CN111442741A - Non-linear interference type bending sensor - Google Patents

Non-linear interference type bending sensor Download PDF

Info

Publication number
CN111442741A
CN111442741A CN202010435426.5A CN202010435426A CN111442741A CN 111442741 A CN111442741 A CN 111442741A CN 202010435426 A CN202010435426 A CN 202010435426A CN 111442741 A CN111442741 A CN 111442741A
Authority
CN
China
Prior art keywords
light
optical fiber
curvature
parametric amplifier
fiber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202010435426.5A
Other languages
Chinese (zh)
Inventor
倪智豪
王海龙
赵春柳
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
China Jiliang University
Original Assignee
China Jiliang University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by China Jiliang University filed Critical China Jiliang University
Priority to CN202010435426.5A priority Critical patent/CN111442741A/en
Publication of CN111442741A publication Critical patent/CN111442741A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)

Abstract

The invention provides a nonlinear interference type curvature sensor which comprises pump light, seed light, an optical fiber parameter amplifier (comprising two coarse wavelength division multiplexers and a dispersion displacement optical fiber), a curvature sensing element, a single mode optical fiber, a photoelectric detector, an oscilloscope and the like. The optical fiber parametric amplifier is characterized in that the wavelength (1550nm) of the pump light is located in an anomalous dispersion region of the dispersion shifted optical fiber, so that a phase matching condition can be met, and therefore a four-wave mixing effect in the optical fiber can occur. When the curvature of the single-mode fiber at the output end of the idler frequency light of the first fiber parametric amplifier is changed, part of the light intensity of the idler frequency light escapes into the cladding, so that the interference fringe contrast at the output end of the second fiber parametric amplifier is changed, the corresponding relation between the maximum value of the light intensity and the contrast and the curvature of the interference fringe can be obtained, and finally the curvature sensing with higher sensitivity is realized.

