Fully integrated monolithic silicon photonic gyroscope and noise suppression method thereof

Abstract

The application provides a full integration type monolithic silicon photon gyroscope and a noise suppression method thereof, the gyroscope comprising a silicon photon chip and an ASIC circuit, the silicon photon chip comprising a laser, a Y branch, three couplers, a waveguide resonant cavity and four detectors, two of the detectors being used for detecting resonant signals of the waveguide resonant cavity, and the other two detectors being used for detecting intensity changes of laser output light signals; the ASIC circuit comprising a current control module and a rotation speed demodulation and compensation module, the current control module being used for determining square wave current signal parameters according to measured parameters of the waveguide resonant cavity, and tuning the square wave current signal according to differential mode components of clockwise and counterclockwise resonant signals; the rotation speed demodulation and compensation module being used for calculating measured parameters of the waveguide resonant cavity according to voltage signals detected by the detectors, calculating differential mode and common mode components of the clockwise and counterclockwise resonant signals, calculating intensity compensation parameters and frequency compensation parameters, and calculating a gyroscope output.

Description

Technical Field

[0001] This invention belongs to the field of optical sensing technology, specifically relating to a fully integrated monolithic silicon photonic gyroscope and its noise suppression method. Background Technology

[0002] Fiber optic gyroscopes possess outstanding advantages such as high precision, all-solid-state construction, and flexible structure. They have already been developed into a series of products and have become the preferred inertial measurement element for inertial navigation systems of various precision levels. With the deepening of applications, there is an urgent need for fiber optic gyroscopes to possess advantages such as miniaturization, low cost, and high reliability. Domestic and international research institutions have attempted to achieve these goals through device miniaturization and system micro-assembly. However, miniaturized optoelectronic devices face disadvantages such as high cost and poor reliability, and micro-assembly schemes have limited impact on reducing the size of fiber optic gyroscopes. The miniaturization and low-cost development of fiber optic gyroscopes has encountered a bottleneck. In recent years, with the rapid development of integrated optics and micro / nano fabrication technologies, integrating multiple active and passive optical devices onto a single silicon photonic chip has become possible and is widely used in the communication field. This provides a new approach for the integration and miniaturization of fiber optic gyroscopes: combining the advantages of silicon photonic chip miniaturization and ease of mass production with the high precision of fiber optic gyroscopes, silicon photonic gyroscopes are gradually becoming a cutting-edge hot topic in the international next-generation optical gyroscope market.

[0003] The integration of multiple materials introduces material compatibility issues. For example, active materials used in light source fabrication have good hybrid integration potential with PLC materials used in couplers and on-chip rings, and Ge materials used in detector fabrication. However, LiNbO3 materials used in optical phase modulators are difficult to integrate with other types of materials, posing challenges to the integrated design of multiple devices and becoming a bottleneck limiting the improvement of integration density. Furthermore, the integration of optical paths inevitably introduces problems such as chip heating, intensity noise, and Kerr noise, severely restricting the performance improvement of silicon photonic gyroscopes. Therefore, there is an urgent need for a silicon photonic gyroscope technology solution that does not integrate a LiNbO3 phase modulator (i.e., a fully integrated monolithic design) and possesses noise compensation capabilities. Summary of the Invention

[0004] To address the technical problems of limited integration in existing silicon photonic gyroscopes, this invention provides a fully integrated monolithic silicon photonic gyroscope and its noise suppression method. A laser, detector, coupler, and waveguide resonant cavity are integrated on a silicon photonic chip. By controlling the driving current of the laser, the gyroscope has a high-sensitivity detection range, thereby improving the chip integration.

[0005] To address the technical problems existing in the prior art, this invention provides a fully integrated monolithic silicon photonic gyroscope, comprising:

[0006] A silicon photonic chip includes a laser, a Y-branch, couplers C1, C2, and C3, a waveguide resonant cavity, and detectors PD1, PD2, PD3, and PD4. Couplers C1, C2, and C3 are all 2×2 couplers. The laser output is connected to the Y-branch input. The two outputs of the Y-branch are connected to ports a of couplers C1 and C2, respectively. Ports b of couplers C1 and C2 are connected to ports a and b of coupler C3, respectively. Ports c and d of coupler C3 are connected to the two input and output ports of the waveguide resonant cavity, respectively. Port c of couplers C1 and C2 is connected to detectors PD1 and PD2, respectively. Port d of couplers C1 and C2 is connected to detectors PD3 and PD4, respectively. Detectors PD1 and PD2 are used to detect the resonant signal of the waveguide resonant cavity, and detectors PD3 and PD4 are used to detect the intensity change of the laser output light signal.

[0007] An ASIC circuit is included, comprising a current control module and a speed demodulation and compensation module. The current control module determines the square wave current signal parameters based on the measured parameters of the waveguide resonant cavity and tunes the square wave current signal based on the differential mode components of the clockwise and counterclockwise resonant signals. The speed demodulation and compensation module calculates the measured parameters of the waveguide resonant cavity based on the voltage signals detected by each detector, calculates the differential mode and common mode components of the clockwise and counterclockwise resonant signals, calculates the intensity compensation parameters and frequency compensation parameters, and calculates the gyroscope output.

[0008] Furthermore, the silicon photonic gyroscope also includes a temperature control signal module, used to linearly scan the temperature of the laser and adjust the center frequency of the laser to be within the resonant valley frequency range of the counterclockwise resonant signal of the waveguide resonant cavity.

