CN114935397A - Laser vibration measurement optical integrated chip and method for time-sharing calibration frequency drift - Google Patents
Laser vibration measurement optical integrated chip and method for time-sharing calibration frequency drift Download PDFInfo
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Abstract
The invention discloses a laser vibration measurement optical integrated chip and a method for calibrating frequency drift in time division, belonging to the technical field of photoelectric communication. The device comprises a laser, an integrated optical chip, a data processing module, a laser drive and a transmitting lens; the integrated optical chip comprises a first coupler, a first beam splitter, a first phase shifter, a frequency mixer, a Mach-Zehnder structure, a second beam combiner, a first beam combiner and a second coupler. The beam is directly split by the on-chip beam splitter, so that the integration level is higher, other extra devices such as optical fibers are not needed, the packaging is facilitated, and the size miniaturization of the whole system is facilitated; the frequency drift of the laser can be subjected to time division multiplexing, and frequency drift calculation and compensation are performed without additional beam splitting, so that the power consumption of a system is reduced; the frequency drift compensation of the laser is carried out without an additional frequency mixer or an interference light path and the like, and the size of a chip is further reduced, so that the technical effects of low power consumption, small size, high integration level and lower cost are achieved, and meanwhile, the frequency drift time-sharing calibration of the laser is realized.
Description
Technical Field
The invention relates to the technical field of photoelectric communication, in particular to a laser vibration measurement optical integrated chip and a method for calibrating frequency drift in a time-sharing manner.
Background
Vibration characterization is an important means of identifying reliability, and different sensing techniques should be utilized for different monitoring purposes. The most common vibration sensor is an acceleration sensor, which has low cost and high reliability, but belongs to contact measurement, and must be attached to the surface of an object to be measured, each monitoring point needs an acceleration sensor, and absolute measurement can be performed only by performing accurate calibration. In addition, the calibration of the acceleration sensor is also susceptible to the change of the ambient temperature, and the inevitable mechanical resonance limits the measurement bandwidth. While non-contact measurements are made by microphones or other acoustic sensing elements, the effects of mechanical resonance on bandwidth are still not eliminated and there is a possibility that environmental noise or noise emitted by non-monitored parts will annihilate the useful signal. With the rapid development of laser and optical fiber technologies, it is now possible to design a new type of closed optical path laser doppler vibration sensor to overcome the inherent disadvantages of the vibration sensor and to expand the application range, including the detection of micro-fracture of bedrock during the induction phase of earthquake, where such extremely small vibrations are difficult to detect.
The laser Doppler vibration measurement system irradiates a laser beam on the surface of a rough target, and analyzes Doppler frequency modulation information generated by target vibration by detecting the phase difference between an echo beam and a local oscillation beam, so that physical quantities such as displacement, speed and the like of the target vibration are obtained. This sensor is a non-contact measuring instrument because, without mass coupling, the sensor has no effect on the vibration characteristics of the object. Furthermore, such sensors have no mechanical moving parts, eliminating the inherent resonance that limits the measurement bandwidth.
Patent application No. 201911284902.1 adopts on-chip delay interferometer and mixing receiving method to compensate laser wavelength drift, but this patent does not explain the inside concrete structure mode of chip, and delay interferometer passes through the waveguide and is connected with off-chip laser, and the integrated level is not high, need carry out the light path coupling to delay interferometer off-chip, has increased system integration process step and the volume still can be great.
In addition, the on-chip delay interferometer needs to be split by the laser, namely, the method equivalently improves the total power consumption required by the laser and also improves the relative intensity noise of a coherent detection light path part.
The existing laser Doppler vibration detection equipment is generally designed and produced on the basis of free space optical path or optical fiber optical path transmission, a discrete optical crystal device or an optical fiber optical device is adopted to build a Michelson interferometer or Mach-Zehnder interferometer structure, the size is large, the cost is high, a laser with a narrow line width is required to be adopted to improve the coherence length of a system in order to achieve high sensitivity and accuracy, and the cost of the system is further improved.
In addition, in the long-term working process of the existing laser Doppler vibration measurement equipment, the working wavelength of a laser can drift along with time, and the accuracy of the system is influenced.
