WO2008128462A1

WO2008128462A1 - A fault detecting method, system and apparatus for optical distributed network

Info

Publication number: WO2008128462A1
Application number: PCT/CN2008/070721
Authority: WO
Inventors: Sulin Yang
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2007-04-18
Filing date: 2008-04-16
Publication date: 2008-10-30
Also published as: CN101291176B; CN101291176A

Abstract

A fault detecting method, system and apparatus for optical distributed network are provided, the method comprises: the losses of the uplink signal at OLT side and the downlink signal at ONU/ONT side are detected respectively; if the loss of the downlink signal is greater than that of the uplink signal, then it is determined that an optical fiber bend fault is occurred; if the loss of the downlink signal is equal to that of the uplink signal, then it is determined that a connector fault is occurred. The system comprises: the first signal detecting module (1) arranged at OLT side and the second signal detecting module (2) arranged at ONU/ONT side, for detecting the optical powers of the uplink signal and the downlink signal at both sides respectively; a loss computing module (3), for computing the losses of the uplink signal and the downlink signal; and a fault analysis module (4), for analyzing and determining the fault type and/or the fault location according to the losses of the uplink signal and the downlink signal. The invention can expediently detect the fault type and/or the fault location, and have no special requirement to the optical fiber layout, so it is adapt to carry out fault detection on-line and in real time.

Description

TECHNICAL FIELD The present invention relates to a fault detection method, system and device for a communication network, and more particularly to a method, system and device for detecting faults in a light distribution network . BACKGROUND OF THE INVENTION At present, in the field of access networks, digital subscriber lines (DSL) are fully developed, and optical access is also booming, especially for point-to-multipoint optical access technologies. The Optical Network (Passive Optical Network) is once again receiving attention. Compared with point-to-point optical access, the P0N central office can be divided into dozens or more optical fibers to connect users with one optical fiber, thus greatly reducing the cost of network construction. At present, representative P0N technologies are Gigabit Passive Optical Network (GPON) and Ethernet Passive Optical Network (EPON), among which GPON technology has higher line rate. , maintenance management functions and other features.

The P0N system structure is shown in Figure 1. It consists of three parts: Optical Line Termination (OLT), Optical Distribution Network (ODN), and Optical Network Unit (Optical Network Unit). ONU) / Optical Network Termination (ONT).

The 0LT provides a network side interface for the PON system, connecting one or more 0DNs. The ODN splits the data in the 0LT downlink to each 0NU, and simultaneously aggregates the uplink data of multiple 0NU/0NTs to the 0LT. The ONU provides a user-side interface for the PON system, and the upstream is connected to the 0DN. If 0NU provides user port functions directly, such as an Ethernet user port, it is called 0NT.

ODN is generally divided into four parts, a passive optical splitter (Splitter), a backbone fiber (Feed Fiber) A, a distributed fiber (Distribute Fiber) B and a split fiber (Drop Fiber) C, which are divided into The cloth fiber and the branch fiber can be collectively referred to as a branch fiber. In Figure 1, there is a 0DN structure diagram with 2-level splitting. For the 0DN with only one-stage splitting, there are only trunk fibers and split fibers.

The P0N system uses a wavelength of 1 310 legs for the uplink and a wavelength of 1490 nm for the downlink. The uplink and downlink lights can be transmitted in the same fiber as shown in Figure 1. The uplink and downlink can also be transmitted by using one fiber.

In the P0N system, from 0LT to 0NU is called downlink, and vice versa. The downlink data is sent to each 0NU in a broadcast manner, and the uplink data transmission of each 0NU is allocated by the 0LT transmission interval, and is transmitted to the 0LT in a time division multiplexing manner.

In the PON system, 0LT and 0NU/0NT are connected through 0DN. If the 0DN fails, it will inevitably affect the data transmission of the entire P0N system. The failure of 0DN is mainly caused by the connection and excessive bending. Connection failures include loose connectors and contamination of the fiber end face of the connector.

