Passive optical network (PON) fault detection method

Abstract

The embodiment of the invention provides a passive optical network (PON) fault detection method, which comprises the following steps of: sending a first downlink optical signal through an optical line terminal (OLT), and receiving a reflection superposition signal from a plurality of branch optical fiber links, and the branch optical fiber links are provided with devices for changing the characteristics of the optical signal; and the OLT determines a fault of the branch optical fiber link based on the reflection superposition signal and a preset downlink change signal. The problem that fault detection cannot be rapidly and accurately carried out in a point-to-multipoint PON topology system in the prior art is solved, and the effect of improving the efficiency and accuracy of fault detection in the point-to-multipoint PON topology system is achieved.

Description

Technical Field

[0001] This invention relates to the field of communications, and more specifically, to a method for detecting faults in a passive optical network (PON). Background Technology

[0002] During the deployment of an Optical Distribution Network (ODN), operators often struggle to obtain the correct ODN topology. They must manually record the locations of optical splitters and their connections to Optical Network Terminations (ONTs) in the resource management system. However, manual recording is prone to errors, and the relationships between splitters and ONTs can change at any time, leading to inaccurate records. Therefore, in the operation of a Passive Optical Network (PON) system, when a system fault occurs, it is difficult to quickly and accurately pinpoint the fault location and promptly eliminate it.

[0003] Currently, network system fault detection primarily utilizes optical time domain reflectometers (OTDRs). This method is effective for fault detection and location in point-to-point network topologies and is widely used in point-to-point network fault detection. However, in point-to-multipoint PON topologies, OTDRs cannot distinguish Rayleigh backscattered light from different branches, thus making fiber optic fault detection impossible.

[0004] In summary, the relevant technologies have the problem of not being able to quickly and accurately detect faults in point-to-multipoint PON topology systems. Summary of the Invention

[0005] This invention provides a method for fault detection in passive optical networks (PONs), which at least solves the problem that fault detection cannot be performed quickly and accurately in point-to-multipoint PON topology systems in related technologies.

[0006] According to an embodiment of the present invention, a method for fault detection in a passive optical network (PON) is provided, comprising: an optical line terminal (OLT) transmitting a first downlink optical signal and receiving reflected superimposed signals from multiple branch optical fiber links, wherein the branch optical fiber links are provided with devices for changing the characteristics of the optical signals; and the OLT determining a fault in the branch optical fiber link based on the reflected superimposed signals and a preset downlink change signal.

[0007] According to yet another embodiment of the present invention, a computer-readable storage medium is also provided, wherein a computer program is stored therein, wherein the computer program is configured to perform the steps in any of the above method embodiments when executed.

[0008] According to yet another embodiment of the present invention, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0009] According to yet another embodiment of the present invention, a computer program product is also provided, comprising a computer program that, when executed by a processor, implements the steps in any of the above method embodiments.

[0010] This invention provides a method for fault detection in a Passive Optical Network (PON). An OLT transmits a first downlink optical signal and receives reflected and superimposed signals from multiple branch fiber optic links. Each branch fiber optic link is equipped with a device to modify the characteristics of the optical signal. The OLT determines the fault in a branch fiber optic link based on the reflected and superimposed signals and a preset downlink variation signal. This method solves the problem of slow and accurate fault detection in point-to-multipoint PON topologies, improving both the efficiency and accuracy of fault detection in such systems. Attached Figure Description

[0011] Figure 1 This is a hardware structure block diagram of the computer terminal for the PON fault detection method according to an embodiment of the present invention.

