A service fault recovery method based on optical fiber link loss test

Abstract

The application discloses a service fault recovery method based on optical fiber link loss testing, and relates to the technical field of optical communication service recovery, and comprises the following steps: acquiring an optical fiber routing topology, service parameters and spare optical path resources, dividing service bearing optical links and performing bidirectional loss testing to form a sectional link loss benchmark record; performing fault loss testing according to optical power and service states, matching a reflection curve with the sectional link loss benchmark record, determining a fault-affected optical fiber section and affected services, and forming a link fault diagnosis record; testing candidate recovery paths, retaining current loss of normal optical fiber sections, replacing loss of the fault-affected optical fiber section with actual loss of the candidate recovery paths, and forming a service recovery execution list; locking recovery resources and switching the affected services, and determining a service fault recovery result. The application realizes matching of recovery path optical loss and actual link states and association of the fault-affected optical fiber section and the affected services.

Description

Technical Field

[0001] This invention relates to the field of optical communication service recovery technology, and in particular to a service fault recovery method based on optical fiber link loss testing. Background Technology

[0002] Optical fiber communication networks handle high-capacity, long-distance service transmissions. Their operation and maintenance typically rely on optical transport network management systems, optical power monitoring devices, and optical time-domain reflectometry (OTDR) equipment to detect link status. Conventional service fault recovery methods first identify link anomalies based on transmitted optical power, received optical power, bit error rate, and continuity alarms. Then, by combining reflection curves and resource topology, the fault range is located. Bypass paths or end-to-end recovery paths are searched based on spare fiber cores, spare wavelengths, and optical cross-connect resources. Finally, optical power and service continuity are verified after service switching.

[0003] The above methods still have two limitations: First, the correlation between fault location results and service-bearing segments is relatively coarse, making it difficult to determine faulty segments and affected services by combining bidirectional reflection curves and segment loss changes. Second, candidate recovery paths are mostly evaluated based on topological distance, nominal loss, or historical parameters, without reconstructing the recovery link based on the current loss of normal segments and the measured loss of candidate paths, causing deviations between the expected loss and available loss margin and the actual state. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a service fault recovery method based on optical fiber link loss testing to solve the problems of insufficient accuracy in associating fault-affected sections and affected services, and insufficient matching degree between the optical loss assessment of the recovery path and the actual link status in the existing technology.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a service fault recovery method based on optical fiber link loss testing, comprising: acquiring optical fiber routing topology, service parameters, and backup optical path resources; dividing the service-bearing optical link into optical fiber segments and performing bidirectional loss testing; establishing a correspondence between services and optical fiber segments; and acquiring segment link loss baseline records; performing fault loss testing based on optical power and service status; registering the reflection curve with the segment link loss baseline records; determining the affected optical fiber segments and services, and forming a link fault diagnosis record; searching and testing candidate recovery paths based on the link fault diagnosis record and backup optical path resources; retaining the current loss of normal optical fiber segments; replacing the loss of fault-affected optical fiber segments with the measured loss of candidate recovery paths; calculating the expected link loss and available loss margin after recovery; forming a service recovery execution list; locking recovery resources based on the service recovery execution list; switching affected services using segment-level bypass or end-to-end recovery methods; and determining the service fault recovery result based on received optical power, measured link loss, bit error rate status, and service continuity status.

[0007] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, the fiber optic connection relationship, optical cross-connect relationship, service transmission parameters, spare fiber core information, and spare wavelength information are obtained through an optical transmission network management system, an optical fiber resource management system, and an optical transport network controller. The service-carrying optical link is divided into multiple fiber optic segments using optical distribution frame ports, connectors, optical splitters, optical cross-connectors, optical amplification nodes, and locatable fiber splice points as segment boundaries. When the distance between two adjacent segment boundaries is less than the attenuation dead zone length of the bidirectional loss testing equipment, the fiber transmission portion between the two adjacent segment boundaries is merged into a composite fiber optic segment. Each fiber optic segment is associated with its corresponding physical optical cable segment and common risk group, and the fiber segment start point, fiber segment end point, segment length, and segment transmission direction are recorded.

[0008] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, the service-bearing optical link is traced along the service signal transmission direction according to the service transmitting port, service receiving port, service wavelength, and optical cross-connection relationship; the fiber optic segment numbers are arranged according to the order in which the service signal passes through the fiber optic segments to form an ordered fiber optic segment sequence corresponding to the service identifier; for services with bidirectional transmission direction, a correspondence is established between forward services and forward ordered fiber optic segment sequences, and a correspondence is established between reverse services and reverse ordered fiber optic segment sequences; when the service cross-connection relationship is inconsistent with the physical route in the fiber optic routing topology, the corresponding service is marked as a route pending verification state, and the generation of the corresponding service's segment link loss benchmark record is stopped.

[0009] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, optical time-domain reflectometry is performed in both directions of the service-bearing optical link to obtain forward and reverse reflection curves. Using fixed reflection events in the fiber optic routing topology as location references, the same physical event in the forward and reverse reflection curves is registered to determine the forward and reverse segment losses of each fiber segment. The bidirectional reference loss of each fiber segment is determined based on the forward and reverse segment losses, and the equivalent passive loss of the segment reference is determined based on the loss calibration relationship between the test wavelength and the service wavelength. Loss closure verification is performed by combining the equivalent passive loss of the segment reference, the end-to-end net loss of the service, the node insertion loss, and the actual gain of the optical amplification node for each fiber segment. The verified loss test results are associated with the service identifier, the ordered fiber segment sequence, the physical optical cable segment, and the common risk group to obtain the segment link loss reference record.

[0010] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, the following steps are taken: First, the transmitted optical power, received optical power, optical signal loss status, bit error rate before forward error correction, and service operation management and maintenance continuity status of the service-bearing optical link are collected. Second, the current end-to-end net loss is determined based on the transmitted and received optical power, and compared with the end-to-end reference net loss in the segment link loss reference record to obtain the increase in end-to-end net loss. Third, when the increase in end-to-end net loss, optical signal loss status, bit error rate before forward error correction, or service operation management and maintenance continuity status reaches the fault triggering condition, a bidirectional fault loss test is performed on the service-bearing optical link to obtain the current forward reflection curve and the current reverse reflection curve. Fourth, fixed reflection events are obtained from the segment link loss reference record, and these fixed reflection events are used as registration anchor points to perform event pairing on the current forward reflection curve and the current reverse reflection curve. Fifth, distance coordinate correction is performed on the current forward reflection curve and the current reverse reflection curve based on the registration anchor points, and segment registration is completed according to the fiber segment boundary.

[0011] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, the following steps are taken: First, based on the current forward and reverse reflection curves after segment registration, the current loss of each fiber segment is determined. Then, the current loss is compared with the segment reference loss in the segment link loss reference record to obtain the new loss of each fiber segment. Second, based on the reflection curve termination event, new reflection events, changes in loss of existing reflection events, and the new loss of the segment, the fault event type and the affected fiber segment are determined. Third, based on the position of the fault event in the reflection curve, the physical optical cable segment corresponding to the affected fiber segment, and the common risk group, the fault event location and fault isolation range are determined. Fourth, based on the correspondence between services and fiber segments, services containing the affected fiber segment in the ordered fiber segment sequence are queried to determine the affected services and their corresponding affected status. Fifth, the current loss of the normal fiber segment, the affected fiber segment, the fault event type, the fault event location, the fault isolation range, and the affected services are associated to form a link fault diagnosis record.

[0012] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, the following steps are taken: First, the affected fiber optic segment, fault isolation range, fault-associated physical optical cable segment, fault-associated common risk group, and affected services are obtained from the link fault diagnosis record. Second, the current occupancy status of the spare fiber core, spare wavelength, and optical cross-connect port is obtained based on the spare optical path resource identifier. Third, a recovery path search topology is constructed based on the fiber optic routing topology and the current occupancy status. Fourth, fiber optic segments within the fault isolation range, fault-associated physical optical cable segment, fault-associated common risk group, and unavailable resources are deleted from the recovery path search topology. Fifth, a segment-level bypass path is searched using the optical cross-connect nodes at both ends of the affected fiber optic segment as the bypass start and bypass end points. Sixth, an end-to-end recovery path is searched using the sending and receiving ports of the affected services as the recovery start and recovery end points. Finally, the segment-level bypass path and the end-to-end recovery path are combined into a candidate recovery path set.

[0013] As a preferred embodiment of the service fault recovery method based on optical fiber link loss testing described in this invention, the method involves: establishing temporary test connections at optical cross-connect nodes according to a set of candidate recovery paths; performing bidirectional loss testing on passive test segments in the candidate recovery paths; obtaining the measured loss of the candidate recovery paths at the service wavelength based on the bidirectional loss test results and the loss calibration relationship between the test wavelength and the service wavelength; obtaining the insertion loss of newly added optical cross-connects and the actual gain of optical amplification nodes based on the recovery start and end points of the candidate recovery paths; determining the replaced optical fiber segments and the retained normal optical fiber segments from the ordered sequence of affected optical fiber segments based on the recovery start and end points of the candidate recovery paths; obtaining the current loss of the retained normal optical fiber segments from the link fault diagnosis records; and establishing a loss replacement relationship between the current loss of the retained normal optical fiber segments, the measured loss of the candidate recovery paths, and the replaced optical fiber segments.

[0014] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, the following steps are taken: The current loss of the retained normal fiber optic segment and the measured loss of the candidate recovery path are summarized, the insertion loss of the newly added optical cross-connect is added, and the actual gain of the optical amplification node is subtracted to obtain the expected link loss after recovery; Based on the difference between the allowed end-to-end net loss of the affected service and the expected link loss after recovery, the available recovery loss margin is obtained; Candidate recovery paths with an available recovery loss margin not lower than the safe recovery loss margin threshold, and whose service wavelength, transmission rate, modulation method, forward error correction configuration, and recovery resource status meet the service transmission requirements are selected to obtain available candidate paths; Available candidate paths are arranged according to the degree of fault risk isolation, available recovery loss margin, number of fiber optic segments to be changed, and number of optical cross-connect nodes to be operated; The affected service, available candidate paths, expected link loss after recovery, available recovery loss margin, resources to be locked, and recovery execution order are associated to form a service recovery execution list.

