CN220933001U - Optical fiber accelerometer probe and acceleration sensing system - Google Patents

Abstract

The utility model relates to an optical fiber interference sensing technology and discloses an optical fiber accelerometer probe and an acceleration sensing system; the optical fiber accelerometer probe is applied to an acceleration sensing system and comprises a mass block; the first elastic column body and the second elastic column body are arranged at two ends of the mass block; the first optical fiber and the second optical fiber are respectively wound on the first elastic column body and the second elastic column body; a first reflective element disposed at a second end of the first optical fiber; a second reflective element disposed at a second end of the second optical fiber; the first end part of the first optical fiber and the first end part of the second optical fiber are connected with a light source component and a light detector in the acceleration sensing system through a light path component. In the utility model, even if the probe of the accelerometer generates tiny vibration at the surveying position, obvious optical path difference can be generated between two paths of light rays in the first optical fiber and the second optical fiber, and the sensitivity of the accelerometer is improved.

Description

Optical fiber accelerometer probe and acceleration sensing system

Technical Field

The utility model relates to the technical field of optical fiber interference type sensing, in particular to an optical fiber accelerometer probe and an acceleration sensing system.

Background

Seismic exploration is an exploration method commonly adopted in the field of oil and gas resource exploitation, and oil and gas development is turned to unconventional oil and gas reservoirs due to the lack of conventional oil and gas resources, wherein the unconventional oil and gas reservoirs are generally in a complex deep geological environment. The low-frequency signal has stronger penetrability, can be transmitted to the depth of the earth surface, carries abundant inversion information, adopts the low-frequency seismic wave signal excited manually at 0-160Hz as a seismic source, and is more suitable for the exploration of deep unconventional oil and gas reservoirs. The optical fiber accelerometer uses the optical fiber as a transmission medium and uses light as a carrier, has the advantages of high sensitivity, high temperature and high pressure resistance, strong electromagnetic interference resistance and the like, and is convenient for underground low-frequency seismic exploration. However, the existing optical fiber accelerometer probe has the problem of low sensitivity, and is difficult to meet the actual measurement requirement.

Disclosure of utility model

The utility model aims to provide an optical fiber accelerometer probe and an acceleration sensing system, which can improve the surveying precision of the optical fiber accelerometer probe to a certain extent and better meet the dynamic range requirement of low-frequency detection.

In order to solve the technical problems, the utility model provides an optical fiber accelerometer probe which is applied to an acceleration sensing system and comprises a mass block; the first elastic column body and the second elastic column body are arranged at two ends of the mass block; a first optical fiber and a second optical fiber wound around the first elastic column and the second elastic column, respectively; a first reflective element disposed at a second end of the first optical fiber; a second reflective element disposed at a second end of the second optical fiber;

the first end of the first optical fiber and the first end of the second optical fiber are connected with a light source assembly and a light detector in the acceleration sensing system through a light path assembly, so that light rays output by the light source assembly are divided into two paths of coherent light rays through the light path assembly and are respectively input into the first optical fiber and the second optical fiber, and the light rays reflected by the first reflecting element and the second reflecting element are conducted to the light detector after being interfered with each other through the light path assembly.

Optionally, the first reflective element and the second reflective element are both faraday rotator mirrors.

Optionally, the first elastic column and the second elastic column are both made of silica gel; the mass block is a manganese brass structure block; the first optical fiber and the second optical fiber are g657.a2 bending resistant optical fibers.

Optionally, the mass block is a cylinder with the cross section radius of 14 mm-16 mm; the first elastic column body and the second elastic column body are both cylinders with the cross-sectional radius smaller than that of the mass block; the total height of the mass block and the first elastic column body and the second elastic column body is 28 mm-32 mm.

Optionally, the mass block, the first elastic column and the second elastic column are all encapsulated in a cylindrical shell, and aluminum covers are arranged at two ends of the cylindrical shell and used for forming a closed cavity together with the cylindrical shell;

And the two cylindrical shells are respectively in fit connection with the end parts of the first elastic column body and the second elastic column body, which deviate from the mass block.

An acceleration sensing system comprising a fibre optic accelerometer probe as claimed in any one of the preceding claims; the light source component, the light detector, the light path component and the signal processing unit; the output end of the light source component and the input end of the optical detector are respectively connected with the optical fiber accelerometer probe through the optical path component; the output end of the optical detector is connected with the input end of the signal processing unit;

The light output by the light source assembly is divided into two paths of coherent light through the light path assembly and respectively enters the first optical fiber and the second optical fiber of the optical fiber accelerometer probe, the two paths of coherent light respectively enter the light path assembly after being reflected by the first reflecting element and the second reflecting element of the optical fiber accelerometer probe, and enter the light detector after being interfered in the light path assembly, the light detector detects and photoelectrically converts interference light waves, and the converted electric signals are transmitted to the signal processing unit, so that the signal processing unit processes the detected signals.

