CN108168728B - device and method for simultaneously measuring temperature strain of unbalanced polarization maintaining optical fiber double interferometers - Google Patents
device and method for simultaneously measuring temperature strain of unbalanced polarization maintaining optical fiber double interferometers Download PDFInfo
- Publication number
- CN108168728B CN108168728B CN201711310550.3A CN201711310550A CN108168728B CN 108168728 B CN108168728 B CN 108168728B CN 201711310550 A CN201711310550 A CN 201711310550A CN 108168728 B CN108168728 B CN 108168728B
- Authority
- CN
- China
- Prior art keywords
- polarization
- maintaining
- optical fiber
- interferometer
- 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.)
- Active
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
-
- 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
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/168—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of polarisation
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention provides a device and a method for simultaneously measuring temperature strain of a double interferometer of an unbalanced polarization maintaining optical fiber. The polarization maintaining fiber coupler, the phase modulator, the polarization maintaining fiber and the polarization maintaining fiber reflector constitute one unbalanced polarization maintaining fiber interferometer, and the light source injects light via the polarizer into the fast and slow axes of the polarization maintaining fiber for transmission to realize coaxial transmission signal interference in the interferometer. Because the parameters of the fast axis and the slow axis of the polarization maintaining optical fiber are different, the fast axis signal and the slow axis signal have different responses to the same temperature and strain, an orthogonal response matrix is constructed by adopting a non-equilibrium interferometer structure, and the temperature response coefficient and the strain response coefficient of two paths of interference signals are measured, so that the temperature and the strain can be measured simultaneously. The scheme solves the problem of cross sensitivity, and the measurement result is accurate and stable and has high sensitivity.
Description
Technical Field
The invention relates to an optical fiber sensing technology, in particular to a device and a method for simultaneously measuring temperature strain of an unbalanced polarization-maintaining optical fiber double interferometer.
Background
with the rapid development of human society, various large-scale foundation engineering facilities are continuously constructed, strain detection is an indispensable means in the structural safety guarantee of large-scale modern engineering structures, such as dams, skyscrapers, bridges and the like, and strain detection is required in the production construction and maintenance processes of many engineering structures to guarantee the construction and operation quality. In addition, strain detection has very important application in earthquake and crustal strain monitoring, oil well exploration, marine environment detection and other human activities, so various strain detection sensors are developed endlessly.
compared with the traditional strain detector adopting an electromechanical detection principle, the optical fiber strain detector is favored due to the characteristics of small volume, light weight, electromagnetic interference resistance, corrosion resistance, electric insulation, capability of working in a severe environment and the like, and particularly, the optical fiber strain detector based on the interferometer principle has the advantages of simple structure, high sensitivity (displacement resolution of picometers and sub-picometers), large dynamic range (160-180 dB), wide measurement frequency band (DC-MHz) and the like, so that the optical fiber strain detector is widely applied. However, due to the characteristics of the optical fiber, the strain detector used for strain measurement is sensitive to both temperature and strain, and is linearly related to the temperature and the strain, so that the problem of cross sensitivity between temperature and strain exists in practical application of such a sensor, that is, it is difficult to separate the variation caused by each of temperature and strain from the finally obtained to-be-measured value, which seriously hinders the engineering popularization of the optical fiber strain sensor. The following technologies are generally adopted to solve the problem of temperature strain cross sensitivity at present:
1. the method adopts a method of setting a reference optical fiber measuring system, namely, a set of identical reference optical fiber sensors are arranged beside a measuring optical fiber sensor and are in a relaxed state without strain to acquire temperature information, and then the temperature information is deducted from the measuring information of the measuring optical fiber sensor to acquire strain information. For example, li-eston et al, the university of southeast 2009, proposed a fiber grating strain temperature simultaneous measurement sensor (CN200920040685.7), which uses two identical fiber gratings to make one of them measure temperature without stress and the other is sensitive to both temperature and strain. However, two sets of identical optical fiber sensing systems need to be arranged in parallel at the same time, but it is difficult to ensure that the reference optical fiber sensing system and the measurement optical fiber sensing system are completely consistent in the actual manufacturing process, which limits the application of the method.
2. An integrated optical fiber strain and temperature sensor is adopted, namely two sensors are integrated in a set of optical fiber sensing system to respectively realize the measurement of a single one of temperature and strain to be measured and the simultaneous measurement of two ones of the temperature and the strain to be measured, generally one sensor is used for measuring the temperature, and the other sensor is used for measuring the temperature and the strain simultaneously, for example, the Rongyunjiang of the institute of photoelectric engineering of Chongqing university in 2000 proposes an integrated optical fiber strain and temperature sensor device (CN00244460.7), and the device integrates a broadband optical fiber temperature sensor in an optical fiber FP strain sensor to realize the function of simultaneously measuring the temperature and the strain. However, the general structure of the integrated optical fiber strain and temperature sensor is complex, and it is difficult to ensure the measurement accuracy and measurement range of the two integrated optical fiber sensors to be consistent, so that the method is not widely applied.
3. The method includes the steps that strain and temperature simultaneous measurement sensing is achieved through the fiber bragg grating, namely a special sensor is constructed through the characteristics of the fiber bragg grating, for example, Sundarrajan Asokan and the like in India of 2012 propose a method (US 20120120176597) for distinguishing and measuring strain and temperature through a fiber bragg grating cross line sensor, a 2-order coefficient matrix is constructed through two fiber bragg gratings with different parameters and sensitive to temperature and strain in the fiber bragg grating cross line sensor, and the function of simultaneous measurement of temperature and strain is achieved through solving the coefficient matrix. The fiber grating sensor is generally small in size and simple in structure, so that the fiber grating sensor is widely applied, but because the constructed coefficient matrix is a non-orthogonal matrix, the solution obtained by the matrix can be greatly changed along with the weak change of matrix parameters, and the stability of a measurement result is reduced.
