Heterodyne interference structure-based wide-range optical acceleration sensor and measurement method

Abstract

The invention relates to the technical field of optical acceleration sensors, in particular to a wide-range optical acceleration sensor based on a heterodyne interference structure and a measurement method. The sensor comprises a narrow linewidth laser, an isolator, a 1 * 2 coupler, a first acousto-optic modulator, a second acousto-optic modulator, a first 1 * 3 coupler, a second 1 * 3 coupler, a first circulator, a second circulator, a third circulator, a first optical fiber, a second optical fiber, a third optical fiber, a sensing unit, a first 2 * 1 coupler, a second 2 * 1 coupler and a third 2 * 1 coupler. A first photoelectric detector, a second photoelectric detector, a third photoelectric detector and a PC; the sensing unit comprises a base, a first measuring mirror, a second measuring mirror and a reference mirror; the back of the first measuring mirror, the back of the second measuring mirror and the back of the reference mirror are all fixed with the base. The optical acceleration sensor solves the problem that an existing optical acceleration sensor cannot achieve wide-range measurement for large acceleration, and is suitable for the fields of industrial automation, intelligent monitoring and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical acceleration sensor, and particularly relates to a large-range optical acceleration sensor based on a heterodyne interference structure and a measurement method. BACKGROUND

[0002] With the rapid development of industrial automation, intelligent monitoring and other fields, the demand for high-performance sensors continues to grow. Optical acceleration sensors have shown good application prospects in many fields due to their unique advantages. However, in actual application, the existing optical acceleration sensors can only achieve high-precision measurement for small acceleration due to their own structure limitations, and cannot achieve large-range measurement for large acceleration, thereby leading to limited application range. Based on this, it is necessary to invent a large-range optical acceleration sensor based on a heterodyne interference structure and a measurement method to solve the problem that the existing optical acceleration sensors cannot achieve large-range measurement for large acceleration. SUMMARY

[0003] The present application provides a large-range optical acceleration sensor based on a heterodyne interference structure and a measurement method to solve the problem that the existing optical acceleration sensors cannot achieve large-range measurement for large acceleration.

[0004] The present application is implemented by adopting the following technical solutions:

[0005] The large-range optical acceleration sensor based on the heterodyne interference structure comprises a narrow-line-width laser, an isolator, a 1x2 coupler, a first acousto-optic modulator, a second acousto-optic modulator, a first 1x3 coupler, a second 1x3 coupler, a first loop, a second loop, a third loop, a first optical fiber, a second optical fiber, a third optical fiber, a sensitive unit, a first 2x1 coupler, a second 2x1 coupler, a third 2x1 coupler, a first photodetector, a second photodetector, a third photodetector and a PC.

[0006] The sensitive unit comprises a base, a first measurement mirror, a second measurement mirror and a reference mirror; the back surface of the first measurement mirror, the back surface of the second measurement mirror and the back surface of the reference mirror are fixed to the base.

[0007] The outgoing end of the narrow-line-width laser is connected with the incoming end of the 1x2 coupler through the isolator; the two outgoing ends of the 1x2 coupler are respectively connected with the incoming end of the first acousto-optic modulator and the incoming end of the second acousto-optic modulator; the outgoing end of the first acousto-optic modulator is connected with the incoming end of the first 1x3 coupler; and the outgoing end of the second acousto-optic modulator is connected with the incoming end of the second 1x3 coupler.

[0008] The three outgoing ends of the first 1x3 coupler are respectively connected with the first port of the first loop, the first port of the second loop and the first port of the third loop.

[0009] The second port of the first circulator is connected with the head end of the first optical fiber; the tail end face of the first optical fiber is opposite to the front face of the first measuring mirror; the third port of the first circulator is connected with the first incident end of the first 2x1 coupler; the second port of the second circulator is connected with the head end of the second optical fiber; the tail end face of the second optical fiber is opposite to the front face of the second measuring mirror; the third port of the second circulator is connected with the first incident end of the second 2x1 coupler; the second port of the third circulator is connected with the head end of the third optical fiber; the tail end face of the third optical fiber is opposite to the front face of the reference mirror; the third port of the third circulator is connected with the first incident end of the third 2x1 coupler;

[0010] The three incident ends of the second 1x3 coupler are connected with the second incident end of the first 2x1 coupler, the second incident end of the second 2x1 coupler and the second incident end of the third 2x1 coupler respectively.

[0011] The incident end of the first 2x1 coupler is connected with the incident end of the first photodetector; the incident end of the second 2x1 coupler is connected with the incident end of the second photodetector; the incident end of the third 2x1 coupler is connected with the incident end of the third photodetector; the signal output end of the first photodetector, the signal output end of the second photodetector and the signal output end of the third photodetector are connected with the signal input end of the PC.

[0012] Further, the base comprises two short elastic beams which are parallel to each other and opposite to each other, and two long elastic beams which are parallel to each other and opposite to each other.