Optionally, the optical path component comprises an optical fiber coupler and a lithium niobate y waveguide modulator; the device also comprises a signal processing unit;

The output end of the light source component is connected with the first end of the optical fiber coupler; the second end of the optical fiber coupler is connected with the optical signal input end of the lithium niobate y waveguide modulator; the first output end and the second output end of the lithium niobate y waveguide modulator are respectively connected with the first end part of the first optical fiber and the first end part of the second optical fiber in the optical fiber accelerometer probe; the third end of the optical fiber coupler is connected with the input end of the optical detector; the output end of the optical detector is connected with the input end of the signal processing unit; the output end of the signal processing unit is connected with the modulation signal input end of the lithium niobate y waveguide modulator;

The light output by the light source assembly is transmitted to the lithium niobate y waveguide modulator through the optical fiber coupler, the lithium niobate y waveguide modulator splits the light into two paths of coherent light rays which are respectively incident to the first optical fiber and the second optical fiber, the two paths of coherent light rays are respectively transmitted to a first reflecting element and a second reflecting element in the optical fiber accelerometer probe, reflected and are incident into the lithium niobate y waveguide modulator through the first optical fiber and the second optical fiber, and mutual interference occurs in the lithium niobate y waveguide modulator; the light waves which interfere with each other are transmitted to the light detector through the optical fiber coupler; the optical detector detects and obtains an interference signal, and transmits the interference signal to the signal processing unit; the signal processing unit demodulates the interference signal to obtain a signal to be detected and a carrier modulation signal, and inputs the carrier modulation signal to the lithium niobate y waveguide modulator so that the lithium niobate y waveguide modulator modulates the light waves which interfere with each other.

Optionally, an optical isolator is disposed between the light source assembly and the fiber coupler.

Optionally, a depolarizer is arranged between the second end of the optical fiber coupler and the optical signal input end of the lithium niobate y waveguide modulator; a first depolarizer is arranged between the first output end of the lithium niobate y waveguide modulator and the first end part of the first optical fiber; a second depolarizer is arranged between the second output end of the lithium niobate y waveguide modulator and the first end part of the second optical fiber;

The second end of the optical fiber coupler is connected with the depolarizer through a single mode optical fiber; the depolarizer is connected with the optical signal input end of the lithium niobate y waveguide modulator through a polarization maintaining fiber;

The first depolarizer is connected with the first output end of the lithium niobate y waveguide modulator, and the second depolarizer is connected with the second output end of the lithium niobate y waveguide modulator through polarization maintaining optical fibers.

Optionally, the signal processing unit comprises an A/D conversion circuit, an FPGA signal processing unit and a D/A conversion circuit;

Wherein, the input end of the A/D conversion circuit is connected with the output end of the optical detector; the output end of the A/D conversion circuit is connected with the input end of the FPGA signal processing unit; the output end of the FPGA signal processing unit is connected with the input end of the D/A conversion circuit; and the output end of the D/A conversion circuit is connected with the modulation signal input end of the lithium niobate y waveguide modulator.

The utility model provides an optical fiber accelerometer probe and an acceleration sensing system; the optical fiber accelerometer probe is applied to an acceleration sensing system and comprises a mass block; the first elastic column body and the second elastic column body are arranged at two ends of the mass block; the first optical fiber and the second optical fiber are respectively wound on the first elastic column body and the second elastic column body; a first reflective element disposed at a second end of the first optical fiber; a second reflective element disposed at a second end of the second optical fiber; the first end of the first optical fiber and the first end of the second optical fiber are connected with a light source assembly and a light detector in the acceleration sensing system through the light path assembly, so that light rays output by the light source assembly are divided into two paths of coherent light rays through the light path assembly and are respectively input into the first optical fiber and the second optical fiber, and the light rays reflected by the first reflecting element and the second reflecting element are conducted to the light detector after being interfered by the light path assembly.

In the optical fiber accelerometer probe, a first elastic column body and a second elastic column body are respectively arranged at two ends of a mass block, and a first optical fiber and a second optical fiber are respectively wound on the first elastic column body and the second elastic column body; simultaneously, a first reflecting element and a second reflecting element are respectively arranged at the second end part of the first optical fiber and the second end part of the second optical fiber; therefore, in the actual surveying process, when the surveying position vibrates to drive the mass block to vibrate, the first elastic column body and the second elastic column body are required to be stretched and the second elastic column body is required to be compressed to deform reversely, correspondingly, the lengths of the first optical fiber and the second optical fiber are also required to be stretched and the length of the first optical fiber and the length of the second optical fiber are required to be shortened to change reversely, namely, larger optical path difference is generated between two paths of light rays which are respectively incident to the first optical fiber and the second optical fiber and transmitted by the first optical fiber and the second optical fiber after being reflected by the first reflecting element and the second reflecting element, and the optical fiber accelerometer probe is enabled to be more sensitive to vibration detection of the surveying position.

And in a preferred embodiment of the application, a y-waveguide integrated phase modulator is used for replacing the internal modulation of a light source or the external modulation of PZT in the phase generation carrier demodulation in an acceleration sensing system comprising the optical fiber accelerometer probe, so that the dynamic range of low-frequency detection is improved to a certain extent.

Drawings

For a clearer description of embodiments of the utility model or of the prior art, the drawings that are used in the description of the embodiments or of the prior art will be briefly described, it being apparent that the drawings in the description below are only some embodiments of the utility model, and that other drawings can be obtained from them without inventive effort for a person skilled in the art.

FIG. 1 is a schematic cross-sectional view of a fiber optic accelerometer probe according to an embodiment of the application;

FIG. 2 is a schematic diagram of a partial perspective structure of a fiber optic accelerometer probe according to an embodiment of the application;

Fig. 3 is a schematic structural diagram of an acceleration sensing system according to an embodiment of the present application.

