Fiber grating sensor multiplexing device and method based on photon lantern mode diversity

Abstract

The application provides a kind of fiber grating sensing multiplexing device based on photon lantern mode diversity, wide spectrum probe light is generated by wide spectrum light source output module, simultaneously has base mode and high order space mode by the eccentricity fusion high order space mode excitation module, and after being separated by spatial mode conversion separation and multiplexing module, multiple paths carried by base mode are obtained, enter the topology module of multiple paths space mode Bragg fiber grating reflection, form multiple paths fiber grating reflection spectrum carried by base mode and carrying monitoring data, when spatial mode conversion separation and multiplexing module multiplexes multiple paths grating reflection spectrum into a path to be measured spectrum with monitoring data, by multiple paths space mode reflection spectrum processing module demodulation analysis, monitoring data synchronous detection and analysis are realized. By implementing the application, the problems of insufficient multiplexing capacity, low reliability, high cost, synchronous detection positioning and the like of the existing fiber grating sensing multiplexing device can be solved.

Description

Technical Field

[0001] This invention relates to the field of fiber optic grating sensing multiplexing technology, and in particular to a fiber optic grating sensing multiplexing device and method based on photonic lantern mode diversity. Background Technology

[0002] Compared to traditional piezoelectric ceramic sensors on the market, fiber optic sensors have advantages such as long-distance monitoring, multiplexing, high sensitivity and high resolution, immunity to electromagnetic interference, and strong long-term stability. They have great development potential in fields such as national defense, power, oil and gas resources, intelligent transportation, construction, and medicine.

[0003] Fiber optic sensors are divided into point-type fiber optic sensors and long-range distributed fiber optic sensors. Point-type fiber optic sensors can accurately sense the monitored object, but the number of sensing points is limited. Long-range distributed fiber optic sensors have a long sensing distance and are suitable for long-distance online monitoring, but their measurement accuracy is low, making it difficult to accurately determine the actual situation in complex working environments. With the increasing size of monitoring equipment and the demand for long-distance sensing, single-point fiber optic sensing technology is far from meeting the detection needs of large spatial areas. Therefore, multi-point multiplexing high-precision sensing technology is particularly important.

[0004] Currently, point-type fiber Bragg gratings (FBGs) are recognized in the industry as the most diverse, commercially viable, and widely used type of fiber optic sensing technology. To achieve high-precision multi-point measurements, various multiplexing techniques have been proposed, such as wavelength division multiplexing (WDM), time division multiplexing (TDM), and spatial division multiplexing (SDM). WDM technology connects multiple fiber Bragg gratings (FBGs) with different center wavelengths in series in the same optical path to achieve multiplexed sensing. However, each FBG requires an independent wavelength range to reduce overlap between adjacent FBGs, thus limiting the number of sensors to the light source bandwidth and preventing large-scale sensor multiplexing. Furthermore, the serial topology has low reliability; if one FBG fails, the network following it becomes paralyzed, reducing the reliability of the multiplexed sensing system. TDM separates the fiber Bragg grating reflection spectrum signals using time-domain separation, multiplexing FBG sensors with the same or different center reflection wavelengths into the same FBG sensing system. However, it cannot achieve synchronous detection by multiple sensors for accurate fault location. SDM technology solves the crosstalk problem between multiple FBGs connected in series in a single fiber by distributing multiple FBGs to different spatial optical paths. However, the SDM structure requires optical switching devices to allocate transmission channels. On the one hand, the multiplexing capacity is limited by the number of optical switching channels; on the other hand, it cannot achieve synchronous detection by multiple sensors for accurate fault location, and the system is complex and costly.

[0005] Therefore, it is necessary to conduct research on novel mode-multiplexed fiber Bragg grating sensing topologies to realize a high-capacity, high-precision, high-reliability, and low-cost fiber Bragg grating sensing multiplexing device based on the spatial mode dimension, thereby solving the problems of insufficient multiplexing capability, low reliability, high cost, and synchronous detection and positioning of existing fiber Bragg grating sensing multiplexing devices. Summary of the Invention

[0006] The technical problem to be solved by the embodiments of the present invention is to provide a fiber Bragg grating sensing multiplexing device and method based on photonic lantern mode diversity, which can solve the problems of insufficient multiplexing capability, low reliability, high cost, and synchronous detection and positioning of existing fiber Bragg grating sensing multiplexing devices.