4. The most common optical fiber sensor utilizing the Brillouin effect, such as the Mengzhou of the national defense science and technology university of the national liberation of the people in 2013, provides a distributed optical fiber sensor method and device (CN201310140194.0) for simultaneously measuring temperature and strain, and the scheme realizes the function of simultaneously measuring temperature and strain by injecting incident light with two different wavelengths into the same common single-mode sensing optical fiber in sequence and separately measuring the Brillouin frequency shift quantity of the single-mode sensing optical fiber. However, such sensors have multiple applications and distributed sensing and have the disadvantages of complex structure, multiple supporting devices and the like.
5. For example, a sensor (CN201520488312.1) based on simultaneous measurement of temperature and strain of spherical and fine-core optical fibers is proposed by the benzyl cheng of the national institute of metrology in 2015, and uses a special optical fiber to enable a cladding mode and a core mode to form a mach zehnder interferometer to realize the function of simultaneous measurement of temperature and strain. However, the cost of such sensors is high due to the use of special optical fibers, and the sensors are limited by the optical fiber drawing technology, and the performance of the sensors is inconsistent due to the unstable quality of part of special optical fibers.
in addition, there are numerous other types of fiber optic sensors that can achieve simultaneous strain and temperature measurements, such as Mark e.froggatt, 2008, usa, which proposes a method of distributed strain and temperature simultaneous measurement in polarization maintaining fiber (US20080002187) to achieve simultaneous temperature and strain measurement.
however, for the most widely used fiber optic interferometer sensor, the reference fiber optic measurement system method is mainly set up and the integrated fiber optic strain and temperature sensor is adopted to solve the problem of temperature and strain cross sensitivity of the fiber optic interferometer sensor, but the disadvantages of the two methods are obvious. There is therefore no simple, effective and universally applicable solution to the problem of temperature and strain cross-sensitivity of fiber optic interferometer sensors in the prior art disclosures.
Disclosure of Invention
The invention aims to provide a non-equilibrium polarization maintaining optical fiber double-interferometer temperature and strain simultaneous measurement device which can solve the problem of cross sensitivity of temperature and strain and realize simultaneous measurement of temperature and strain parameters. The invention also aims to provide a method for simultaneously measuring the temperature strain of the unbalanced polarization-maintaining optical fiber and the double interferometers based on the device for simultaneously measuring the temperature strain of the unbalanced polarization-maintaining optical fiber and the double interferometers.
The purpose of the invention is realized as follows:
The invention relates to a device for simultaneously measuring temperature strain of a non-equilibrium polarization-maintaining optical fiber double interferometer, which comprises a narrow-linewidth laser light source 101, a polarizer 111, a non-equilibrium polarization-maintaining optical fiber double interferometer 130, a polarization beam splitting differential detection device 140 and a signal acquisition, demodulation and recording device 150,
The narrow-bandwidth laser light source 101 is connected with the input end a of the polarization-maintaining circulator 141 through the polarizer 111, and the counter-axis angle 121 of the polarization-maintaining optical fiber at the connection position is 0-45 degrees; the unbalanced polarization maintaining fiber interferometer 130 is connected with the signal acquisition, demodulation and recording device 150 through the polarization beam splitting differential detection device 140;
The unbalanced polarization maintaining fiber dual interferometer 130 consists of a 2 × 2 polarization maintaining fiber coupler 131, a phase modulator 134, the 1 st and 2 nd polarization maintaining fibers 132 and 135 and the 1 st and 2 nd polarization maintaining fiber mirrors 133 and 136; the first output end c3 of the polarization-maintaining fiber coupler 131 is connected to the 1 st polarization-maintaining fiber mirror 133 through the 1 st polarization-maintaining fiber 132 to form a fixed-length sensing arm l of the first interferometer1(ii) a The second output end c4 of the polarization maintaining fiber coupler 131 is connected to the 2 nd polarization maintaining fiber 135 and the 2 nd polarization maintaining fiber reflector 136 in turn through the phase modulator 134 to form a fixed-length sensing arm l of the second interferometer2The arm length difference Δ l ═ l of the unbalanced polarization maintaining fiber interferometer 1301-l2The | is more than 0.1m, and the counter-axis angles of all the polarization maintaining optical fiber joints are 0-0 degree;
the polarization beam splitting differential detection device 140 is composed of a polarization maintaining circulator 141, a 1 st and a 2 nd polarization beam splitters 142 and 145, and 1 st and a 2 nd differential detectors 143 and 146, 144 and 147; the first input end c1 of the polarization-maintaining fiber coupler 131 is connected with the 1 st polarization beam splitter 142 through a polarization-maintaining circulator 141, the second input end c2 of the polarization-maintaining fiber coupler 131 is connected with the 2 nd polarization beam splitter 145, and the counter-axis angles of all the polarization-maintaining fiber joints are 0-0 degree; the 1 st differential detectors 143 and 146 are connected to the 1 st and 2 nd polarization beam splitters 142 and 145 fast axis signal output terminals, and the 2 nd differential detectors 144 and 147 are connected to the 1 st and 2 nd polarization beam splitters 142 and 145 slow axis signal output terminals.
The device for simultaneously measuring the temperature strain of the unbalanced polarization maintaining optical fiber and the double interferometers can also comprise:
1. the polarization maintaining fiber coupler 131 is a 2 × 2 polarization maintaining fiber coupler, the optimal splitting ratio is 50:50, the fast axis and the slow axis work simultaneously, the wavelength working range can cover the emission spectrum of the narrow-linewidth laser light source 101, and the pigtails are all polarization maintaining fibers.
2. The fast and slow axes of the 1 st and 2 nd polarization maintaining fiber reflectors 133 and 136 work simultaneously, the polarization state of reflected light is the same as that of incident light, the wavelength working range can cover the emission spectrum of the narrow-linewidth laser light source 101, and the pigtails are all polarization maintaining fibers.