Description

Non-linear interference type bending sensor
Technical Field
The invention provides a nonlinear interference type bending sensor, and belongs to the technical field of optical fiber sensing.
Background
Since the measurement sensitivity of the conventional linear fiber interferometer is limited by the shot noise limit, in order to realize the sensing with higher sensitivity, quantum technology is required, that is, a nonlinear interferometer is used, which is different from the linear interferometer by the following steps: it uses nonlinear medium such as optical fiber parametric amplifier (FOPA) to replace traditional linear beam splitter, and can realize great improvement of sensitivity by inputting coherent state.
The invention utilizes the four-wave mixing effect in the optical fiber, which is a parametric amplification process caused by the optical third-order nonlinear effect. Its process can be described as follows: if two beams with different frequency components are co-propagating in the fiber, the two input frequency components are assumed to be v1And v2In the case of phase matching, two new frequency components v are then generated3、v4And satisfy the relation of conservation of energy between them v3+v4＝v1+v2。
The nonlinear interferometer can be applied to a plurality of sensing fields such as bending sensing, wherein the bending sensing is a technology for measuring the bending by utilizing the fact that when an optical fiber is bent, a part of fiber core energy can escape into a cladding so as to cause the loss of transmission light intensity of the optical fiber, and parameters (such as the maximum value of the light intensity and the contrast of interference fringes) are changed by measuring the change of the fiber core energy. The method is simple in technical implementation, so that the method is quite wide in practical application.
Disclosure of Invention
The invention aims to solve the problem that the measurement sensitivity of the existing linear interferometer is limited by the shot noise limit, and provides a nonlinear interference type curvature sensor.
The technical scheme adopted by the invention is as follows:
a nonlinear interference type curvature sensor comprises two beams of pump light, seed light, two optical fiber parameter amplifiers, a curvature sensing element, a single-mode optical fiber, a photoelectric detector and an oscilloscope; the connection mode is as follows: the curvature detection method comprises the steps that a first pumping light and a seed light are injected into a first optical fiber parametric amplifier, a single-mode optical fiber of an idler frequency optical channel output by the first optical fiber parametric amplifier is bent to form a curvature sensing element, a signal light output by the first optical fiber parametric amplifier, an idler frequency light passing through the curvature sensing element and a second pumping light are injected into a second optical fiber parametric amplifier, the signal light and the idler frequency light output by the second optical fiber parametric amplifier are connected with an oscilloscope through a photoelectric detector, and curvature detection can be achieved through analysis and display of the maximum light intensity value on the oscilloscope and the change of the contrast of interference fringes.
In the above technical solution, the optical fiber parametric amplifier is composed of two coarse wavelength division multiplexers and a dispersion shifted fiber located in the middle, and the wavelength 1550nm of the pump light is located in the anomalous dispersion region of the dispersion shifted fiber, which can satisfy the phase matching condition of four-wave mixing.
Compared with the prior art, the invention has the beneficial effects that:
1. compared with a linear interference type bending sensor, the sensor has higher sensitivity when the bending sensing is realized by utilizing the maximum value of the light intensity of the output light, and the sensitivity is 0-500m-1The sensitivity is improved by 5.855-5.928 times.
2. Two beams of light (signal light and idler light) are used in the sensor and combined organically, at 0-194.232m-1The signal light at the output end of FOPA2 is used at 194.232-500m-1The use of idler light at the output of the FOPA2 thus allows for accurate measurement of wide range bending.
Drawings
In order to more clearly illustrate the embodiment or technical solution of the present invention, the present invention is further described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of an application system of the present invention. Wherein, 1: pumping light I; 2: seed light; 3.5, 8, 10: a coarse wavelength division multiplexer; 4. 9: a dispersion shifted optical fiber; 6: a curvature sensing element; 7: pumping light II; 11. 12: a photodetector; 13: an oscilloscope.
FIG. 2 is a schematic diagram of the principle analysis of the sensor of the present invention, wherein (a) FOPA1 and FOPA2 form a nonlinear interferometer, (b) the diagram is a schematic diagram of a bending degree sensing element, the chord length of the bending part is 2L, and the chord height is d.
Fig. 3 is a schematic diagram of the principle of a linear interference type bending sensor (beamplitter (bs)) + beamplitter (bs) structure.
FIG. 4 is a graph at G1＝4,G23.5, the dependence of the maximum intensity at the output of the FOPA2 (signal and idler), the maximum intensity at the output of the linear interferometer, and the loss on curvature, where: the dotted line, the dot-dash line and the solid line (yellow) are respectively the dependency relationship of the maximum light intensity of the signal light at the output end of FOPA2, the idler light at the output end of FOPA2 and the output end of the linear interferometer on the curvature; the dotted line is the dependence of loss on curvature; the solid line (black) is the ratio of the maximum intensity of the idler light to the maximum intensity at the output of the linear interferometer.
FIG. 5 is a graph at G1＝4,G23.5, the first derivative of the maximum intensity at the output of the FOPA2 (signal and idler) and the maximum intensity at the output of the linear interferometer, is curvature dependent, where: the dotted line, the dash-dot line and the solid line respectively represent the dependence of the first derivative of the maximum intensity of the signal light at the output end of the FOPA2, the maximum intensity of the idler frequency light at the output end of the FOPA2 and the maximum intensity of the light at the output end of the linear interferometer on the curvature.
FIG. 6 is a graph at G1＝4,G23.5, the dependence of fringe contrast and loss on curvature at the output of the FOPA2 (signal and idler), the output of the linear interferometer, where: (a) the dotted line, the dash-dot line and the solid line respectively represent the dependence of the contrast of interference fringes of the signal light at the output end of FOPA2, the idler light at the output end of FOPA2 and the output end of the linear interferometer on the curvature, and the dotted line represents the dependence of loss on the curvature. (b) An enlarged view of a part of (a).
FIG. 7 is a graph at G1＝4,G2The dependence of the fringe contrast first derivative on curvature at the output of FOPA2 (signal and idler) and the output of the linear interferometer at 3.5, where: (a) the dashed line, the solid line and the dotted line respectively represent the dependence of the first derivative of the interference fringe contrast of the signal light at the output end of FOPA2, the output end of the linear interferometer and the idler frequency light at the output end of FOPA2 on the curvature. (b) An enlarged view of a part of (a).
Detailed Description
The invention will be further described with reference to the following specific examples and the accompanying drawings:
a particular arrangement of a bending sensor of the non-linear interferometric type according to the invention is shown in fig. 1, to which the following description is given only by way of example, without limiting the scope of the invention. In this example, the sensor includes: pumping light 1; 2, seed light; coarse wavelength division multiplexers 3, 5, 8, 10; dispersion-shifted optical fibers 4, 9; a curvature sensing element 6; a second pump light 7; photodetectors 11, 12; an oscilloscope 13. Wherein, the coarse wavelength division multiplexer 3, the dispersion displacement optical fiber 4 and the coarse wavelength division multiplexer 5 form a parametric amplifier FOPA 1; the coarse wavelength division multiplexer 8, the dispersion displacement optical fiber 9 and the coarse wavelength division multiplexer 10 form a parametric amplifier FOPA 2; the curvature sensing element consists of two optical fiber holders and a single-mode optical fiber, and the change of the curvature of the single-mode optical fiber is realized by changing the distance between the two optical fiber holders. The connection mode is as follows: the FOPA1 is injected by the pump light I1 and the seed light 2, the FOPA1 outputs idler frequency light, the signal light output by the FOPA1 and the pump light II 7 are injected into the FOPA2 after passing through the curvature sensing element 6, and the signal light and the idler frequency light at the output end of the FOPA2 are both connected with the oscilloscope 13 through the photoelectric detectors 11 and 12 to carry out light intensity maximum value and interference fringe contrast analysis.
Principle analysis:
the general structural principle of the present invention is illustrated in fig. 2. By irradiating seeds with light
Figure BDA0002502057470000031
And pump light p1Injected into FOPA1, and mixed by four waves to generate two output lights (signal lights)
Figure BDA0002502057470000032
Idler frequency light
Figure BDA0002502057470000033
) Can be described as
Figure BDA0002502057470000034
Passing FOPA1 idler light through a bend sensing element (bend loss S), then
Figure BDA0002502057470000035
Then two beams of output light (signal light) are obtained after FOPA2
Figure BDA0002502057470000036
Idler frequency light
Figure BDA0002502057470000037
) Can be described as
Figure BDA0002502057470000038
Of these, FOPA1 is non-phase sensitive, while FOPA2 is phase sensitive, so the phase factor exp (i θ) is considered here.
Calculation formula from particle number
Figure BDA0002502057470000039
To obtain
Figure BDA00025020574700000310
The intensity of the light is injected into the seed. Therefore, it is
Figure BDA00025020574700000311
Figure BDA0002502057470000041
The interference fringe contrast formula can be obtained as follows:
Figure BDA0002502057470000042
Figure BDA0002502057470000043
in order to show that the non-linear interference type bending sensor provided by the invention has higher sensitivity than a linear interference type bending sensor, the structure (shown in fig. 3) of the non-linear interference type bending sensor and the linear interference type bending sensor (BS + BS) shown in fig. 2 are compared.
The process of fig. 3 is described in detail as follows: injected light
Figure BDA0002502057470000044
Output after passing through two beam splitters and a bending degree sensing element (bending loss is S)
Figure BDA0002502057470000045
Can be described as:
Figure BDA0002502057470000046
the output light intensity can be described as:
Figure BDA0002502057470000047
wherein, IL0The intensity of the light is injected into the seed. The interference is generated at each output end as can be seen from the equation (1-8), and the contrast of the interference fringes is:
Figure BDA0002502057470000048
in order to obtain the dependency relationship of the interference fringe contrast, the maximum light intensity and the loss on the curvature representing the bending degree, initial parameters of a plurality of single-mode optical fibers are set, and the fiber core refractive index n11.461, cladding refractive index n2The core radius a is 4um at 1.456, and thus the cutoff wavelength can be obtained
Figure BDA0002502057470000049
And for the idler channel, λ 1534nm, which satisfies the single-mode transmission condition, the bend chord L is 1mm, and in the single-mode fiber, the formula of the loss caused by curvature is given by:
Figure BDA00025020574700000410
wherein the content of the first and second substances,
Figure BDA0002502057470000051
rho is curvature;
Figure BDA0002502057470000052
is a radial normalized phase constant; w is a radial normalized attenuation constant; k is a radical of1A modified Bessel function of order 1; n is the difference between the refractive indexes of the core and the cladding; v is normalized frequency;
in practice, AcAnd U can be calculated by the following approximate formula:
Figure BDA0002502057470000053
Figure BDA0002502057470000054
as shown in fig. 2(b), since the arc length of the bent portion is 2arcsin (L ρ)/ρ, the available loss S is:
Figure BDA0002502057470000055
in order to make a fair comparison of the two interferometers by taking into account that the sensitivity of the interferometer is related to the number of photons inside the interferometer, I is adjusted separately0And IL0To ensure I2'＝IL2'. Finally, under the condition of the same phase-sensitive field strength, Is1、Ii1、IL22Is plotted in fig. 4, with Is1、Ii1And IL22The first derivative of the maximum as a function of the curvature p is shown in fig. 5. It can be known that the maximum values of the light intensity of the signal light and the idler frequency light at the output end of the FOPA2 of the nonlinear interferometer are higher than the maximum value of the light intensity at the output end of the linear interferometer, the maximum value of the light intensity of the idler frequency light is amplified by 5.714-5.856 times relative to the linear interferometer, and the sensitivity is improved by 5.855-5.928 times (when the absolute value of the first derivative of the maximum value of the light intensity to the curvature is larger, the sensitivity is higher).
In addition, V isL22、Vs1、Vi1The sum loss S as a function of the curvature p is plotted in FIG. 6, and V is plottedL22、Vs1And Vi1The first derivative of (a) is plotted in fig. 7 as a function of the curvature p. From FIG. 6, it can be seen that the distance between 0 and 500m-1Within the range of (3), the contrast of interference fringes of signal light all meets the one-to-one correspondence relation with the curvature; however, the idler frequency is not satisfied, and cannot be realized at 0-107.827m-1Accurate measurement within range. From FIG. 7, the reference value is 0 to 194.232m-1The sensitivity of the signal light is higher than that of the idle frequency light at 194.232-500m-1In time, the sensitivity of the idler is higher than that of the signal light, so that the signal light and the idler need to be combined to achieve the range of 0-500m-1The curvature within the range of (1) is accurately measured. At 0-194.232m-1Measured by signal light at 194.232-500m-1Time is measured using the idler light.
Meanwhile, as can be seen from FIG. 7, the curvature is lower than 193.232m-1The sensitivity of the linear interference type bending sensor is lower than that of the signal light, and is 204.459-500m-1The temporal sensitivity is lower than the idler. Albeit at 193.232-204.459m-1Linear interferometric type curvature sensors have higher sensitivity than signal and idler light, but this is only a small fraction of the curvature range.
In summary, the nonlinear interference type bending sensor provided by the invention can realize accurate measurement of bending, and has higher sensitivity compared with a linear interference type bending sensor.
The above-mentioned examples, which have been provided to illustrate the objects, technical solutions and advantages of the present invention, should be understood that they are merely exemplary and not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (3)