[0015] As a preferred embodiment of the service fault recovery method based on fiber optic link loss testing described in this invention, the candidate recovery path and the resources to be locked corresponding to the affected service are read according to the recovery execution order in the service recovery execution list, the current status of the spare fiber core, spare wavelength, optical cross-connect port, wavelength conversion port and optical amplification node are re-verified, and atomic locking is performed on the recovery resources that have passed the verification. When the candidate recovery path is a segment-level bypass path, the normal fiber segments outside the fault-affected fiber segment remain unchanged, and a bypass optical path is established between the optical cross-connect nodes at both ends of the fault-affected fiber segment. When the candidate recovery path is an end-to-end recovery path, an end-to-end recovery optical path that avoids the fault-affected fiber segment is established between the service transmitting port and the service receiving port. Depending on the degraded transmission status or complete interruption status of the original service-bearing optical link, the affected service is switched from the original service-bearing optical link to the established segment-level bypass optical path or end-to-end recovery optical path. Within the recovery verification time window, the transmitted optical power, received optical power, bit error rate before forward error correction, optical signal loss status, and service operation management and maintenance continuity status are collected after recovery. The measured link loss after recovery is determined based on the transmitted and received optical power. The received optical power after recovery, the measured link loss after recovery, the deviation between the measured link loss after recovery and the expected link loss after recovery, the bit error rate before forward error correction, and the continuity status of service operation management and maintenance are compared with the corresponding allowable conditions to determine the recovery verification result of the current candidate recovery path. When the recovery verification result meets all allowable conditions, the corresponding affected service is determined to have been successfully recovered, and the locked recovery resources are converted to a service occupancy status. When the recovery verification result does not meet all allowable conditions, the recovery resources occupied by the current candidate recovery path are released, and the next candidate recovery path is selected according to the service recovery execution list to form the service fault recovery result.

[0016] The beneficial effects of this invention are as follows: By dividing the service-carrying optical link into multiple fiber segments, performing bidirectional loss tests on each fiber segment, and establishing a correspondence between services and ordered fiber segment sequences, the link loss benchmark is refined from end-to-end overall recording to segment-level recording, improving the correlation accuracy between fault loss changes and specific fiber segments and carried services; by retaining the current loss of normal fiber segments when a fault occurs, replacing the loss of fault-affected fiber segments with the measured loss of candidate recovery paths, and combining the insertion loss of newly added nodes and the actual gain of optical amplification nodes to calculate the expected link loss after recovery, the reconstruction of the recovery link loss based on the current link state and the measured path state is realized, improving the matching degree between the recovery path loss assessment and the actual operating state. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a service fault recovery method based on fiber optic link loss testing.

[0019] Figure 2 A flowchart for recording link fault diagnosis.

[0020] Figure 3 A flowchart for the execution checklist for business resumption.

[0021] Figure 4 A flowchart for determining the outcome of business failure recovery. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0025] Reference Figures 1-4 This is one embodiment of the present invention, which provides a service fault recovery method based on optical fiber link loss testing, including the following steps: S1. Obtain the fiber optic routing topology, service parameters, and backup optical path resources. Divide the service-bearing optical links into fiber optic segments and perform bidirectional loss tests. Establish the correspondence between services and fiber optic segments and obtain the segment link loss baseline records. Furthermore, the optical transmission network management system, optical fiber resource management system, and optical transmission network controller acquire optical fiber connection relationships, optical cross-connect relationships, service transmission parameters, spare fiber core information, and spare wavelength information.

[0026] Specifically, the optical transmission control terminal reads the optical fiber routing topology from the optical transmission network management system, the optical cable segment, fiber core, spare fiber core and their physical routes from the optical fiber resource management system, and the service cross-connection relationship, wavelength occupancy status, spare wavelength, wavelength conversion capability and optical amplification node operating parameters from the optical transmission network controller, and associates them according to the device identifier, port identifier and optical fiber connection identifier.

[0027] The fiber optic routing topology includes optical line terminals, optical distribution frames, optical cross-connect nodes, optical splitting nodes, optical amplification nodes, fiber splicing points, connectors, and the connection relationships between fiber segments and fiber cores between nodes. Service parameters include service identifier, service transmitting port, service receiving port, transmission direction, service wavelength, transmission rate, modulation scheme, forward error correction configuration, receiving sensitivity, maximum allowable received optical power, allowable upper limit of bit error rate before forward error correction, service continuity judgment conditions, service level, and allowable end-to-end net loss. Backup optical path resources include backup fiber core identifier, backup wavelength identifier, backup optical cross-connect port identifier, wavelength conversion node, wavelength conversion port, resource start point, resource end point, physical fiber segment identifier, common risk group identifier, and resource occupancy status.

[0028] It should be noted that the optical transmission network management system in this embodiment is a functional name for the optical fiber communication network management side system. When adopting an optical transport network architecture, the optical transmission network management system is implemented by the optical transport network management system described in the background art. Therefore, the optical transmission network management system and the optical transport network management system correspond to the same management side system in this embodiment and do not represent two independent systems. The optical transport network controller is used to perform optical cross-connect configuration, wavelength resource scheduling, and recovery path establishment, and belongs to a different functional entity from the optical transport network management system.

[0029] It should also be noted that the fiber optic routing topology, service parameters, and backup optical path resources are derived from resource records generated during the construction, commissioning, and operation of the optical transmission network; the resource occupancy status serves as a snapshot of the status at the time of baseline formation, and the real-time status is reread when searching for candidate recovery paths and performing service switching.

[0030] Furthermore, the optical fiber link carrying the service is divided into multiple fiber segments, using optical distribution frame ports, connectors, optical splitting nodes, optical cross-connect nodes, optical amplification nodes, and locatable fiber splice points as segment boundaries.

[0031] Among them, an optical fiber link refers to an optical signal transmission path consisting of optical fiber segments and connecting nodes along the way, while a service-bearing optical link refers to the transmission path in an optical fiber link that actually carries the corresponding service signal between the service transmitting port and the service receiving port according to the current optical cross-connection relationship; subsequent segmentation, loss testing and fault recovery of the service-bearing optical link are all considered processing of the corresponding optical fiber link.

[0032] Specifically, the optical transmission control terminal determines the boundary of each segment along the actual physical route from the service transmission port to the service reception port, divides the optical fiber transmission part between two adjacent segment boundaries into an optical fiber segment, and uses the optical amplification node as the boundary of the adjacent optical fiber segment, so that the optical fiber segment only records the loss of optical fiber and passive devices.

[0033] Furthermore, when the distance between the boundaries of two adjacent segments is less than the attenuation dead zone length of the bidirectional loss test equipment, the fiber transmission portion between the boundaries of the two adjacent segments is merged into a composite fiber segment.

[0034] At the same time, adjacent connection events that cannot be independently distinguished by the reflection curve under the current test pulse and the optical fibers between them are merged and recorded, and the boundaries of each segment before merging are saved as the event locations within the composite optical fiber segment so as to limit the fault location range after a fault occurs.

[0035] It should be noted that the bidirectional loss testing equipment uses optical time-domain reflectometry (OTDR) equipment; the attenuation dead zone length is read from the equipment parameter record or technical manual of the bidirectional loss testing equipment and determined in conjunction with the current test pulse width and reflection event intensity; when the pulse width increases or the reflection event intensifies, the attenuation dead zone length increases accordingly. The attenuation dead zone length of commonly used single-mode fiber testing equipment is usually 2 to 15 meters, specifically using the value calibrated by the equipment under the current test parameters. The typical attenuation dead zone of existing optical time-domain reflectometry equipment is about 2 to 5 meters, and about 12 meters for some remote testing equipment. At the same time, the equipment manufacturers clearly state that the attenuation dead zone increases with the increase of the test pulse width.

[0036] Furthermore, each fiber segment is associated with its corresponding physical fiber cable segment and common risk group, and the fiber segment start point, fiber segment end point, segment length, and segment transmission direction are recorded.

[0037] Specifically, each fiber segment is assigned a fiber segment number, and the fiber type, number of splice points within the segment, physical cable segment identifier, common risk group identifier, and segment transmission direction are recorded. The actual gain of the optical amplifier node is recorded as an independent gain data record for the service-bearing optical link and is not included in the passive loss of the fiber segment.

[0038] Among them, the common risk group is used to record fiber optic segments that share the same optical cable sheath, duct, pole line or equipment room risk node.

[0039] Furthermore, based on the service transmission port, service reception port, service wavelength, and optical cross-connection relationship, the service bearer optical link is traced along the service signal transmission direction.

[0040] This involves acquiring currently active optical cross-connections and fiber core connections node by node, starting from the service transmission port, all the way to the service reception port, to avoid substituting the actual bearer path with the shortest topology path between service endpoints.

[0041] Furthermore, the fiber segment numbers are arranged according to the order in which the service signals pass through the fiber segments, forming an ordered sequence of fiber segments corresponding to the service identifier.

[0042] At the same time, the ordered fiber segment sequence is bound to the service identifier, service wavelength, transmitting port, receiving port and transmission direction, so that the affected services can be queried in reverse based on the fiber segment affected by the fault.

[0043] Furthermore, for services with bidirectional transmission, a correspondence is established between forward services and forward ordered fiber segment sequences, and between reverse services and reverse ordered fiber segment sequences.

[0044] Specifically, when the same fiber optic segment carries multiple services, each service identifier is associated with the same fiber optic segment number, forming a many-to-many correspondence between services and fiber optic segments.

[0045] Furthermore, when the cross-connection relationship of services is inconsistent with the physical routing in the fiber optic routing topology, the corresponding service is marked as a route pending verification state, and the generation of the corresponding service's segment link loss baseline record is stopped.

[0046] It should be noted that after the route verification is completed, an ordered sequence of optical fiber segments is re-formed according to the currently effective optical cross-connection relationship to avoid discrepancies between the reference loss and the actual service carrying path.

[0047] Furthermore, optical temporal reflectance tests are performed in both directions of the service-bearing optical link to obtain forward and reverse reflectance curves.

[0048] Specifically, remote optical testing units are set up at both ends of the service-bearing optical link. The optical fiber carrying the service uses a monitoring wavelength isolated from the service wavelength and is connected through a wavelength division multiplexer and an optical filter. The optical fiber not carrying the service uses the test wavelength supported by the equipment.

[0049] It should be noted that the test wavelength, measurement distance, pulse width, fiber refractive index, sampling interval, and averaging number are set according to the fiber type, the length of the service-bearing optical link, and the equipment manual; the test optical power under service-bearing conditions shall not exceed the upper limit of the monitoring optical power allowed by the optical transceiver, optical amplifier, and wavelength division multiplexing equipment.