[0012] Figure 2 This is a flowchart of passive optical network (PON) fault detection according to an embodiment of the present invention;

[0013] Figure 3 This is a schematic diagram of the port identification process according to an embodiment of the present invention;

[0014] Figure 4 This is a schematic diagram of the fault detection process according to an embodiment of the present invention;

[0015] Figure 5 This is a schematic diagram illustrating the principle of port recognition in an embodiment of the present invention;

[0016] Figure 6 This is the structural principle of the branch fiber optic link device according to an embodiment of the present invention. Figure 1 ;

[0017] Figure 7 This is the structural principle of the branch fiber optic link device according to an embodiment of the present invention. Figure 2 . Detailed Implementation

[0018] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0020] Passive Optical Network (PON) is a point-to-multipoint network. The system mainly consists of an Optical Line Terminal (OLT) at the central office, Optical Network Units (ONUs) or Optical Network Terminals (ONTs) at the user end, and an Optical Distribution Network (ODN). The ODN of a PON is an optical distribution network used to branch / couple or multiplex / demultiplex optical signals between the OLT and ONT. It can include passive optical devices such as optical fibers, splitters, optical couplers, fiber optic connectors, and wavelength division multiplexers. Compared to point-to-point topologies, this point-to-multipoint optical distribution network structure of PON can significantly reduce fiber costs. However, this multi-branch structure based on passive optical devices such as splitters poses significant challenges to fault detection technology and topology visualization in optical distribution networks.

[0021] The methods and embodiments provided in this application can be executed on a mobile terminal, a computer terminal, or a similar computing device. Taking running on a computer terminal as an example, Figure 1 This is a hardware structure block diagram of the computer terminal for the PON fault detection method according to an embodiment of the present invention. Figure 1 As shown, a computer terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 (which may include, but is not limited to, a microprocessor MCU or a programmable logic device FPGA, etc.) and a memory 104 for storing data are also shown. The computer terminal may further include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that... Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the computer terminal described above. For example, the computer terminal may also include components that are more complex than those described above. Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown.

[0022] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the PON fault detection method in this embodiment of the invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, thereby implementing the above-described method. The memory 104 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to a computer terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0023] The transmission device 106 is used to receive or send data via a network. Specific examples of the network described above may include a wireless network provided by a communication provider for the computer terminal. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 106 may be a Radio Frequency (RF) module, used for wireless communication with the Internet.

[0024] This invention provides a method for detecting faults in a passive optical network (PON). Figure 2 This is a flowchart of passive optical network (PON) fault detection according to an embodiment of the present invention, such as... Figure 2 As shown, the process includes the following steps:

[0025] In step S202, the OLT sends a first downlink optical signal and receives reflected superimposed signals from multiple branch fiber links, wherein the branch fiber links are equipped with devices for changing the characteristics of the optical signals.

[0026] In this embodiment of the invention, the above-mentioned reflected superimposed signal is a return signal generated by the first downlink optical signal during system transmission after being scattered by the optical fiber or reflected by optoelectronic devices and connectors. The reflected superimposed signal is received at the OLT end.

[0027] In one exemplary embodiment, before the OLT transmits the first downlink optical signal, the method further includes: the OLT sending control information to the ONU, the control information being used to notify the ONU to stop uplink information transmission and start fault detection; the OLT receiving control response information from the ONU and stopping downlink information transmission.

[0028] In step S204, the OLT determines the fault of the branch fiber link based on the reflected superimposed signal and the preset downlink change signal.

[0029] In one exemplary embodiment, the method further includes: the OLT performing simulation calculations on the first downlink optical signal based on different device characteristics of the branch fiber link to obtain a preset downlink variation signal.

[0030] In an exemplary embodiment, the OLT determines the fault of a branch fiber link based on the reflected superimposed signal and the preset downlink change signal, including: the OLT performs calculations on the reflected superimposed signal and the preset downlink change signal, and determines the branch fiber link that caused the fault based on the calculation results; the OLT obtains the optical time domain reflectometer (OTDR) curve of the corresponding branch fiber link based on the calculation results; and the OLT locates the fault in the branch fiber link according to the OTDR curve.

[0031] In one exemplary embodiment, the preset downlink change signals corresponding to different branch fiber optic links are orthogonal to each other; or, the correlation between the preset downlink change signals corresponding to different branch fiber optic links satisfies a preset minimum correlation threshold.

[0032] In one exemplary embodiment, the method further includes: the OLT sending a second downlink optical signal to the ONU, with each ONU connected to a branch optical fiber link; the OLT receiving uplink feedback signals from the ONU and determining the branch optical fiber link connected to the ONU based on the characteristic parameters of the uplink feedback signals and the device characteristics of the branch optical fiber link, so as to establish a connection mapping relationship between the ONU and the branch optical fiber link.

[0033] In this embodiment of the invention, the aforementioned uplink feedback signal includes, but is not limited to, the modified signal and a simplified feature signal formed by feature extraction of the modified signal. The modified signal is the signal that is altered by the aforementioned second downlink optical signal as it passes through the branch fiber optic link.

[0034] In an exemplary embodiment, the characteristic parameters of the uplink feedback signal include at least one of the following: pitch depth; eye diagram; signal spectrum.

[0035] This invention provides a method for fault detection in a Passive Optical Network (PON). An OLT transmits a first downlink optical signal and receives reflected and superimposed signals from multiple branch fiber optic links. Each branch fiber optic link is equipped with a device to modify the characteristics of the optical signal. The OLT determines the fault in a branch fiber optic link based on the reflected and superimposed signals and a preset downlink variation signal. This method solves the problem of slow and accurate fault detection in point-to-multipoint PON topologies, improving both the efficiency and accuracy of fault detection in such systems.

[0036] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0037] This embodiment also provides a PON fault detection device for implementing the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0038] The PON fault detection provided in this embodiment of the invention can be configured as an OLT, including a transmitting module and a detection module. The transmitting module is configured to transmit a first downlink optical signal and receive reflected superimposed signals from multiple branch fiber links, wherein the branch fiber links are equipped with devices for changing the characteristics of the optical signals. The detection module is configured to determine the fault of the branch fiber link based on the reflected superimposed signals and a preset downlink change signal.

[0039] In this embodiment of the invention, the PON fault detection device may also include different modules, and the naming and functional division of the modules may be selected in different ways according to the actual situation, without specific restrictions.

[0040] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0041] Embodiments of the present invention also provide a computer-readable storage medium storing a computer program, wherein the computer program is configured to perform the steps in any of the above method embodiments when executed.

[0042] In one exemplary embodiment, the aforementioned computer-readable storage medium may include, but is not limited to, various media capable of storing computer programs, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard disk, magnetic disk, or optical disk.

[0043] Embodiments of the present invention also provide an electronic device including a memory and a processor, the memory storing a computer program and the processor being configured to run the computer program to perform the steps in any of the above method embodiments.

[0044] In one exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor and the input / output device is connected to the processor.

[0045] This invention also provides a computer program product, including a computer program that, when executed by a processor, implements the steps in any of the above method embodiments.

[0046] In one exemplary embodiment, the computer program product described above includes a non-volatile computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the methods described in various embodiments of this application.

[0047] Specific examples in this embodiment can be found in the examples described in the above embodiments and exemplary implementations, and will not be repeated here.

[0048] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0049] To enable those skilled in the art to better understand the technical solutions of the present invention, the following description is provided in conjunction with different embodiments.

[0050] Example 1

[0051] Topology restoration in PON involves two aspects. The first is branch and port identification, used to identify the connections between branches and ports of ONUs in the network. The second is fault detection, identifying faulty branches.

[0052] The PON fault detection method proposed in this invention does not require any changes to existing ONU equipment and optical modules, does not require the addition of a detection light source on the OLT side, and while the ODN splitter maintains its passive characteristics, it can realize fault detection and ONU port identification in the ODN network, and perform fault detection in the ODN network.

[0053] The PON fault detection method proposed in this invention includes two stages: port identification and fault detection. The port identification establishes a mapping relationship between the ONU and the branch fiber link, and the fault detection determines the branch fiber link that caused the fault and the location of the fault.

[0054] Figure 3 This is a schematic diagram of the port identification process according to an embodiment of the present invention, such as... Figure 3 As shown, it includes the following steps:

[0055] Step 1: Send downlink signal.

[0056] The OLT sends downlink service signals, custom signals, or pulses (i.e., the second downlink optical signal). These downlink signals undergo multipath superposition and delay through different branch fiber links, resulting in different changes to the downlink optical signal. The OLT needs to notify the ONU (Optical Network Unit) in the message management system to provide feedback upon receiving the downlink optical signal; that is, the ONU sends an uplink feedback signal to the OLT. The information required for this feedback is defined by the OLT so that it can distinguish between different branch fiber links after receiving the uplink feedback signal.

[0057] Step 2: Receive the signal, the signal with changed uplink transmission characteristics, such as a change in code pattern.

[0058] The ONU connected to the ports of different branch fiber optic links receives downlink optical signals. The ONU then transmits the changes in the characteristics of the received downlink optical signals to the OLT uplink. These changes in the characteristics of the optical signals may include, but are not limited to, changes in the optical signal's code pattern.

[0059] Step 3: Identify changes in the signal (e.g., changes in the code pattern) and establish the mapping relationship between the ONU and the branch fiber optic link.

[0060] The OLT receives the uplink feedback signal from the ONU and determines the corresponding branch fiber link connected to the ONU based on the characteristic parameters of the uplink feedback signal and the device characteristics of the branch fiber link, thereby establishing a connection mapping relationship between the ONU and the branch fiber link. This mapping relationship is stored in the register on the OLT side. The uplink feedback signal includes, but is not limited to, the modified signal and a simplified feature signal formed by feature extraction from the modified signal. The modified signal is the signal that changes as the second downlink optical signal in the above embodiment passes through the branch fiber link.

[0061] Figure 4 This is a schematic diagram of the fault detection process according to an embodiment of the present invention, such as... Figure 4 As shown, it includes the following steps:

[0062] Step 1: If fault detection is initiated, the OLT sends control information to notify the ONU that fault detection is expected to start after N frames.

[0063] Step 2: The ONU responds to the OLT and stops uplink services. Uplink services are included in uplink information transmission.

[0064] When the ONU receives a fault detection notification (i.e., the aforementioned control information) from the OLT, it responds to the OLT by sending a control response message and simultaneously stops uplink information transmission.

[0065] Step 3: The OLT receives feedback from the ONU, suspends downlink services, and sends a detection signal.

[0066] After receiving the control response information from the ONU, the OLT suspends downlink information transmission and performs fault detection. The OLT sends a downlink optical signal (i.e., the first downlink optical signal in the above embodiment, also known as the detection signal), which undergoes multipath superposition and delay through various branch fiber optic links with different devices, resulting in different downlink optical signal changes (i.e., obtaining the reflected superimposed signal in the above embodiment). The reflected superimposed signal is the return signal generated by the first downlink optical signal during system transmission, after scattering through the optical fiber or reflection through optoelectronic devices and connectors. The reflected superimposed signal is received at the OLT end.

[0067] In this embodiment of the invention, the preset downlink change signals corresponding to different branch optical fiber links are controlled to be orthogonal to each other; or, the correlation between the preset downlink change signals corresponding to different branch optical fiber links satisfies a preset minimum correlation threshold.

[0068] Step 4: The OLT receives the scattered / reflected detection signal (the reflected superimposed signal in the above embodiment), performs relevant calculations, and locates the fault.

[0069] The OLT receives the reflected and superimposed signals from the optical fiber after multiple paths. It processes the reflected and superimposed signals with preset downlink change signals to detect the corresponding faulty branch optical fiber links. Based on the calculation results, it plots the corresponding OTDR curve and locates the fault in the branch optical fiber link by abnormal reflection peaks and attenuation points on the OTDR curve.

[0070] In one embodiment, when the OLT transmits the first downlink optical signal, it can store the original first downlink optical signal. Then, using the stored first downlink optical signal, it performs real-time calculations based on the device's characteristics to obtain the aforementioned preset downlink change signal. Finally, it processes the preset downlink change signal and the reflected superimposed signal to detect the faulty branch fiber optic link. In another embodiment, when the OLT transmits the first downlink optical signal, it performs simulation calculations based on the first downlink optical signal and the device's characteristics to obtain the aforementioned preset downlink change signal. It then stores the preset downlink change signal. Upon receiving the reflected superimposed signal, it directly processes the reflected superimposed signal and the stored preset downlink change signal to detect the faulty branch fiber optic link.

[0071] In one embodiment, the preset downlink change signal needs to meet the following conditions: the preset downlink change signals corresponding to different branch fiber links are orthogonal to each other; or, the correlation between the preset downlink change signals corresponding to different branch fiber links meets a preset minimum correlation threshold. Only when these conditions are met can different branch fiber links be correctly distinguished after processing, enabling fault location and identification. The computational method used to obtain the preset downlink change signal based on the characteristics of the device from the first downlink optical signal is not limited in this embodiment.

[0072] In this embodiment of the invention, different device characteristics of the branch fiber optic link, such as the splitting-combining ratio, delay time, and combining information, are uniformly stored in a table at the OLT. The OLT performs simulation calculations based on the stored device characteristic information. Figure 6 Taking a device with two paths as an example, the random sequence of the first downlink optical signal is represented by X(T). The preset downlink change signal obtained by simulating the device characteristics such as beam splitting, delay, and beam combining on X(T) is as follows:

[0073] X(T-T1)*1 / (M+1) / (N+1)+X(T-T2)*M / (M+1)*N / (N+1).

[0074] Among them, such as Figure 6 As shown, M represents the splitting ratio, T1 and T2 represent delays, T represents the time parameter of the random sequence, and N represents the combining ratio.

[0075] Step 5: After receiving the reflected superimposed signal from the fault detection, the OLT resumes the transmission of downlink information (including but not limited to downlink service transmission).

[0076] Step 6: The ONU receives the recovery notification from the OLT and resumes normal uplink information transmission (including but not limited to uplink service transmission).

[0077] Example 2

[0078] In this embodiment, the process of port identification and fault detection described above is explained in detail.

[0079] Figure 5 This is a schematic diagram illustrating the principle of port recognition in an embodiment of the present invention, as shown below. Figure 5 As shown, different branch fiber optic links are equipped with different devices for altering optical signals. In this embodiment of the invention, the port identification process includes the following steps:

[0080] Step 1: The OLT sends downlink service signals, custom signals, or pulses (i.e., the second downlink optical signal). This downlink optical signal undergoes multipath superposition and delay through different branch fiber links, resulting in different changes to the downlink optical signal. The OLT needs to notify the ONU in the message management system to provide feedback upon receiving the downlink optical signal; that is, the ONU sends an uplink feedback signal to the OLT. The information required for feedback is defined by the OLT so that it can distinguish between different branch fiber links after receiving the uplink feedback signal. In one embodiment, the information required for feedback includes, but is not limited to, the modified signal, and simplified feature signal transmission formed by feature extraction of the modified signal.

[0081] In this embodiment of the invention, the branch fiber optic link has different device features. For the branch fiber optic link, the device for changing the optical signal can be on the optical fiber or integrated into the optical splitter.

[0082] Figure 6 This is the structural principle of the branch fiber optic link device according to an embodiment of the present invention. Figure 1 ,like Figure 6 As shown, the downlink optical signal is split into two paths by an optical splitter with a splitting ratio of 1:M. One path is delayed by T1 through path 1, and the other path is delayed by T2 through path 2. Then, they are coupled by an optical combiner with a combining ratio of 1:N to become the modified downlink optical signal.

[0083] In one embodiment, the process of changing the optical signal described above is not limited to two paths; it can be split into multiple paths using a beam splitter, and then the multiple optical signals can be superimposed and combined into one using a beam combiner. Figure 6 This example uses only two paths.

[0084] In one embodiment, the above-described device for altering optical signals can also be a single-path device, but it can be implemented by adding additional reflectors, including but not limited to Bragg gratings, resonant cavities, circulators, etc.

[0085] Figure 7 This is the structural principle of the branch fiber optic link device according to an embodiment of the present invention. Figure 2 ,like Figure 7 As shown, the downlink optical signal passes through a first reflector (fully passable in one direction, 100% reflected in the other), and after a delay of T1 along path 1, it passes through a second reflector. The second reflector has a reflectivity of R%, and 1-R% of the light will be transmitted and continue to propagate. At this time, the R% of the reflected light will again pass through a delay of T1 and reach the first reflector, where it will be 100% reflected back to the second reflector. The second reflector transmits R%*(1-R%) of light. The transmitted light is equivalent to being delayed and superimposed on the 1-R% light signal that was transmitted in the first transmission. This cycle repeats, theoretically with an infinite number of iterative reflections. However, due to the limitation of light intensity, the subsequent signals will be attenuated to a very weak level, approaching noise.

[0086] In this embodiment of the invention, both of the above-mentioned methods of delaying and superimposing signals can achieve changes in the downlink optical signal, with different device structure changes made on each branch.

[0087] Step 2: The ONU connected to the ports of different branch fiber optic links receives the downlink optical signal. The ONU then transmits the changes in the characteristics of the received downlink optical signal to the OLT uplink. These changes in the optical signal characteristics may include, but are not limited to, changes in the optical signal's code pattern.

[0088] Step 3: The OLT receives the uplink feedback signal from the ONU and determines the corresponding branch fiber link connected to the ONU based on the characteristic parameters of the uplink feedback signal and the device characteristics of the branch fiber link, thus establishing a connection mapping relationship between the ONU and the branch fiber link. This mapping relationship is stored in the register on the OLT side. The aforementioned uplink feedback signal includes, but is not limited to, the modified signal and a simplified feature signal formed by feature extraction from the modified signal. The modified signal is the signal that changes as the second downlink optical signal in the above embodiment passes through the branch fiber link.

[0089] In this embodiment of the invention, the OLT can establish a connection with the branch fiber link based on any unique characteristic of the modified optical signal (i.e., the uplink feedback signal in the above embodiments). This includes, but is not limited to, identification of the tuning depth in the time domain of signal reception, identification of eye diagrams, and analysis of the signal spectrum.

[0090] The fault detection steps are as follows:

[0091] Step 1: If fault detection is initiated, the OLT sends control information to notify the ONU that fault detection is expected to start after N frames.

[0092] Step 2: When the ONU receives the fault detection notification (i.e., the aforementioned control information) from the OLT, it responds to the OLT by sending a control response message and simultaneously stops uplink information transmission.

[0093] Step 3: After receiving the control response information from the ONU, the OLT suspends downlink information transmission and performs fault detection. The OLT sends a downlink optical signal (i.e., the first downlink optical signal in the above embodiment, also known as the detection signal). During the transmission of the first downlink optical signal in the system, the reflected signal generated by the scattering of the optical fiber or the reflection of the optoelectronic device or connector is the above-mentioned reflected superimposed signal. The reflected superimposed signal enters the OLT and is received.

[0094] In this embodiment of the invention, during downlink transmission, without adding an additional OTDR light source or hardware device, the OLT transmits a downlink optical signal. This downlink optical signal includes, but is not limited to, an optical pulse, a pulse sequence, a random service signal, a preamble signal in communication, or any random or known signal transmitted. The OLT pre-buffers this signal into the fault location module for subsequent fault location processing.

[0095] In one embodiment, when the OLT transmits the first downlink optical signal, it can store the original first downlink optical signal. Then, it uses the stored first downlink optical signal to perform real-time calculations based on the device's characteristics to obtain the aforementioned preset downlink change signal. Finally, it processes the preset downlink change signal and the reflected superimposed signal to detect the faulty branch fiber optic link. In another embodiment, when the OLT transmits the first downlink optical signal, it performs simulation calculations based on the first downlink optical signal and the device's characteristics to obtain the aforementioned preset downlink change signal. It then stores the preset downlink change signal. Upon receiving the reflected superimposed signal, it directly uses the reflected superimposed signal and the stored preset downlink change signal to perform calculations to detect the faulty branch fiber optic link. The embodiments of the present invention do not limit the calculation methods involved in obtaining the preset downlink change signal from the first downlink optical signal based on the device's characteristics.

[0096] Step 4: The OLT receives the scattered / reflected detection signal (the reflected superimposed signal in the above embodiment), performs relevant calculations, and locates the fault.

[0097] The OLT receives the reflected and superimposed signals from the optical fiber after multiple paths. It processes the reflected and superimposed signals with preset downlink change signals to detect the corresponding faulty branch optical fiber links. Based on the calculation results, it plots the corresponding OTDR curve and locates the fault in the branch optical fiber link by abnormal reflection peaks and attenuation points on the OTDR curve.

[0098] In this embodiment of the invention, different device characteristics of the branch fiber optic link, such as the splitting and combining ratio, delay time, and combining information, are uniformly stored in a table at the OLT. The OLT performs simulation calculations based on the stored device characteristic information.

[0099] Step 5: After receiving the reflected superimposed signal from the fault detection, the OLT resumes the transmission of downlink information and notifies the ONU to also resume the transmission of uplink information normally.

[0100] Step 6: The ONU receives the recovery notification from the OLT and resumes normal uplink information transmission.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fault detection in a passive optical network (PON), characterized in that, include: The optical line terminal (OLT) sends a first downlink optical signal and receives reflected superimposed signals from multiple branch optical fiber links, wherein the branch optical fiber links are equipped with devices for changing the characteristics of the optical signal. The OLT determines the fault of the branch fiber link based on the reflected superimposed signal and the preset downlink change signal.

2. The method according to claim 1, characterized in that, Also includes: The OLT sends a second downlink optical signal to the optical network unit (ONU), and each ONU is connected to one of the branch optical fiber links. The OLT receives the uplink feedback signal from the ONU and determines the branch fiber link corresponding to the ONU based on the characteristic parameters of the uplink feedback signal and the device characteristics of the branch fiber link, so as to establish the connection mapping relationship between the ONU and the branch fiber link.

3. The method according to claim 2, characterized in that, in, The characteristic parameters of the uplink feedback signal include at least one of the following: Top adjustment depth; eye diagram; signal spectrum.

4. The method according to claim 1, characterized in that, Also includes: The OLT performs simulation calculations on the first downlink optical signal based on the different device characteristics of the branch fiber link to obtain the preset downlink variation signal.

5. The method according to claim 1, characterized in that, The OLT determines the fault of the branch fiber link based on the reflected superimposed signal and the preset downlink change signal, including: The OLT performs calculations on the reflected superimposed signal and the preset downlink change signal, and determines the faulty branch fiber link based on the calculation results. Based on the calculation results, the OLT obtains the corresponding OTDR curve of the branch fiber link; The OLT locates the fault in the branch fiber optic link based on the OTDR curve.

6. The method according to claim 1, characterized in that, in, The preset downlink variation signals corresponding to different branch fiber optic links are orthogonal to each other; Alternatively, the correlation between the preset downlink change signals corresponding to different branch fiber optic links satisfies a preset minimum correlation threshold.

7. The method according to claim 1, characterized in that, Before the OLT transmits the first downlink optical signal, the method further includes: The OLT sends control information to the ONU, which is used to notify the ONU to stop uplink information transmission and start fault detection. The OLT receives control response information from multiple ONUs and stops downlink information transmission.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the method described in any one of claims 1 to 7.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method described in any one of claims 1 to 7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1 to 7.

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