[0007] To address the aforementioned technical problems, embodiments of the present invention provide a fiber grating sensing multiplexing device based on photonic lantern mode diversity, comprising a broadband light source output module, an off-core fusion splicing higher-order spatial mode excitation module, a spatial mode conversion, separation, and multiplexing module, and a multi-path spatial mode Bragg fiber grating topology module connected in sequence, as well as a multi-path spatial mode reflectance spectral processing module connected to the off-core fusion splicing higher-order spatial mode excitation module; wherein...

[0008] The broadband light source output module is used to generate stable and power-adjustable broadband probe light;

[0009] The eccentric fusion higher-order spatial mode excitation module and the broadband light source output module are connected by an optical fiber eccentric fusion method. The module is used to excite the broadband probe light through eccentric fusion to form a signal carrying both the fundamental mode and a higher-order spatial mode, and inject it into the spatial mode conversion, separation and multiplexing module. The module also receives the spectrum to be measured fed back from the spatial mode conversion, separation and multiplexing module and injects it into the multi-channel spatial mode reflectance spectrum processing module.

[0010] The spatial mode conversion separation and multiplexing module is used to demultiplex and separate the broadband probe light that carries both fundamental mode and higher-order spatial mode, to obtain a multi-path grating incident spectrum carried by the fundamental mode, and inject it into the multi-path spatial mode Bragg fiber grating topology module; and to multiplex the multi-path grating reflection spectrum carried by the fundamental mode and carrying relevant monitoring data fed back from the multi-path spatial mode Bragg fiber grating topology module, to obtain a single reflection spectrum that carries both fundamental mode and higher-order spatial mode and carries all monitoring data, and to feed this reflection spectrum back as the spectrum to be measured to the off-core fusion higher-order spatial mode excitation module;

[0011] The multi-path spatial mode Bragg fiber grating topology module is used to form a corresponding grating reflection spectrum carried by the fundamental mode when irradiated by the incident spectrum of multiple gratings carried by the fundamental mode, and to transmit each grating reflection spectrum using an optical signal carrying relevant monitoring data obtained from monitoring a designated device, so as to feed it back to the spatial mode conversion separation and multiplexing module.

[0012] The multi-channel spatial mode reflectance spectral processing module is used to demodulate and analyze the spectrum to be measured, so as to realize the synchronous detection and analysis of the relevant monitoring data carried by each grating reflectance spectrum in the multi-channel spatial mode Bragg fiber grating topology module.

[0013] The broadband light source output module includes a broadband light source that generates a broadband light with a C-band detection spectrum, a working wavelength of 1528nm to 1565nm, and a stability of ±0.005dBm / nm, and an output power range of 0mw to 20mw.

[0014] The eccentric fusion splicing high-order spatial mode excitation module includes a few-mode fiber circulator; wherein the few-mode fiber circulator performs eccentric fusion splicing with the single-mode pigtail of the broadband light source output module at a preset eccentric fusion splice point through the few-mode fiber; the fusion offset of the eccentric fusion splice point is determined by the number of grating incident spectra separated in the spatial mode conversion separation and multiplexing module.

[0015] The spatial mode conversion separation and multiplexing module includes a photonic lantern; the number of separations by the photonic lantern is determined by the number of feedback grating reflection spectra in the multi-path spatial mode Bragg fiber grating topology module.

[0016] The multi-channel spatial mode Bragg fiber grating topology module includes a multi-channel point-type fiber Bragg grating (FBG) sensor. Each FBG sensor is used to monitor the designated device to generate corresponding monitoring data. Upon receiving the incident spectrum of a corresponding grating, it generates a corresponding grating reflection spectrum and loads the relevant monitoring data into the optical signal of the grating reflection spectrum. The monitoring data is temperature or strain data.

[0017] The analysis results of the multi-channel spatial mode reflectance spectroscopy processing module include the curves showing the changes in the spectral center wavelength of the spectrum under test with temperature and strain in each spatial mode.

[0018] Wherein, the fundamental mode is LP 01 Pattern; the higher-order spatial patterns include LP 11 Pattern, LP 21 Patterns and LPs 02 model.

[0019] This invention also provides a fiber optic grating sensing multiplexing method based on photonic lantern mode diversity, the method comprising the following steps:

[0020] The broadband light source output module generates stable and power-adjustable broadband probe light;

[0021] The eccentric fusion higher-order spatial mode excitation module excites the broadband probe light through eccentric fusion to form a carrier that simultaneously carries the fundamental mode and the higher-order spatial mode.