[0013] The first mass block is fixed between the inner side faces of the head ends of the two short elastic beams; the first connecting block is fixed between the inner side faces of the tail ends of the two short elastic beams; the tail ends of the two long elastic beams are flush with the tail ends of the two short elastic beams; the head ends of the two long elastic beams exceed the head ends of the two short elastic beams; the second mass block is fixed between the inner side faces of the head ends of the two long elastic beams; the second connecting block is fixed between the inner side faces of the tail ends of the two long elastic beams; the third connecting block is fixed between the outer side face of the tail end of the second short elastic beam and the outer side face of the tail end of the first long elastic beam.

[0014] The back face of the first measuring mirror is fixed with the outer side face of the head end of the first short elastic beam; the back face of the second measuring mirror is fixed with the outer side face of the head end of the first long elastic beam; the back face of the reference mirror is fixed with the outer side face of the tail end of the first short elastic beam.

[0015] Further, the two short elastic beams, the two long elastic beams, the first mass block, the second mass block, the first connecting block, the second connecting block and the third connecting block are made of fused quartz.

[0016] Further, the splitting ratio of the 1x2 coupler is 50:50; the splitting ratio of the first 1x3 coupler and the splitting ratio of the second 1x3 coupler are all 33.3:33.3:33.3.

[0017] Further, the first measurement mirror, the second measurement mirror and the reference mirror are all plane high-reflectivity mirrors.

[0018] The method is realized by using the following steps:

[0019] First, the sensor is controlled to enter a working mode; the working mode is specifically:

[0020] The laser emitted by the narrow-line-width laser passes through the isolator for isolation and is incident on the 1x2 coupler, and is split into two optical signals with equal power by the 1x2 coupler; the two optical signals are shifted in frequency by the first acousto-optic modulator and the second acousto-optic modulator respectively to form two optical signals with different frequencies: the first optical signal is incident on the first 1x3 coupler and is split into three optical signals with equal power by the first 1x3 coupler; the second optical signal is incident on the second 1x3 coupler and is split into three optical signals with equal power by the second 1x3 coupler;

[0021] The first optical signal split by the first 1x3 coupler is incident on the first measurement mirror through the first optical fiber and the first circulator in sequence, and forms a first reflected optical signal after being reflected by the first measurement mirror; the first reflected optical signal is incident on the first 2x1 coupler through the first optical fiber and the first circulator in sequence; the first optical signal split by the second 1x3 coupler is incident on the first 2x1 coupler and interferes with the first reflected optical signal in the first 2x1 coupler to form a first beat frequency optical signal; the first beat frequency optical signal is incident on the first photodetector and is converted into a first electrical signal by the first photodetector and then transmitted to the PC;

[0022] The second optical signal split by the first 1x3 coupler is incident on the second measurement mirror through the second optical fiber and the second circulator in sequence, and forms a second reflected optical signal after being reflected by the second measurement mirror; the second reflected optical signal is incident on the second 2x1 coupler through the second optical fiber and the second circulator in sequence; the second optical signal split by the second 1x3 coupler is incident on the second 2x1 coupler and interferes with the second reflected optical signal in the second 2x1 coupler to form a second beat frequency optical signal; the second beat frequency optical signal is incident on the second photodetector and is converted into a second electrical signal by the second photodetector and then transmitted to the PC;

[0023] The third light signal branched by the first 1x3 coupler is sequentially incident to the reference mirror through the third circulator and the third optical fiber, and forms a third reflected light signal after being reflected by the reference mirror; the third reflected light signal is sequentially incident to the third 2x1 coupler through the third optical fiber and the third circulator; the third light signal branched by the second 1x3 coupler is incident to the third 2x1 coupler, and interferes with the third reflected light signal in the third 2x1 coupler to form a third beat frequency light signal; the third beat frequency light signal is incident to the third photodetector, and is converted into a third electric signal by the third photodetector and then transmitted to the PC;

[0024] In the working mode, the tail end face of the first optical fiber and the front face of the first measurement mirror jointly constitute a first F-P resonant cavity, the tail end face of the second optical fiber and the front face of the second measurement mirror jointly constitute a second F-P resonant cavity, and the tail end face of the third optical fiber and the front face of the reference mirror jointly constitute a third F-P resonant cavity;

[0025] When there is no acceleration input, the cavity length of the first F-P resonant cavity, the cavity length of the second F-P resonant cavity and the cavity length of the third F-P resonant cavity remain consistent, and the phase of the first electric signal, the phase of the second electric signal and the phase of the third electric signal remain consistent;