[0050] It should be noted that the upper limit of the monitoring optical power is determined based on the minimum value among the maximum allowable input optical power of the optical transceiver at the monitoring wavelength, the maximum allowable input optical power of the monitoring channel of the optical amplifier, and the rated power of the monitoring port of the wavelength division multiplexing equipment, with a safety margin of 1 dB to 3 dB reserved on the basis of the minimum value. When performing online testing using a monitoring wavelength of 1625 nm or 1650 nm, the average output power of the monitoring light injection end is usually taken as -10 dBmW to 0 dBmW. The specific value is based on the output capability of the test equipment and the technical parameters of the optical devices along the way. When the upper limit of the monitoring optical power specified by any equipment is lower than -10 dBmW, the average output power of the monitoring light injection end is determined by deducting the safety margin of 1 dB to 3 dB from the upper limit of the monitoring optical power specified by the corresponding equipment.

[0051] Online fiber optic testing typically uses filtered 1625 nm or 1650 nm wavelengths. Existing commercial online testing equipment offers light source output power specifications such as -8 dBmW, -7 dBmW, and -3 dBmW.

[0052] Furthermore, using fixed reflection events in the fiber optic routing topology as location references, the same physical event in the forward and reverse reflection curves is registered to determine the forward and reverse segment losses of each fiber optic segment.

[0053] Specifically, loss tests are performed 3 to 5 times in each of the two directions under the same test parameters. The median value of the loss from multiple tests on the same fiber segment in the same direction is taken. Then, the distance coordinates of the forward and reverse reflection curves are unified by the reflection events of connectors, optical splitters, and link ends with fixed positions, and the test results belonging to the same physical segment are paired.

[0054] It should be noted that the number of repetitions of the loss test is determined according to the test specifications of the bidirectional loss test equipment, the equipment repeatability index, and the acceptance test requirements of the fiber optic link project, and is written into the test control parameter table, usually 3 to 5 times. Initially, 3 loss tests are performed along the same test direction. When the difference between the maximum and minimum values ​​of the 3 test losses in the same fiber segment does not exceed the allowable deviation of unidirectional test repeatability, the median value of the 3 test losses is taken. When the difference between the maximum and minimum values ​​exceeds the allowable deviation of unidirectional test repeatability, 1 to 2 additional loss tests are performed to bring the total number of tests to 4 to 5, and the maximum, minimum, and median values ​​of the corresponding test losses are re-determined. After the total number of tests reaches 5, if the difference between the maximum and minimum values ​​still exceeds the allowable deviation of unidirectional test repeatability, the test results of this group in the current direction are discarded and the loss test is re-performed.

[0055] It should also be noted that the difference between the maximum and minimum values ​​of loss in multiple tests in the same direction shall not exceed the allowable deviation of unidirectional test repeatability. The allowable deviation of unidirectional test repeatability is determined based on the equipment measurement repeatability, link length and acceptance results, and is usually taken as 0.2 dB to 1.0 dB. The allowable deviation of position matching for the same physical event is determined based on the sampling interval, pulse width and event positioning accuracy, and is usually taken as 2 meters to 20 meters.

[0056] Furthermore, the bidirectional reference loss of each fiber segment is determined based on the forward segment loss and the reverse segment loss, and the equivalent passive loss of the segment reference is determined based on the loss calibration relationship between the test wavelength and the service wavelength.

[0057] Specifically, the bidirectional reference loss of the optical fiber segment is expressed as: ; in, Indicates the first The bidirectional reference loss of each fiber segment, in decibels. Indicates the first The median forward section loss of each fiber segment, in decibels. Indicates the first The median reverse segment loss of each fiber segment, in decibels. Indicates the fiber optic segment number.

[0058] It should be noted that by averaging the forward and reverse section losses, the impact of the difference in backscattering characteristics between the two sides of the splice on the unidirectional loss results is reduced; if no effective reflection curve is obtained in either direction, the corresponding fiber section is marked as a bidirectional test incomplete state, and the test in the missing direction is re-executed.

[0059] When the test wavelength is the same as the service wavelength, the bidirectional reference loss is used as the equivalent passive loss of the section reference.

[0060] When the test wavelength is inconsistent with the service wavelength, the equivalent passive loss of the section reference is expressed as: ; in, Indicates the first The equivalent passive loss of each fiber segment at the service wavelength, expressed in decibels. Indicates the first The fiber attenuation coefficient of each fiber segment at the service wavelength, expressed in decibels per kilometer. Indicates the first The fiber attenuation coefficient of each fiber segment at the test wavelength, expressed in decibels per kilometer. Indicates the first The length of each fiber optic segment, in kilometers. Indicates the first The insertion loss correction amount for passive devices in a fiber segment when switching from the test wavelength to the service wavelength, expressed in decibels.

[0061] It should be noted that the fiber attenuation coefficient is obtained based on the fiber model's factory parameters, engineering acceptance records, or multi-wavelength measurement records. Taking commonly used single-mode fiber as an example, it is typically 0.30 dB / km to 0.40 dB / km at the 1310 nm service wavelength, 0.17 dB / km to 0.30 dB / km at the 1550 nm service wavelength, and 0.20 dB / km to 0.30 dB / km at the 1625 nm test wavelength. The insertion loss correction is determined by the cumulative difference in insertion loss between connectors, optical splitters, and wavelength division multiplexers within the current fiber segment at the service wavelength and the test wavelength. The insertion loss correction for a single or a small number of passive devices is typically -0.5 dB to 0.5 dB, while that for multiple passive devices is typically -1.0 dB to 1.0 dB. The specific value depends on the device's technical parameters or multi-wavelength calibration results.

[0062] Furthermore, loss closure verification is performed by combining the segment benchmark equivalent passive loss, service end-to-end net loss, node insertion loss, and actual gain of optical amplification nodes for each fiber segment. The verified loss test results are then associated with service identifiers, ordered fiber segment sequences, physical optical cable segments, and common risk groups to obtain segment link loss benchmark records.

[0063] Specifically, during stable operation, the transmitted optical power and received optical power are read synchronously, and the end-to-end reference net loss is expressed as: ; in, Indicates the first The end-to-end baseline net loss for this service, in decibels. Indicates the first The transmit optical power of this service, measured in decibels and milliwatts. Indicates the first The received optical power of this service, measured in decibels and milliwatts. Indicates the business sequence number.

[0064] Furthermore, by summing the equivalent passive losses of the service segments and combining them with the insertion losses of nodes outside the test reference plane and the actual gains of the optical amplification nodes, the loss closure deviation is calculated and expressed as: ; in, Indicates the first Loss closure deviation of the item, in decibels. Indicates the first The ordered set of fiber segment numbers corresponding to each service item. Indicates the first The section reference equivalent passive loss of each fiber segment at the service wavelength. Indicates the first The total insertion loss of optical ports, filters, and optical cross-connect devices located outside the bidirectional loss test reference plane in this service, expressed in decibels. Indicates the first The total actual gain of the optical amplification nodes through which the service passes, expressed in decibels.

[0065] It should be noted that the node insertion loss is obtained from the equipment parameters, acceptance records, or commissioning test records, and the actual gain of the optical amplification node is obtained from the operation monitoring records; when there is no optical amplification node or the test reference plane has covered all passive devices, the corresponding total gain or the total node insertion loss is taken as 0.

[0066] The allowable threshold for loss closure is determined based on the bidirectional loss test error, optical power monitoring error, number of fiber segments, and node insertion loss error, and is typically set to 0.5 dB to 2.0 dB. If the loss closure threshold is exceeded after three consecutive retests, the corresponding service will be marked as a baseline pending review status.

[0067] It should be noted that the number of loss closure retests is determined based on the repeatability index of the bidirectional loss test equipment, the stability of optical power monitoring, and the acceptance rules of the fiber optic link project, and is written into the test control parameter table. It is usually configured to be 2 to 5 times; in this embodiment, 3 consecutive times are taken. When the loss closure deviation obtained from 3 consecutive retests exceeds the allowable threshold for loss closure, it is determined that the current segment link loss benchmark has not passed the verification.

[0068] Furthermore, the verified services are correlated with the fiber segment correspondence, forward segment loss, reverse segment loss, segment reference equivalent passive loss, end-to-end reference net loss, node insertion loss, actual gain of optical amplification nodes, and loss closure deviation to form a segment link loss reference record.

[0069] The segment link loss baseline record also includes test wavelength, test parameters, baseline formation time, baseline validity status, and test control parameters. The test control parameters include monitoring cycle, end-to-end net loss increase threshold, bit error rate warning threshold before forward error correction, number of consecutive abnormal monitoring cycles, segment new loss threshold, recovery loss safety margin threshold, recovery verification time window, recovery verification sampling cycle, expected loss deviation threshold after recovery, and resource lockout allowed duration.

[0070] It should be noted that the test control parameters are predetermined based on the equipment measurement accuracy, normal fluctuation range of the link, service level, equipment response time, and allowable service recovery time, and are saved along with the segment link loss benchmark record. The thresholds are not temporarily lowered in subsequent steps.

[0071] S2. Perform fault loss tests based on optical power and service status, register the reflection curve with the segment link loss benchmark record, determine the fiber segment affected by the fault and the affected services, and form a link fault diagnosis record. Furthermore, the system acquires the transmit optical power, receive optical power, optical signal loss status, bit error rate before forward error correction, and service operation management and maintenance continuity status of the optical link carrying the service.

[0072] Specifically, the optical transmission control terminal reads optical power from the service transmission port and the service reception port according to the monitoring period in the segment link loss baseline record, and reads optical signal loss alarm, forward error correction statistics and service operation management and maintenance continuity detection results from the optical transport network controller.

[0073] It should be noted that the transmitted optical power and received optical power are derived from the digital diagnostic monitoring interface or optical power monitoring module of the optical transceiver equipment; the bit error rate before forward error correction and the continuity status of service operation management and maintenance are derived from the statistical register of the optical transmission equipment and the detection results of optical transmission network path monitoring, Ethernet continuity detection and corresponding service protocols, respectively.

[0074] Furthermore, the current end-to-end net loss is determined based on the transmitted optical power and received optical power, and then compared with the end-to-end reference net loss in the segment link loss reference record to obtain the increase in end-to-end net loss.

