscope increases from 31 °/h to 2.93 °/h, with an integration time of 10 seconds in the 5 hour test. And the tested Arrhena analysis of variance shows that the bias stability of the resonant integrated optical gyroscope adopting the method is improved from 5 degrees/h to 0.3 degrees/h, as shown in fig. 6b, and the method is the best result of the resonant integrated optical gyroscope based on the silicon waveguide resonant cavity at present. Experimental results show that the frequency spectrum separation method can effectively reduce the gyro output offset error caused by the back light correlation error, and the measurement accuracy of the resonant integrated optical gyroscope is remarkably improved.
According to the invention, the experiment verification of the frequency spectrum separation method for inhibiting the back light related error is carried out, the on-chip low-cost high-precision angular velocity measurement is realized on the resonant integrated optical gyroscope, the experiment shows that the measurement precision Allen variance of the resonant integrated optical gyroscope by using the frequency spectrum separation method reaches 0.3 degrees/h, the detection precision of the resonant integrated optical gyroscope is greatly improved by using the frequency spectrum separation method, and the application of the integrated optical gyroscope in novel micro-inertial navigation systems such as clustered unmanned aerial vehicles, micro-nano satellites and unmanned vehicles is facilitated.
Claims (7)
1. The frequency spectrum separation method for inhibiting the back reflection error of the resonant integrated optical gyroscope is characterized by comprising the following specific steps of:
step one, constructing a spectrum separation detection device for inhibiting the correlation error of back reflection light, adding four triangular phase modulation waveforms for inhibiting the back reflection error, and modulating clockwise input light E in a ring waveguide resonant cavity in_CW And input light E in the counterclockwise direction in_CCW ；
The spectrum separation detection apparatus includes: the device comprises a laser, an isolator, an integrated optical phase modulator, a ring waveguide resonant cavity, a clockwise detector, a counterclockwise detector, a laser frequency locking controller and an angular velocity controller;
light generated by the laser passes through the isolator and enters the integrated optical phase modulator to be separated into two beams of light; the two separated beams are phase modulated by four triangular phase modulation waveforms respectively, the four triangular phase modulation waveforms have the same initial phase and the same amplitude V ppj (j=1, 2,3, 4) corresponds to a phase shift 2 pi of the integrated optical phase modulator and the different frequencies are f, respectively B_CW 、f B_CCW 、f S_CW And f S_CCW ；
Frequency f B_CW And f S_CW For modulating clockwise input light E in annular waveguide resonator in_CW Expressed as:
wherein E is 0 e i2πft An output electric field of the laser; m is M j (m k )(j,k＝1,2,3,4,m k E Z) m for each triangular wave phase modulation respectively k The Fourier expansion coefficients; θ CW An initial phase for clockwise input light;
frequency f B_CCW And f S_CCW Input light E for modulating counter-clockwise direction of annular waveguide resonant cavity in_CCW Expressed as:
θ CCW an initial phase of the input light counterclockwise;
step two, two input light E modulated by triangle phase modulation waveform in_CW And E is in_CCW Respectively adding the light beams to two light beams propagating along the clockwise direction and the anticlockwise direction of the annular waveguide resonant cavity to obtain clockwise output light E of the annular waveguide resonant cavity out_CW And counterclockwise output light E out_CCW ；
Clockwise output light E out_CW Expressed as:
wherein S is 13 (2 pi f) is from E in_CW To E out_CW Light propagation model S of (2) 23 (2 pi f) is from E in_CCW To E out_CW Is a model of light propagation;
counterclockwise output E of annular waveguide resonant cavity out_CCW Expressed as:
step three, clockwise detector PD CW And a counter-clockwise detector PD CCW Respectively receive clockwise output light E out_CW And counterclockwise output light E out_CCW Converting into an electrical signal;
step four, designing and f B_CW And f B_CCW The sine waves with the same frequency and phase are demodulated to obtain a demodulation result De CW ；
Step five, for the demodulation result De CW Analyzing the various items to obtain the optimal frequency value f of two triangular waves for inhibiting the back error S_CW And f S_CCW Separating the signal light from the back reflection light to inhibit the frequency spectrum of the back light related error of the resonant integrated optical gyroscope;
step six, the laser frequency locking controller locks the output frequency of the laser on the static resonance frequency of the annular waveguide resonant cavity according to the sum of demodulation results of the clockwise detector and the anticlockwise detector, and the locked frequency is independent of whether the gyroscope rotates; meanwhile, the angular velocity controller provides sawtooth wave feedback signals according to the difference between demodulation results of the clockwise detector and the anticlockwise detector, and the sawtooth wave feedback signals are respectively and differentially added to the clockwise pointer light and the anticlockwise light through the integrated optical phase modulator to generate resonance frequency movement so as to offset resonance frequency difference generated by the angular velocity;
four triangular phase modulation waveforms are proposed and by designing triangular wave f S_CW And f S_CCW The optimum frequency value of (2) is such that the back reflection is spectrally separated from the signal light to suppress errors caused by the back light.