[0009] Furthermore, the speed demodulation and compensation module specifically includes the following units:

[0010] The resonant cavity measured parameter calculation unit is used to calculate the measured parameters of the waveguide resonant cavity based on the voltage signals detected by each detector. The measured parameters include the overall transmission loss, current-power tuning coefficient, current-frequency tuning coefficient, and optical path intensity attenuation coefficient.

[0011] The CW demodulation unit is used to demodulate the output clockwise resonant signal to obtain a digital signal;

[0012] The CCW demodulation unit is used to demodulate the output counterclockwise resonant signal to obtain a digital signal.

[0013] The differential mode calculation unit is used to perform difference calculations on clockwise and counterclockwise resonant signals to obtain the differential mode components.

[0014] The common-mode calculation unit is used to sum the clockwise and counterclockwise resonant signals to obtain the common-mode components;

[0015] The gyroscope closed-loop and parameter compensation calculation unit is used to calculate the intensity compensation parameters and frequency compensation parameters based on the differential mode components and measured parameters.

[0016] The noise compensation unit is used to calculate the gyroscope output based on the common-mode component, combined with intensity compensation parameters and frequency compensation parameters.

[0017] This invention also provides a noise suppression method for a fully integrated monolithic silicon photonic gyroscope, comprising the following steps:

[0018] Design a square wave current signal for the input laser, wherein the design parameters of the square wave current signal include frequency, tuning range, and amplitude;

[0019] When the ASIC circuit is powered on, the set square wave current signal is applied to the laser.

[0020] After determining that the counterclockwise resonant signal has entered a valley, the clockwise and counterclockwise resonant signals are demodulated, and the differential-mode components and common-mode components of the clockwise and counterclockwise resonant signals are calculated. The differential-mode component is the clockwise resonant signal minus the counterclockwise resonant signal.

[0021] If the differential mode component is determined to be 0, the control square wave current signal is kept at its current value.

[0022] If the differential mode component is greater than 0, the square wave current signal is controlled to be tuned down; if the differential mode component is less than 0, the square wave current signal is controlled to be tuned up.

[0023] Through multiple tuning processes, the center frequency of the laser is steadily locked to the resonant frequency of the waveguide resonant cavity, ensuring that the square wave current signal remains unchanged.

[0024] Furthermore, the square wave current signal design method includes the following steps:

[0025] S101. The frequency of the square wave current signal is designed to be greater than the relative intensity noise frequency of the laser and less than the upper limit of the laser tuning bandwidth frequency.

[0026] S102. Determine the optimal current tuning region of the laser and set the bias current to the median value of the optimal current tuning region of the laser.

[0027] The upper and lower extreme values ​​of the tuning range are determined based on the maximum free spectral width of the square wave current signal covering at least one waveguide resonant cavity.

[0028] S103. Determine the amplitude of the square wave current signal based on the gyroscope's maximum sensitivity.

[0029] Furthermore, the upper and lower extrema of the tuning interval are set to i. max -i max ,but

[0030] 2i max K f-i >1.5FSR

[0031] Among them, K f-i is the frequency-current tuning factor of the laser, and FSR is the maximum free spectral linewidth.

[0032] Further, step S103 includes the following steps:

[0033] The laser is input with a set bias current, the voltage of the laser after passing through coupler C1 and coupler C2 is collected, and the total transmission loss of coupler C1 and coupler C2 is calculated.

[0034] The laser is input with a set bias current, the output voltages of detectors PD1 and PD2 are collected, and the optical path intensity attenuation coefficient is calculated.

[0035] A sawtooth wave current signal with a frequency of 1Hz is input to the laser. The output voltage of detector PD3 is collected, and the current-intensity tuning coefficient is calculated.

[0036] A sawtooth wave current signal with a frequency of 1Hz is input to the laser. The output voltage of detector PD1 is collected, and the current-frequency tuning coefficient is calculated.

[0037] The gyroscope sensitivity is

[0038]

[0039] Where Δi is the amplitude of the square wave current signal, α is the total transmission loss of coupler C1 and coupler C2, and K p-i K f-i These are the current-intensity tuning coefficient and the current-frequency tuning coefficient, respectively, and A is the optical path intensity attenuation coefficient;

[0040] By taking the derivative of the gyroscope sensitivity with respect to Δi and setting dK / dΔi=0, the amplitude of the square wave current signal is obtained.

[0041] Furthermore, the formula for calculating the overall transmission loss is as follows:

[0042] α = α1 + α2

[0043]

[0044] Among them, R 3f A 3f These represent the transresistivity and current responsivity of detector PD3, respectively, R 4fA 4f V1 and V2 are the transresistivity and current responsivity of detector PD4, respectively; V0 is the no-light voltage of detectors PD3 and PD4; V1 and V2 are the voltages of the laser under steady-state conditions detected by detectors PD3 and PD4, respectively; and P0 is the output power of the laser under steady-state conditions.

[0045] The method for calculating the optical path intensity attenuation coefficient is as follows:

[0046]

[0047] Among them, R 1f A 1f These represent the transresistivity and current responsivity of detector PD1, respectively, R 2f A 2f V'0 represents the transresistivity and current responsivity of detector PD2, respectively; V'0 represents the no-light voltage of detectors PD1 and PD2; V'1 and V'2 represent the voltages of the laser under steady-state conditions detected by detectors PD1 and PD2, respectively; and P0 represents the output power of the laser under steady-state conditions.

