CN114739545B - PBS-based high-frequency vibration information demodulation system and calibration method - Google Patents
PBS-based high-frequency vibration information demodulation system and calibration method Download PDFInfo
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- G—PHYSICS
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
- G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
- G01L27/002—Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination
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Abstract
The application discloses a PBS-based high-frequency vibration information demodulation system and a calibration method, wherein a second mechanical three-ring polarization controller is manually adjusted to adjust the polarization rotation axis of a GP branch to beAdjusting the first mechanical tricyclic polarization controller to make the incident polarization state be the optimal polarization state s op = (0, 1, 0); continuously applying overload dynamic pressure, and adjusting the third mechanical three-ring polarization controller; on a PBS data reading software interface on a computer, the voltage waveforms of the two paths of photodetectors are characterized by opposite phases, maximum peak-to-peak values and concave symmetry of the peaks and the valleys. The method is used for detecting polarization information change caused by pressure-induced birefringence, and takes the overload dynamic pressure time domain response waveform as an observation object, so that the adjusting method is simple and easy to realize.
Description
Technical Field
The application relates to the field of photoelectric sensors and photoelectricity, in particular to a calibration method of a high-frequency vibration information demodulation system in an optical fiber sensing method for monitoring pressure in real time by utilizing Stokes parameters of optical fiber transmitted light.
Background
When the optical fiber is affected by external environment (temperature, stress, magnetic field, pressure, etc.), parameters such as intensity, phase, frequency, polarization state, etc. of transmitted light in the optical fiber can be changed correspondingly. By detecting these parameters of the transmitted light, the change of the corresponding physical quantity is known, which is called optical fiber sensing technology.
Research and experiments show that under the action of pressure, the birefringence phenomenon generated in an optical fiber can cause the polarization state of light to change, and the polarization state can be characterized by Stokes parameters, and the polarization state comprises three normalized Stokes components. Dynamic pressure sensing can be achieved by detection of stokes parameters at a single wavelength point. And can convert displacement, acceleration, current, underwater acoustic signal and other variables into pressure-induced birefringence changes through various transduction structures such as cantilever beams, magnets, diaphragms and the like, thereby realizing the measurement of various variables by utilizing polarization states.
The traditional stokes parameter measurement principle is a wave division mode, namely light to be measured is divided into four beams, then polarization analyzers or 1/4 wave plates in different directions are respectively applied to the beams, and after photoelectric detection, output photocurrents are calculated to obtain three normalized stokes parameters. Because the analyzer and the wave plate have discrete devices and no optical fiber online devices at present, the collimation of light beams, the precise adjustment of angles of the analyzer and the wave plate and the integrated treatment of the devices have very strict requirements on the process and the packaging, the core process technology is monopoly abroad, and the cost is relatively high. Meanwhile, the polarization test card of foreign companies adopts a non-terminal test mode, so that the bandwidth is limited, and the bandwidth expansion is difficult to carry out.
Therefore, a scheme of demodulating all-fiber polarization information in a non-discrete component and terminal test mode is proposed later, namely, a polarization state detection is performed by using an all-fiber polarization measurement system consisting of a fiber polarization controller (polarization controller, PC) and a fiber polarization beam splitter (polarizationbeam splitter, PBS). In the polarization state measurement scheme, a commercial polarization state analyzer is firstly required to calibrate and scale the system, the calibration mode is to input specific three polarization states respectively, and after each polarization state change, a Polarization Controller (PC) is regulated to enable the intensity of two paths of output light of a fiber Polarization Beam Splitter (PBS) to meet a specific relation. However, the calibration method is a blind adjustment process, the adjustment process is complicated, and the PC is changed for many times, so that the light intensity requirements of three specific input polarization states can be met at the same time, the experience of a debugger is extremely depended, and theoretical guidance on the reproduction of the system is lacking.
Disclosure of Invention
The application aims to provide a PBS-based high-frequency vibration information demodulation system and a calibration method, which are used for detecting polarization information change caused by pressure-induced birefringence, and the adjustment method is simple and easy to realize by using an overload dynamic pressure time domain response waveform as an observation object.
