Distributed sensing method and sensing device based on photonic crystal fiber

Abstract

The invention provides a distributed sensing method based on photonic crystal fibers, which comprises the following steps: performing frequency conversion detection on the photonic crystal fibers under different specified blood pressure fingers and specified temperature values to obtain an orthogonal polarization back Rayleigh scattering time domain curve set; calculating an orthogonal correlation peak frequency shift corresponding to each specified blood pressure value and a parallel correlation peak frequency shift corresponding to each specified temperature value according to each orthogonal polarization back Rayleigh scattering time domain curve set, and respectively establishing a corresponding relationship between the blood pressure and the orthogonal correlation peak frequency shift and a corresponding relationship between the temperature and the parallel correlation peak frequency shift; frequency conversion detection is conducted on the distributed sensing structures distributed in the blood vessels to be detected, and the actual blood pressure value and the actual temperature value of each measuring point position are calculated according to the corresponding relation and the frequency conversion detection result. The defect that only single-point measurement can be carried out in the prior art is overcome, and the high-sensitivity response and high-precision measurement characteristics to blood pressure and temperature changes are reserved.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing and medical technology, and in particular to a distributed sensing method and a sensing device based on photonic crystal optical fiber. Background Art

[0002] Fiber optic sensors have the advantages of small size, wide bandwidth, high sensitivity, no electromagnetic interference, corrosion resistance, high temperature resistance, high pressure resistance, and adaptability to harsh environments. Fiber optic sensors can be used as both information transmission media and sensor elements. They can continuously measure environmental parameters distributed along the length of the fiber, such as temperature, strain, etc., and can achieve perceptual measurements with extremely high measurement sensitivity. In view of their excellent technical solutions and low costs, fiber optic sensors have very broad prospects in medical applications.

[0003] Blood is the most important part of human health, so it is very important to monitor the patient's blood pressure and temperature clinically. At present, fiber optic sensing technology has been widely used in blood pressure and temperature monitoring applications. However, this type of application mainly uses fiber optic probes and light reflection principle technology for detection. This detection method can only achieve single-point measurement at a time, with low sensitivity, and cannot achieve simultaneous measurement of temperature and blood pressure at multiple points. Therefore, when it comes to multi-point monitoring of human blood vessels, multiple fiber optic probes are often required to perform multiple tests in multiple locations to obtain monitoring information at each point, which greatly increases the measurement cost.

[0004] In view of this, how to provide a distributed sensing method and sensing device based on photonic crystal fiber to solve the limitations of existing pressure detection methods and the difficulty in achieving distributed measurement is a problem to be solved in this technical field. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention aims to provide a distributed sensing method and a sensing device based on photonic crystal fiber to solve at least one of the above-mentioned technical problems.

[0006] In order to at least solve the above technical problems, in a first aspect, the present invention provides a distributed sensing method based on photonic crystal fiber, the method comprising:

[0007] Performing frequency conversion detection on the photonic crystal optical fiber in different designated measurement groups to obtain a set of orthogonal polarization back Rayleigh scattering time domain curves corresponding to each designated measurement group, wherein the designated measurement group includes a designated blood pressure value and a designated temperature value;

[0008] Calculating the orthogonal correlation peak frequency shift corresponding to each of the specified blood pressure values ​​and the parallel correlation peak frequency shift corresponding to each of the specified temperature values ​​according to each of the orthogonal polarization Rayleigh backscattering time domain curve sets, and establishing the corresponding relationships between the blood pressure and the orthogonal correlation peak frequency shift, and between the temperature and the parallel correlation peak frequency shift;

[0009] The distributed sensing structure is subjected to frequency conversion detection. The distributed sensing structure is a sensing structure with multiple measuring points formed by encapsulating the photonic crystal optical fiber and arranging it in multiple blood vessels to be measured. The actual blood pressure value and the actual temperature value at each measuring point are calculated based on the corresponding relationship and the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each measuring point calculated based on the frequency conversion detection result.

[0010] Preferably, the orthogonal polarization Rayleigh backscattering time domain curve set includes two orthogonal polarization Rayleigh backscattering time domain curves.

[0011] Preferably, the frequency conversion detection is performed on the photonic crystal optical fibers in different designated measurement groups to obtain a set of orthogonal polarization back-Rayleigh scattering time domain curves corresponding to each designated measurement group, including:

[0012] Frequency modulation is performed on a coherent light source with stable frequency to generate a swept frequency detection light with periodically changing frequency;

[0013] The frequency sweep detection light is pulse modulated and polarization multiplexed, and then input into the photonic crystal optical fiber in different designated measurement groups, so as to excite orthogonally polarized back-scattered Rayleigh light signals related to the orthogonal polarization transmission mode in the photonic crystal optical fiber;

[0014] The back-scattered Rayleigh light signal is converted into an electrical signal to obtain a set of orthogonal polarization back-scattered Rayleigh light time domain curves corresponding to each designated measurement group.

[0015] Preferably, the calculating, based on each of the orthogonal polarization Rayleigh backscattering time domain curve sets, the orthogonal correlation peak frequency shift corresponding to each of the specified blood pressure values ​​and the parallel correlation peak frequency shift corresponding to each of the specified temperature values ​​comprises:

[0016] Combining the orthogonal polarization Rayleigh backscattering time domain curve sets into a three-dimensional intensity spectrum set of orthogonal polarization Rayleigh backscattering time domain scattering whose intensity varies with optical fiber position and frequency;

[0017] Performing a two-dimensional cross-correlation operation on the orthogonal polarization backscattered Rayleigh time-domain scattering three-dimensional intensity spectrum set to obtain an orthogonal correlation peak frequency shift corresponding to the specified blood pressure value in each of the specified measurement groups;

[0018] The orthogonal polarization Rayleigh backscattering three-dimensional intensity spectrum set includes two orthogonal polarization Rayleigh backscattering three-dimensional intensity spectra.

[0019] Preferably, the calculation formula for performing a two-dimensional cross-correlation operation on the orthogonal polarization backscattering Rayleigh time-domain scattering three-dimensional intensity spectrum set is:

[0020] F xy (z) = argmax(correlation(I x (f,z),I y (f,z));

[0021] Among them, F xy (z) is the orthogonal correlation peak frequency shift distributed along the optical fiber position z, and the optical fiber position corresponds to the time axis; x (f,z) represents the three-dimensional intensity spectrum of the backscattered Rayleigh time domain scattering corresponding to the polarization state in the x polarization direction; I y (f,z) represents the three-dimensional intensity spectrum of the back Rayleigh time-domain scattering corresponding to the polarization state in the y polarization direction; correlation is the calculation symbol of the correlation coefficient, and argmax is the frequency of the corresponding position where the correlation coefficient is maximized.