Detailed Description

Based on the principle of optical fiber interferometry, in an acceleration sensing system, two paths of interference arms are generally required to be arranged. When the optical fiber accelerometer probe in the acceleration sensing system vibrates along with the measured object, the optical path of one interference arm is unchanged, the optical path of the other interference arm is changed, so that the optical path difference of the light rays in the two interference arms is generated, the phases of the two light rays are correspondingly changed, and a phase difference is formed. And determining the vibration acceleration of the measured object according to the change rule of the phase difference of the two paths of light rays. However, if the vibration amplitude of the measured object is low, the optical path difference of the corresponding two paths of light rays is relatively small and difficult to detect, and the sensitivity of the fiber optic accelerometer probe survey can be affected to a certain extent.

Therefore, the application provides a technical scheme capable of improving the sensitivity of the optical fiber accelerometer probe.

In order to better understand the aspects of the present utility model, the present utility model will be described in further detail with reference to the accompanying drawings and detailed description. It will be apparent that the described embodiments are only some, but not all, embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Referring to fig. 1 and 2, fig. 1 is a schematic cross-sectional structure of a fiber optic accelerometer probe according to an embodiment of the application; fig. 2 is a schematic diagram of a partial perspective structure of a fiber optic accelerometer probe according to an embodiment of the application.

It will be appreciated that the fibre optic accelerometer probe of the present application is applicable to acceleration sensing systems. In one embodiment of the application, the fiber optic accelerometer probe may comprise:

A mass 10; a first elastic column 11 and a second elastic column 12 disposed at both ends of the mass 10; a first optical fiber 13 and a second optical fiber 14 wound around the first elastic cylinder 11 and the second elastic cylinder 12, respectively; a first reflecting element 15 disposed at a second end of the first optical fiber 13; a second reflective element 16 disposed at a second end of the second optical fiber 14;

The first end of the first optical fiber 13 and the first end of the second optical fiber 14 are connected with a light source assembly and a light detector in the acceleration sensing system through the light path assembly, so that light rays output by the light source assembly are divided into two paths of coherent light rays through the light path assembly and are respectively input into the first optical fiber 13 and the second optical fiber 14, and the light rays reflected by the first reflecting element 15 and the second reflecting element 16 are conducted to the light detector after interference of the light path assembly.

It will be appreciated that the optical path assembly in this embodiment should be an optical path element that includes a light path capable of dividing the light beam output from the light source assembly into two coherent light beams, and should also include an optical path element that is capable of combining the light beams respectively output from the first end portion of the first optical fiber 13 and the first end portion of the second optical fiber 14 of the fiber optic accelerometer probe so that the two light beams interfere with each other.

When the optical fiber accelerometer probe in this embodiment is applied to an acceleration sensing system, structural components of the acceleration sensing system other than the optical fiber accelerometer probe may refer to structural components of a conventional optical fiber sensor formed based on michael interference principle, which is not particularly limited in this embodiment.

The mass block 10 in the optical fiber accelerometer probe in the embodiment is made of a material with higher density; for example, a manganese brass block may be used. Of course, the mass 10 of other materials is not excluded in this embodiment; as long as the mass size is large enough under the condition of small volume; it is sufficient to ensure that when the fibre optic accelerometer probe is placed in a survey environment, the mass 10 will vibrate with the vibrations of the survey environment.

The two ends of the mass block 10 are respectively provided with a first elastic column 11 and a second elastic column 12, and the two ends of the mass block 10 can be respectively bonded with the first elastic column 11 and the second elastic column 12 through metal silica gel adhesives. The first elastic column 11 and the second elastic column 12 should be column structures which can be deformed under stress, and the first elastic column 11 and the second elastic column 12 can use 601 silica gel with low Young's modulus to increase the sensitivity, and can also use other types of silica gel or rubber. When the mass block 10 vibrates along with the survey environment, if the mass block 10 moves to one side of the first elastic column 11, the first elastic column 11 is extruded to radially expand and thicken the first elastic column 11, and the second elastic column 12 is stretched to thin the second elastic column 12; the first optical fiber 13 wound around the first elastic column 11 is elongated as the first elastic column 11 becomes thicker and the refractive index is changed, while the second optical fiber 14 wound around the second elastic column 12 is shortened as the second elastic column 12 becomes thinner and the refractive index is changed opposite to that of the first optical fiber 13. The light transmitted in the first optical fiber 13 is transmitted to the second end of the first optical fiber 13 through the entire first optical fiber 13 after being incident from the first end of the first optical fiber 13 and is reflected by the first reflecting element 15, and then is transmitted to the first end of the first optical fiber 13 again through the first optical fiber 13, so that the optical path length of the light transmitted in the first optical fiber 13 is twice the length of the first optical fiber 13; similarly, the light transmitted in the second optical fiber 14 is transmitted to the second end of the second optical fiber 14 after being incident from the first end of the second optical fiber 14, and is retransmitted to the first end of the second optical fiber 14 after being reflected by the second reflecting element 16, so that the optical path length of the light transmitted in the second optical fiber 14 is twice the length of the second optical fiber 14; thus, when the first optical fiber 13 is elongated and the length is increased and the refractive index is correspondingly changed, and the second optical fiber 14 is contracted and the length is reduced and the refractive index is changed, the optical path difference between the light rays output by the first end parts of the two optical fibers can be made to be the superposition of the optical path changes of the two light rays; accordingly, the phase difference between the light rays outputted from the first end portion of the first optical fiber 13 and the first end portion of the second optical fiber 14 is relatively larger.

