A device for detecting the opening of a door of an optical fiber distribution box

Abstract

The present disclosure relates to a device for detecting the opening of a door of an optical fiber splitter box. A device for detecting the opening of a door of an optical fiber splitter box is provided, comprising: a movable rod, which is coupled to the box body of the optical fiber splitter box through a first recovery device, wherein a first optical fiber in the optical fiber splitter box is attached to the movable rod; and a detector, which is configured to detect the optical attenuation value on the first optical fiber, and judge whether the door is opened according to the change in the optical attenuation value on the first optical fiber; wherein, when the door of the optical fiber splitter box is closed, the door presses the movable rod into the optical fiber splitter box, the first recovery device is in a compressed state, and the first optical fiber is in an original state; when the door of the optical fiber splitter box is opened, the first recovery device is in a recovery state, the movable rod pops out of the optical fiber splitter box, and drives the first optical fiber to bend with a certain bending radius, wherein the larger the bending radius of the optical fiber, the larger the change in the optical attenuation value.

Description

Technical Field

[0001] The present disclosure generally relates to the field of optical fiber communication, and more particularly to a device for detecting whether a door of an optical fiber splitter box is opened. Background Art

[0002] PON (Passive Optical Network) technology is one of the best technologies for broadband access networks. In recent years, with the rapid development of the communications industry, EPON (Ethernet Passive Optical Network) and GPON (Gigabit-Capable Passive Optical Networks) technologies have been widely used.

[0003] The optical fiber distribution box (can be referred to as the optical fiber distribution box) is an interface device used to connect the trunk optical cable and the distribution optical cable outdoors, in the corridor or indoors, and to place the optical splitter. The optical cable junction box (can be referred to as the optical junction box) is a junction device that provides optical fiber termination and jumper connection for the trunk layer optical cable and the distribution layer optical cable.

[0004] The doors or covers (hereinafter referred to as covers) of optical fiber distribution boxes, optical cross-connection boxes and other equipment are currently partially open for various reasons. If the covers (doors) are opened for a long time, it will not only cause safety hazards such as damage, but also directly affect the service life of internal components, increase transmission light attenuation, and reduce communication quality. Due to their huge number, these devices may bring a series of management problems, such as wide distribution range, large number, and difficulty in supervision.

[0005] In addition, when using passive optical networks, traditional monitoring equipment will have problems such as difficulty in obtaining power. At present, the technical solutions for monitoring optical handover boxes are mostly based on IoT-based electronic locks with batteries. The common problem of such technical solutions is the high price, cost and subsequent maintenance cost, so it has not been well promoted and implemented.

[0006] Therefore, there is a need for a device capable of managing a large number of optical splitter boxes in a passive optical network. Summary of the invention

[0007] A brief overview of the disclosure is given below in order to provide a basic understanding of some aspects of the disclosure. However, it should be understood that this overview is not an exhaustive overview of the disclosure. It is not intended to identify the key or important parts of the disclosure, nor is it intended to limit the scope of the disclosure. Its purpose is simply to give some concepts about the disclosure in a simplified form as a prelude to a more detailed description given later.

[0008] According to a first aspect of the present disclosure, a device for detecting that a door of an optical fiber splitter box is opened is provided, comprising: a movable rod, which is coupled to the body of the optical fiber splitter box through a first recovery device, wherein a first optical fiber in the optical fiber splitter box is attached to the movable rod; and a detector, which is configured to detect an optical attenuation value on the first optical fiber, and to determine whether the door is opened according to a change in the optical attenuation value on the first optical fiber; wherein: when the door of the optical fiber splitter box is closed, the door presses the movable rod into the optical fiber splitter box, the first recovery device is in a compressed state, and the first optical fiber is in an original state; when the door of the optical fiber splitter box is opened, the first recovery device is in a recovery state, and the movable rod pops out of the optical fiber splitter box, driving the first optical fiber to bend with a certain bending radius, wherein the larger the bending radius of the optical fiber, the larger the change in the optical attenuation value.

[0009] The device proposed in the present disclosure is suitable for transformation at a relatively low cost under passive conditions, and can remotely monitor the opening and closing status of the door of the optical fiber distribution box, providing an effective management means, thereby achieving the purpose of improving communication quality.