[0022] Preferably, the calculating of the orthogonal correlation peak frequency shift of the corresponding designated blood pressure value and the parallel correlation peak frequency shift of the corresponding designated temperature value according to the orthogonal polarization Rayleigh backscattering time domain curve set further includes:

[0023] Randomly select a designated measurement group from the plurality of designated measurement groups as a reference measurement group, use two orthogonally polarized Rayleigh time-domain scattering three-dimensional intensity spectra of the reference measurement group as a reference intensity spectrum, and use two orthogonally polarized Rayleigh time-domain scattering three-dimensional intensity spectra corresponding to any designated measurement group different from the reference measurement group as a measurement intensity spectrum;

[0024] Perform a two-dimensional cross-correlation operation on each of the measured intensity spectra and the back Rayleigh time-domain scattering three-dimensional intensity spectrum having the same polarization state in the reference intensity spectrum, to obtain a correlation characteristic curve based on the x polarization direction and a correlation characteristic curve based on the y polarization direction of the measured intensity spectrum and the reference intensity spectrum, respectively, obtain the maximum values ​​of the two correlation characteristic curves and perform an average operation to obtain a parallel correlation comprehensive peak frequency shift;

[0025] The change value of the orthogonal correlation peak frequency shift of the measured intensity spectrum and the reference intensity spectrum is calculated, and the parallel correlation comprehensive peak frequency shift is subtracted from the change value to obtain the parallel correlation peak frequency shift of the specified temperature value corresponding to the measured intensity spectrum.

[0026] Preferably, the calculation formula involved in the parallel correlation peak frequency shift includes:

[0027] F xx (z) = argmax(correlation(I refx (f,z),I x (f,z));

[0028] F yy (z) = argmax(correlation(I refy (f,z),I y (f,z));

[0029] F(z)=(F xx (z)+F yy (z)) / 2-ΔF xy ;

[0030] Among them, F xx (z) represents the parallel correlation peak frequency shift corresponding to the polarization state in the x-polarization direction distributed along the optical fiber position z; F yy (z) represents the parallel correlation peak frequency shift corresponding to the polarization state in the y polarization direction distributed along the optical fiber position z; refx (f,z) represents the reference intensity spectrum corresponding to the polarization state in the x polarization direction; I refy (f,z) represents the reference intensity spectrum corresponding to the polarization state in the y polarization direction; x (f,z) represents the measured intensity spectrum corresponding to the polarization state in the x polarization direction; I y (f,z) represents the measured intensity spectrum corresponding to the polarization state in the y polarization direction; ΔF xy represents the change value of the orthogonal correlation peak frequency shift between the measured intensity spectrum and the reference intensity spectrum; F(z) represents the parallel correlation peak frequency shift distributed along the optical fiber position z.

[0031] Preferably, the establishing of the corresponding relationships between the blood pressure and the orthogonal correlation peak frequency shift, and the temperature and the parallel correlation peak frequency shift, respectively, comprises:

[0032] Fitting the plurality of designated blood pressure values ​​and the orthogonal correlation peak frequency shift corresponding to each designated blood pressure value to obtain a first fitting curve between blood pressure and orthogonal correlation peak frequency shift;

[0033] Fitting the plurality of designated temperature values ​​and the parallel correlation peak frequency shift corresponding to each designated temperature value to obtain a second fitting curve between temperature and parallel correlation peak frequency shift;

[0034] The first fitting curve and the second fitting curve constitute the corresponding relationship;

[0035] The actual blood pressure value and the actual temperature value at each of the measuring points are calculated based on the corresponding relationship and the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each of the measuring points calculated based on the frequency conversion detection result, including:

[0036] The actual blood pressure value at each of the measuring points is calculated based on the first fitting curve and the actual orthogonal correlation peak frequency shift of each of the measuring points calculated based on the frequency conversion detection result;

[0037] The actual temperature value at each of the measuring points is calculated based on the second fitting curve and the actual parallel correlation peak frequency shift of each of the measuring points calculated based on the variable frequency detection result.

[0038] In a second aspect, the present invention further provides a distributed sensing device based on photonic crystal fiber, the distributed sensing device comprising: a phase-sensitive optical time domain reflectometer, a distributed sensing structure and a data processor;

[0039] The pulse transmitting end of the phase-sensitive optical time-domain reflectometer is connected to the distributed sensing structure, and the data processor is connected to the data output interface of the phase-sensitive optical time-domain reflectometer;

[0040] The phase-sensitive optical time-domain reflectometer is used to emit detection light, receive orthogonally polarized back-Rayleigh scattered light signals transmitted in the distributed sensing structure, and convert the back-Rayleigh scattered light signals into electrical signals to obtain a set of orthogonal polarized back-Rayleigh scattered time-domain curves; the distributed sensing structure is a sensing structure with multiple measuring points formed by encapsulating photonic crystal optical fibers and arranging them in multiple blood vessels to be measured, and is used to excite orthogonally polarized back-Rayleigh scattered signals under the pulse action of the phase-sensitive optical time-domain reflectometer; the data processor is used to receive the orthogonal polarized back-Rayleigh scattered time-domain curve set, calculate the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each measuring point according to the orthogonal polarized back-Rayleigh scattered time-domain curve set, and the data processor stores the corresponding relationship between blood pressure and orthogonal correlation peak frequency shift, and temperature and parallel correlation peak frequency shift. The data processor is also used to calculate the actual blood pressure value and actual temperature value at each measuring point according to the corresponding relationship, the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift.

[0041] Preferably, the phase-sensitive optical time-domain reflectometer comprises:

[0042] Coherent optical lasers, electro-optic modulators, fiber gratings, semiconductor optical amplifiers, couplers, two-way polarization controllers, polarization combiners, time-delay optical fibers, arbitrary waveform generators, erbium-doped fiber amplifiers, bandpass filters, photodetectors, and circulators;

[0043] The coherent optical laser, the electro-optic modulator, the fiber grating, the semiconductor optical amplifier, and the coupler are connected in sequence, the coupler is respectively connected to the two polarization controllers, the coupler divides the pulse signal light output by the semiconductor optical amplifier into two paths, the two pulse signal lights are respectively connected to the polarization controllers, and one of them is introduced into the delay optical fiber, and then the two pulse signal lights are connected to the polarization combiner, the polarization combiner, the erbium-doped optical amplifier and the bandpass filter are connected in sequence, the arbitrary wave generator is respectively connected to the electro-optic modulator and the semiconductor optical amplifier, the first port of the circulator is connected to the bandpass filter, the second port of the circulator is connected to the distributed sensing structure as the pulse transmitting end of the phase-sensitive optical time domain reflectometer, and the third port of the circulator is connected to the photodetector; the photodetector is connected to the data processor as the data output interface of the phase-sensitive optical time domain reflectometer.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention provides a distributed sensing method based on photonic crystal fiber. First, by performing frequency conversion detection on photonic crystal fibers in different designated measurement groups, an orthogonal polarization back Rayleigh scattering time domain curve set corresponding to each designated measurement group is obtained, and the designated measurement group includes a designated blood pressure value and a designated temperature value; then, according to each orthogonal polarization back Rayleigh scattering time domain curve set, an orthogonal correlation peak frequency shift corresponding to each designated blood pressure value and a parallel correlation peak frequency shift corresponding to each designated temperature value are calculated, and corresponding relationships between blood pressure and orthogonal correlation peak frequency shift, and between temperature and parallel correlation peak frequency shift are established respectively; secondly, frequency conversion detection is performed on a distributed sensing structure, and the distributed sensing structure is a sensing structure with multiple measuring points formed by encapsulating photonic crystal fibers and arranging them in multiple blood vessels to be measured, and the actual blood pressure value and actual temperature value at each measuring point are calculated according to the corresponding relationship and the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each measuring point calculated according to the frequency conversion detection result. The present application utilizes the pressure-sensitive property of the birefringence of the orthogonal polarization mode excited in the photonic crystal fiber, and calculates the orthogonal correlation frequency shift corresponding to the birefringence under different blood pressure through the orthogonal back-Rayleigh time-domain scattering curve of the photonic crystal fiber, thereby obtaining the pressure on the photonic crystal fiber path, and realizing the distributed monitoring of the blood pressure on the blood vessel path where the optical fiber is laid. By utilizing the temperature-varying property of the effective refractive index of the two transmission modes of orthogonal polarization, the Rayleigh time-domain scattering curve of the same polarization mode collected at different temperatures is used to calculate the parallel correlation frequency shift corresponding to different temperature changes, thereby obtaining the temperature change on the optical fiber path, and realizing the distributed monitoring of the blood vessel temperature. The method provided in this embodiment effectively solves the defect that the traditional sensor based on the optical fiber probe and reflection principle can only realize single-point measurement, avoids the time and cost requirements brought by the need for multiple detections, and retains the high sensitivity response and high-precision measurement characteristics to changes in blood pressure and temperature, and can realize online distributed monitoring, greatly broadening the application capabilities of distributed sensing technology.