[0022] The spatial mode conversion separation and multiplexing module demultiplexes and separates the broadband probe light that carries both the fundamental mode and the higher-order spatial mode to obtain the multi-path grating incident spectrum carried by the fundamental mode.

[0023] When the multi-channel spatial mode Bragg fiber grating topology module is irradiated by the incident spectrum of multiple gratings carried by the fundamental mode, it forms a corresponding grating reflection spectrum carried by the fundamental mode, and transmits each grating reflection spectrum using an optical signal carrying relevant monitoring data obtained from monitoring a designated device, so as to feed it back to the spatial mode conversion separation and multiplexing module.

[0024] When the multi-channel spatial mode reflectance spectroscopy processing module receives the spectrum to be measured, it demodulates and analyzes the spectrum to achieve synchronous detection and analysis of the relevant monitoring data carried by each grating reflectance spectrum in the multi-channel spatial mode Bragg fiber grating topology module. The spectrum to be measured is a multi-channel grating reflectance spectrum carried by the fundamental mode, which is multiplexed into a reflectance spectrum with both the fundamental mode and higher-order spatial modes in the spatial mode conversion, separation and multiplexing module, and then fed back by the eccentric fusion higher-order spatial mode excitation module.

[0025] Wherein, the fundamental mode is LP 01 Pattern; the higher-order spatial patterns include LP 11 Pattern, LP 21 Patterns and LPs 02 model.

[0026] Implementing the embodiments of the present invention has the following beneficial effects:

[0027] Compared to traditional wavelength division multiplexing (WDM), time division multiplexing (TDM), and space division multiplexing (SDM) technologies, this invention utilizes the spatial mode dimension and introduces a multi-channel spatial mode Bragg fiber grating topology module to distribute multiple monitoring data (acquired via FBG sensors) to channels carried by different spatial modes. This expands the number of spatial mode multiplexing monitoring points and enables simultaneous detection by multiple sensors. Furthermore, the spatial mode conversion separation and diversity multiplexing in the multiplexing module eliminate the need for spatial beam splitting and combining, resulting in advantages such as low system complexity and ease of integration. Therefore, it solves the problems of insufficient multiplexing capability, low reliability, high cost, and synchronous detection and positioning in existing fiber grating sensing multiplexing devices. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0029] Figure 1 This is a logical structure connection diagram of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in an embodiment of the present invention;

[0030] Figure 2 for Figure 1 Application scenario diagram of fiber optic grating sensing multiplexing device;

[0031] Figure 3 This is an example of the initial carrying reflection spectrum of each spatial mode in an application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in this embodiment of the invention.

[0032] Figure 4 The reflectance spectrum is a temperature monitoring application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in this embodiment of the invention.

[0033] Figure 5 The image shows wavelength-temperature sensitivity curves of different spatial modes in an application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in this embodiment of the invention.

[0034] Figure 6 The reflection spectrum is a strain monitoring application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in this embodiment of the invention.

[0035] Figure 7 The image shows wavelength-strain sensitivity curves of different spatial modes in an application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in this embodiment of the invention.

[0036] Figure 8 This is a reflection spectrum of temperature and strain mixed monitoring in an application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in an embodiment of the present invention.

[0037] Figure 9 The graphs show the wavelength-temperature sensitivity and wavelength-strain sensitivity curves of different spatial modes in an application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in this embodiment of the invention.

[0038] Figure 10This is a flowchart of a fiber optic grating sensing multiplexing method based on photonic lantern mode diversity provided in an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] like Figure 1 As shown in the figure, a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity proposed in this embodiment of the invention includes a broadband light source output module 200, an off-core fusion splicing high-order spatial mode excitation module 201, a spatial mode conversion, separation and multiplexing module 202, and a multi-channel spatial mode Bragg fiber optic grating topology module 203 connected in sequence, as well as a multi-channel spatial mode reflection spectrum processing module 204 connected to the off-core fusion splicing high-order spatial mode excitation module 201; wherein,

[0041] A broadband light source output module 200 is used to generate stable and power-adjustable broadband probe light;

[0042] In one example, the broadband light source output module 200 is a broadband light source (such as...). Figure 2 1) shown in the figure may be composed of an ASE broadband light source and an optical attenuator; wherein, the broadband light source generates a broadband light with a C-band detection spectrum, a working wavelength of 1528nm~1565nm and a stability of ±0.005dBm / nm, and its output power range is 0mw~20mw.