The high-frequency vibration information demodulation system based on PBS comprises a semiconductor laser, a first mechanical three-ring polarization controller, a 1:9 optical coupler, a second mechanical three-ring polarization controller, a general electric polarization state on-line monitoring module, a first A/D conversion signal acquisition card, a third mechanical three-ring polarization controller, a polarization beam splitter, a first photoelectric detector, a second A/D conversion signal acquisition card and a computer,
the semiconductor laser is connected with the 1:9 optical coupler through the first mechanical three-ring polarization controller, the output end of the 1:9 optical coupler is respectively connected with the input ends of the second mechanical three-ring polarization controller and the third mechanical three-ring polarization controller, the output end of the second mechanical three-ring polarization controller is connected with the universal electric polarization state on-line monitoring module and the A/D conversion signal acquisition card in series, and the output end of the A/D conversion signal acquisition card is connected with the computer; the output end of the third mechanical type tricyclic polarization controller is connected with the input end of the polarization beam splitter, the output end of the polarization beam splitter is respectively connected with the input ends of the first photoelectric detector and the second photoelectric detector, the output ends of the first photoelectric detector and the second photoelectric detector are respectively connected with the input end of the second A/D conversion signal acquisition card, and the output end of the second A/D conversion signal acquisition card is connected with the computer.
Preferably, a sensor head is connected in series between the first mechanical three-ring polarization controller and the 1:9 optical coupler, and the sensor head comprises a signal generator, a driver and a test optical fiber which are connected in series.
Preferably, the second mechanical tricyclic polarization controller, the universal electric polarization state on-line monitoring module, the first A/D conversion signal acquisition card and the computer form a GP branch; the third mechanical three-ring polarization controller, the polarization beam splitter, the first photoelectric detector, the second A/D conversion signal acquisition card and the computer form a PBS branch; the first mechanical three-ring polarization controller, the sensing head, the 1:9 optical coupler, the third mechanical three-ring polarization controller, the polarization beam splitter, the first photoelectric detector, the second A/D conversion signal acquisition card and the computer form a calibrated branch.
The application relates to a calibration method of a calibration device of a high-frequency vibration information demodulation system based on PBS, which comprises the following steps:
step 001: manually adjusting a second mechanical tricyclic polarization controller to adjust the polarization rotation axis of the GP branch to
Opening a vibration source, generating overload dynamic pressure by applying voltage on the vibration exciter, forming a track circle on the bonding ball of the computer interface, and adjusting the second mechanical three-ring polarization controller to enable the track circle to be parallel to the equator of the bonding ball;
step 002: adjusting the first mechanical tricyclic polarization controller to make the incident polarization state be the optimal polarization state s op ＝(0,1,0)；
Closing the excitation source, adjusting the first mechanical three-ring polarization controller, observing the GP branch software interface, and adjusting the polarization state to (0, 1, 0);
opening the excitation source, observing whether a track circle formed on the bonding ball of the computer interface is on the equator or not, if yes, repeating the first step to carry out fine adjustment;
step 003: the third mechanical three-ring polarization controller is adjusted to make the polarization rotation axis of the PBS branch be
Continuously applying overload dynamic pressure on the basis of the second step, and adjusting the third mechanical three-ring polarization controller; on a PBS data reading software interface on a computer, the voltage waveforms of the two paths of photodetectors are characterized by opposite phases, maximum peak-to-peak values and concave symmetry of the peaks and the valleys.
Preferably, the specific process of step 001 of the present application is: applying a sinusoidal pressure signal to the optical fiber by using a vibration exciter, wherein the sinusoidal pressure signal is an overload signal compared with a relation curve of Stokes parameters and pressure of the optical fiber, manually adjusting a second mechanical three-ring polarization controller, observing a GP shunt waveform interface, and adjusting a polarization rotation axis of the GP branch to
Preferably, the specific process of step 002 of the present application is: adjusting the first mechanical tricyclic polarization controller such that s 1 The peak value of the waveform is 2, and bilateral distortion with concave symmetry of the wave peak and the wave trough exists; s is(s) 2 The waveform can generate stable frequency doubling signals; s is(s) 3 The waveform is approximately a straight line and has a value of 0; the GP leg is considered to be adjusted to a predetermined position as a reference standard for the PBS leg.