1. A nonlinear interference type curvature sensor is characterized by comprising two beams of pump light, seed light, two optical fiber parametric amplifiers, a curvature sensing element, a single mode optical fiber, a photoelectric detector and an oscilloscope; the connection mode is as follows: the curvature detection method comprises the steps that a first pumping light and a seed light are injected into a first optical fiber parametric amplifier, a single-mode optical fiber of an idler frequency optical channel output by the first optical fiber parametric amplifier is bent to form a curvature sensing element, a signal light output by the first optical fiber parametric amplifier, an idler frequency light passing through the curvature sensing element and a second pumping light are injected into a second optical fiber parametric amplifier, the signal light and the idler frequency light output by the second optical fiber parametric amplifier are connected with an oscilloscope through a photoelectric detector, and curvature detection can be achieved through analysis and display of the maximum light intensity value on the oscilloscope and the change of the contrast of interference fringes.
2. The nonlinear interferometric bending sensor according to claim 1, wherein the fiber parametric amplifier is composed of two coarse wavelength division multiplexers and a dispersion shift fiber in the middle, and the pump light has a wavelength of 1550nm in an anomalous dispersion region of the dispersion shift fiber, so as to satisfy a phase matching condition of four-wave mixing.
3. A non-linear interferometric tortuosity sensor according to claim 1, characterised in that the sensor has a tortuosity detection range of 0-500m-1And the detection sensitivity is higher than that of the corresponding linear interference type bending sensor.
CN202010435426.5A 2020-05-21 2020-05-21 Non-linear interference type bending sensor Pending CN111442741A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202010435426.5A CN111442741A (en) 2020-05-21 2020-05-21 Non-linear interference type bending sensor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202010435426.5A CN111442741A (en) 2020-05-21 2020-05-21 Non-linear interference type bending sensor