[0026] When there is an acceleration input, the acceleration acts on the two short elastic beams to make the first mass block and the first measurement mirror vibrate in simple harmonic motion, and acts on the two long elastic beams to make the second mass block and the second measurement mirror vibrate in simple harmonic motion, thereby changing the cavity length of the first F-P resonant cavity and changing the cavity length of the second F-P resonant cavity, so as to change the phase of the first electric signal and change the phase of the second electric signal; at the same time, the cavity length of the third F-P resonant cavity remains unchanged, so that the phase of the third electric signal remains unchanged; then, the PC substitutes the phase of the first electric signal and the phase of the third electric signal into a first acceleration measurement equation of the sensor to obtain a first measurement result of the acceleration, and substitutes the phase of the second electric signal and the phase of the third electric signal into a second acceleration measurement equation of the sensor to obtain a second measurement result of the acceleration;

[0027] When the input acceleration is small, the amplitude of the second mass block and the second measurement mirror is greater than the amplitude of the first mass block and the first measurement mirror due to the smaller stiffness of the two long elastic beams than the stiffness of the two short elastic beams, so that the change amount of the cavity length of the second F-P resonant cavity is greater than the change amount of the cavity length of the first F-P resonant cavity, thereby the change amount of the phase of the second electric signal is greater than the change amount of the phase of the first electric signal, so that the accuracy of the second measurement result of the acceleration is higher than the accuracy of the first measurement result of the acceleration; at this time, the second measurement result of the acceleration is taken as the high-precision measurement result of the acceleration;

[0028] When the input acceleration is large, the amplitude of the first mass and the first measurement mirror remains normal when the amplitude of the second mass and the second measurement mirror exceeds the limit, so that the cavity length variation of the first F-P resonant cavity remains normal when the cavity length variation of the second F-P resonant cavity exceeds the limit, thereby making the phase variation of the first electric signal remain normal when the phase variation of the second electric signal exceeds the limit, so that the first measurement result of the acceleration remains within the range when the second measurement result of the acceleration exceeds the range; at this time, the first measurement result of the acceleration is taken as the large-range measurement result of the acceleration.

[0029] Further, the first acceleration measurement equation of the sensor is represented as follows:

[0030] ;

[0031] ;

[0032] In the formula: represents the displacement of the first mass; represents the phase of the first electric signal; represents the phase of the third electric signal; represents the wavelength of the laser emitted by the narrow linewidth laser; represents the first measurement result of the acceleration; represents the elastic coefficient of the short elastic beam; represents the mass of the first mass.

[0033] Further, the second acceleration measurement equation of the sensor is represented as follows:

[0034] ;

[0035] ;

[0036] In the formula: represents the displacement of the second mass; represents the phase of the second electric signal; represents the phase of the third electric signal; represents the wavelength of the laser emitted by the narrow linewidth laser; represents the second measurement result of the acceleration; represents the elastic coefficient of the long elastic beam; represents the mass of the second mass.

[0037] Further, the frequency difference of the two light signals after frequency shift is 1 MHz.

[0038] Compared with the prior optical acceleration sensor, the application adopts a brand-new structure, and on one hand, realizes high-precision measurement for smaller acceleration, and on the other hand, realizes large-range measurement for larger acceleration, so that high precision and large range are combined, thereby making the application range no longer limited.

[0039] The application effectively solves the problem that the prior optical acceleration sensor cannot realize large-range measurement for larger acceleration, and is suitable for industrial automation, intelligent monitoring and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a light path schematic diagram of the application.

[0041] Figure 2 is a plane structure schematic diagram of the sensitive unit in the application.

[0042] Figure 3 is a three-dimensional structure schematic diagram of the sensitive unit in the application.

[0043] Figure 4 is a partial structure schematic diagram of Figure 3 . Figure 1 .

[0044] Figure 5 is a partial structure schematic diagram of Figure 3 . Figure 2 .

[0045] Figure 6 is a partial structure schematic diagram of Figure 3 . Figure 3 .

[0046] In the figure: 1-narrow line width laser, 2-isolator, 3-1x2 coupler, 4a-first acousto-optic modulator, 4b-second acousto-optic modulator, 5a-first 1x3 coupler, 5b-second 1x3 coupler, 6a-first optical circulator, 6b-second optical circulator, 6c-third optical circulator, 7a-first optical fiber, 7b-second optical fiber, 7c-third optical fiber, 8a-short elastic beam, 8b-long elastic beam, 8c-first mass block, 8d-second mass block, 8e-first connecting block, 8f-second connecting block, 8g-third connecting block, 9a-first measurement mirror, 9b-second measurement mirror, 9c-reference mirror, 10a-first 2x1 coupler, 10b-second 2x1 coupler, 10c-third 2x1 coupler, 11a-first photodetector, 11b-second photodetector, 11c-third photodetector, 12-PC. DETAILED DESCRIPTION

[0047] The large-range optical acceleration sensor based on heterodyne interference structure comprises a narrow-line-width laser 1, an isolator 2, a 1*2 coupler 3, a first acousto-optic modulator 4a, a second acousto-optic modulator 4b, a first 1*3 coupler 5a, a second 1*3 coupler 5b, a first optical circulator 6a, a second optical circulator 6b, a third optical circulator 6c, a first optical fiber 7a, a second optical fiber 7b, a third optical fiber 7c, a sensing unit, a first 2*1 coupler 10a, a second 2*1 coupler 10b, a third 2*1 coupler 10c, a first photoelectric detector 11a, a second photoelectric detector 11b, a third photoelectric detector 11c, and a PC 12.