[0048] The current-intensity tuning coefficient is calculated as follows:

[0049]

[0050] Where i0 and i1 are the minimum and maximum values ​​of the sawtooth wave current signal, respectively, and V0” and V”1 are the voltages corresponding to i0 and i1 detected by detector PD3, respectively. R 3f A 3f These are the transresistivity and current responsivity of detector PD3, respectively.

[0051] The current-frequency tuning coefficient is calculated as follows:

[0052]

[0053] Where c is the speed of light, n is the refractive index of the waveguide resonant cavity, L is the cavity length of the waveguide resonant cavity, and i a and i b These are the currents corresponding to two adjacent resonant signals detected by detector PD1.

[0054] Furthermore, the square wave current signal design method also includes the following steps:

[0055] Calculate strength compensation parameters:

[0056] A P =k1×K P-i ×σ i

[0057] Where k1 is the strength error constant, σ i K is the difference between the current drive current and the initial current. p-i This refers to the current-intensity tuning factor;

[0058] Calculate frequency compensation parameters:

[0059] A f =k2×K f-i ×σ i

[0060] Where k2 is the frequency error constant, K f-i This refers to the current-frequency tuning coefficient.

[0061] The calculated gyroscope output after compensation is:

[0062] D 补偿后 =D 补偿前 +iA p +iA f

[0063] Where i is the current drive current.

[0064] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0065] The beneficial effects of this invention compared to the prior art are as follows:

[0066] This invention proposes a high-precision silicon photonic gyroscope that does not require a phase modulator and has noise suppression capabilities, with the following three advantages:

[0067] (1) A silicon photonic chip integrating a light source, detector, coupler and on-chip ring was used. Instead of using the traditional LiNbO3 optical phase modulator to achieve signal modulation, the square wave signal was modulated on the drive current terminal of the laser. Since the laser has a large modulation bandwidth, it can meet the high speed application of silicon photonic gyroscope. From the design of the optical chip, it also has a smaller size and lower cost.

[0068] (2) The accuracy improvement scheme of “common-differential mode noise suppression structure + error compensation” was adopted, and the compensation algorithm was embedded into the ASIC circuit. Differential mode was used as control to suppress common-mode intensity error caused by temperature-induced changes in optical path intensity and extinction ratio. Common mode was used as output to suppress differential-mode intensity error represented by Kerr error, thereby improving the accuracy of silicon photonic gyroscope.

[0069] (3) Differential mode control is adopted, which makes the closed loop faster and improves the dynamic response capability and environmental anti-interference capability of silicon photonic gyroscope. Attached Figure Description

[0070] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0071] Figure 1 A schematic diagram of the structure of a fully integrated monolithic silicon photonic gyroscope provided in a specific embodiment of the present invention;

[0072] Figure 2 A schematic diagram illustrating the principle of the speed demodulation and compensation module provided in a specific embodiment of the present invention;

[0073] Figure 3 A schematic diagram of a square wave current signal of a silicon photonic gyroscope provided in a specific embodiment of the present invention;

[0074] Figure 4 A flowchart illustrating a noise suppression method for a fully integrated monolithic silicon photonic gyroscope, provided as a specific embodiment of the present invention. Detailed Implementation

[0075] Specific embodiments of the present invention will now be described in detail. In the following description, specific details are set forth for purposes of explanation and not limitation, in order to aid in a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced in other embodiments departing from these specific details.

[0076] It should be noted that, in order to avoid obscuring the invention with unnecessary details, only the device structure and / or processing steps closely related to the solution of the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0077] As one aspect of the present invention, a fully integrated monolithic silicon photonic gyroscope is provided, which does not require a phase modulator and has noise suppression capabilities. The overall structure of this silicon photonic gyroscope is as follows: Figure 1 As shown, it includes a silicon photonic chip and an application-specific integrated circuit (ASIC). The silicon photonic chip includes detectors PD1, PD2, PD3, and PD4, a laser, a Y-branch, couplers C1, C2, and C3, and a waveguide resonant cavity. The ASIC circuit includes a current control module, a temperature control signal module, and a speed demodulation and compensation module.

[0078] On the silicon photonic chip, couplers C1, C2, and C3 are all 2×2 couplers. The laser output is connected to the Y-branch input. The two outputs of the Y-branch are connected to port a of couplers C1 and C2, respectively. Port b of couplers C1 and C2 is connected to ports a and b of coupler C3, respectively. Ports c and d of coupler C3 are connected to the two input and output ports of the waveguide resonant cavity, respectively. Port c of couplers C1 and C2 is connected to detectors PD1 and PD2, respectively. Port d of couplers C1 and C2 is connected to detectors PD3 and PD4, respectively. Detectors PD1 and PD2 are used to detect the resonant signal of the waveguide resonant cavity, and detectors PD3 and PD4 are used to detect the intensity change of the laser output light signal.

[0079] The current control module is used to determine the square wave current signal parameters based on the measured parameters of the waveguide resonant cavity, and to tune the square wave current signal based on the differential mode components of the clockwise and counterclockwise resonant signals.

[0080] The speed demodulation and compensation module is used to calculate the measured parameters of the waveguide resonant cavity based on the voltage signals detected by each detector, calculate the differential-mode and common-mode components of the clockwise and counterclockwise resonant signals, calculate the intensity compensation parameters and frequency compensation parameters, and calculate the gyroscope output. Further, the speed demodulation and compensation module specifically includes the following units:

[0081] The resonant cavity measured parameter calculation unit is used to calculate the measured parameters of the waveguide resonant cavity based on the voltage signals detected by each detector. The measured parameters include the overall transmission loss, current-power tuning coefficient, current-frequency tuning coefficient, and optical path intensity attenuation coefficient.