[0046] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 A flow chart of a photonic crystal fiber distributed sensing method provided by an embodiment of the present invention;

[0049] Figure 2 A schematic diagram of the structure of a photonic crystal fiber distributed sensing device provided in an embodiment of the present invention;

[0050] Figure 3 A schematic diagram of the structure of a phase-sensitive optical time-domain reflectometer in a device provided in an embodiment of the present invention;

[0051] Figure 4 A schematic diagram of the structure of a data processor in a device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention; the "and / or" keyword involved in this implementation represents both and, or. In other words, A and / or B mentioned in the embodiments of this specification represent both A and B, and A or B, and describe the three states of A and B. For example, A and / or B means: only A is included but not B; only B is included but not A; A and B are included.

[0053] Meanwhile, in the embodiments of this specification, when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a central component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time.

[0054] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0055] Before introducing the specific embodiments of the present application, it is necessary to supplement the following:

[0056] Since the existing vascular blood pressure sensors and human body temperature sensors in clinical practice are mainly based on optical fiber sensor probes and light reflection principles, these sensors can only perform single-point measurements. If multiple position information is required, multiple measurements need to be performed, and the problem of online measurement needs to be solved urgently. Phase-sensitive optical time-domain reflectometry has been widely used in distributed sensing technology due to its excellent sensing performance in distributed measurement. In distributed sensing, the length of each equivalent spatial resolution of the phase-sensitive optical time-domain reflectometer can be approximated to a single-point measurement, which can be equivalent to the sensing effect of a single optical fiber probe, and has the advantages of extremely high measurement accuracy and sensitivity, and has great potential in medical applications. In addition, since single-mode optical fiber is less sensitive to interference factors other than temperature and strain, the scope of application of phase-sensitive optical time-domain reflectometry is greatly limited. Special optical fiber has the advantage of being sensitive to certain specific parameters due to its special structure or material composition, which solves this pain point of ordinary single-mode optical fiber. In recent years, its application in distributed sensing technology has become increasingly abundant. Photonic crystal fiber is highly sensitive to transverse stress changes due to the microstructural characteristics of its cross section. Therefore, applying high-birefringence photonic crystal fiber to phase-sensitive optical time-domain reflectometry can effectively solve the problem of single-mode fiber's insufficient sensitivity to measurement parameters, while maintaining the advantage of single-mode fiber's sensitivity to temperature. The orthogonal polarization modes excited therein can simultaneously complete dual-parameter measurements of pressure and temperature changes, which is expected to solve the defects of current fiber-optic probe-based sensors.

[0057] Because the effective refractive index of different polarization modes of the photonic crystal fiber changes differently when it is subjected to pressure, it shows the difference in effective refractive index of different polarization modes, that is, the birefringence value is sensitive to the pressure, and the birefringence value can be calculated based on the orthogonal back-scattering curve set obtained by scanning the orthogonal polarization state mode of the photonic crystal fiber. According to this characteristic, the present application uses a fast-frequency phase-sensitive optical time-domain reflectometer to detect the birefringence of the photonic crystal fiber, thereby obtaining distributed pressure information on the optical fiber, reflecting the blood pressure at various locations on the blood vessels where the optical fiber is laid. The effective refractive indexes of the two polarization modes are both sensitive to temperature and have similar responses to temperature. Therefore, the peak frequency shift caused by temperature and pressure can be obtained by calculating the back-scattering curve set of the same polarization mode, and then the orthogonal peak frequency shift caused by the blood pressure change is subtracted from it, thereby obtaining the peak frequency shift corresponding to the temperature, reflecting the temperature change at various locations of the blood vessels.

[0058] Embodiment 1

[0059] See also Figure 1 Specifically, in the implementation of the photonic crystal fiber distributed sensing method, the method includes the following steps S110 to S130:

[0060] Step S110, performing frequency conversion detection on the photonic crystal optical fibers in different designated measurement groups to obtain a set of orthogonal polarization Rayleigh backscattering time domain curves corresponding to each designated measurement group, wherein the designated measurement group includes a designated blood pressure value and a designated temperature value;

[0061] Specifically, the present application places the same fiber position of the photonic crystal fiber to be measured under different designated measurement groups, so as to apply different temperatures and blood pressures to the same fiber position of the photonic crystal fiber.

[0062] In a possible implementation, the orthogonal polarization Rayleigh backscattering time domain curve set is a collection of Rayleigh backscattering signals in two orthogonal polarization directions varying with time, and the orthogonal polarization Rayleigh backscattering time domain curve set includes two orthogonal polarization Rayleigh backscattering time domain curves.

[0063] In a possible implementation, the above step S110 involves performing frequency conversion detection on the photonic crystal fibers in different designated measurement groups to obtain a set of orthogonal polarization backscattering time domain curves corresponding to each designated measurement group, specifically including the following sub-steps:

[0064] (a) Frequency modulating a frequency-stable coherent light source to generate a swept-frequency probe light with a periodically changing frequency;

[0065] Among them, the coherent light source can be a coherent optical laser, which uses a frequency-stable coherent optical laser to emit continuous light. The continuous light is frequency-modulated by an electro-optical modulator to form a double-sideband swept-frequency detection light with rapid frequency changes. Then, the double-sideband swept-frequency detection light can be filtered into a single-sideband detection light through a fiber grating.