There have been such statistical results: 83% of the failures of the Fibre-to-Home (F iber To The Home) system occurred in the "first kilometer" near the user, and the fiber failure accounted for 37%. More than 70% of fiber failures are caused by connection failures, and 26% are caused by excessive attenuation caused by fiber bending. Therefore, with the large number of P0N networks deployed and running, in order to ensure the normal operation of the P0N network, it is necessary to correctly and quickly identify and locate fiber faults. In addition, because the P0N network is close to the user, the identification and location of the fiber fault must meet the low cost requirements. Fiber faults are characterized by increased or even complete loss of light path.

The Opt i ca l Time Doma in Ref l ec tometer (OTDR) is a measuring instrument for measuring the transmission characteristics of an optical fiber. 0TDR provides attenuation details along the length of the fiber, ie detecting, locating and measuring faults (also known as events) anywhere on the fiber optic cable link. The failure refers to a defect in the optical transmission link due to welding, connectors, adapters, jumpers, bends or breaks, etc., and variations in the optical transmission characteristics of such defects can be measured. In the optical fiber communication network, the transmission characteristic test and fault location of the optical fiber transmission link require 0TDR. The OTDR works like a radar scan. The 0TDR sends a test signal and then determines the type and location of the fault based on the strength and time of the signal reflected back from the fiber event point. As shown in Figure 2, 0TDR is normally set on the 0LT side.

The optical fiber link monitoring can automatically and continuously perform on-line remote monitoring of the optical fiber line. The optical fiber line of the P0N network can be regularly maintained, and the fault can be identified remotely to achieve a rapid response to the fault, which can be affected before the high-level network is affected. Implement the underlying fast protection switch.

However, in the point-to-multipoint topology of the P0N network, the test signals sent by the 0TDR on the 0LT side are superimposed on each branch, and the 0TDR cannot distinguish the branch fiber where the event point is located, and if it is resolved from the ONU side. The cost of fault location is too high, and when the line loss is too large, the test data cannot be transmitted to the 0LT side in real time. In addition, due to the price sensitivity of the P0N network, a low cost fiber network fault identification scheme is required.

Another solution has been proposed in the prior art by adding a mirror at the end of each branch fiber to reflect the test wavelength. In the process of wiring, the length of each branch fiber is different, so that the waveforms of the reflected light at the end of each branch fiber do not overlap. The branch fiber is monitored by monitoring the waveform of the reflected light at the end of each branch fiber.

The scheme must require that each branch fiber has a different length to determine the branch state based on the position of the reflected signal of each branch. This increases the difficulty of wiring, and can only judge the defects of fiber breakage or severe deterioration of performance, and cannot judge the defects caused by other causes (such as connection, bending, stress change, etc.).

The difficulty of the 0LT side test of the P0N network fiber is that the back-reflection signals of the test signals sent by the multiple branch fibers to the 0TDR are superimposed, which makes it impossible to distinguish the fault of a specific branch fiber. As shown in FIG. 3, another solution of the prior art, 0TDR is set on the 0NU/0NT side, and the P0N network fiber is monitored from the 0NU/0NT side, and each 0NU/0NT integrates a 0TDR, and each 0NU time-sharing monitors the ONU. The branch fiber and trunk fiber are located, and the test data or result is uploaded to the 0LT through the uplink channel. This method easily locates the fault of the branch fiber or the trunk fiber. However, due to the large number of 0NU/0NTs, the 0TDR device is very expensive, and the cost of implementing the solution is high. It is not realistic to deploy on the 0NU side. Summary of the invention

The object of the embodiments of the present invention is to provide a fault detection method, system and device for a light distribution network, which can perform type detection and/or fault location detection on faults in a light distribution network at a low cost and conveniently.