[0082] The CW demodulation unit is used to demodulate the output clockwise resonant signal to obtain a digital signal;

[0083] The CCW demodulation unit is used to demodulate the output counterclockwise resonant signal to obtain a digital signal.

[0084] The differential mode calculation unit is used to perform difference calculations on clockwise and counterclockwise resonant signals to obtain the differential mode components.

[0085] The common-mode calculation unit is used to sum the clockwise and counterclockwise resonant signals to obtain the common-mode components;

[0086] The gyroscope closed-loop and parameter compensation calculation unit is used to calculate the intensity compensation parameters and frequency compensation parameters based on the differential mode components and measured parameters.

[0087] The noise compensation unit is used to calculate the gyroscope output based on the common-mode component, combined with intensity compensation parameters and frequency compensation parameters.

[0088] The temperature control signal module is used to linearly scan the temperature of the laser and adjust the center frequency of the laser to be within the resonant valley frequency range of the counterclockwise resonant signal of the waveguide resonant cavity.

[0089] The optical path transmission path of the silicon photonic gyroscope is as follows: The laser emitted by the laser on the silicon photonic chip enters the Y branch and is split into two linearly polarized beams of equal power. These beams pass through couplers C1 and C2, and then through coupler C3, respectively, into the waveguide resonant cavity. The two beams propagate clockwise and counterclockwise in the waveguide resonant cavity, respectively. After the beams with different numbers of turns propagate in the waveguide resonant cavity, they exit and form multi-beam interference at the two exit ports of coupler C3. The interference signals reach detector PD1 via coupler C1 to form a clockwise resonant signal, and reach detector PD2 via coupler C2 to form a counterclockwise resonant signal. The counterclockwise signal is used for closed-loop demodulation and laser control to stabilize the laser center frequency relative to the resonant frequency of the resonant cavity. The clockwise signal is used for speed demodulation and intensity compensation to detect the speed and suppress the intensity noise introduced by the laser square wave current modulation and the silicon photonic chip. The temperature control signal controls the temperature of the laser. Detectors PD3 and PD4 detect the intensity changes of the output optical signal of the laser, which are used to calculate the measured parameters of the silicon-based waveguide resonant cavity.

[0090] Speed ​​demodulation and compensation module, such as Figure 2 As shown, based on the parameters V1, V2, V3 input from multiple detectors... CW and V CCW The measured parameters of the silicon-based resonant cavity are calculated to obtain the required square wave current signal parameters, which serve as the core of the closed-loop control. Simultaneously, the CW signal (clockwise resonant signal) and CCW signal (counterclockwise resonant signal) are integrated, and their differential mode component is used as the control input for the laser's square wave current signal, used for tuning the square wave current signal. Its common mode component is also obtained as the compensation input for the silicon photonic gyroscope. Intensity compensation parameters and frequency compensation parameters are calculated based on the square wave current signal output. These two compensation parameters are transmitted to the compensation module in real time, and combined with the common mode component, the compensated gyroscope output is obtained.

[0091] In this invention, the ASIC circuit integrates a current control module to generate a tunable square wave current signal with a certain bias, which is then applied to the current control terminal of the laser. Its functions are threefold: 1) to provide bias current, enabling constant drive current control of the laser; 2) to achieve current modulation at a certain frequency and amplitude, thereby replacing the phase modulation method in traditional silicon photonic gyroscopes; and 3) to adjust the square wave current signal in real time based on the closed-loop demodulation results, achieving closed-loop control of the laser center frequency on the waveguide resonant cavity resonant frequency, thus laying the foundation for rotational speed detection.

[0092] At the gyroscope closed-loop control terminal, the current control module first sends out DC and sawtooth wave signals respectively. Based on the conversion relationship, it obtains the measured parameters of the silicon-based waveguide resonant cavity, specifically including overall transmission loss, current-power tuning coefficient, current-frequency tuning coefficient, and optical path intensity attenuation coefficient. These measured parameters are then transmitted to the current control module. According to the solution algorithm, the frequency, tuning range, and amplitude parameters of the modulation current are obtained. The current control module then generates a corresponding modulation current to the laser's drive current control terminal. Combined with the temperature control signal, this achieves stable laser control. Because measured parameters are used, the sensitivity of the silicon photonic gyroscope is established more accurately, and the gyroscope achieves maximum sensitivity. Simultaneously, an overall control and accuracy improvement scheme of "differential-mode control and common-mode compensation output" is adopted. Compared to the traditional single-signal closed-loop, single-signal output scheme, it has better dynamic response capability and anti-interference advantages. Compared to the existing "common-mode control and differential-mode output" scheme, it not only achieves compensation but also jointly suppresses common-mode and differential-mode intensity noise, resulting in a significant improvement in the accuracy of the silicon photonic gyroscope.