[0048] The sensing unit comprises a base, a first measurement mirror 9a, a second measurement mirror 9b, and a reference mirror 9c; the back surface of the first measurement mirror 9a, the back surface of the second measurement mirror 9b, and the back surface of the reference mirror 9c are fixed to the base.

[0049] The outgoing end of the narrow-line-width laser 1 is connected to the incoming end of the 1*2 coupler 3 through the isolator 2; the two outgoing ends of the 1*2 coupler 3 are respectively connected to the incoming end of the first acousto-optic modulator 4a and the incoming end of the second acousto-optic modulator 4b; the outgoing end of the first acousto-optic modulator 4a is connected to the incoming end of the first 1*3 coupler 5a; and the outgoing end of the second acousto-optic modulator 4b is connected to the incoming end of the second 1*3 coupler 5b.

[0050] The three outgoing ends of the first 1*3 coupler 5a are respectively connected to the first port of the first optical circulator 6a, the first port of the second optical circulator 6b, and the first port of the third optical circulator 6c.

[0051] The second port of the first optical circulator 6a is connected to the leading end of the first optical fiber 7a; the tail end surface of the first optical fiber 7a is opposite to the front surface of the first measurement mirror 9a; the third port of the first optical circulator 6a is connected to the first incoming end of the first 2*1 coupler 10a; the second port of the second optical circulator 6b is connected to the leading end of the second optical fiber 7b; the tail end surface of the second optical fiber 7b is opposite to the front surface of the second measurement mirror 9b; the third port of the second optical circulator 6b is connected to the first incoming end of the second 2*1 coupler 10b; the second port of the third optical circulator 6c is connected to the leading end of the third optical fiber 7c; the tail end surface of the third optical fiber 7c is opposite to the front surface of the reference mirror 9c; and the third port of the third optical circulator 6c is connected to the first incoming end of the third 2*1 coupler 10c.

[0052] The three outgoing ends of the second 1*3 coupler 5b are respectively connected to the second incoming end of the first 2*1 coupler 10a, the second incoming end of the second 2*1 coupler 10b, and the second incoming end of the third 2*1 coupler 10c.

[0053] The exit end of the first 2*1 coupler 10a is connected with the entrance end of the first photoelectric detector 11a; the exit end of the second 2*1 coupler 10b is connected with the entrance end of the second photoelectric detector 11b; the exit end of the third 2*1 coupler 10c is connected with the entrance end of the third photoelectric detector 11c; the signal output end of the first photoelectric detector 11a, the signal output end of the second photoelectric detector 11b, and the signal output end of the third photoelectric detector 11c are all connected with the signal input end of the PC 12.

[0054] The base comprises two mutually parallel and opposite short elastic beams 8a and two mutually parallel and opposite long elastic beams 8b.

[0055] The first mass block 8c is fixed between the inner side surfaces of the head ends of the two short elastic beams 8a; the first connecting block 8e is fixed between the inner side surfaces of the tail ends of the two short elastic beams 8a; the tail ends of the two long elastic beams 8b are flush with the tail ends of the two short elastic beams 8a; the head ends of the two long elastic beams 8b exceed the head ends of the two short elastic beams 8a; the second mass block 8d is fixed between the inner side surfaces of the head ends of the two long elastic beams 8b; the second connecting block 8f is fixed between the inner side surfaces of the tail ends of the two long elastic beams 8b; the third connecting block 8g is fixed between the outer side surface of the tail end of the second short elastic beam 8a and the outer side surface of the tail end of the first long elastic beam 8b.

[0056] The back surface of the first measuring mirror 9a is fixed with the outer side surface of the head end of the first short elastic beam 8a; the back surface of the second measuring mirror 9b is fixed with the outer side surface of the head end of the first long elastic beam 8b; the back surface of the reference mirror 9c is fixed with the outer side surface of the tail end of the first short elastic beam 8a.

[0057] The two short elastic beams 8a, the two long elastic beams 8b, the first mass block 8c, the second mass block 8d, the first connecting block 8e, the second connecting block 8f, and the third connecting block 8g are all made of fused quartz.

[0058] The splitting ratio of the 1*2 coupler 3 is 50:50; the splitting ratios of the first 1*3 coupler 5a and the second 1*3 coupler 5b are both 33.3:33.3:33.3.

[0059] The first measuring mirror 9a, the second measuring mirror 9b, and the reference mirror 9c are all plane high-reflectivity mirrors.

[0060] The large-range optical acceleration measurement method based on the heterodyne interference structure is realized by the large-range optical acceleration sensor based on the heterodyne interference structure.

[0061] First, the sensor is controlled to enter a working mode; the working mode is specifically:

[0062] The laser emitted by the narrow line width laser 1 is incident to the 1x2 coupler 3 after isolation by the isolator 2, and is divided into two optical signals with equal power by the 1x2 coupler 3; the two optical signals are shifted in frequency by the first and second acousto-optic modulators 4a and 4b respectively to form two optical signals with different frequencies; the first optical signal is incident to the first 1x3 coupler 5a and is divided into three optical signals with equal power by the first 1x3 coupler 5a; the second optical signal is incident to the second 1x3 coupler 5b and is divided into three optical signals with equal power by the second 1x3 coupler 5b;

[0063] The first optical signal divided by the first 1x3 coupler 5a is incident to the first measuring mirror 9a in sequence through the first circulator 6a and the first optical fiber 7a, and forms a first reflected optical signal after reflection by the first measuring mirror 9a; the first reflected optical signal is incident to the first 2x1 coupler 10a in sequence through the first optical fiber 7a and the first circulator 6a; the first optical signal divided by the second 1x3 coupler 5b is incident to the first 2x1 coupler 10a, and interferes with the first reflected optical signal in the first 2x1 coupler 10a to form a first beat frequency optical signal; the first beat frequency optical signal is incident to the first photodetector 11a, and is converted into a first electrical signal by the first photodetector 11a and then transmitted to the PC 12;

[0064] The second optical signal divided by the first 1x3 coupler 5a is incident to the second measuring mirror 9b in sequence through the second circulator 6b and the second optical fiber 7b, and forms a second reflected optical signal after reflection by the second measuring mirror 9b; the second reflected optical signal is incident to the second 2x1 coupler 10b in sequence through the second optical fiber 7b and the second circulator 6b; the second optical signal divided by the second 1x3 coupler 5b is incident to the second 2x1 coupler 10b, and interferes with the second reflected optical signal in the second 2x1 coupler 10b to form a second beat frequency optical signal; the second beat frequency optical signal is incident to the second photodetector 11b, and is converted into a second electrical signal by the second photodetector 11b and then transmitted to the PC 12;

[0065] The third optical signal divided by the first 1x3 coupler 5a is incident to the reference mirror 9c in sequence through the third circulator 6c and the third optical fiber 7c, and forms a third reflected optical signal after reflection by the reference mirror 9c; the third reflected optical signal is incident to the third 2x1 coupler 10c in sequence through the third optical fiber 7c and the third circulator 6c; the third optical signal divided by the second 1x3 coupler 5b is incident to the third 2x1 coupler 10c, and interferes with the third reflected optical signal in the third 2x1 coupler 10c to form a third beat frequency optical signal; the third beat frequency optical signal is incident to the third photodetector 11c, and is converted into a third electrical signal by the third photodetector 11c and then transmitted to the PC 12;

[0066] In the working mode, the tail end face of the first optical fiber 7a and the front face of the first measuring mirror 9a jointly constitute a first F-P resonant cavity, the tail end face of the second optical fiber 7b and the front face of the second measuring mirror 9b jointly constitute a second F-P resonant cavity, and the tail end face of the third optical fiber 7c and the front face of the reference mirror 9c jointly constitute a third F-P resonant cavity;

[0067] When there is no acceleration input, the cavity length of the first F-P resonant cavity, the cavity length of the second F-P resonant cavity, and the cavity length of the third F-P resonant cavity remain consistent, and the phase of the first electric signal, the phase of the second electric signal, and the phase of the third electric signal remain consistent;

[0068] When there is an acceleration input, the acceleration acts on the two short elastic beams 8a, causing the first mass block 8c and the first measuring mirror 9a to undergo simple harmonic vibration, and acts on the two long elastic beams 8b, causing the second mass block 8d and the second measuring mirror 9b to undergo simple harmonic vibration, thereby causing the cavity length of the first F-P resonant cavity to change and the cavity length of the second F-P resonant cavity to change, and thereby causing the phase of the first electric signal to change and the phase of the second electric signal to change; at the same time, the cavity length of the third F-P resonant cavity remains unchanged, thereby causing the phase of the third electric signal to remain unchanged; then, the PC 12 substitutes the phase of the first electric signal and the phase of the third electric signal into a first acceleration measurement equation of the sensor, thereby obtaining a first measurement result of the acceleration, and substitutes the phase of the second electric signal and the phase of the third electric signal into a second acceleration measurement equation of the sensor, thereby obtaining a second measurement result of the acceleration;

[0069] When the input acceleration is small, the amplitude of the second mass block 8d and the second measuring mirror 9b is greater than the amplitude of the first mass block 8c and the first measuring mirror 9a due to the smaller stiffness of the two long elastic beams 8b than the stiffness of the two short elastic beams 8a, causing the cavity length change of the second F-P resonant cavity to be greater than the cavity length change of the first F-P resonant cavity, thereby causing the phase change of the second electric signal to be greater than the phase change of the first electric signal, and thereby causing the accuracy of the second measurement result of the acceleration to be higher than the accuracy of the first measurement result of the acceleration; at this time, the second measurement result of the acceleration is taken as the high-precision measurement result of the acceleration;