In order to solve the problems of large volume and high cost of the current high-precision laser Doppler vibration measurement equipment, the light output by the laser is directly split by the on-chip beam splitter, the integration level is higher, other additional devices such as optical fibers are not needed, the packaging is facilitated, and the volume miniaturization of the whole system is facilitated; the frequency drift of the laser can be subjected to time division multiplexing, and frequency drift calculation and compensation are performed without additional beam splitting, so that the power consumption of a system is reduced; the frequency drift compensation of the laser is not needed to be carried out by an additional frequency mixer or an interference light path, and the size of a chip is further reduced, so that the technical effects of low power consumption, small size, high integration level and lower cost are achieved, and the frequency drift time-sharing calibration of the laser is realized.
Disclosure of Invention
Aiming at the problems, the laser vibration measurement optical integrated chip for time-sharing frequency drift calibration is provided, and is characterized in that: the device comprises a laser, an integrated optical chip, a data processing module, a laser drive and a transmitting lens; the integrated optical chip comprises a first coupler, a first beam splitter, a first phase shifter, a frequency mixer, a Mach-Zehnder structure, a second beam combiner, a first beam combiner and a second coupler. The beam is directly split by the on-chip beam splitter, so that the integration level is higher, other extra devices such as optical fibers are not needed, the packaging is facilitated, and the size miniaturization of the whole system is facilitated; the frequency drift of the laser can be subjected to time division multiplexing, and frequency drift calculation and compensation are performed without additional beam splitting, so that the power consumption of a system is reduced; the frequency drift compensation of the laser is not needed to be carried out by an additional frequency mixer or an interference light path, and the size of a chip is further reduced, so that the technical effects of low power consumption, small size and high integration level are achieved, and the frequency drift time-sharing calibration of the laser is realized.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows.
The utility model provides a laser vibration measurement optical integrated chip that time sharing calibration frequency was floated which characterized in that: the device comprises a laser, an integrated optical chip, a data processing module, a laser drive and a transmitting lens; the integrated optical chip comprises a first coupler, a first beam splitter, a first phase shifter, a frequency mixer, a Mach-Zehnder structure, a second beam combiner, a first beam combiner and a second coupler; laser output by the laser sequentially enters the integrated optical chip and the emitting lens and then is focused on the surface of the vibrating object, and a vibration signal beam reflected by the surface of the vibrating object is received and processed by the integrated optical chip and then demodulated by the data processing module to obtain a vibration signal; when the laser vibration measurement system generates frequency drift under the influence of continuous work or severe environment, the wavelength drift calibration is carried out through the Mach-Zehnder structure and the first reference light, the laser drive is adjusted after the processing of the data processing module, and the stability of the central frequency of the laser is realized.
Preferably, the laser and the emission lens are respectively connected with the first coupler and the second coupler through optical fiber or free space coupling.
Preferably, the mach-zehnder structure includes a second beam splitter, a second phase shifter, and a third beam splitter.
Preferably, an input end of the second beam splitter is connected with an output end of the first phase shifter through a waveguide, and the laser is split into second reference light and second signal light through the second beam splitter; the second reference light is directly connected with the beam splitter in three phases through the waveguide; and the second signal light is sequentially connected with the second phase shifter and the third beam splitter through the waveguide.
Preferably, laser output by the laser is coupled into the chip through the first coupler, and is split by the beam splitter to form first reference light and first signal light, and the first reference light is directly output to one input end of the mixer through the waveguide; the first signal light enters the Mach-Zehnder structure after passing through the first phase shifter, is divided into three beams by the beam splitter inside the Mach-Zehnder structure, is directly output to the second beam combiner through one output end of the third beam splitter, and is finally output to the other input end of the frequency mixer.
Preferably, the other output end of the third beam splitter is sequentially connected with the first beam combiner, the second coupler and the transmitting lens, and finally output to the surface of the vibrating object through the transmitting lens, the vibrating signal beam reflected by the surface of the vibrating object is coupled into the chip through the second coupler, and output to the other input end of the frequency mixer after passing through the first beam combiner and the second beam combiner, and is mixed with the first reference light and output to the data processing module, and the data processing module demodulates and acquires the vibrating signal.