Preferably, the specific process of step 003 of the present application is: on the basis of the incident polarization state being adjusted to (0, 1, 0), continuously applying dynamic pressure exceeding the size of a monotonic interval, and adjusting a third mechanical tricyclic polarization controller, wherein the aim is to adjust the polarization rotation axis of the PBS branch to be consistent with the GP branch (0, 1, 0), and the PBS branch reflects s 1 The size of the waveform peak-to-peak value; at this time s 1 The peak value of the waveform reaches 2, and the concave degree of the wave crest and the wave trough is consistent; thus the output voltage waveform of the PBS branchFeatures are as follows 1 The waveform peak is consistent, namely the voltage waveform characteristics of the two paths of photodetectors on the PBS data reading software interface are opposite in phase, and the voltage peak value V of the signal voltage peak of the first photodetector C And a signal voltage peak-to-peak value V of the second photodetector D Maximum and consistent concave degree of the wave crest and the wave trough is achieved.
The calibration device and the method of the PBS-based high-frequency offset information demodulation system use the time domain response waveform of the dynamic pressure as an observation object in the calibration process, and can directly adjust the polarization rotation axis on the interface of the commercial polarimeter by applying the dynamic pressure. Meanwhile, the third mechanical type tri-ring polarization controller of the PBS branch is adjusted by utilizing the symmetry of waveform indent under overload pressure, so that the complexity of adjustment is greatly reduced, and the adjustment time is saved. The method provides reliable theoretical support for reproduction of the calibration process, and the calibration process is not a blind adjustment process any more and no longer depends on experience of a debugger. The calibration scheme is helpful to construct a polarization information demodulation system with simple structure and low cost, and can demodulate the pressure information contained therein, thereby meeting the requirement of high-frequency dynamic pressure real-time monitoring.
Drawings
FIG. 1 is a schematic diagram of the mapping relationship between the force of an extruded fiber optic sensor head and Stokes parameters. Wherein a represents the motion track of Stokes parameters on the bunsen balls under the action of pressure; b represents the stokes parameter versus pressure.
Fig. 2 is a system configuration diagram of the scaling device of the present application.
FIG. 3 is a schematic flow chart of the calibration method of the present application.
FIG. 4 is a schematic diagram of the interface of the GP shunt waveform in step 001 of the calibration method of the present application.
Fig. 5 is a schematic diagram of a PBS shunt waveform interface in step 003 of the calibration method of the present application. Wherein a represents a schematic diagram of a voltage waveform of a scaling signal of the first photodetector; b represents a schematic diagram of a voltage waveform of a scaling signal of the second photodetector.
FIG. 6 is a waveform of the output of the two branches with their polarization rotation axes adjusted in unison in an embodiment of the application. Wherein a represents a GP branch output waveform schematic diagram; b represents a schematic diagram of the output waveform of the PBS leg.
FIG. 7 is a graph of adjusting the polarization state of incident light to s op After= (1, 0), the corresponding GP leg waveform is compared with the PBS leg equalized normalized waveform. Wherein a represents a GP branch waveform schematic diagram; b represents a schematic diagram of the PBS leg waveform.
Fig. 8 is a schematic diagram of a waveform of a high frequency offset demodulation information oscilloscope.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to specific embodiments of the present application and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The following describes in detail the technical solutions provided by the embodiments of the present application with reference to the accompanying drawings.
1. Principle of:
a 4 x 4 matrix M, i.e. a mueller matrix, may be used in an optical transmission system to represent the transmission characteristics of the optical device with respect to polarization. The polarization state of the incident light is expressed by stokes parameters: (S) 0 ,S 1 ,S 2 ,S 3 ) in T The polarization state of the outgoing light obtained after passing through the optical device (S 0 ,S 1 ,S 2 ,S 3 ) out T The method comprises the following steps:
by S 0 The other three parameters are normalized to obtain normalized Stokes parameters (S 1 /S 0 ,S 2 /S 0 ,S 3 /S 0 ) I.e.(s) 1 ,s 2 ,s 3 ) The mueller matrix may also be degraded toA 3 x 3 rotation matrix. The polarization state of the incident light at this time is s in And the polarization state s of the emergent light out The relation of (2) is:
s out ＝Ms in
the Mueller matrix of the extruded fiber optic sensor head is a coordinate transformation matrix describing any angle of rotation about any axis in three dimensions, where the axis refers to the intrinsic axis of rotation of the sensor headThe polarization state will be about the intrinsic axis of rotation under pressure>The rotation, polarization state trajectory depends on the location of the incident polarization state and the direction of the intrinsic rotation axis. So that a cosine-varying relationship exists between the stokes parameter and the external pressure. The sensing can thus be achieved by measuring the stokes parameter, using a monotonic interval of the sinusoid. If the peak-to-peak value of the applied dynamic force exceeds a monotonic interval, it is referred to as overload pressure.
