WO2012065459A1

WO2012065459A1 - System and method for testing fibre failure in passive optical network

Info

Publication number: WO2012065459A1
Application number: PCT/CN2011/077559
Authority: WO
Inventors: 徐继东
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-11-15
Filing date: 2011-07-25
Publication date: 2012-05-24
Also published as: CN101984561A; CN101984561B

Abstract

Provided are a system and method for testing fibre failure in a passive optical network. The method includes: an optical time domain reflectometer (OTDR) device sends out an instruction for testing a certain branch fibre, and the optical passage of the branch fibre designated by the instruction is connected after a branch fibre selector has received the instruction; the OTDR device, after having sent out an optical length detection signal, analyses a received reflection signal corresponding to the optical length detection signal to find out whether or not the reflection signal is abnormal, so as to determine whether or not the main fibre or the corresponding branch fibre has a failure. By way of the present invention, the failures in the main fibre and all branch fibres of a passive optical network can be monitored, detected and located, and by selecting an OTDR monitoring signal, a corresponding branch fibre thereof can be selected for the detection, which avoids the problem that branch fibres of the same length cannot be distinguished due to signal overlapping thereof.

Description

Detection system and method for optical fiber fault in passive optical network

Technical field

The present invention relates to an optical network system in the field of communications, and more particularly to a system and method for detecting a fiber fault in a passive optical network. Background technique

The rapid development of network technology and the popularization of network applications, such as network communication and online shopping, as well as online entertainment, have become part of modern life, so the existing access network copper (wired) system is far from satisfying. High-speed and broadband demand, and passive optical networks are broadband and high-speed, environmentally friendly and energy-efficient broadband access technologies, and are the best candidates to replace existing access networks, which are being accepted by most operators. It is deployed to meet the growing number of communications users and faster and better service needs.

A Passive Optical Network (PON) is a point-to-multipoint optical (OLT), an Optical Network Unit (ONU), and an Optical Distribution Network (ODN). Usually, an optical line terminal OLT connects a plurality of branch fibers and a corresponding optical network unit ONU to a point-to-multipoint structure through an optical fiber and an optical distribution network ODN optical power splitter (referred to as a splitter).

After the placement and deployment of a large number of passive optical networks, it is necessary to consider the operation and maintenance of the network, especially the detection of fiber lines and the location of faults. In order to reduce operating and maintenance costs, operators want to use an optical path detection device (for example, an Optical Time Domain Reflectometer (OTDR) to detect the trunk and branch fibers of the entire passive optical network, if one The branch fiber fails, and it is hoped that the fault can be quickly detected and the fault can be located and repaired without affecting the services of other branch fibers.

When an OTDR is used to detect such a point-to-multipoint network at the OLT of the central office, the signal of the backbone fiber generally has no problem, but the signals of the branch fiber will encounter the following two problems. 1. If the distance between some of the branch fibers and the splitter is approximately equal, the OTDR cannot distinguish which branch fiber is the signal unless a high resolution OTDR is used. But the highest resolution that can be provided now is 2 meters.

2. If the splitter has a large split ratio, then the Rayleigh reflected signal of the branched fiber will have a large loss when it passes through the splitter. When it reaches the OTDR detector, the signal is already submerged in the noise.

For example: For a 10 km ODN with a 1:32 split ratio, the loss of the splitter is 3*5+3=18 dB, while the 10 km fiber loss is 0.40*10 = 4.0 dB. The maximum dynamic range of a typical OTDR device is around 40 dB. For example, the optical path detection signal passes through the splitter to the end of the branch fiber and then totally reflects (ie, does not count the reflection loss) through the splitter to the OTDR. If other losses (such as connection loss, etc.) are not counted, the total optical path loss will reach 2*18+2*4.0 = 44 dB. This is beyond the operating dynamic range of the OTDR device, so the signal from the branch fiber is submerged in the noise. This shows that the OTDR equipment conventionally used in the local office is a fault of the branch fiber of the ODN which cannot measure the large split ratio. This kind of phenomenon is relatively popular. In the actual PON network, for various reasons, even for a PON with a small split ratio, the reflected signal of the branch fiber cannot be seen by the ordinary OTDR instrument.