Similarly, when the mass block 10 vibrates to one side of the second elastic column 12, the first elastic column 11 is stretched to compress the second elastic column 12, and accordingly, the length of the first optical fiber 13 is shortened and the length of the second optical fiber 14 is lengthened, and the phase difference between the light rays transmitted in the first optical fiber 13 and the second optical fiber 14 is the same as the accumulation of the phase change of the two paths of light rays, so that a relatively increased phase difference can be generated.

In practical applications, taking the first elastic column 11 and the second elastic column 12 as cylinders with the same size and shape, the first optical fiber 13 and the second optical fiber 14 are optical fiber accelerometer probes with the same length, when the optical fibers are strained, the optical fiber length and the refractive index of the optical fiber accelerometer probes are changed, so that the phase of the light transmitted in the optical fibers is changed, and the phase change can be expressed as: k ₀ =2pi/λ. Wherein lambda is the wavelength of incident light, n is the refractive index of the optical fiber, deltaL is the length change of the optical fiber, v is the Poisson's ratio of the optical fiber, and P ₁₁、P₁₂ is the photoelastic coefficient of the first optical fiber 13 and the photoelastic coefficient of the second optical fiber 14 respectively;

The equivalent elastic coefficient of each elastic column body in the optical fiber accelerometer probe is that Wherein pi is the circumference, b is the radius of the cross section of the elastic cylinder, E is the Young's modulus of the elastic cylinder, H is the height of the elastic cylinder, mu is the Poisson's ratio of the elastic cylinder, K _fn =Y.A, Y is the Young's modulus of the optical fiber, A is the cross section area of the optical fiber, N is the number of turns of the elastic cylinder corresponding to the winding of the optical fiber, and/>The relation between the length change of the optical fiber and the height change of the corresponding elastic column body is as follows: /(I)L is the length of the optical fiber, and ΔH is the height variation of the elastic column.

From Hooke's lawAnd the relation between the phase change and the acceleration under the working frequency can be obtained by the optical fiber phase modulation mechanism as/>The sensitivity of the optical fiber accelerometer probe at the working frequency isNatural frequency is/>Where m is the mass of the mass 10 and m _cyl is the mass of the elastic column.

When the height of the elastic column body is 8mm and the radius of the cross section is 10mm, the natural frequency is greater than 500Hz, the working frequency range of the optical fiber accelerometer probe accords with the low-frequency geophone frequency range, the sensitivity of the accelerometer is 42.1511dB re rad/g, the natural frequency is 543.3653Hz, and the sensitivity of the accelerometer is improved on the premise of meeting the requirements of the underground low-frequency geophone size and frequency.

Based on the above discussion, in contrast to conventional fiber optic accelerometer probes, only the fiber optic as the interference arm is typically wound around the compliant material structure, and the fiber optic as the reference arm does not undergo a length stretching change with vibration of the proof mass 10. Therefore, in the optical fiber accelerometer probe of the present embodiment, along with the vibration of the surveying environment, the expansion and contraction changes of the two optical fibers of the first optical fiber 13 and the second optical fiber 14 can be simultaneously caused, even if the frequency is smaller and the vibration amplitude is smaller, the optical path difference between the light rays in the two optical fibers can generate a larger phase difference because the length and the refractive index of the first optical fiber 13 and the second optical fiber 14 are changed reversely, so that even if the surveying environment generates tiny vibration, the optical fiber accelerometer probe of the present embodiment can also cause the light rays transmitted by the first optical fiber 13 and the second optical fiber 14 in the optical fiber accelerometer probe to generate obvious phase difference, that is, the optical fiber accelerometer probe of the present embodiment is more sensitive to the vibration of the surveying environment.

In addition, the first elastic column 11 and the second elastic column 12 at two ends of the mass block 10 are both in columnar structures, so that variable deformation of the first elastic column 11 and the second elastic column 12 when being extruded or stretched can be further improved, further the phase difference change range between light rays transmitted in the first optical fiber 13 and the second optical fiber 14 is enlarged to a certain extent, and the sensitivity of the optical fiber accelerometer probe is ensured.

In addition, in the accelerometer sensitive probe of the embodiment, the first elastic column 11 and the second elastic column 12 are pushed and pulled by the mass block 10 to realize detection of acceleration signals, so that the transverse noise interference generated by the transverse vibration of the first elastic column 11 and the second elastic column 12 can be counteracted, and the anti-interference capability of the accelerometer sensitive probe is improved.

The first elastic column 11 and the second elastic column 12 in this embodiment may have a cylindrical structure, and of course, the present application does not exclude the use of a square column, an oval column, or other cylindrical structures.

It will be appreciated that, in general, the first elastic column 11 and the second elastic column 12 may have the same column structure, but in practical application, it is not excluded to provide two columns with different radii. And the cross-sectional radii of the first and second elastic columns 11 and 12 should be smaller than the cross-sectional radius of the mass 10. The mass 10 may be a cylinder with a cross-sectional radius of 14mm to 16mm, and in particular, the mass 10 may have a cross-sectional radius of 15mm; in addition, the total height of the mass block 10, the first elastic column 11 and the second elastic column 12 is 28-32 mm, so that the overall structure size of the optical fiber accelerometer probe is relatively small on the basis that the optical fiber accelerometer probe meets the survey requirement.