As shown in fig. 2, the laser is used as a light source, firstly, the incident polarization state of the whole system is controlled by the PC1, then the whole system is split into two parts by using a coupler, and the two parts enter a polarization measurement module (i.e., GP branch) and an all-fiber polarization measurement system (i.e., PBS branch) formed by the PC and the PBS respectively, wherein the GP branch is used as a reference standard, and the PBS branch is calibrated. A point is selected between the coupler and the PC1 as an application point of external pressure, and is set as A, and the incident polarization state is s A ＝(s A1 ,s A2 ,s A3 ). Because the output Stokes parameters of the two branches gradually become larger along with the point A, sinusoidal changes are shown, namely, the Mueller matrixes of the two branches along with the pressure changes are respectively as follows:
the polarization state of the light output by the GP branch is obtained through deduction is as follows:
namely, three normalized stokes vectors of the GP branch output polarization states are respectively:
s GP,1 ＝b 11 (F)s A1 +b 12 (F)s A2 +b 13 (F)s A3
s GP,2 ＝b 21 (F)s A1 +b 22 (F)s A2 +b 23 (F)s A3
s GP,3 ＝b 31 (F)s A1 +b 32 (F)s A2 +b 33 (F)s A3
and the output voltage of the PBS branch is:
V OUT (F)＝R(a 11 (F)s A1 +a 12 (F)s A2 +a 13 (F)s A3 )
where R is a constant associated with the photodetector.
The mathematical conditions for the PBS leg to complete the scaling are therefore as follows:
when a is 11 ＝b 11 ,a 12 ＝b 12 ,a 13 ＝b 13 V at the time of OUT Output reflects GP way s 1 Is of a size of (a) and (b).
When a is 11 ＝b 21 ,a 12 ＝b 22 ,a 13 ＝b 23 V at the time of OUT Output reflects GP way s 2 Is of a size of (a) and (b).
When a is 11 ＝b 31 ,a 12 ＝b 32 ,a 13 ＝b 33 V at the time of OUT Output reflects GP way s 3 Is of a size of (a) and (b).
The above is the mathematical model support for the calibration method.
In the present pressure sensor only one si is requiredToxose parameters. Therefore, the axes of the upper and lower branches are adjusted to be consistent, and the first mathematical condition of conclusion can be satisfied OUT The output of (a) is s of GP path 1 . Through theoretical analysis, for s 1 For reference, the sinusoidal performance curve is optimized, and the polarization rotation axis and the optimal incident polarization state can be selected as follows:
shaftThe corresponding optimal polarization state is s op = (0, 1, 0) or s op ＝(0,-1,0)；
ShaftThe corresponding optimal polarization state is s op = (0, 1) or s op ＝(0,0,-1)；
In the calibration scheme, the polarization rotation axis is usedOptimal polarization state s op = (0, 1, 0) as an example.
FIG. 1 is a schematic diagram of the mapping relationship between the force of an extruded fiber optic sensor head and Stokes parameters. Wherein a represents the motion track of Stokes parameters on the bunsen balls under the action of pressure; b represents the stokes parameter versus pressure. The Mueller matrix of the extruded fiber optic sensor head is a coordinate transformation matrix describing any angle of rotation about any axis in three dimensions, where the axis refers to the intrinsic axis of rotation of the sensor headThe polarization state will be about the intrinsic rotation axis under pressureThe rotation, as shown in part a of fig. 1, the polarization state trajectory depends on the location of the incident polarization state and the direction of the intrinsic rotation axis. So that a cosine-varying relation exists between the stokes quantity and the external pressure, as shown in part b of fig. 1. Because ofThis can be achieved by measuring the stokes parameter, using a monotonic interval of the sinusoid. If the peak-to-peak value of the applied dynamic force exceeds a monotonic interval, it is referred to as overload pressure.