Preferably, signal light output by the third beam splitter passes through the first beam combiner and then all reaches the second coupler; at this time, the signal light cannot be output to the second beam combiner through the first beam combiner.
Preferably, the phase shifter I and the phase shifter II adopt tunable phase shifters.
Preferably, the first phase shifter and the second phase shifter adopt a thermally tuned phase shifter.
Preferably, the first phase shifter adopts a time-delay waveguide structure.
Preferably, the laser vibration measurement method for calibrating the frequency drift in time division is characterized by comprising the following steps of:
s1: the length of the first phase shifter is L, and the first phase shifter has the function that when the first reference light reaches the mixer and the first signal light directly reaches the mixer after passing through the third beam splitter and the second beam splitter, the phase difference between the two paths of light is as follows:
wherein k =0,1,2 … …;
assuming a laser center frequency off 0 Then, there are:
whereinnIs the equivalent refractive index of the waveguide,cis the speed of light in vacuum.
S2: when the laser vibration measurement system works under the conditions of vibration measurement or stable and appropriate external environment, phase shift tuning is carried out on the second phase shifter, and meanwhile, the phase difference between the second signal light and the second reference light meets the following conditions:
at the moment, the second beam splitter, the second phase shifter and the third beam splitter, namely the connecting waveguides among the devices, form a Mach-Zehnder interferometer structure together, and the condition of constructive (or destructive) interference is met, at the moment, all light output by the third beam splitter reaches the first beam combiner, and is output through the second coupler for vibration measurement.
S3: the central wavelength of the laser drifts due to continuous work or external severe environment, at the moment, phase shift tuning is carried out on the second phase shifter, and meanwhile, the phase difference between the second signal light and the second reference light meets the following conditions:
at the moment, the second beam splitter, the second phase shifter and the third beam splitter, namely the connecting waveguides among the devices, form a Margard interferometer structure together, the interference cancellation (or constructive) condition is met, light output by the third beam splitter is input to the mixer through the second beam combiner, and meanwhile wavelength drift calculation calibration is carried out on the light and the first reference light.
S4: assuming a center frequency drift ofδIn the normal caseδIs a minimum value; of signals of the I and Q paths output in said mixerThe phase difference will deviate from the original phase difference
The offset phase is:
according to the demodulation principle of the mixer, the difference of the output IQ two paths of signals is as follows:
the relationship between the amount of laser center frequency drift and the mixer output can be obtained:
the two paths of signals output by the second frequency mixer are respectively as follows:
therefore, the method comprises the following steps:
determining the center frequency shift of the laser from the output of the mixer according to the above formulaδAnd the post-processing module adjusts the current driven by the laser or the internal temperature control mode of the laser according to the obtained result, so that the central frequency of the laser is maintained stable.
Preferably, the vibration measurement method based on the laser optical integrated chip is characterized by comprising the following steps.
S1: suppose that the vibration displacement of the measurement object is s: (t) Then it causes a phase change of:
wherein λ is the laser wavelength.
S2: the optical power output by the four ports in the mixer can be expressed as:
wherein,
the phase modulation signal of the second phase shifter has a modulation frequency usually much larger than the vibration frequency.
S3: subtracting the signals of four ports in the frequency mixer pairwise to obtain IQ two-path signals respectively, then dividing the subtracted signals, and demodulating phase information by performing arc tangent operation:
separable by filtering, wavelet decomposition, or the like
And the vibration displacement of the object can be restored to be s (by a conversion formula)t)。
Due to the adoption of the technical scheme, the invention has the following beneficial effects.
1. The invention carries out direct beam splitting through the on-chip beam splitter, has higher integration level, does not need other additional devices such as optical fibers and the like, is more beneficial to packaging, and achieves the technical effect of miniaturization of the whole laser vibration measurement system.
2. The frequency drift of the laser is subjected to time division multiplexing, and frequency drift calculation and compensation are performed without additional beam splitting, so that the technical effect of reducing the power consumption of a system is achieved.