[0093] As another aspect of the present invention, a noise suppression method for a fully integrated monolithic silicon photonic gyroscope is provided, comprising the following steps:

[0094] I. Design of Square Wave Current Signal

[0095] The design parameters of a square wave current signal mainly include frequency, tuning range, and amplitude. These are prerequisites for determining the gyroscope's sensitivity and system stability. The methods for establishing these parameters are as follows:

[0096] (1) First, it is necessary to determine the frequency of the square wave current signal: the frequency f of the square wave current signal. i The tuning bandwidth is mainly determined by the narrow linewidth laser. Typically, the tuning frequency of a frequency-tunable narrow linewidth laser (i.e., when using sinusoidal modulation) can reach 300k-1MHz. However, since the square wave current signal is a multiple harmonic component of the tuning frequency, the modulation frequency of the square wave current signal cannot be too high in order to ensure the tuning bandwidth, and it usually needs to be less than 100kHz. In addition, the relative intensity noise of the narrow linewidth laser is mainly concentrated below 10kHz, and the noise amplitude is inversely proportional to the frequency. In order to achieve a better relative intensity noise suppression effect, the modulation frequency of the square wave current signal needs to be greater than 10kHz. Therefore, considering both modulation speed and noise suppression effect, the preferred frequency of the square wave current signal is 10k to 100kHz.

[0097] (2) Secondly, it is necessary to establish the tuning range of the square wave current signal, namely the bias current and the tuning current: Since the theoretical optimal current tuning range of traditional narrow linewidth lasers is 80-140mA, the laser has the best tuning linearity in this range. Preferably, the bias current is set to the middle value of the optimal current tuning range, namely 110mA. This can take into account both the maximum current tuning range and the optimal tuning linearity, thereby ensuring the gyroscope closed-loop control range and scaling factor performance.

[0098] The tuning current design needs to take into account the frequency-current tuning coefficient K of the narrow linewidth laser. f-i The design principle for the maximum free spectral linewidth (FSR) of the waveguide resonator is to cover at least one complete FSR within the current tuning range. To allow for a certain margin, a frequency range coverage of 1.5 FSR is set. The upper and lower extreme values ​​of the tuning current are designed as i... max and -i max Ensure 2i max K f-i >1.5FSR design requirements.

[0099] Therefore, the tuning range of the square wave current signal is established as: (110-i max )mA~(110+i max )mA.

[0100] (3) Finally, the amplitude of the square wave current signal needs to be determined: the amplitude of the square wave current signal determines the magnitude of the laser frequency modulation, and different laser frequencies correspond to different gyroscope sensitivities K, which satisfy formula (1):

[0101]

[0102] Where Δi is the amplitude of the square wave current signal, α is the total transmission loss of coupler C1 and coupler C2, and K P-i K f-i These are the current-intensity tuning coefficient and the current-frequency tuning coefficient, respectively, and A is the intensity attenuation coefficient of the entire optical path.

[0103] This invention, based on measured parameters of a silicon-based resonant cavity, determines the amplitude of a square wave current signal to maximize the sensitivity of the silicon photonic gyroscope. The specific steps for determining the optimal amplitude of the square wave current signal are as follows:

[0104] 1) Measured total transmission loss α of couplers C1 and C2:

[0105] The current control module outputs an optimal bias current of 110mA. At this point, the laser maintains a stable power output P0 (obtained from the laser's IP curve) without any modulation current. The loss α1 of coupler C1 is obtained from the voltage V1 detected by detector PD3, and the loss α2 of coupler C2 is obtained from the voltage V2 detected by detector PD4. α1, α2, and α are calculated as follows:

[0106]

[0107] α=α1+α2 (4)

[0108] Among them, R 3f A 3f These represent the transresistivity and current responsivity of detector PD3, respectively, R 4f A 4f V1 and V2 are the transresistivity and current responsivity of detector PD4, respectively; V0 is the no-light voltage of detectors PD3 and PD4; V1 and V2 are the voltages of the laser under steady-state conditions detected by detectors PD3 and PD4, respectively; and P0 is the output power of the laser under steady-state conditions.

[0109] 2) Measured intensity attenuation coefficient A of the entire optical path:

[0110] The current control module outputs an optimal bias current of 110mA. At this time, the laser maintains a stable power output P0 (P0 is obtained from the laser IP curve) without modulation current. The detection voltages V'1 and V'2 of detectors PD1 and PD2 are detected, and the intensity attenuation coefficient A of the entire optical path is calculated according to formula (5):

[0111]

[0112] Among them, R 1f A 1f These represent the transresistivity and current responsivity of detector PD1, respectively, R 2f A 2f V'0 represents the transresistivity and current responsivity of detector PD2, respectively; V'0 represents the no-light voltage of detectors PD1 and PD2; V'1 and V'2 represent the voltages of the laser under steady-state conditions detected by detectors PD1 and PD2, respectively; and P0 represents the output power of the laser under steady-state conditions.

[0113] 3) Measured current-intensity tuning coefficient K P-i :

[0114] The current control module outputs a sawtooth wave current signal with a frequency of 1Hz, and its minimum and maximum values ​​are i0 and i1, respectively. At this time, the laser maintains a linearly changing power output without modulation current. The voltage V”1 detected by the detector PD3 in the speed demodulation and compensation module also shows a linear change, and its initial value is V0”. The current-intensity tuning coefficient K is calculated according to formula (6). P-i :

[0115]

[0116] Where i0 and i1 are the minimum and maximum values ​​of the sawtooth wave current signal, respectively, and V0” and V”1 are the voltages corresponding to i0 and i1 detected by detector PD3, respectively. R 3f A 3f These are the transresistivity and current responsivity of detector PD3, respectively.