G657.a2 bending-resistant optical fibers may be employed for the first optical fibers 13 wound around the first and second elastic columns 11 and 12, respectively. It will be appreciated that the first optical fiber 13 is wound around the first elastic column 11 and the second optical fiber 14 is wound around the second elastic column 12 in a plurality of turns, so that the lengths of the first optical fiber 13 and the second optical fiber 14 are more varied with the deformation of the first elastic column 11 and the second elastic column 12. And the surfaces of the first optical fiber 13 and the second optical fiber 14 may be coated with a silica gel adhesive to increase the degree of coupling between the optical fibers and the elastic column.

In addition, the first reflecting element 15 disposed at the second end portion of the first optical fiber 13 and the second reflecting element 16 disposed at the second end portion of the second optical fiber 14 may employ a common mirror, and may employ a faraday rotator mirror whose insertion loss is small, and may provide a high signal-to-noise ratio.

Further, in order to ensure stability of the fiber optic accelerometer probe, in another alternative embodiment of the present application, it may further include:

The mass block 10, the first elastic column 11 and the second elastic column 12 are all encapsulated in a cylindrical shell 17, and aluminum covers 18 are arranged at two ends of the cylindrical shell 17 and are used for forming a closed cavity together with the cylindrical shell 17;

And, two cylindricality shells 17 respectively with first elastic column 11 and second elastic column 12 face away from the terminal laminating connection of quality piece 10.

As shown in fig. 1 and 2, aluminum covers 18 are respectively arranged at two ends of a cylindrical shell 17, the cylindrical shell 17 is fastened and connected with the aluminum covers 18 through screws to form an integrated packaging structure, and pretightening force is applied to the accelerometer sensitive probe, so that system stability is enhanced.

In summary, in the optical fiber accelerometer probe of the present application, the first elastic column and the second elastic column are respectively disposed at two ends of the mass block, in the actual surveying process, when the surveying position vibrates to drive the mass block to vibrate, the first elastic column and the second elastic column inevitably generate a reverse deformation of stretching and compressing one by one, correspondingly, the lengths of the first optical fiber and the second optical fiber respectively wound on the first elastic column and the second elastic column generate a reverse change of stretching and shrinking, and the refractive index also generates a reverse increase and decrease, so that the optical path difference between the two paths of light rays respectively transmitted in the first optical fiber and the second optical fiber is the superposition of the optical path changes of the two paths of light rays, even if the surveying environment generates a slight vibration, the optical path difference between the two paths of light rays can generate an obvious optical path difference, and the sensitivity of the optical fiber accelerometer probe is improved to a certain extent.

Fig. 3 is a schematic structural diagram of an acceleration sensing system according to an embodiment of the present application, as shown in fig. 3. The application further provides an embodiment of an acceleration sensing system, which may include the optical fiber accelerometer probe as described in any one of the above, and further includes a light source assembly 21, a light detector 28, an optical path assembly and a signal processing unit;

In this embodiment, the output end of the light source assembly 21 and the input end of the light detector 28 are respectively connected with the optical fiber accelerometer probe 100 through an optical path assembly; the optical path assembly should be an optical path element capable of dividing the light outputted from the light source assembly 21 into two coherent light rays, and should also be an optical path element capable of combining the light rays outputted from the first end portion of the first optical fiber 13 and the first end portion of the second optical fiber 14 of the optical fiber accelerometer probe 100, respectively, so that the two light rays interfere with each other; and the output of the photodetector 28 is connected to the input of the signal processing unit.

Thus, the light beam output by the light source component 21 is divided into two paths of coherent light beams by the light path component and respectively enters the first optical fiber 13 and the second optical fiber 14 of the optical fiber accelerometer probe 100, the two paths of coherent light beams respectively enter the light path component after being reflected by the first reflecting element 15 and the second reflecting element 16 of the optical fiber accelerometer probe 100, and enter the light detector 28 after being interfered in the light path component, the light detector 28 detects and photoelectrically converts the interference light wave, and the converted electric signal is transmitted to the signal processing unit so that the signal processing unit processes the detected signal. For the acceleration sensing system in this embodiment, structural components other than the optical fiber accelerometer probe 100 may be referred to as structural components of a conventional optical fiber sensor formed based on michael interference principle, and the present embodiment is not particularly limited.

In another alternative embodiment of the application, the optical path component may include a fiber coupler 23 and a lithium niobate y-waveguide modulator 25;

Wherein the output end of the light source assembly 21 is connected with the first end of the optical fiber coupler 23; a second end of the optical fiber coupler 23 is connected with an optical signal input end of the lithium niobate y waveguide modulator 25; the first output end and the second output end of the lithium niobate y waveguide modulator 25 are respectively connected with the first end of the first optical fiber 13 and the first end of the second optical fiber 14 in the optical fiber accelerometer probe 100; the third end of the optical fiber coupler 23 is connected with the input end of the optical detector 28; the output end of the optical detector 28 is connected with the input end of the signal processing unit; the output end of the signal processing unit is connected with the modulation signal input end of the lithium niobate y waveguide modulator 25;