[0075] Specifically, the current end-to-end net loss is expressed as: ; in, Indicates the first The current end-to-end net loss of the service, in decibels. Indicates the first The current transmit optical power of this service, in decibels and milliwatts. Indicates the first The current received optical power for this service, in decibels and milliwatts. This indicates the business sequence number that has been determined in step one.

[0076] The increase in end-to-end net loss is expressed as: ; in, Indicates the first The increase in end-to-end net loss for this business, in decibels. Indicates the first The current end-to-end net loss of the business. This indicates the first step determined in step one. End-to-end baseline net loss for the business.

[0077] It should be noted that no less than 3 sets of transmitted optical power and received optical power are read in each monitoring cycle and the median value is taken respectively; when the service-bearing optical link includes an optical amplification node, the current end-to-end net loss is only used as the fault loss test trigger quantity and is not directly used as the passive fiber loss.

[0078] The number of optical power sampling groups in each monitoring cycle is determined based on the monitoring cycle length, the refresh cycle of the optical power monitoring equipment, and the test control parameter table, and is usually configured as 3 to 10 groups. When the number of effective samples is less than 3 groups, the median value of transmitted optical power and the median value of received optical power in the current monitoring cycle are not calculated, and the current monitoring cycle is marked as insufficient monitoring data.

[0079] Furthermore, when the increase in end-to-end net loss, the state of optical signal loss, the bit error rate before forward error correction, or the continuity of service operation management and maintenance reaches the fault triggering condition, a bidirectional fault loss test is performed on the service-bearing optical link to obtain the current forward reflection curve and the current reverse reflection curve.

[0080] Specifically, when the increase in end-to-end net loss continuously reaches the end-to-end net loss increase threshold, or the bit error rate before forward error correction continuously reaches the warning threshold, a loss anomaly triggering flag is generated; when optical signal loss or service operation management and maintenance continuity is detected, a loss anomaly triggering flag is directly generated.

[0081] It should be noted that the threshold for the increase in end-to-end net loss is usually set at 0.5 dB to 3 dB, the warning threshold for bit error rate before forward error correction is usually set at 80% to 95% of the upper limit acceptable to the equipment, and the number of continuous abnormal monitoring cycles is usually set at 2 to 5. When the transmitted optical power is abnormal but the link net loss, bit error rate and continuity are normal, it is marked as a state pending verification of the transmitting port and the fiber segment fault test is not triggered.

[0082] Furthermore, after generating the loss anomaly trigger flag, the current service wavelength, ordered fiber segment sequence, and optical cross-connection relationship are verified to be consistent with those when the reference was formed.

[0083] When consistent, the benchmark test parameters are used, and 3 to 5 fault loss tests are performed from both ends of the link respectively. The median value of the backscatter power at the same sampling location is taken to form the current forward reflection curve and the current reverse reflection curve.

[0084] It should be noted that when the routing or service wavelength has changed, the original segment link loss baseline record is marked as invalid and step one is re-executed; the remote optical test unit is controlled through an independent management channel, so that tests can still be performed from both sides of the fault location after the fiber is broken.

[0085] Furthermore, fixed reflection events are obtained from the segment link loss baseline record, and the fixed reflection events are used as registration anchors to perform event pairing on the current forward reflection curve and the current reverse reflection curve.

[0086] Specifically, connector reflection events, optical splitter node reflection events, fiber splicing events, link end reflection events, and reflection curve termination events are extracted from the current reflection curve. The current fixed reflection event with a position difference not exceeding the allowable deviation for event position matching and with the same transmission direction sequence is identified as the same physical event as the reference fixed reflection event.

[0087] It should be noted that the reflection event identification uses the mature event analysis program built into the optical time domain reflectance testing equipment; the allowable deviation for event location matching follows the values ​​in the segment link loss benchmark record.

[0088] Furthermore, distance coordinate correction is performed on the current forward and reverse reflection curves based on the registration anchor points, and segment registration is completed according to the fiber segment boundaries.

[0089] Specifically, between two adjacent registration anchor points, segmented linear distance correction is performed based on the position difference between the anchor points in the current reflection curve and the reference reflection curve. The sampling position of the current reflection curve is mapped to the reference link distance coordinates, and then assigned to the corresponding optical fiber segment according to the optical fiber segment start point and optical fiber segment end point.

[0090] It should be noted that when the current reflection curve terminates prematurely, the last fixed reflection event that completed registration before the termination position is retained, and the termination position is mapped to the corresponding fiber segment accordingly; distance coordinate correction does not change the backscattering power of the reflection curve.

[0091] Furthermore, based on the current forward reflection curve and the current reverse reflection curve after the segment registration is completed, the current equivalent passive loss of each optical fiber segment is determined, and the current equivalent passive loss is compared with the segment benchmark equivalent passive loss in the segment link loss benchmark record to obtain the new loss of each optical fiber segment.

[0092] Specifically, the current forward segment loss and the current reverse segment loss are calculated according to the fiber segment boundary, and the median value from multiple tests is taken. The current equivalent passive loss is expressed as: ; in, Indicates the first The current equivalent passive loss of each fiber segment, in decibels. Indicates the first The median forward segment loss of each fiber segment, in decibels. Indicates the first The median reverse segment loss of each fiber segment. This indicates the first step formed. The segment reference equivalent passive loss of each fiber segment This indicates the first step formed. Median forward segment loss of each fiber segment. This indicates the first step formed. Median reverse segment loss of each fiber segment.

[0093] It should be noted that when both directions are valid, bidirectional results are used; when only one direction is valid, the equivalent passive loss of the section reference is superimposed with the change in the current section loss relative to the reference section loss in the same direction; when there are no valid results in both directions, it is marked as an unreachable state of loss testing, and the section where the reflection curve terminates is handled according to the fiber breakage judgment rules.

[0094] Specifically, the additional loss is determined according to the following formula: ; in, Indicates the first The increase in loss per fiber segment, expressed in decibels. Indicates the first The current equivalent passive loss of each fiber segment, Indicates the first The segment reference equivalent passive loss of each fiber segment.

[0095] It should be noted that when the new loss is less than 0, the actual calculation result is retained to record loss fluctuations, but the corresponding fiber segment is not identified as a loss-increased segment.

[0096] Furthermore, based on the termination event of the reflection curve, the new reflection event, the loss change of the original reflection event, and the new loss in the segment, the fault event type and the fiber segment affected by the fault are determined.

[0097] Specifically, when the reflection curve terminates within the fiber segment and the positioning results in both test directions are consistent, it is determined to be a fiber breakage type fault; when a new reflection event occurs or the loss of an existing reflection event increases and reaches the segment's new loss threshold in at least two consecutive tests, it is determined to be a point loss type fault; when no new reflection event occurs but the attenuation slope increases within a continuous distance and the cumulative new loss reaches the segment's new loss threshold, it is determined to be a distributed loss type fault.

[0098] It should be noted that the threshold for newly added loss in a section is typically set between 0.2 dB and 1.0 dB; the continuous distance range of distributed loss is not less than 5 sampling intervals and not less than the spatial resolution distance corresponding to the current test pulse. When multiple adjacent sections belong to the same physical optical cable segment and exhibit continuous attenuation changes, they are merged into one distributed fault impact area.

[0099] It should be noted that when the fault triggering conditions are met but no abnormal fiber segment loss is identified, the optical transceiver or optical amplifier will be transferred to the equipment fault verification process and will not enter the automatic recovery process based on fiber segment loss replacement.

[0100] Furthermore, based on the location of the fault event in the reflection curve, the physical optical cable segment corresponding to the affected optical fiber segment, and the common risk group, the location of the fault event and the scope of fault isolation are determined.

[0101] Specifically, fiber breakage faults are identified by the termination position of the reflection curve, point loss faults by the location of the event loss increase, and distributed loss faults by the start and end points of the continuous attenuation anomaly range. The fault event locations are then mapped to physical optical cable segments and common risk groups.

[0102] Specifically, when the distance between the fault event location and the segment boundary does not exceed the allowable deviation for event location matching, the adjacent fiber segments on both sides of the boundary are included in the fault isolation range; when the fault event is located inside the segment, the corresponding fiber segment is included in the fault isolation range; for distributed loss type faults, all segments traversed by the continuous abnormal range are included in the fault isolation range.

[0103] It should be noted that the fault isolation range is used to exclude resources within the fault location and its positioning error range during subsequent path search, and does not mean that the physical optical cable on site will be disconnected immediately.

[0104] Furthermore, based on the correspondence between services and fiber segments, the services that include fault-affected fiber segments in the ordered fiber segment sequence are queried to determine the affected services and their corresponding affected status.

[0105] Specifically, services that pass through the affected fiber optic segment are queried according to the transmission direction. When forward and reverse services use different fiber cores, only services using the faulty fiber core are written into the affected service set. When they share the same fiber core, services in both directions that pass through the affected fiber optic segment are written into the affected service set.

[0106] When optical signal loss or interruption of service operation, management and maintenance continuity occurs, it is determined to be a service interruption state; when the service remains continuous but the increase in end-to-end net loss or the bit error rate before forward error correction reaches the corresponding threshold, it is determined to be a service degradation state; when the current service is not abnormal but passes through a fiber optic segment affected by a fault, it is determined to be a risk state in the same segment.

[0107] It should be noted that the service interruption status corresponds to the complete interruption of the original service-bearing optical link, while the service degradation status and the same-segment risk status correspond to the degraded transmission status; the same-segment risk status is used to pre-calculate available recovery paths before the fault loss continues to increase.

[0108] Furthermore, the current loss of the normal fiber segment, the fiber segment affected by the fault, the type of fault event, the location of the fault event, the scope of fault isolation, and the affected services are correlated to form a link fault diagnosis record.

[0109] Specifically, the current equivalent passive loss, new loss, and segment status of each fiber segment are associated with the fiber segment affected by the fault, the location of the fault event, the type of the fault event, the physical optical cable segment associated with the fault, the common risk group associated with the fault, the fault isolation range, the identifier of the affected service, the status of the service affected, and the status of the original service-bearing optical link.

[0110] The current loss of the normal fiber segment is the current equivalent passive loss of the normal fiber segment, which is used to reserve the actual loss of the normal segment when a fault occurs. The link fault diagnosis record also includes the fault diagnosis number, fault trigger time, current end-to-end net loss, and end-to-end net loss increase.