[0066] (b) pulse modulating and polarization multiplexing the frequency-sweeping detection light and inputting it into the photonic crystal fiber in different designated measurement groups, thereby exciting orthogonally polarized back-scattered Rayleigh light signals associated with the orthogonal polarization transmission mode in the photonic crystal fiber;

[0067] Specifically, a single-sideband detection light is modulated into a pulse signal light by a semiconductor optical amplifier, the pulse signal light is divided into two paths by a coupler, and polarization controllers are respectively introduced into the two paths of pulse signal light to control the polarization states of the two paths of pulse signal light to be parallel to the two polarization axes of the photonic crystal fiber, a delay fiber is introduced into one of the two paths of pulse signal light so that the time domain signals finally detected by the two paths of pulse signal light do not overlap, the two paths of pulse signal light are combined by a polarization combiner and then injected into the photonic crystal fiber through a circulator to excite orthogonal polarization back-Rayleigh scattered light signals related to the orthogonal polarization transmission mode in the photonic crystal fiber, and the orthogonal polarization back-Rayleigh scattered light signals transmitted from the photonic crystal fiber received from the receiving end of the circulator are converted into electrical signals by a photodetector to obtain a set of orthogonal polarization back-Rayleigh scattered time domain curves corresponding to each specified measurement group.

[0068] (c) converting the backscattered Rayleigh light signal into an electrical signal to obtain a set of orthogonal polarization backscattered Rayleigh time domain curves corresponding to each specified measurement group.

[0069] Among them, the electro-optic modulator used for frequency modulation is driven by an arbitrary waveform generator. By inputting an electrical signal with a periodically and rapidly changing frequency into the arbitrary waveform generator, the electro-optic modulator can perform short-period frequency conversion modulation on the continuous light output by the coherent light laser, thereby generating a double-sideband swept-frequency detection light with a periodically changing frequency.

[0070] In this embodiment, the orthogonal polarization state modes of photonic crystal fibers are used for mixed detection of blood pressure and temperature. In a specific implementation, a high-birefringence photonic crystal fiber that can excite an orthogonal polarization state mode with a large effective refractive index difference is used as the optical fiber to be tested. Different polarization state modes transmitted in this type of optical fiber can show different effective refractive index changes when subjected to pressure, and reflect different birefringence sizes on the back Rayleigh time-domain scattering curve, so the method provided in this embodiment can be used to achieve pressure detection. In addition, the two polarization modes are respectively highly sensitive to temperature changes, and the effective refractive index changes of the same polarization mode can reflect temperature changes, so the method provided in this embodiment can also be used to achieve temperature detection.

[0071] Step S120, calculating the orthogonal correlation peak frequency shift corresponding to each specified blood pressure value and the parallel correlation peak frequency shift corresponding to each specified temperature value according to each orthogonal polarization backscattering time domain curve set, and establishing the corresponding relationship between the blood pressure and the orthogonal correlation peak frequency shift, and the temperature and the parallel correlation peak frequency shift respectively;

[0072] In the actual pressure detection scenario, it is not convenient to directly detect the size of birefringence. However, according to the compensation relationship between the effective refractive index difference of the orthogonal polarization mode transmitted in the photonic crystal fiber and the frequency change of the detection light, the compensation relationship between the effective refractive index difference and the detection light wavelength can be obtained. In actual implementation, the orthogonal correlation peak frequency shift used to compensate for the effective refractive index difference can be obtained by performing a two-dimensional cross-correlation operation based on the three-dimensional intensity spectrum of the orthogonal polarization back Rayleigh scattering time domain collected under variable frequency detection. In addition, the effective refractive index of the mode itself is directly affected by temperature changes, so the temperature change on the optical fiber can also be reflected by demodulating the effective refractive index difference of the two polarization modes at different temperatures. In actual implementation, the effective refractive index change during this period can be obtained by performing a two-dimensional cross-correlation operation on the three-dimensional spectrum of the back Rayleigh time domain scattering obtained under variable frequency detection using the same polarization transmission mode at different times. , So it reflects the size of the temperature change.

[0073] In the method provided in this embodiment, the orthogonal correlation peak frequency shift is used to reflect the birefringence magnitude, which directly represents the pressure magnitude, thereby converting the corresponding relationship between the pressure magnitude and the birefringence magnitude into the corresponding relationship between the pressure and the orthogonal correlation peak frequency shift. The relationship between the birefringence magnitude and the orthogonal correlation peak frequency shift can be expressed using the following formula:

[0074]

[0075] Among them, Δn xy is the difference in effective refractive index between two polarization modes, n x is the effective refractive index of the optical fiber x polarization axis, Δν xy is the orthogonal correlation peak frequency shift, ν0 is the center frequency of the detection light.

[0076] Apply different pressures to the optical fiber, obtain the magnitude of the orthogonal correlation peak frequency shift under each pressure, and establish a magnitude relationship between the pressure and the orthogonal correlation peak frequency shift.

[0077] In addition, in the method provided in this embodiment, the effective refractive index change of the same polarization mode is also reflected by the parallel correlation peak frequency shift, thereby reflecting the temperature change. The relationship between the effective refractive index change and the parallel correlation peak frequency shift can be expressed by the following formula:

[0078]

[0079] Among them, Δn aa is the difference in effective refractive index of the modes with the same polarization state a at different times, n a is the initial effective refractive index of the polarization axis of the a-fiber, Δν aais the parallel correlation peak frequency shift, ν0 is the center frequency of the detection light, and a refers to the x-polarization axis or the y-polarization axis.

[0080] The temperature of the optical fiber is changed, the magnitude of the parallel correlation peak frequency shift at each temperature compared to the initial temperature is obtained, and the magnitude relationship between the temperature magnitude and the parallel correlation peak frequency shift is established.

[0081] In a possible implementation, the step S120 involves calculating the orthogonal correlation peak frequency shift corresponding to each specified blood pressure value and the parallel correlation peak frequency shift corresponding to each specified temperature value based on each orthogonal polarization Rayleigh backscattering time domain curve set, and specifically includes the following sub-steps:

[0082] (1) Combining the orthogonal polarization Rayleigh backscattering time domain curve set into a three-dimensional intensity spectrum set of orthogonal polarization Rayleigh backscattering whose intensity varies with the fiber position and frequency;

[0083] The orthogonal polarization Rayleigh backscattering three-dimensional intensity spectrum set includes two orthogonal polarization Rayleigh backscattering three-dimensional intensity spectra;

[0084] (2) performing a two-dimensional cross-correlation operation on the three-dimensional intensity spectrum set of the orthogonal polarization backscattering Rayleigh time-domain scattering to obtain an orthogonal correlation peak frequency shift corresponding to a specified blood pressure value in each specified measurement group for compensating for the effective refractive index difference;

[0085] In a possible implementation, the calculation formula for performing a two-dimensional cross-correlation operation on the three-dimensional intensity spectrum set of orthogonal polarization backward Rayleigh time-domain scattering involved in the sub-step (2) of the above step S120 is:

[0086] F xy (z) = argmax(correlation(I x (f,z),I y (f,z));

[0087] Among them, F xy (z) is the orthogonal correlation peak frequency shift distributed along the optical fiber position z, where the optical fiber position corresponds to the time axis; x (f,z) represents the three-dimensional intensity spectrum of the backward Rayleigh time-domain scattering corresponding to the polarization state in the x-polarization direction; I y (f,z) represents the three-dimensional intensity spectrum of the backscattered Rayleigh time-domain scattering corresponding to the polarization state in the y polarization direction; correlation is the calculation symbol of the correlation coefficient, and argmax is the frequency corresponding to the position with the maximum correlation coefficient.

