CN111982267A - Optical fiber sensor for sound wave and vibration measurement and working method thereof - Google Patents
Optical fiber sensor for sound wave and vibration measurement and working method thereof Download PDFInfo
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- CN111982267A CN111982267A CN202010807920.XA CN202010807920A CN111982267A CN 111982267 A CN111982267 A CN 111982267A CN 202010807920 A CN202010807920 A CN 202010807920A CN 111982267 A CN111982267 A CN 111982267A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 32
- 238000005259 measurement Methods 0.000 title claims abstract description 17
- 238000000034 method Methods 0.000 title claims description 7
- 230000003287 optical effect Effects 0.000 claims abstract description 30
- 230000003068 static effect Effects 0.000 claims abstract description 6
- 230000005540 biological transmission Effects 0.000 claims abstract description 4
- 239000000835 fiber Substances 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 7
- 239000010453 quartz Substances 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 238000001514 detection method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000007812 deficiency Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000003209 petroleum derivative Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
Abstract
The invention discloses an optical fiber sensor for sound wave and vibration measurement, which comprises a sensing head shell, a micro optical beam splitter and a cantilever beam, wherein the sensing head shell is provided with a sensing head cavity; the micro optical beam splitter is embedded in the bottom of the sensing head shell, and the cantilever beam is arranged at the top of the sensing head shell and forms a closed space with the sensing head shell; when a beam of laser enters the micro optical beam splitter through the optical fiber, two beams of light with mutually perpendicular directions are generated in the optical fiber sensor through the micro optical beam splitter, because the transmission and reflection of the semi-transparent and semi-reflective mirror and the reflection of the cantilever beam and the total-reflective mirror, the optical path difference can be generated when the two beams of light are reflected back to the optical fiber, and the distance between the semi-transparent and semi-reflective mirror and the total-reflective mirror is fixed during working, the determined optical path difference can be obtained by utilizing the structure of the micro optical beam splitter, so that the problem that the optimal static working point drifts due to the change of the optical path difference under the change of the ambient temperature is solved.
Description
Technical Field
The invention relates to the field of sensors, in particular to an optical fiber sensor for sound wave and vibration measurement.
Background
Compared with an electronic sensor, the interference-intensity modulation type optical fiber sensor has the advantages of small volume, simple structure, high sensitivity, high temperature and high pressure resistance, corrosion resistance, electromagnetic interference resistance, capability of forming an optical fiber sensing network and the like in the aspects of sound wave and vibration measurement. Therefore, the method has wide application in the fields of acoustic wave sensing, monitoring of petroleum and natural gas pipeline transportation with a severe environment, building structure health monitoring, medical diagnosis, safety interception with high requirement on anti-interference capability and the like.
However, the interference-intensity modulation type optical fiber sensor has a problem that the sensor operating point shifts due to environmental factors, which is the biggest obstacle in practical application of such a modulation method. For a two-beam interferometric modulation sensor, the interference spectrum is a cosine function, and the phase-intensity conversion curve is usually the segment of the cosine curve with the best linearity. When detecting an ac signal such as a sound wave, the static operating point is generally set at a phase point of pi/2 where the slope of the curve is the largest, also referred to as a Q point. Near the Q-point, the response of the small signal is linear and the sensitivity of the response is maximal. However, if the operating point deviates from the Q-point due to external factors, the sensitivity of the sensor decreases and a non-linear response occurs. Various proposals have been made to address the problem of drift in the operating point of interferometric-intensity modulated sensors, but none have overcome the drift in the Q-point in principle.
Disclosure of Invention
In view of the above-mentioned deficiencies of the prior art, the present invention provides an optical fiber sensor for measuring sound waves and vibrations, which can stably operate at an optimal static operating point even when the ambient temperature changes, thereby making up the deficiencies of the prior art.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
an optical fiber sensor for sound wave and vibration measurement comprises a sensing head shell, a micro optical beam splitter and a cantilever beam; the miniature optical beam splitter is embedded in the bottom of the sensing head shell, and the cantilever beam is arranged at the top of the sensing head shell and forms a closed space with the sensing head shell.
Furthermore, the micro beam splitter is composed of a half mirror and a full mirror which are parallel to each other.