To achieve the above objective, an embodiment of the present invention provides a fault detection method for a light distribution network, including the following steps:

Check the loss of 'J uplink signal and downlink signal;

When the uplink signal loss and/or the loss of the downlink signal exceeds the normal range, the uplink signal loss is compared with the loss of the downlink signal. If the loss of the downlink signal is greater than the loss of the uplink signal, it is determined that the fiber bending fault has occurred.

Another embodiment of the present invention provides a fault detection method for another optical distribution network, including the following steps:

Check the loss of 'J uplink signal and downlink signal;

When it is detected that the loss of the uplink signal and/or the downlink signal is out of the normal range, the loss is further judged if the loss of the downlink signal and/or the uplink signal of the optical line terminal to all optical network units/optical network terminals exceeds the normal. Range, then determine that the fault occurred in the trunk segment;

If the loss of the downlink signal and/or the uplink signal of all the optical network unit/optical network terminals connected to the same distributed optical fiber exceeds the normal range, it is determined that the fault occurs in the distributed optical fiber;

If the loss of the downlink signal and/or the uplink signal of the optical line terminal to one or several optical network units/optical network terminals exceeds the normal range, and the one or several optical network units/optical network terminals are not connected to the same distribution All of the optical network units/optical network terminals of the optical fiber determine that a fault has occurred on the shunt segment corresponding to the one or more optical network units/optical network terminals.

The invention also provides a fault detection system for a light distribution network, comprising: The first signal detecting module is disposed on the optical line terminal side for detecting optical power of the uplink and downlink signals on the optical line terminal side;

The second signal detecting module is disposed on the optical network unit/optical network terminal side, and is configured to detect optical power of the uplink and downlink signals on the optical network unit/optical network terminal side;

The loss calculation module is connected to the first signal detection module and the second signal detection module, and is configured to calculate the loss of the uplink and downlink signals according to the detected optical power;

The fault analysis module is coupled to the loss calculation module for determining the type of fault and/or the fault location based on the loss of the uplink and downlink signals.

The invention also provides a fault detecting device for a light distribution network, comprising:

a signal detecting module, configured to detect optical power of the uplink and downlink signals;

a loss calculation module, connected to the signal detection module, configured to calculate the loss of the uplink and downlink signals according to the detected optical power;

It can be seen from the above technical solution that the present invention can conveniently detect the type of fault and/or the location of the fault by detecting and analyzing the loss of the uplink and downlink signals, and has no special requirements for the deployment of the optical fiber, and can be identified online and in real time. Fiber bending, connector failure, etc.

The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic structural view of a prior art P 0 N system;

2 is a schematic diagram of a prior art failure test using the 0TDR on the 0LT side;

3 is a schematic diagram of a prior art failure test on the 0NU/0NT side using 0TDR;

4 is a schematic structural diagram of a fault detection system of a light distribution network according to Embodiment 2 of the present invention; and FIG. 5 is a schematic structural diagram of a fault detection apparatus for a light distribution network according to Embodiment 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

An optical power meter is disposed on the OLT side and the 0NU/0NT side to detect optical power of the uplink and downlink signals on the 0LT side and the 0NU/0NT side respectively; and calculate the loss of the uplink signal and the downlink signal according to the detected optical power; For the network, there is loss between the signal transmitting end and the receiving end of the signal. For the downlink signal, the optical power of the downlink signal detected by the 0LT side is greater than the optical power of the downlink signal detected by the 0NU/0NT side, 0LT side and 0NU. The difference between the optical power of the downlink signal detected by the /0NT side is the loss of the downlink signal; for the uplink signal, the optical power of the uplink signal detected by the 0NU/0NT side is greater than the optical power of the uplink signal detected by the 0LT side, and the 0LT side is The difference between the optical powers of the uplink signals detected on the 0NT/0NT side is the loss of the uplink signal. In the actual P0N system, a 0LT connects multiple ONU/0NTs through 0DN, and an optical power meter is set on each 0NU/0NT side, so that the detection data of the loss of multiple sets of uplink and downlink signals is obtained, if detected. If the loss data or loss variation exceeds the normal range, the optical network has failed. By analyzing and processing multiple sets of loss data, information on the type of fault and/or the location of the fault in the optical distribution network can be obtained.