Fig. 2 is a system structure diagram of a calibration method of a high-frequency vibration information demodulation system based on a PBS, which is provided in an embodiment of the present application, as shown in fig. 1, the calibration system of the high-frequency vibration information demodulation system based on the PBS includes a semiconductor laser TLS, a mechanical three-ring polarization controller PC, a 1:9 optical coupler, a polarization beam splitter PBS, a photodetector PD, a general electric GP polarization on-line monitoring module, an a/D conversion signal acquisition card, and a computer.
In this embodiment, the first mechanical three-ring polarization controller PC1, the sensing head, the second mechanical three-ring polarization controller PC2, the general electric GP polarization on-line monitoring module, the a/D conversion signal acquisition card, and the computer constitute a reference standard branch, because the branch mainly uses the on-line polarization monitoring module of the general electric GP to detect the polarization state, and converts the polarization state into an electrical signal through the photoelectric detector of the general electric GP on-line polarization monitoring module, and then maps the electrical signal to the computer in real time through the a/D conversion signal acquisition card, so the GP branch is abbreviated. The branch is mainly used as a reference standard to provide support for calibration of the measuring branch. The first mechanical three-ring polarization controller PC1, the sensing head, the third mechanical three-ring polarization controller PC3, the polarization beam splitter PBS, the photoelectric detector PD, the A/D conversion signal acquisition card and the computer form a calibrated branch, and the branch mainly uses the polarization beam splitter PBS and the photoelectric detector PD to detect the polarization state, converts the polarization state into an electric signal through the photoelectric detector, and maps the electric signal to the computer in real time through the A/D conversion signal acquisition card, so the branch is called PBS for short. The branch is a measurement branch and is a measurement subject of the embodiment.
As an implementation mode of the embodiment of the application, the semiconductor laser is connected with a common single-mode optical fiber between PCs, between 1:9 optical couplers and PCs, between PCs and PBS, between PCs and GP, the PC is connected with the 1:9 optical couplers with bare wires of the single-mode optical fiber, and the PBS is directly connected with the photo detector PD. The bare wire of the same single-mode fiber between the PC and the 1:9 optical coupler is used as a sensing head when the vibration source vibrates.
Fig. 3 is a flowchart of a calibration method based on a PBS high frequency offset information demodulation system according to an embodiment of the present application, where the calibration method based on the PBS high frequency offset information demodulation system according to the embodiment includes the following steps:
step 001: manually adjusting PC2, observing GP shunt waveform interface until the rotation axis is adjusted to be
In step 001, a sinusoidal pressure signal is applied to the fiber using a vibration exciter. The pressure signal is an overload signal compared to the fiber Stokes parameter versus pressure curve. Manually adjusting PC2, observing a GP shunt waveform interface, and adjusting the polarization rotation axis of the GP shunt to be at the moment when the locus circle of Stokes parameters appears on the interface and is parallel to the equator of the Bangka sphere
Step 002: PC1 is regulated to make the incident polarization state be the optimal polarization state s op ＝(0,1,0)。
In step 002, PC1 is adjusted so that s 1 The peak value of the waveform is 2, and bilateral distortion with concave symmetry of the wave peak and the wave trough exists; s is(s) 2 The waveform can generate stable frequency doubling signals; s is(s) 3 The waveform is approximately a straight line and has a value of 0. The GP leg may be considered to be adjusted to a predetermined position and may be used as a reference for the PBS leg.
Step 003: PC3 is adjusted to observe the PBS branching waveform interface, so that the polarization rotation axis of the PBS branching is
In step 003, dynamic pressure exceeding the magnitude of the monotonic interval is continuously applied to adjust PC3 based on the incident polarization state being adjusted to (0, 1, 0), with the objective of adjusting the polarization rotation axis of the PBS leg to (0, 1, 0) coincident with the GP leg, at which time the PBS leg reflectsIs s is 1 Is of a size of (a) and (b). At this time s 1 The peak-to-peak value reaches 2 and the concave degree of the peak and the trough is consistent. Therefore, the voltage waveform characteristics of the PBS branch should be consistent with the voltage waveform characteristics of the two paths of photodetectors on the PBS data reading software interface, namely the voltage waveform characteristics of the two paths of photodetectors are opposite in phase and peak-to-peak V C 、V D Maximum and consistent concave degree of the wave crest and the wave trough is achieved.