3. the wavelength working ranges of the polarizer 111, the polarization-maintaining circulator 141, the 1 st and 2 nd polarization-maintaining optical fibers 132 and 135, the 1 st and 2 nd polarization-maintaining beam splitters 142 and 145 and the 1 st, 2 nd, 3 rd and 4 th photodetectors 143, 144, 146 and 147 can cover the emission spectrum of the narrow-linewidth laser light source 101; the output terminal l1 of the polarizer 111, the input terminals p1, p4 of the 1 st and 2 nd polarization-maintaining beam splitters 142, 145, the phase modulator 134, the polarization-maintaining circulator 131, and the pigtails of the 1 st and 2 nd polarization-maintaining fiber mirrors 133, 136 are all polarization-maintaining fibers.
The measuring method of the device for simultaneously measuring the temperature strain of the unbalanced polarization maintaining optical fiber double interferometers based on the invention comprises the following steps:
1) in a laboratory, a sensing arm of the measuring device is in a constant temperature environment, a displacement table is used for applying tensile stress, displacement data and phase change data are recorded, and the strain coefficients of a slow axis interferometer, namely an x-axis interferometer and a fast axis interferometer, namely a y-axis interferometer are calculatedand used as known constants for later calculation;
2) In a laboratory, a sensing arm of the measuring device is in a relaxed state, the ambient temperature is changed, phase change data is recorded, and the strain coefficients of a slow-axis interferometer, namely an x-axis interferometer and a fast-axis interferometer, namely a y-axis interferometer are calculatedAnd used as known constants for later calculation;
3) The measuring device is placed in a test environment, a sensing arm optical fiber of an interferometer is fixedly attached to the surface of an object to be measured, the strain epsilon and the environment temperature change delta T of the object to be measured are transmitted to the sensing optical fiber through contact or media, finally, the phase position demodulated by an interference signal is changed, and the phase position is recordedrecording the phase data of the fast and slow axis interferometer to obtain delta phix、Δφy；
4) constant measured in laboratoryandand delta phi obtained in the test environmentx、Δφy(ii) a Carry-in typeand calculating to obtain the strain parameter and the temperature change of the environment to be measured.
The invention provides a method and a device for simultaneously measuring temperature and strain of an unbalanced polarization maintaining optical fiber double interferometer.
The device for simultaneously measuring the temperature strain of the unbalanced polarization maintaining fiber double interferometers has the main ending characteristics that:
the main components comprise: the device comprises a narrow-linewidth laser light source 101, a polarizer 111, an unbalanced polarization-maintaining optical fiber dual interferometer 130, a polarization beam splitting differential detection device 140 and a signal acquisition, demodulation and recording device 150, as shown in fig. 1.
(1) The narrow-bandwidth laser light source 101 is connected with the input end a of the polarization-maintaining circulator 141 through the polarizer 111, and the counter-axis angle 121 of the polarization-maintaining optical fiber at the connection position is 0-45 degrees; the unbalanced polarization maintaining fiber interferometer 130 is connected with the signal acquisition, demodulation and recording device 150 through the polarization beam splitting differential detection device 140; the output light of the narrow linewidth laser light source 101 is changed into linear polarization light after passing through the polarizer 111, and is injected into the polarization maintaining fiber slow axis at the input end a of the polarization maintaining circulator 141 at an angle of 45 degrees at the joint 121, so that the fast axis and the slow axis of the polarization maintaining fiber are simultaneously injected with light with the same energy for transmission, and then enter the unbalanced polarization maintaining fiber interferometer 130, as shown in fig. 2;
(2) The unbalanced polarization-maintaining fiber interferometer 130 comprises a 2 × 2 polarization-maintaining fiber coupler 131, a phase modulator 134, a second polarization-maintaining fiber1 polarization maintaining fiber 132, 2 polarization maintaining fiber 135, 1 polarization maintaining fiber reflector 133 and 2 polarization maintaining fiber reflector 136; the first output end c3 of the polarization-maintaining fiber coupler 131 is connected to the 1 st polarization-maintaining fiber mirror 133 through the 1 st polarization-maintaining fiber 132 to form a fixed-length sensing arm l of the interferometer1(ii) a The second output end c4 of the polarization maintaining fiber coupler 131, through the phase modulator 134, sequentially forms the interferometer fixed-length sensing arm l with the 2 nd polarization maintaining fiber 135 and the 2 nd polarization maintaining fiber reflector 1362the arm length difference Deltal ═ l of the unbalanced polarization maintaining fiber interferometer (130)1-l2The | is more than 0.1m, and the counter-axis angles of all the polarization maintaining optical fiber joints are 0-0 degree; the polarization maintaining optical fiber and the polarization maintaining device in the unbalanced polarization maintaining optical fiber interferometer 130 are connected with a fast axis and a slow axis respectively, when light is injected into the fast axis and the slow axis simultaneously for transmission, the light is transmitted through an interference light path of the unbalanced polarization maintaining optical fiber interferometer 130, and finally the fast axis light and the fast axis light are interfered, the slow axis light and the slow axis light are interfered, and the two paths of interference are not interfered with each other respectively, so that the two paths of interferometers of the fast axis light path and the slow axis light path are simultaneously arranged in the unbalanced polarization maintaining optical fiber interferometer 130;
(3) The polarization beam splitting differential detection device 140 is composed of a polarization maintaining circulator 141, a 1 st and a 2 nd polarization beam splitters 142 and 145, and 1 st and a 2 nd differential detectors 143 and 146, 144 and 147; the first input end c1 of the polarization-maintaining fiber coupler 131 is connected with the 1 st polarization beam splitter 142 through a polarization-maintaining circulator 141, the second input end c2 of the polarization-maintaining fiber coupler 131 is connected with the 2 nd polarization beam splitter 145, and the counter-axis angles of all the polarization-maintaining fiber joints are 0-0 degree; the 1 st differential detector is connected with the fast-axis signal output ends of the 1 st and 2 nd polarization beam splitters 142 and 145, and the 2 nd differential detector is connected with the slow-axis signal output ends of the 1 st and 2 nd polarization beam splitters 142 and 145; interference signals transmitted on the fast axis and the slow axis are output by a first input end c1 and a second input end c2 of the polarization-maintaining fiber coupler 131, wherein the fast axis interference signal and the slow axis interference signal of the first input end c1 are transmitted to the 1 st polarization beam splitter 142 through the polarization-maintaining circulator 141 and are separated, the fast axis interference signal and the slow axis interference signal of the second input end c2 are transmitted to the 2 nd polarization beam splitter 145 and are separated, the two fast axis signals are detected by a 1 st differential detector, the two slow axis signals are detected by a 2 nd differential detector, the differential detection realizes common-mode rejection and differential-mode-Zehnder effects, and the photoelectric detector transmits the detected signals to the signal acquisition, demodulation and recording device 150;
(4) the signal acquisition, demodulation and recording device 150 comprises a data acquisition card 151 and signal demodulation and recording software 152, wherein the data acquisition card 151 is directly connected with the signal demodulation and recording software 152; in addition, the 1 st and 2 nd differential detectors 143 and 146, 144 and 147 and the phase modulator 134 are connected to the data acquisition card 151; the signals detected by the differential detector are collected by the data acquisition card 151, the signal demodulation and recording software 152 is finally transmitted, the signal demodulation and recording software 152 demodulates, displays, records and stores the signals, and the like, and meanwhile, the signal demodulation and recording software 152 controls the data acquisition card 151 to load the modulation signals to the phase modulator 134.