Furthermore, the optical fiber is connected with the bottom of the shell of the sensing head, and the connection point is positioned below the semi-transparent semi-reflective mirror; the laser is divided into two directions perpendicular to each other by the half-transmitting and half-reflecting mirror.
Furthermore, two points are arranged at two ends of the cantilever beam, wherein one end is a vibration point, and the other end is a fixed point; the vibration point is influenced by the detection sound wave to generate vibration, so that the optical path is changed, and the detection sound wave intensity is obtained through processing.
Further, the semi-transparent semi-reflecting mirror and the total reflecting mirror are made of quartz; the quartz is not sensitive to temperature changes, so that the measurement accuracy is higher.
Furthermore, the cantilever beam is made of a sound-sensitive material and is sensitive to sound wave induction, and detection precision is improved.
Further, the transmission fiber is a common single mode fiber.
Further, the distance L between the half-mirror and the total-reflection mirror which are parallel to each other satisfies L ═ OPD/2n, wherein OPD is the optical path difference of a beam of laser which is incident to the half-mirror and the total-reflection mirror and returns to the incident point after being reflected and transmitted, and n is the refractive index of the material selected by the half-mirror and the total-reflection mirror; optical path difference
To target the phase difference, λ is the center wavelength of the laser light source.
The working method comprises the following steps:
s1, the laser is irradiated on the half mirror of the micro light beam splitter through the optical fiber; the semi-transparent semi-reflecting mirror divides the laser into two laser beams in the mutually vertical directions, wherein the laser beam in one direction is irradiated on the vibration point of the cantilever beam and then reflected back to the optical fiber, the light in the other direction is reflected to the fixed point of the cantilever beam through the fully reflecting mirror and then reflected back to the optical fiber, and the optical path difference OPD of the two laser beams is a determined value at the moment;
s2, recording the distance between the half mirror and the total reflection mirror as L, where the OPD is 2nL, and when the refractive indexes n of the half mirror and the total reflection mirror are the same, the optical path difference OPD is 2 times the distance between the half mirror and the total reflection mirror, and controlling the optical path difference OPD by adjusting the distance between the half mirror and the total reflection mirror;
S3、by phase difference
It is known that the phase difference can be adjusted by adjusting the distance L between the half mirror and the total mirror
The operating point is stabilized at the optimum static operating point.
The invention has the beneficial effects that: when a beam of laser enters the micro light beam splitter through the optical fiber, two beams of light with mutually perpendicular directions are generated in the optical fiber sensor through the micro light beam splitter, because the transmission and reflection of the semi-transparent and semi-reflective mirror and the reflection of the cantilever beam and the total-reflective mirror, the optical path difference can be generated when the two beams of light are reflected back to the optical fiber, and the distance between the semi-transparent and semi-reflective mirror and the total-reflective mirror is fixed during working, the determined optical path difference can be obtained by utilizing the structure of the micro light beam splitter, so that the change of the optical path difference under the change of the ambient temperature is eliminated, and the optical fiber sensor is ensured to work at the optimal static working point.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic diagram of a fiber optic sensor configuration and optical path for acoustic and vibration measurements;
FIG. 2 is a schematic diagram of a micro beam splitter in a fiber optic sensor configuration;
FIG. 3 is a schematic diagram of a cantilever beam of a fiber optic sensor structure.
Reference numbers and corresponding part names in the drawings:
1-optical fiber, 2-sensing head shell, 3-micro beam splitter, 4-cantilever beam, 5-two beams of laser, 6-vibration point, 7-fixed point, 8-semi-transparent semi-reflective mirror and 9-total reflective mirror.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1:
as shown in fig. 1, the optical fiber sensor for acoustic wave and vibration measurement of the present embodiment includes a sensing head housing 2, a micro beam splitter and a cantilever 4; the micro optical beam splitter 3 is embedded in the bottom of the sensing head shell 2, and the cantilever beam 4 is arranged at the top of the sensing head shell 2 and forms a closed space with the sensing head shell 2.
As shown in fig. 2, the micro beam splitter 3 is composed of a half mirror 8 and a full mirror 9 which are parallel to each other, the half mirror 8 and the full mirror 9 are made of quartz, but not limited to quartz, and the influence of temperature on quartz is small, so that the sensor is less influenced by the outside, and the measured data is more accurate; the optical fiber 1 is connected with the bottom of the sensing head shell 2, the connecting point is positioned below the semi-transparent semi-reflecting mirror 8, and the optical fiber 1 is selected to be a single-mode optical fiber.