[0088] That is, by performing a two-dimensional cross-correlation operation on the three-dimensional intensity spectrum set of orthogonal polarization backscattering Rayleigh time domain scattering, the distribution of the orthogonal correlation peak frequency shift at the optical fiber position can be obtained, that is, the blood pressure at different blood vessel positions. The orthogonal correlation peak frequency shift is calculated using the following formula:

[0089] F xy (z) = argmax(correlation(I x (f,z),I y (f,z)).

[0090] In a possible implementation, calculating the orthogonal correlation peak frequency shift of the corresponding designated blood pressure value and the parallel correlation peak frequency shift of the corresponding designated temperature value according to the orthogonal polarization Rayleigh backscattering time domain curve set also includes:

[0091] A designated measurement group is randomly selected from a plurality of designated measurement groups as a reference measurement group, two orthogonally polarized Rayleigh time-domain scattering three-dimensional intensity spectra of the reference measurement group are used as reference intensity spectra, and two orthogonally polarized Rayleigh time-domain scattering three-dimensional intensity spectra corresponding to any designated measurement group different from the reference measurement group are used as measurement intensity spectra;

[0092] Perform a two-dimensional cross-correlation operation on each measured intensity spectrum and a three-dimensional intensity spectrum of backscattered Rayleigh time-domain scattering having the same polarization state in the reference intensity spectrum, obtain a correlation characteristic curve based on the x polarization direction and a correlation characteristic curve based on the y polarization direction of the measured intensity spectrum and the reference intensity spectrum, respectively, obtain the maximum values ​​of the two correlation characteristic curves and perform an average operation, and obtain a parallel correlation comprehensive peak frequency shift;

[0093] The change value of the orthogonal correlation peak frequency shift of the measured intensity spectrum and the reference intensity spectrum is calculated, and the change value is subtracted from the parallel correlation comprehensive peak frequency shift to obtain the parallel correlation peak frequency shift of the specified temperature value corresponding to the measured intensity spectrum.

[0094] In a possible implementation manner, the calculation formula involved in the parallel correlation peak frequency shift includes:

[0095] F xx (z) = argmax(correlation(I refx (f,z),I x (f,z));

[0096] F yy (z) = argmax(correlation(I refy (f,z),I y (f,z));

[0097] F(z)=(F xx (z)+Fyy (z)) / 2-ΔF xy ;

[0098] Among them, F xx (z) represents the parallel correlation peak frequency shift corresponding to the polarization state in the x-polarization direction distributed along the optical fiber position z; F yy (z) represents the parallel correlation peak frequency shift corresponding to the polarization state in the y polarization direction distributed along the optical fiber position z; refx (f,z) represents the reference intensity spectrum corresponding to the polarization state in the x-polarization direction; I refy (f,z) represents the reference intensity spectrum corresponding to the polarization state in the y polarization direction; I x (f,z) represents the measured intensity spectrum corresponding to the polarization state in the x-polarization direction; I y (f,z) represents the measured intensity spectrum corresponding to the polarization state in the y polarization direction; ΔF xy It represents the change in the orthogonal correlation peak frequency shift between the measured intensity spectrum and the reference intensity spectrum; F(z) represents the parallel correlation peak frequency shift distributed along the optical fiber position z; correlation represents the calculation sign of the correlation coefficient, and argmax represents the sign of the frequency corresponding to the position with the maximum correlation coefficient.

[0099] Among them, the parallel correlation comprehensive peak frequency shift is (F xx (z)+F yy (z)) / 2, F(z) is the parallel correlation peak frequency shift for a specified temperature value corresponding to the measured intensity spectrum.

[0100] Calculation of ΔF xy When , the orthogonal correlation peak frequency shifts of the measured intensity spectrum and the reference intensity spectrum can be calculated respectively by the calculation formula of the orthogonal correlation peak frequency shift, and the difference between the two is the change value of the orthogonal correlation peak frequency shift of the measured intensity spectrum and the reference intensity spectrum.

[0101] It can be understood that z in the above calculation formula is the time axis, and can also be equivalent to the optical fiber position. That is, by obtaining the optical fiber position of the photonic crystal fiber where the specified blood pressure value and the specified temperature value are measured, the specific sizes of the orthogonal correlation peak frequency shift and the parallel correlation peak frequency shift at the corresponding measurement position can be obtained.

[0102] In a possible implementation, the corresponding relationships between blood pressure and orthogonal correlation peak frequency shift, and between temperature and parallel correlation peak frequency shift are established, including:

[0103] Fitting a plurality of designated blood pressure values ​​and an orthogonal correlation peak frequency shift corresponding to each designated blood pressure value to obtain a first fitting curve between the blood pressure and the orthogonal correlation peak frequency shift;

[0104] Fitting a plurality of designated temperature values ​​and the parallel correlation peak frequency shift corresponding to each designated temperature value to obtain a second fitting curve between temperature and the parallel correlation peak frequency shift;

[0105] The first fitting curve and the second fitting curve form a corresponding relationship;

[0106] The actual blood pressure value and the actual temperature value at each measuring point are calculated based on the corresponding relationship and the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each measuring point calculated based on the frequency conversion detection result, including:

[0107] The actual blood pressure value at each measuring point is calculated based on the first fitting curve and the actual orthogonal correlation peak frequency shift of each measuring point calculated based on the frequency conversion detection result;

[0108] The actual temperature value at each measuring point is calculated based on the second fitting curve and the actual parallel correlation peak frequency shift of each measuring point calculated based on the variable frequency detection result.

[0109] After calculating the orthogonal and parallel correlation peak frequency shifts, the orthogonal peak frequency shifts at each pressure can be fitted according to step 102, and the fitting results can be used as the corresponding relationship between the orthogonal peak frequency shift and the pressure, and the parallel peak frequency shifts under different temperature changes can be fitted to obtain the sensitivity of the parallel peak frequency shift to the temperature change; or according to step 103, the pressure and temperature changes corresponding to the orthogonal and parallel correlation peak frequency shifts can be obtained by using the obtained corresponding relationship between the orthogonal peak frequency shift and the pressure and the sensitivity of the parallel peak frequency shift to the temperature change, as the actually detected pressure and temperature change values.

[0110] The distributed sensing method of blood vessel blood pressure and temperature based on photonic crystal fiber provided in this embodiment is based on photonic crystal fiber and phase-sensitive optical time domain reflection that can stimulate different polarization modes with high birefringence for distributed sensing, and utilizes the characteristics that the birefringence size in the photonic crystal fiber is sensitive to pressure and the transmission mode is sensitive to temperature, thereby realizing the distributed sensing method of blood vessel blood pressure and temperature based on photonic crystal fiber. It can be foreseen that the method proposed in this embodiment will play a huge role in the simultaneous monitoring of blood vessel blood pressure and temperature in actual medical applications and other pressure and temperature measurement applications.

[0111] Step S130, performing frequency conversion detection on the distributed sensing structure. The distributed sensing structure is a sensing structure with multiple measuring points formed by encapsulating photonic crystal optical fibers and arranging them in multiple blood vessels to be measured. The actual blood pressure value and actual temperature value at each measuring point are calculated based on the corresponding relationship and the actual orthogonal correlation peak frequency shift and actual parallel correlation peak frequency shift of each measuring point calculated based on the frequency conversion detection result.