[0010] Other features and advantages of the present disclosure will become more apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0012] The present disclosure may be more clearly understood from the following detailed description with reference to the accompanying drawings, in which:

[0013] Figure 1 shows an overall schematic diagram of a detection device according to an embodiment of the present disclosure;

[0014] Figure 2 shows a cross-sectional view of a detection device according to an embodiment of the present disclosure;

[0015] Figure 3 Three views of a groove of a detection device according to an embodiment of the present disclosure are shown;

[0016] Figure 4 Three views of a movable rod of a detection device according to an embodiment of the present disclosure are shown;

[0017] Figure 5 A cross-sectional view of the detection device according to an embodiment of the present disclosure when the box door is closed is shown;

[0018] Figure 6A cross-sectional view of the detection device according to an embodiment of the present disclosure is shown with the door of the box opened. DETAILED DESCRIPTION

[0019] The following detailed description is made with reference to the accompanying drawings, and the following detailed description is provided to assist in a comprehensive understanding of the various exemplary embodiments of the present disclosure. The following description includes various details to assist in understanding, but these details are considered to be examples only and not to limit the present disclosure, which is defined by the appended claims and their equivalents. The words and phrases used in the following description are only used to enable a clear and consistent understanding of the present disclosure. In addition, for the sake of clarity and brevity, descriptions of well-known structures, functions, and configurations may be omitted. Those of ordinary skill in the art will recognize that various changes and modifications may be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0020] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0021] In a PON optical network, the optical signal is emitted from the light-emitting end, usually through long-distance optical fiber transmission and flange, multi-level splitter and other jumper connections, and finally received by the light receiving end. The losses in the whole process include the transmission loss of the optical fiber itself, the loss of flange jumper connection, the splitting loss, the loss caused by excessive bending and breakage of the light, etc. The optical attenuation value can be used to represent the loss on the optical fiber, and the optical attenuation value can be calculated as the difference between the power value sent by the optical fiber at the central office and the power value received at the user end.

[0022] The light beam cannot satisfy the total internal reflection condition in the bent optical fiber, which means that part of the light beam will escape from the core of the optical fiber. Therefore, the power reaching the receiving end is less than the power emitted from the light emitting end. That is, the bending of the optical fiber will cause power loss. The present disclosure uses this point to detect whether the door of the optical fiber distribution box is open.

[0023] Figure 1 FIG. 1 shows an overall schematic diagram of a detection device according to an embodiment of the present disclosure. Figure 1 As shown in FIG. 1 , the housing 10 of the detection device can be fixed in the optical fiber splitting box, for example, fixed on the bottom plate of the box body 12 of the optical fiber splitting box. The detected user optical fiber 5 can be connected in series through the connecting flange 7 .

[0024] When the door 11 of the optical fiber splitting box is closed, the door 11 presses the movable rod 2 to move toward the inside of the box body 12. When the door 11 of the optical fiber splitting box is opened, the movable rod 2 will pop out of the box body 12.

[0025] Figure 2 FIG. 4 shows a cross-sectional view of a detection device according to an embodiment of the present disclosure. Figure 2 As shown, the detection device may include a groove 1 , a movable rod 2 and a first recovery device 3 .

[0026] The groove 1 can be fixed to the housing 10 of the detection device, or can be a part of the housing 10 of the detection device. When the door 11 is opened, the optical fiber 5 can be driven by the movable rod 2 to press into the groove 1, and the bending radius of the optical fiber is defined by the bending radius in the groove 1. Figure 2 As shown in the figure, the groove 1 may include two sections with different bending radii. When the door is opened, the optical fiber 5 pressed into the groove 1 by the movable rod 2 may be bent with different bending radii, thereby generating different optical attenuation values.

[0027] As a non-limiting example, the three-view diagram of the groove 1 can be as follows: Figure 3 As shown, the groove 1 can be composed of two semi-cylindrical grooves with different radii, and a perforation is provided in the groove for the movable rod 2 to pass through. For example, the two semi-cylinders can be set to have radii of approximately 5 mm and 7.5 mm, respectively. According to actual measurements, a change in the optical attenuation value of approximately 0.3-1.0 dB can be generated in the optical fiber. The specific value of the curvature radius of the groove can be set to other values ​​as needed. In addition, the specific value of the change in the optical attenuation value may also vary according to different optical fiber manufacturers and construction processes.