[0070] When the input acceleration is large, since the stiffness of the two long elastic beams 8b is less than that of the two short elastic beams 8a, when the amplitude of the second mass block 8d and the second measuring mirror 9b exceeds the limit, the amplitude of the first mass block 8c and the first measuring mirror 9a will still remain normal. This means that when the cavity length change of the second FP resonant cavity exceeds the limit, the cavity length change of the first FP resonant cavity will still remain normal. Consequently, when the phase change of the second electrical signal exceeds the limit, the phase change of the first electrical signal will still remain normal. Therefore, when the second measurement result of acceleration exceeds the range, the first measurement result of acceleration will still be within the range. At this time, the first measurement result of acceleration is taken as the large range measurement result of acceleration.

[0071] The first acceleration measurement equation of the sensor is expressed as follows:

[0072] ;

[0073] ;

[0074] In the formula: This represents the displacement of the first mass block 8c; Indicates the phase of the first electrical signal; Indicates the phase of the third electrical signal; This indicates the wavelength of the laser emitted by the narrow linewidth laser 1; The first type of measurement result representing acceleration; This represents the elastic modulus of the short elastic beam 8a; This represents the mass of the first mass block 8c.

[0075] The second acceleration measurement equation of the sensor is expressed as follows:

[0076] ;

[0077] ;

[0078] In the formula: This represents the displacement of the second mass block 8d; Indicates the phase of the second electrical signal; Indicates the phase of the third electrical signal; This indicates the wavelength of the laser emitted by the narrow linewidth laser 1; The second measurement result representing acceleration; This represents the elastic modulus of the long elastic beam 8b; This represents the mass of the second mass block 8d.

[0079] The frequency difference between the two optical signals after frequency shifting is 1MHz.

[0080] In practice, the two short elastic beams 8a are each in the form of a sheet having a length of 50 mm and a thickness of 400 μm. The two long elastic beams 8b are each in the form of a sheet having a length of 100 mm and a thickness of 50 μm.

[0081] Although the above describes specific embodiments of the present application, those skilled in the art will understand that these are merely illustrative, and the scope of protection of the present application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and the essence of the present application, and these changes and modifications all fall within the scope of protection of the present application.

Claims

1. A large-range optical accelerometer based on a heterodyne interferometry structure, characterized in that: Includes a narrow linewidth laser (1), an isolator (2), a 1×2 coupler (3), a first acousto-optic modulator (4a), a second acousto-optic modulator (4b), a first 1×3 coupler (5a), a second 1×3 coupler (5b), a first circulator (6a), a second circulator (6b), a third circulator (6c), a first optical fiber (7a), a second optical fiber (7b), a third optical fiber (7c), a sensing unit, a first 2×1 coupler (10a), a second 2×1 coupler (10b), a third 2×1 coupler (10c), a first photodetector (11a), a second photodetector (11b), a third photodetector (11c), and a PC (12); The sensitive unit includes a base, a first measuring mirror (9a), a second measuring mirror (9b), and a reference mirror (9c); the back of the first measuring mirror (9a), the back of the second measuring mirror (9b), and the back of the reference mirror (9c) are all fixed to the base; The output end of the narrow linewidth laser (1) is connected to the input end of the 1×2 coupler (3) through the isolator (2); the two output ends of the 1×2 coupler (3) are respectively connected to the input ends of the first acousto-optic modulator (4a) and the second acousto-optic modulator (4b); the output end of the first acousto-optic modulator (4a) is connected to the input end of the first 1×3 coupler (5a); the output end of the second acousto-optic modulator (4b) is connected to the input end of the second 1×3 coupler (5b); The three output ends of the first 1×3 coupler (5a) are respectively connected to the first port of the first circulator (6a), the first port of the second circulator (6b), and the first port of the third circulator (6c). The second port of the first circulator (6a) is connected to the head end of the first optical fiber (7a); the tail end face of the first optical fiber (7a) faces the front of the first measuring mirror (9a); the third port of the first circulator (6a) is connected to the first incident end of the first 2×1 coupler (10a); the second port of the second circulator (6b) is connected to the head end of the second optical fiber (7b); the tail end face of the second optical fiber (7b) faces the front of the second measuring mirror (9b); the third port of the second circulator (6b) is connected to the first incident end of the second 2×1 coupler (10b); the second port of the third circulator (6c) is connected to the head end of the third optical fiber (7c); the tail end face of the third optical fiber (7c) faces the front of the reference mirror (9c); the third port of the third circulator (6c) is connected to the first incident end of the third 2×1 coupler (10c). The three output ends of the second 1×3 coupler (5b) are respectively connected to the second input end of the first 2×1 coupler (10a), the second input end of the second 2×1 coupler (10b), and the second input end of the third 2×1 coupler (10c). The output end of the first 2×1 coupler (10a) is connected to the input end of the first photodetector (11a); the output end of the second 2×1 coupler (10b) is connected to the input end of the second photodetector (11b); the output end of the third 2×1 coupler (10c) is connected to the input end of the third photodetector (11c); the signal output ends of the first photodetector (11a), the second photodetector (11b), and the third photodetector (11c) are all connected to the signal input end of the PC (12).

2. The large-range optical accelerometer based on a heterodyne interferometry structure according to claim 1, characterized in that: The base includes two short elastic beams (8a) that are parallel to each other and facing each other, and two long elastic beams (8b) that are parallel to each other and facing each other. A first mass block (8c) is fixed between the inner sides of the first ends of two short elastic beams (8a); a first connecting block (8e) is fixed between the inner sides of the tail ends of two short elastic beams (8a); the tail ends of two long elastic beams (8b) are flush with the tail ends of two short elastic beams (8a); the first ends of two long elastic beams (8b) extend beyond the first ends of two short elastic beams (8a); a second mass block (8d) is fixed between the inner sides of the first ends of two long elastic beams (8b); a second connecting block (8f) is fixed between the inner sides of the tail ends of two long elastic beams (8b); a third connecting block (8g) is fixed between the outer side of the tail end of the second short elastic beam (8a) and the outer side of the tail end of the first long elastic beam (8b). The back of the first measuring mirror (9a) is fixed to the outer side of the first end of the first short elastic beam (8a); the back of the second measuring mirror (9b) is fixed to the outer side of the first end of the first long elastic beam (8b); and the back of the reference mirror (9c) is fixed to the outer side of the tail end of the first short elastic beam (8a).

3. The large-range optical accelerometer based on a heterodyne interferometry structure according to claim 2, characterized in that: The two short elastic beams (8a), the two long elastic beams (8b), the first mass block (8c), the second mass block (8d), the first connecting block (8e), the second connecting block (8f), and the third connecting block (8g) are all made of fused silica.

4. The large-range optical accelerometer based on a heterodyne interferometry structure according to claim 1, characterized in that: The splitting ratio of the 1×2 coupler (3) is 50:50; the splitting ratio of the first 1×3 coupler (5a) and the splitting ratio of the second 1×3 coupler (5b) are both 33.3:33.3:33.

3.

5. The large-range optical accelerometer based on a heterodyne interferometry structure according to claim 1, characterized in that: The first measuring mirror (9a), the second measuring mirror (9b), and the reference mirror (9c) are all planar high-reflectivity mirrors.