[0112] After respectively obtaining the relationship between the orthogonal correlation peak frequency shift and pressure and the relationship between the parallel correlation peak frequency shift and temperature, the photonic crystal fiber to be measured can be arranged in multiple blood vessels to be monitored, and the photonic crystal fiber to be measured can be actually detected.

[0113] It can be understood that after the orthogonal polarization backscattering time domain signal set is obtained by frequency conversion detection in the distributed sensing structure, it can be processed through the calculation step of the above step 120, that is, the detected backscattering three-dimensional intensity spectrum set of the orthogonal polarization state of the photonic crystal fiber to be measured is demodulated by two-dimensional cross-correlation operation, and after the orthogonal correlation peak frequency shift and the parallel correlation peak frequency shift are obtained respectively, the actual pressure magnitude and temperature distribution at each measuring point of the measured distributed sensing structure can be calculated through the corresponding relationship between the orthogonal correlation peak frequency shift and the pressure and the corresponding relationship between the parallel correlation peak frequency shift and the temperature obtained in step 102. Among them, the measuring point is the corresponding layout position of each blood vessel to be measured.

[0114] After steps 110 to 130 provided in this embodiment, distributed high-sensitivity simultaneous monitoring of blood vessel pressure and temperature can be completed through photonic crystal optical fiber.

[0115] In summary, an embodiment of the present invention provides a distributed sensing method based on photonic crystal fiber. First, by performing frequency conversion detection on the photonic crystal fiber in different designated measurement groups, a set of orthogonal polarization back Rayleigh scattering time domain curves corresponding to each designated measurement group is obtained, and the designated measurement group includes a designated blood pressure value and a designated temperature value; then, the orthogonal correlation peak frequency shift corresponding to each designated blood pressure value and the parallel correlation peak frequency shift corresponding to each designated temperature value are calculated according to each orthogonal polarization back Rayleigh scattering time domain curve set, and the corresponding relationship between the blood pressure and the orthogonal correlation peak frequency shift, and the temperature and the parallel correlation peak frequency shift are established respectively; secondly, frequency conversion detection is performed on the distributed sensing structure, which is a sensing structure with multiple measuring points formed by encapsulating the photonic crystal fiber and arranging it in multiple blood vessels to be measured, and the actual blood pressure value and the actual temperature value at each measuring point are calculated according to the corresponding relationship and the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each measuring point calculated according to the frequency conversion detection result. The embodiment of the present application utilizes the pressure-sensitive property of the birefringence size of the orthogonal polarization mode excited in the photonic crystal fiber, and calculates the orthogonal correlation frequency shift size corresponding to the birefringence size under different blood pressure sizes through the orthogonal back-to-back Rayleigh time-domain scattering curve of the photonic crystal fiber, thereby obtaining the pressure size on the photonic crystal fiber path, and realizing the distributed monitoring of the blood pressure on the blood vessel path where the optical fiber is laid. Utilizing the effective refractive index of the two transmission modes of orthogonal polarization that changes with temperature, the Rayleigh time-domain scattering curves of the same polarization mode collected at different temperatures are used to calculate the parallel correlation frequency shift size corresponding to different temperature changes, thereby obtaining the temperature change on the optical fiber path, and realizing the distributed monitoring of the blood vessel temperature. The method provided in this embodiment effectively solves the defect that the traditional sensor based on the optical fiber probe and reflection principle can only realize single-point measurement, avoids the time and cost requirements brought by the need for multiple detections, and retains the high sensitivity response and high-precision measurement characteristics to changes in blood pressure and temperature, and can realize online distributed monitoring, greatly broadening the application capabilities of distributed sensing technology.

[0116] Embodiment 2

[0117] On the basis of the photonic crystal fiber distributed sensing method provided in the first embodiment above, the present invention further provides a photonic crystal fiber distributed sensing device that can be used to implement the above method.

[0118] See also Figure 2 , Figure 2Schematic diagram of the device architecture of an embodiment of the present invention. Specifically, the photonic crystal fiber-based distributed sensing device is used to sense and monitor blood pressure and temperature on the optical fiber layout path, and specifically includes: a phase-sensitive optical time domain reflectometer, a distributed sensing structure and a data processor; the pulse transmitting end of the phase-sensitive optical time domain reflectometer is connected to the distributed sensing structure, and the data processor is connected to the data output interface of the phase-sensitive optical time domain reflectometer;

[0119] Among them, the phase-sensitive optical time-domain reflectometer is used to emit detection light, receive orthogonally polarized back-Rayleigh scattered light signals transmitted in the distributed sensing structure, and convert the back-Rayleigh scattered light signals into electrical signals to obtain an orthogonal polarization back-Rayleigh scattering time-domain curve set; the distributed sensing structure is a sensing structure with multiple measuring points formed by encapsulating photonic crystal optical fibers and arranging them in multiple blood vessels to be measured, and is used to excite orthogonally polarized back-Rayleigh scattered signals under the pulse action of the phase-sensitive optical time-domain reflectometer; the data processor is used to receive the orthogonal polarization back-Rayleigh scattering time-domain curve set, calculate the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each measuring point based on the orthogonal polarization back-Rayleigh scattering time-domain curve set, and the corresponding relationship between blood pressure and orthogonal correlation peak frequency shift, and temperature and parallel correlation peak frequency shift stored in the data processor. The data processor is also used to calculate the actual blood pressure value and actual temperature value at each measuring point based on the corresponding relationship, the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift.

[0120] like Figure 3 As shown, in a possible implementation, the phase-sensitive optical time-domain reflectometer includes:

[0121] Coherent laser (LD), electro-optic modulator (EOM), fiber Bragg grating, semiconductor optical amplifier (SOA), coupler, two-way polarization controller, polarization beam combiner (PBC), delay fiber, arbitrary waveform generator (AWG), erbium-doped fiber amplifier (EDFA), bandpass filter (BPF), photodetector (PD) and circulator;

[0122] Among them, a coherent optical laser, an electro-optic modulator, a fiber grating, a semiconductor optical amplifier, and a coupler are connected in sequence, the coupler is connected to two polarization controllers respectively, the coupler divides the pulse signal light output by the semiconductor optical amplifier into two paths, the two pulse signal lights are connected to the polarization controllers respectively, and one of them introduces a delay optical fiber, and then the two pulse signal lights are connected to a polarization combiner, the polarization combiner, the erbium-doped optical amplifier and the bandpass filter are connected in sequence, the arbitrary wave generator is connected to the electro-optic modulator and the semiconductor optical amplifier respectively, the first port of the circulator is connected to the bandpass filter, the second port of the circulator is connected to the distributed sensing structure as the pulse transmitting end of the phase-sensitive optical time domain reflectometer, and the third port of the circulator is connected to the photodetector; the photodetector is connected to the data processor as the data output interface of the phase-sensitive optical time domain reflectometer.