1) Detection of fault type: When the fiber connection failure occurs (such as the end face is contaminated and the connector is loose), the loss changes in the upper and lower directions (1 310 nm and 1490) are consistent. When the fiber is excessively bent, the losses in the upper and lower directions (1 310 and 1490 nm) are different, and the loss in the downstream direction (1490 nm) is larger than that in the upstream direction (1 310 legs), that is, excessive bending The loss of a light wave having a long wavelength is larger than the loss of a light wave having a short wavelength.

After the P0N network is deployed, the uplink and downlink loss of each link is tested, that is, the uplink and downlink loss of the optical link between the 0LT and each ONU/0NT is tested. The loss is used as the uplink and downlink reference loss of the P0N network. The reference loss can also be determined by measuring the up and down loss of 0DN as a reference loss when it is necessary to recalibrate the 0DN loss of the P0N network. After the P0N network is running, real time The upper and lower losses of the ODN are measured to obtain the uplink and downlink real-time losses of the ODN. The difference between the uplink and downlink real-time losses and the uplink and downlink reference losses is the amount of change in the uplink and downlink losses.

When the optical network fails, the loss of the uplink signal and/or the downlink signal will exceed the normal range. Judging whether the loss of the uplink and downlink signals exceeds the normal range can be achieved in two ways:

Method 1. According to the previously determined reference loss, a loss threshold is preset. If the signal loss measured in real time exceeds the threshold, the signal loss is considered to be beyond the normal range.

Mode 2: According to the previously determined reference loss, a loss variation threshold is preset, and the loss measured in real time is subtracted from the reference loss to obtain the loss variation. If the variation of the signal loss exceeds the threshold, the signal loss is considered to be beyond normal. range.

The comparison of the loss degree of the uplink signal and the downlink signal can be directly compared by the uplink and downlink signal loss detected in real time, or can be compared by the loss variation of the uplink and downlink signals.

Therefore, when the uplink signal loss and/or the loss of the downlink signal exceeds the normal range, the uplink signal loss is compared with the loss of the downlink signal. If the loss of the downlink signal is greater than the loss of the uplink signal, it is determined that the fiber bending fault occurs; If the loss of the uplink and downlink signals is equal or the loss of the uplink and downlink signals is equal, it is determined that a connector failure has occurred.

The normal range refers to the range of variation of the loss of the uplink and downlink signals when the 0DN is not faulty.

2) Detection of fault location: As shown in Figure 1, the 0DN can be divided into three parts by the passive optical splitter, the lead fiber, the distributed fiber (Di str ibute fiber) and the split fiber. (Drop Fiber), the split fiber is connected to 0NU/0NT. Due to the existence of such a hierarchical structure, when the loss of the uplink signal and/or the downlink signal is detected beyond the normal range, the detected multiple sets of loss data can be analyzed and processed according to the 0NU/0NT and the distributed fiber (Di s tr The correspondence between ibute F iber and Drop Fiber determines whether the fault occurs in the trunk fiber or a segment of the distributed fiber or the split fiber, specifically:

If the loss of the downlink signal and/or the uplink signal from 0LT to all 0NU/0NTs is out of the normal range, it can be judged that the fault occurs in the trunk segment; If the loss of the downlink signal and/or the uplink signal of all ONUs/ONTs connected by the OLT to the same distribution fiber exceeds the normal range, it is determined that the fault occurs in the distribution fiber;

If the downlink signal and/or uplink signal loss of 0LT to one or several ONU/0NTs exceeds the normal range, and the one or more ONU/0NTs are not all 0NU/0NTs connected to the same distribution fiber, then the fault is determined to occur. On the branch segment corresponding to the one or several ONUs/ONTs.

