Passive optical network monitoring device and detection method

Abstract

The invention relates to a passive optical network monitoring device and a detection method, and the device comprises a light generation module which is used for generating pulse light with a pseudo-random sequence; the circulator is used for enabling the optical signal to go down to the optical fiber trunk and sending the reflected uplink optical signal to the reflected light analysis module at the same time; the splitter distributes the downlink optical signals to the optical network units and gathers the uplink optical signals to the optical fiber trunk at the same time; and the reflected light analysis module is used for receiving the reflected light signal and analyzing the fault position based on the reflected light signal. According to the application, the pulse light with the pseudo-random sequence is generated through the light generation module, the pulse light can reach each branch link through the circulator and the splitter, the reflection points arranged on each branch link reflect the pulse light and return to the reflected light analysis module, and then the fault position is analyzed according to the reflected light signal. According to the invention, high-precision resolution can be realized by controlling the pulsed light with the pseudo-random sequence, and the method can be used for fault detection of a point-to-multipoint network.

Description

Technical Field

[0001] The present application relates to the field of optical fiber communication technology, and in particular to a passive optical network monitoring device and a detection method. Background Art

[0002] At present, passive optical networks have been widely used in access networks due to their high bandwidth, long transmission distance, low cost, multi-service support, and easy maintenance. With the large-scale construction of fiber-to-the-home, the number of optical fibers laid has continued to increase, the coverage has expanded, and the amount of business carried has also continued to increase. Therefore, it is very important to establish a low-cost, large-capacity, and highly reliable passive optical network. However, due to the complexity of the access environment and the characteristics of long-distance transmission, fault monitoring and location has always been one of the important challenges in PON (Passive Optical Network).

[0003] Among related technologies, OTDR (Optical Time Domain Reflectometer) can provide detailed information about fiber length, loss, attenuation, connection points, breakpoints and other potential problems, and has wide application value in many fields such as fiber link fault query and positioning, and fiber optic cable construction and maintenance. Therefore, OTDR has become the main solution for PON monitoring.

[0004] However, the fault monitoring method based on OTDR is mainly applicable to point-to-point networks. For point-to-multipoint networks, such as PON, the backscattered signal measured by OTDR contains all signals from different branch links, so the signal of one branch may be partially or completely covered by the signals of other branches.

[0005] Therefore, it is necessary to design a new passive optical network monitoring device to overcome the above problems. Summary of the invention

[0006] The present application provides a passive optical network monitoring device and detection method, which can solve the technical problem that the OTDR-based fault monitoring method in the related art is mainly applicable to point-to-point networks but not to point-to-multipoint networks.

[0007] In a first aspect, an embodiment of the present application provides a passive optical network monitoring device, comprising: an optical generation module, which is used to generate pulsed light with a pseudo-random sequence; a circulator, which is connected to the optical generation module; a splitter, which is connected to the circulator through an optical fiber trunk; a plurality of optical network units, which are connected to the splitter through branch links, and each branch link is provided with a reflection point; and a reflected light analysis module, which is connected to the splitter, and the reflected light analysis module is used to receive a reflected light signal and analyze a fault location based on the reflected light signal.

[0008] In combination with the first aspect, in one embodiment, the light generating module includes: a light source, which is used to emit continuous light; a modulation module, which connects the light source and the circulator, and is used to modulate the continuous light emitted by the light source into a pulse light with a pseudo-random sequence.

[0009] In combination with the first aspect, in one embodiment, the modulation module includes: an intensity modulator, the intensity modulator is connected to the light source; an acousto-optic modulator, the acousto-optic modulator is connected to the intensity modulator and the circulator; a pseudo-random sequence generator, the pseudo-random sequence generator is connected to the intensity modulator and the acousto-optic modulator, the pseudo-random sequence generator is used to modulate the pseudo-random sequence onto continuous light through the intensity modulator, and drive the acousto-optic modulator to modulate the continuous light with the pseudo-random sequence into pulsed light with the pseudo-random sequence.

[0010] In combination with the first aspect, in one implementation, the passive optical network monitoring device further includes an amplifier, wherein the amplifier is disposed between the intensity modulator and the acousto-optic modulator, and the intensity modulator is connected to the acousto-optic modulator via the amplifier.

[0011] In combination with the first aspect, in one embodiment, the reflected light analysis module includes: a photodetector, which is connected to the circulator and is used for photoelectric conversion; and a data processing module, which is connected to the photodetector and is used to analyze the fault location based on the reflected light signal.

[0012] In combination with the first aspect, in one embodiment, the reflected light analysis module further includes an optical filter, wherein the optical filter is located between the circulator and the photodetector, and the photodetector is connected to the circulator via the optical filter.

[0013] In combination with the first aspect, in one embodiment, the reflected light analysis module also includes an analog-to-digital converter, which is located between the photodetector and the data processing module, and the data processing module is connected to the photodetector via the analog-to-digital converter, and the analog-to-digital converter is used to capture the reflected light signal trajectory.

[0014] In combination with the first aspect, in one implementation, positions of reflection points on each of the branch links are different.

[0015] In a second aspect, an embodiment of the present application provides a passive optical network link detection method, which includes the following steps:

[0016] Sending pulse light with a pseudo-random sequence to the circulator, so that the pulse light with the pseudo-random sequence passes through the circulator and the splitter and enters each branch link, wherein each branch link is connected to an optical network unit and each branch link is provided with a reflection point;

[0017] A reflected light signal is received, and a fault location is analyzed based on the reflected light signal.

[0018] In conjunction with the second aspect, in one implementation, analyzing the fault location based on the reflected light signal includes:

[0019] The sequence of reflected light signals is correlated with the pseudo-random sequence to obtain the position and delay of the correlation peak;

[0020] The fault location is determined by the position and delay of the correlation peak.

[0021] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0022] The optical generation module can generate pulse light with a pseudo-random sequence. The pulse light can reach each branch link through the circulator and the splitter. The reflection point set on each branch link can reflect the pulse light. The reflected light analysis module can analyze the fault location according to the reflected light signal. Both the pulse light and the reflected light signal carry a pseudo-random sequence. By controlling the pseudo-random sequence, high-precision resolution can be achieved, which can be used for fault detection in point-to-multipoint networks, solving the technical problem that the OTDR-based fault monitoring method in the related technology is mainly applicable to point-to-point networks but not to point-to-multipoint networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A schematic diagram of the structure of a passive optical network monitoring device provided in an embodiment of the present application;

[0025] Figure 2 Among them, (1) is the optical signal after being modulated by the intensity modulator provided in the embodiment of the present application, and (2) is the optical signal after passing through the amplifier and the acousto-optic modulator.

[0026] In the figure:

[0027] 1. Light generation module; 11. Light source; 12. Intensity modulator; 13. Acousto-optic modulator; 14. Pseudo-random sequence generator; 15. Amplifier;

[0028] 2. Circulator; 3. Optical fiber trunk; 4. Splitter;

[0029] 5. Branch link; 6. Optical network unit; 7. Reflection point;

[0030] 8. Reflected light analysis module; 81. Photoelectric detector; 82. Data processing module; 83. Optical filter; 84. Analog-to-digital converter. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] The embodiments of the present application provide a passive optical network monitoring device and detection method, which can solve the technical problem that the OTDR-based fault monitoring method in the related art is mainly applicable to point-to-point networks but not to point-to-multipoint networks.

[0033] See also Figure 1 As shown, a passive optical network monitoring device provided in an embodiment of the present application may include: an optical generation module 1, which is used to generate pulse light with a pseudo-random sequence; a circulator 2, which is connected to the optical generation module 1; a splitter 4, which is connected to the circulator 2 through an optical fiber trunk 3; a plurality of optical network units 6, which are connected to the splitter 4 through branch links 5, and each of the branch links 5 is provided with a reflection point 7; and a reflected light analysis module 8, which is connected to the splitter 4, and the reflected light analysis module 8 is used to receive a reflected light signal and analyze the fault location based on the reflected light signal.

[0034] In this embodiment, the splitter 4 is a 1:N splitter 4, which is used to distribute the detection light (i.e., the pulse light with a pseudo-random sequence) to n branch links 5, and to synthesize the reflected light signals reflected by the n branch links 5 into one; each branch link 5 is connected to an optical network unit 6 (ONU) at the end, and the position of the reflection point 7 on each branch link 5 is different. The function of the optical fiber trunk 3 is to transmit optical signals, fiber to the home, optical wireless access, etc.

[0035] In this embodiment, the optical generation module 1 can generate pulse light with a pseudo-random sequence. The pulse light can reach each branch link 5 through the circulator 2 and the splitter 4. The reflection point 7 set on each branch link 5 can reflect the pulse light. The reflected light signals of each branch link 5 are synthesized into one through the splitter 4 and reach the reflected light analysis module 8 through the circulator 2. After receiving the reflected light signal, the reflected light analysis module 8 can analyze the fault location according to the reflected light signal. In addition, both the pulse light and the reflected light signal carry a pseudo-random sequence. By controlling the pseudo-random sequence, the transmission rate of the pulse light can be controlled. The higher the transmission rate, the better the spatial resolution, and the high-precision resolution can be achieved. The higher the resolution accuracy, the less the reflected light signals of each branch link 5 will affect each other. Therefore, it can be used for fault detection of point-to-multipoint networks, solving the technical problem that the fault monitoring method based on OTDR in the related art is mainly applicable to point-to-point networks and not applicable to point-to-multipoint networks. At the same time, the deployment and implementation of the passive optical network monitoring device provided by this embodiment does not require changing the original PON structure, and has strong scalability and low cost.

[0036] Furthermore, in one embodiment, the light generating module 1 may include: a light source 11, the light source 11 is used to emit continuous light; a modulation module, the modulation module is connected to the light source 11 and the circulator 2, and the modulation module is used to modulate the continuous light emitted by the light source 11 into a pulse light with a pseudo-random sequence. In this embodiment, the light source 11 can emit continuous light, and the modulation module can modulate and cut the continuous light emitted by the light source 11, and can first modulate the pseudo-random sequence onto the continuous light, and then cut the continuous light with the pseudo-random sequence to form a pulse light with a pseudo-random sequence. In this embodiment, the light source 11 is separated from the modulation module, and the separate modulation module can better adjust the pseudo-random sequence, and then modulate the appropriate pseudo-random sequence onto the continuous light emitted by the light source 11.

[0037] Further, in some optional embodiments, see Figure 1As shown, the modulation module may include: an intensity modulator 12, wherein the intensity modulator 12 is connected to the light source 11; an acousto-optic modulator 13, wherein the acousto-optic modulator 13 is connected to the intensity modulator 12 and the circulator 2; and a pseudo-random sequence generator 14, wherein the pseudo-random sequence generator 14 is connected to the intensity modulator 12 and the acousto-optic modulator 13, wherein the pseudo-random sequence generator 14 is used to modulate the pseudo-random sequence onto the continuous light through the intensity modulator 12, and drive the acousto-optic modulator 13 to modulate the continuous light with the pseudo-random sequence into a pulse light with the pseudo-random sequence. In this embodiment, the pseudo-random sequence generator 14 can generate a pseudo-random sequence, and at the same time, the pseudo-random sequence generator 14 can modulate the pseudo-random sequence onto the continuous light emitted by the light source 11 through the intensity modulator 12, and the continuous light modulated by the intensity modulator 12 is as shown in FIG. Figure 2 (1); the pseudo-random sequence generator 14 can also drive the acousto-optic modulator 13 to cut the continuous light, and modulate the continuous light with the pseudo-random sequence into the pulse light with the pseudo-random sequence. In this embodiment, the acousto-optic modulator 13 acts as an optical switch, and the energy of the pulse light carrying the pseudo-random sequence is more concentrated than that of the continuous light, which can improve the signal-to-noise ratio of the reflected light signal.

[0038] Based on the above technical solution, see Figure 1 As shown, in some embodiments, the passive optical network monitoring device may further include an amplifier 15, which is disposed between the intensity modulator 12 and the acousto-optic modulator 13, and the intensity modulator 12 is connected to the acousto-optic modulator 13 via the amplifier 15. In this embodiment, the amplifier 15 is used to amplify the optical signal, and the continuous light with the pseudo-random sequence is first amplified by the amplifier 15 to obtain Figure 2 The continuous light shown in (2) then enters the acousto-optic modulator 13, and the acousto-optic modulator 13 modulates the continuous light with a pseudo-random sequence into a pulse light with a pseudo-random sequence.

[0039] Further, in one embodiment, see Figure 1As shown, the reflected light analysis module 8 may include: a photodetector 81, the photodetector 81 is connected to the circulator 2, and the photodetector 81 is used for photoelectric conversion; a data processing module 82, the data processing module 82 is connected to the photodetector 81, and the data processing module 82 is used to analyze the fault location based on the reflected light signal. In this embodiment, the photodetector 81 can detect the reflected light signal, and transmit the reflected light signal to the data processing module 82 after performing photoelectric conversion. After receiving the converted reflected light signal, the data processing module 82 can perform a correlation operation on the sequence of the reflected light signal and the pseudo-random sequence. According to the correlation peak and the time delay, the position of the reflection point can be determined, and according to the change in the amplitude of the correlation peak, the change in the intensity of the branch light can be determined, thereby discovering the fault. And the data processing module 82 is used to determine whether the link is faulty, with fast response speed and simple operation.

[0040] In this embodiment, the pulsed light signals reflected from different reflection points all carry pseudo-random sequences. The data processing module 82 performs autocorrelation operation on the pseudo-random sequence in the reflected light and the pseudo-random sequence originally sent. Since the reflected signals with different time delays will appear as different correlation peaks on the time axis, the round-trip time of the reflected signal can be calculated based on the delay of the correlation peak. The time accuracy is the duration of the unit bit of the pseudo-random sequence. Correspondingly, the spatial resolution of the reflection point depends on the duration of a single bit in the sequence, and the formula is: Where c represents the propagation rate of light in the optical fiber, and t represents the duration of a unit bit in the PN code. Therefore, the higher the transmission rate, the shorter the duration t of the unit bit, and the better the spatial resolution D, thus achieving high-precision resolution. Since the distance from the reflection point to the splitter of each branch link is difficult to be completely equal, all reflection points will be marked as independent reflection peaks at high resolution, making it easy to distinguish and identify each branch. Therefore, different reflection points can be identified according to the different distances between the reflection points, which is used for fault detection in point-to-multipoint networks.

[0041] Furthermore, in one embodiment, the reflected light analysis module 8 may further include an optical filter 83, the optical filter 83 is located between the circulator 2 and the photodetector 81, and the photodetector 81 is connected to the circulator 2 via the optical filter 83. In this embodiment, after the reflected light signal passes through the circulator 2, it first passes through the optical filter 83 and then reaches the photodetector 81, and the optical filter 83 can filter the reflected light signal.

[0042] Furthermore, in some embodiments, the reflected light analysis module 8 may also include an analog-to-digital converter 84, the analog-to-digital converter 84 is located between the photodetector 81 and the data processing module 82, and the data processing module 82 is connected to the photodetector 81 via the analog-to-digital converter 84, and the analog-to-digital converter 84 is used to capture the reflected light signal trajectory. In this embodiment, the reflected light signal passing through the photodetector 81 will be received by the analog-to-digital converter 84, digital signal processing is performed, the reflected light signal trajectory is captured, and then reaches the data processing module 82 for analysis.

[0043] The present application also provides a passive optical network link detection method, which may include the following steps:

[0044] Step 1: Send pulse light with a pseudo-random sequence to the circulator 2, so that the pulse light with the pseudo-random sequence passes through the circulator 2 and the splitter 4 and enters each branch link 5, wherein each branch link 5 is connected to an optical network unit 6, and each branch link 5 is provided with a reflection point 7.

[0045] Step 2: Receive the reflected light signal, and analyze the fault location based on the reflected light signal.

[0046] In this embodiment, the optical generation module 1 can generate pulse light with a pseudo-random sequence. The optical generation module 1 is connected to the circulator 2. The optical generation module 1 can send the pulse light with a pseudo-random sequence to the circulator 2. The pulse light reaching the circulator 2 can be sent to the splitter 4 through the optical fiber trunk 3. After the splitting, the pulse light is divided into N paths and sent to each branch link 5 respectively. The reflection point 7 on each branch link 5 can reflect the pulse light to form a reflected light signal. The reflected light signal passes through the splitter 4 and the circulator 2 in sequence and is received by the reflected light analysis module 8. The reflected light analysis module 8 can analyze the fault location based on the reflected light signal. Among them, the optical generation module 1 in this embodiment can adopt the optical generation module 1 provided in any of the above embodiments and realize the corresponding functions, which will not be repeated here; and the reflected light analysis module 8 can adopt the reflected light analysis module 8 provided in any of the above embodiments and realize the corresponding functions, which will not be repeated here.

[0047] In step 1, at the transmitting end, the pseudo-random sequence generator 14 modulates the pseudo-random sequence onto the optical signal through the intensity modulator 12, and enters the acousto-optic modulator 13 after passing through the amplifier 15. The pseudo-random sequence generator 14 can drive the acousto-optic modulator 13 to modulate the pulse light, and the generated pulse light with the pseudo-random sequence enters the ODN network through the circulator 2. The pulse light with the pseudo-random sequence is reflected at the reflection point 7 of each branch link 5 and returns to the receiving end through the circulator 2.

[0048] In step 2, at the receiving end, the reflected light signal passes through the optical filter 83, is detected by the photodetector 81, is received by the analog-to-digital converter 84, performs digital signal processing, and then transmits the reflected light signal to the data processing module 82.

[0049] Furthermore, in one embodiment, analyzing the fault location based on the reflected light signal may include:

[0050] Step 21: perform a correlation operation on the sequence of reflected light signals and the pseudo-random sequence to obtain the position and delay of the correlation peak.

[0051] Step 22: Determine the fault location by the location and time delay of the correlation peak. In this step, both step 21 and step 22 are performed in the data processing module 82 .

[0052] In this embodiment, the pseudo-random sequence is usually used to verify the correctness and integrity of the signal due to its autocorrelation characteristics. When we perform correlation operations on the transmitted pseudo-random sequence and the received signal, even under low signal-to-noise ratio conditions, by accurately matching the pseudo-random sequence, a significant peak in the correlation result can be observed. This characteristic is used to identify the pseudo-random sequence from the noisy received signal and accurately determine the delay and time interval. Based on the good autocorrelation characteristics of the pseudo-random sequence, a significant correlation peak is formed only when the received sequence is aligned with the transmitted sequence. Therefore, the round-trip time of the reflected signal can be measured based on the delay of the correlation peak. The time accuracy is the duration of a unit bit in the pseudo-random sequence, and the spatial resolution is D=ct / 2, where c represents the propagation rate of light in the optical fiber, and t represents the duration of a unit bit in the PN code.

[0053] In the present application, first, at the transmitting end, the pseudo-random sequence generator 14 modulates the pseudo-random sequence onto the continuous light through the intensity modulator 12, and after amplification by the amplifier 15, the signal light is cut by the acousto-optic modulator 13 to obtain the pulse light with the pseudo-random sequence, and then the cut pulse light enters the optical fiber trunk 3 through the circulator 2, and is connected to each branch link 5 by the splitter 4, and then connected to the ONU, and the pulse light is reflected after passing through the reflection point 7 of each branch link 5. Finally, at the receiving end, the reflected light signal is associated with the transmission sequence, and the pseudo-random sequence is detected from the noise. In this embodiment, each branch is distinguished by the different positions of the reflection point 7 on each branch link 5. The passive optical network monitoring device is simple, cheap, easy to expand, fast monitoring response speed, simple operation, and reduced maintenance costs.

[0054] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0055] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0056] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A passive optical network monitoring device, characterized in that: It includes: A light generating module (1) for generating pulsed light with a pseudo-random sequence; A circulator (2), the circulator (2) being connected to the light generating module (1); A splitter (4), the splitter (4) being connected to the circulator (2) via an optical fiber trunk (3); A plurality of optical network units (6), wherein the plurality of optical network units (6) are connected to the splitter (4) via branch links (5), and each branch link (5) is provided with a reflection point (7); and a reflected light analysis module (8), which is connected to the splitter (4), and the reflected light analysis module (8) is used to receive the reflected light signal and analyze the fault location based on the reflected light signal.

2. The passive optical network monitoring device according to claim 1, characterized in that: The light generating module (1) comprises: A light source (11), the light source (11) being used to emit continuous light; A modulation module is connected to the light source (11) and the circulator (2), and is used to modulate the continuous light emitted by the light source (11) into pulsed light with a pseudo-random sequence.

3. The passive optical network monitoring device according to claim 2, characterized in that: The modulation module comprises: an intensity modulator (12), the intensity modulator (12) being connected to the light source (11); an acousto-optic modulator (13), the acousto-optic modulator (13) being connected to the intensity modulator (12) and the circulator (2); A pseudo-random sequence generator (14) is connected to the intensity modulator (12) and the acousto-optic modulator (13), and is used to modulate a pseudo-random sequence onto continuous light through the intensity modulator (12), and to drive the acousto-optic modulator (13) to modulate the continuous light with the pseudo-random sequence into pulsed light with the pseudo-random sequence.

4. The passive optical network monitoring device according to claim 3, characterized in that: The passive optical network monitoring device also includes an amplifier (15), wherein the amplifier (15) is arranged between the intensity modulator (12) and the acousto-optic modulator (13), and the intensity modulator (12) is connected to the acousto-optic modulator (13) via the amplifier (15).

5. The passive optical network monitoring device according to claim 1, characterized in that: The reflected light analysis module (8) comprises: A photodetector (81), the photodetector (81) is connected to the circulator (2), and the photodetector (81) is used for performing photoelectric conversion; A data processing module (82), the data processing module (82) is connected to the photoelectric detector (81), and the data processing module (82) is used to analyze the fault location based on the reflected light signal.

6. The passive optical network monitoring device according to claim 5, characterized in that: The reflected light analysis module (8) further comprises an optical filter (83), wherein the optical filter (83) is located between the circulator (2) and the photodetector (81), and the photodetector (81) is connected to the circulator (2) via the optical filter (83).

7. The passive optical network monitoring device according to claim 5 or 6, characterized in that: The reflected light analysis module (8) further comprises an analog-to-digital converter (84), wherein the analog-to-digital converter (84) is located between the photodetector (81) and the data processing module (82), and the data processing module (82) is connected to the photodetector (81) via the analog-to-digital converter (84), and the analog-to-digital converter (84) is used to capture the trajectory of the reflected light signal.

8. The passive optical network monitoring device according to claim 1, characterized in that: The positions of the reflection points (7) on each of the branch links (5) are different.

9. A passive optical network link detection method, characterized in that: It includes the following steps: Sending pulse light with a pseudo-random sequence to the circulator (2), so that the pulse light with the pseudo-random sequence passes through the circulator (2) and the splitter (4) and enters each branch link (5), wherein each branch link (5) is connected to an optical network unit (6), and each branch link (5) is provided with a reflection point (7); A reflected light signal is received, and a fault location is analyzed based on the reflected light signal.

10. The passive optical network link detection method according to claim 9, characterized in that: The analyzing the fault location based on the reflected light signal comprises: The sequence of reflected light signals is correlated with the pseudo-random sequence to obtain the position and delay of the correlation peak; The fault location is determined by the position and delay of the correlation peak.

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