3. The invention does not need an additional mixer or an interference light path and the like to carry out laser frequency drift compensation, further reduces the chip size, thereby achieving the technical effects of low power consumption, small volume, high integration level and lower cost, and simultaneously realizing the frequency drift time-sharing calibration of the laser.
Drawings
The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention, from which other drawings may be derived by those of ordinary skill in the art without inventive faculty.
Fig. 1 is a schematic structural view of the vibration measuring system.
FIG. 2 is a schematic diagram of an integrated optical chip.
In the figure, a 1-laser, a 2-integrated optical chip, a 21-coupler I, a 22-beam splitter I, a 23-mixer, a 24-beam combiner II, a 25-phase shifter I, a 26-beam splitter II, a 27-beam splitter III, a 28-beam combiner I, a 29-coupler II, a 210-phase shifter II, a 3-transmitting lens, a 4-data processing module and a 5-laser drive are arranged.
Detailed Description
The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.
Example 1:
the schematic structural diagram of the laser vibration measurement system for time-sharing calibration frequency drift as shown in fig. 1 includes a laser 1, an integrated optical chip 2, a data processing module 4, a laser driver 5, and an emission lens 3; as shown in fig. 2, an integrated optical chip for time-division calibration of frequency drift includes a first coupler 21, a first beam splitter 22, a first phase shifter 25, a mixer 23, a mach-zehnder structure, a second beam combiner 24, a first beam combiner 28, and a second coupler 29; the laser output by the laser 1 sequentially enters the integrated optical chip 2 and the transmitting lens 3 and then is focused on the surface of the vibrating object, and after the vibration signal beam reflected by the surface of the vibrating object is received and processed by the integrated optical chip 2, the vibration signal is demodulated and obtained by the data processing module 4; when the laser vibration measurement system generates frequency drift under the influence of continuous work or severe environment, the wavelength drift calibration is carried out through the Mach-Zehnder structure and the first reference light, the laser drive is adjusted after the processing of the data processing module 4, and the stability of the central frequency of the laser 1 is realized.
The laser 1 and the transmitting lens 3 are respectively connected with the first coupler 21 and the second coupler 29 through optical fiber or free space coupling.
The Mach-Zehnder structure comprises a second beam splitter 26, a second phase shifter 210 and a third beam splitter 27; the input end of the second beam splitter 26 is connected with the output end of the first phase shifter 25 through a waveguide, and the laser is split into second reference light and second signal light through the second beam splitter 26; the second reference light is directly connected with the third beam splitter 27 through a waveguide; the second signal light is connected to the second phase shifter 26 and the third beam splitter 27 in this order through a waveguide.
Laser output by the laser 1 is coupled into the integrated optical chip 2 through a first coupler 21, and is split by a first beam splitter 21 to form first reference light and first signal light, wherein the first reference light is directly output to one input end of the mixer 23 through a waveguide; the first signal light enters the Mach-Zehnder structure after passing through the first phase shifter 25, is split by the third beam splitter 27 inside the Mach-Zehnder structure, is directly output to the second beam combiner 24 through one output end of the third beam splitter 27, and is finally output to the other input end of the frequency mixer 23; the other output end of the third beam splitter 27 is sequentially connected with the first beam combiner 28, the second coupler 29 and the transmitting lens 3, and finally output to the surface of the vibrating object through the transmitting lens 3, the vibrating signal beam reflected by the surface of the vibrating object is coupled into the integrated optical chip 2 through the second coupler 29, and output to the other input end of the frequency mixer 23 after passing through the first beam combiner 28 and the second beam combiner 24, and is mixed with the first reference light and output to the data processing module 4, and the data processing module 4 demodulates and obtains the vibrating signal.
In addition, signal light output by the third beam splitter 27 passes through the first beam combiner 22 and then all reaches the second coupler 29; at this time, the signal light cannot be output to the second beam combiner 24 through the first beam combiner 28; the first phase shifter 25 and the second phase shifter 210 adopt tunable phase shifters, preferably thermal tunable phase shifters; the first phase shifter 25 adopts a time delay waveguide structure.