[0043] The eccentric fusion high-order spatial mode excitation module 201 and the broadband light source output module 200 are connected by an optical fiber eccentric fusion splice. The module is used to excite the broadband probe light through eccentric fusion to form a carrier that simultaneously carries the fundamental mode and the high-order spatial mode, and inject it into the spatial mode conversion, separation and multiplexing module 202; and to receive the spectrum to be measured fed back by the spatial mode conversion, separation and multiplexing module 202, and inject it into the multi-channel spatial mode reflection spectrum processing module 204.

[0044] In one example, the off-core fusion splicing higher-order spatial mode excitation module 201 includes a few-mode fiber circulator (e.g., Figure 2 As shown in Figure 3); wherein, the few-mode fiber circulator is connected to the single-mode pigtail of the broadband light source output module 200 via a few-mode fiber at a preset eccentric fusion splice point (such as...). Figure 2 As shown in step 2), eccentric fusion splicing is performed; the fusion offset of this eccentric fusion splice point is determined by the number of grating incident spectra separated in the spatial mode conversion separation and multiplexing module 202; at this time, the few-mode fiber circulator sets the fundamental mode to LP. 01 The broadband probe light of the mode is formed by simultaneously having a fundamental mode of LP. 01 Patterns and including LP11 Pattern, LP 21 Patterns and LPs 02 High-order spatial mode carrying; that is, few-mode fiber circulators can support LP. 01 LP 11 LP 21 LP 02 Four spatial modes.

[0045] The spatial mode conversion separation and multiplexing module 202 is used to demultiplex and separate the broadband probe light that carries both the fundamental mode and the higher-order spatial mode, to obtain a multi-path grating incident spectrum carried by the fundamental mode, and inject it into the multi-path spatial mode Bragg fiber grating topology module 203; and to multiplex the multi-path grating reflection spectrum carried by the fundamental mode and carrying relevant monitoring data fed back from the multi-path spatial mode Bragg fiber grating topology module 203, to obtain a single reflection spectrum that carries both the fundamental mode and the higher-order spatial mode and carries all monitoring data, and to feed this reflection spectrum as the spectrum to be measured back to the off-core fusion higher-order spatial mode excitation module 201;

[0046] In one example, the spatial mode conversion separation and multiplexing module 202 includes a photonic lantern (such as...). Figure 2 As shown in 5), at this time, the photonic lantern few-mode pigtail and the few-mode fiber circulator port few-mode pigtail are connected by a PC / APC flange connector; wherein, the number of separations of the photonic lantern is determined by the number of feedbacks of the grating reflection spectrum in the multi-path spatial mode Bragg fiber grating topology module 203, for example, it can support LP 01 LP 11 LP 21 LP 02 Four spatial modes are used to achieve conversion, separation, and multiplexing of the four spatial modes. Therefore, during forward incident light transmission, the fundamental mode LP will be used. 01 Both the broadband probe light carried by the higher-order spatial modes are converted into a unified light source from the fundamental mode LP. 01 The mode carries the multi-path grating incident spectrum, which is injected into the multi-path spatial mode Bragg grating topology module 203 respectively; during back-reflection light transmission, the LP generated by the multi-path spatial mode Bragg grating topology module 203 is used to generate the light. 01 The grating reflection spectrum carried by the mode is converted into the corresponding higher-order spatial mode and injected into the multi-channel spatial mode reflection spectrum processing module 204 through a few-mode fiber circulator.

[0047] The multi-path spatial mode Bragg fiber grating topology module 203 is used to form a corresponding grating reflection spectrum carried by the fundamental mode when irradiated by the incident spectrum of multiple gratings carried by the fundamental mode, and to transmit each grating reflection spectrum using an optical signal carrying relevant monitoring data obtained from monitoring a designated device, so as to feed it back to the spatial mode conversion separation and multiplexing module 202.

[0048] In one example, the multi-channel spatial mode Bragg fiber grating topology module 203 includes a multi-channel point-type fiber Bragg grating (FBG) sensor (such as... Figure 2 As shown in 7); where each FBG sensor is used to monitor a designated device to generate corresponding monitoring data (such as temperature, strain data, etc.), and receives data from a corresponding LP sensor. 01 When the grating incident spectrum carried by the mode is irradiated, a corresponding path is generated via LP. 01 The mode carries the grating reflection spectrum, and the relevant monitoring data is loaded into the optical signal of the grating reflection spectrum; that is, by utilizing the mode diversity fundamental mode LP 01 The mode carries multiple FBG sensors to different photonic lantern mode branches, enabling multi-point monitoring of changes in parameters such as temperature and strain caused by the equipment. The optical path is multiplexed through the spatial mode conversion, separation, and multiplexing module 202, converting the fundamental mode LP... 01 The mode is converted into the corresponding fundamental mode LP. 01 Patterns and LPs 11 LP 21 LP 02 Advanced spatial modes enable multiplexing of multi-channel independent sensors in multiple spatial modes.