The polarization maintaining fiber coupler 131 is: the optimal splitting ratio of the 2 multiplied by 2 polarization-maintaining optical fiber coupler is 50:50, the fast axis and the slow axis work simultaneously, the wavelength working range can cover the emission spectrum of the narrow-linewidth laser light source 101, and the tail fibers are all polarization-maintaining optical fibers;
The 1 st and 2 nd polarization maintaining fiber reflectors 133 and 136 work at the same time, the polarization state of reflected light is the same as that of incident light, the wavelength working range can cover the emission spectrum of the narrow-linewidth laser light source 101, and the pigtails are all polarization maintaining fibers;
The polarizer 111, the polarization-maintaining circulator 141, the 1 st and 2 nd polarization-maintaining fibers 132 and 135, the 1 st and 2 nd polarization beam splitters 142 and 145, the 1 st, 2 nd, 3 rd and 4 th photodetectors 143, 144, 146 and 147, and the wavelength working range can cover the emission spectrum of the narrow-linewidth laser light source 101; the output terminal l1 of the polarizer 111, the input terminals p1, p4 of the 1 st and 2 nd polarization-maintaining beam splitters 142, 145, the phase modulator 134, the polarization-maintaining circulator 131, the 1 st and 2 nd polarization-maintaining fiber mirrors 133, 136, and the tail fibers thereof are all polarization-maintaining fibers.
The invention relates to a technical improvement of a strain measuring instrument based on an optical fiber interferometer, which mainly solves the problem of cross sensitivity of temperature and strain of the strain measuring instrument of the common single-mode optical fiber interferometer and realizes the simultaneous measurement of temperature and strain parameters. The technical scheme adopted for realizing the above purpose of the invention is to replace a single mode fiber by a polarization maintaining fiber with two transmission axes of a fast axis and a slow axis and build a full polarization maintaining fiber interference light path by adopting a polarization maintaining fiber device, as shown in figure 1. In the polarization maintaining optical fiber, light can be transmitted independently along a fast axis and a slow axis, so that two interference light paths can be realized in the same optical fiber interference system by using the fast axis and the slow axis of the polarization maintaining optical fiber, the phase outputs of the fast axis interference light path and the slow axis interference light path respectively have temperature coefficients and strain coefficients due to the fact that parameters such as refractive indexes of the fast axis and the slow axis of the polarization maintaining optical fiber are inconsistent, an orthogonal coefficient matrix is constructed between an output phase and temperature and strain to be measured by measuring the temperature coefficients and the strain coefficients of the two interference light paths, and due to the orthogonal property of the coefficient matrix, when matrix parameters change, the solution obtained by the matrix is relatively stable, and the accuracy and the stability of matrix solution are realized. Therefore, the orthogonal coefficient matrix is used for solving, the simultaneous measurement of the temperature and the strain can be realized, the measurement result is stable, the problem of cross sensitivity of the temperature and the strain in the optical fiber interferometer is solved, the measurement result is accurate and stable, the sensitivity is high, and the method is suitable for engineering application.
In order to realize simultaneous transmission of light on two transmission axes, namely a fast axis and a slow axis, of polarization-maintaining optical fiber, a polarizer with tail fiber as the polarization-maintaining optical fiber is connected with a light source, the polarizer is connected with the polarization-maintaining optical fiber, and the axial angle of a connecting point is 0-45 degrees. As shown in figure 2, light output by a light source is changed into linearly polarized light after passing through a polarizer, polarization state is kept through a tail fiber of the polarizer, and then transmitted light is divided into two parts with equal energy through a connecting point with an axial angle of 0-45 degrees and is respectively injected into a polarization-maintaining optical fiber fast-slow axis at the input end of a polarization-maintaining coupler for transmission. In fiber optic interferometers, the relationship between temperature and strain and the output phase of the interferometer is range-linearly dependent, and the change in the demodulated output phase, Δ φ, for slow-axis (x-axis) interferometers and fast-axis interferometersx、ΔφyThe relationship between strain ε and temperature change Δ T can be expressed as:
Using equations (1) to (2), a linear system of equations represented by a matrix is obtained:
In the formula (1) and the formula (2),andThe strain coefficient and the temperature coefficient of the polarization maintaining fiber slow axis (x axis) interferometer and the fast axis (y axis) interferometer are constants related to the parameters of the fiber, and the values can be obtained through experimental measurement or can be estimated through theoretical calculation to obtain approximate values. The length l of sensing optical fiber in interferometer is combined by using the parameters of elastic-optical coefficient, thermo-optical coefficient, thermal expansion coefficient, polarization maintaining optical fiber birefringence and the like of common single mode optical fiber1≈l2> Δ l and it was found by theoretical derivation when the arm length difference Δ l ═ l1-l2when | is greater than 0.1m, the coefficient matrix in the formula (3) may be changed into an orthogonal coefficient matrix, and the solution of the linear equation with the orthogonal coefficient matrix is more stable than that of the non-orthogonal coefficient matrix, that is, when a parameter in the orthogonal coefficient matrix is slightly changed, the solution of the linear equation is less affected, as shown in fig. 3. Therefore, in practical application, the unbalanced interferometer with the arm length difference larger than 0.1m is constructed, and the measurement result is more accurate and stable. Further simplifying the formula (3) to obtain:
in actual test, the phase information finally demodulated by the interferometer is combined with the four parameters of the coefficient matrix obtained by previous experiment and calculation, and the temperature and the strain parameter to be measured can be obtained by operation according to the formula (4).
