A non-contact optical fiber sensing system and method

Abstract

The present invention provides a non-contact optical fiber sensing system and method. The system includes a passive fiber Bragg grating sensor and an active demodulation analyzer. The passive fiber Bragg grating sensor includes an optical fiber and a fiber Bragg grating sensor connected in series on the optical fiber. The active demodulation analyzer includes a laser light source, an optical circulator, and a demodulation analyzer. One end of the passive fiber Bragg grating sensor is connected with a first fiber collimator. The active demodulation analyzer further includes a second fiber collimator and an alignment mechanism. The laser light source is connected to the first end of the optical circulator for outputting an optical signal. The optical fiber led out from the second end of the optical circulator is connected with the second fiber collimator. The second fiber collimator is used for non-contact alignment with the first fiber collimator under the adjustment of the alignment mechanism so as to transmit the optical signal bidirectionally. The demodulation analyzer is connected to the third end of the optical circulator. The present invention can expand the application scenarios of the optical fiber sensing system and save costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber sensing, and particularly relates to a non-contact optical fiber sensing system and method. Background Art

[0002] Optical fiber sensing is suitable for large-scale and long-distance sensing application scenarios, and is widely used in fields such as transportation (railways, highways, bridges), power communication (transmission cables), coal mines and mountains, oil and gas exploration, aerospace equipment, and urban security. It is a very promising sensing technology in the market.

[0003] Figure 1 As shown, a common optical fiber sensing system is formed by physically connecting a passive fiber Bragg grating sensor 1 and an active demodulation analyzer 2. The passive fiber Bragg grating sensor 1 is obtained by writing a weak reflection Bragg grating (the reflectivity of a single grating <1%) at intervals on the core of a fiber. The active demodulation analyzer 2 includes a laser light source, a circulator, and a demodulation analyzer. The laser pulse emitted by the laser light source passes through the circulator into the fiber of the passive fiber Bragg grating sensor 1, and the laser reflected from each weak reflection Bragg grating is received by the demodulation analyzer through the circulator. By analyzing the change in the laser wavelength reflected from each grating, the deformation and temperature change at each grating can be sensed.

[0004] However, currently, the application scenarios of optical fiber sensing technology have great limitations and are mainly applied to static large-scale projects. One of the reasons is that both the passive fiber Bragg grating sensor 1 as the sensor and the active demodulation analyzer 2 are physically connected together to form a complete set of sensing systems, and the demodulation analyzer is expensive and large in size, so it is generally only used in large-scale key projects. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a non-contact optical fiber sensing system and method, so as to expand the application scenarios of the optical fiber sensing system.

[0006] The technical solution adopted by the present invention to solve the above technical problem is as follows:

[0007] As the first aspect of the present invention, the present invention provides a non-contact optical fiber sensing system, including a passive fiber Bragg grating sensor and an active demodulation analyzer. The passive fiber Bragg grating sensor includes a fiber and fiber Bragg grating sensors connected in series on the fiber. The active demodulation analyzer includes a laser light source, an optical circulator, and a demodulation analyzer;

[0008] The passive fiber Bragg grating sensor is disposed on the object to be detected, and one end of the passive fiber Bragg grating sensor is connected to a first fiber collimator;

[0009] The active demodulation analyzer described above is provided on a movable carrier, and the active demodulation analyzer further includes a second fiber collimator and an alignment mechanism; wherein, the laser light source is connected to the first end of the optical circulator for outputting an optical signal; a fiber is led out from the second end of the optical circulator and connected to the second fiber collimator, and the second fiber collimator is used for non-contact alignment with the first fiber collimator under the adjustment of the alignment mechanism to transmit the optical signal bidirectionally; the demodulation analyzer is connected to the third end of the optical circulator.

[0010] According to the above solution, the alignment mechanism includes an image acquisition unit and a motion platform; wherein,

[0011] The image acquisition unit is used to identify the position of the first fiber collimator;

[0012] The motion platform is used to adjust the beam axis of the second fiber collimator to be aligned with the beam axis of the first fiber collimator;

[0013] Both the first fiber collimator and the second fiber collimator are used to amplify the optical signal to form parallel light for transmission.

[0014] According to the above solution, the motion platform is a four-axis platform for adjustment in four directions of y, z, θy, and θz; where z is the vertical direction, y is the horizontal direction and perpendicular to the laser direction emitted from the second fiber collimator, θy is the pitch angle on the horizontal plane, and θz is the yaw angle on the vertical plane.

[0015] According to the above solution, the image acquisition unit is an industrial camera fixed on the motion platform.

[0016] According to the above solution, the motion platform includes a box body, a two-dimensional linear module, and a biaxial galvanometer; wherein,

[0017] The biaxial galvanometer and the second fiber collimator are respectively fixed in the box body. The biaxial galvanometer includes a reflecting mirror and two rotating shafts for adjusting the angles of the reflecting mirror in the θy and θz directions. The light passing through the second fiber collimator is reflected by the reflecting mirror and then output, constituting the second beam axis of the second fiber collimator;

[0018] The box body is fixed to the moving end of the two-dimensional linear module, and the second beam axis of the second fiber collimator is controlled to move in the z direction and the y direction through the two-dimensional linear module.

[0019] According to the above solution, a metal disc is externally connected to the first fiber collimator, and the metal disc is perpendicular to the first beam axis of the first fiber collimator;

[0020] The metal disc is arranged at the end of the object to be detected for the image acquisition unit to collect images.

[0021] According to the above solution, the object to be detected is a bridge, a building, a highway, a transmission cable or a new energy vehicle battery pack.

[0022] According to the above solution, the movable carrier is a drone or an autonomous vehicle; the alignment mechanism is controlled and adjusted by a control unit in the movable carrier.

[0023] As a second aspect of the present invention, the present invention also provides a sensing method for the non-contact optical fiber sensing system, including the following steps:

[0024] S1. The movable carrier moves within a certain distance from the object to be detected;

[0025] S2. Obtain the optical axis position of the first fiber collimator;

[0026] S3. Adjust the position and angle of the second fiber collimator so that the second fiber collimator is non-contact aligned with the first fiber collimator;

[0027] S4. The optical signal emitted by the laser source is transmitted in the natural space to the first fiber collimator after passing through the circulator and the second fiber collimator. The optical signal reflected back by the fiber grating sensor in the passive fiber grating sensor is transmitted in the natural space to the second fiber collimator after passing through the first fiber collimator, and then reaches the demodulation analyzer through the circulator for demodulation.

[0028] According to the above method, in S2, the spatial position of the first fiber collimator is obtained by the image acquisition unit, and the optical axis position of the first fiber collimator is calculated.

[0029] According to the above method, a metal disc is externally connected to the first fiber collimator, and the metal disc is perpendicular to the beam axis of the first fiber collimator;

[0030] Specifically, in S2, the three-dimensional point cloud of the metal disc and the first fiber collimator is obtained by taking pictures with a 3D industrial camera. The plane equation of the metal disc and the spatial position of the first fiber collimator are obtained through a visual matching algorithm, and a ray perpendicular to the plane equation starting from the spatial position of the first fiber collimator is calculated. This ray is the optical axis position of the first fiber collimator.

[0031] According to the above method, S3 specifically includes:

[0032] S31. According to the optical axis position of the first fiber collimator, adjust the movement in the y and z directions through a two-dimensional linear module so that the beam axis of the first fiber collimator passes through the center of the mirror of the biaxial galvanometer;

[0033] S32. Control the laser light source to emit an optical signal, adjust the angles of the two rotation axes of the two-axis galvanometer so that the reflecting mirror deflects within a certain range to form the scanning of the two-axis galvanometer. The optical signal output from the second fiber collimator scans back and forth within the scanning area of the galvanometer. When the beam axis of the light beam emitted from the second fiber collimator coincides with the beam axis of the first fiber collimator, the second fiber collimator is non-contact aligned with the first fiber collimator;

[0034] The two rotation axes are respectively used to adjust the angles of the reflecting mirror in the θy and θz directions;

[0035] The z direction is the vertical direction, the y direction is the horizontal direction and perpendicular to the laser direction emitted from the second fiber collimator, θy is the pitch angle on the horizontal plane, and θz is the yaw angle on the vertical plane.

[0036] The beneficial effects of the present invention are as follows:

[0037] 1. Since the physical quantity of the object to be detected does not need to be monitored at all times, in the present invention, the connection between the passive fiber Bragg grating sensor and the active demodulation analyzer is non-contact sensor-connected by two fiber collimators, so that the passive fiber Bragg grating sensor is arranged on the object to be detected, and the expensive active demodulation analyzer is arranged on the movable carrier. When monitoring is required, the movable carrier can be moved to the side of the object to be detected, thus expanding the application scenario of the fiber optic sensing system and saving costs.

[0038] 2. The fiber collimator at the object to be detected end is quickly positioned by the image acquisition unit, and then the fiber collimator at the movable carrier end is finely adjusted by the motion platform, so as to quickly align the two fiber collimators.

[0039] 3. By using the scanning of the two-axis galvanometer, as long as the beam axis of the first fiber collimator is within the scanning area of the galvanometer, the alignment between the two fiber collimators can be ensured. Description of the Drawings

[0040] Figure 1 is a schematic diagram of a common fiber optic sensing system in the prior art.

[0041] Figure 2 is a schematic diagram of the principle of an embodiment of the present invention.

[0042] Figure 3 is a schematic diagram of the application scenario of an embodiment of the present invention.

[0043] Figure 4 is a schematic diagram of the application scenario of another embodiment of the present invention.

[0044] Figure 5 is a schematic diagram of the image acquisition principle of an embodiment of the present invention.

[0045] In the figure:

[0046] 1 - Passive fiber Bragg grating sensor, 101 - Optical fiber, 102 - Fiber Bragg grating sensor;

[0047] 2 - Active demodulation analyzer;

[0048] 3 - First fiber collimator, 301 - First beam axis;

[0049] 4 - Second fiber collimator, 401 - Second beam axis;

[0050] 5 - Battery pack;

[0051] 6 - Unmanned vehicle;

[0052] 701 - Image acquisition unit, 702 - Motion platform, 7021 - Two - axis galvanometer, 70211 - First reflector, 70212 - Second reflector, 7022 - Two - dimensional linear module;

[0053] 8 - Box body;

[0054] 9 - Metal disc. Detailed implementation manners

[0055] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] As the first aspect of the present invention, the present invention provides a non - contact fiber optic sensing system, as Figure 2 shown, including a passive fiber Bragg grating sensor 1 and an active demodulation analyzer 2.

[0057] Among them, the passive fiber Bragg grating sensor 1 includes an optical fiber 101 and a fiber Bragg grating sensor 102 connected in series on the optical fiber 101, and one end of the passive fiber Bragg grating sensor 1 is connected to a first fiber collimator 3. The passive fiber Bragg grating sensor 1 is arranged on the object to be detected.

[0058] The active demodulation analyzer 2 includes a laser light source, an optical circulator, a demodulation analyzer, a second fiber collimator 4 and an alignment mechanism. The laser light source is connected to the first end of the optical circulator for outputting an optical signal; the second end of the optical circulator leads out an optical fiber and is connected to the second fiber collimator 4, and the second fiber collimator 4 is used for non - contact alignment with the first fiber collimator 3 under the adjustment of the alignment mechanism to transmit the optical signal bidirectionally; the demodulation analyzer is connected to the third end of the optical circulator.

[0059] The present invention aims to utilize a first fiber collimator 3 and a second fiber collimator 4 to amplify the laser spot transmitted within the optical fiber, forming parallel light. By aligning the two fiber collimators, the parallel light can be transmitted contactlessly between them. The first fiber collimator 3 and the second fiber collimator 4 have the same structure. Common fiber collimators contain a self-focusing lens.

[0060] The present invention provides an alignment mechanism for automatically aligning a fiber collimator, such as Figure 3 As shown, the alignment mechanism includes an image acquisition unit 701 and a motion platform 702 .

[0061] The image acquisition unit 701 is used to identify the position of the first fiber collimator 3. In this embodiment, the image acquisition unit uses an industrial camera, such as a 3D industrial camera, which is fixed on a motion platform. In this embodiment, in order to cooperate with the image acquisition of the 3D industrial camera, the object end to be detected is adaptively set. Specifically, Figure 5 As shown, the first fiber optic collimator 3 is externally connected to a metal disk 9, which is perpendicular to the first beam axis 301 of the first fiber optic collimator 3. The metal disk 9 is placed at the end of the object to be inspected, allowing the image acquisition unit 701 to capture images. The image acquisition unit 701 captures a three-dimensional point cloud of the metal disk 9 and the first fiber optic collimator 3. Using a visual matching algorithm, the plane equation of the metal disk 9 and the spatial position of the first fiber optic collimator 3 are obtained. A ray perpendicular to the plane equation is calculated from the spatial position of the first fiber optic collimator 3. This ray is the optical axis position of the first fiber optic collimator 3.

[0062] The motion platform 702 is used to adjust the second light beam axis 401 of the second optical fiber collimator 4 to be aligned with the first light beam axis 301 of the first optical fiber collimator 3 .

[0063] In this embodiment, the motion platform 702 is a four-axis platform used to adjust the second light beam axis 401 in four directions: y, z, θy, and θz; wherein z is the vertical direction, y is the horizontal direction and is perpendicular to the direction of the laser emitted from the second fiber collimator, θy is the pitch angle on the horizontal plane (i.e., the rotation direction around an axis parallel to the y-axis), and θz is the yaw angle on the vertical plane (i.e., the rotation direction around an axis parallel to the z-axis).

[0064] To minimize signal strength drops, the beams entering and exiting the first and second fiber collimators 3 and 4 are parallel beams with a diameter of approximately 1 mm. The four-axis platform requires near-perfect alignment of the second beam axis 401 of the second fiber collimator 4 with the first beam axis 301 of the first fiber collimator 3 to achieve communication.

[0065] There are many ways to achieve adjustments in the four directions of y, z, θy, and θz. In this embodiment, the y and z directions are adjusted using a two-dimensional linear module, and the θy and θz directions are adjusted using a two-axis galvanometer. As Figure 4 shown, the motion platform includes a box body 8, a two-dimensional linear module 7022, and a two-axis galvanometer 7021. Among them, the two-axis galvanometer 7021 and the second fiber collimator 4 are respectively fixed in the box body 8. The two-axis galvanometer 7021 includes a reflecting mirror and two rotating shafts for adjusting the angles of the reflecting mirror in the θy and θz directions. The light passing through the second fiber collimator 4 is reflected by the reflecting mirror and then output, forming the second beam axis 401 of the second fiber collimator 4. In this embodiment, the reflecting mirror includes a first reflecting mirror 70211 and a second reflecting mirror 70212, and each reflecting mirror is adjusted by one rotating shaft, finally achieving the adjustment in two rotating directions. The box body 8 is fixed to the moving end of the two-dimensional linear module 7022, and the second beam axis 401 of the second fiber collimator 4 is controlled by the two-dimensional linear module 7022 to move in the z direction and the y direction.

[0066] Furthermore, the second fiber collimator 4 is fixed to the side of the two-axis galvanometer 7021. After the optical signal is output from the second fiber collimator 4, it is reflected by the first reflecting mirror 70211 and the second reflecting mirror 70212 in the two-axis galvanometer 7021 and then output. The second beam axis 401 of the output beam is adjusted as the first reflecting mirror 70211 and the second reflecting mirror 70212 swing. Within the swing range of the reflecting mirror, the output beam forms a scanning area. The swings of the first reflecting mirror 70211 and the second reflecting mirror 70212 are respectively adjusted by two rotating shafts for adjusting the angles in the θy and θz directions. When the second beam axis 401 coincides with the first beam axis 301 of the first fiber collimator 3, the first fiber collimator 3 and the second fiber collimator 4 complete alignment, and at this time, the passive fiber grating sensor 1 and the active demodulation analyzer 2 complete one communication.

[0067] It should be noted that Figure 4 only for a schematic diagram, drawing the second fiber collimator 4, the motion platform, etc. outside the unmanned vehicle 6 is to magnify the structure for easy understanding. In fact, the structures such as the second fiber collimator 4 and the motion platform are all located in the unmanned vehicle 6.

[0068] For the adjustment in the θy and θz directions, it can also be replaced by directly adjusting the angle of the second fiber collimator 4 with 2 rotating shafts.

[0069] Continue as Figure 2 and Figure 3As shown in the figure, in specific applications, the passive fiber Bragg grating sensor 1 is disposed on the object to be detected, such as the battery pack 5 of an electric bus (for detecting the temperature at various locations of the battery pack), and it can also be a bridge, a building, a road, a transmission cable, etc. For the convenience of non-contact signal transmission, the first fiber collimator 3 is fixed at the end of the object to be detected. The active demodulation analyzer 2 is disposed on a movable carrier, such as an unmanned vehicle 6, and it can also be an unmanned aerial vehicle, etc. The alignment mechanism is controlled and adjusted by the control unit in the movable carrier, thereby saving control costs. As an alternative solution, it can also be equipped with its own control unit. The second fiber collimator 4, the alignment mechanism, and the active demodulation analyzer 2 form an integrated unit, which can be carried on any movable carrier.

[0070] As the second aspect of the present invention, the present invention also provides a sensing method for the non-contact fiber optic sensing system, including the following steps:

[0071] S1. The movable carrier moves within a certain distance from the object to be detected. The positional relationship between the movable carrier and the object to be detected can be determined according to the positions of the first fiber collimator and the second fiber collimator during actual applications.

[0072] S2. Obtain the spatial position of the first fiber collimator. Specifically, the spatial position of the first fiber collimator can be obtained through an image acquisition unit, and then the spatial position of the light beam axis of the first fiber collimator can be calculated based on an image processing algorithm.

[0073] In this embodiment, a metal disk is externally connected to the first fiber collimator, and the metal disk is perpendicular to the first light beam axis of the first fiber collimator. The three-dimensional point cloud of the metal disk and the first fiber collimator is obtained by taking pictures with a 3D industrial camera. The plane equation of the metal disk and the spatial position of the first fiber collimator are obtained through a visual matching algorithm, and a ray perpendicular to the plane equation starting from the spatial position of the first fiber collimator is calculated. This ray is the optical axis position of the first fiber collimator.

[0074] S3. Adjust the position and angle of the second fiber collimator so that the second fiber collimator is non-contact aligned with the first fiber collimator. Specifically, it can include the following steps:

[0075] S31. According to the spatial position of the light beam axis of the first fiber collimator, adjust the movement in the y and z directions through a two-dimensional linear module so that the light beam axis of the first fiber collimator passes through the center of the mirror of the two-axis galvanometer; the z direction is the vertical direction, and the y direction is the horizontal direction and perpendicular to the laser direction emitted from the second fiber collimator.

[0076] S32. Control the laser light source to emit an optical signal, and adjust the angles of the two rotation axes of the two-axis galvanometer so that the reflecting mirror deflects within a certain range to form the scanning of the two-axis galvanometer. The optical signal output from the second fiber collimator scans back and forth within the scanning area of the galvanometer. When the beam axis of the light beam emitted from the second fiber collimator coincides with the beam axis of the first fiber collimator, the second fiber collimator is non-contact aligned with the first fiber collimator. The two rotation axes are respectively used to adjust the angles of the reflecting mirror in the θy and θz directions. θy is the pitch angle on the horizontal plane, and θz is the yaw angle on the vertical plane.

[0077] S4. When non-contact alignment is achieved, the optical signal emitted by the laser light source is transmitted in the natural space to the first fiber collimator after passing through the circulator and the second fiber collimator. The optical signal reflected back by the fiber Bragg grating sensor in the passive fiber Bragg grating sensor is transmitted in the natural space to the second fiber collimator after passing through the first fiber collimator, and then reaches the demodulation analyzer through the circulator for demodulation.

[0078] The working process of the present invention will be further described below in combination with specific application scenarios. There are more and more electric buses in each city. During the charging process, it is easy to cause explosions and fires due to excessive temperature inside the battery pack. Therefore, the centralized charging places for electric buses are key fire prevention places, but there is currently no effective solution for monitoring the temperature inside the battery pack. This embodiment can achieve periodic monitoring of the temperature inside the battery pack of electric buses. As Figure 3 shown, when the bus manufacturer produces the battery pack 5, the passive fiber Bragg grating sensor 1 with the first fiber collimator 3 is buried inside the battery pack. The passive fiber Bragg grating sensor 1 is a conventional temperature sensor and is buried in the battery pack using conventional technology. The active demodulation analyzer 2 (including a laser, an optical circulator, and a demodulation analyzer), the second fiber collimator 4, the industrial camera 701, and the moving platform 702 are all installed on a driverless vehicle 6.

[0079] In the centralized charging place, the driverless vehicle 6 periodically inspects the temperature inside the battery pack 5 of each electric bus being charged. The specific working process is as follows:

[0080] 1. The driverless vehicle 6 runs to a fixed point in front of the first electric bus. When the position of the first fiber collimator 3 installed on the electric bus is determined, and the positions of the second fiber collimator 4 and the industrial camera 701 on the driverless vehicle 6 are also determined, since the position of the charging parking space is determined, the parking position of the driverless vehicle 6, that is, the fixed point, can be determined. In this embodiment, the fixed point is 2 - 5 meters in front of the charging parking space. The industrial camera 701 takes pictures to identify the relative position of the first fiber collimator 3 on the bus mainly to determine the position of the first beam axis 301 of the first fiber collimator 3.

[0081] 2. The controller on the driverless vehicle 6 aligns the second fiber collimator 4 with the first fiber collimator 3 by adjusting the motion platform 702 according to the above position data, that is: the second light beam axis 401 of the second fiber collimator 4 coincides with the first light beam axis 301 of the first fiber collimator 3. The distance between the second fiber collimator 4 and the first fiber collimator 3 enables the smooth transmission of optical signals, generally within 2 - 10 meters, preferably 3 - 5 meters.

[0082] 3. After alignment, the laser source emits broadband laser pulses. The pulses are emitted from the second fiber collimator 4, enter the first fiber collimator 3, and after encountering the fiber grating sensor 102, the laser with a specific wavelength will be reflected back. The reflected laser passes through the first fiber collimator 3 and is transmitted through space back to the second fiber collimator 4, and then enters the demodulation analyzer after passing through the circulator.

[0083] 4. The demodulation analyzer calculates the temperature at the grating according to the change in the optical wave wavelength returned by each grating. If the temperature of the fiber grating sensor on the battery pack 5 is abnormal, the driverless vehicle 6 can issue an alarm to remind the staff to intervene, thus ensuring charging safety. The demodulation and temperature calculation of the demodulation analyzer are both conventional techniques in the art and not the innovation points of this invention, so they will not be elaborated here.

[0084] The driverless vehicle 6 checks the internal temperature of the battery packs of all buses in sequence, and then continuously repeats the above cycle. Only 1 or a small number of driverless vehicles 6 can achieve periodic inspection of the battery pack temperatures of all buses in the centralized charging site, greatly saving costs.

[0085] The non-contact fiber optic sensing system and method proposed in this invention achieve innovation in wireless communication between the active demodulation analyzer and the passive fiber grating sensor several meters away. This is due to the fact that spatial light is transmitted in the form of parallel laser beams, and the communication between the two fiber collimators has low requirements for distance. Even if the distance fluctuates within the range of 3 to 10 meters, effective communication can still be achieved. Particularly prominent is the four-axis adjustment ability equipped by the second fiber collimator, which significantly reduces the positioning accuracy requirements of the movable carrier carrying the active demodulation analyzer when approaching the object to be measured. Specifically, the parking position of the carrier only needs to be roughly aligned (for example, about 5 meters away from the front of the object to be measured, and an error of ±0.1 meters in the y-axis and z-axis directions is acceptable). This flexibility is of great value in various special application scenarios. Especially in the power industry, this technology can achieve non-contact and long-distance monitoring of high-voltage wires, including wire deformation and temperature measurement, thus effectively avoiding the risk of electric shock to operators and equipment, demonstrating its great potential in improving operation safety and efficiency.

[0086] It should be understood that those of ordinary skill in the art can make improvements or modifications based on the above description, and all such improvements and modifications shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A non-contact fiber optic sensing system comprising a passive fiber grating (FBG) sensor and an active demodulation analyzer, wherein the passive fiber grating (FBG) sensor comprises an optical fiber and a fiber grating sensor serially connected to the optical fiber, and the active demodulation analyzer comprises a laser light source, an optical circulator, and the demodulation analyzer; characterized in that: The passive fiber Bragg grating sensor is arranged on the object to be detected, and one end of the passive fiber Bragg grating sensor is connected to a first fiber collimator; The active demodulation analyzer is disposed on a movable carrier and further includes a second fiber collimator and an alignment mechanism. A laser light source is connected to a first end of the optical circulator for outputting an optical signal. An optical fiber extending from a second end of the optical circulator is connected to the second fiber collimator. The second fiber collimator is configured to be non-contactly aligned with the first fiber collimator under adjustment by the alignment mechanism to enable bidirectional transmission of optical signals. The demodulation analyzer is connected to a third end of the optical circulator. The first optical fiber collimator is externally connected to a metal disk, the metal disk and the beam axis of the first optical fiber collimator being perpendicular to each other; the metal disk is arranged at the end of the object to be detected; The alignment mechanism includes an image acquisition unit and a motion platform; wherein, The image acquisition unit is a 3D industrial camera fixed to the motion platform and used to identify the position of the first fiber collimator. Specifically, the three-dimensional point cloud of the metal disk and the first fiber collimator is collected, and the plane equation of the metal disk and the spatial position of the first fiber collimator are obtained through a visual matching algorithm. A ray perpendicular to the plane equation starting from the spatial position of the first fiber collimator is calculated. This ray is the optical axis position of the first fiber collimator. The motion platform is used to adjust the beam axis of the second optical fiber collimator to be aligned with the beam axis of the first optical fiber collimator; The first optical fiber collimator and the second optical fiber collimator are both used to amplify the optical signal to form parallel light transmission.

2. The non-contact optical fiber sensing system according to claim 1, characterized in that: The motion platform is a four-axis platform used for adjustment in the four directions of y, z, θy, and θz; where z is the vertical direction, y is the horizontal direction and is perpendicular to the direction of the laser emitted from the second fiber collimator, θy is the pitch angle on the horizontal plane, and θz is the yaw angle on the vertical plane.

3. The non-contact optical fiber sensing system according to claim 2, wherein: The motion platform includes a box body, a two-dimensional linear module and a dual-axis galvanometer; wherein, The biaxial galvanometer and the second fiber collimator are respectively fixed in the box body. The biaxial galvanometer includes a reflector and two rotation axes for adjusting the reflector's angles in the θy and θz directions. The light passing through the second fiber collimator is reflected by the reflector and then output to form the second beam axis of the second fiber collimator. The box body is fixed to the moving end of the two-dimensional linear module, and the two-dimensional linear module is used to control the movement of the second light beam axis of the second optical fiber collimator in the z direction and the y direction.

4. The non-contact optical fiber sensing system according to claim 1, wherein: The object to be detected is a bridge, a building, a road, a transmission cable or a new energy vehicle battery pack.

5. The non-contact optical fiber sensing system according to claim 1, wherein: The movable carrier is a drone or an unmanned vehicle; the alignment mechanism is controlled and adjusted by a control unit in the movable carrier.

6. A sensing method for the non-contact optical fiber sensing system according to claim 1, characterized in that: The following steps are involved: S1. The movable carrier moves to within a certain distance of the object to be detected; S2. Obtain the optical axis position of the first fiber collimator. Specifically, obtain a three-dimensional point cloud of the metal disk and the first fiber collimator by taking photos with a 3D industrial camera, obtain the plane equation of the metal disk and the spatial position of the first fiber collimator by a visual matching algorithm, and calculate a ray perpendicular to the plane equation starting from the spatial position of the first fiber collimator. This ray is the optical axis position of the first fiber collimator. S3, adjusting the position and angle of the second optical fiber collimator so that the second optical fiber collimator is non-contactly aligned with the first optical fiber collimator; S4. The optical signal emitted by the laser light source is transmitted to the first optical fiber collimator in natural space after passing through the circulator and the second optical fiber collimator. The optical signal reflected back by the optical fiber Bragg grating sensor in the passive optical fiber Bragg grating sensor is transmitted to the second optical fiber collimator in natural space after passing through the first optical fiber collimator, and then reaches the demodulation analyzer for demodulation through the circulator.

7. The sensing method according to claim 6, wherein: The S3 specifically includes: S31. According to the optical axis position of the first fiber collimator, adjust the movement in the y and z directions using a two-dimensional linear module so that the beam axis of the first fiber collimator passes through the center of the reflector of the dual-axis galvanometer; S32. Control the laser light source to emit a light signal, adjust the angles of the two rotation axes of the dual-axis galvanometer so that the reflector deflects within a certain range to form a scanning operation of the dual-axis galvanometer, and the light signal output from the second fiber collimator scans back and forth within the scanning area of the galvanometer. When the axis of the light beam emitted from the second fiber collimator coincides with the axis of the light beam of the first fiber collimator, the second fiber collimator is non-contactly aligned with the first fiber collimator. The two rotation axes are used to adjust the angles of the reflector in the θy and θz directions respectively; The z direction is the vertical direction, the y direction is the horizontal direction and is perpendicular to the direction of the laser emitted from the second optical fiber collimator, θy is the pitch angle on the horizontal plane, and θz is the yaw angle on the vertical plane.

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