[0123] Specifically, a coherent optical laser is used to output continuous light with stable frequency; an electro-optical modulator is used to frequency-modulate the continuous light to form a double-sideband detection light with rapid frequency change; a fiber grating is used to filter the double-sideband detection light into a single-sideband detection light; a semiconductor optical amplifier is used to modulate the single-sideband detection light into a pulse signal light; a coupler is used to divide the pulse signal light into two paths; two polarization controllers are used to control the polarization states of the two pulse signal lights to be parallel to the two orthogonal polarization axes of the photonic crystal fiber; a delay fiber is used to delay one of the two pulse signal lights to prevent the scattering signals of the two orthogonal polarization states from overlapping; a polarization combiner is used to combine the pulse signal lights of the two orthogonal polarization states; an erbium-doped The optical amplifier is used to amplify the combined pulse signal light; the bandpass filter is used to filter out the spontaneous radiation noise in the combined and amplified pulse signal light to form the detection light; the circulator is used to guide the optical path direction of the detection light and the back Rayleigh scattered light signal to inject the detection light into the distributed sensing structure and stimulate the orthogonal polarization back Rayleigh scattered light signal related to the orthogonal polarization transmission mode in the photonic crystal fiber; the arbitrary wave generator is used to control the electro-optic modulator and the semiconductor optical amplifier; the photodetector is used to convert the orthogonal polarization back Rayleigh scattered light signal transmitted from the photonic crystal fiber received from the receiving end of the circulator into an electrical signal to obtain a set of orthogonal polarization back Rayleigh scattered time domain curves.

[0124] The data processor includes one or more processors and a memory. Figure 4 A processor is taken as an example.

[0125] The processor and the memory may be connected via a bus or other means. Figure 4 The example of connecting through bus is taken in the following.

[0126] As a non-volatile computer-readable storage medium, the memory can be used to store non-volatile software programs, non-volatile computer executable programs and modules, such as the corresponding relationship between the blood pressure and the orthogonal correlation peak frequency shift, the temperature and the parallel correlation peak frequency shift calculated in the distributed pressure sensing method based on photonic crystal fiber in Example 1, and the calculation process of the orthogonal correlation peak frequency shift and the parallel correlation peak frequency shift. The processor executes various functional applications and data processing of the distributed pressure sensing device based on photonic crystal fiber by running the non-volatile software programs, instructions and modules stored in the memory, that is, realizes part of the content involved in the distributed sensing method based on photonic crystal fiber in Example 1.

[0127] The memory may include a high-speed random access memory and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0128] The program instructions / modules are stored in the memory, and when executed by one or more processors, the relevant contents of the photonic crystal fiber distributed sensing method in the above embodiment 1 are executed, for example, the above described Figure 1 The corresponding steps are shown.

[0129] An embodiment of the present invention further provides a non-volatile computer storage medium, wherein the computer storage medium stores computer executable instructions, and the computer executable instructions are executed by one or more processors, such as Figure 4 A processor in can enable the above one or more processors to execute the photonic crystal fiber distributed sensing method in embodiment 1, for example, to execute the above described Figure 1 The corresponding steps are shown.

[0130] It is worth noting that the information interaction, execution process, etc. between the modules and units within the above-mentioned devices and systems are based on the same concept as the processing method embodiment of the present invention. The specific contents can be found in the description of the method embodiment of the present invention and will not be repeated here.

[0131] A person skilled in the art may understand that all or part of the steps in the various methods of the embodiments may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, and the storage medium may include: a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, etc.

[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A distributed sensing method based on photonic crystal fiber, characterized in that: The method comprises: Performing frequency conversion detection on the photonic crystal optical fiber in different designated measurement groups to obtain a set of orthogonal polarization back Rayleigh scattering time domain curves corresponding to each designated measurement group, wherein the designated measurement group includes a designated blood pressure value and a designated temperature value; Calculating the orthogonal correlation peak frequency shift corresponding to each of the specified blood pressure values ​​and the parallel correlation peak frequency shift corresponding to each of the specified temperature values ​​according to each of the orthogonal polarization Rayleigh backscattering time domain curve sets, and establishing the corresponding relationships between the blood pressure and the orthogonal correlation peak frequency shift, and between the temperature and the parallel correlation peak frequency shift; The distributed sensing structure is subjected to frequency conversion detection. The distributed sensing structure is a sensing structure with multiple measuring points formed by encapsulating the photonic crystal optical fiber and arranging it in multiple blood vessels to be measured. The actual blood pressure value and the actual temperature value at each measuring point are calculated based on the corresponding relationship and the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each measuring point calculated based on the frequency conversion detection result.

2. The distributed sensing method based on photonic crystal fiber according to claim 1, characterized in that: The orthogonal polarization Rayleigh backscattering time domain curve set includes two orthogonal polarization Rayleigh backscattering time domain curves.

3. The distributed sensing method based on photonic crystal fiber according to claim 2, characterized in that: The method of performing frequency conversion detection on the photonic crystal optical fibers in different designated measurement groups to obtain a set of orthogonal polarization backscattering time domain curves corresponding to each designated measurement group includes: Frequency modulation is performed on a coherent light source with stable frequency to generate a swept frequency detection light with periodically changing frequency; The frequency sweep detection light is pulse modulated and polarization multiplexed, and then input into the photonic crystal optical fiber in different designated measurement groups, so as to excite orthogonally polarized back-scattered Rayleigh light signals related to the orthogonal polarization transmission mode in the photonic crystal optical fiber; The back-scattered Rayleigh light signal is converted into an electrical signal to obtain a set of orthogonal polarization back-scattered Rayleigh time domain curves corresponding to each designated measurement group.

4. The distributed sensing method based on photonic crystal fiber according to claim 1, characterized in that: The calculating, based on each of the orthogonal polarization Rayleigh backscattering time domain curve sets, an orthogonal correlation peak frequency shift corresponding to each of the specified blood pressure values ​​and a parallel correlation peak frequency shift corresponding to each of the specified temperature values ​​comprises: Combining the orthogonal polarization Rayleigh backscattering time domain curve sets into a three-dimensional intensity spectrum set of orthogonal polarization Rayleigh backscattering time domain scattering whose intensity varies with optical fiber position and frequency; Performing a two-dimensional cross-correlation operation on the orthogonal polarization backscattered Rayleigh time-domain scattering three-dimensional intensity spectrum set to obtain an orthogonal correlation peak frequency shift corresponding to the specified blood pressure value in each of the specified measurement groups; The orthogonal polarization Rayleigh backscattering three-dimensional intensity spectrum set includes two orthogonal polarization Rayleigh backscattering three-dimensional intensity spectra.

5. The distributed sensing method based on photonic crystal fiber according to claim 4, characterized in that: The calculation formula for performing a two-dimensional cross-correlation operation on the three-dimensional intensity spectrum set of the orthogonal polarization backscattering Rayleigh time-domain scattering is: F xy (z)=argmax(correlation(I x (f,z),I y (f,z)); Among them, F xy (z) is the orthogonal correlation peak frequency shift distributed along the optical fiber position z, and the optical fiber position corresponds to the time axis; x (f,z) represents the three-dimensional intensity spectrum of the backscattered Rayleigh time domain scattering corresponding to the polarization state in the x polarization direction; I y (f,z) represents the three-dimensional intensity spectrum of the back Rayleigh time-domain scattering corresponding to the polarization state in the y polarization direction; correlation is the calculation symbol of the correlation coefficient, and argmax is the frequency of the corresponding position where the correlation coefficient is maximized.