As shown in fig. 3, two points are arranged at two ends of the cantilever beam 4, wherein one end is a vibration point 6, the other end is a fixed point 7, and the cantilever beam is made of a sound-sensitive material, which is beneficial to sensing the detected sound wave.
The working method of the sensor comprises the following steps: one beam of light is emitted to a semi-transparent semi-reflecting mirror 8 of the micro light beam splitter 3 through a single mode fiber, wherein the transmitted light is emitted to a cantilever beam vibration point 6, the reflected light is emitted to a cantilever beam fixed point 7 after being reflected by a full reflecting mirror 9, the two beams of light 5 are reflected back to the fiber 1 through a cantilever beam 4, and the optical path difference OPD of the two beams of light 5 is a determined value at the moment; the distance between the half mirror 8 and the total reflection mirror 9 is denoted as L, the OPD is 2nL, under the condition that the refractive indexes n of the materials of the half mirror 8 and the total reflection mirror 9 are the same, the optical path difference OPD and the distance L between the half mirror 8 and the total reflection mirror 9 are in 2-fold relationship, when the distance L between the half mirror 8 and the total reflection mirror 9 is determined, the optical path difference OPD can be determined, and the phase difference is determined
The phase difference can be adjusted by adjusting the distance L between the half mirror (8) and the total reflection mirror (9)
When L is determined, the phase difference
If the temperature of the working point is higher than the set temperature, the working point is shifted to the maximum extent.
Claims (9)
1. An optical fiber sensor for sound wave and vibration measurement, characterized by comprising a sensing head housing (2), a micro beam splitter (3) and a cantilever beam (4); the micro optical beam splitter (3) is embedded in the bottom of the sensing head shell (2), and the cantilever beam (4) is arranged at the top of the sensing head shell (2) and forms a closed space with the sensing head shell (2).
2. A fiber optic sensor for acoustic and vibration measurements according to claim 1, characterized in that the miniature beam splitter (3) is composed of a half-mirror (8) and a full-mirror (9) parallel to each other.
3. A fibre-optic sensor for acoustic and vibration measurements according to any of claims 1-2, characterized in that the optical fibre (1) is connected to the bottom of the sensor head housing (2) and the connection point is located below the half-mirror (8).
4. A fiber optic sensor for acoustic and vibration measurements according to claim 1, characterized in that the cantilever beam (4) is provided with two points at both ends, one end being a vibration point (6) and the other end being a fixed point (7).
5. A fiber optic sensor for acoustic and vibration measurements according to claim 2, characterized in that the semi-transparent and semi-reflective mirrors (8) and the total-reflective mirror (9) are made of quartz.
6. A fiber optic sensor for acoustic and vibration measurements according to claim 1, characterized in that the cantilever beam (4) is made of acoustically sensitive material.
7. A fiber optic sensor for acoustic and vibration measurements according to claim 3, characterized in that the optical fiber (1) is a plain single mode fiber.
8. An optical fiber sensor for sound and vibration measurement according to claim 2, characterized in that the distance L between the half mirror (8) and the half mirror (9) parallel to each other satisfies L-OPD/2 n, where OPD is the optical path difference between a laser beam incident on the half mirror (8) and the half mirror (9) after reflection and transmission and returning to the incident point, and n is the refractive index of the material selected for the half mirror (8) and the half mirror (9); optical path difference
To target the phase difference, λ is the center wavelength of the laser light source.