compared with the prior art, the invention has the advantages that:
(1) the system adopts the design of a full polarization maintaining optical fiber interferometer, realizes the interference of fast axis light and the interference of slow axis light and slow axis light in the same optical fiber interference system, realizes the simultaneous measurement of temperature and strain by utilizing different temperature coefficients and strain coefficients of two interference light paths, and solves the problem of cross sensitivity of temperature and strain.
(2) the system adopts the design of the unbalanced interferometer, so that the length difference of two arms of the interferometer is larger than 0.1m, and an orthogonal coefficient matrix is constructed by utilizing the temperature coefficient and the strain coefficient of the fast-slow axis interferometer, so that the coefficient matrix can solve a stable solution, and the accuracy and the stability of the measurement result of the device are ensured.
(3) The system adopts a Michelson type interferometer structure, and the optical signal returns twice in the sensing optical fiber, so that the optical signal responds 2 times to the external to-be-measured value, and the sensitivity of the system is greatly improved. In addition, due to the design of the all-fiber optical path, the device is small in size, easy to build and suitable for instrumentation.
(4) the system adopts the design of a full polarization maintaining optical fiber light path, and the polarization maintaining optical fiber has the function of maintaining the polarization state of transmission light, so that the problem of polarization fading caused by random change of the polarization state in a common single-mode optical fiber interferometer is avoided, the stability of interference signals is improved, and the stability of the performance of a system device is further improved.
the invention provides a method and a device for simultaneously measuring temperature strain of an unbalanced polarization maintaining optical fiber double interferometer based on the improvement of the prior art, and the design concept is as follows: utilize the characteristic that can be along fast axle and the mutual independent transmission of slow axle simultaneously in the polarization maintaining optical fiber, use polarization maintaining optical fiber and polarization maintaining device to build a full polarization maintaining optical fiber interference, adopt the polarizer to become light source output light after the line polarisation, become 45 jiaos with polarization maintaining optical fiber transmission axle and inject polarization maintaining optical fiber interferometer, this makes polarization maintaining optical fiber interferometer's fast axle and slow axle all have optical transmission and transmit light energy size equal, realize fast axle light and fast axle light interference finally in the interferometer, slow axle light and slow axle light interference, consequently can adopt polarization maintaining optical fiber's fast and slow axle to realize two interference light paths in same optical fiber interference system. The method comprises the steps that the phase outputs of a fast axis interference light path and a slow axis interference light path respectively have a temperature coefficient and a strain coefficient due to the fact that the refractive index of a fast axis and the refractive index of a slow axis of a polarization-maintaining optical fiber are not consistent, an unbalanced interferometer is constructed by changing the arm length difference of the polarization-maintaining optical fiber interferometer, when the arm length difference is larger than 0.1m, an orthogonal coefficient matrix can be constructed between the output phase and the temperature and strain to be measured, due to the orthogonal property of the coefficient matrix, when the matrix parameters change, the solution obtained by the matrix is relatively stable, and accuracy and stability of matrix solving are achieved. Therefore, the orthogonal coefficient matrix is used for solving, the simultaneous measurement of the temperature and the strain can be realized, the measurement result is stable, and the problem of cross sensitivity of the temperature and the strain in the optical fiber interferometer is solved.
Drawings
FIG. 1 is a schematic diagram of a device for simultaneously measuring temperature and strain of an unbalanced polarization maintaining fiber dual interferometer;
FIG. 2a is a schematic diagram showing the alignment of the polarizer output polarization maintaining fiber and the polarization maintaining coupler input polarization maintaining fiber at a connection point of 0-45 °; FIG. 2b is a schematic diagram of the polarization state of the transmitted light at the output terminal l1 of the polarizer; FIG. 2c is a schematic view of the light split at the connection point 121; FIG. 2d is a schematic diagram of the polarization state of the transmitted light at the input end a of the polarization-maintaining circulator;
FIG. 3a is a schematic diagram of a case where the coefficient matrices are not orthogonal; fig. 3b is a schematic diagram of the case where the coefficient matrices are orthogonal.
Detailed Description
The invention is described in more detail below by way of example.
proper connection of the devices is required before testing for temperature and strain. As shown in fig. 1 and fig. 2, the components are connected in the connection manner described in the disclosure, and all the optical path connections are soldered to stabilize the optical path.