The current remedy is to add an optical filter in front of all ONUs that transmits all light less than 1625 nm, but reflects the light of the OTDR above 1625 nm, as shown in Figure 2. When the optical filter is used, the light reflected by the port can be increased by 6 dB. Equipped with a high-resolution OTDR device, it is possible to determine whether the branch fiber is faulty based on whether there is reflected light, but it is still impossible to determine the exact location where the branch fiber fault occurs. If some of the branched fibers are of equal length, the reflected light overlaps, and even high-resolution OTDR devices cannot distinguish the difference. To make matters worse, for large ODP (such as 1:128 split ratio), the gain brought by the filter may not be enough for the loss of the splitter, so the OTDR equipment in the office may not receive it. Any information from the branch fiber. Summary of the invention

The technical problem to be solved by the present invention is to provide a system and method for fault detection of a passive optical network fiber, which is used to solve the problem that any branch fiber can be detected and located by an OTDR device in the office. In order to solve the above technical problem, a passive optical network fiber fault detection system is provided, including: an optical time domain reflectometer (OTDR) device, a wavelength division multiplexing coupler, a wavelength selective coupler, a branch fiber selector, and a wavelength selective router connected to the branch fiber, wherein the wavelength division multiplexing coupler is connected to the OTDR device and an optical line terminal (OLT), and is connected to the wavelength selective coupler through a trunk fiber; a selective coupler coupled to the splitter and the branch fiber selector; the branch fiber selector being coupled to the wavelength selective coupler and each of the wavelength selective routers; each of the wavelength selective routers further Corresponding branch fiber connection, connected to the optical network unit by the branch fiber, wherein

The OTDR device is configured to: emit an optical path detection signal to the wavelength division multiplexing coupler; and analyze whether the reflected signal is abnormal according to the received reflected signal corresponding to the optical path detection signal to determine a trunk optical fiber or corresponding Whether the branch fiber is faulty;

The wavelength division multiplexing coupler is configured to: direct the optical path detection signal to the backbone optical fiber; and separate the reflected signal corresponding to the optical path detection signal from the backbone optical fiber, and transmit the reflected signal to the OTDR device;

The wavelength selective coupler is configured to: separate the optical path detection signal from the trunk fiber to be transmitted to the branch fiber selector; and return the received reflection signal corresponding to the optical path detection signal back to the trunk fiber Upper

The branch fiber selector is configured to: transmit the optical path detection signal to a wavelength selection router that is previously turned on; and transmit the received reflection signal corresponding to the optical path detection signal to the pre-connected wavelength selection Coupler

The wavelength selection router is configured to: transmit the optical path detection signal to a corresponding branch fiber, and then separate a reflection signal corresponding to the optical path detection signal from an uplink signal of the branch fiber, where the optical path is The reflected signal corresponding to the detection signal is transmitted to the branch fiber selector.

Preferably, the above system also has the following features:

The OTDR device is further configured to: send a command signal for detecting a branch fiber to the wavelength division multiplexing coupler before the optical path detection signal is sent to the wavelength division multiplexing coupler or after the detection ends Transmitting, by the wavelength division multiplexing coupler and the wavelength selective coupler, the branch fiber selector, The branch fiber selector is further configured to: after receiving the command signal, turn on or off the wavelength selection router according to the command signal.

Preferably, the above system further has the following features: The branch fiber selector includes: a passive optical module, an optical switch controller, and a 1 X N optical switch, where:

The passive optical module includes an optical circulator module and a beam splitting module, and the optical circulator module includes: an input interface, an output interface, a first access interface, and a second access interface, and the optical signal entering from the input interface The first input and output interface output, the optical signal entering from the first access interface is output from the second access interface, and the optical signal from the second access interface is output from the output interface; the optical splitting module includes: a common interface, a first optical splitting interface, and a second optical splitting interface, after the optical signal entering the shared optical interface is split into two optical signals, and outputted from the first optical splitting interface and the second optical splitting interface respectively;

The output interface of the optical circulator module is connected to the common interface of the optical splitting module, the first optical splitting interface is connected to the input interface of the optical circulator module, the second optical splitting interface and the optical switch controller Connecting, the optical switch controller is connected to the optical switch; the wavelength selective coupler is connected to the first access interface, and the second access interface is connected to a universal port of the optical switch, the optical switch The N branch ports are connected to the corresponding wavelength selective routers.

The optical switch controller is configured to: if the instruction for detecting a branch fiber is detected, and issue an associated control command to the optical switch;

The optical switch is configured to: turn on or off the optical path of the branch port of the optical switch and the branch port corresponding to the branch fiber specified by the command according to the control command.

Preferably, the above system also has the following features:

The optical circulator module is a four-interface optical circulator, or

The optical circulator module is composed of two three-interface optical circulators.