In step 004, in order to verify that the trajectory circle of the PBS branch is consistent with the trajectory circle of the GP branch, the (1, 0) is taken as the incident polarization state, whether the PBS branch waveform at this time accords with the theory is observed, and whether the GP branch is consistent with the PBS branch waveform is observed.
FIG. 4 shows the GP shunt waveform interface in step 001, as shown in FIG. 4, when the waveforms of the three Stokes parameter components at the display interface simultaneously satisfy the following waveform conditions, the polarization rotation axis of the shunt at this time isThe incident polarization state is s op ＝(0,1,0)：s 1 The peak value of the waveform is 2, and the concave symmetrical bilateral distortion phenomenon occurs in the wave peak and wave trough; s is(s) 2 The waveform is a stable frequency doubling signal; s is(s) 3 The waveform is a straight line.
FIG. 5 shows a PBS shunt waveform interface in step 003. As shown in FIG. 5, when waveforms detected by two photodetectors of a PBS shunt meet the waveform condition that voltage waveforms of the two photodetectors are characterized by opposite phases, maximum peak-to-peak values and consistent peak-to-trough indent degrees, the shunt has an incident polarization state of s op On the premise of = (0, 1, 0), its polarization rotation axis is
FIG. 6 is a waveform of the output of the two branches with their polarization rotation axes adjusted in unison in an embodiment of the application. Wherein a represents a GP branch output waveform schematic diagram; b represents a schematic diagram of the output waveform of the PBS leg. As shown in FIG. 6, in the calibration scheme of the PBS-based high-frequency vibration information demodulation system provided by the embodiment of the application, a low-frequency sinusoidal pressure signal is continuously provided for a sensing head at a vibration excitation source, and the headFirstly, PC2 is regulated to make the polarization rotation axis of GP branch beThen the excitation source is closed, and PC1 is regulated to make the incident polarization state detected by GP branch be s op = (0, 1, 0), in case of being adjusted at this time, the excitation source is turned on, and the corresponding output waveform is shown as a part a in fig. 6. And then, under the condition that the excitation source is started, the PC3 is regulated so that the output waveform of the path is consistent with the output waveform of the GP branch, namely the part b in fig. 6. At this time, the output polarization state of the PBS branch corresponds to s of the GP branch 1 A component.
FIG. 7 is a graph of adjusting the polarization state of incident light to s op After= (1, 0), the corresponding GP leg waveform is compared with the PBS leg equalized normalized waveform. Wherein a represents a GP branch waveform schematic diagram; b represents a schematic diagram of the PBS leg waveform. The waveform phenomenon of the two branches is a frequency division phenomenon, and the corresponding data are similar.
Fig. 8 is a waveform of a high frequency offset demodulation information oscilloscope. As shown in FIG. 8, according to the calibration scheme of the PBS-based high-frequency vibration information demodulation system provided by the embodiment of the application, 25MHz incident polarized signal is passed through the calibrated system, the output polarized signal frequency can be seen to be 25MHz on an oscilloscope, and the calibrated system is proved to be capable of monitoring high-frequency signals in real time.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and variations of the present application will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.