9. Method of operating a sensor according to any of claims 1 to 8, characterized in that it comprises the following steps:
s1, the laser is irradiated on the half-transmitting and half-reflecting mirror (8) of the micro light beam splitter (3) through the optical fiber (1); the semi-transmitting and semi-reflecting mirror (8) divides the laser into two laser beams (5) in the mutually perpendicular directions, wherein the laser beam in one direction is irradiated at a vibration point (6) of the cantilever beam (4) and then reflected back to the optical fiber (1), the light in the other direction is reflected to a fixed point (7) of the cantilever beam (4) through the fully reflecting mirror (9) and then reflected back to the optical fiber (1), and the optical path difference OPD of the two laser beams (5) is a determined value at the moment;
s2, recording the distance between the half mirror (8) and the total reflection mirror (9) as L, setting OPD as 2nL, and controlling the optical path difference OPD by adjusting the distance L between the half mirror (8) and the total reflection mirror (9) when the refractive indexes n of the materials of the half mirror (8) and the total reflection mirror (9) are the same, wherein the optical path difference OPD is in a 2-time relation with the distance L between the half mirror (8) and the total reflection mirror (9);
s3, calculating the phase difference
The phase difference can be adjusted by adjusting the distance L between the half mirror (8) and the total reflection mirror (9)
The operating point is stabilized at the optimum static operating point.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010807920.XA CN111982267A (en) | 2020-08-12 | 2020-08-12 | Optical fiber sensor for sound wave and vibration measurement and working method thereof |
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| CN202010807920.XA CN111982267A (en) | 2020-08-12 | 2020-08-12 | Optical fiber sensor for sound wave and vibration measurement and working method thereof |
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Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1392395A (en) * | 1971-07-07 | 1975-04-30 | Ibm | Stabilization of optical path length differences |
| CN201408305Y (en) * | 2009-05-19 | 2010-02-17 | 光库通讯(珠海)有限公司 | Differential phase shift keying signal demodulator |
| CN101782368A (en) * | 2010-03-03 | 2010-07-21 | 福州高意通讯有限公司 | Interferometer |
| CN102680073A (en) * | 2012-05-21 | 2012-09-19 | 天津大学 | Novel optical fiber vibration measurement instrument |
| US20130016940A1 (en) * | 2011-05-12 | 2013-01-17 | Korea Advanced Institute Of Science And Technology (Kaist) | Fiber optic sensor using transmissive grating panel and mirror |
| CN104808193A (en) * | 2015-04-29 | 2015-07-29 | 中国科学技术大学 | Non-polarization beam splitter-based Rayleigh scattering Doppler frequency discriminator for F-P (Fabry-Perot) etalons |
| CN106124028A (en) * | 2016-06-15 | 2016-11-16 | 北京理工大学 | A kind of micro-nano fiber vibrating sensor based on femtosecond laser parallel micromachining |
| CN107907203A (en) * | 2017-11-30 | 2018-04-13 | 大连理工大学 | A kind of demodulation method of optical fiber F P cavate sonic sensors |
| CN110553713A (en) * | 2018-05-30 | 2019-12-10 | 中国科学院电子学研究所 | Optical fiber ultrasonic sensor |
-
2020
- 2020-08-12 CN CN202010807920.XA patent/CN111982267A/en active Pending
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1392395A (en) * | 1971-07-07 | 1975-04-30 | Ibm | Stabilization of optical path length differences |
| CN201408305Y (en) * | 2009-05-19 | 2010-02-17 | 光库通讯(珠海)有限公司 | Differential phase shift keying signal demodulator |
| CN101782368A (en) * | 2010-03-03 | 2010-07-21 | 福州高意通讯有限公司 | Interferometer |
| US20130016940A1 (en) * | 2011-05-12 | 2013-01-17 | Korea Advanced Institute Of Science And Technology (Kaist) | Fiber optic sensor using transmissive grating panel and mirror |
| CN102680073A (en) * | 2012-05-21 | 2012-09-19 | 天津大学 | Novel optical fiber vibration measurement instrument |
| CN104808193A (en) * | 2015-04-29 | 2015-07-29 | 中国科学技术大学 | Non-polarization beam splitter-based Rayleigh scattering Doppler frequency discriminator for F-P (Fabry-Perot) etalons |
| CN106124028A (en) * | 2016-06-15 | 2016-11-16 | 北京理工大学 | A kind of micro-nano fiber vibrating sensor based on femtosecond laser parallel micromachining |
| CN107907203A (en) * | 2017-11-30 | 2018-04-13 | 大连理工大学 | A kind of demodulation method of optical fiber F P cavate sonic sensors |
| CN110553713A (en) * | 2018-05-30 | 2019-12-10 | 中国科学院电子学研究所 | Optical fiber ultrasonic sensor |
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