2. The method for spectrum separation of the resonant integrated optical gyroscope for suppressing back reflection errors of claim 1, wherein the step one specifically comprises:
the laser is connected with an integrated optical phase modulator through an isolator, the integrated optical phase modulator is connected with a ring waveguide resonant cavity, and light beams in the clockwise direction and the anticlockwise direction are transmitted in the ring waveguide resonant cavity; the output end of the annular waveguide resonant cavity is respectively connected with a clockwise detector and a anticlockwise detector, the sum of output results of the two detectors is connected with a laser frequency locking controller, and the output is fed back to the laser to lock the frequency on the static resonant frequency of the annular waveguide resonant cavity, so that a closed loop of the resonant cavity center resonant frequency is formed; meanwhile, the difference of output results of the two detectors is connected with an angular velocity controller, and a sawtooth wave feedback signal is provided for the integrated optical phase modulator to offset the resonance frequency difference of clockwise and anticlockwise light caused by the angular velocity signal, so that a closed loop of the angular velocity signal is formed;
in the resonant integrated optical gyroscope, the end face of the detector is a main source of back reflection error, because obvious refractive index difference exists between the front side and the rear side of the detector, even if an antireflection film exists, the back reflection is difficult to be inhibited;
the back-scattering errors are caused by scattered light that is randomly generated in the waveguide microstructure and that is inevitably present at scattering points throughout the resonator;
the suppressed back reflection includes back reflection light at the detector and back scattering light in the resonant cavity, which are all light propagating back along the resonant cavity, and finally superimposed on the resonant cavity output, affecting the demodulation result of the angular velocity signal; when the ring waveguide resonator, by virtue of the characteristics that the back reflection and the back dispersion generated in the path of the waveguide ring resonator have the same light propagation direction and have the same frequency and the phase difference is fixed, the method of frequency spectrum separation is proposed to separate the signal light and the back reflection/back dispersion in the frequency domain so as to inhibit the error generated by the back light and simultaneously inhibit the back reflection error and the back dispersion error.
3. The method for spectrum separation of the resonant integrated optical gyroscope for suppressing back reflection errors according to claim 1, wherein the two light propagation models in the second step have the following calculation formulas:
S 13 (2πf)＝T CW (f)(1-γ 2 )σ 2 e i4πfτ ，
S 23 (2πf)＝e iπ γ(1-γ 2 ) 1/2 σ 4 e i8πfτ (T CCW (f)R CW (f)+T CW (f)R CCW (f))
wherein γ is the back reflectivity of the reflection point; t (T) CW (f) And T CCW (f) Respectively, is a ring waveguide harmonic obtained by using multi-beam interference theoryTransmission transfer function of cavity clockwise and anticlockwise, R CW (f) And R is CCW (f) Respectively, the transmission functions of clockwise and anticlockwise light in the annular waveguide resonant cavity, and tau is the transmission time of the light from the coupler to the reflection point in the annular waveguide resonant cavity; sigma is the transmission loss of the waveguide from the coupler to the reflection point;
R CW,CCW (f)＝(1-k C /(1-qe -i2πfτ ))(1-α C )/ 1/2 (1-k C ) 1/2 ,
T CW,CCW (f)＝k C (1-α c )(1-α L/2 ) 1/2 /(1-qe -i2πfτ ),
wherein alpha is C Is the cross-coupling ratio of losses, k C Is the cross-coupling ratio of the waveguide coupler, alpha L/2 The transmission loss is half-length of the waveguide resonant cavity, and q is total optical loss of the waveguide ring resonator cavity.
4. The method for spectrum separation of resonant integrated optical gyroscope for suppressing back reflection error as claimed in claim 1, wherein the detector PD is clockwise in the third step CW The received light consists of forward light with an angular velocity signal and back reflected light.