[0117] 4) Measured current-frequency tuning coefficient K f-i :

[0118] The current control module outputs a sawtooth wave current signal with a frequency of 1Hz, whose minimum and maximum values ​​are i0 and i1, respectively. At this time, the laser maintains a linearly changing power output without modulation current. A clear resonant signal can be observed in detector PD1. The speed demodulation and compensation module records the current magnitudes corresponding to two adjacent resonant signals, which are i0 and i1, respectively. a and i b The current-frequency tuning coefficient K is calculated according to formula (7). f-i :

[0119]

[0120] Where c is the speed of light, n is the refractive index of the waveguide resonant cavity, L is the cavity length of the waveguide resonant cavity, and i a and i b These are the currents corresponding to two adjacent resonant signals detected by detector PD1;

[0121] 5) Taking the derivative of formula (1) with respect to the square wave current signal amplitude Δi, and setting dK / dΔi=0, this is the condition for the gyroscope sensitivity K to reach its maximum value. Substituting the measured α, A, and K... P-i and K f-i The square wave current signal amplitude Δi is obtained when dK / dΔi = 0, and is used as the square wave current signal amplitude established in this invention.

[0122] The final designed silicon photonic gyroscope square wave current signal is as follows: Figure 3 As shown, it is specifically divided into three intervals: the upper tuning region, the lower tuning region, and the modulation region, with a tuning range of 2i. maxmA, where the upper tuning region covers 110 mA ~ (110+i max )mA, lower tuning region coverage (110-i max )mA~110mA, with the modulation region located at (110±Δi)mA.

[0123] The functions of each zone of the square wave current signal are as follows:

[0124] Modulation region: mainly to achieve laser frequency modulation under the optimal square wave current signal amplitude Δi in order to obtain the maximum silicon photonic gyroscope sensitivity;

[0125] Upper tuning region: mainly when the differential mode signal of CW signal and CCW signal is less than 0, the driving current (i.e. square wave current) is tuned upward so that it steadily approaches 0 value.

[0126] Down-tuning region: This mainly involves detecting that when the differential mode signal of CW and CCW is greater than 0, the drive current is tuned downwards, so that it steadily approaches 0.

[0127] Through up and down tuning, the differential mode signals of CW and CCW are ultimately used to achieve closed-loop tracking and locking of the resonant cavity signal.

[0128] This invention, by employing a current modulation technique and optimizing the current modulation parameters, offers the following advantages over traditional phase modulation schemes:

[0129] (1) The LiNbO3 material in the traditional phase modulation scheme has been removed, which makes it easier to achieve true on-chip integration and is conducive to further reduction of gyroscope size, weight, power consumption and cost;

[0130] (2) Based on the measured parameters of silicon photonic chips, the current modulation parameters are optimized so that the silicon photonic gyroscope can obtain the maximum dynamic range under the maximum gyroscope sensitivity. Since the measured parameters are used, the sensitivity is established more accurately, the gyroscope has the maximum sensitivity, and it is also beneficial to improve the environmental adaptability and anti-interference ability of silicon photonic gyroscope.

[0131] II. Methods for demodulating the rotational speed and suppressing noise in silicon photonic gyroscopes, such as... Figure 4 As shown.

[0132] The specific workflow and steps are as follows:

[0133] (1) When the ASIC circuit is powered on, the ASIC circuit first performs a reset detection. If the reset signal is high, the circuit board is initialized; if the reset signal is low, the square wave current signal is set according to the established square wave current signal frequency, amplitude and tuning range, and applied to the laser current pin of the silicon photonic chip.

[0134] (2) The valley entry is determined based on the CCW signal. The specific determination method is based on the comparison voltage. If it is low, it means that it is outside the valley. At this time, the temperature control signal in the ASIC circuit performs a sawtooth wave linear scan on the laser die temperature to achieve linear scan within a certain temperature range until the center frequency of the laser is within the resonant valley frequency range of the resonant cavity CCW.

[0135] (3) Once the speed demodulation and intensity compensation module detects that the center frequency of the laser is within the resonant valley frequency range, it simultaneously demodulates the CCW signal and the CW signal, and then uses the differential mode component of CCW and CW as the input control signal of the current closed loop, while using the common mode component of CCW and CW as the gyroscope output signal (at this time, it is the signal before the square wave current signal compensation). Compared with the traditional single signal closed loop and single signal output scheme, it has better dynamic response capability and anti-interference advantage. Compared with the "common mode control and differential mode output" scheme, it not only realizes the compensation function, but also can jointly suppress the common mode and differential mode intensity noise, and achieve a significant improvement in the accuracy of silicon photonic gyroscope.

[0136] (4) Determine whether the differential mode component is 0. If it is 0, it means that the differential mode components of CCW and CW have achieved a steady lock on the resonant frequency of the waveguide resonant cavity. At this time, the square wave current signal maintains its current value. If it is not 0, it means that the square wave current signal needs to be tuned.

[0137] (5) Determine the positive and negative values ​​of the differential mode component. If the value is greater than 0, perform down-tuning of the square wave current signal. If the value is less than 0, perform up-tuning of the square wave current signal. During this process, calculate the gyroscope output error caused by intensity changes.

[0138] (6) Through multiple closed-loop control, the center frequency of the laser is steadily locked to the resonant frequency of the waveguide resonant cavity, and the square wave current signal no longer changes and remains at its current value.