[0028] The movable rod 2 can be coupled to the housing 10 of the detection device through the first restoration device 3. Since the device is fixed in the box 12, the movable rod 2 can be coupled to the box 12 of the optical fiber distribution box through the first restoration device 3. Figure 2 As shown in , one end of the movable rod 2 is located inside the shell 10 and is attached with the optical fiber 5, and the other end can be located outside the shell 10. In an embodiment according to the present disclosure, the contour of the end of the movable rod 2 inside the shell 10 and attached with the optical fiber 5 can be matched with the contour of the groove 1 to better define the bending radius of the optical fiber 5 pressed into the groove 1, thereby more accurately defining the change in the light attenuation value caused by the bending of the optical fiber. When the door 11 is closed, the end of the movable rod 2 that can be located outside the shell 10 can be against the door 11; when the door 11 is opened, the movable rod 2 can use the force provided by the first restoring device 3 to move toward the outside of the box body 12. In an embodiment according to the present disclosure, as Figure 2 As shown, the movable rod 2 may also have a flange, through which the first restoring device 3 may be coupled to the movable rod 2 and provide force to the movable rod 2. The movable distance of the movable rod 2 may be limited by the distance between the flange and the wall of the housing 10, thereby avoiding damage to the optical fiber caused by excessive movement of the movable rod 2.

[0029] As a non-limiting example, the three-view drawing of the movable rod 2 can be as follows: Figure 4As shown, one end of the optical fiber 5 attached may be composed of two semi-cylinders with different radii, which can drive the optical fiber 5 to bend with different bending radii when the box door is opened, thereby generating different light attenuation values.

[0030] Figure 2 In the figure, the first restoring device 3 is shown as a compression spring. However, the first restoring device 3 may not be limited thereto, and may be, for example, other devices using materials capable of elastic deformation, such as an elastic plate, or other devices capable of compression and restoration, such as a gas spring.

[0031] Figure 5 A cross-sectional view of the detection device according to an embodiment of the present disclosure is shown when the door is closed. When the door 11 is closed, the door 11 presses the movable rod 2 into the box body 12 of the optical fiber splitter box. At this time, the first recovery device 3 is in a compressed state, and the optical fiber 5 is in an original state.

[0032] Figure 6 A cross-sectional view of the detection device according to an embodiment of the present disclosure is shown when the box door is open. When the box door 11 is opened, the first recovery device 3 is in a recovery state, and the movable rod 2 pops out of the box body 12 of the optical fiber splitter box, driving the optical fiber 5 to bend at a certain bending radius. Moreover, the larger the bending radius of the optical fiber, the greater the change in the optical attenuation value.

[0033] The detection device may further include a second restoring device 4. The second restoring device 4 may be configured to keep the optical fiber 5 in an original state when the box door 11 is closed. When the box door 11 is opened, since the movable rod 2 applies force to the optical fiber 5 to press the optical fiber 5 into the groove 1, the second restoring device 4 may be stretched as the optical fiber 5 bends.

[0034] exist Figure 5 and Figure 6 In the figure, the second restoring device 4 is shown as a restoring spring. However, the second restoring device 4 may not be limited thereto, and may be other devices that restore the optical fiber 5 to its original state without external force, such as a tube made of elastic material.

[0035] The detection device may further include a positioning card 6 located on the movable rod 2. The positioning card 6 may be configured to limit the position of the optical fiber 5 relative to the movable rod 2. For example, the positioning card 6 may be configured to make the optical fiber 5 perpendicular to the central axis of the cylindrical movable rod 2. The positioning card 6 may be useful for limiting the bending radius of the optical fiber 5 in two situations: when the door 11 is closed and when the door 11 is opened, so that the change of the optical attenuation value in these two states is relatively fixed.

[0036] In addition, the detection device further comprises a detector, which can detect the light attenuation value on the optical fiber 5 and determine whether the box door 11 is opened according to the change in the light attenuation value on the optical fiber 5 .

[0037] In the case of using one optical fiber for detection, it is possible to determine whether the door 11 is open based on the change in the optical attenuation value on the optical fiber. In an embodiment according to the present disclosure, if the change in the optical attenuation value on the optical fiber is detected to be equal to the first reference value, it is determined that the door 11 is open. The first reference value may be preset or obtained by on-site measurement when the detection device is installed in the optical fiber splitter box. The first reference value may be stored in the detector corresponding to the data of the optical fiber, or may be stored in the memory of the detection system.

[0038] It is also possible to use two optical fibers for detection, and the second optical fiber can be attached to the movable rod 2 at a different position than the first optical fiber. Figure 2 In the embodiment shown, the first optical fiber and the second optical fiber can be attached to two semi-cylinders with different radii at the ends of the movable rod 2, respectively. Similarly, in the embodiment according to the present disclosure, the second optical fiber can be covered with a second recovery device 4. The second recovery device 4 can be configured to keep the second optical fiber in an original state when the door 11 is closed. In addition, in the embodiment according to the present disclosure, the positioning card 6 can be used to limit the position of the second optical fiber relative to the movable rod 2.

[0039] Similar to what has been described above, in the case of using two optical fibers, when the box door 11 is closed, the second optical fiber is in its original state; when the box door 11 is opened, the movable rod 2 drives the second optical fiber to bend with a bending radius different from that of the first optical fiber. The detector can be configured to detect the optical attenuation values ​​on the first optical fiber and the second optical fiber, and determine whether the box door 11 is open based on the amount of change in the optical attenuation values ​​on the first optical fiber and the second optical fiber. If it is detected that the amount of change in the optical attenuation values ​​on the first optical fiber and the second optical fiber is equal to the first reference value and the second reference value, respectively, it is determined that the box door 11 is open. Similarly, the second reference value can be preset, or it can be obtained by performing on-site measurements when the detection device is installed in the optical fiber splitter box. The second reference value can be stored in the detector corresponding to the data of the second optical fiber, or it can be stored in the memory of the detection system.

[0040] In an embodiment according to the present disclosure, the detector may be configured to detect the door status of multiple optical fiber splitter boxes. The detector may poll and detect the optical attenuation values ​​of the optical fibers in the multiple optical fiber splitter boxes at a certain period, and determine whether they meet certain rules to detect the door status. The detection period is determined, for example, according to the number of optical fiber splitter boxes to be detected. For example, all optical fiber splitter boxes to be detected may be detected every 10 minutes, and the latest optical attenuation values ​​of the associated optical fibers may be saved.

[0041] In an embodiment according to the present disclosure, an anti-jitter strategy may also be adopted. After detecting that the amount of change in the optical attenuation value on the first optical fiber and the second optical fiber is equal to the first reference value and the second reference value, respectively, the amount of change in the optical attenuation value on the first optical fiber and the second optical fiber is detected multiple times at predetermined time intervals. If the amount of change in the optical attenuation value on the first optical fiber and the second optical fiber is still equal to the first reference value and the second reference value, respectively (reasonable deviations are allowed), it is determined that the door is open. For example, if it is found within 10 minutes that the amount of change in the optical attenuation value of the optical fiber of two designated users in a certain optical fiber splitter box meets the conditions, it is determined that the door of the fiber splitter box is suspected to be open. In order to prevent occasional false jitters, it is judged again every 30 seconds after the discovery. If the conditions are still met after 3 detections and judgments, it is judged that the door of the fiber splitter box is open.

[0042] It should be noted that factors such as weather, wind direction and volume, and external construction may cause a certain degree of change in the optical path. In the embodiment according to the present disclosure, after recording the current latest difference in each cycle, the following judgment can be made:

[0043] If one of the optical attenuation values ​​A and B of the two optical fibers in the optical fiber splitter box to be tested changes, it can be considered that the attenuation is caused by a certain optical fiber from the optical fiber splitter box to the user's home;

[0044] If the optical attenuation values ​​A and B of the two optical fibers change, and the optical attenuation values ​​A and B of the two optical fibers increase or decrease by approximately the same amount, it can be considered that the uplink optical path of the optical splitter associated with the optical splitter box has changed;

[0045] If the optical attenuation values ​​A and B of the two optical fibers both change, but the change amount does not meet the specified conditions, for example, the change amount of the optical attenuation value A is not equal to the first reference value or the change amount of the optical attenuation value B is not equal to the second reference value, it can be considered that the optical fibers of the downstream users have changed to a certain extent;

[0046] If the changes in the optical attenuation values ​​A and B of the two optical fibers meet the specified requirements, such as the change in the optical attenuation value A is equal to the first reference value and the change in the optical attenuation value B is equal to the second reference value (reasonable deviations are allowed), for example, for a device in which the grooves are set to have bending radii of approximately 5 mm and approximately 3 mm, the change in the optical attenuation value A is equal to approximately 0.8 dB, the change in the optical attenuation value B is equal to approximately 0.3 dB, and after multiple anti-shake processing, it can be determined that the door is open.

[0047] In summary, according to the first aspect of the present disclosure, a device for detecting that a door of an optical fiber splitter box is opened is provided, comprising: a movable rod, which is coupled to the box body of the optical fiber splitter box through a first recovery device, wherein the first optical fiber in the optical fiber splitter box is attached to the movable rod; and a detector, which is configured to detect the optical attenuation value on the first optical fiber, and judge whether the door is opened according to the change in the optical attenuation value on the first optical fiber; wherein: when the door of the optical fiber splitter box is closed, the door presses the movable rod into the optical fiber splitter box, the first recovery device is in a compressed state, and the first optical fiber is in an original state; when the door of the optical fiber splitter box is opened, the first recovery device is in a recovery state, and the movable rod pops out of the optical fiber splitter box, driving the first optical fiber to bend with a certain bending radius, wherein the larger the bending radius of the optical fiber, the greater the change in the optical attenuation value.

[0048] In some embodiments, a second optical fiber in the optical fiber splitter box is attached to the movable rod at a position different from that of the first optical fiber; and the detector is also configured to detect the optical attenuation value on the second optical fiber, and determine whether the box door is open based on the change in the optical attenuation values ​​on the first optical fiber and the second optical fiber; wherein: when the box door of the optical fiber splitter box is closed, the second optical fiber is in an original state; when the box door of the optical fiber splitter box is opened, the movable rod drives the second optical fiber to bend with a bending radius different from that of the first optical fiber.

[0049] In some embodiments, the device further comprises a groove. When the door of the optical fiber splitter box is opened, the optical fiber is driven by the movable rod to be pressed into the groove. The bending radius of the optical fiber is defined by the bending radius in the groove.

[0050] In some embodiments, the optical fiber is attached to an end of the movable rod, and the profile of the end matches the profile of the groove.

[0051] In some embodiments, the device further comprises a second restoration device sleeved on the two optical fibers, wherein the second restoration device is configured to restore the optical fibers to an original state when the box door is closed.

[0052] In some embodiments, the device further comprises a positioning card located on the movable rod, wherein the positioning card is configured to limit a position of the optical fiber relative to the movable rod.

[0053] In some embodiments, if it is detected that the change in the optical attenuation value on the first optical fiber is equal to a first reference value, it is determined that the door is open.

[0054] In some embodiments, if it is detected that the changes in the optical attenuation values ​​on the first optical fiber and the second optical fiber are respectively equal to the first reference value and the second reference value, it is determined that the door is open.

[0055] In some embodiments, the first reference value and the second reference value are obtained by measuring when the device is installed in an optical fiber splitter box.

[0056] In some embodiments, after detecting that the change in the optical attenuation values ​​on the first optical fiber and the second optical fiber is respectively equal to the first reference value and the second reference value, the change in the optical attenuation values ​​on the first optical fiber and the second optical fiber is detected multiple times at predetermined time intervals, and if the change in the optical attenuation values ​​on the first optical fiber and the second optical fiber is still respectively equal to the first reference value and the second reference value, it is determined that the box door is open.

[0057] In some embodiments, the optical attenuation value on the optical fiber is the difference between the power value sent by the optical fiber at the central office and the power value received by the optical fiber at the user end.

[0058] The detection device according to the present disclosure may have the following advantages:

[0059] First, under the condition of passive optical network, the change of optical attenuation characteristics caused by physical deformation is used as a detection method, which is low-cost and easy to implement.

[0060] Second, by setting multiple conditions, the software and hardware work together to improve the reliability of detection. By simultaneously detecting the optical fibers of two different paths, the misjudgment caused by the light attenuation change of a single downlink can be avoided; changes can be made simultaneously within the same detection cycle; two deformation curvatures are used in one detection unit to produce different light attenuation changes, and the two optical paths being detected must meet the specified range of changes.

[0061] Third, it does not cause permanent damage to the optical fiber in the optical fiber distribution box. The optical fiber is in a normal state when the box door is closed, and the optical fiber is bent only when the box door is opened, which can reduce the bending time; the movable rod end with a certain bending radius and the groove are set, so that the optical fiber has a fixed bending radius when bending; a second recovery device is set at the bending part of the optical fiber, which can help the optical fiber return to its original state when the second recovery device is restored.

[0062] The subject matter of the present disclosure is provided as an example of an apparatus, system, and method for performing the features described in the present disclosure. However, in addition to the above-mentioned features, other features or variations may also be expected. It is expected that the implementation of the components and functions of the present disclosure may be accomplished with any emerging technology that may replace any of the above-mentioned implementation technologies.

[0063] In addition, the above description provides examples without limiting the scope, applicability or configuration set forth in the claims. Without departing from the spirit and scope of the present disclosure, the functions and arrangements of the elements discussed may be changed. Various embodiments may appropriately omit, replace or add various processes or components. For example, features described with respect to certain embodiments may be combined in other embodiments.

[0064] Similarly, while operations are depicted in a particular order in the drawings, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed to achieve desired results. In certain circumstances, multitasking and parallel processing can be advantageous.

Claims

1. A device for detecting that a door of an optical fiber splitter box is opened, comprising: A movable rod, the movable rod being coupled to the box body of the optical fiber splitter box through a first recovery device, wherein a first optical fiber in the optical fiber splitter box is attached to the movable rod, and a second optical fiber in the optical fiber splitter box is attached to the movable rod at a position different from that of the first optical fiber; and a detector configured to detect an optical attenuation value on the first optical fiber and an optical attenuation value on the second optical fiber, and to determine whether the door is opened according to a change in the optical attenuation value on the first optical fiber and the optical attenuation value on the second optical fiber; in: When the door of the optical fiber splitter box is closed, the door presses the movable rod into the optical fiber splitter box, the first recovery device is in a compressed state, the first optical fiber is in an original state, and the second optical fiber is in an original state; When the door of the optical fiber splitter box is opened, the first recovery device is in a recovery state, the movable rod pops out of the optical fiber splitter box, driving the first optical fiber to bend at a certain bending radius, and the movable rod drives the second optical fiber to bend at a bending radius different from that of the first optical fiber, wherein the larger the bending radius of the optical fiber, the greater the change in the optical attenuation value.

2. The device according to claim 1 further comprises a groove, and when the box door of the optical fiber splitter box is opened, the optical fiber is driven by the movable rod to be pressed into the groove, and the bending radius of the optical fiber is limited by the bending radius in the groove.

3. The device according to claim 2, wherein: An optical fiber is attached to the end of the movable rod, the profile of the end matching the profile of the groove.

4. The device according to claim 1 further comprises a second recovery device sleeved on the two optical fibers, wherein the second recovery device is configured to restore the optical fibers to their original state when the cabinet door is closed.

5. The apparatus according to claim 1, further comprising a positioning card located on the movable rod, wherein the positioning card is configured to limit the position of the optical fiber relative to the movable rod.

6. The device according to claim 1, wherein: If it is detected that the changes in the optical attenuation values ​​on the first optical fiber and the second optical fiber are respectively equal to the first reference value and the second reference value, it is determined that the door is opened.

7. The device according to claim 6, wherein: The first reference value and the second reference value are obtained by measuring when the device is installed in an optical fiber splitter box.

8. The device according to claim 6, wherein: After detecting that the changes in the optical attenuation values ​​on the first optical fiber and the second optical fiber are respectively equal to the first reference value and the second reference value, the changes in the optical attenuation values ​​on the first optical fiber and the second optical fiber are detected multiple times at predetermined time intervals. If the changes in the optical attenuation values ​​on the first optical fiber and the second optical fiber are still respectively equal to the first reference value and the second reference value, it is determined that the box door is open.

9. The device according to claim 1, wherein: The optical attenuation value on the optical fiber is the difference between the power value sent by the optical fiber at the central office and the power value received at the user end.

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