6. A large-range optical acceleration measurement method based on a heterodyne interferometry structure, wherein the method is implemented based on the large-range optical accelerometer based on a heterodyne interferometry structure as described in claim 2, characterized in that: This method is implemented using the following steps: First, control the sensor to enter the working mode; the working mode is as follows: The laser emitted by the narrow linewidth laser (1) is isolated by the isolator (2) and then incident on the 1×2 coupler (3), and is split into two optical signals of equal power by the 1×2 coupler (3); the two optical signals are frequency shifted by the first acousto-optic modulator (4a) and the second acousto-optic modulator (4b) respectively to form two optical signals with different frequencies: the first optical signal is incident on the first 1×3 coupler (5a), and is split into three optical signals of equal power by the first 1×3 coupler (5a); the second optical signal is incident on the second 1×3 coupler (5b), and is split into three optical signals of equal power by the second 1×3 coupler (5b); The first optical signal split from the first 1×3 coupler (5a) is sequentially incident on the first measuring mirror (9a) via the first circulator (6a) and the first optical fiber (7a), and is reflected by the first measuring mirror (9a) to form the first reflected optical signal; the first reflected optical signal is sequentially incident on the first 2×1 coupler (10a) via the first optical fiber (7a) and the first circulator (6a); the first optical signal split from the second 1×3 coupler (5b) is incident on the first 2×1 coupler (10a), and interferes with the first reflected optical signal in the first 2×1 coupler (10a) to form the first beat frequency optical signal; the first beat frequency optical signal is incident on the first photodetector (11a), and is converted into the first electrical signal by the first photodetector (11a) and transmitted to the PC (12). The second optical signal split from the first 1×3 coupler (5a) is sequentially incident on the second measuring mirror (9b) via the second circulator (6b) and the second optical fiber (7b), and is reflected by the second measuring mirror (9b) to form a second reflected optical signal; the second reflected optical signal is sequentially incident on the second 2×1 coupler (10b) via the second optical fiber (7b) and the second circulator (6b); the second optical signal split from the second 1×3 coupler (5b) is incident on the second 2×1 coupler (10b), and interferes with the second reflected optical signal in the second 2×1 coupler (10b) to form a second beat frequency optical signal; the second beat frequency optical signal is incident on the second photodetector (11b), and is converted into a second electrical signal by the second photodetector (11b) and transmitted to the PC (12); The third optical signal split from the first 1×3 coupler (5a) is sequentially incident on the reference mirror (9c) via the third circulator (6c) and the third optical fiber (7c), and is reflected by the reference mirror (9c) to form the third reflected optical signal; the third reflected optical signal is sequentially incident on the third 2×1 coupler (10c) via the third optical fiber (7c) and the third circulator (6c); the third optical signal split from the second 1×3 coupler (5b) is incident on the third 2×1 coupler (10c), and interferes with the third reflected optical signal in the third 2×1 coupler (10c) to form the third beat frequency optical signal; the third beat frequency optical signal is incident on the third photodetector (11c), and is converted into the third electrical signal by the third photodetector (11c) and transmitted to the PC (12); In the working mode, the tail end face of the first optical fiber (7a) and the front face of the first measuring mirror (9a) together form the first FP resonant cavity, the tail end face of the second optical fiber (7b) and the front face of the second measuring mirror (9b) together form the second FP resonant cavity, and the tail end face of the third optical fiber (7c) and the front face of the reference mirror (9c) together form the third FP resonant cavity. When there is no acceleration input, the cavity lengths of the first FP resonant cavity, the second FP resonant cavity, and the third FP resonant cavity remain consistent, and the phases of the first electrical signal, the second electrical signal, and the third electrical signal remain consistent. When there is an acceleration input, the acceleration acts on two short elastic beams (8a) on the one hand, causing the first mass block (8c) and the first measuring mirror (9a) to undergo simple harmonic motion, and on two long elastic beams (8b) on the other hand, causing the second mass block (8d) and the second measuring mirror (9b) to undergo simple harmonic motion. This causes the cavity length of the first FP resonant cavity to change on the one hand, and the cavity length of the second FP resonant cavity to change on the other hand, thus causing the phase of the first electrical signal to change on the one hand, and the phase of the second electrical signal to change on the other hand. At the same time, the cavity length of the third FP resonant cavity remains unchanged, thus causing the phase of the third electrical signal to remain unchanged. Then, the PC (12) substitutes the phase of the first electrical signal and the phase of the third electrical signal into the first acceleration measurement equation of the sensor to obtain the first measurement result of acceleration. On the other hand, it substitutes the phase of the second electrical signal and the phase of the third electrical signal into the second acceleration measurement equation of the sensor to obtain the second measurement result of acceleration. When the input acceleration is small, since the stiffness of the two long elastic beams (8b) is less than that of the two short elastic beams (8a), the amplitude of the second mass block (8d) and the second measuring mirror (9b) will be greater than that of the first mass block (8c) and the first measuring mirror (9a). This makes the change in the cavity length of the second FP resonant cavity greater than that of the first FP resonant cavity, which in turn makes the phase change of the second electrical signal greater than that of the first electrical signal. As a result, the accuracy of the second measurement result of acceleration is higher than that of the first measurement result of acceleration. In this case, the second measurement result of acceleration is taken as the high-precision measurement result of acceleration. When the input acceleration is large, since the stiffness of the two long elastic beams (8b) is less than that of the two short elastic beams (8a), when the amplitude of the second mass block (8d) and the second measuring mirror (9b) exceeds the limit, the amplitude of the first mass block (8c) and the first measuring mirror (9a) will still remain normal. This means that when the cavity length change of the second FP resonant cavity exceeds the limit, the cavity length change of the first FP resonant cavity will still remain normal. Consequently, when the phase change of the second electrical signal exceeds the limit, the phase change of the first electrical signal will still remain normal. Thus, when the second measurement result of acceleration exceeds the range, the first measurement result of acceleration will still be within the range. At this time, the first measurement result of acceleration will be taken as the large range measurement result of acceleration.

7. The large-range optical acceleration measurement method based on heterodyne interferometry structure according to claim 6, characterized in that: The first acceleration measurement equation of the sensor is expressed as follows: ； ； In the formula: This represents the displacement of the first mass block (8c); Indicates the phase of the first electrical signal; Indicates the phase of the third electrical signal; This indicates the wavelength of the laser emitted by the narrow linewidth laser (1); The first type of measurement result representing acceleration; This represents the elastic modulus of the short elastic beam (8a); This represents the mass of the first mass block (8c).

8. The large-range optical acceleration measurement method based on heterodyne interferometry structure according to claim 6, characterized in that: The second acceleration measurement equation of the sensor is expressed as follows: ； ； In the formula: This represents the displacement of the second mass block (8d); Indicates the phase of the second electrical signal; Indicates the phase of the third electrical signal; This indicates the wavelength of the laser emitted by the narrow linewidth laser (1); The second measurement result representing acceleration; This represents the elastic modulus of the long elastic beam (8b); This represents the mass of the second mass block (8d).

9. The large-range optical acceleration measurement method based on heterodyne interferometry structure according to claim 6, characterized in that: The frequency difference between the two optical signals after frequency shifting is 1MHz.

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