The corresponding relationship between 0NT/0NU and the branch fiber is as follows: During the P0N network deployment or after deployment, the topology of the 0DN and the relationship between all the 0NU/0NTs connected to the 0DN and the 0DN are recorded for each 0NU/0NT. Fiber (0DN for primary grading). Through the physical identification of 0NU/0NT (such as 0NU/0NT serial number (SN Serial Number) or media access control address (MAC address (Mega ia Acces s Cont ro l Addres s)) or logical identification (such as ONU/ONT The identity (ID) or LLI D (logical link identity) is associated with the topology of the 0DN.

The above-mentioned fault location detection and fault type detection are independent of each other, and can be used together in practical applications. The fault type can be first determined by detecting the fault type, and the fault location is further determined by detecting the fault location. It is also possible to first determine the specific location of the fault by detecting the fault location, and then determine the fault type by detecting the fault type.

The above 0LT side and 0NU/0NT side are not limited to the 0LT device and the 0NU/0NT device, and may be an optical fiber close to the 0LT device and/or the 0NU/0NT device, that is, the optical power meter can be used with both the 0LT device and the 0NU/. The 0NT device is integrated. It is also possible to set a detection point at the fiber near the 0LT device and the 0NU/0NT device. The optical power meter is used to detect the power of the upper and lower optical signals on the optical path separated by the detection point.

The optical power meter in the above embodiment 1 can also be replaced with other instruments or devices capable of measuring optical power.

Example 2 4 is a schematic structural diagram of a fault detection system of a light distribution network according to Embodiment 2 of the present invention, where the system includes:

The first signal detecting module 1 is disposed on the 0LT side for detecting the optical power of the uplink and downlink signals on the 0LT side;

The second signal detecting module 2 is disposed on the 0NU/0NT side for detecting the optical power of the upper and lower signals on the 0NU/0NT side;

The first and second signal detecting modules are capable of detecting optical power of the 1 310 nm and l Onm optical signals. The first and second signal detecting modules may further include an optical power detecting module of 1 310 nm optical signal and an optical power detecting module of 1490 optical signal.

The first signal detecting module and the second signal detecting module may be optical power meters. The signal detection module can be integrated with the 0LT device and the 0NU/0NT device, that is, the signal detection module is integrated in the 0LT and ONU/0NT devices, and the integrated signal detection module is used to measure the transmitted and/or received optical power, ie Optical power of the upstream and downstream wavelengths. In a specific implementation, the signal detection module may be integrated outside the optical transceiver module of the 0LT and ONU/0NT devices, or may be integrated inside the optical transceiver or integrate a part of the functions of the signal detection module into the optical transceiver. Internally, another part of the function is integrated outside the transceiver. In addition, it is also possible to set a detection point near the optical fiber of the 0LT device and the 0NU/0NT device, and use the signal detection module to detect the optical power of the uplink and downlink signals on the optical path separated by the detection point.

The loss calculation module 3 is connected to the first signal detection module and the second signal detection module, and is configured to calculate the loss of the uplink and downlink signals according to the detected optical power;

The fault analysis module 4 is connected to the loss calculation module for determining the type of fault and/or the fault location according to the loss of the uplink and downlink signals.

The loss calculation module and the failure analysis module may be disposed on the 0LT side, or may be disposed in the 0LT and ONU/0NT devices together with the signal detection module. When the loss calculation module and the failure analysis module are integrated with the first signal detection module in the 0LT device, 0LT and The first and second signal detection modules integrated by the ONU/ONT detect the optical power of the two wavelengths (1 31 0/ 1490 nm), and then the 0NU/0NT device passes the detected upstream line of the two wavelengths through the 0DN. The optical power is transmitted to the loss calculation module in the 0LT device to perform loss calculation of the uplink and downlink signals, and then the fault analysis module analyzes and processes the loss of the uplink and downlink signals to obtain a detection result.