the connection mode is as follows:
(1) The narrow-bandwidth laser light source 101 is connected with the input end a of the polarization-maintaining circulator 141 through the polarizer 111, and the counter-axis angle 121 of the polarization-maintaining optical fiber at the connection position is 0-45 degrees; the unbalanced polarization maintaining fiber interferometer 130 is connected with the signal acquisition, demodulation and recording device 150 through the polarization beam splitting differential detection device 140;
(2) the unbalanced polarization maintaining fiber interferometer 130 is composed of a 2 × 2 polarization maintaining fiber coupler 131, a phase modulator 134, a 1 st polarization maintaining fiber 132, a 2 nd polarization maintaining fiber 135, a 1 st polarization maintaining fiber reflector 133 and a 2 nd polarization maintaining fiber reflector 136; the first output end c3 of the polarization-maintaining fiber coupler 131 is connected to the 1 st polarization-maintaining fiber mirror 133 through the 1 st polarization-maintaining fiber 132 to form a fixed-length sensing arm l of the interferometer1(ii) a The second output end c4 of the polarization maintaining fiber coupler 131, through the phase modulator 134, sequentially forms the interferometer fixed-length sensing arm l with the 2 nd polarization maintaining fiber 135 and the 2 nd polarization maintaining fiber reflector 1362The arm length difference Deltal ═ l of the unbalanced polarization maintaining fiber interferometer (130)1-l2the | is more than 0.1m, and the counter-axis angles of all the polarization maintaining optical fiber joints are 0-0 degree;
(3) the polarization beam splitting differential detection device 140 is composed of a polarization maintaining circulator 141, a 1 st and a 2 nd polarization beam splitters 142 and 145, and 1 st and a 2 nd differential detectors 143 and 146, 144 and 147; the first input end c1 of the polarization-maintaining fiber coupler 131 is connected with the 1 st polarization beam splitter 142 through a polarization-maintaining circulator 141, the second input end c2 of the polarization-maintaining fiber coupler 131 is connected with the 2 nd polarization beam splitter 145, and the counter-axis angles of all the polarization-maintaining fiber joints are 0-0 degree; the 1 st differential detector is connected with the fast-axis signal output ends of the 1 st and 2 nd polarization beam splitters 142 and 145, and the 2 nd differential detector is connected with the slow-axis signal output ends of the 1 st and 2 nd polarization beam splitters 142 and 145;
(4) The signal acquisition, demodulation and recording device 150 comprises a data acquisition card 151 and signal demodulation and recording software 152, wherein the data acquisition card 151 is directly connected with the signal demodulation and recording software 152; in addition, the 1 st and 2 nd differential detectors 143 and 146, 144 and 147 and the phase modulator 134 are connected to the data acquisition card 151;
The detailed performance parameters of the optical fiber device selected by the device are as follows.
(1) The working wavelength of the narrow-line-width laser light source is 1550 +/-20 nm, the central wavelength is 1550nm, the fiber output power is more than 2mW, and the spectral line width is less than 1 pm;
(2) The polarization maintaining optical fiber polarizer is a three-port circulator, the working wavelength is 1550nm, the insertion loss is 1dB, the return loss is more than 55dB, and the tail fiber is a panda type polarization maintaining optical fiber;
(2) The working wavelength of the polarization-maintaining circulator is 1550nm, the extinction ratio is 30dB, the insertion loss is less than 1dB, the input end is a single-mode optical fiber, and the output end is a panda-type polarization-maintaining optical fiber;
(3) The working wavelength of the 2 x 2 polarization-maintaining optical fiber coupler is 1550nm, the light splitting ratio is 50:50, the fast axis and the slow axis work simultaneously, and the tail fiber is a panda-type polarization-maintaining optical fiber;
(4) the phase modulator is a piezoelectric ceramic ring, the diameter of the phase modulator is 30mm, the length of the wound optical fiber is 1000mm, the wound optical fiber is a panda type polarization maintaining optical fiber, and the modulation amplitude is larger than 2 pi;
(5) The 1 st and 2 nd polarization maintaining fibers are panda type polarization maintaining fibers, the extinction ratio is better than 20dB, and the lengths are 97000mm and 98000mm respectively;
(6) The working wavelength of the 1 st and 2 nd polarization-maintaining optical fiber reflectors is 1550 +/-5 nm, the fast and slow axes work simultaneously, the polarization state of reflected light and incident light is the same, the insertion loss is 0.6dB, and the tail fiber is a polarization-maintaining optical fiber and has the length of 1000 mm;
(7) the 1 st and 2 nd polarization beam splitters are 1 multiplied by 2 polarization beam splitters, the working wavelength is 1550nm, the extinction ratio is greater than 20dB, the insertion loss is less than 0.5dB, and the tail fiber of the input end is a polarization-maintaining fiber;
(8) The photosensitive materials of the 1 st, 2 nd, 3 rd and 4 th photodetectors are all InGaAs, the light detection range is 1100-1700 nm, the responsivity is more than 0.9A/W, for example, Nirvana of New Focus company is adoptedTMSeries 2017 type balance detector.
The working process of the measuring device is as follows:
firstly, measuring the respective temperature coefficient and strain coefficient of the fast-axis interferometer and the slow-axis interferometer in a laboratory and calculating four parameters of an orthogonal coefficient matrix in a formula (3)Andand used as a known constant for later calculation;
Secondly, the device is placed in a test environment, and sensing optical fibers of the interferometer, namely two arms of the interferometer, are fixedly attached to the surface of an object to be tested. When an object to be detected is strained or the temperature is changed, the strain and the environmental temperature change of the object to be detected act on the sensing optical fiber of the interferometer through contact or medium transmission, so that the length and the refractive index of the sensing optical fiber are changed, the optical path of light transmitted in the sensing optical fiber is further influenced, and finally the phase demodulated by the interference signal is changed. The interference light signal is detected by the photoelectric detector and converted into an electric signal after being output from the interferometer, the converted electric signal is amplified by the circuit and collected by the data acquisition card, and finally transmitted to the signal demodulation system and demodulated to obtain the phase change, and then the phase information is recorded and stored.
Finally, combining four parameters of an orthogonal coefficient matrix which are obtained by measurement before and are used as known quantitiesAnd measuring in a test environment to obtain the phase changes of the fast axis interferometer and the slow axis interferometer, and calculating according to the formula (4) to obtain the values of the strain and the temperature change of the physical parameter to be measured, so as to finally realize the simultaneous measurement of the strain and the temperature.