[0049] The multi-channel spatial mode reflectance spectral processing module 204 is used to demodulate and analyze the spectrum under test, so as to realize the synchronous detection and analysis of the relevant monitoring data carried by each grating reflectance spectrum in the multi-channel spatial mode Bragg fiber grating topology module 203. The analysis results include, but are not limited to, the curves of the change of the spectral center wavelength of the spectrum under test with temperature and strain in each spatial mode.

[0050] In one example, the multi-channel spatial mode reflectance spectral processing module 204 demodulates and analyzes the center wavelength of the grating reflectance spectrum of the FBG sensor, and then processes it through the fundamental mode LP. 01 Patterns and LPs 11 LP 21 LP 02 The offset of the center wavelength of the grating reflection spectrum carried by the high-order spatial mode is calculated, and the temperature, strain and other data are monitored and analyzed simultaneously.

[0051] The multi-channel spatial mode reflectance spectral processing module 204 operates in the wavelength range of 1525nm to 1568nm, with an input optical power range of -60dBm to 5dBm and a wavelength resolution of 20pm. It supports the fundamental mode LP... 01 Patterns and LPs 11 LP 21 LP 02 The grating reflectance spectra of FBG sensors carried by higher-order spatial modes were used for spectral detection and data acquisition to analyze the changes in the spectral center wavelength of the grating reflectance spectra of FBG sensors carried by different spatial modes. Simultaneously, the fundamental mode LP... 01 Patterns and LPs 11 LP 21 LP 02 By measuring the change in the center wavelength of the spatial mode reflectance spectrum, wavelength-temperature and strain-temperature sensitivity curves of different spatial modes are obtained, enabling simultaneous monitoring and analysis of multi-point temperature, strain, and other data.

[0052] like Figures 3 to 9 As shown, the application scenario of a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity provided in this embodiment of the invention is further described below:

[0053] By LP 01 Patterns and LPs 11 LP 21 LP 02 The spectrum of the initial reflection center wavelength of the Bragg grating sensor carried by the higher-order spatial mode, as shown in... Figure 3 As shown. At this point, the initial reflection center wavelength is the center wavelength of the reflection spectrum under normal temperature (20℃) and stress (0µN), LP. 01 Patterns and LPs 11 LP 21 LP 02 The center wavelengths of the reflection spectra of the Bragg grating sensor carried by the higher-order spatial modes are 1545.01 nm, 1550.02 nm, 1554.98 nm and 1559.99 nm, respectively.

[0054] At this time, the fiber Bragg grating sensing multiplexing device is used for temperature monitoring, such as... Figure 4 As shown. Among them, Figure 4 (a) is LP 01 The pattern optical path carrying the fiber Bragg grating sensor shows the center wavelength-temperature variation. Taking an initial temperature of 20℃ and a center wavelength of 1545.01nm as a baseline, below 20℃, the center wavelength shifts to the left, reaching a center wavelength of 1544.61nm at 0℃. Above 20℃, the center wavelength shifts to the right, reaching a center wavelength of 1546.67nm at 100℃. At this point, LP... 11LP 21 LP 02 The Bragg grating sensor, which carries a high-order spatial mode, is subjected to a temperature of 20°C. Figure 4 (b) Wavelength-temperature variation diagrams of multiplexed fiber Bragg grating sensors with different spatial modes, extending single-channel detection to LP based on actual application requirements. 01 LP 11 LP 21 and LP 02 Multiple spatial modes can be reused to simultaneously monitor temperature changes at different spatial locations, thus realizing mode reuse of fiber Bragg grating temperature sensors.

[0055] The fiber grating sensing multiplexing device analyzed the wavelength-temperature sensitivity curves for different spatial modes, as shown in the following figures. Figure 5 As shown. Among them, Figure 5 (a) is the fundamental mode LP 01 The wavelength-temperature fitting line of the FBG sensor carried by the mode is obtained by fitting 100 sets of data consisting of temperature and corresponding center wavelength in the temperature range of -100℃ to 100℃, with a goodness of fit R. 2 =99.958%. Figure 5 (b) then by extending to LP 01 Patterns and LPs 11 LP 21 LP 02 The Bragg grating sensor, implemented in a higher-order spatial mode, simultaneously measures temperature. Similarly, fitting 100 sets of data yields wavelength-temperature fitting lines for the FBG sensor in the extended four LP modes, with a goodness-of-fit R0. 2 The accuracy rates were 99.958%, 99.967%, 99.949%, and 99.967%, respectively. The measurement accuracy did not decrease significantly after expansion, demonstrating the good scalability of the modular multiplexing system.