[0111] S3. Based on the link fault diagnosis record and backup optical path resources, search and test candidate recovery paths, retain the current loss of normal optical fiber segments, replace the loss of optical fiber segments affected by the fault with the measured loss of candidate recovery paths, calculate the expected link loss and the recovery available loss margin after recovery, and form a service recovery execution list. Furthermore, the affected fiber optic segments, fault isolation range, fault-related physical optical cable segments, fault-related common risk groups, and affected services are obtained from the link fault diagnosis records. The current occupancy status of backup fiber cores, backup wavelengths, and optical cross-connect ports is obtained based on the backup optical path resource identifier.

[0112] Specifically, it simultaneously acquires the current equivalent passive loss of normal fiber segments, the status of services affected, the status of the original service-carrying optical links, and the service wavelength, transmission rate, modulation method, forward error correction configuration, and allowed end-to-end net loss of each affected service, and re-reads the real-time status of spare fiber cores, spare wavelengths, spare ports, wavelength conversion nodes, and optical amplification nodes.

[0113] It should be noted that the backup optical path resources are used to limit the search range, and the real-time status is used to determine whether they can actually be used when a failure occurs, so as to avoid using resources that have been occupied by other services or locked by other recovery tasks.

[0114] Furthermore, a recovery path search topology is constructed based on the fiber optic routing topology and the current occupancy status, and fiber optic segments within the fault isolation range, within the fault-related physical fiber optic cable segment, within the fault-related common risk group, and those with unavailable resources are removed from the recovery path search topology.

[0115] Specifically, optical line terminals, optical distribution frames, optical cross-connect nodes, optical splitting nodes, and optical amplification nodes are used as path nodes, and available fiber optic segments are used as path edges. Physical optical cable segment identifiers, common risk group identifiers, spare fiber core status, spare wavelength status, transmission direction, and segment length are associated with the path edges.

[0116] It should be noted that deleting the path edges corresponding to the fault-associated physical optical cable segment and the common risk group is to prevent candidate recovery paths from sharing the same optical cable sheath, duct, pole line, or equipment room risk node with the fault-affected optical fiber segment.

[0117] Furthermore, using the optical cross-connect nodes at both ends of the fiber optic segment affected by the fault as the bypass start and bypass end points, a segment-level bypass path is searched.

[0118] Among them, the optical cross-connection nodes at both ends of the fiber optic segment affected by the fault refer to the nodes that are closest to the fault isolation range on the upstream and downstream sides of the original service-bearing optical link of the affected service and are capable of performing optical cross-connection.

[0119] Specifically, when the boundary of the fiber segment affected by the fault is a node capable of performing optical cross-connection and is located outside the fault isolation range, the corresponding segment boundary is determined as the bypass start point or bypass end point; when the segment boundary is an optical distribution frame port, connector, optical splitter node, optical amplifier node, or locatable fiber splice point, or when the corresponding segment boundary is located within the fault isolation range, the process traces back upstream or downstream along the original service-bearing optical link to the nearest node capable of performing optical cross-connection, and the two nodes determined by the backtracking are respectively taken as the bypass start point and bypass end point, and the fiber segment on the original service-bearing optical link between the bypass start point and bypass end point is determined as the replaced fiber segment. In the recovery path search topology, a loop-free path connecting the bypass start point and bypass end point without passing through the deleted path edge is searched; when there is no node capable of performing optical cross-connection on either side, no corresponding segment-level bypass path is generated, and the process switches to end-to-end recovery path search.

[0120] Furthermore, using the sending and receiving ports of the affected services as the recovery start and end points, an end-to-end recovery path is searched, and the segment-level bypass path and the end-to-end recovery path are combined into a candidate recovery path set.

[0121] Specifically, the path search adopts the constraint shortest path or multi-path search method supported by the optical transport network controller, and uses wavelength continuity, wavelength conversion capability, optical cross-connect capability and transmission direction as constraints; for the same affected service, 3 to 10 candidate recovery paths without loops are reserved.

[0122] It should be noted that when a segment-level bypass path can bypass the fault isolation range, both the segment-level bypass path and the end-to-end recovery path are retained; when neither exists, the corresponding affected service is written into the "Pending Manual Recovery" item. Each path in the candidate recovery path set records the candidate recovery path number, path type, recovery start point, recovery end point, fiber optic segment traversed, spare fiber core, spare wavelength, optical cross-connect node, optical amplification node, physical optical cable segment, and common risk group.

[0123] Furthermore, based on the candidate recovery path set, temporary test connections are established at the optical cross-connect nodes, and bidirectional loss tests are performed on the passive test segments in the candidate recovery paths.

[0124] Specifically, before establishing a temporary test connection, the optical transmission control terminal rereads the current occupancy and locking status of the spare fiber cores, spare wavelengths, optical cross-connect ports, and wavelength conversion ports used by the candidate recovery path. Temporary test connections are only established for resources that do not carry on-network services, are not pre-occupied by protection services, and are not locked. When a candidate recovery path needs to pass through optical cross-connect nodes or optical devices shared with on-network services, the test light is accessed through a test port or monitoring channel isolated from the service transmission channel, without changing the effective optical cross-connect relationship corresponding to the on-network service. If isolation testing conditions are not available, the corresponding candidate recovery path is marked as temporarily suspended for testing, and the test is performed within the maintenance time window. After the temporary test connection is established, the connection status returned by each optical cross-connect node is verified. If the connection status matches the temporary test configuration, bidirectional loss testing begins. After the test is completed, the temporary test configuration is revoked, and the connection status of each node is reread and compared with the connection status saved before the test. If the connection status matches, the temporary test connection is determined to be released; if the connection status does not match, subsequent test processing is stopped, and a connection status pending recovery record is generated.

[0125] The test uses the same test wavelength, pulse width, sampling interval and number of repetitions as in step one. Each direction is tested 3 to 5 times and the median value of the segment loss is taken. If the difference between multiple tests of the same passive test segment exceeds the allowable deviation of unidirectional test repeatability, the test is repeated. If it still does not meet the requirements, the candidate recovery path is marked as invalid.

[0126] It should be noted that the optical time-domain reflectometry test light cannot directly pass through the optical amplification node with isolation function to complete the bidirectional test of the entire path. Therefore, the loss of each passive test segment and the actual gain of the optical amplification node are recorded separately.

[0127] Furthermore, based on the bidirectional loss test results and the loss calibration relationship between the test wavelength and the service wavelength, the measured loss of the candidate recovery path under the service wavelength is obtained, and the insertion loss of the newly added optical cross-connect and the actual gain of the optical amplification node are obtained.

[0128] Specifically, the bidirectional test results of each passive test segment included in the candidate recovery path replacement section are converted into the measured equivalent passive loss at the service wavelength according to the loss calibration relationship between the test wavelength and the service wavelength. The converted measured equivalent passive losses are then summarized to obtain the measured loss of the candidate recovery path. The measured loss of the candidate recovery path is the measured equivalent passive loss of the candidate recovery path replacement section at the service wavelength. The path portion of the candidate recovery path that overlaps with the retained normal fiber segment is not included in the measured loss of the candidate recovery path. At the same time, the insertion loss of the optical cross-connection added outside the temporary test reference plane when establishing the recovery optical path, as well as the current actual gain of each optical amplification node in the candidate recovery path, are read.

[0129] It should be noted that no wavelength conversion is performed when the test wavelength matches the service wavelength; if the wavelength loss calibration relationship for the corresponding fiber type or passive device is missing, the candidate recovery path will be marked as a loss-to-calibration state and will not be included in the automatic recovery range. Device losses already included in the measured loss of the candidate recovery path will not be included in the insertion loss of the new optical cross-connection.

[0130] Furthermore, based on the recovery start and end points of the candidate recovery paths, the fiber segments to be replaced and the normal fiber segments to be retained are determined from the ordered fiber segment sequence of the affected services.

[0131] Specifically, for segment-level bypass paths, the original fiber segment between the bypass start point and the bypass end point is identified as the replaced fiber segment, and the normal fiber segment that continues to be used before the bypass start point and after the bypass end point is identified as the retained normal fiber segment; for end-to-end recovery paths, the original fiber segment that is no longer used is identified as the replaced fiber segment, and only the normal fiber segment that is shared with the original service-carrying optical link and continues to be used is identified as the retained normal fiber segment.

[0132] Furthermore, the current loss of the preserved normal fiber segment is obtained from the link fault diagnosis record, and a loss replacement relationship is established between the current loss of the preserved normal fiber segment, the measured loss of the candidate recovery path, and the replaced fiber segment.

[0133] Specifically, for each affected service and each candidate recovery path, a service candidate combination is established. The current equivalent passive loss of each normal fiber segment at the time of the fault is retained, the loss of the replaced fiber segment is deleted, and the loss of the replaced fiber segment is replaced with the measured loss of the candidate recovery path.

[0134] It should be noted that the current equivalent passive loss measured in step two is used to retain the normal fiber segment, instead of the reference loss, so that the recovery loss calculation retains the temperature changes, connector changes, and long-term attenuation changes that already existed in the normal segment when the fault occurred; when the candidate recovery path overlaps with the retained normal fiber segment, only the retained normal fiber segment is included to avoid duplicate accumulation.

[0135] It should also be noted that the test reference plane of the candidate recovery path replacement section should correspond to the start and end points of the replaced fiber segment; when the reference planes cannot be completely overlapped, the loss of passive devices added between the reference planes should be included in the insertion loss of the new optical cross-connection.

[0136] Furthermore, the current loss of the retained normal fiber segment and the measured loss of the candidate recovery path are summarized, the insertion loss of the newly added optical cross-connect is added and the actual gain of the optical amplification node is deducted to obtain the expected link loss after recovery.

[0137] Specifically, the expected link loss after recovery is expressed as: ; in, Indicates the first The estimated link loss after recovery for each service candidate combination is expressed in decibels. The estimated link loss after recovery is the end-to-end net loss including the gain of the optical amplification node. Indicates the first The set of reserved normal fiber segment numbers corresponding to each service candidate combination; This indicates the first step determined in step two. The current equivalent passive loss of a normal fiber segment, in decibels; Indicates the first The measured equivalent passive loss of the candidate recovery path replacement part in each service candidate combination at the service wavelength is expressed in decibels. Indicates the first The optical cross-connection insertion loss added when establishing the recovery optical path for each service candidate combination, which is not included in the measured equivalent passive loss of the candidate recovery path, is expressed in decibels. Indicates the first Each service candidate combination corresponds to the sum of the current actual gains of each optical amplification node in the recovery optical path, in decibels; This indicates the candidate recovery path number.