Claims (1)
1. a measuring method based on an unbalanced polarization-maintaining optical fiber double-interferometer temperature strain simultaneous measuring device comprises a narrow-linewidth laser light source (101), a polarizer (111), an unbalanced polarization-maintaining optical fiber double-interferometer (130), a polarization beam splitting differential detection device (140) and a signal acquisition, demodulation and recording device (150),
The narrow-bandwidth laser light source (101) is connected with the input end (a) of the polarization-maintaining circulator (141) through the polarizer (111), and the counter-axis angle (121) of the polarization-maintaining optical fiber at the joint is 0-45 degrees; the unbalanced polarization maintaining fiber interferometer (130) is connected with the signal acquisition, demodulation and recording device (150) through the polarization beam splitting differential detection device (140);
The unbalanced polarization-maintaining fiber dual interferometer (130) consists of a 2 multiplied by 2 polarization-maintaining fiber coupler (131), a phase modulator (134), a 1 st polarization-maintaining fiber (132), a 2 nd polarization-maintaining fiber (135) and a 1 st polarization-maintaining fiber reflector (133), a 2 nd polarization-maintaining fiber reflector (136); the first output end (c3) of the polarization-maintaining fiber coupler (131) is connected with the 1 st polarization-maintaining fiber reflector (133) through the 1 st polarization-maintaining fiber (132) to form a first interferometer fixed-length sensing arm (l)1) (ii) a A second output end (c4) of the polarization-maintaining optical fiber coupler (131) is sequentially connected with a 2 nd polarization-maintaining optical fiber (135) and a 2 nd polarization-maintaining optical fiber reflector (136) through a phase modulator (134) to form a second interferometer fixed-length sensing arm (l)2) The arm length difference Deltal ═ l of the unbalanced polarization maintaining fiber interferometer (130)1-l2The | is more than 0.1m, and the counter-axis angles of all the polarization maintaining optical fiber joints are 0-0 degree;
The polarization beam splitting differential detection device (140) consists of a polarization-maintaining circulator (141), a 1 st polarization beam splitter (142), a 2 nd polarization beam splitter (145), and a 1 st differential detector (143, 146, 144, 147) and a 2 nd differential detector (147); a first input end (c1) of the polarization-maintaining optical fiber coupler (131) is connected with the 1 st polarization beam splitter (142) through a polarization-maintaining circulator (141), a second input end (c2) of the polarization-maintaining optical fiber coupler (131) is connected with the 2 nd polarization beam splitter (145), and the axial angles of all the polarization-maintaining optical fiber joints are 0-0 degree; the 1 st differential detector (143 and 146) is connected with the fast axis signal output ends of the 1 st and 2 nd polarization beam splitters (142 and 145), and the 2 nd differential detector (144 and 147) is connected with the slow axis signal output ends of the 1 st and 2 nd polarization beam splitters (142 and 145);
the method is characterized by comprising the following steps:
1) In a laboratory, a sensing arm of the measuring device is in a constant temperature environment, a displacement table is used for applying tensile stress, displacement data and phase change data are recorded, and the strain coefficients of a slow-axis x-axis interferometer and a fast-axis y-axis interferometer are calculatedand used as known constants for later calculation;
2) In the laboratoryIn the method, the sensing arm of the measuring device is in a relaxed state, the ambient temperature is changed, phase change data is recorded, and the strain coefficients of a slow-axis x-axis interferometer and a fast-axis y-axis interferometer are calculatedAnd used as known constants for later calculation;
3) The measuring device is placed in a test environment, a sensing arm optical fiber of the interferometer is fixedly attached to the surface of an object to be measured, the strain epsilon and the environment temperature change delta T of the object to be measured are transmitted to the sensing optical fiber through contact or media, finally, the phase demodulated by an interference signal changes, the phase data of the fast-axis and slow-axis interferometers are recorded, and delta phi is obtainedx、Δφy；
4) Constant measured in laboratoryandAnd delta phi obtained in the test environmentx、Δφy(ii) a Carry-in typeand calculating to obtain the strain parameter and the temperature change of the environment to be measured.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711310550.3A CN108168728B (en) | 2017-12-11 | 2017-12-11 | device and method for simultaneously measuring temperature strain of unbalanced polarization maintaining optical fiber double interferometers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711310550.3A CN108168728B (en) | 2017-12-11 | 2017-12-11 | device and method for simultaneously measuring temperature strain of unbalanced polarization maintaining optical fiber double interferometers |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108168728A CN108168728A (en) | 2018-06-15 |
| CN108168728B true CN108168728B (en) | 2019-12-10 |
Family
ID=62524891
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201711310550.3A Active CN108168728B (en) | 2017-12-11 | 2017-12-11 | device and method for simultaneously measuring temperature strain of unbalanced polarization maintaining optical fiber double interferometers |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108168728B (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109946042B (en) * | 2019-03-06 | 2020-07-14 | 湖北三江航天红峰控制有限公司 | Method and device for measuring coupling precision of Y-shaped waveguide |
| CN109916533B (en) * | 2019-03-15 | 2021-04-20 | 哈尔滨工程大学 | PDH demodulation polarization maintaining grating FP cavity temperature strain simultaneous measurement device |
| CN110426129B (en) * | 2019-06-25 | 2021-01-15 | 太原理工大学 | Device and method for measuring cross correlation of different light fields based on photon interference |
| CN111308547B (en) * | 2020-03-21 | 2022-09-27 | 哈尔滨工程大学 | Six-dimensional seismic wave measuring device based on composite interferometer |
| CN111426856A (en) * | 2020-03-21 | 2020-07-17 | 哈尔滨工程大学 | Michelson-Sagnac composite dual-polarization fiber interferometer with single light source |