[0056] At this time, the fiber optic grating sensing multiplexing device is used for strain monitoring, such as... Figure 6 As shown. Among them, Figure 6 (a) is LP 11 The optical path carries the center wavelength-strain variation diagram of the fiber Bragg grating sensor. The fiber Bragg grating strain sensor measured micro-strain from -500μN to 500μN. With the initial strain of 0μN and the center strain of 1550.02nm as the reference, below 0N, the center wavelength of the reflection spectrum shifts to the left, reaching 1549.29nm at -500μN; above 0N, the center wavelength of the reflection spectrum shifts to the right, reaching 1550.71nm at 500μN. Figure 6 (b) Wavelength-strain variation diagrams of multiplexed fiber Bragg grating sensors with different spatial modes, extending single-channel detection to LP according to actual application requirements. 01LP 11 LP 21 and LP 02 Four spatial modes are multiplexed to simultaneously monitor strain changes at different spatial locations, realizing mode multiplexing of fiber optic strain sensors.

[0057] The wavelength-strain sensitivity curves of different spatial modes analyzed by the fiber Bragg grating sensing multiplexing device are shown in the following figures. Figure 7 As shown. Among them, Figure 7 (a) is the fundamental mode LP 01 The wavelength-strain fitting line of the FBG sensor carried by the mode is obtained by fitting 100 sets of data consisting of strain values ​​and corresponding center wavelengths in the range of -800μN to 800μN. The goodness of fit R is... 2 =99.936%. Figure 7 (b) then by extending to LP 01 Patterns and LPs 11 LP 21 LP 02 The Bragg grating sensor, implemented in a higher-order spatial mode, simultaneously performs strain measurement. Similarly, fitting 100 sets of data yields wavelength-strain fitting lines for the FBG sensor in the extended four LP modes, with a goodness-of-fit R0. 2 The percentages were 99.915%, 99.954%, 99.924%, and 99.936%, respectively. The measurement accuracy did not decrease significantly after expansion, demonstrating the good scalability of the modular multiplexing system.

[0058] At this time, the fiber optic grating sensing multiplexing device is used for mixed monitoring of temperature and strain reflection spectra, such as... Figure 8 As shown. Based on practical needs, this can be extended to simultaneously monitor temperature and strain changes at different spatial locations using multiple spatial models. Among them, LP... 01 and LP 02 The fiber Bragg grating sensors in the spatial mode have center wavelengths of 1545.01 nm and 1559.99 nm, respectively, and are used for temperature measurement. LP 11 and LP 21 The fiber Bragg grating sensors in the spatial mode, with center wavelengths of 1550.02 nm and 15545.98 nm, are used to measure strain.

[0059] The fiber Bragg grating sensing multiplexing device analyzed the hybrid multiplexing sensitivity curves of different spatial modes, as shown in the figure. Figure 9 As shown. Wherein, LP 01 and LP 02 The FBG sensor it carries is a temperature sensor. It acquires different temperatures and corresponding center wavelengths from two FBG sensors within a temperature range of -100℃ to 100℃; high-order mode LP11 and LP 21 The FBG sensor used is a strain sensor. Two FBG sensors were used to obtain different strains and corresponding center wavelengths within a strain range of -800μN to 800μN. Temperature (strain) versus center wavelength fitting lines were obtained for each sensor by fitting 100 sets of data, with a goodness of fit R0. 2 They were 99.968%, 99.943%, 99.939%, and 99.963%, respectively.

[0060] like Figure 10 As shown, this is an embodiment of the present invention, which proposes a fiber optic grating sensing multiplexing method based on photonic lantern mode diversity. It is implemented on a fiber optic grating sensing multiplexing device based on photonic lantern mode diversity in this embodiment of the present invention. The method includes the following steps:

[0061] Step S1: The broadband light source output module generates a stable and power-adjustable broadband probe light;

[0062] Step S2: The eccentric fusion higher-order spatial mode excitation module excites the broadband probe light through eccentric fusion to form a carrier that simultaneously carries the fundamental mode and the higher-order spatial mode.

