Large-range optical acceleration sensor based on heterodyne interference structure and measuring method

Abstract

The application relates to the technical field of optical acceleration sensors, in particular to a large-range optical acceleration sensor based on a heterodyne interference structure and a measuring method, which comprises a narrow-line-width 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 loop, a second loop, a third loop, a first optical fiber, a second optical fiber, a third optical fiber, a sensitive unit, a first 2*1 coupler, a second 2*1 coupler, a third 2*1 coupler, a first photoelectric detector, a second photoelectric detector, a third photoelectric detector and a PC; the sensitive unit comprises a base, a first measuring mirror, a second measuring mirror and a reference mirror; the back surface of the first measuring mirror, the back surface of the second measuring mirror and the back surface of the reference mirror are fixed to the base. The application solves the problem that the existing optical acceleration sensor cannot realize large-range measurement for larger acceleration and is suitable for the fields of industrial automation and intelligent monitoring.

Description

Technical Field

[0001] This invention relates to the field of optical acceleration sensor technology, specifically a large-range optical acceleration sensor and measurement method based on a heterodyne interference structure. Background Technology

[0002] With the rapid development of industrial automation, intelligent monitoring, and other fields, the demand for high-performance sensors continues to grow. Optical accelerometers, with their unique advantages, have shown promising application prospects in many fields. However, in practical applications, existing optical accelerometers, due to their structural limitations, can only achieve high-precision measurements for relatively small accelerations, and cannot achieve large-range measurements for larger accelerations, thus limiting their applicability. Therefore, it is necessary to invent a large-range optical accelerometer and measurement method based on a heterodyne interferometry structure to solve the problem that existing optical accelerometers cannot achieve large-range measurements for larger accelerations. Summary of the Invention

[0003] To address the problem that existing optical accelerometers cannot achieve large-range measurements for large accelerations, this invention provides a large-range optical accelerometer and measurement method based on a heterodyne interferometry structure.

[0004] This invention is achieved using the following technical solution:

[0005] A large-range optical accelerometer based on a heterodyne interferometer structure includes 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 element, a first 2×1 coupler, a second 2×1 coupler, a third 2×1 coupler, a first photodetector, a second photodetector, a third photodetector, and a PC.

[0006] The sensitive unit includes 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 to the base;

[0007] The output end of the narrow linewidth laser is connected to the input end of a 1×2 coupler via an isolator; the two output ends of the 1×2 coupler are respectively connected to the input ends of the first acousto-optic modulator and the second acousto-optic modulator; the output end of the first acousto-optic modulator is connected to the input end of the first 1×3 coupler; and the output end of the second acousto-optic modulator is connected to the input end of the second 1×3 coupler.

[0008] The three output terminals of the first 1×3 coupler are respectively connected to the first port of the first circulator, the first port of the second circulator, and the first port of the third circulator;

[0009] The second port of the first circulator is connected to the head end of the first optical fiber; the tail end face of the first optical fiber faces the front of the first measuring mirror; the third port of the first circulator is connected to the first incident end of the first 2×1 coupler; the second port of the second circulator is connected to the head end of the second optical fiber; the tail end face of the second optical fiber faces the front of the second measuring mirror; the third port of the second circulator is connected to the first incident end of the second 2×1 coupler; the second port of the third circulator is connected to the head end of the third optical fiber; the tail end face of the third optical fiber faces the front of the reference mirror; the third port of the third circulator is connected to the first incident end of the third 2×1 coupler.

[0010] The three output terminals of the second 1×3 coupler are respectively connected to the second input terminal of the first 2×1 coupler, the second input terminal of the second 2×1 coupler, and the second input terminal of the third 2×1 coupler;

[0011] The output end of the first 2×1 coupler is connected to the input end of the first photodetector; the output end of the second 2×1 coupler is connected to the input end of the second photodetector; the output end of the third 2×1 coupler is connected to the input end of the third photodetector; the signal output ends of the first photodetector, the second photodetector, and the third photodetector are all connected to the signal input end of the PC.

[0012] Furthermore, the base includes two short elastic beams that are parallel to each other and facing each other, and two long elastic beams that are parallel to each other and facing each other.

[0013] A first mass block is fixed between the inner sides of the first ends of two short elastic beams; a first connecting block is fixed between the inner sides of the tail ends of two short elastic beams; the tail ends of two long elastic beams are flush with the tail ends of two short elastic beams; the first ends of two long elastic beams extend beyond the first ends of two short elastic beams; a second mass block is fixed between the inner sides of the first ends of two long elastic beams; a second connecting block is fixed between the inner sides of the tail ends of two long elastic beams; a third connecting block is fixed between the outer side of the tail end of the second short elastic beam and the outer side of the tail end of the first long elastic beam.

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

[0015] Furthermore, 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 all made of fused silica.

[0016] Furthermore, the splitting ratio of the 1×2 coupler is 50:50; the splitting ratios of the first 1×3 coupler and the second 1×3 coupler are both 33.3:33.3:33.3.

[0017] Furthermore, the first measuring mirror, the second measuring mirror, and the reference mirror are all planar high-reflectivity mirrors.

[0018] A large-range optical acceleration measurement method based on a heterodyne interferometer structure, which is implemented using the large-range optical acceleration sensor based on a heterodyne interferometer structure described in this invention, is carried out through the following steps:

[0019] First, control the sensor to enter the working mode; the working mode is as follows:

[0020] The laser emitted by the narrow linewidth laser is isolated by an isolator and then incident on a 1×2 coupler, where it is split into two optical signals of equal power. The two optical signals are then frequency-shifted by a first acousto-optic modulator and a second acousto-optic modulator, respectively, to form two optical signals with different frequencies. The first optical signal is incident on a first 1×3 coupler and split into three optical signals of equal power. The second optical signal is incident on a second 1×3 coupler and split into three optical signals of equal power.

[0021] The first optical signal split from the first 1×3 coupler is sequentially incident on the first measuring mirror via the first circulator and the first optical fiber, and is reflected by the first measuring mirror to form the first reflected optical signal; the first reflected optical signal is sequentially incident on the first optical fiber and the first circulator to the first 2×1 coupler; the first optical signal split from the second 1×3 coupler is incident on the first 2×1 coupler, and interferes with the first reflected optical signal in the first 2×1 coupler to form the first beat frequency optical signal; the first beat frequency optical signal is incident on the first photodetector, and is converted into the first electrical signal by the first photodetector and transmitted to the PC;

[0022] The second optical signal split from the first 1×3 coupler is sequentially incident on the second measuring mirror via the second circulator and the second optical fiber, and is reflected by the second measuring mirror to form the second reflected optical signal; the second reflected optical signal is sequentially incident on the second optical fiber and the second circulator to the second 2×1 coupler; the second optical signal split from the second 1×3 coupler is incident on the second 2×1 coupler, and interferes with the second reflected optical signal in the second 2×1 coupler to form the second beat frequency optical signal; the second beat frequency optical signal is incident on the second photodetector, and is converted into the second electrical signal by the second photodetector before being transmitted to the PC;

[0023] The third optical signal split from the first 1×3 coupler is sequentially incident on the reference mirror via the third circulator and the third optical fiber, and is reflected by the reference mirror to form the third reflected optical signal; the third reflected optical signal is sequentially incident on the third optical fiber and the third circulator to the third 2×1 coupler; the third optical signal split from the second 1×3 coupler is incident on the third 2×1 coupler, and interferes with the third reflected optical signal in the third 2×1 coupler to form the third beat frequency optical signal; the third beat frequency optical signal is incident on the third photodetector, and is converted into a third electrical signal by the third photodetector before being 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 measuring mirror together form the first FP resonant cavity, the tail end face of the second optical fiber and the front face of the second measuring mirror together form the second FP resonant cavity, and the tail end face of the third optical fiber and the front face of the reference mirror together form the third FP resonant cavity.

[0025] 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.

[0026] When acceleration is input, it acts on two short elastic beams, causing the first mass and the first measuring mirror to undergo simple harmonic motion, and on two long elastic beams, causing the second mass and the second measuring mirror to undergo simple harmonic motion. This causes changes in the cavity length of both the first and second FP resonant cavities, resulting in changes in the phase of both the first and second electrical signals. Simultaneously, the cavity length of the third FP resonant cavity remains unchanged, thus keeping the phase of the third electrical signal constant. Then, the PC substitutes the phases of the first and third electrical signals into the sensor's first acceleration measurement equation to obtain the first measurement result of acceleration. Simultaneously, the PC substitutes the phases of the second and third electrical signals into the sensor's second acceleration measurement equation to obtain the second measurement result of acceleration.

[0027] When the input acceleration is small, because the stiffness of the two long elastic beams is less than that of the two short elastic beams, the amplitude of the second mass and the second measuring mirror will be greater than that of the first mass and the first measuring mirror. This results in the cavity length change of the second FP resonant cavity being greater than that of the first FP resonant cavity. Consequently, the phase change of the second electrical signal is greater than that of the first electrical signal, making the accuracy of the second acceleration measurement result higher than that of the first acceleration measurement result. In this case, the second acceleration measurement result is taken as the high-precision acceleration measurement result.

[0028] When the input acceleration is large, since the stiffness of the two long elastic beams is less than that of the two short elastic beams, when the amplitude of the second mass block and the second measuring mirror exceeds the limit, the amplitude of the first mass block and the first measuring mirror 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.

[0029] Furthermore, the first acceleration measurement equation of the sensor is expressed as follows:

[0030] ;

[0031] ;

[0032] In the formula: This represents the displacement of the first mass block; Indicates the phase of the first electrical signal; Indicates the phase of the third electrical signal; Indicates the wavelength of laser emitted by a narrow-linewidth laser; The first type of measurement result representing acceleration; This represents the elastic modulus of a short elastic beam; This represents the mass of the first mass block.

[0033] Furthermore, the second acceleration measurement equation of the sensor is expressed as follows:

[0034] ;

[0035] ;

[0036] In the formula: This indicates the displacement of the second mass block; Indicates the phase of the second electrical signal; Indicates the phase of the third electrical signal; Indicates the wavelength of laser emitted by a narrow-linewidth laser; The second measurement result representing acceleration; This represents the elastic modulus of a long elastic beam; This indicates the mass of the second mass block.

[0037] Furthermore, the frequency difference between the two optical signals after frequency shifting is 1MHz.

[0038] Compared with existing optical accelerometers, this invention adopts a novel structure, which enables high-precision measurement for smaller accelerations and large-range measurement for larger accelerations, thus combining high precision and large range, thereby removing the limitations on its application scope.

[0039] This invention effectively solves the problem that existing optical accelerometers cannot achieve large-range measurement for large accelerations, and is applicable to fields such as industrial automation and intelligent monitoring. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the optical path of the present invention.

[0041] Figure 2 This is a schematic diagram of the planar structure of the sensitive unit in this invention.

[0042] Figure 3 This is a three-dimensional structural diagram of the sensitive unit in this invention.

[0043] Figure 4 yes Figure 3 Partial structural diagram Figure 1 .

[0044] Figure 5 yes Figure 3 Partial structural diagram Figure 2 .

[0045] Figure 6 yes Figure 3 Partial structural diagram Figure 3 .

[0046] In the diagram: 1-Narrow linewidth laser, 2-Isolator, 3-1×2 coupler, 4a-First acousto-optic modulator, 4b-Second acousto-optic modulator, 5a-First 1×3 coupler, 5b-Second 1×3 coupler, 6a-First circulator, 6b-Second circulator, 6c-Third 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 measuring mirror, 9b-Second measuring mirror, 9c-Reference mirror, 10a-First 2×1 coupler, 10b-Second 2×1 coupler, 10c-Third 2×1 coupler, 11a-First photodetector, 11b-Second photodetector, 11c-Third photodetector, 12-PC. Detailed Implementation

[0047] A large-range optical accelerometer based on a heterodyne interferometer structure 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.

[0048] The sensitive unit includes a base, a first measuring mirror 9a, a second measuring mirror 9b, and a reference mirror 9c; the back surfaces of the first measuring mirror 9a, the second measuring mirror 9b, and the reference mirror 9c are all fixed to the base.