When the laser vibration measurement system carries out vibration measurement, namely the laser 1 starts to work or is in a stable and proper condition, light generated by the laser 1 is coupled into the integrated optical chip 2 through the first coupler 21 and is split into first signal light and first reference light through the first beam splitter 22, and the first reference light is directly output to one input end of the mixer 23; the first signal light enters the Mach-Zehnder structure after passing through the first phase shifter 25, namely enters the second beam splitter 26, and is split by the second beam splitter 26 to form second reference light and second signal light, the second reference light is directly output to one input end of the third beam splitter 27 through the waveguide, and the second signal light sequentially enters the other input end of the third beam splitter 27 through the second phase shifter 210 through the waveguide.
At this time, all the signal light of the third beam splitter 27 is output to the first beam combiner 28, enters the second coupler 29 after passing through the first beam combiner 28, is coupled to the outside of the integrated optical chip 2 by the second coupler 29, is output to the surface of the vibrating object after passing through the transmitting lens 3, is simultaneously coupled to the inside of the integrated optical chip 2 by the second coupler 29 through the surface reflection of the vibrating object, is output to the other input end of the mixer 23 through the first beam combiner 28 and the second beam combiner 24, is mixed with the first reference light and is output to the data processing module 4, and the data processing module 4 obtains the vibration signal of the vibrating object through demodulation.
When the laser vibration measurement system performs frequency drift calibration, that is, the laser 1 continues to operate for a period of time or the center frequency of the laser 1 drifts under a severe external environment. At this time, light generated by the laser 1 is coupled into the integrated optical chip 2 through the first coupler 21, and is split into first signal light and first reference light through the first beam splitter 22, and the first reference light is directly output to one input end of the mixer 23; the first signal light enters the Mach-Zehnder structure after passing through the first phase shifter 25, namely enters the second beam splitter 26, and is split by the second beam splitter 26 to form second reference light and second signal light, the second reference light is directly output to one input end of the third beam splitter 27 through the waveguide, and the second signal light sequentially enters the other input end of the third beam splitter 27 through the second phase shifter 210 through the waveguide.
At this time, all signal light of the third beam splitter 27 enters the second beam combiner 24 and is output to the mixer 23, the signal light and the first reference light are subjected to wavelength drift calibration, a central frequency drift value of the laser 1 is obtained after calibration processing and calculation and is output to the data processing module 4, the data processing module 4 adjusts current driven by the laser 1 or an internal temperature control mode of the laser 1 according to the obtained central frequency drift value of the laser 1 to regulate and control the central frequency of the laser 1, and therefore the stability of the central frequency of the laser 1 is achieved.
Example 2:
a laser vibration measurement method for calibrating frequency drift in time division is characterized by comprising the following steps.
S1: the length of the first phase shifter 25 is L, and the first phase shifter 25 is used for making the phase difference between the first reference light and the first signal light when the first reference light reaches the mixer 23 and when the first signal light directly reaches the mixer 23 after passing through the third beam splitter 27 and the second beam splitter 26:
wherein k =0,1,2 … …;
suppose that the laser 1 has a center frequency off 0 Then, there are:
whereinnIs the equivalent refractive index of the waveguide,cis the speed of light in vacuum.
S2: when the laser vibration measurement system works under the conditions of vibration measurement or stable and appropriate external environment, the phase shift tuning is carried out on the second phase shifter 210, and meanwhile, the phase difference between the second signal light and the second reference light meets the following requirements:
at this time, the second beam splitter 26, the second phase shifter 210 and the third beam splitter 27, that is, the connecting waveguides among the devices, together form a mach-zehnder interferometer structure, and the constructive (or destructive) condition of interference is satisfied, at this time, the light output by the third beam splitter 27 will all reach the first beam combiner 28, and is coupled and output through the second coupler 29 for vibration measurement.
S3: the central wavelength of the laser 1 drifts due to continuous work or the external severe environment, at this time, the second phase shifter 210 is phase-shifted and tuned, and the phase difference between the second signal light and the second reference light satisfies the following conditions:
(or), wherein m =0,1,2 … …;
at this time, the second beam splitter 26, the second phase shifter 210 and the third beam splitter 27, that is, the connecting waveguides among the devices, together form a markedler interferometer structure, and satisfy the interference cancellation (or constructive) condition, and the light output by the third beam splitter 27 is all input to the mixer 23 through the second beam combiner 24, and is calibrated by wavelength drift calculation with the first reference light.