[0139] (7) Perform strength compensation modeling and obtain strength compensation parameters in the gyroscope closed-loop and compensation parameter calculation module: based on the measured current-intensity tuning coefficient K of the silicon-based resonant cavity. P-i And the difference σ between the current driving current (i.e., the current input square wave current signal) i and the initial current (i.e., the bias current 110mA). i Establish strength compensation parameter A P With σ i K P-i Relationship: A P =k1×K P-i ×σ i Where k1 is the measured strength error constant;

[0140] (8) Perform frequency compensation modeling and obtain frequency compensation parameters in the gyroscope closed-loop and compensation parameter calculation module: based on the measured current-frequency tuning coefficient K of the silicon-based resonant cavity. f-i And the difference σ between the current drive current i and the initial current (110mA). i Establish frequency compensation parameter A f With σ i K f-i Relationship: A f =k2×K f-i ×σ i , where k2 is the measured frequency error constant;

[0141] (9) Incorporating intensity compensation parameter A into the silicon photonic gyroscope compensation module P and frequency compensation parameter A f Based on the current driving current i, a quadratic term fitting and real-time compensation are performed on the zero position of the gyroscope output to obtain the final gyroscope output. The compensated gyroscope output is: D 补偿后 =D 补偿前 +iA p +iA f .

[0142] It should be noted that, for ease of calculation, the differential mode component in this embodiment is the CW signal minus the CCW signal.

[0143] The silicon photonic gyroscope provided by this invention adopts a gyroscope closed-loop and accuracy improvement scheme based on "common-differential mode noise suppression structure + error compensation", and its specific features are as follows:

[0144] (1) Differential mode locking technology is adopted. By comparing the zero-crossing of the differential mode components, the tuning direction of the square wave current signal is determined. Under this condition, the square wave current signal has the following two advantages: ① It does not require large-range tuning but only requires a small change in current, which reduces the intensity change introduced by the current to a certain extent and realizes the reduction of common mode intensity noise; ② The differential mode component is used to control the change of the square wave current signal. At this time, the reciprocity error introduced by the change of ambient temperature due to optical path loss, extinction ratio, etc. will not affect the closed-loop feedback tuning of the square wave current signal, thereby improving the dynamic response capability and anti-interference advantage of the closed-loop system.

[0145] (2) The output method of "common mode + compensation parameter correction" is adopted. The gyroscope output is solved by common mode components, which can effectively suppress external differential mode intensity errors (such as Kerr noise). Taking the change of optical path loss after Y branch as an example, if the splitting ratio of Y branch changes due to changes in ambient temperature, if the traditional CCW signal demodulation output mode is used, the Kerr error introduced by the difference in splitting ratio will change irregularly with temperature changes, which is difficult to suppress effectively and causes gyroscope error; however, after using common mode demodulation output, the fluctuation of the splitting ratio of Y branch will not cause changes in common mode components, and the Kerr error will be completely suppressed.

[0146] The features described and / or illustrated above with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, and / or in combination with or in lieu of features in other embodiments.

[0147] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, components, or combinations thereof.

[0148] Many features and advantages of these embodiments are apparent from this detailed description, and therefore the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since many modifications and alterations will readily occur to those skilled in the art, the embodiments of the invention are not intended to be limited to the precise structures and operations illustrated and described, but rather to encompass all suitable modifications and equivalents falling within their scope.

[0149] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0150] The parts of this invention not described in detail are techniques known to those skilled in the art.

Claims

1. A fully integrated monolithic silicon photonic gyroscope, characterized in that, include A silicon photonic chip includes a laser, a Y-branch, couplers C1, C2, and C3, a waveguide resonant cavity, and detectors PD1, PD2, PD3, and PD4. Couplers C1, C2, and C3 are all 2x2 couplers. The laser output is connected to the Y-branch input. The two outputs of the Y-branch are connected to ports a of couplers C1 and C2, respectively. Ports b of couplers C1 and C2 are connected to ports a and b of coupler C3, respectively. Ports c and d of coupler C3 are connected to the two input and output ports of the waveguide resonant cavity, respectively. Port c of couplers C1 and C2 is connected to detectors PD1 and PD2, respectively. Port d of couplers C1 and C2 is connected to detectors PD3 and PD4, respectively. Detectors PD1 and PD2 are used to detect the resonant signal of the waveguide resonant cavity, and detectors PD3 and PD4 are used to detect the intensity change of the laser output light signal. An ASIC circuit is included, comprising a current control module and a speed demodulation and compensation module. The current control module determines the square wave current signal parameters based on the measured parameters of the waveguide resonant cavity and tunes the square wave current signal based on the differential mode components of the clockwise and counterclockwise resonant signals. The speed demodulation and compensation module calculates the measured parameters of the waveguide resonant cavity based on the voltage signals detected by each detector, calculates the differential mode and common mode components of the clockwise and counterclockwise resonant signals, calculates the intensity compensation parameters and frequency compensation parameters, and calculates the gyroscope output.

2. The silicon photonic gyroscope according to claim 1, characterized in that, The silicon photonic gyroscope also includes a temperature control signal module, which is used to linearly scan the temperature of the laser and adjust the center frequency of the laser to be within the resonant valley frequency range of the counterclockwise resonant signal of the waveguide resonant cavity.