5. The method for spectrum separation of resonant integrated optical gyroscope for suppressing back reflection error as recited in claim 1, wherein in the fourth step, the clockwise output light E of the annular waveguide resonant cavity is output out_CW Multiplying the demodulation sine wave and the whole period T of the demodulation sine wave to obtain a demodulation result De CW By De CW1 ,De CW21 ,De CW22 And De CW23 The composition was calculated as follows:
6. the method for spectrum separation of the resonant integrated optical gyroscope for suppressing back reflection errors according to claim 1, wherein the fifth specific analysis process is as follows:
demodulation result De CW Middle De CW1 Is a useful signal about the resonant frequency in the clockwise direction, it contains angular velocity information, and does not contain any back-reflection related terms;
De CW23 only back-reflected light is contained and is negligible due to its low intensity;
De CW21 is the direct current component of the back reflection error, and is formed by the frequency f B_CW Is generated with an intensity that is only equal to the basic delta-modulated residual component M 2 (0)，M 4 (0) Correlation; when modulating voltage V ppj When the peak-to-peak value of (2) pi phase of the integrated optical phase modulator is accurately adjusted to the voltage corresponding to the 2 pi phase of the integrated optical phase modulator j (0) De for accurately eliminating back reflection errors with zero amplitude CW21 An item;
De CW22 by optimally modulating f of different frequencies S_CW And f S_CCW So that the modulation frequency f B_CW And I out_CW The minimum value Γ=min [ | (m) of the frequency difference between the frequency components of (c) 1 +1)f B_CW +m 2 f S_CW -m 3 f B_CCW -m 4 f S_CCW |]As large as possible, separating the signal light from the back light in the frequency domain to obtain an optimal back reflection error De CW22 Is effective in inhibiting the occurrence of a disease.
7. Such as weightThe method for spectrum separation of resonant integrated optical gyroscope for suppressing back reflection error as recited in claim 1, wherein f in said four triangular phase modulation waveforms B_CW And f S_CW The modulated wave is added to two beams of light propagating clockwise along the annular waveguide resonant cavity, f B_CCW And f S_CCW The modulated wave is added on two beams of light propagating along the anticlockwise direction of the annular waveguide resonant cavity; fundamental modulation frequency f B_CW And f B_CCW Designed to be equal, forming a fundamental carrier rejection frequency for maintaining maximum demodulation gain and minimum optical effect nonlinearity of the resonant integrated optical gyroscope; by designing f S_CW And f S_CCW The optimum frequency value of the triangular waveform of the (c) is such that the back reflection is spectrally separated from the signal light to suppress errors caused by the back light.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101464151A (en) * | 2009-01-05 | 2009-06-24 | 浙江大学 | Detection apparatus and method for miniature resonance type optical gyroscope with double-signal combined modulation |
| US9459101B1 (en) * | 2015-06-15 | 2016-10-04 | Honeywell International Inc. | Systems and methods for fiber optic gyroscopes utilizing reference ring resonators |
| CN108168537A (en) * | 2018-02-06 | 2018-06-15 | 浙江大学 | The detecting system and method for resonance type optical gyroscope based on quadrature demodulation |
| CN111238464A (en) * | 2020-01-19 | 2020-06-05 | 浙江大学 | Detection system and method of resonant optical gyroscope based on combination of reciprocity modulation and time division switching |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101464151A (en) * | 2009-01-05 | 2009-06-24 | 浙江大学 | Detection apparatus and method for miniature resonance type optical gyroscope with double-signal combined modulation |
| US9459101B1 (en) * | 2015-06-15 | 2016-10-04 | Honeywell International Inc. | Systems and methods for fiber optic gyroscopes utilizing reference ring resonators |
| CN108168537A (en) * | 2018-02-06 | 2018-06-15 | 浙江大学 | The detecting system and method for resonance type optical gyroscope based on quadrature demodulation |
| CN111238464A (en) * | 2020-01-19 | 2020-06-05 | 浙江大学 | Detection system and method of resonant optical gyroscope based on combination of reciprocity modulation and time division switching |
Non-Patent Citations (1)
| Title |
|---|
| 谐振腔光纤陀螺信号检测方法的研究;马慧莲,金仲和,丁纯,王跃林;中国激光(第08期);全文 * |
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