[0138] It should be noted that the current equivalent passive loss of the retained normal fiber segment, the measured loss of the candidate recovery path replacement part, and the insertion loss of the newly added optical cross-connection are all loss quantities, which are added together in the formula; the actual gain of the optical amplification node is a gain quantity, which is subtracted in the formula, and all items are expressed in decibels.

[0139] It should also be noted that when there is no optical amplification node, the test reference plane already includes all newly added optical cross-connect devices, or the end-to-end recovery path does not retain the original normal fiber segment, the sum of the corresponding gain, insertion loss, or segment loss is taken as 0; when the optical amplification node alarms, gain data is missing, or exceeds the allowable operating range, the corresponding service candidate combination is not calculated.

[0140] Furthermore, based on the difference between the net end-to-end loss allowed for the affected services and the expected link loss after recovery, the available loss margin for recovery is obtained.

[0141] Specifically, the recoverable loss margin is determined according to the following formula: ; in, Indicates the first Recovery available loss margin for each business candidate combination, in decibels. Indicates the first The affected business is allowed a net end-to-end loss, in decibels. Indicates the first Expected link loss after recovery for each service candidate combination.

[0142] It should be noted that the recovery loss safety margin threshold is predetermined based on the aging margin of the optical transceiver module, changes in ambient temperature, fluctuations in the insertion loss of optical cross-connect devices, and the service level, and is usually taken as 1 dB to 6 dB; the recovery loss safety margin threshold is not reduced in reverse based on the test results of the current candidate recovery path.

[0143] Furthermore, candidate recovery paths are selected that have a recovery loss margin not lower than the recovery loss safety margin threshold, and whose service wavelength, transmission rate, modulation scheme, forward error correction configuration, and recovery resource status meet the service transmission requirements, thereby obtaining service available candidate paths.

[0144] Specifically, in candidate recovery paths without wavelength conversion capability, it is verified that the service wavelength is continuously available in all fiber segments; in candidate recovery paths with wavelength conversion capability, it is verified that the wavelength conversion node supports the service transmission rate and modulation method; at the same time, it is verified that the optical transceiver port, optical cross-connect port and optical amplification node support the service wavelength, transmission rate, modulation method and transmission direction.

[0145] Furthermore, the expected received optical power is determined based on the current transmitted optical power and the expected link loss after recovery, and it is verified that the expected received optical power is not lower than the receiving sensitivity and not higher than the maximum allowable received optical power.

[0146] When the loss condition, optical power condition, wavelength condition, port condition, modulation method condition, forward error correction configuration condition, resource availability condition, and test validity condition are all met, the candidate recovery path is determined as the service available candidate path.

[0147] It should be noted that bidirectional services verify both transmission directions separately. Only when there are available candidate paths for services in both directions and no conflict in the recovery resources will the service enter the automatic recovery range.

[0148] Furthermore, the available candidate paths for the service are ranked according to the degree of fault risk isolation, the margin of recovery available loss, the number of fiber segments that need to be changed, and the number of optical cross-connect nodes that need to be operated.

[0149] Specifically, a fault risk isolation level field is set for each candidate recovery path, and the field value is determined based on the fiber optic segments, physical cable segments, and common risk groups traversed by the candidate recovery path. When a candidate recovery path enters the fault isolation range, or passes through a fault-related physical cable segment or a fault-related common risk group, the fault risk isolation level field is set to "risk not isolated," and the corresponding candidate recovery path is determined as an unavailable candidate path and does not participate in the ranking of service-available candidate paths. When a candidate recovery path does not enter the fault isolation range and does not pass through a fault-related physical cable segment or a fault-related common risk group, the fault risk isolation level field is set to "risk isolated," and the corresponding candidate recovery path is retained as a service-available candidate path. For service-available candidate paths where both the fault risk isolation level field indicates "risk isolated," they are ranked from largest to smallest recovery availability loss margin. If the recovery availability loss margin is the same, they are ranked from smallest to largest based on the number of fiber optic segments that need to be changed. If they are still the same, they are ranked from smallest to largest based on the number of optical cross-connection nodes that need to be operated, the physical length of the path from shortest to longest, and the candidate recovery path number from smallest to largest.

[0150] The judgment rules for the fault risk isolation degree field and the sorting rules for available candidate paths are determined based on the operator's service recovery strategy and network operation and maintenance configuration, and are pre-written into the recovery path sorting strategy table of the optical transport network controller. The fault risk isolation degree field is used to re-verify the path search results to prevent candidate recovery paths that pass through fault-related risk resources from entering the set of available candidate paths due to fiber optic routing topology, common risk group records, or resource status updates.

[0151] It should be noted that the candidate recovery paths are arranged by comparison item by item, without simply weighting and summing the risk isolation level, recovery available loss margin and number of operations, so as to avoid the instability of the arrangement results due to the weight changes of data with different dimensions.

[0152] Furthermore, the affected services, available candidate paths, expected link loss after recovery, remaining loss margin after recovery, resources to be locked, and recovery execution order are associated to form a service recovery execution list.

[0153] Specifically, affected services are arranged according to service interruption status, service degradation status, and risk status within the same segment. When the statuses are the same, they are arranged from highest to lowest service level and from earliest to latest fault trigger time. When multiple services compete for the same spare fiber core, spare wavelength, or exclusive optical cross-connect port, the corresponding available candidate path is reserved for the service that ranks first, and the corresponding resource is recorded as the priority resource and the service that ranks first is the priority service. Then, the next available candidate path without resource conflict is selected for the services that rank last.

[0154] Simultaneously, multiple available candidate paths for the same service are written into the service recovery execution list in order of priority. When a service ranked lower in the list has no available candidate path without conflict due to resource contention, a resource contention pending recovery record is generated, recording the affected service identifier, conflicting resource identifier, conflicting resource type, priority occupying service identifier, resource contention occurrence time, and reason for no automatic recovery path. If the recovery resource corresponding to the priority occupying service is a temporarily locked resource that can be released after recovery failure, the service ranked lower in the list is written into the recovery waiting queue, and the candidate recovery path selection is re-executed after the corresponding resource is released. If the conflicting resource has been converted to the service occupation status of the priority occupying service, or if there is no expected releaseable resource within the allowed service recovery time, the service ranked lower in the list is written into the pending manual recovery item.

[0155] The service recovery execution list includes resource contention status, conflicting resource identifier, conflicting resource type, priority occupied service identifier, waiting queue status, fault diagnosis number, affected service identifier, affected service status, original service carrying optical link status, candidate recovery path number and type, candidate bypass fiber segment, retained normal fiber segment, expected link loss after recovery, recovery available loss margin, service wavelength, optical cross-connection operation node, wavelength conversion node, list of resources to be locked, candidate recovery path arrangement order, and service recovery execution order.

[0156] S4. Based on the service recovery execution list, lock the recovery resources, switch the affected services using segment-level bypass or end-to-end recovery methods, and determine the service fault recovery result based on the received optical power, measured link loss, bit error status, and service continuity status.

[0157] Furthermore, according to the recovery execution order in the business recovery execution list, the candidate recovery paths and resources to be locked corresponding to the affected business are read, the current status of the spare fiber core, spare wavelength, optical cross-connect port, wavelength conversion port and optical amplification node are re-verified, and atomic locking is performed on the recovery resources that have passed the verification.

[0158] Specifically, when the spare fiber core is not carrying other services, the spare wavelength is idle in all fiber segments traversed by the candidate recovery path, the optical cross-connect port and wavelength conversion port are not occupied, and the optical amplification node is not in a faulty or abnormal gain state, a recovery transaction number is generated and all resources in the list of resources to be locked are locked at the same time.

[0159] Atomic locking refers to the process of establishing a recovery optical path only after all resources to be locked have been successfully locked; if any resource lock fails, the partially completed lock is revoked and the next candidate recovery path is read.

[0160] It should be noted that the allowed duration of resource locking is determined based on the controller command response time, the number of control nodes, and the allowed service recovery time, and is usually between 1 second and 30 seconds; when the recovery is successful, the locked state is converted to the service occupied state, and the lock is released when the recovery fails.

[0161] Furthermore, when the candidate recovery path is a segment-level bypass path, the normal fiber segments outside the fault-affected fiber segments remain unchanged, and a bypass optical path is established between the optical cross-connect nodes at both ends of the fault-affected fiber segment; when the candidate recovery path is an end-to-end recovery path, an end-to-end recovery optical path that avoids the fault-affected fiber segments is established between the service transmission port and the service reception port.

[0162] Specifically, segment-level bypass recovery establishes optical cross-connections based on candidate bypass fiber segments, bypass start points, and bypass end points, replacing only the original fiber segments corresponding to the fault isolation range; end-to-end recovery establishes optical cross-connections sequentially from the service sending port to the service receiving port according to the order of each fiber segment in the candidate recovery path, and configures wavelength conversion nodes and optical amplification nodes according to the service recovery execution list.

[0163] Meanwhile, before switching services, the configuration execution status returned by each optical cross-connect node, wavelength conversion node, and optical amplification node is obtained; when all configurations are completed and the device status is normal, the recovery optical path is determined to be established; if any configuration fails, the current recovery configuration is revoked, the recovery resources are released, and the next candidate recovery path is read.

[0164] It should be noted that the optical cross-connect configuration, wavelength conversion configuration, and optical channel establishment adopt mature control methods supported by the optical transport network controller; the equipment supports sending test signals or continuous test frames without carrying user services to confirm the optical path connectivity before service switching when the optical channel is tested.

[0165] Furthermore, depending on the degraded transmission status or complete interruption status of the original service-bearing optical link, the affected services will be switched from the original service-bearing optical link to the established segment-level bypass optical link or end-to-end recovery optical link.

[0166] Specifically, when the original service-bearing optical link is in a degraded transmission state, the process is executed in the order of first establishing a recovery optical path, then switching services, and finally processing the original optical path. The original optical path resources that can maintain service transmission are reserved before the recovery verification is completed. When the original service-bearing optical link is in a completely interrupted state, the fiber segment affected by the fault is kept isolated, and the service is directly connected to the recovery optical path.