[0063] Step S3: The spatial mode conversion separation and multiplexing module demultiplexes and separates the broadband probe light that carries both the fundamental mode and the higher-order spatial mode to obtain the multi-path grating incident spectrum carried by the fundamental mode.

[0064] Step S4: When the multi-channel spatial mode Bragg fiber grating topology module is irradiated by the incident spectrum of multiple gratings carried by the fundamental mode, it forms a corresponding grating reflection spectrum carried by the fundamental mode, and transmits each grating reflection spectrum using an optical signal carrying relevant monitoring data obtained from monitoring the designated device, so as to feed it back to the spatial mode conversion separation and multiplexing module.

[0065] Step S5: When the multi-channel spatial mode reflectance spectroscopy processing module receives the spectrum to be measured, it demodulates and analyzes the spectrum to be measured, so as to realize the synchronous detection and analysis of the relevant monitoring data carried by each grating reflectance spectrum in the multi-channel spatial mode Bragg fiber grating topology module; wherein, the spectrum to be measured is the multi-channel grating reflectance spectrum carried by the fundamental mode, which is multiplexed into a reflectance spectrum with both the fundamental mode and the higher-order spatial mode in the spatial mode conversion, separation and multiplexing module, and fed back by the eccentric fusion higher-order spatial mode excitation module.

[0066] Wherein, the fundamental mode is LP 01 Pattern; the higher-order spatial patterns include LP 11 Pattern, LP 21Patterns and LPs 02 model.

[0067] Implementing the embodiments of the present invention has the following beneficial effects:

[0068] Compared to traditional wavelength division multiplexing (WDM), time division multiplexing (TDM), and space division multiplexing (SDM) technologies, this invention utilizes the spatial mode dimension and introduces a multi-channel spatial mode Bragg fiber grating topology module to distribute multiple monitoring data (acquired via FBG sensors) to channels carried by different spatial modes. This expands the number of spatial mode multiplexing monitoring points and enables simultaneous detection by multiple sensors. Furthermore, the spatial mode conversion separation and diversity multiplexing in the multiplexing module eliminate the need for spatial beam splitting and combining, resulting in advantages such as low system complexity and ease of integration. Therefore, it solves the problems of insufficient multiplexing capability, low reliability, high cost, and synchronous detection and positioning in existing fiber grating sensing multiplexing devices.

[0069] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as ROM / RAM, disk, optical disk, etc.

[0070] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A fiber optic grating sensing multiplexing device based on photonic lantern mode diversity, characterized in that, The system includes, in sequence, a broadband light source output module, an off-core fusion splicing high-order spatial mode excitation module, a spatial mode conversion, separation and multiplexing module, and a multi-channel spatial mode Bragg fiber grating topology module, as well as a multi-channel spatial mode reflectance spectral processing module connected to the off-core fusion splicing high-order spatial mode excitation module; wherein, The broadband light source output module is used to generate stable and power-adjustable broadband probe light; The eccentric fusion higher-order spatial mode excitation module and the broadband light source output module are connected by an optical fiber eccentric fusion method. The module is used to excite the broadband probe light through eccentric fusion to form a signal carrying both the fundamental mode and a higher-order spatial mode, and inject it into the spatial mode conversion, separation and multiplexing module. The module also receives the spectrum to be measured fed back from the spatial mode conversion, separation and multiplexing module and injects it into the multi-channel spatial mode reflectance spectrum processing module. The spatial mode conversion, separation, and multiplexing module is used to demultiplex and separate the broadband probe light that simultaneously carries the fundamental mode and higher-order spatial modes, obtaining a multi-path incident broadband light of gratings carried by the fundamental mode, and injecting it into the multi-path spatial mode Bragg fiber grating topology module; and to multiplex the multi-path fiber grating reflection spectra carried by the fundamental mode and carrying relevant monitoring data fed back from the multi-path spatial mode Bragg fiber grating topology module, obtaining a single reflection spectrum that simultaneously carries the fundamental mode and higher-order spatial modes and carries all monitoring data, and feeding this reflection spectrum as the spectrum to be measured back to the off-core fusion higher-order spatial mode excitation module; The multi-path spatial mode Bragg fiber grating topology module is used to form a corresponding grating reflection spectrum carried by the fundamental mode when irradiated by the incident spectrum of multiple gratings carried by the fundamental mode, and to transmit each grating reflection spectrum using an optical signal carrying relevant monitoring data obtained from monitoring a designated device, so as to feed it back to the spatial mode conversion separation and multiplexing module. The multi-channel spatial mode reflectance spectral processing module is used to demodulate and analyze the spectrum to be measured, so as to realize the synchronous detection and analysis of the relevant monitoring data carried by each grating reflectance spectrum in the multi-channel spatial mode Bragg fiber grating topology module.