Embodiment 3 Figure, the device includes:

a signal detecting module 5, configured to detect optical power of the uplink and downlink signals;

The loss calculation module 6 is connected to the signal detection module, and is configured to calculate the loss of the uplink and downlink signals according to the detected optical power;

The fault analysis module 7 is connected to the loss calculation module for determining the type of fault and/or the fault location according to the loss of the uplink and downlink signals. It is easy to identify fiber bending and connector failure, and can quickly locate the fiber segment where it is located, especially for real-time online detection.

It should be noted that the above embodiments are only intended to illustrate the technical solutions of the present invention and are not to be construed as limiting the embodiments of the present invention. The technical solutions of the present invention may be modified or equivalently replaced, and the modified technical solutions may not deviate from the technical scope of the present invention.

Claims

Rights request

A fault detection method for a light distribution network, comprising:

Check the loss of 'J uplink signal and downlink signal;

2. The method according to claim 1, further comprising: determining that a connector failure has occurred if the losses of the uplink and downlink signals are equal.

3. The method according to claim 1, wherein the method for detecting loss of an uplink signal and a downlink signal comprises:

Detecting optical power of the uplink and downlink signals on the optical line terminal side and the optical network unit/optical network terminal side respectively;

The loss of the uplink signal and the downlink signal are respectively calculated according to the detected optical power.

4. The method according to claim 3, further comprising:

If the downlink signal and/or the uplink signal loss of the optical line terminal to all the optical network unit/optical network terminals are out of the normal range, it is determined that the fault occurs in the trunk segment;

If the loss of the downlink signal and/or the uplink signal of all the optical network unit/optical network terminals connected to the same distributed optical fiber is out of the normal range, it is determined that the fault occurs in the distributed optical fiber;

If the downlink signal and/or uplink signal loss of the optical line terminal to one or several of the optical network unit/optical network terminals exceeds a normal range, and the one or several optical network units/optical network terminals are not connected To all optical network units/optical network terminals of the same distribution fiber, it is determined that the fault occurs on the branch segment corresponding to the one or several optical network units/optical network terminals.

A fault detection method for a light distribution network, comprising the steps of: detecting a loss of a 'J uplink signal and a downlink signal; When it is detected that the loss of the uplink signal and/or the downlink signal is out of the normal range, the loss is further judged if the loss of the downlink signal and/or the uplink signal of the optical line terminal to all optical network units/optical network terminals exceeds the normal. Range, then determine that the fault occurred in the trunk segment;

The method according to claim 5, wherein the detecting the loss of the uplink signal and the downlink signal is specifically:

The optical power of the downlink signal on the optical line terminal side and the optical network unit/optical network terminal side is respectively detected; and the loss of the downlink signal is separately calculated according to the detected optical power.

7. A fault detection system for a light distribution network, comprising:

The first signal detecting module is disposed on the optical line terminal side for detecting optical power of the uplink and downlink signals on the optical line terminal side;

The system according to claim 7, wherein the loss calculation module and the failure analysis module are disposed on the optical line terminal side; the second signal detection module passes the optical distribution network and the The loss calculation module communicates to transmit the optical power of the uplink and downlink signals on the optical network unit/optical network terminal side to the loss calculation module.

The system according to claim 7 or 8, wherein the first signal detecting module is disposed inside the optical line terminal, and is integrally disposed or separated from the transceiver module in the optical line terminal; the second signal The detecting module is disposed inside the optical network unit/optical network terminal, and is integrally or separately disposed with the transceiver module in the optical network unit/optical network terminal.

10. A fault detecting apparatus for a light distribution network, comprising:

And a loss calculation module, configured to be connected to the signal detection module, configured to calculate a loss of the uplink and downlink signals according to the detected optical power; and a fault analysis module, connected to the loss calculation module, configured to determine the loss according to the uplink and downlink signals The type of fault and / or the location of the fault.