[0049] The emitting end of the narrow linewidth laser 1 is connected to the incident end of the 1×2 coupler 3 through the isolator 2; the two emitting ends of the 1×2 coupler 3 are respectively connected to the incident ends of the first acousto-optic modulator 4a and the second acousto-optic modulator 4b; the emitting end of the first acousto-optic modulator 4a is connected to the incident end of the first 1×3 coupler 5a; the emitting end of the second acousto-optic modulator 4b is connected to the incident end of the second 1×3 coupler 5b.

[0050] The three output terminals 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] A first mass block 8c is fixed between the inner sides of the first ends of the two short elastic beams 8a; a first connecting block 8e is fixed between the inner sides 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 first ends of the two long elastic beams 8b extend beyond the first ends of the two short elastic beams 8a; a second mass block 8d is fixed between the inner sides of the first ends of the two long elastic beams 8b; a second connecting block 8f is fixed between the inner sides of the tail ends of the 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.

[0056] 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.

[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 silica.

[0058] 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.

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

[0060] A large-range optical acceleration measurement method based on a heterodyne interferometer structure, which is implemented using the large-range optical acceleration sensor based on a heterodyne interferometer structure described in this invention, is carried out through the following steps:

[0061] First, control the sensor to enter the working mode; the working mode is as follows:

[0062] The laser emitted by the narrow linewidth laser 1 is isolated by the isolator 2 and then incident on the 1×2 coupler 3, where it is split into two optical signals of equal power. The two optical signals are then 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 split into three optical signals of equal power. The second optical signal is incident on the second 1×3 coupler 5b and split into three optical signals of equal power.

[0063] 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 optical fiber 7a and the first circulator 6a via the first 2×1 coupler 10a; 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.

[0064] 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 optical fiber 7b and the second circulator 6b via the second 2×1 coupler 10b; 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 before being transmitted to the PC 12;

[0065] 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 optical fiber 7c and the third circulator 6c via the third 2×1 coupler 10c; 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 before being 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 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.

[0067] 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.

[0068] When acceleration is input, the acceleration acts on two short elastic beams 8a, causing the first mass block 8c and the first measuring mirror 9a to undergo simple harmonic motion, and on two long elastic beams 8b, causing the second mass block 8d and the second measuring mirror 9b to undergo simple harmonic motion. This causes changes in the cavity length of the first FP resonant cavity and the cavity length of the second FP resonant cavity, which in turn causes changes in the phase of the first and second electrical signals. At the same time, the cavity length of the third FP resonant cavity remains unchanged, thus keeping the phase of the third electrical signal unchanged. Then, the PC 12 substitutes the phases of the first and third electrical signals into the sensor's first acceleration measurement equation to obtain the first measurement result of acceleration, and substitutes the phases of the second and third electrical signals into the sensor's second acceleration measurement equation to obtain the second measurement result of acceleration.

[0069] When the input acceleration is small, because 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 the amplitude of the first mass block 8c and the first measuring mirror 9a. This results in the cavity length change of the second FP resonant cavity being greater than that of the first FP resonant cavity. Consequently, the phase change of the second electrical signal is greater than that of the first electrical signal, making the accuracy of the second acceleration measurement result higher than that of the first acceleration measurement result. In this case, the second acceleration measurement result is taken as the high-precision acceleration measurement result.

[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. 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 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, both short elastic beams 8a are sheet-like structures, with a length of 50 mm and a thickness of 400 micrometers. Both long elastic beams 8b are sheet-like structures, with a length of 100 mm and a thickness of 50 micrometers.

[0081] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention 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 essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

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 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); the back of the reference mirror (9c) is fixed to the outer side of the tail end of the first short elastic beam (8a). 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 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.

3. 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.

4. 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.

5. 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 1, 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.

6. The large-range optical acceleration measurement method based on heterodyne interferometry structure according to claim 5, 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).

7. The large-range optical acceleration measurement method based on heterodyne interferometry structure according to claim 5, 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).

8. The large-range optical acceleration measurement method based on heterodyne interferometry structure according to claim 5, characterized in that: The frequency difference between the two optical signals after frequency shifting is 1MHz.

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