The light output by the light source assembly 21 is transmitted to the lithium niobate y waveguide modulator 25 through the optical fiber coupler 23, the lithium niobate y waveguide modulator 25 splits the light into two paths of coherent light beams which are respectively incident to the first optical fiber 13 and the second optical fiber 14, the two paths of coherent light beams are respectively transmitted to the first reflecting element 15 and the second reflecting element 16 in the optical fiber accelerometer probe 100, reflected by the first optical fiber 13 and the second optical fiber 14, and are incident into the lithium niobate y waveguide modulator 25, and mutual interference occurs in the lithium niobate y waveguide modulator 25; the light waves interfering with each other are transmitted to the light detector 28 through the optical fiber coupler 23; the photodetector 28 detects the obtained interference signal and transmits the interference signal to the signal processing unit; the signal processing unit demodulates the interference signal to obtain a signal to be detected and a carrier modulation signal, and inputs the carrier modulation signal to the lithium niobate y waveguide modulator 25 so that the lithium niobate y waveguide modulator 25 modulates the optical wave which interferes with each other.

As shown in fig. 3, the optical fiber coupler 23 in the present embodiment may be a 2*1 optical fiber coupler, in which the first end and the third end of the optical fiber coupler 23 are located on the same side, and the first end of the optical fiber coupler 23 is connected to the output end of the light source assembly 21; thus, the light outputted from the light source assembly 21 can be inputted from the first end of the optical fiber coupler 23 and outputted from the second end; and the second end of the optical fiber coupler 23 is connected to the optical signal input end of the lithium niobate y-waveguide modulator 25, thereby causing the light outputted from the second end of the optical fiber coupler 23 to be incident on the lithium niobate y-waveguide modulator 25; based on the light splitting characteristic of the lithium niobate y waveguide modulator 25, the light is divided into two paths of coherent light in the lithium niobate y waveguide modulator 25, and the two paths of coherent light are output from a first output end and a second output end of the lithium niobate y waveguide modulator 25 respectively; the first output end of the lithium niobate y waveguide modulator 25 is connected to the first end of the first optical fiber 13 of the optical fiber accelerometer probe 100, and the second output end of the lithium niobate y waveguide modulator 25 is connected to the first end of the second optical fiber 14 of the optical fiber accelerometer probe 100, so that two paths of coherent light rays can be respectively incident to the first reflecting element 15 and the second reflecting element 16 through the conduction of the first optical fiber 13 and the second optical fiber 14, respectively reflected by the first reflecting element 15 and the second reflecting element 16, and then are again incident to the first output end and the second output end of the lithium niobate y waveguide modulator 25 through the first end of the first optical fiber 13 and the first end of the second optical fiber 14; the two coherent light beams re-enter the lithium niobate y waveguide modulator 25 and then interfere with each other, and the light waves with mutual interference can be transmitted to the second end of the optical fiber coupler 23, from the second end of the optical fiber coupler 23 to the third end of the optical fiber coupler 23, and enter the photodetector 28; the interference of the two paths of coherent light rays can be detected through the light detector 28; when there is a phase difference between the two coherent light beams, the interference conditions generated are different along with the difference of the phase differences, so that the photodetector 28 outputs a corresponding electric signal to the signal processing unit according to the detected interference light wave; the signal processing unit carries out demodulation operation on the electric signal, and a signal to be detected (namely, a signal representing the vibration acceleration of the accelerometer probe) and a carrier modulation signal can be obtained; the signal processing unit inputs the carrier modulation signal to the lithium niobate y waveguide modulator 25, and the lithium niobate y waveguide modulator 25 can phase modulate the two paths of light within the lithium niobate y waveguide modulator 25 based on the carrier modulation signal.

In the acceleration sensing system of the present application, the lithium niobate y waveguide modulator 25 is used instead of the light source internal modulation or PZT external modulation in the phase generation carrier demodulation, and the dynamic range of the low-frequency detection can be improved to some extent.

In practical applications, the signal processing unit may specifically be composed of an a/D conversion circuit 29, an FPGA signal processing unit 210, and a D/a conversion circuit 211;

Wherein the input end of the A/D conversion circuit 29 is connected with the output end of the photodetector; the output end of the A/D conversion circuit 29 is connected with the input end of the FPGA signal processing unit 210; the output end of the FPGA signal processing unit 210 is connected with the input end of the D/A conversion circuit 211; an output terminal of the D/a conversion circuit 211 is connected to a modulation signal input terminal of the lithium niobate y-waveguide modulator 25.

The electrical signal output from the photodetector 28 is an analog signal, the analog signal is input to the a/D conversion circuit 29, the a/D conversion circuit 29 converts the analog signal into a digital signal, the FPGA signal processing unit 210 performs demodulation operation based on the digital signal to obtain an acceleration signal to be measured, the carrier modulation signal is input to the D/a conversion circuit 211, and the analog signal is converted by the D/a conversion circuit 211 to be input to the lithium niobate y waveguide modulator 25.

Of course, in practical application, the output end of the signal processing unit may be further connected to a PC host or a display device, for outputting real-time acceleration information of the survey environment; the acceleration signal may be specifically output in real time by the FPGA signal processing unit 210.