| CN111337009B (en) * | 2020-04-24 | 2022-02-01 | 中山大学 | Ultrasonic measuring device for realizing differential balance detection based on SAGNAC principle |
| CN112033301B (en) * | 2020-08-07 | 2021-05-07 | 太原理工大学 | Scrape trigger crookedness optical fiber measurement system |
| CN112525373B (en) * | 2020-11-10 | 2023-05-12 | 广东工业大学 | Strain temperature simultaneous measurement device based on dual-wavelength polarization-maintaining optical fiber interferometer |
| CN112525372B (en) * | 2020-11-10 | 2023-06-27 | 广东工业大学 | Strain temperature simultaneous measurement device and method based on polarization maintaining optical fiber double-arm different-axis interferometer |
| CN112485467B (en) * | 2020-11-10 | 2024-04-09 | 广东工业大学 | Temperature compensation accelerometer based on polarization maintaining optical fiber double-arm different-axis interferometer |
| CN113097842B (en) * | 2021-03-29 | 2022-11-08 | 中国科学院上海光学精密机械研究所 | Polarization maintaining fiber-based ultrastable laser system |
| CN113251937B (en) * | 2021-04-13 | 2022-09-06 | 董永康 | Method and device for measuring diameter of cladding of polarization maintaining optical fiber |
| CN113108710B (en) * | 2021-04-14 | 2022-05-03 | 安徽大学 | Optical low-frequency strain detection system and detection method based on ellipse fitting |
| CN113639652B (en) * | 2021-08-31 | 2024-04-12 | 中电科思仪科技股份有限公司 | Automatic testing and analyzing method for strain distribution of optical fiber hydrophone |
| CN113532307B (en) * | 2021-09-09 | 2021-11-30 | 南京信息工程大学 | Wide-range strain sensor based on Michelson fiber optic interferometer |
| CN116878394B (en) * | 2023-08-02 | 2024-04-19 | 哈尔滨工业大学 | Interference displacement measurement system and method for polarized light phase modulation of microprobe |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2311600A (en) * | 1996-03-29 | 1997-10-01 | Secr Defence | Optic Fibre Interferometric sensor |
| CN2531369Y (en) * | 2002-03-08 | 2003-01-15 | 电子科技大学 | Optical fiber Michelson interferometer having light circulator |
| CN102162742B (en) * | 2011-01-07 | 2012-08-22 | 哈尔滨工程大学 | Quasi-distribution optical fiber white-light strain sensing and demodulation device based on nonequilibrium Michelson interferometer |
| CN104180831A (en) * | 2013-05-24 | 2014-12-03 | 无锡万润光子技术有限公司 | Sensitivity-enhanced optical time domain reflection distributed Michelson interferometer based on two-core optical fiber |
| US9476699B2 (en) * | 2015-03-05 | 2016-10-25 | General Photonics Corporation | Measurements of strain, stress and temperature by using 1-dimensional and 2-dimensional distributed fiber-optic sensors based on sensing by polarization maintaining fiber of distributed polarization crosstalk distribution |
| CN105698871B (en) * | 2016-03-29 | 2018-08-21 | 天津大学 | Distributed strain temperature simultaneously measuring device and method based on probe beam deflation |
-
2017
- 2017-12-11 CN CN201711310550.3A patent/CN108168728B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN108168728A (en) | 2018-06-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108168728B (en) | device and method for simultaneously measuring temperature strain of unbalanced polarization maintaining optical fiber double interferometers | |
| Tian et al. | High-sensitivity fiber-optic strain sensor based on the Vernier effect and separated Fabry–Perot interferometers | |
| Zhang et al. | Micro-fiber-based FBG sensor for simultaneous measurement of vibration and temperature | |
| Cai et al. | A fiber ring cavity laser sensor for refractive index and temperature measurement with core-offset modal interferometer as tunable filter | |
| Tang et al. | High-performance bending vector and strain sensor using a dual-tapered photonic crystal fiber Mach–Zehnder interferometer | |
| Zhang et al. | Highly sensitive temperature and strain sensor based on fiber Sagnac interferometer with Vernier effect | |
| Liu et al. | Fiber in-line Mach–Zehnder interferometer for gas pressure sensing | |
| Huang et al. | In-fiber Mach-Zehnder interferometer exploiting a micro-cavity for strain and temperature simultaneous measurement | |
| CN112525373B (en) | Strain temperature simultaneous measurement device based on dual-wavelength polarization-maintaining optical fiber interferometer | |
| Dong et al. | Cladding-mode resonance in polarization-maintaining photonic-crystal-fiber-based sagnac interferometer and its application for fiber sensor | |
| CN112525372B (en) | Strain temperature simultaneous measurement device and method based on polarization maintaining optical fiber double-arm different-axis interferometer | |
| Ying et al. | Demodulation method of Fabry-Perot sensor by cascading a traditional Mach-Zehnder interferometer | |
| CN105093136A (en) | All-fiber weak magnetic field measuring device | |
| Wei et al. | Tunable multimode fiber based filter and its application in cost-effective interrogation of fiber-optic temperature sensors | |
| Zhao et al. | In-fiber Mach–Zehnder interferometer based on up-taper fiber structure with Er3+ doped fiber ring laser | |
| Ma et al. | Simultaneous measurement of temperature and pressure by utilizing an integrated Mach-Zehnder | |
| Wu et al. | Highly sensitive force sensor based on balloon-like interferometer | |
| CN108132067A (en) | A kind of polarization maintaining optical fibre interferometer of passive temperature compensation and its compensation method | |
| Gang et al. | A novel strain sensor using a fiber taper cascaded with an air bubble based on Fabry–Pérot interferometer | |
| Liu et al. | Review of fiber mechanical and thermal multi-parameter measurement technologies and instrumentation | |
| Zhang et al. | High-sensitivity transverse-load and axial-strain sensor based on air-bubble Fabry–Pérot cavity and fiber Sagnac loop cascaded | |
| Yao et al. | 7-core fiber-based high-resolution omnidirectional vector bending sensor enabled by microwave photonics filter | |
| Li et al. | Inconsistency measurement between two branches of LiNbO3 integrated optic Y-junction | |
| CN103134627B (en) | Temperature insensitive stress sensor based on low birefringence polarization maintaining fiber loop mirror (PM-FLM) | |
| Zhang et al. | Distributed polarization characteristic testing for optical closed loop of Sagnac interferometer |
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 | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |