Topology reduction method and apparatus

Abstract

The application relates to the technical field of optical communication, and provides a topology restoration method and device. The method comprises the following steps: receiving a first signal sent from an optical network unit (ONU) passive optical network (PON) port, wherein the first signal is a signal sent by the ONU PON port and reaching an optical line terminal (OLT) PON port through an optical transmission link; the optical transmission link is used for applying corresponding first characteristic information to the first signals sent by different ONU PON ports; analyzing the first characteristic information, and restoring a topology connection relationship between the ONU PON port and the OLT PON port based on an analysis result. The topology restoration method and device provided by the application solve the technical problem that an OLT cannot determine the ODN to which an ONU belongs in a wide-area coverage scenario.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, and in particular to a topology restoration method and apparatus. Background Technology

[0002] In existing Passive Optical Networks (PONs), the Optical Line Terminal (OLT) is connected to the Optical Network Unit (ONU) through the Optical Distribution Network (ODN).

[0003] With the introduction of wide-area coverage technology, a single OLT connects to multiple ODNs via a wide-area coverage panel, and each ODN connects to multiple ONUs, forming a two-stage optical splitting structure. However, due to the lack of a mechanism to identify the ODN to which an ONU belongs, the OLT cannot directly determine which ODN branch the ONU connects to, making it impossible to reconstruct the topological connection relationship between ONUs and ODNs. When a system fault occurs, the OLT cannot determine the ODN to which the fault-related ONU belongs, making fault troubleshooting and diagnosis difficult. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a topology restoration method and apparatus.

[0005] In a first aspect, this application provides a topology restoration method, comprising: The system receives a first signal from the passive optical network (PON) port of the optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port and transmitted through an optical transmission link to the optical line terminal (OLT) PON port; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports. The first feature information is parsed, and based on the parsing result, the topological connection relationship between the ONU PON port and the OLT PON port is restored.

[0006] In one embodiment, the OLT PON port is connected to multiple ONU PON ports via different optical transmission links, and a first module is provided on the corresponding optical transmission link; wherein, the first module is used to enable the signals transmitted by different ONU PON ports to carry the corresponding first feature information in the time domain and / or frequency domain; the first feature information corresponds one-to-one with the optical transmission link corresponding to the ONU PON port; the first feature information includes the time delay value between the ONU PON port and the OLT PON port.

[0007] In one embodiment, the first characteristic information of each ONU PON port under the same optical distribution network (ODN) may be the same or different, and the first characteristic information of all ONU PON ports under different ODNs may be different from each other.

[0008] In one embodiment, parsing the first feature information and, based on the parsing result, reconstructing the topological connection relationship between the ONUPON port and the OLT PON port includes: Perform a second-order autocorrelation operation on the first signal to obtain the second-order autocorrelation moment sequence corresponding to the first feature information; Peak analysis is performed on the second-order autocorrelation moment sequence to obtain target feature information, wherein the target feature information is the first feature information experienced by the first signal; Based on the mapping relationship between latency value and ODN identifier, the target feature information is mapped to the corresponding target ODN identifier; Based on the target ODN identifier, the topology connection relationship is restored.

[0009] In one embodiment, performing a second-order autocorrelation operation on the first signal to obtain the second-order autocorrelation moment sequence corresponding to the first feature information includes: The second-order autocorrelation moment sequence is obtained by multiplying and accumulating the first signal with the shifted sequence obtained by cyclically shifting the first signal to the right by different sign bits. The right-shifted sign bit corresponding to the peak position of the second-order autocorrelation moment sequence is determined based on the target feature information.

[0010] In one embodiment, the peak analysis of the second-order autocorrelation moment sequence to obtain target feature information includes: Determine the maximum, second maximum, and third maximum values ​​in the second-order autocorrelation moment sequence; The target feature information is obtained based on the position of the second maximum value in the second-order autocorrelation moment sequence.

[0011] In one embodiment, before obtaining the target feature information based on the position of the second maximum value in the second-order autocorrelation moment sequence, the method further includes: Calculate the peak-to-sidelobe ratio between the second-highest value and the third-highest value; When the peak sidelobe ratio is less than a preset threshold, the OLT receiver is switched from direct detection reception to coherent reception to obtain the amplitude and phase information of the first signal. Based on the amplitude information and the phase information, a new second-order autocorrelation moment sequence is calculated; The target feature information is obtained based on the position of the second maximum value in the new second-order autocorrelation moment sequence.

[0012] In one embodiment, receiving the first signal sent from the ONU PON port includes: In a multi-generation, multi-rate passive optical network system, the first signal is received from the ONUPON ports of different generations and different rates after being transmitted through their respective corresponding ODNs.

[0013] In one embodiment, the optical transmission link consists of a first optical transmission link and a second optical transmission link; the first module is disposed on the corresponding first optical transmission link and / or second optical transmission link. Wherein, the first optical transmission link is a passive device, and the second optical transmission link is an active device; The passive device includes at least an optical fiber, a beam splitter, and an optical connector. The active device includes at least an optical amplifier, an optical emitting module, a photodetector module, and an electrical signal driver; or, the active device is a device that aggregates multiple ODN signals to the same OLT PON port.

[0014] Secondly, this application provides a topology restoration apparatus, comprising: The receiving module is used to receive a first signal sent from the passive optical network (PON) port of the optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port that reaches the optical line terminal (OLT) PON port through the optical transmission link; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports. The topology restoration module is used to parse the first feature information and restore the topology connection relationship between the ONU PON port and the OLT PON port based on the parsing result.

[0015] Thirdly, this application provides an electronic device, including a processor and a memory storing a computer program, wherein the processor executes the program to implement the steps of the topology restoration method described in the first aspect.

[0016] Fourthly, this application provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the topology restoration method described in the first aspect.

[0017] Fifthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the topology restoration method described in the first aspect.

[0018] The topology restoration method and apparatus provided in this application introduce different first feature information on the optical links between the OLT and multiple ONUs respectively. The OLT can accurately obtain the first feature information that the signal has passed through by analyzing the received signal, and then restore the topology connection relationship between the ONU and the OLT based on the first feature information. This solves the technical problem that the OLT cannot determine the ODN to which the ONU belongs in wide-area coverage scenarios, and improves the efficiency of network fault diagnosis and troubleshooting. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating the topology restoration method provided in this application.

[0021] Figure 2 A schematic diagram illustrating the topology restoration principle for wide-area coverage provided in this application.

[0022] Figure 3 A schematic diagram illustrating the extraction of latency information provided in this application.

[0023] Figure 4 A schematic diagram of the peak sidelobe ratio of the second-order autocorrelation moment sequence provided in this application.

[0024] Figure 5 A topology reconstruction diagram of the multi-generational wide-area coverage PON system provided in this application.

[0025] Figure 6 A schematic diagram of the topology reduction device provided in this application.

[0026] Figure 7 A schematic diagram of the structure of the electronic device provided in this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] A PON network is a point-to-multipoint (P2MP) optical transmission system widely used in fiber optic access networks. A PON network generally consists of three parts: an OLT (Optical Line Terminal), an ODN (Optical Distribution Network), and ONUs (Optical Units). The ODN, composed of single-mode fiber, optical splitters, and optical connectors, provides the optical transmission medium for the physical connection between the OLT and ONUs. Typically, the transmission direction from the OLT to the ONU is defined as the downlink direction, and the transmission direction from the ONU to the OLT is defined as the uplink direction.

[0029] In the relevant PON network topology, one OLT connects to one ODN, and through the ODN connects a certain number of ONUs (e.g., 64 ONUs). In this architecture, since there is only one level of optical splitter between the OLT and the ONUs, the OLT can directly identify which ONU it is connected to. The network topology is clear and easy to manage and troubleshoot.

[0030] However, for some cost-sensitive OLT deployment scenarios, wide-area coverage technology is sometimes required to improve the coverage range of a single OLT. In a wide-area coverage architecture, one OLT connects to N ODNs, and through these N ODNs, connects to N×64 ONUs. In this case, due to the introduction of the wide-area coverage board, one OLT connects to multiple ONUs under the same ODN. Since the OLT connects to the ONUs via two stages of optical splitters, the OLT cannot directly obtain which ODN branch or ODN backbone the ONU passes through to connect to the OLT. This prevents the OLT from directly reconstructing the entire connection topology between the ONUs and the OLT.

[0031] Due to the introduction of wide area coverage technology, the OLT cannot determine the connection relationship between the ONU PON port and the ODN. When a system failure occurs, the OLT cannot determine the ODN to which the fault-associated ONU belongs, making it difficult to troubleshoot and diagnose the fault, which greatly affects network operation and maintenance efficiency and user experience.

[0032] To address the aforementioned issues, this application provides a topology restoration method for a passive optical network (PON) wide-area coverage system. Different delay values ​​are introduced on the optical links between the OLT and each ODN, giving each ODN a unique delay identifier. When the uplink signal from an ONU arrives at the OLT after passing through different ODNs, the signal carries different delay characteristics. The OLT performs delay analysis on the received signal, extracts the delay value experienced by the signal, and then determines the ODN to which the ONU belongs based on a pre-stored mapping relationship between delay values ​​and ODN identifiers. This restores the topology connection relationship, enabling the OLT to accurately restore the topology connection relationship between the ONU and the OLT, thereby improving the efficiency of network fault diagnosis and troubleshooting.

[0033] It should be noted that the optical domain delay used in this application is a signal delay technique commonly used in optical domain processing. It has various implementation methods, including flange-connected delay lines, optical waveguides and their derivative waveguide-type delayers, resonant on-chip continuous delayers and their derivative resonant plate-type delayers, fixed fiber delay coils, and optical switch matrix arrays, etc. This application does not specifically limit these delay techniques.

[0034] Figure 1 A flowchart illustrating the topology restoration method provided in this application is shown below. Figure 1 As shown, this application provides a topology restoration method, including: Step 101: Receive a first signal sent from the passive optical network (PON) port of the optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port that reaches the optical line terminal (OLT) PON port via an optical transmission link; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports.

[0035] In one embodiment, the optical transmission link consists of a first optical transmission link and a second optical transmission link; the first module is disposed on the corresponding first optical transmission link and / or second optical transmission link; Wherein, the first optical transmission link is a passive device, and the second optical transmission link is an active device; The passive device includes at least an optical fiber, a beam splitter, and an optical connector. The active device includes at least an optical amplifier, an optical emitting module, a photodetector module, and an electrical signal driver; or, the active device is a device that aggregates multiple ODN signals to the same OLT PON port.

[0036] In this application, the OLT or the receiver of the OLT's PON port receives a signal sequence (i.e., the first signal) from the ONU. In a wide-area coverage scenario, the OLT is connected to multiple ODNs through a wide-area coverage panel, and each ODN has multiple ONUs connected to it. The uplink transmission path from the ONU to the OLT is as follows: the uplink signal emitted by the ONU is first transmitted through the branch fiber of the ODN to the ODN's optical splitter, and then through the ODN's trunk fiber to the wide-area coverage panel. After being multiplexed by a wavelength division multiplexing (WDM) device within the wide-area coverage panel, it is finally transmitted to the OLT's receiver.

[0037] In one embodiment, the OLT is connected to three ODNs via a wide-area coverage panel to form a wide-area coverage PON system. The optical transmission link from the ONU PON port to the OLT PON port is functionally divided into a first optical transmission link and a second optical transmission link.

[0038] The first optical transmission link is a passive device, consisting of single-mode fiber, a 1:64 optical splitter, and an SC / APC optical connector. It is responsible for aggregating the uplink optical signals from the ONUs to the ODN backbone fiber. The backbone fiber lengths of the three ODNs are 5km, 8km, and 12km, respectively. Their inherent transmission delays differ, but are insufficient to meet the uniqueness requirement for topology reconstruction. The second optical transmission link is an active device, employing a wide-area coverage board that aggregates multiple ODN signals to the same OLT PON port. This board integrates a wavelength division multiplexer (WDM), an optical amplifier (EDFA), and a photodetector module. After multiplexing and power compensation of the three ODN uplink signals, the signals are sent to the OLT receiver.

[0039] The first module (delay module) in this embodiment is deployed in two segments simultaneously. On the first optical transmission link side, delay fibers of different lengths are fused between the backbone fiber of each ODN and the entrance of the wide area coverage panel: ODN-1 adds a 20-meter delay fiber (corresponding to approximately 100ns delay), ODN-2 adds an 80-meter delay fiber (corresponding to approximately 400ns delay), and ODN-3 adds a 160-meter delay fiber (corresponding to approximately 800ns delay). The delay fibers are connected to the backbone fiber via flanges, achieving passive delay. On the second optical transmission link side, an optical switch matrix array is integrated inside the wide area coverage panel as an auxiliary delay fine-tuning device to perform nanosecond-level delay compensation for each ODN branch, ensuring that the total delay value of the three ODNs strictly meets the constraint conditions that they are distinct and easily extracted from the second-order autocorrelation moments.

[0040] In this application, a first module is respectively set on the optical fiber connecting each ODN in the wide area coverage panel to the WDM output of the wide area coverage panel, introducing different first characteristic information (such as time delay value) for each ODN. For example, for the wide area coverage panel in N There are three different ODNs, where a delay T1 is introduced for ODN-1, a delay T2 is introduced for ODN-2, and so on, for ODN-... N Introducing delay T N , where, for any i , j ∈[1, N ], if and only if i = j At that time, T i =T j This indicates that each ODN corresponds to a unique delay value, and the delay values ​​between different ODNs are different.

[0041] In this application, the implementation methods of the first module include, but are not limited to, delay lines based on flange connections, optical waveguides and their derived waveguide delayers, resonant on-chip continuous delayers and their derived resonant plate delayers, fixed fiber delay coils and optical switch matrix arrays, etc., and appropriate delay implementation methods can be selected according to actual engineering needs.

[0042] In this application, based on the aforementioned delay introduction mechanism, all ONUs in the PON network possess the following two characteristics: Feature 1: For all ONUs under the same ODN, the transmission delay experienced by all ONU signals through the ODN to the same OTL or OLT PON port is the same. This is because all ONUs under the same ODN share the same ODN backbone fiber and the same delay module, therefore the delay of the ODN backbone is the same in the transmission path from each ONU to the OTL or OLT PON port.

[0043] Feature 2: For any two ONUs belonging to different ODNs, the transmission delays experienced by the signals from the two ONUs to the same OTL or OLT PON port through their respective ODNs are not the same. This is because different ODNs correspond to different delay values, and these delay values ​​are not identical to each other.

[0044] Each ODN has a corresponding delay value, which can be calculated using a function. F (ODN- i )=T i This represents a one-to-one correspondence between the ODN and the latency T. This mapping is pre-stored on the OLT side. F The correspondence between all inputs and outputs serves as the basis for topology reconstruction.

[0045] Step 102: parse the first feature information and, based on the parsing result, reconstruct the topological connection relationship between the ONU PON port and the OLT PON port. The parsing process can use second-order autocorrelation operation to obtain a second-order autocorrelation moment sequence.

[0046] In this application, after the OLT receiver completes the reception of the signal, it can send the received signal sequence (i.e., the first signal) to the delay analyzer for delay analysis.

[0047] Specifically, let the received signal sequence be... Y [ n ],in, n This is the sampling point number. Y [ n Move right p After that, we get the shift sequence. Y [ n+p Second-order autocorrelation moments R YY [ k Defined as Y [ n ]and Y [ n + p The result of the multiplication and accumulation operation is obtained by adjusting the shift bits. p (or corresponding delay) k By multiplying and accumulating the results under the given conditions, we obtain the second-order autocorrelation moment sequence. R YY [ k ].

[0048] In this application, when the number of shifts... p The strongest correlation exists between the original signal sequence and its shifted sequence when the number of sampling points corresponds exactly to the first characteristic information (time delay) experienced by the signal during transmission is equal to the number of sampling points. At this point, a significant peak will appear in the second-order autocorrelation moment sequence. Therefore, the time delay experienced by the signal can be determined by analyzing the peak position of the second-order autocorrelation moment sequence.

[0049] Furthermore, the obtained second-order autocorrelation moment sequence R YY [ k Peak analysis is performed. First, the maximum, second maximum, and third maximum values ​​in the second-order autocorrelation moment sequence are determined. The maximum value typically appears in... kThe position of 0 (i.e., the autocorrelation value without shift) corresponds to the signal's self-power; the position of the second maximum value corresponds to the main time delay value experienced by the signal during transmission, i.e., the target time delay value. This is because after the signal passes through the time delay module, the original signal and the delayed signal are superimposed at the receiving end, forming a signal structure with time delay characteristics, which manifests as the second maximum peak value in the second-order autocorrelation moment sequence.

[0050] Then, by locating the position of the second maximum value in the second-order autocorrelation moment sequence, the target time delay value experienced by the uplink signal sequence can be obtained.

[0051] Furthermore, the OLT uses a pre-stored mapping relationship between latency values ​​and ODN identifiers. F The acquired target latency value is mapped to the corresponding ODN identifier. Since each ODN corresponds to a unique latency value, and the latency values ​​of different ODNs are different, this mapping relationship is one-to-one, and the target ODN identifier corresponding to the target latency value can be uniquely determined.

[0052] Finally, based on the target ODN identifier, the OLT determines the ODN to which the ONU corresponding to the currently received uplink signal belongs, thereby reconstructing the topological connection relationship between the ONU and the OLT. By traversing the uplink signals of all online ONUs, the OLT can gradually reconstruct the complete topological connection relationship between all ONUs and the OLT in the entire wide-area coverage network, forming a complete network topology map.

[0053] The topology restoration method provided in this application introduces different first feature information on the optical links between the OLT and multiple ONUs. The OLT can accurately obtain the first feature information that the signal has passed through by analyzing the received signal, and then restore the topology connection relationship between the ONU and the OLT based on the first feature information. This solves the technical problem that the OLT cannot determine the ODN to which the ONU belongs in wide-area coverage scenarios, and improves the efficiency of network fault diagnosis and troubleshooting.

[0054] Based on the above embodiments, the OLT PON port is connected to multiple ONU PON ports through different optical transmission links, and a first module is provided on the corresponding optical transmission link; wherein, the first module is used to enable the signals transmitted by different ONU PON ports to carry the corresponding first feature information in the time domain and / or frequency domain; the first feature information corresponds one-to-one with the optical transmission link corresponding to the ONU PON port; the first feature information includes the time delay value between the ONU PON port and the OLT PON port.

[0055] In one embodiment, the first feature information further includes one or more of the signal spectrum, signal amplitude, and signal phase.

[0056] Figure 2 The schematic diagram of the topology restoration principle for wide-area coverage provided in this application can be referred to. Figure 2 As shown in this application, the wide area coverage board is a device that connects the OLT to multiple ODNs. Its function is to aggregate the uplink signals from multiple ODNs and transmit them to the OLT, while simultaneously distributing the downlink signals from the OLT to each ODN. In a wide area coverage PON system, one OLT connects to... N There are multiple ODN connections, and each ODN connects to multiple ONUs (e.g., 64 ONUs), so one OLT can cover... N With 64 ONUs, the coverage of a single OLT is greatly improved.

[0057] WDM (Wide Area Network) is installed inside the wide area coverage panel. Figure 2 (Not shown in the image) is used to perform multiplexing of uplink signals from multiple ODNs. In this application, to achieve intelligent topology restoration, a first module is respectively set on the optical fiber between the wide area coverage board and each ODN, as shown in the reference. Figure 2 As shown, the first module of different lengths used between the wide-area coverage version and the ODN corresponds to different latency values.

[0058] Specifically, for wide area coverage panels N Each of the three different ODNs is connected to the optical fiber of the wide area network panel (WDM) outlet, and is designated as ODN- i The first module is introduced, which corresponds to the introduction of a time delay T. i ,in i ∈[1, N The first module is located between the ODN backbone fiber and the WDM wide area distribution panel. That is, after the uplink signal is transmitted from the ODN to the wide area distribution panel, it first passes through the first module to introduce a time delay, and then enters the WDM for multiplexing.

[0059] In this application, the relationship between the time-delayed signal introduced by the first module and the original signal can be expressed as: the signal finally input to the WDM y ( t ) = 0.5 × x ( t )+0.5× x ( t - Ti ),in, x ( t () represents the original signal. x ( t - Ti (delay) Ti The following signal, y ( tThe signal is the resultant signal after combining. This expression indicates that the original signal and the delayed signal are superimposed with equal weights to form a signal with time delay characteristics.

[0060] In this application, Ti Satisfy the constraints: For any i , j ∈[1, N ], if and only if i = j hour, Ti = Tj This indicates that the latency values ​​corresponding to different ODNs are different, and each ODN has a unique latency identifier.

[0061] In one embodiment, the OLT PON port is connected to three ODNs via three independent optical transmission links, with 64 ONUs connected to each ODN, forming a wide-area coverage PON system. To achieve intelligent topology restoration, a first module is set on each optical transmission link to enable the uplink signals sent by different ONU PON ports to carry corresponding first feature information in the time domain and / or frequency domain.

[0062] Specifically, the first module is deployed using a multi-dimensional feature combination approach. For the first optical transmission link (corresponding to ODN-1), the first module consists of a fixed fiber delay coil and a bandpass filter: the delay coil introduces a fixed 200ns delay, giving the signal a identifiable delay characteristic in the time domain; the bandpass filter allows only 1550nm±0.5nm wavelength components to pass through in the C-band, changing the signal spectrum shape. For the second optical transmission link (corresponding to ODN-2), the first module consists of an electrically adjustable optical attenuator and a phase modulator: the optical attenuator reduces the signal amplitude by 3dB, producing a specific amplitude attenuation characteristic; the phase modulator introduces a fixed π / 4 phase offset to the carrier, giving the signal a identifiable phase characteristic during coherent detection. For the third optical transmission link (corresponding to ODN-3), the first module consists of an optical switch matrix array and a comb-shaped optical filter: the optical switches select delay paths of different lengths to generate a 400ns delay; the comb-shaped optical filter generates periodic passbands and stopbands in the frequency domain, forming a unique spectral envelope characteristic.

[0063] The above three sets of first module configurations enable each of the three optical transmission links to have a unique first feature information, with each feature information corresponding to its corresponding optical transmission link one-to-one, and the feature combinations of different links do not overlap.

[0064] The OLT-side receiver employs a coherent reception architecture, simultaneously detecting the time-domain waveform, spectral distribution, amplitude envelope, and phase information of the uplink signal. The signal processing unit first performs autocorrelation analysis on the time-domain waveform to extract delay features; then, it analyzes the spectral shape through FFT transformation to identify bandpass or comb-shaped spectral features; next, it compares the amplitudes of each branch signal to identify amplitude attenuation features; finally, it extracts phase offset features through phase demodulation. Based on the joint decision of multi-dimensional feature information, the OLT can uniquely determine the optical transmission link traversed by each ONU's uplink signal, thereby reconstructing the topology connection between the ONU and the ODN. This embodiment significantly improves the reliability and anti-interference capability of topology reconstruction through the fusion of time-domain and frequency-domain features.

[0065] Based on the above embodiments, the first feature information of each ONU PON port under the same optical distribution network (ODN) may be the same or different, and the first feature information of all ONU PON ports under different ODNs may be different from each other.

[0066] In a PON network, the optical fiber from the ODN splitter to each ONU is called a branch fiber. The length of the branch fiber may differ between different ONUs, thus the branch delay (i.e., the first characteristic information between the PON ports of different ONUs under the same optical distribution network ODN) may vary. In this application, the branch delay between ONUs under the same ODN can be the same or different, depending on the length configuration of the branch fiber in the actual network deployment.

[0067] When the branch delay between ONUs under the same ODN is the same, all ONUs under the same ODN have the same branch fiber length, so the transmission delay from each ONU to the ODN splitter is the same.

[0068] When the branch delays between ONUs under the same ODN are different, the different ONUs under the same ODN have different branch fiber lengths, so the transmission delay from each ONU to the ODN splitter is different.

[0069] Regardless of the above situation, this application requires that the total latency of all ONUs under different ODNs be different.

[0070] Specifically, for any two ONUs belonging to different ODNs, let ONU- a Belongs to ODN- i ONU- b Belongs to ODN- j ( i ≠ j If T_total_ is satisfied, then T_total_ must be satisfied. a ≠T_total_b .

[0071] When the branch delays of each ONU under the same ODN are the same, as long as the delay values ​​of different ODNs are different, it can be guaranteed that the total delay of all ONUs under different ODNs will be different.

[0072] When the branch delays of ONUs under the same ODN are different, it is necessary to design delay values ​​and branch delays to ensure that the total delay of all ONUs under different ODNs is different and does not overlap, thus guaranteeing the uniqueness of the total delay. For example, suppose there are three ODNs, and the branch delay range of ONUs under each ODN is [0, 50] symbol periods. To ensure that the total delay of all ONUs under different ODNs is different, the delay value of ODN-1 can be selected as 100 symbol periods, the delay value of ODN-2 as 200 symbol periods, and the delay value of ODN-3 as 300 symbol periods. At this time, the total delay range of all ONUs under ODN-1 is [100, 150], the total delay range of all ONUs under ODN-2 is [200, 250], and the total delay range of all ONUs under ODN-3 is [300, 350]. The three ranges do not overlap, satisfying the constraint that the total delays are different.

[0073] Based on the above embodiments, the step of parsing the first feature information and, based on the parsing result, reconstructing the topological connection relationship between the ONU PON port and the OLT PON port includes: Perform a second-order autocorrelation operation on the first signal to obtain the second-order autocorrelation moment sequence corresponding to the first feature information; Peak analysis is performed on the second-order autocorrelation moment sequence to obtain target feature information, wherein the target feature information is the first feature information experienced by the first signal; Based on the mapping relationship between latency value and ODN identifier, the target feature information is mapped to the corresponding target ODN identifier; Based on the target ODN identifier, the topology connection relationship is restored.

[0074] In this application, the OLT is connected to three optical distribution networks (ODN-1, ODN-2, and ODN-3) via a wide area coverage panel. A first module is installed on the optical fiber connecting each ODN to the wide area coverage panel, and the first characteristic information introduced is a distinct delay value: ODN-1 corresponds to a delay T1 = 100 symbol periods, ODN-2 corresponds to a delay T2 = 400 symbol periods, and ODN-3 corresponds to a delay T3 = 800 symbol periods. The OLT side pre-stores a mapping table F between the delay values ​​and ODN identifiers.

[0075] When an ONU sends an uplink signal, the signal is transmitted through its corresponding ODN, carrying the corresponding time delay characteristics, and finally reaches the OLT receiver to form the first signal. Y [ n The OLT signal processing unit first performs a second-order autocorrelation operation on the first signal, and then... Y [ n ] Instead of moving to the right k The sequence after the position Y [ n + k By performing point-by-point multiplication and accumulation, the second-order autocorrelation moment sequence is obtained. R YY [ k Because the signal contains both the original component and the delayed component, R YY [ k ]exist k The maximum value (peak power) appears at =0. k The second-largest peak value occurs at the position equal to the actual delay value.

[0076] Subsequently, R YY [ k Perform peak search and exclude k After finding the maximum value at =0, identify the second maximum value and its position in the remaining sequence. k second Assuming the currently received signal comes from ODN-2, the second-highest value occurs when... k second The position =400 corresponds to 400 symbol periods of target feature information.

[0077] Based on the pre-stored mapping table F, the target feature information 400 is mapped to the corresponding target ODN identifier ODN-2. According to the target ODN identifier, the ONU is marked as belonging to ODN-2, and an association record between the ONU and ODN-2 is established in the topology database. The OLT sequentially performs the above-mentioned second-order autocorrelation operation, peak analysis, feature mapping, and topology marking process on all online ONUs, and finally restores the complete ONU and ODN topology connection diagram, realizing intelligent topology restoration in wide-area coverage scenarios.

[0078] Based on the above embodiments, The step of performing a second-order autocorrelation operation on the first signal to obtain the second-order autocorrelation moment sequence corresponding to the first feature information includes: The second-order autocorrelation moment sequence is obtained by multiplying and accumulating the first signal with the shifted sequence obtained by cyclically shifting the first signal to the right by different sign bits. The right-shifted sign bit corresponding to the peak position of the second-order autocorrelation moment sequence is determined based on the target feature information. In this application, let the first signal sequence received by the OLT receiver be... Y [ n ],in n =0, 1, 2, ... N -1, N The length of the signal sequence. Uplink signal sequence. Y [ n [] is the signal sequence that arrives at the OLT after the original signal sent by the ONU is transmitted through the ODN and delayed by the delay module.

[0079] Furthermore, the first signal sequence Y [ n Move right p After that, we get the shift sequence. Y [ n + p ].in, p The preset shift number is used; then, the first signal sequence is... Y [ n The second-order autocorrelation moment is obtained by multiplying the shift sequence point by point and then accumulating the product results.

[0080] Next, the process of calculating the second-order autocorrelation moment value is repeated for all shift positions to obtain the second-order autocorrelation moment sequence. R YY [ k The formula is: ; Second-order autocorrelation moment sequence R YY [ k [Reflects the signal sequence] Y [ n ] and its own displacement k The degree of correlation between sequences after the last bit. k When =0, it represents the self-power of the signal, which is usually the maximum value of the second-order autocorrelation moment sequence.

[0081] when k When the number of sampling points equals the time delay experienced by the signal during transmission, since the signal contains both the original component and the delayed component, there is a strong correlation between the original signal sequence and the shifted sequence. R YY [ k A second-highest peak will occur. Therefore, this application uses positioning... R YY [ kThe second maximum value of the signal can be used to determine the time delay experienced by the signal.

[0082] Based on the above embodiments, The peak analysis of the second-order autocorrelation moment sequence to obtain target feature information includes: Determine the maximum, second maximum, and third maximum values ​​in the second-order autocorrelation moment sequence; The target feature information is obtained based on the position of the second maximum value in the second-order autocorrelation moment sequence.

[0083] In this application, a second-order autocorrelation moment sequence is obtained. R YY [ k Afterwards, peak analysis is needed to extract time delay information. First, the second-order autocorrelation moment sequence is traversed. R YY [ k Find the maximum value and its corresponding position.

[0084] After excluding the position of the maximum value, the remaining second-order autocorrelation moment sequence values ​​are traversed to find the second-maximum value and its corresponding position. The position corresponding to the second-maximum value is the number of sampling points corresponding to the target feature information that the signal has experienced during transmission. This is because after the signal passes through the first module, the original signal and the delayed signal are superimposed, and in the second-order autocorrelation moment sequence, in addition to the zero-delay main peak, a second-maximum peak will appear at the position corresponding to the time delay value.

[0085] In this application, after excluding the positions of the maximum and second maximum values, the remaining second-order autocorrelation moment sequence values ​​can be traversed to find the third maximum value and its corresponding position. The third maximum value and its position are used for subsequent peak sidelobe ratio (PSLR) calculation, which can serve as a basis for judging the reliability of time delay information extraction.

[0086] Furthermore, based on the determined position of the second maximum value, the target time delay value experienced by the first signal sequence is obtained. In this application, to improve the accuracy of peak positioning, the following optimization method can be adopted: Neighborhood search method. After initially locating the approximate position of the second-highest value, a fine search is performed within a small range (e.g., ±5 sampling points) around that position to find the true peak position. This method can avoid peak position deviation caused by sampling discretization.

[0087] Multi-frame accumulation method. Since the second-order autocorrelation moment sequence of a single measurement may be affected by noise, second-order autocorrelation can be performed on multiple signal frames separately. Then, the second-order autocorrelation moment sequences of multiple frames are accumulated and averaged to obtain a more stable second-order autocorrelation moment sequence, which is then used for peak analysis. This method can effectively suppress the influence of random noise and improve the reliability of time delay estimation.

[0088] Figure 3 For a schematic diagram illustrating the extraction of latency information provided in this application, please refer to the following. Figure 3 As shown, it is assumed that there are three ODNs in the wide-area coverage panel of the PON, and the delays of the three ODNs are 100 symbols, 400 symbols, and 800 symbols, respectively. In this scenario, the OLT receives the uplink signals from the ONUs under each ODN and performs delay analysis based on the delay extraction algorithm of the second-order autocorrelation moment. The delay information recovered from the finally detected signals is as follows: Figure 3 As shown, the time delay extraction algorithm based on the second-order autocorrelation moment can accurately extract the time delay information, enabling the topology reconstruction of the ONU.

[0089] Based on the above embodiments, before obtaining the target feature information according to the position of the second maximum value in the second-order autocorrelation moment sequence, the method further includes: Calculate the peak-to-sidelobe ratio between the second-highest value and the third-highest value; When the peak sidelobe ratio is less than a preset threshold, the OLT receiver is switched from direct detection reception to coherent reception to obtain the amplitude and phase information of the first signal. Based on the amplitude information and the phase information, a new second-order autocorrelation moment sequence is calculated; The target feature information is obtained based on the position of the second maximum value in the new second-order autocorrelation moment sequence.

[0090] During transmission, signals in a PON network may experience various severe fiber optic transmission impairments, such as fiber attenuation, dispersion, nonlinear effects, and connector loss. These impairments can affect the received signal. Y [ n As signal power decreases, signal quality deteriorates. When signal power is too low, noise becomes the dominant component, making time delay information extraction based on second-order autocorrelation moments difficult and potentially leading to erroneous time delay estimates. To improve the accuracy of time delay information extraction, refer to... Figure 2 As shown, in this application, a receiver switching mechanism is introduced. Before obtaining target feature information based on the second-maximum value position, the following judgment and processing steps are first performed: Step 1: Calculate the peak sidelobe ratio (PSLR). Figure 4For a schematic diagram of the peak-to-sidelobe ratio of the second-order autocorrelation moment sequence provided in this application, please refer to [the relevant documentation]. Figure 4 As shown, the Peak-to-Sidelobe Ratio (PSLR) is calculated based on the maximum, second-maximum, and third-maximum values ​​of the second-order autocorrelation moment sequence determined in the above embodiments. The PSLR is defined as the ratio between the second-maximum and third-maximum values. A larger PSLR indicates a more prominent second-maximum peak, less influence from noise and interference, and higher reliability of time delay information extraction. Conversely, a smaller PSLR indicates a smaller difference between the second-maximum peak and the sidelobe peak, greater influence from noise and interference, and lower reliability of time delay information extraction.

[0091] Step two: Determine if PSLR is less than a preset threshold. In this application, the preset threshold can be set to 3dB. In this application, PSLR can be determined through a topology analysis module. When PSLR < 3dB (that is...) R YY [ k The second maximum amplitude is twice that of the third maximum amplitude, indicating that the delay information extraction capability of the Direct Detection (DD) receiver is insufficient and receiver switching is required.

[0092] In this application, the preset threshold of 3dB can be selected based on empirical values ​​derived from numerous simulation experiments. In practical applications, the preset threshold can be adjusted according to factors such as system performance requirements, channel conditions, and bit error rate requirements.

[0093] Step 3: If the PSLR is less than a preset threshold, switch the OLT receiver from DD reception to coherent reception. Since the direct detection receiver only detects the optical power (i.e., amplitude information) of the received signal and cannot obtain the phase information, the output signal-to-noise ratio of the DD receiver is poor when the signal power is low, making it difficult to accurately extract the time delay information. The coherent receiver, by mixing the received signal with the reference optical signal generated by the local oscillator, can simultaneously detect both the amplitude and phase information of the received signal, thereby obtaining more signal characteristics and improving the accuracy of time delay information extraction.

[0094] In this application, the OLT uses an optical switch to achieve receiver switching. Based on the PSLR determination result, the optical switch switches the received signal from the DD receiver path to the coherent receiver path. The switching process must ensure signal continuity and integrity to avoid signal loss or distortion during the switching process.

[0095] Step four: Based on the amplitude and phase information, a new second-order autocorrelation moment sequence is calculated. In coherent reception mode, the formula for calculating the new second-order autocorrelation moment sequence is: ; By introducing phase information, the new second-order autocorrelation moment sequence can more accurately reflect the characteristics of the time delay component in the signal, and can effectively suppress noise interference and highlight the time delay peak even under low signal-to-noise ratio conditions.

[0096] Step 5: Obtain target feature information based on the location of the second maximum value in the new second-order autocorrelation moment sequence. Perform peak analysis on the new second-order autocorrelation moment sequence to determine the maximum, second maximum, and third maximum value. Obtain target feature information based on the location of the second maximum value: In this application, the PSLR calculation and receiver switching decision can be implemented in software within the OLT controller or through hardware circuitry. The switching speed of the optical switch meets the system's real-time requirements, typically requiring switching to be completed on the order of microseconds to avoid impacting normal service transmission.

[0097] Based on the above embodiments, receiving the first signal sent from the ONU PON port includes: In a multi-generation, multi-rate passive optical network system, the first signal is received from the ONUPON ports of different generations and different rates after being transmitted through their respective corresponding ODNs.

[0098] With the development of PON technology, it is becoming increasingly common for different generations of PON technology to coexist in the same network. At the same time, different generations of PON technology support different transmission rates. In multi-generation, multi-rate PON systems, the OLT needs to support the registration and online connection of ONUs with multiple rates, making the network topology more complex.

[0099] This application addresses OLT receiving optical modules of various generations on the OLT side, such as GPON receiving modules, XG-PON receiving modules, XGS-PON receiving modules, and 50G PON receiving modules. These receiving modules support signal reception and processing at different rates and are compatible with ONUs of different generations.

[0100] On the ONU side, each ODN connects to ONUs with various data rates. For example, ODN-1 connects to GPON ONUs and XG-POON ONUs, while ODN-2 connects to XGS-PON ONUs and 50G PON ONUs. The uplink signals emitted by ONUs of different generations and data rates have different frame structures, modulation formats, symbol rates, and other characteristics.

[0101] For each optical fiber connecting an ODN to a wide area coverage panel, there are delayers (i.e., first modules) with different delays. For example, the delay value of ODN-1 is T1, the delay value of ODN-2 is T2, and the delay value of ODN-3 is T3, and T1, T2, and T3 are all different.

[0102] On the OLT side, multi-generational receiving optical modules based on DD detection are deployed to receive optical signals. These modules can identify the uplink signal characteristics of ONUs from different generations and send the received signals to the corresponding processing channels. Subsequently, the signals from each processing channel are uniformly sent to a delay analyzer for delay analysis.

[0103] The delay analysis extracts delay information based on the content of the above embodiments. Specifically, for uplink signal sequences from ONUs of different generations and different speeds, the following processing is performed: First, based on the generational and rate characteristics of the signal, corresponding preprocessing operations are performed, such as filtering, equalization, and clock recovery, to eliminate the differences between signals from different generations and send them uniformly into the time delay analyzer.

[0104] Then, a second-order autocorrelation operation is performed on the preprocessed signal sequence to obtain the second-order autocorrelation moment sequence. Since the symbol rates of signals from different generations are different, the correspondence between the sampling rate and the number of shift bits needs to be adjusted according to the symbol rate of each signal during the second-order autocorrelation operation to ensure the accuracy of the time delay estimation.

[0105] Next, peak analysis is performed on the second-order autocorrelation moment sequence to obtain the target time delay value corresponding to the second maximum value position; and according to the pre-stored mapping relationship between time delay value and ODN identifier, the target time delay value is mapped to the corresponding ODN identifier.

[0106] Finally, based on the ODN identifier, the topological connection relationship between the ONU and the ODN is restored.

[0107] In this application, the total delay experienced by the uplink signal sequences emitted by ONUs of different generations and different rates is different, ensuring the main distinguishing feature of the total delay of ONUs under different ODNs.

[0108] Figure 5 For a topology reconstruction diagram of the multi-generation wide-area coverage PON system provided in this application, please refer to... Figure 5 As shown, on the OLT side, there are multiple generations of OLT receiving optical modules, supporting the registration and online operation of ONUs with various rates such as GPON, XG-PON, and XGS-PON. On the ONU side, each ODN has ONUs with multiple rates. For the optical fiber connecting each ODN to the wide coverage board, there are delay devices with different delays. On the OLT side, multi-generation receiving optical modules based on DD detection are deployed to receive optical signals, which are then sent to a delay analyzer for delay analysis. The delay analysis extracts delay information based on the above-mentioned content and feeds it back to the OLT to reconstruct the entire link topology.

[0109] In another embodiment, reference may be made to Figure 5As shown, on the OLT side, the same OLT receiving optical module with multiple generations supports the registration and online connection of ONUs with multiple rates; on the ONU side, each ODN has ONUs with multiple rates. For the optical fiber connecting each ODN to the wide coverage board, there are delayers with different delays; simultaneously, for the branch optical fibers where different ONUs reside, there are also different first modules. The delay information of ONUs under different ODNs is different, but the delay information between multiple ONUs under the same ODN can be the same. Then, multi-generation receiving optical modules based on DD detection are deployed to receive the optical signal, which is then sent to a delay analyzer for delay analysis. The delay analysis extracts the delay information based on the above-mentioned content and feeds it back to the OLT to reconstruct the entire link topology.

[0110] This application introduces different delay values ​​on the optical links between the OLT and multiple ODNs, extracts delay information using the second-order autocorrelation moment, and combines the peak sidelobe ratio for receiver adaptive switching, thereby realizing the intelligent restoration of the topology connection relationship between the ONU and ODN in a wide-area coverage PON system. It is applicable to various wide-area coverage PON deployment scenarios and has strong compatibility.

[0111] The topology restoration apparatus provided in this application is described below. The topology restoration apparatus described below can be referred to in correspondence with the topology restoration method described above.

[0112] Figure 6 A schematic diagram of the topology reduction apparatus provided in this application is shown below. Figure 6 As shown, this application provides a topology restoration device, characterized in that it includes a receiving module 601 and a topology restoration module 602. The receiving module 601 is used to receive a first signal sent from the passive optical network (PON) port of an optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port that travels through an optical transmission link to the optical line terminal (OLT) PON port. The optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports. The topology restoration module 602 is used to parse the first feature information and, based on the parsing result, restore the topology connection relationship between the ONU PON port and the OLTPON port.

[0113] The topology restoration device provided in this application introduces different first feature information on the optical links between the OLT and multiple ONUs. The OLT can analyze the received signals to accurately obtain the first feature information that the signals have passed through, and then restore the topology connection relationship between the ONUs and the OLT based on the first feature information. This solves the technical problem that the OLT cannot determine the ODN to which the ONU belongs in wide-area coverage scenarios, and improves the efficiency of network fault diagnosis and troubleshooting.

[0114] Figure 7 A schematic diagram of the structure of the electronic device provided in this application, such as... Figure 7 As shown, the electronic device may include: a processor 701, a communications interface 702, a memory 703, and a communication bus 704, wherein the processor 701, the communications interface 702, and the memory 703 communicate with each other via the communication bus 704. The processor 701 can call logical instructions in the memory 703 to execute a topology restoration method, which includes: receiving a first signal sent from the passive optical network (PON) port of the optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port that travels through an optical transmission link to the optical line terminal (OLT) PON port; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports; parsing the first feature information, and based on the parsing result, restoring the topology connection relationship between the ONU PON port and the OLT PON port.

[0115] Furthermore, the logical instructions in the aforementioned memory 703 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0116] On the other hand, this application also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a computer, the computer can execute the topology restoration method provided by the above methods. The method includes: receiving a first signal sent from the passive optical network (PON) port of an optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port that reaches the optical line terminal (OLT) PON port via an optical transmission link; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports; parsing the first feature information, and restoring the topology connection relationship between the ONU PON port and the OLT PON port based on the parsing result.

[0117] In another aspect, this application also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program is implemented to perform the topology restoration method provided in the above embodiments. The method includes: receiving a first signal sent from a passive optical network (PON) port of an optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port that travels through an optical transmission link to an optical line terminal (OLT) PON port; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports; parsing the first feature information, and restoring the topology connection relationship between the ONU PON port and the OLT PON port based on the parsing result.

[0118] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0119] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, 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 can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A topology restoration method, characterized in that, include: The system receives a first signal from the passive optical network (PON) port of the optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port and transmitted through an optical transmission link to the optical line terminal (OLT) PON port; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports. The first feature information is parsed, and based on the parsing result, the topological connection relationship between the ONU PON port and the OLT PON port is restored.

2. The topology restoration method according to claim 1, characterized in that, The OLT PON port is connected to multiple ONU PON ports through different optical transmission links, and a first module is provided on the corresponding optical transmission link; wherein, the first module is used to enable the signals transmitted by different ONU PON ports to carry the corresponding first feature information in the time domain and / or frequency domain; the first feature information corresponds one-to-one with the optical transmission link corresponding to the ONU PON port; the first feature information includes the time delay value between the ONU PON port and the OLT PON port.

3. The topology restoration method according to claim 1, characterized in that, The first characteristic information of each ONU PON port under the same optical distribution network (ODN) may be the same or different, and the first characteristic information of all ONU PON ports under different ODNs may be different from each other.

4. The topology restoration method according to claim 1, characterized in that, The step of parsing the first feature information and, based on the parsing result, reconstructing the topological connection relationship between the ONU PON port and the OLT PON port includes: Perform a second-order autocorrelation operation on the first signal to obtain the second-order autocorrelation moment sequence corresponding to the first feature information; Peak analysis is performed on the second-order autocorrelation moment sequence to obtain target feature information, wherein the target feature information is the first feature information experienced by the first signal; Based on the mapping relationship between latency value and ODN identifier, the target feature information is mapped to the corresponding target ODN identifier; Based on the target ODN identifier, the topology connection relationship is restored.

5. The topology restoration method according to claim 4, characterized in that, The step of performing a second-order autocorrelation operation on the first signal to obtain the second-order autocorrelation moment sequence corresponding to the first feature information includes: The second-order autocorrelation moment sequence is obtained by multiplying and accumulating the first signal with the shifted sequence obtained by cyclically shifting the first signal to the right by different sign bits. The right-shifted sign bit corresponding to the peak position of the second-order autocorrelation moment sequence is determined based on the target feature information.

6. The topology restoration method according to claim 4, characterized in that, The peak analysis of the second-order autocorrelation moment sequence to obtain target feature information includes: Determine the maximum, second maximum, and third maximum values ​​in the second-order autocorrelation moment sequence; The target feature information is obtained based on the position of the second maximum value in the second-order autocorrelation moment sequence.

7. The topology restoration method according to claim 6, characterized in that, Before obtaining the target feature information based on the position of the second maximum value in the second-order autocorrelation moment sequence, the method further includes: Calculate the peak-to-sidelobe ratio between the second-highest value and the third-highest value; When the peak sidelobe ratio is less than a preset threshold, the OLT receiver is switched from direct detection reception to coherent reception to obtain the amplitude and phase information of the first signal. Based on the amplitude information and the phase information, a new second-order autocorrelation moment sequence is calculated; The target feature information is obtained based on the position of the second maximum value in the new second-order autocorrelation moment sequence.

8. The topology restoration method according to claim 1, characterized in that, The receiving of the first signal from the ONU PON port includes: In a multi-generation, multi-rate passive optical network system, the first signal is received from the ONU PON ports of different generations and different rates after being transmitted through their respective corresponding ODNs.

9. The topology restoration method according to claim 2, characterized in that, The optical transmission link consists of a first optical transmission link and a second optical transmission link; the first module is installed on the corresponding first optical transmission link and / or second optical transmission link; Wherein, the first optical transmission link is a passive device, and the second optical transmission link is an active device; The passive device includes at least an optical fiber, a beam splitter, and an optical connector. The active device includes at least an optical amplifier, an optical emitting module, a photodetector module, and an electrical signal driver; or, the active device is a device that aggregates multiple ODN signals to the same OLT PON port.

10. A topology reduction apparatus, characterized in that, include: The receiving module is used to receive a first signal sent from the passive optical network (PON) port of the optical network unit (ONU), wherein the first signal is a signal sent by the ONU PON port that reaches the optical line terminal (OLT) PON port through the optical transmission link; the optical transmission link is used to apply corresponding first feature information to the first signals sent by different ONU PON ports. The topology restoration module is used to parse the first feature information and restore the topology connection relationship between the ONU PON port and the OLT PON port based on the parsing result.

11. An electronic device comprising a processor and a memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the topology restoration method according to any one of claims 1 to 9.

12. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the topology restoration method according to any one of claims 1 to 9.

13. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the topology restoration method according to any one of claims 1 to 9.

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