S4: assuming a center frequency drift ofδIn the normal caseδIs a minimum value; the phase difference between the I and Q signals output from the mixer 23 will be different from the original phase difference
The offset phase is:
according to the demodulation principle of the mixer 23, the difference of the output IQ signals is as follows:
the relationship between the amount of shift in the center frequency of the laser 1 and the output of the mixer 23 can be obtained:
the two output signals of the mixer 23 are respectively:
therefore, the method comprises the following steps:
the central frequency shift of the laser 1 is determined from the result output from the mixer 23 according to the above formulaδAnd the post-processing module adjusts the current driven by the laser 1 or the internal temperature control mode of the laser 1 according to the obtained result, so that the central frequency of the laser 1 is stable.
Example 3:
a vibration measurement method based on a laser optical integrated chip is characterized by comprising the following steps.
S1: suppose that the vibration displacement of the measurement object is s: (t) Then it causes a phase change of:
wherein λ is the laser wavelength.
S2: the optical power output from the four ports in the mixer 23 can be expressed as:
wherein,
the phase-modulated signal from the second phase shifter 210 has a modulation frequency that is usually much greater than the oscillation frequency.
S3: subtracting the signals of the four ports in the mixer 23 by two to obtain IQ two-path signals respectively, then dividing the subtracted signals, and then performing arc tangent operation to demodulate phase information:
separable by filtering, wavelet decomposition, or the like
And the vibration displacement of the object can be restored to be s (by a conversion formula)t)。
Although the specification has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the described embodiments are not intended to limit the scope of the invention, which is defined by the claims appended hereto, as one of ordinary skill in the art will readily appreciate from the disclosure that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Claims (10)
1. The utility model provides a laser vibration measurement optical integrated chip that time sharing calibration frequency drifted which characterized in that: the device comprises a laser, an integrated optical chip, a data processing module, a laser drive and a transmitting lens; the integrated optical chip comprises a first coupler, a first beam splitter, a first phase shifter, a frequency mixer, a Mach-Zehnder structure, a second beam combiner, a first beam combiner and a second coupler; laser output by the laser sequentially enters the integrated optical chip and the emitting lens and then is focused on the surface of the vibrating object, and a vibration signal beam reflected by the surface of the vibrating object is received and processed by the integrated optical chip and then demodulated by the data processing module to obtain a vibration signal; when the laser vibration measurement system generates frequency drift under the influence of continuous work or severe environment, wavelength drift calibration is carried out on the Mach-Zehnder structure and the first reference light, laser driving is adjusted after the wavelength drift calibration is processed by the data processing module, and the stability of the central frequency of the laser is achieved.
2. The laser vibration measurement optical integrated chip for time-sharing calibration frequency drift of claim 1, wherein: the laser and the transmitting lens are respectively connected with the first coupler and the second coupler through optical fibers or free space coupling.
3. The laser vibration measurement optical integrated chip for time-sharing calibration frequency drift of claim 1, wherein: the Mach-Zehnder structure comprises a second beam splitter, a second phase shifter and a third beam splitter; the input end of the second beam splitter is connected with the output end of the first phase shifter through a waveguide, and the laser is split into second reference light and second signal light through the second beam splitter; the second reference light is directly connected with the beam splitter in three phases through the waveguide; and the second signal light is sequentially connected with the second phase shifter and the third beam splitter through the waveguide.
4. The laser vibration measurement optical integrated chip for time-sharing calibration frequency drift according to claim 2, wherein: laser output by the laser is coupled into a chip through a first coupler, and is split by a beam splitter to form first reference light and first signal light, and the first reference light is directly output to one input end of a mixer through a waveguide; and the first signal light enters the Mach-Zehnder structure after passing through the first phase shifter, is divided into three beams by the beam splitter inside the Mach-Zehnder structure, is directly output to the second beam combiner through one output end of the third beam splitter, and is finally output to the other input end of the frequency mixer.