3. The silicon photonic gyroscope according to claim 1, characterized in that, The speed demodulation and compensation module specifically includes the following unit: a resonant cavity measured parameter calculation unit, used to calculate the measured parameters of the waveguide resonant cavity based on the voltage signals detected by each detector. The measured parameters include the overall transmission loss, current-power tuning coefficient, current-frequency tuning coefficient, and optical path intensity attenuation coefficient. The CW demodulation unit is used to demodulate the output clockwise resonant signal to obtain a digital signal; The CCW demodulation unit is used to demodulate the output counterclockwise resonant signal to obtain a digital signal. The differential mode calculation unit is used to perform difference calculations on clockwise and counterclockwise resonant signals to obtain the differential mode components. The common-mode calculation unit is used to sum the clockwise and counterclockwise resonant signals to obtain the common-mode components; The gyroscope closed-loop and parameter compensation calculation unit is used to calculate the intensity compensation parameters and frequency compensation parameters based on the differential mode components and measured parameters. The noise compensation unit is used to calculate the gyroscope output based on the common-mode component, combined with intensity compensation parameters and frequency compensation parameters.

4. A noise suppression method for a fully integrated monolithic silicon photonic gyroscope, characterized in that, The method using the silicon photonic gyroscope according to any one of claims 1 to 3 includes the following steps: Design a square wave current signal for the input laser, wherein the design parameters of the square wave current signal include frequency, tuning range, and amplitude; When the ASIC circuit is powered on, the set square wave current signal is applied to the laser. After determining that the counterclockwise resonant signal has entered a valley, the clockwise and counterclockwise resonant signals are demodulated, and the differential-mode components and common-mode components of the clockwise and counterclockwise resonant signals are calculated. The differential-mode component is the clockwise resonant signal minus the counterclockwise resonant signal. If the differential mode component is determined to be 0, the control square wave current signal is kept at its current value. If the differential mode component is greater than 0, the square wave current signal is controlled to be tuned down; if the differential mode component is less than 0, the square wave current signal is controlled to be tuned up. Through multiple tuning processes, the center frequency of the laser is steadily locked to the resonant frequency of the waveguide resonant cavity, ensuring that the square wave current signal remains unchanged.

5. The method according to claim 4, characterized in that, The square wave current signal design method includes the following steps: S101. The frequency of the square wave current signal is designed to be greater than the relative intensity noise frequency of the laser and less than the upper limit of the laser tuning bandwidth frequency. S102. Determine the optimal current tuning region of the laser and set the bias current to the median value of the optimal current tuning region of the laser. The upper and lower extreme values ​​of the tuning range are determined based on the maximum free spectral width of the square wave current signal covering at least one waveguide resonant cavity. S103. Determine the amplitude of the square wave current signal based on the gyroscope's maximum sensitivity.

6. The method according to claim 5, characterized in that, The upper and lower extrema of the tuning range are set as follows: , ,but ,in, This refers to the frequency-current tuning coefficient of the laser. FSR This represents the maximum free spectral linewidth.

7. The method according to claim 5, characterized in that, Step S103 includes the following steps: The laser is input with a set bias current, and the voltage of the laser after passing through coupler C1 and coupler C2 is collected to calculate the total transmission loss of coupler C1 and coupler C2; the laser is input with a set bias current, and the output voltage of detector PD1 and detector PD2 is collected to calculate the optical path intensity attenuation coefficient. A sawtooth wave current signal with a frequency of 1Hz is input to the laser. The output voltage of detector PD3 is collected, and the current-intensity tuning coefficient is calculated. A sawtooth wave current signal with a frequency of 1Hz is input to the laser. The output voltage of detector PD1 is collected, and the current-frequency tuning coefficient is calculated. The gyroscope sensitivity is ,in, The amplitude of the square wave current signal. The total transmission loss of coupler C1 and coupler C2 is given. , These are the current-intensity tuning coefficient and the current-frequency tuning coefficient, respectively, and A is the optical path intensity attenuation coefficient; Adjust the gyroscope sensitivity to Take the derivative, let The amplitude of the square wave current signal is obtained.

8. The method according to claim 7, characterized in that, The formula for calculating the overall transmission loss is as follows: ,in, , These are the transresistivity and current responsivity of detector PD3, respectively. , These are the transresistivity and current responsivity of detector PD4, respectively. The photoelectric voltage of detectors PD3 and PD4. , These are the voltages of the laser under steady-state conditions detected by detectors PD3 and PD4, respectively. The output power of the laser under steady-state conditions; the optical path intensity attenuation coefficient is calculated as follows: ,in, , These are the transresistivity and current responsivity of detector PD1, respectively. These represent the transresistivity and current responsivity of detector PD2, respectively. The photoelectric voltage of detectors PD1 and PD2. These are the voltages of the laser under steady-state conditions detected by detectors PD1 and PD2, respectively. This refers to the output power of the laser under steady-state conditions. The current-intensity tuning coefficient is calculated as follows: ,in, These represent the minimum and maximum values ​​of the sawtooth wave current signal, respectively. These are the corresponding detectors detected by PD3. voltage, These are the transresistivity and current responsivity of detector PD3, respectively. The current-frequency tuning coefficient is calculated as follows: Where c is the speed of light, n is the refractive index of the waveguide resonant cavity, and L is the cavity length of the waveguide resonant cavity. and These are the currents corresponding to two adjacent resonant signals detected by detector PD1.

9. The method according to claim 8, characterized in that, The square wave current signal design method also includes the following steps: Calculate strength compensation parameters: Where k1 is the strength error constant, The difference between the current drive current and the initial current. This refers to the current-intensity tuning factor; Calculate frequency compensation parameters: Where k2 is the frequency error constant, This refers to the current-frequency tuning coefficient. The calculated gyroscope output after compensation is: ,in, i This represents the current drive current.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The processor executes the computer program to implement the method described in any one of claims 4 to 9.

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