From the overall structure of the acceleration sensing system, the interference signal detected by the photodetector 28 can be expressed as: wherein A is the direct current component of the interference light intensity, B is the alternating current component of the interference light intensity, The phase modulation introduced for the lithium niobate y waveguide modulator 25, C is the modulation depth, f _c is the modulation frequency, V is the voltage applied to the modulator, V _π is the half-wave voltage (the voltage required for phase delay pi); the modulation effect of the lithium niobate y waveguide modulator 25 becomes 2 times due to the michelson interference structure; /(I)The phase difference of the two interfering arms, which is caused by acceleration, is related to the structure of the fiber optic accelerometer probe 100. The phase change/>, caused by acceleration to be measured, can be demodulated through a carrier demodulation algorithm generated by proper phase after the interference signal is subjected to photoelectric conversion

It should be noted that, the demodulation operation performed by the signal processing unit in this embodiment, that is, the operation process of the conventional phase-generated carrier (phase-GENERATED CARRIER, abbreviated as PGC) demodulation algorithm at present, for example, may be a PGC-DCM algorithm, or a PGC-Arctan algorithm, or may be the operation process of other demodulation algorithms; the present utility model is not particularly limited in this regard, and reference may be made specifically to the operation procedure of the PGC demodulation algorithm currently in common use. It can be understood that the demodulation operation process implemented by the signal processing unit is not improved in operation program, but only the signal processing unit capable of implementing conventional demodulation operation is adopted to cooperate with other components in the utility model to implement the technical scheme of the utility model. Therefore, the acceleration sensing system in the utility model meets the requirements of the protection object of the utility model.

In the embodiment, the carrier modulation signal frequency is considered to be larger than twice of the product of the amplitude of the phase change and the frequency caused by the acceleration signal, and the lithium niobate y waveguide modulator 25 is used for carrying out phase modulation, so that the modulation frequency can reach the MHz level, and the acceleration amplitude and the frequency range detected by the acceleration sensing system are improved; and the use of the lithium niobate y waveguide modulator 25 can ensure that the two interference arms are equal in length, and an unbalanced interferometer caused by the addition of a phase modulator is avoided, so that the phase noise of the light source assembly 21 is reduced.

On the basis, in order to further improve the detection precision of the acceleration sensing system, in another alternative embodiment of the present application, an optical isolator 22 may be further disposed between the light source assembly 21 and the optical fiber coupler 23, so as to prevent the interference light reflected by the first reflecting element and the second reflecting element from damaging the light source assembly 21.

In another alternative embodiment of the present application, it may further include:

A depolarizer 24 is arranged between the second end of the optical fiber coupler 23 and the optical signal input end of the lithium niobate y waveguide modulator 25; a first depolarizer 26 is arranged between the first output end of the lithium niobate y-waveguide modulator 25 and the first end of the first optical fiber 13; a second depolarizer 27 is provided between the second output of the lithium niobate y-waveguide modulator 25 and the first end of the second optical fiber 14.

The second end of the optical fiber coupler 23 is connected with the depolarizer 24 through a single mode optical fiber; the depolarizer 24 is connected with the optical signal input end of the lithium niobate y waveguide modulator 25 through polarization maintaining optical fibers;

The first depolarizer 26 and the first output terminal of the lithium niobate y waveguide modulator 25, and the second depolarizer 27 and the first output terminal of the lithium niobate y waveguide modulator 25 are connected by polarization maintaining fibers.

In this embodiment, the optical fibers connected to the input end and the output end of the depolarizer 24 are a single-mode optical fiber and a polarization maintaining optical fiber, so that the light transmitted by the single-mode optical fiber can be depolarized, and the light after being depolarized is transmitted to the lithium niobate y waveguide modulator 25 through the polarization maintaining optical fiber, so that the optical fiber incident to the lithium niobate y waveguide modulator 25 is ensured to be in a non-polarized state; the lithium niobate y waveguide modulator 25 can perform phase modulation in phase generation carrier demodulation according to the carrier modulation signal generated by the signal processing unit, and the optical fibers connected to the first output end and the second output end of the lithium niobate y waveguide modulator 25 are all polarization maintaining optical fibers, so that the first depolarizer 26 and the second depolarizer 27 are respectively added to the first output end and the second output end of the lithium niobate y waveguide modulator 25, and the polarization influence of the reflected light can be eliminated. Except the optical signal input end and the optical fibers of the two output ends of the lithium niobate y waveguide modulator 25, all other optical fiber devices adopt single-mode optical fibers, and the cost of the acceleration sensing system is reduced on the basis of ensuring the accuracy of the acceleration sensing system.

It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is inherent to. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. In addition, the parts of the above technical solutions provided in the embodiments of the present application, which are consistent with the implementation principles of the corresponding technical solutions in the prior art, are not described in detail, so that redundant descriptions are avoided.

The principles and embodiments of the present utility model have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present utility model and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the utility model can be made without departing from the principles of the utility model and these modifications and adaptations are intended to be within the scope of the utility model as defined in the following claims.

Claims (10)

1. The optical fiber accelerometer probe is characterized by being applied to an acceleration sensing system and comprising a mass block; the first elastic column body and the second elastic column body are arranged at two ends of the mass block; a first optical fiber and a second optical fiber wound around the first elastic column and the second elastic column, respectively; a first reflective element disposed at a second end of the first optical fiber; a second reflective element disposed at a second end of the second optical fiber;

the first end of the first optical fiber and the first end of the second optical fiber are connected with a light source assembly and a light detector in the acceleration sensing system through a light path assembly, so that light rays output by the light source assembly are divided into two paths of coherent light rays through the light path assembly and are respectively input into the first optical fiber and the second optical fiber, and the light rays reflected by the first reflecting element and the second reflecting element are conducted to the light detector after being interfered with each other through the light path assembly.