Claims (4)
1. The calibration method of the PBS-based high-frequency vibration information demodulation system is characterized by comprising a semiconductor laser, a first mechanical three-ring polarization controller, a 1:9 optical coupler, a second mechanical three-ring polarization controller, a general electric polarization state on-line monitoring module, a first A/D conversion signal acquisition card, a third mechanical three-ring polarization controller, a polarization beam splitter, a first photoelectric detector, a second A/D conversion signal acquisition card and a computer;
the semiconductor laser is connected with the 1:9 optical coupler through the first mechanical three-ring polarization controller, the output end of the 1:9 optical coupler is respectively connected with the input ends of the second mechanical three-ring polarization controller and the third mechanical three-ring polarization controller, the output end of the second mechanical three-ring polarization controller is connected with the universal electric polarization state on-line monitoring module and the A/D conversion signal acquisition card in series, and the output end of the A/D conversion signal acquisition card is connected with the computer; the output end of the third mechanical three-ring polarization controller is connected with the input end of the polarization beam splitter, the output end of the polarization beam splitter is respectively connected with the input ends of the first photoelectric detector and the second photoelectric detector, the output ends of the first photoelectric detector and the second photoelectric detector are respectively connected with the input end of the second A/D conversion signal acquisition card, and the output end of the second A/D conversion signal acquisition card is connected with the computer;
a sensing head is connected in series between the first mechanical three-ring polarization controller and the 1:9 optical coupler, and the sensing head comprises a signal generator, a driver and a test optical fiber which are connected in series;
the second mechanical three-ring polarization controller, the universal electric polarization state on-line monitoring module, the first A/D conversion signal acquisition card and the computer form a GP branch; the third mechanical three-ring polarization controller, the polarization beam splitter, the first photoelectric detector, the second A/D conversion signal acquisition card and the computer form a PBS branch; the first mechanical three-ring polarization controller, the sensing head, the 1:9 optical coupler, the third mechanical three-ring polarization controller, the polarization beam splitter, the first photoelectric detector, the second A/D conversion signal acquisition card and the computer form a calibrated branch;
the calibration method comprises the following steps:
step 001: manually adjusting a second mechanical tricyclic polarization controller to adjust the polarization rotation axis of the GP branch to
Opening a vibration source, generating overload dynamic pressure by applying voltage on the vibration exciter, forming a track circle on the bonding ball of the computer interface, and adjusting the second mechanical three-ring polarization controller to enable the track circle to be parallel to the equator of the bonding ball;
step 002: adjusting the first mechanical tricyclic polarization controller to make the incident polarization state be the optimal polarization state s op ＝(0,1,0)；
Closing the excitation source, adjusting the first mechanical three-ring polarization controller, observing the GP branch software interface, and adjusting the polarization state to (0, 1, 0);
opening the excitation source, observing whether a track circle formed on the bonding ball of the computer interface is on the equator or not, if yes, repeating the first step to carry out fine adjustment;
step 003: the third mechanical three-ring polarization controller is adjusted to make the polarization rotation axis of the PBS branch be
Continuously applying overload dynamic pressure on the basis of the second step, and adjusting the third mechanical three-ring polarization controller; on a PBS data reading software interface on a computer, the voltage waveforms of the two paths of photodetectors are characterized by opposite phases, maximum peak-to-peak values and concave symmetry of the peaks and the valleys.
2. The calibration method according to claim 1, wherein the specific process of the step 001 is as follows: applying a sinusoidal pressure signal to the optical fiber by using a vibration exciter, wherein the sinusoidal pressure signal is an overload signal compared with a relation curve of Stokes parameters and pressure of the optical fiber, manually adjusting a second mechanical three-ring polarization controller, observing a GP shunt waveform interface, and adjusting a polarization rotation axis of the GP branch to
3. The calibration method according to claim 1, wherein the specific process of the step 002 is as follows: adjusting the first mechanical tricyclic polarization controller such that s 1 The peak value of the waveform is 2, and bilateral distortion with concave symmetry of the wave peak and the wave trough exists; s is(s) 2 The waveform can generate stable frequency doubling signals; s is(s) 3 The waveform is approximately a straight line and has a value of 0; the GP leg is considered to be adjusted to a predetermined position as a reference standard for the PBS leg.
4. The calibration method according to claim 1, wherein the specific process of the step 003 is as follows: on the basis of the incident polarization state being adjusted to (0, 1, 0), continuously applying dynamic pressure exceeding the size of a monotonic interval, and adjusting a third mechanical tricyclic polarization controller, wherein the aim is to adjust the polarization rotation axis of the PBS branch to be consistent with the GP branch (0, 1, 0), and the PBS branch reflects s 1 The size of the waveform peak-to-peak value; at this time s 1 The peak value of the waveform reaches 2, and the concave degree of the wave crest and the wave trough is consistent; therefore, the waveform characteristics of the output voltage of the PBS branch should be equal to s 1 The waveform peak is consistent, namely the voltage waveform characteristics of the two paths of photodetectors on the PBS data reading software interface are opposite in phase, and the voltage peak value V of the signal voltage peak of the first photodetector C And a signal voltage peak-to-peak value V of the second photodetector D Maximum and consistent concave degree of the wave crest and the wave trough is achieved.
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