2. The fiber optic grating sensing multiplexing device based on photonic lantern mode diversity as described in claim 1, characterized in that, The broadband light source output module includes a broadband light source, which generates broadband light with a C-band detection spectrum, a working wavelength of 1528nm to 1565nm, and a stability of ±0.005dBm / nm, and its output power ranges from 0mw to 20mw.

3. The fiber optic grating sensing multiplexing device based on photonic lantern mode diversity as described in claim 2, characterized in that, The eccentric fusion splicing high-order spatial mode excitation module includes a few-mode fiber circulator; wherein, the few-mode fiber circulator performs eccentric fusion splicing with the single-mode pigtail of the broadband light source output module through the few-mode fiber at a preset eccentric fusion splice point; the fusion offset of the eccentric fusion splice point is determined by the number of grating incident spectra separated in the spatial mode conversion separation and multiplexing module.

4. The fiber optic grating sensing multiplexing device based on photonic lantern mode diversity as described in claim 3, characterized in that, The spatial mode conversion separation and multiplexing module includes a photonic lantern; wherein the number of separations by the photonic lantern is determined by the number of feedbacks of the grating reflection spectrum in the multi-path spatial mode Bragg fiber grating topology module.

5. The fiber optic grating sensing multiplexing device based on photonic lantern mode diversity as described in claim 4, characterized in that, The multi-channel spatial mode Bragg fiber grating topology module includes a multi-channel point-type fiber Bragg grating (FBG) sensor; wherein, each FBG sensor is used to monitor the designated device to generate corresponding monitoring data, and when receiving the incident spectrum of the corresponding grating, it generates the corresponding grating reflection spectrum, and loads the relevant monitoring data into the optical signal of the grating reflection spectrum; the monitoring data is temperature or strain data.

6. The fiber optic grating sensing multiplexing device based on photonic lantern mode diversity as described in claim 5, characterized in that, The analysis results of the multi-channel spatial mode reflectance spectroscopy processing module include the curves showing the changes in the spectral center wavelength of the spectrum under test with temperature and strain in each spatial mode.

7. The fiber optic grating sensing multiplexing device based on photonic lantern mode diversity as described in claim 6, characterized in that, The fundamental mode is LP. 01 Pattern; the higher-order spatial patterns include LP 11 Pattern, LP 21 Patterns and LPs 02 model.

8. A fiber optic grating sensing multiplexing method based on photonic lantern mode diversity, characterized in that, The method includes the following steps: The broadband light source output module generates stable and power-adjustable broadband probe light; The eccentric fusion higher-order spatial mode excitation module excites the broadband probe light through eccentric fusion to form a carrier that simultaneously carries the fundamental mode and the higher-order spatial mode. The spatial mode conversion separation and multiplexing module demultiplexes and separates the broadband probe light that carries both the fundamental mode and the higher-order spatial mode to obtain the multi-path grating incident spectrum carried by the fundamental mode. When the multi-path spatial mode Bragg fiber grating topology module receives multiple grating incident spectra carried by the fundamental mode, it forms a corresponding grating reflection spectrum carried by the fundamental mode, and transmits each grating reflection spectrum using an optical signal carrying relevant monitoring data obtained from monitoring a designated device, so as to feed it back to the spatial mode conversion separation and multiplexing module. When the multi-channel spatial mode reflectance spectroscopy processing module receives the spectrum to be measured, it demodulates and analyzes the spectrum to achieve synchronous detection and analysis of the relevant monitoring data carried by each grating reflectance spectrum in the multi-channel spatial mode Bragg fiber grating topology module. The spectrum to be measured is a multi-channel grating reflectance spectrum carried by the fundamental mode, which is multiplexed into a reflectance spectrum with both the fundamental mode and higher-order spatial modes in the spatial mode conversion, separation and multiplexing module, and then fed back by the eccentric fusion higher-order spatial mode excitation module.

9. The fiber optic grating sensing multiplexing method based on photonic lantern mode diversity as described in claim 8, characterized in that, The fundamental mode is LP. 01 Pattern; the higher-order spatial patterns include LP 11 Pattern, LP 21 Patterns and LPs 02 model.

Images