Publications (1)

Publication Number Publication Date
CN111442741A true CN111442741A (en) 2020-07-24

Family

ID=71657123

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202010435426.5A Pending CN111442741A (en) 2020-05-21 2020-05-21 Non-linear interference type bending sensor

Country Status (1)

Country Link
CN (1) CN111442741A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112068045A (en) * 2020-09-02 2020-12-11 中国计量大学 Nonlinear interference type magnetic field sensor
CN112097811A (en) * 2020-09-02 2020-12-18 中国计量大学 Nonlinear interference type double-parameter sensor based on correlation injection scheme

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112068045A (en) * 2020-09-02 2020-12-11 中国计量大学 Nonlinear interference type magnetic field sensor
CN112097811A (en) * 2020-09-02 2020-12-18 中国计量大学 Nonlinear interference type double-parameter sensor based on correlation injection scheme

Similar Documents

Publication Publication Date Title
Wu et al. Few-mode optical fiber based simultaneously distributed curvature and temperature sensing
CN111442741A (en) Non-linear interference type bending sensor
CN106556574B (en) Online two-beam interference type optic fibre refractive index sensor and refractivity tester
CN113108710B (en) Optical low-frequency strain detection system and detection method based on ellipse fitting
Zhang et al. Simultaneous measurement of refractive index and temperature by Mach–Zehnder cascaded with FBG sensor based on multi-core microfiber
Zhao et al. Beating the shot-noise limit with optical fiber quantum sensors for salinity measurement
Kawa et al. Single-end-access strain and temperature sensing based on multimodal interference in polymer optical fibers
Eftimov et al. Sensing with a LP/sub 01/-LP/sub 02/intermodal interferometer
Tong et al. Fiber-optic temperature sensor based on beat frequency and neural network algorithm
CN111537445A (en) Ring resonant cavity enhanced liquid component and concentration sensor based on evanescent wave
Chen et al. Curvature sensor based on SMF taper in fiber loop ring down system
Liu et al. Ultra-low noise phase measurement of fiber optic sensors via weak value amplification
CN113804412B (en) Micro-chromatic dispersion measuring device of optical fiber device based on annular light path structure
Du et al. Single-ended self-calibration high-accuracy Raman distributed temperature sensing based on multi-core fiber
Wang et al. Single-few-single mode fiber structure for simultaneous measurement for curvature and temperature assisted by intensity-correlated pulse twin beams
Zhao et al. Refractive index sensor based on a gradually hot-pressed flatted plastic optical fiber
Li et al. Optimized neural network for temperature extraction from Brillouin scattering spectra
Obaton et al. Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing
CN206709787U (en) A kind of double chirp gratings strain demodulating system based on piezoelectric ceramics
CN212512920U (en) Non-linear interference type bending sensor
CN110319940B (en) Laser fiber interferometer diagnostic system for high density plasma density measurement
Liu et al. Investigations on seven-core fiber based interferometric all-fiber sensor for curvature and temperature measurements
Li et al. Phase compensation sensitized wave front splitting fiber Mach-Zehnder interferometer
CN113091783B (en) High-sensitivity sensing device and method based on two-stage Brillouin scattering
Song et al. Mid-infrared refractive index sensor with high sensitivity and wide detection range based on multimode interference in tellurite optical fibers

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination