Optical fiber calibration method

Abstract

The invention relates to an optical fiber calibration method. The optical fiber calibration method comprises the following steps: a reference position setting step: acquiring a map in a mine and setting a plurality of reference positions in the map; a test light output step of emitting test light for the optical fiber laid in the mine; a test sound emission step of emitting a test sound on the optical fiber laid at the reference position or at a position near the optical fiber at the reference position; a time acquisition step: acquiring the transmission time of transmitting the optical signal carrying the information of the test sound to the starting end of the optical fiber; and a storage step: correspondingly storing the serial number of the optical fiber, the transmission time and / or the length of the optical fiber corresponding to the transmission time, and the reference position. According to the optical fiber calibration method, accurate calibration can be realized through the optical fiber, and the position of the personnel in the mine can be quickly determined during rescue.

Description

Technical Field

[0001] This invention relates to the technical field of mine rescue, and more particularly to a method for optical fiber calibration in mines. Background Technology

[0002] Laying fiber optic cables within mines is a necessary measure to ensure safe production and improve management efficiency. Fiber optics offer advantages such as resistance to electromagnetic interference, long transmission distances, and high bandwidth, providing a stable and reliable data transmission channel for systems such as underground video surveillance, personnel identification, environmental monitoring, and communication dispatch. Through fiber optic networks, the occurrence of disasters can be monitored in real time. Compared to traditional cables, fiber optic transmission is more stable and has lower maintenance costs, making it a crucial infrastructure for achieving safe production. Summary of the Invention

[0003] This invention provides an optical fiber calibration method that enables accurate calibration of optical fibers, allowing for rapid determination of the location of personnel in mines during rescue operations.

[0004] In a first aspect, embodiments of the present invention provide an optical fiber calibration method, the method comprising: a reference position setting step, acquiring a map in a mine and setting multiple reference positions in the map; a test light output step, emitting test light for an optical fiber laid in the mine; a test tone emission step, emitting a test tone at a location on or near the optical fiber laid at the reference position; a time acquisition step, acquiring the transmission time of an optical signal carrying information of the test tone to the beginning of the optical fiber; and a storage step, storing the optical fiber number, the transmission time and / or the length of the optical fiber corresponding to the transmission time, and the corresponding reference positions.

[0005] The fiber calibration method described above also includes a calculation step, which calculates the length of the fiber based on the transmission time.

[0006] According to the above fiber optic calibration method, the reference position refers to the name of the reference position and / or the three-dimensional coordinates of the reference position in a preset coordinate system.

[0007] According to the above-mentioned fiber optic calibration method, it also includes a three-dimensional coordinate acquisition step, which establishes a correspondence between each location in the mine and a pre-established three-dimensional coordinate system to obtain the three-dimensional coordinates of the reference location and other locations in the map.

[0008] According to the fiber optic calibration method described above, in the three-dimensional coordinate acquisition step, three-dimensional positioning of each region is achieved by using short-range communication based on electromagnetic field coupling technology or ZigBee wireless sensor network.

[0009] According to the fiber optic calibration method described above, in the three-dimensional coordinate acquisition step, Bluetooth or inertial sensors are used to achieve three-dimensional positioning at each location.

[0010] According to the above-described fiber optic calibration method, a verification step is also included: the test tone is emitted for any of the reference positions of the fiber optic cables; if the detected position of the fiber optic cable emitting the test tone corresponds to the reference position, the test is deemed qualified; if the detected position of the fiber optic cable emitting the test tone does not correspond to the reference position, the fiber optic cable is recalibrated.

[0011] The fiber optic calibration method described above also includes a display step, in which, during the verification, the location where the test sound was detected is visually displayed on the map using a display device.

[0012] According to the above-described optical fiber calibration method, the optical fiber utilizes a distributed acoustic sensing system based on Rayleigh scattering.

[0013] According to the fiber optic calibration method described above, the verification is performed at predetermined intervals.

[0014] The fiber optic calibration method provided by this invention enables accurate calibration via optical fiber, allowing for rapid determination of personnel locations in mines during rescue operations. Furthermore, employing three-dimensional coordinates allows for even more accurate calibration. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart of an optical fiber calibration method according to an embodiment of the present invention is shown; Figure 2 A schematic diagram of an example of optical fiber laying according to an embodiment of the present invention is shown; Figure 3 A schematic diagram illustrating an example of fiber optic signal transmission and processing according to an embodiment of the present invention is shown; Figure 4 This is a flowchart illustrating an example of regional calibration in a mine using short-range communication calibration based on electromagnetic field coupling technology; Figure 5 This is a flowchart illustrating an example of using a ZigBee wireless sensor network to achieve 3D positioning of various areas; Figure 6 This is a flowchart illustrating three-dimensional positioning using Bluetooth based on RSSI signal strength. Figure 7 This is a flowchart illustrating the use of inertial positioning to achieve three-dimensional positioning at various locations; Figure 8 A flowchart illustrating an example of the verification and calibration results involved in an embodiment of the present invention is shown. Detailed Implementation

[0017] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. 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 and embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0018] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0019] In mines, optical fibers used include grating fibers, interferometric fibers, and Rayleigh scattering-based fibers. Grating fibers work by utilizing the slight deformation of the grating caused by external sound waves, which in turn alters the frequency, phase, and amplitude of the reflected light. By demodulating the corresponding parameters and employing sound reconstruction algorithms, the sound information of the environment at each grating point can be obtained. Interferometric fiber optic acoustic sensing (IFOS) is a high-sensitivity sensing technology that converts sound wave signals into measurable optical signals based on the interference effect of light and the sensing characteristics of optical fibers. The original sound wave information is then reconstructed using demodulation algorithms. Rayleigh scattering-based fibers use a single ordinary optical fiber simultaneously as both a "sensing medium" and a "transmission medium." By detecting the coherent changes in the backscattered Rayleigh light within the fiber, distributed, blind-zone-free monitoring of acoustic / vibration signals across the entire fiber length is achieved.

[0020] This invention proposes a fiber optic calibration method before the use of optical fibers. In this invention, the fiber optic calibration method refers to a method of mapping the fiber optic cable's laying location to its position within the mine to achieve accurate fiber positioning. Fiber optic calibration is the process of mapping the actual position of the fiber optic cable to the monitored position, that is, associating the distance on the fiber optic cable with the actual position. In this invention, the system performs calibration based on reference objects, at least associating key locations within the mine with the corresponding distances of the optical fibers, thus achieving calibration.

[0021] Figure 1 A flowchart of an optical fiber calibration method according to an embodiment of the present invention is shown. The optical fiber calibration method includes: a reference position setting step S1, acquiring a map of a mine and setting multiple reference positions in the map; a test light output step S2, emitting test light for an optical fiber laid in the mine; a test tone emission step S3, emitting a test tone on an optical fiber laid at or near the reference position; a time acquisition step S4, acquiring the transmission time of the optical signal carrying the test tone information to the beginning of the optical fiber; and a storage step S5, storing the optical fiber number, the transmission time, / or the length of the optical fiber corresponding to the transmission time, and the corresponding reference positions.

[0022] Figure 2 A schematic diagram illustrating an example of optical fiber laying according to an embodiment of the present invention is shown. (In conjunction with...) Figure 1 and Figure 2 The fiber optic calibration method is explained.

[0023] Each mine has its own internal structure map. This map describes the specific structure within the mine tunnels. The map can mark the coordinates of key areas within a preset coordinate system. For example, the main entrance of the mine can be set as the origin of the coordinate system, the east-west horizontal direction of the entrance as the X-axis, the north-south horizontal direction as the Y-axis, and the vertical direction as the Z-axis. The mine includes refuge chambers, connecting tunnels, electromechanical tunnels, safety chambers, substations, retreat passages, power distribution chambers, auxiliary retreat tunnels, and permanent refuge chambers. These locations can be used as reference points, i.e., reference objects, to pre-determine the three-dimensional coordinates of each reference location along the X, Y, and Z axes. The setting of the coordinate system is not particularly limited and can be determined based on the actual scenario.

[0024] exist Figure 2 In the diagram, A is the entrance to mine K, and optical fiber S is laid along the mine shaft inwards. This illustration shows the optical fiber branching into various mine shafts, but it is not limited to this; a single optical fiber can also be laid by meandering through different locations. K1 and K2 in the diagram are reference locations within the mine, with clearly defined coordinates on the mine map.

[0025] Figure 3 This diagram illustrates an example of fiber optic signal transmission and processing according to an embodiment of the present invention. The fiber optic signal transmission detection system 100 includes a laser pulse generation unit 1, an optical circuit unit 2, a signal processing and control unit 3, and an output unit 4. During calibration, the laser pulse generation unit 1 emits test light to a fiber optic cable laid in a mine. The optical circuit unit 2 outputs the test light to the fiber optic cable. Workers emit a test tone at a location on or near the fiber optic cable at a reference location and record the time of emission. The fiber optic cable senses the sound signal, affects the transmitted light, and can feed back the light signal carrying the test tone information to the optical circuit unit 2. The signal processing and control unit 3 can obtain the transmission time of the light signal carrying the test tone information to the beginning of the fiber optic cable based on the time of emission of the test tone and the time of receiving its feedback signal. Upon obtaining this transmission time, the fiber optic cable number, the measured transmission time, and the reference location can be stored accordingly. The output unit 4 can be a display that outputs the stored table processed by the signal processing and control unit 3 in a displayable manner. After the fiber optic cable is laid, tap the fiber optic cable at the reference location and check the tapping location at the host controller containing output unit 4.

[0026] As an optional embodiment, the fiber calibration method further includes a calculation step to calculate the length of the fiber based on the aforementioned transmission time. The signal processing and control unit 3 also calculates the fiber length based on the transmission time and the speed of light. In the aforementioned storage step, instead of the transmission time, the fiber number, the fiber length corresponding to the transmission time, and the aforementioned reference position can be stored accordingly. Alternatively, the fiber number, the aforementioned transmission time, the fiber length corresponding to the transmission time, and the aforementioned reference position can also be stored accordingly.

[0027] Here, the aforementioned reference position can be the specific name of the reference object, the three-dimensional coordinates of each reference object, or both.

[0028] The above operations can be used to calibrate the optical fiber, thereby accurately determining the location in the mine represented by the returned optical fiber signal.

[0029] The above explains the calibration of reference positions in a mine. However, if an optical fiber passes through multiple reference positions, and the distance between these reference positions is large, the reference positions can also be used as a benchmark to calibrate the optical fibers between them. Figure 2For example, after calibrating the optical fibers at reference positions K1 and K2, since reference positions K1 and K2 are relatively far apart, it is desirable to calibrate the optical fibers between them. That is, the optical fiber calibration can be performed at predetermined distances from the reference object. This can be accomplished in the following two ways.

[0030] One approach is to pre-obtain the three-dimensional coordinates of the location to be calibrated on the mine map, that is, to find the optical fiber at that location based on the three-dimensional coordinates of the location to be calibrated, and then... Figure 1 The fiber optic cable is calibrated using the method described above for calibrating the fiber at the reference position; detailed explanations are omitted here. In this method, after obtaining the transmission time, the fiber number, transmission time, and / or the fiber length corresponding to the transmission time, as well as the three-dimensional coordinates of that position, can be stored accordingly.

[0031] Another method is to calibrate the optical fiber using the offset of other locations relative to a reference location. First, the offset coordinates of other locations relative to the reference location are obtained from the mine map. For example, if the coordinates of the reference location are (X1, Y1, Z1), then the offset (a1, b1, c1) of the other location relative to the reference location (X1, Y1, Z1) is obtained from the mine map information. A test tone is emitted on the optical fiber laid at or near the other location, and the time of emission is recorded. The optical fiber senses the sound signal and can transmit an optical signal carrying the test tone information to the optical circuit unit 2. The signal processing and control unit 3 can obtain the transmission time of the optical signal carrying the test tone information to the beginning of the optical fiber based on the time of emission and the time of receiving its feedback signal. Upon obtaining this transmission time, the optical fiber number, the measured transmission time, the reference location as a reference, and the offset coordinates of the other locations relative to the reference location can be stored accordingly. The output unit 4 can be a display, which outputs the stored table processed by the signal processing and control unit 3 in a displayable manner. The advantage of this method is that it can quickly and accurately determine the location from which the sound is emitted based on a reference position.

[0032] Based on the above, when calibrating the reference position and other positions, a three-dimensional coordinate acquisition step may also be included, which establishes a correspondence between each position in the mine and a pre-established three-dimensional coordinate system to obtain the three-dimensional coordinates of each position in the map.

[0033] In the three-dimensional coordinate acquisition step, as an example, short-range communication calibration based on electromagnetic field coupling technology is used to achieve regional-level calibration in the mine. In short-range communication positioning based on electromagnetic field coupling technology, the location association is determined by the signal interaction between the RFID tag and the reader. Workers or robots in the mine wear devices such as safety helmets and miners' lamps with built-in active / passive RFID tags. The RFID tags contained in these devices periodically broadcast radio frequency signals containing unique IDs. Integrated RFID readers are deployed at roadway intersections and key areas as location monitoring substations for identifying radio frequency signals. When a tag enters the substation's identification range, the reader captures the RFID tag's ID and combines it with its known three-dimensional coordinates, uploading the data to the ground main controller via CAN bus or industrial Ethernet. The identification range is typically 1-10 meters. The main controller, including the ground signal processing and control unit 3, binds the RFID tag's ID with the coordinates of the location monitoring substation to achieve three-dimensional positioning of the measured area. Passive RFID tags rely on the reader's electromagnetic field for power, passively emitting broadcast signals, resulting in short identification distances but low cost. Active RFID tags have built-in batteries and can actively broadcast signals. While they require periodic battery replacements, they offer a relatively long reading distance and are suitable for dusty and humid environments, such as underground mines. Optionally, the system can also obtain the signal strength difference (RSSI) between multiple monitoring stations at various locations, and use this difference to estimate the approximate offset of the RFID tag within the area.

[0034] Figure 4 This is a flowchart illustrating an example of area-level calibration in a mine using short-range communication positioning based on electromagnetic field coupling technology. In step S41, an RFID tag periodically broadcasts a radio frequency signal containing a unique ID; in step S42, the location monitoring substation receives the radio frequency signal; in step S43, the tag ID and the location monitoring substation's known coordinates are sent to the main controller; in step S44, the main controller binds the tag ID to the location monitoring substation's coordinates.

[0035] By utilizing short-range communication positioning based on electromagnetic field coupling technology to achieve three-dimensional positioning of various areas, regional-level calibration in mines can be realized.

[0036] In the three-dimensional coordinate acquisition step, as another example, the ZigBee wireless sensor network is used to achieve three-dimensional positioning at various locations.

[0037] Based on the self-organizing characteristics of Wireless Sensor Networks (WSNs), calibration is performed by combining Relative Signal Strength Indicator (RSSI) estimation with multi-node collaboration. A large number of ZigBee anchor nodes are deployed underground. These ZigBee anchor nodes are fixed locations with known three-dimensional coordinates, forming a wireless sensor network covering the tunnel. Positioning terminals worn by personnel or robots in the mine establish communication with multiple surrounding anchor nodes. By measuring the received signal strength of each anchor node, the main controller calculates the distance between the positioning terminal and the anchor node using a path loss model based on the received signal strength. Here, the main controller can use a triangulation algorithm to fuse distance data from multiple anchor nodes to calculate the three-dimensional coordinates of the terminal, achieving a positioning accuracy of 3-5 meters.

[0038] Figure 5 This is a flowchart illustrating an example of using a ZigBee wireless sensor network to achieve 3D positioning at various locations. In step S51, multiple ZigBee anchor nodes with known 3D coordinates are deployed in the underground roadway to construct a wireless sensor network covering the roadway. In step S52, the positioning terminal establishes ZigBee communication with multiple surrounding anchor nodes and measures the Received Signal Strength Indication (RSSI) of each anchor node. In step S53, the RSSI is converted into the distance between the positioning terminal and each anchor node based on a path loss model. In step S54, a triangulation algorithm is used to fuse the distance data of multiple anchor nodes to calculate the 3D coordinates of the positioning terminal.

[0039] A ZigBee wireless sensor network is used to achieve 3D positioning in various areas, with a positioning accuracy of 3-5 meters. The ZigBee anchor nodes support self-organizing networks and multi-hop transmission to cover long-distance tunnels. In addition, the multi-hop error and occlusion effects are reduced by optimizing the deployment location of the anchor nodes.

[0040] As another example in the process of obtaining three-dimensional coordinates, Bluetooth positioning can be used to achieve three-dimensional positioning of various locations.

[0041] Bluetooth calibration requires deploying Bluetooth beacons on the sidewalls and roof of mine tunnels, with known 3D coordinates of these beacons. A positioning terminal receives broadcast signals from surrounding beacons. This Bluetooth calibration method includes the RSSI signal strength method and the Time-of-Flight (ToF) algorithm. In the RSSI method, the main controller estimates the distance between the terminal and the beacon based on the RSSI signal strength using a signal attenuation model, and calculates the 3D coordinates using multi-beacon triangulation. In the ToF algorithm, the propagation time (nanosecond level) between the terminal and the beacon is measured, and the precise distance (distance = speed of light × propagation time) is calculated. Based on the distance data between the positioning terminal and multiple Bluetooth beacons, combined with the preset 3D coordinates of each Bluetooth beacon, the 3D coordinates of the positioning terminal are calculated using a triangulation algorithm, achieving a positioning accuracy of 0.5-3 meters.

[0042] Figure 6 This is a flowchart illustrating 3D positioning using Bluetooth based on RSSI signal strength. In step S61, multiple Bluetooth beacons with known 3D coordinates are deployed on the sidewalls and top of the underground tunnel to construct a calibration reference network. In step S62, the positioning terminal receives broadcast signals from the surrounding Bluetooth beacons. In step S63, the main controller calculates the distance between the terminal and each beacon based on the RSSI signal strength attenuation model or using the ToF algorithm. In step S64, the main controller uses a triangulation algorithm to fuse multiple distance data and calculate the 3D coordinates of the positioning terminal. This Bluetooth positioning method can achieve calibration at the 0.5-3 meter level. Optionally, a hybrid architecture of "Bluetooth + UWB" can be used, where Bluetooth handles coarse calibration and time slot scheduling, and UWB handles precise ranging. A single base station can support 100 concurrent terminals, and data is uploaded to the ground-based main controller via 4G / LoRa, adapting to short-range, high-precision scenarios underground.

[0043] As an example, in the process of establishing a three-dimensional coordinate system, an inertial sensor can also be used to achieve three-dimensional positioning at various locations.

[0044] Motion state perception based on inertial sensors enables positioning without external signals. The inertial sensor is a combination of an accelerometer and a gyroscope. The positioning terminal integrates an inertial sensor; the accelerometer measures the terminal's linear acceleration, and the gyroscope measures angular velocity. Combined with the initial position coordinates, the terminal's displacement, velocity, and attitude are calculated in real time through integration, thus calculating its three-dimensional position. Because inertial sensors have cumulative errors, the error increases over time when used alone. In practical applications, they are often integrated with technologies such as UWB / RFID. UWB / RFID handles calibration in areas with good signal coverage, while INS (Inertial Sensor) fills in gaps in coverage in areas without base station coverage, such as temporary tunnels and goaf areas, improving the reliability of calibration across all scenarios. As an example, the gyroscope is a fiber optic gyroscope. The core working principle of a fiber optic gyroscope is based on the Sagnac effect, where the clockwise and counterclockwise propagating beams of light in a closed optical path produce an optical path difference. By detecting the offset of the interference fringes, the rotational angular velocity can be accurately calculated, providing a basis for attitude perception. Compared to traditional mechanical gyroscopes, it has no mechanical rotating parts, significantly improving its anti-interference capability and measurement accuracy.

[0045] Figure 7It is a flowchart showing three-dimensional positioning of each position using inertial positioning. In step S71, a positioning terminal integrating an accelerometer and a gyroscope acquires an initial position coordinate, an initial velocity, and an initial attitude; in step S72, the accelerometer measures the linear acceleration of the terminal, and the gyroscope measures the angular velocity of the terminal, and the displacement, velocity, and attitude of the terminal are calculated in real time through integral operations; in step S73, combining the initial position and attitude, the three-dimensional position of the terminal is calculated to achieve autonomous positioning without external signals; in step S74, when the terminal enters the UWB / RFID signal coverage area, the UWB / RFID precise position is used to calibrate the cumulative error of the inertial sensor.

[0046] According to the above, compared with the optical cable calibration of a single coordinate, the optical cable calibration with three-dimensional coordinates can be more accurately achieved.

[0047] The above describes the calibration of optical fibers in a mine at a reference position and other positions. Figure 8 It shows an example flowchart of verifying the calibration result involved in an embodiment of the present invention. After the optical fiber in the mine is laid and initially calibrated, considering various changes in the mine, regular verification is required. Refer to Figure 2 , for example, using the reference position for verification. Randomly select the reference positions that need to be verified, such as Figure 2 the reference position K2 is the randomly selected reference position that needs to be verified. Tap the optical fiber at the reference position K2 for verification. In Figure 8 , first in step S11, a test tone is emitted on or near the optical cable at the reference position. Observe the acoustic / vibration signal at the corresponding reference object position displayed on the monitor at the main controller end. If a tapping signal is clearly identified at this reference position, that is, it is detected that the position where the test tone is emitted is consistent with the reference position, then proceed to step S13 and determine that the verification result is qualified; if a tapping signal cannot be identified at this reference position or a tapping signal is shown at other positions, that is, it is detected that the position where the test tone is emitted is inconsistent with the reference position, then proceed to step S14 and determine that the verification result is unqualified, and it is necessary to recalibrate according to the steps S2~S4 in the preliminary calibration shown in Figure 1 .

[0048] The following explanation uses Rayleigh scattering-based optical fiber calibration as an example. In Rayleigh scattering, a single ordinary optical fiber serves as both a "sensing medium" and a "transmission medium." By detecting the coherent changes in the backscattered Rayleigh light within the fiber, distributed, blind-zone-free monitoring of acoustic / vibration signals across the entire fiber length is achieved. The silica material of the optical fiber contains nanoscale refractive index inhomogeneities. When a laser beam propagates through the fiber, it collides with these inhomogeneities, generating backscattered Rayleigh light—part of the light is reflected back to the light source in the opposite direction to the incident light. When the laser emits a light signal, it is affected by the vibration of the test tone at that location, resulting in Rayleigh scattering and partial reflection back to the light source. This allows the propagation time of the light signal to be measured. Therefore, the optical fiber can be calibrated to a specific location in the mine using the method described above, based on the propagation time of the reflected light.

[0049] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0050] It should also be noted that the exemplary embodiments mentioned in this invention describe methods or systems based on a series of steps or apparatus. However, this invention is not limited to the order of the steps described above; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0051] The above description is merely a specific embodiment of the present invention. It should be understood that the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A fiber optic calibration method, characterized in that, include: The reference location setting steps involve acquiring a map of the mine and setting multiple reference locations on the map. The test light output step involves emitting test light onto the optical fiber laid in the mine. The test tone emission step involves emitting a test tone on the optical fiber laid at the reference position or at a position near the optical fiber at the reference position. The time acquisition step involves acquiring the transmission time of the optical signal carrying the test tone information to the beginning of the optical fiber. as well as The storage step involves storing the fiber number, the transmission time, / or the fiber length corresponding to the transmission time, and the reference position.

2. The optical fiber calibration method according to claim 1, characterized in that, It also includes a calculation step to calculate the length of the optical fiber based on the transmission time.

3. The optical fiber calibration method according to claim 1 or 2, characterized in that, The reference position refers to the name of the reference position and / or the three-dimensional coordinates of the reference position in a preset coordinate system.

4. The optical fiber calibration method according to claim 1, characterized in that, It also includes a three-dimensional coordinate acquisition step, which establishes a correspondence between each location in the mine and a pre-established three-dimensional coordinate system to obtain the three-dimensional coordinates of the reference location and other locations in the map.

5. The optical fiber calibration method according to claim 4, characterized in that, In the three-dimensional coordinate acquisition step, three-dimensional positioning of each location is achieved by using short-range communication based on electromagnetic field coupling technology or ZigBee wireless sensor network.

6. The optical fiber calibration method according to claim 4, characterized in that, In the three-dimensional coordinate acquisition step, Bluetooth or inertial sensors are used to achieve three-dimensional positioning at each location.

7. The optical fiber calibration method according to claim 1 or 2, characterized in that, It also includes a verification step, in which the test tone is emitted for any of the reference positions of the optical fiber, and if the detected position of the optical fiber emitting the test tone corresponds to the reference position, the test is set to pass; if the detected position of the optical fiber emitting the test tone does not correspond to the reference position, the optical fiber is recalibrated.

8. The optical fiber calibration method according to claim 7, characterized in that, It also includes a display step, in which, during the verification, the location of the optical fiber that detected the test tone is visualized on the map using a display device.

9. The optical fiber calibration method according to claim 1 or 2, characterized in that, The optical fiber utilizes a distributed acoustic sensing system based on Rayleigh scattering.

10. The optical fiber calibration method according to claim 7, characterized in that, The review is performed at predetermined intervals.

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