5. The laser vibration measurement optical integrated chip for time-sharing frequency drift calibration according to claim 4, wherein: and the other output end of the third beam splitter is sequentially connected with the first beam combiner, the second coupler and the transmitting lens, and finally output to the surface of the vibrating object through the transmitting lens, a vibration signal beam reflected by the surface of the vibrating object is coupled into the chip through the second coupler, and is output to the other input end of the frequency mixer after passing through the first beam combiner and the second beam combiner, and is mixed with the first reference light and output to the data processing module, and the data processing module demodulates and acquires a vibration signal.
6. The laser vibration measurement optical integrated chip for time-sharing frequency drift calibration according to claim 5, wherein: all signal light output by the third beam splitter reaches the second coupler after passing through the first beam combiner; at this time, the signal light cannot be output to the second beam combiner through the first beam combiner.
7. The laser vibration measurement optical integrated chip for time-sharing calibration frequency drift of claim 3, wherein: the first phase shifter and the second phase shifter adopt tunable phase shifters.
8. The laser vibration measurement optical integrated chip for time-sharing calibration frequency drift according to claim 7, wherein: and the first phase shifter adopts a time delay waveguide structure.
9. A laser vibration measurement method for time-sharing calibration frequency drift is characterized by comprising the following steps:
s1: the length of the first phase shifter is L, and the first phase shifter has the function that when the first reference light reaches the mixer and the first signal light directly reaches the mixer after passing through the third beam splitter and the second beam splitter, the phase difference between the two paths of light is as follows:
wherein k =0,1,2 … …;
assuming a laser center frequency off 0 Then, there are:
whereinnIs the equivalent refractive index of the waveguide,cthe speed of light in vacuum;
s2: when the laser vibration measurement system works under the conditions of vibration measurement or stable and appropriate external environment, phase shift tuning is carried out on the second phase shifter, and meanwhile, the phase difference between the second signal light and the second reference light meets the following requirements:
at the moment, the second beam splitter, the second phase shifter and the third beam splitter, namely the connecting waveguides among the devices, form a Mach-Zehnder interferometer structure together, and the condition of constructive (or destructive) interference is met, at the moment, all light output by the third beam splitter reaches the first beam combiner, and is output through the second coupler for vibration measurement;
s3: the central wavelength of the laser drifts due to continuous work or the external severe environment, at the moment, phase shift tuning is carried out on the second phase shifter, and meanwhile, the phase difference between the second signal light and the second reference light meets the following requirements:
at the moment, the second beam splitter, the second phase shifter and the third beam splitter, namely the connecting waveguides among the devices, form a Margard interferometer structure together, and meet the interference cancellation (or constructive) condition, light output by the third beam splitter is input to the mixer through the second beam combiner, and simultaneously wavelength drift calculation calibration is carried out on the light and the first reference light;
s4: assuming a center frequency drift ofδIn the normal caseδIs a minimum value; the phase difference of the I path signal and the Q path signal output by the frequency mixer deviates from the original phase difference
The offset phase is:
according to the demodulation principle of the mixer, the difference of two paths of output IQ signals is as follows:
the relationship between the amount of laser center frequency drift and the mixer output can be obtained:
two paths of signals output by the second frequency mixer are respectively as follows:
therefore, the method comprises the following steps:
determining the center frequency shift of the laser from the output of the mixer according to the above formulaδAnd the post-processing module adjusts the current driven by the laser or the internal temperature control mode of the laser according to the obtained result, so that the central frequency of the laser is maintained stable.
10. A vibration measurement method based on a laser optical integrated chip is characterized by comprising the following steps:
s1: suppose that the vibration displacement of the measurement object is s: (t) Then it causes a phase change of:
wherein λ is the laser wavelength;
s2: the optical power output by the four ports in the mixer can be expressed as:
wherein,
the phase modulation signal of the second phase shifter is a phase modulation signal, and the modulation frequency is usually far greater than the vibration frequency;
s3: subtracting the signals of four ports in the frequency mixer pairwise to obtain IQ two-path signals respectively, then dividing the subtracted signals, and demodulating phase information by performing arc tangent operation:
separable by filtering, wavelet decomposition, or the like
And the vibration displacement of the object can be restored to be s (by a conversion formula)t)。
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