[0167] It should be noted that in degraded transmission mode, lossless protection switching or optical layer bridging switching supported by the equipment is preferred; in complete interruption mode, invalid back-switching to the faulty original optical path is not performed.

[0168] Furthermore, within the recovery verification time window, the transmitted optical power, received optical power, bit error rate before forward error correction, optical signal loss status, and service operation management and maintenance continuity status are collected after recovery, and the measured link loss after recovery is determined based on the transmitted optical power and received optical power.

[0169] Specifically, recovery status is collected according to the recovery verification time window and recovery verification sampling period in the segment link loss baseline record. The median value of the transmitted optical power and received optical power after recovery is taken for no less than 5 sets. The measured link loss after recovery is expressed as: ; in, Indicates the first The measured link loss after recovery for each service candidate combination is expressed in decibels. The measured link loss after recovery is the end-to-end net loss including the actual gain of the optical amplification node. This represents the median transmitted optical power after recovery, in decibels and milliwatts. This represents the median received optical power after recovery, in decibels and milliwatts. Indicates the business sequence number. This indicates the candidate recovery path number.

[0170] It should be noted that the recovery verification time window and sampling period are determined based on the service transmission rate, forward error correction statistics period, service continuity detection period, and equipment interface refresh period. The recovery verification time window is usually 1 to 30 seconds, and the sampling period is usually 100 milliseconds to 1 second. The number of recovery verification sampling groups is determined based on the recovery verification time window, sampling period, and refresh period of the optical power monitoring equipment interface, and is written into the recovery verification parameter table. It is usually configured as 5 to 30 groups. When less than 5 groups of valid sampling data are obtained within the recovery verification time window, the median value of the transmitted optical power and the median value of the received optical power after recovery are not calculated, and the current recovery verification result is marked as insufficient verification data.

[0171] Furthermore, the received optical power after recovery, the measured link loss after recovery, the deviation between the measured link loss after recovery and the expected link loss after recovery, the bit error rate before forward error correction, and the continuity status of service operation management and maintenance are compared with the corresponding allowable conditions to determine the recovery verification result of the current candidate recovery path.

[0172] Specifically, the loss deviation between the measured link loss after recovery and the predicted link loss after recovery is expressed as: ; in, Indicates the first Loss deviation of each business candidate combination, in decibels. This indicates the measured link loss after recovery. This indicates the expected link loss after recovery, as determined in step three.

[0173] It should be noted that the expected loss deviation threshold after recovery is determined based on the optical power monitoring error, the candidate recovery path test error, the insertion loss error of the optical cross-connect device, and the gain fluctuation of the optical amplification node, and is usually taken as 0.5 dB to 2.0 dB. The fact that the measured link loss after recovery exceeds the expected link loss after recovery does not directly indicate that the recovery has failed. It is only determined that the loss condition is not met when the loss deviation exceeds the threshold or the measured link loss after recovery exceeds the end-to-end net loss allowed by the service.

[0174] Furthermore, the received optical power after recovery is compared with the receiving sensitivity and the maximum allowable received optical power. If the same over-limit state occurs for no less than two consecutive sampling periods, the received optical power is determined to be abnormal. The bit error rate before forward error correction is compared with the allowable upper limit and combined with the uncorrectable codeword alarm to determine the bit error state. The service operation management and maintenance continuity state is determined based on optical signal loss, path mismatch, connection error, continuity loss alarm and continuity detection message reception.

[0175] The number of consecutive sampling cycles required to confirm abnormal received optical power is determined based on service continuity requirements, the refresh cycle of the optical power monitoring equipment interface, and the false alarm suppression strategy, and is written into the recovery verification parameter table. It is usually configured as 2 to 5 sampling cycles. In this embodiment, 2 consecutive sampling cycles are used. When the received optical power is lower than the receiving sensitivity or higher than the maximum allowable received optical power for 2 consecutive sampling cycles, the received optical power is determined to be abnormal. If the number of consecutive sampling cycles has not been reached, sampling continues, and no abnormal received optical power judgment is generated.

[0176] It should be noted that services without forward error correction use the maximum allowable bit error rate of the corresponding service interface; the continuity detection of service operation management and maintenance uses optical transport network path monitoring, Ethernet continuity detection, or the detection mechanism of the corresponding service protocol.

[0177] Furthermore, when the recovery verification result meets all the allowed conditions, the corresponding affected service is determined to have been successfully recovered, and the locked recovery resources are converted to a service-occupied state; when the recovery verification result does not meet all the allowed conditions, the recovery resources occupied by the current candidate recovery path are released, and the next candidate recovery path is selected according to the service recovery execution list to form a service fault recovery result.

[0178] Among them, when the received optical power is normal after recovery, the measured link loss after recovery does not exceed the service's allowed end-to-end net loss, the loss deviation does not exceed the expected loss deviation threshold after recovery, the bit error status is normal, the service operation, management and maintenance continuity status is normal and no optical signal loss occurs, the current candidate recovery path is determined as a successful recovery.

[0179] In addition, if the recovery verification fails but the original service-bearing optical link can still maintain service, the service will be switched back to the original service-bearing optical link; if the original service-bearing optical link is completely interrupted, the affected fiber segment will remain isolated; in both cases, the current recovery configuration will be revoked, recovery resources will be released, and the next candidate recovery path will be read. If all available candidate paths for the service fail the recovery verification, the corresponding service will be marked as automatically recovered and added to the list of services awaiting manual recovery.

[0180] Furthermore, after a successful recovery, the segment-level bypass recovery retains the normal fiber optic segments before the bypass start point and after the bypass end point, as well as the candidate bypass fiber optic segments, and the end-to-end recovery retains the actual recovery path; only the original optical path resources that are currently exclusively occupied by the service and are no longer in use are released, while shared resources continue to be retained.

[0181] Specifically, for affected services that have entered the recovery resource locking, recovery optical path establishment and recovery verification processes, the affected services, actual recovery paths, recovery methods, recovery resources, net loss from the front end to the end of the recovery, expected link loss after recovery, measured link loss after recovery, loss deviation, received optical power after recovery, bit error status, service operation management and maintenance continuity status, recovery time, recovery result and reason for recovery failure are associated to form a service fault recovery result record.

[0182] Furthermore, the optical transmission control terminal summarizes the abnormal processing states generated during the service fault recovery process, and associates the corresponding service identifier, fiber segment number, candidate recovery path number, processing stage, state type, state occurrence time, state cause, associated record number, and subsequent handling method to form a service fault processing state record. Among them, the state types include route verification pending state, bidirectional test incomplete state, baseline verification pending state, insufficient monitoring data state, transmitting port verification pending state, loss test unreachable state, loss calibration pending state, resource contention pending recovery state, and manual recovery pending state. The subsequent handling methods include re-verification, re-testing, supplementary calibration, entering the recovery waiting queue, and transferring to manual recovery.

[0183] Furthermore, the service fault recovery result record and service fault processing status record are sent to the optical transmission network management system and the fault maintenance work order system. For the same service that has already generated a service fault recovery result record, the corresponding service fault processing status record is associated with the service fault recovery result record through the recovery transaction number and the fault diagnosis number. For services that have not entered the recovery execution stage, the service fault processing status record is retained and the processing status is updated according to the subsequent handling method.

[0184] It should be noted that the service fault recovery result record is a temporary recovery record formed during the fault period using a segment-level bypass path or an end-to-end recovery path, and is not used to update the original segment link loss baseline record, link fault diagnosis record, or service recovery execution list; the fiber optic segment affected by the fault shall remain isolated until the on-site repair is completed.

[0185] After on-site repairs are completed, bidirectional loss tests are re-executed on the repaired fiber optic segments and the original service-bearing optical links to be relocated, following the link acceptance process. The forward segment loss, reverse segment loss, and segment baseline equivalent passive loss of each fiber optic segment are re-determined, and loss closure verification is performed. If the link acceptance or loss closure verification fails, the current recovery path is maintained, service relocation is not performed, and the reason for failure is written into the record pending manual review. If the link acceptance and loss closure verification pass, a new segment link loss baseline version is generated based on the retest results and marked as pending activation. The original baseline version number, new baseline version number, repaired fiber optic segment, retest results, acceptance results, and corresponding service fault recovery result record numbers are associated to form a baseline reconstruction record after on-site repairs.

[0186] After writing the new segment link loss baseline version, the affected services will be migrated back from the current recovery path to the original service-bearing optical link. Migration verification will be performed based on the received optical power, measured link loss, bit error rate, and service operation management and maintenance continuity status after migration. If the migration verification is successful, the new segment link loss baseline version will be updated to the effective state, the original segment link loss baseline version will be updated to the historical state, and unused recovery resources will be released. If the migration verification fails, the services will be switched back to the current recovery path, the new segment link loss baseline version will be maintained in the pending effective state, and the reason for the migration failure will be written into the baseline reconstruction record after on-site repair.

[0187] In summary, this invention achieves a more refined link loss benchmark by dividing the service-carrying optical link into multiple fiber segments, performing bidirectional loss tests on each fiber segment, and establishing a correspondence between services and ordered fiber segment sequences. This refines the link loss benchmark from end-to-end overall recording to segment-level recording, improving the correlation accuracy between fault loss changes and specific fiber segments and carried services. By retaining the current loss of normal fiber segments at the time of the fault, replacing the loss of fault-affected fiber segments with the measured loss of candidate recovery paths, and combining the insertion loss of newly added nodes and the actual gain of optical amplification nodes to calculate the expected link loss after recovery, this invention reconstructs the recovery link loss based on the current link state and the measured path state, improving the matching degree between recovery path loss assessment and actual operating status.

[0188] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A service fault recovery method based on fiber optic link loss testing, characterized in that, include: Obtain the fiber optic routing topology, service parameters, and backup optical path resources; divide the service-bearing optical links into fiber optic segments and perform bidirectional loss tests; establish the correspondence between services and fiber optic segments; and obtain the segment link loss baseline records. Perform fault loss tests based on optical power and service status, register the reflection curve with the segment link loss benchmark record, determine the fiber segment affected by the fault and the affected services, and form a link fault diagnosis record. Based on the link fault diagnosis records and backup optical path resources, candidate recovery paths are searched and tested. The current loss of the normal fiber segment is retained, and the loss of the fiber segment affected by the fault is replaced with the measured loss of the candidate recovery path. The expected link loss and the available loss margin after recovery are calculated to form a service recovery execution list. Based on the service recovery execution list, the recovery resources are locked, and the affected services are switched using segment-level bypass or end-to-end recovery methods. The service fault recovery result is determined based on the received optical power, measured link loss, bit error rate, and service continuity status.