6. The distributed sensing method based on photonic crystal fiber according to claim 5, characterized in that: The calculating of the orthogonal correlation peak frequency shift of the corresponding designated blood pressure value and the parallel correlation peak frequency shift of the corresponding designated temperature value according to the orthogonal polarization Rayleigh backscattering time domain curve set also includes: Randomly select a designated measurement group from the plurality of designated measurement groups as a reference measurement group, use two orthogonally polarized Rayleigh time-domain scattering three-dimensional intensity spectra of the reference measurement group as a reference intensity spectrum, and use two orthogonally polarized Rayleigh time-domain scattering three-dimensional intensity spectra corresponding to any designated measurement group different from the reference measurement group as a measurement intensity spectrum; Perform a two-dimensional cross-correlation operation on each of the measured intensity spectra and the back Rayleigh time-domain scattering three-dimensional intensity spectrum having the same polarization state in the reference intensity spectrum, to obtain a correlation characteristic curve based on the x polarization direction and a correlation characteristic curve based on the y polarization direction of the measured intensity spectrum and the reference intensity spectrum, respectively, obtain the maximum values ​​of the two correlation characteristic curves and perform an average operation to obtain a parallel correlation comprehensive peak frequency shift; The change value of the orthogonal correlation peak frequency shift of the measured intensity spectrum and the reference intensity spectrum is calculated, and the change value is subtracted from the parallel correlation comprehensive peak frequency shift to obtain the parallel correlation peak frequency shift of the specified temperature value corresponding to the measured intensity spectrum.

7. The distributed sensing method based on photonic crystal fiber according to claim 6 is characterized in that , the calculation formula involved in the parallel correlation peak frequency shift includes: F xx (z)=argmax(correlation(I refx (f,z),I x (f,z)); F yy (z)=argmax(correlation(I refy (f,z),I y (f,z)); F(z)=(F xx (z)+F yy (z)) / 2-ΔF xy ; Among them, F xx (z) represents the parallel correlation peak frequency shift corresponding to the polarization state in the x-polarization direction distributed along the optical fiber position z; F yy (z) represents the parallel correlation peak frequency shift corresponding to the polarization state in the y polarization direction distributed along the optical fiber position z; refx (f,z) represents the reference intensity spectrum corresponding to the polarization state in the x polarization direction; I refy (f,z) represents the reference intensity spectrum corresponding to the polarization state in the y polarization direction; x (f,z) represents the measured intensity spectrum corresponding to the polarization state in the x polarization direction; I y (f,z) represents the measured intensity spectrum corresponding to the polarization state in the y polarization direction; ΔF xy represents the change value of the orthogonal correlation peak frequency shift between the measured intensity spectrum and the reference intensity spectrum; F(z) represents the parallel correlation peak frequency shift distributed along the optical fiber position z.

8. The distributed sensing method based on photonic crystal fiber according to claim 1, characterized in that: The corresponding relationships between blood pressure and orthogonal correlation peak frequency shift, and between temperature and parallel correlation peak frequency shift are respectively established, including: Fitting the plurality of designated blood pressure values ​​and the orthogonal correlation peak frequency shift corresponding to each designated blood pressure value to obtain a first fitting curve between blood pressure and orthogonal correlation peak frequency shift; Fitting the plurality of designated temperature values ​​and the parallel correlation peak frequency shift corresponding to each designated temperature value to obtain a second fitting curve between temperature and parallel correlation peak frequency shift; The first fitting curve and the second fitting curve constitute the corresponding relationship; The actual blood pressure value and the actual temperature value at each of the measuring points are calculated based on the corresponding relationship and the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each of the measuring points calculated based on the frequency conversion detection result, including: The actual blood pressure value at each of the measuring points is calculated based on the first fitting curve and the actual orthogonal correlation peak frequency shift of each of the measuring points calculated based on the frequency conversion detection result; The actual temperature value at each of the measuring points is calculated based on the second fitting curve and the actual parallel correlation peak frequency shift of each of the measuring points calculated based on the variable frequency detection result.

9. A distributed sensing device based on photonic crystal fiber, characterized in that: The distributed sensing device comprises: Phase-sensitive optical time-domain reflectometer, distributed sensing structure and data processor; The pulse transmitting end of the phase-sensitive optical time-domain reflectometer is connected to the distributed sensing structure, and the data processor is connected to the data output interface of the phase-sensitive optical time-domain reflectometer; Among them, the phase-sensitive optical time-domain reflectometer is used to emit detection light, receive orthogonally polarized back-Rayleigh scattered light signals transmitted in the distributed sensing structure, and convert the back-Rayleigh scattered light signals into electrical signals to obtain an orthogonal polarization back-Rayleigh scattering time-domain curve set; the distributed sensing structure is a sensing structure with multiple measuring points formed by encapsulating photonic crystal optical fibers and arranging them in multiple blood vessels to be measured, and is used to excite orthogonally polarized back-Rayleigh scattered signals under the pulse action of the phase-sensitive optical time-domain reflectometer; the data processor is used to receive the orthogonal polarization back-Rayleigh scattering time-domain curve set, and calculate the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift of each of the measuring points based on the orthogonal polarization back-Rayleigh scattering time-domain curve set. The data processor stores the corresponding relationship between blood pressure and orthogonal correlation peak frequency shift, and between temperature and parallel correlation peak frequency shift. The data processor is also used to calculate the actual blood pressure value and the actual temperature value at each of the measuring points based on the corresponding relationship, the actual orthogonal correlation peak frequency shift and the actual parallel correlation peak frequency shift.

10. The photonic crystal fiber-based distributed sensing device according to claim 9, characterized in that: The phase-sensitive optical time-domain reflectometer comprises: Coherent optical lasers, electro-optic modulators, fiber gratings, semiconductor optical amplifiers, couplers, two-way polarization controllers, polarization combiners, time-delay optical fibers, arbitrary waveform generators, erbium-doped fiber amplifiers, bandpass filters, photodetectors, and circulators; The coherent optical laser, the electro-optic modulator, the fiber grating, the semiconductor optical amplifier, and the coupler are connected in sequence, the coupler is respectively connected to the two polarization controllers, the coupler divides the pulse signal light output by the semiconductor optical amplifier into two paths, the two pulse signal lights are respectively connected to the polarization controllers, and one of them is introduced into the delay optical fiber, and then the two pulse signal lights are connected to the polarization combiner, the polarization combiner, the erbium-doped optical amplifier and the bandpass filter are connected in sequence, the arbitrary wave generator is respectively connected to the electro-optic modulator and the semiconductor optical amplifier, the first port of the circulator is connected to the bandpass filter, the second port of the circulator is connected to the distributed sensing structure as the pulse transmitting end of the phase-sensitive optical time domain reflectometer, and the third port of the circulator is connected to the photodetector; the photodetector is connected to the data processor as the data output interface of the phase-sensitive optical time domain reflectometer.

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