2. The fiber optic accelerometer probe of claim 1, wherein the first reflective element and the second reflective element are both faraday rotator mirrors.

3. The fiber optic accelerometer probe of claim 1, wherein the first elastic column and the second elastic column are both silica gel; the mass block is a manganese brass structure block; the first optical fiber and the second optical fiber are g657.a2 bending resistant optical fibers.

4. A fibre optic accelerometer probe according to claim 3, wherein the mass is a cylinder with a cross-sectional radius of 14mm to 16 mm; the first elastic column body and the second elastic column body are both cylinders with the cross-sectional radius smaller than that of the mass block; the total height of the mass block and the first elastic column body and the second elastic column body is 28 mm-32 mm.

5. The fiber optic accelerometer probe of claim 1, wherein the mass, the first elastic column and the second elastic column are all encapsulated in a cylindrical housing, and aluminum covers are arranged at two ends of the cylindrical housing for forming a closed cavity together with the cylindrical housing;

And the two cylindrical shells are respectively in fit connection with the end parts of the first elastic column body and the second elastic column body, which deviate from the mass block.

6. An acceleration sensing system comprising a fibre optic accelerometer probe according to any one of claims 1 to 5; the light source component, the light detector, the light path component and the signal processing unit; the output end of the light source component and the input end of the optical detector are respectively connected with the optical fiber accelerometer probe through the optical path component; the output end of the optical detector is connected with the input end of the signal processing unit;

The light output by the light source assembly is divided into two paths of coherent light through the light path assembly and respectively enters the first optical fiber and the second optical fiber of the optical fiber accelerometer probe, the two paths of coherent light respectively enter the light path assembly after being reflected by the first reflecting element and the second reflecting element of the optical fiber accelerometer probe, and enter the light detector after being interfered in the light path assembly, the light detector detects and photoelectrically converts interference light waves, and the converted electric signals are transmitted to the signal processing unit, so that the signal processing unit processes the detected signals.

7. The acceleration sensing system of claim 6, wherein the optical path component comprises a fiber coupler and a lithium niobate y waveguide modulator;

The output end of the light source component is connected with the first end of the optical fiber coupler; the second end of the optical fiber coupler is connected with the optical signal input end of the lithium niobate y waveguide modulator; the first output end and the second output end of the lithium niobate y waveguide modulator are respectively connected with the first end part of the first optical fiber and the first end part of the second optical fiber in the optical fiber accelerometer probe; the third end of the optical fiber coupler is connected with the input end of the optical detector; the output end of the optical detector is connected with the input end of the signal processing unit; the output end of the signal processing unit is connected with the modulation signal input end of the lithium niobate y waveguide modulator;

The light output by the light source assembly is transmitted to the lithium niobate y waveguide modulator through the optical fiber coupler, the lithium niobate y waveguide modulator splits the light into two paths of coherent light rays which are respectively incident to the first optical fiber and the second optical fiber, the two paths of coherent light rays are respectively transmitted to a first reflecting element and a second reflecting element in the optical fiber accelerometer probe, reflected and are incident into the lithium niobate y waveguide modulator through the first optical fiber and the second optical fiber, and mutual interference occurs in the lithium niobate y waveguide modulator; the light waves which interfere with each other are transmitted to the light detector through the optical fiber coupler; the optical detector detects and obtains an interference signal, and transmits the interference signal to the signal processing unit; the signal processing unit demodulates the interference signal to obtain a signal to be detected and a carrier modulation signal, and inputs the carrier modulation signal to the lithium niobate y waveguide modulator so that the lithium niobate y waveguide modulator modulates the light waves which interfere with each other.

8. The acceleration sensing system of claim 7, wherein an optical isolator is provided between the light source module and the fiber optic coupler.

9. The acceleration sensing system of claim 7 or 8, characterized in, that a depolarizer is arranged between the second end of the fiber coupler and the optical signal input end of the lithium niobate y waveguide modulator; a first depolarizer is arranged between the first output end of the lithium niobate y waveguide modulator and the first end part of the first optical fiber; a second depolarizer is arranged between the second output end of the lithium niobate y waveguide modulator and the first end part of the second optical fiber;

The second end of the optical fiber coupler is connected with the depolarizer through a single mode optical fiber; the depolarizer is connected with the optical signal input end of the lithium niobate y waveguide modulator through a polarization maintaining fiber;

The first depolarizer is connected with the first output end of the lithium niobate y waveguide modulator, and the second depolarizer is connected with the second output end of the lithium niobate y waveguide modulator through polarization maintaining optical fibers.

10. The acceleration sensing system of claim 7, wherein the signal processing unit comprises an a/D conversion circuit, an FPGA signal processing unit, and a D/a conversion circuit;

Wherein, the input end of the A/D conversion circuit is connected with the output end of the optical detector; the output end of the A/D conversion circuit is connected with the input end of the FPGA signal processing unit; the output end of the FPGA signal processing unit is connected with the input end of the D/A conversion circuit; and the output end of the D/A conversion circuit is connected with the modulation signal input end of the lithium niobate y waveguide modulator.