2. The service fault recovery method based on fiber optic link loss testing as described in claim 1, characterized in that, The process of obtaining the fiber optic routing topology, service parameters, and backup optical path resources, and dividing the service-bearing optical link into fiber optic segments includes: The optical transmission network management system, optical fiber resource management system, and optical transport network controller acquire optical fiber connection relationships, optical cross-connect relationships, service transmission parameters, spare fiber core information, and spare wavelength information. Using optical distribution frame ports, connectors, optical splitting nodes, optical cross-connect nodes, optical amplification nodes, and locatable fiber splice points as segment boundaries, the service-carrying optical link is divided into multiple fiber segments. When the distance between the boundaries of two adjacent segments is less than the attenuation dead zone length of the bidirectional loss test equipment, the optical fiber transmission portion between the boundaries of the two adjacent segments is merged into a composite optical fiber segment. Each fiber segment is associated with its corresponding physical fiber segment and common risk group, and the fiber segment start point, fiber segment end point, segment length, and segment transmission direction are recorded.

3. The service fault recovery method based on fiber optic link loss testing as described in claim 2, characterized in that, The establishment of the correspondence between services and fiber optic segments includes: Based on the service transmission port, service reception port, service wavelength, and optical cross-connection relationship, trace the service bearer optical link along the service signal transmission direction; The fiber segment numbers are arranged according to the order in which the service signals pass through the fiber segments, forming an ordered sequence of fiber segments corresponding to the service identifier. For services with bidirectional transmission, establish the correspondence between forward services and forward ordered fiber segment sequences, and the correspondence between reverse services and reverse ordered fiber segment sequences. When the cross-connection relationship of a service is inconsistent with the physical route in the fiber optic routing topology, the corresponding service will be marked as a route pending verification state, and the generation of the corresponding service's segment link loss baseline record will be stopped.

4. The service fault recovery method based on fiber optic link loss testing as described in claim 2 or 3, characterized in that, The acquisition of the segment link loss baseline record includes: Optical temporal reflectance tests were performed in both directions of the service-bearing optical link to obtain the forward and reverse reflectance curves. Using fixed reflection events in the fiber optic routing topology as location references, the same physical event in the forward and reverse reflection curves is registered to determine the forward and reverse segment losses of each fiber optic segment. The bidirectional reference loss of each fiber segment is determined based on the forward segment loss and the reverse segment loss, and the equivalent passive loss of the segment reference is determined based on the loss calibration relationship between the test wavelength and the service wavelength. By combining the segment benchmark equivalent passive loss, service end-to-end net loss, node insertion loss, and actual gain of optical amplification nodes for each fiber segment, loss closure verification is performed. The verified loss test results are then associated with service identifiers, ordered fiber segment sequences, physical optical cable segments, and common risk groups to obtain segment link loss benchmark records.

5. The service fault recovery method based on fiber optic link loss testing as described in claim 1, characterized in that, The process of performing fault loss testing based on optical power and service status, and registering the reflection curve with the segment link loss benchmark record, includes: Collect data on the transmitted optical power, received optical power, optical signal loss status, bit error rate before forward error correction, and the continuity status of service operation, management, and maintenance of the optical link carrying the service. The current end-to-end net loss is determined based on the transmitted optical power and received optical power, and then compared with the end-to-end reference net loss in the segment link loss reference record to obtain the increase in end-to-end net loss. When the increase in end-to-end net loss, optical signal loss status, bit error rate before forward error correction, or continuity of service operation management and maintenance status reach the fault triggering conditions, a bidirectional fault loss test is performed on the service bearer optical link to obtain the current forward reflection curve and the current reverse reflection curve. Obtain fixed reflection events from the segment link loss baseline record, and use the fixed reflection events as registration anchor points to perform event pairing on the current forward reflection curve and the current reverse reflection curve; Based on the registration anchor points, the distance coordinates of the current forward and reverse reflection curves are corrected, and the segment registration is completed according to the fiber segment boundaries.

6. The service fault recovery method based on fiber optic link loss testing as described in claim 5, characterized in that, The process of determining the affected fiber optic segment and the affected services, and forming a link fault diagnosis record, includes: Based on the current forward and reverse reflection curves after segment registration is completed, the current loss of each fiber segment is determined, and the current loss is compared with the segment reference loss in the segment link loss reference record to obtain the new loss of each fiber segment. Based on the termination event of the reflection curve, the new reflection event, the loss change of the original reflection event, and the new loss in the section, determine the type of fault event and the fiber section affected by the fault. Based on the location of the fault event in the reflection curve, the physical optical cable segment corresponding to the fiber segment affected by the fault, and the common risk group, the location of the fault event and the scope of fault isolation are determined. Based on the correspondence between services and fiber segments, query the services that contain fault-affected fiber segments in the ordered fiber segment sequence to determine the affected services and their corresponding affected status. The current loss of the normal fiber segment, the fiber segment affected by the fault, the type of fault event, the location of the fault event, the scope of fault isolation, and the affected services are correlated to form a link fault diagnosis record.

7. The service fault recovery method based on fiber optic link loss testing as described in claim 1, characterized in that, The process of searching and testing candidate recovery paths based on link fault diagnosis records and backup optical path resources includes: The affected fiber optic segment, the scope of the fault isolation, the physical optical cable segment associated with the fault, the common risk group associated with the fault, and the affected services are obtained from the link fault diagnosis record. The current occupancy status of the spare fiber core, spare wavelength, and optical cross-connect port is obtained based on the spare optical path resource identifier. Construct a recovery path search topology based on the fiber optic routing topology and the current occupancy status, and remove fiber optic segments within the fault isolation range, within the fault-related physical fiber optic cable segment, within the fault-related common risk group, and from the recovery path search topology; Using the optical cross-connect nodes at both ends of the fiber optic segment affected by the fault as the bypass start and bypass end points, search for segment-level bypass paths; Using the sending and receiving ports of the affected services as the starting and ending points for recovery, an end-to-end recovery path is searched, and the segment-level bypass path and the end-to-end recovery path are combined into a candidate recovery path set.

8. The service fault recovery method based on fiber optic link loss testing as described in claim 7, characterized in that, The process of retaining the current loss of the normal fiber segment and replacing the loss of the fault-affected fiber segment with the measured loss of the candidate recovery path includes: Based on the candidate recovery path set, control the optical cross-connect nodes to establish temporary test connections, and perform bidirectional loss tests on the passive test segments in the candidate recovery paths; Based on the bidirectional loss test results and the loss calibration relationship between the test wavelength and the service wavelength, the measured loss of the candidate recovery path under the service wavelength is obtained, and the insertion loss of the newly added optical cross-connect and the actual gain of the optical amplification node are obtained. Based on the recovery start and end points of the candidate recovery paths, the fiber segments to be replaced and the normal fiber segments to be retained are determined from the ordered fiber segment sequence of the affected services. Obtain the current loss of the preserved normal fiber segment from the link fault diagnosis record, and establish the loss replacement relationship between the current loss of the preserved normal fiber segment, the measured loss of the candidate recovery path, and the replaced fiber segment.

9. The service fault recovery method based on fiber optic link loss testing as described in claim 1 or 8, characterized in that, The calculation of the estimated link loss and the recovery availability margin after recovery, forming the service recovery execution list, includes: The current loss of the retained normal fiber segment and the measured loss of the candidate recovery path are summarized, the insertion loss of the newly added optical cross-connect is added and the actual gain of the optical amplification node is subtracted to obtain the expected link loss after recovery. The available loss margin for recovery is obtained based on the difference between the net end-to-end loss allowed for the affected service and the expected link loss after recovery. Candidate recovery paths are selected based on the following criteria: the available recovery loss margin is not less than the safe recovery loss margin threshold, and the service wavelength, transmission rate, modulation method, forward error correction configuration, and recovery resource status meet the service transmission requirements. Available service candidate paths are then obtained. The available candidate paths for the service are ranked according to the degree of fault risk isolation, the margin of recovery available loss, the number of fiber segments that need to be changed, and the number of optical cross-connect nodes that need to be operated. The affected services, available candidate paths, expected link loss after recovery, remaining loss margin after recovery, resources to be locked, and recovery execution order are associated to form a service recovery execution list.

10. The service fault recovery method based on fiber optic link loss testing as described in claim 9, characterized in that, The process of locking recovery resources according to the service recovery execution list, switching affected services using segment-level bypass or end-to-end recovery methods, and determining the service fault recovery result based on received optical power, measured link loss, bit error rate, and service continuity status includes: Read the candidate recovery paths and locked resources corresponding to the affected services according to the recovery execution order in the business recovery execution list, re-verify the current status of the spare fiber core, spare wavelength, optical cross-connect port, wavelength conversion port and optical amplification node, and perform atomic locking on the recovery resources that have passed the verification. When the candidate recovery path is a segment-level bypass path, the normal fiber segment outside the fault-affected fiber segment remains unchanged, and a bypass optical path is established between the optical cross-connect nodes at both ends of the fault-affected fiber segment; when the candidate recovery path is an end-to-end recovery path, an end-to-end recovery optical path that avoids the fault-affected fiber segment is established between the service transmission port and the service reception port. Depending on the degraded transmission status or complete interruption status of the original service-bearing optical link, the affected services will be switched from the original service-bearing optical link to the established segment-level bypass optical link or end-to-end recovery optical link. Within the recovery verification time window, collect the transmitted optical power, received optical power, bit error rate before forward error correction, optical signal loss status, and service operation management and maintenance continuity status after recovery, and determine the measured link loss after recovery based on the transmitted optical power and received optical power. The recovery verification results of the current candidate recovery path are determined by comparing the received optical power after recovery, the measured link loss after recovery, the deviation between the measured link loss after recovery and the expected link loss after recovery, the bit error rate before forward error correction, and the continuity status of service operation management and maintenance with the corresponding allowable conditions. When the recovery verification result meets all the allowed conditions, the corresponding affected service is determined to be successfully recovered, and the locked recovery resources are converted to a service occupied state; when the recovery verification result does not meet all the allowed conditions, the recovery resources occupied by the current candidate recovery path are released, and the next candidate recovery path is selected according to the service recovery execution list to form the service fault recovery result.

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