Preferably, the above system further has the following features: the optical switch controller includes a light receiver and an optical switch control module,

The optical receiver is configured to: convert the received optical signal into an electrical signal, and then transmit the received optical signal to the optical switch control module;

The optical switch control module is configured to: after receiving the electrical signal, if the electrical signal is determined To monitor the command signal, an associated control command is issued to the optical switch.

Preferably, the system further has the following features: The optical splitting module is configured to: divide an optical signal that is input from the common interface into an optical signal of a first optical power and an optical signal of a second optical power, where the first optical An optical signal of power is output from the first optical splitting interface, and an optical signal of the second optical power is output from the second optical splitting interface.

Preferably, the above system also has the following features:

The wavelength division multiplexing coupler is a first filter, which is configured to: a port for allowing an optical signal input or output of an OTDR wavelength to be connected to the OTDR device, and a port for allowing an optical signal input or output of a non-OTDR wavelength OLT connection, the shared port is connected to the backbone fiber;

The wavelength selective coupler is a second filter, which is configured to: a port for allowing an optical signal input or output of an OTDR wavelength to be connected to the branch fiber selector, and a port for allowing an optical signal input or output of a non-OTDR wavelength to be The splitter is connected, and the shared port is connected to the trunk fiber;

The wavelength selection router is a third filter, which is configured to: a port for allowing an optical signal input or output of an OTDR wavelength to be connected to the branch fiber selector, a port for allowing an optical signal input or output of a non-OTDR wavelength to be The splitter is connected, and the shared port is connected to the corresponding branch fiber.

The first, second and third filters may be the same device in terms of physical properties. Preferably, the above system also has the following features:

The wavelength division multiplexing coupler is further configured to: direct the downlink signal of the OLT into the trunk fiber; separate the uplink signal from the backbone fiber, and transmit the uplink signal to the OLT;

The wavelength selective coupler is further configured to: separate the downlink signal from the backbone optical fiber, and transmit the downlink signal to the optical splitter; and send the received uplink signal back to the trunk optical fiber;

The optical splitter is configured to: transmit the downlink signal to each of the wavelength selection routers; and output an uplink signal sent by each of the wavelength selection routers to the wavelength selective coupler;

The wavelength selection router is further configured to: transmit the downlink signal to a corresponding branch fiber, and then transmit an uplink signal of the branch fiber to the beam splitter.

In order to solve the above problems, the present invention also provides a method for detecting faults in a passive optical network optical fiber, and performing detection based on the foregoing system, including: The OTDR device sends an instruction for detecting a branch fiber, and after receiving the instruction, the branch fiber selector connects to the optical path of the branch fiber specified by the instruction;

After the optical path detection signal is sent, the OTDR device analyzes whether the reflected signal is abnormal according to the received reflected signal of the optical path detection signal to determine whether there is a fault in the trunk fiber or the corresponding branch fiber.

Preferably, the above method also has the following features:

After the detection of the OTDR device is finished, an end detection instruction is issued;

After receiving the end detection command, the branch fiber selector disconnects the optical path specified by the instruction. Preferably, the wavelength of the optical path detection signal is selected to avoid uplink and downlink service wavelengths.

Preferably, the above method further has the following features: The wavelength of the optical path detection signal is between 1625 nm and 1675 Å.

In summary, the embodiments of the present invention provide a system and method for detecting a fiber fault of a passive optical network, which can monitor, detect, and locate faults of the trunk and all branch fibers of the passive optical network, and select signals by selecting an OTDR. The branch fiber corresponding to the branch fiber is selected for detection, thereby avoiding the problem that the signal of the equal-length branch fiber overlaps and cannot be distinguished. At the same time, the detection signal and the reflected signal of the OTDR are bypassed by the optical splitter and returned to the main fiber, so that the loss of the optical splitter is independent of the optical path detection signal, which ensures the detection capability and accuracy of the OTDR instrument for the branched optical fiber. BRIEF abstract

1 is a schematic structural view of a conventional passive optical network;

2 is a schematic structural diagram of a conventional optical path detecting passive optical network system;

3 is a schematic structural diagram of an optical path detecting passive optical network system according to the present invention;

4 is a schematic structural view of a wavelength division multiplexing coupler of the present invention;

Figure 5 is a schematic structural view of a wavelength selective coupler of the present invention;

6 is a schematic structural diagram of a wavelength selection router according to the present invention;

7 is a schematic structural view of Embodiment 1 of a branch fiber selector according to the present invention;

8 is a schematic structural diagram of Embodiment 2 of a branch fiber selector according to the present invention; Preferred embodiment of the invention

Referring to FIG. 3, a system for detecting a fiber fault of a passive optical network according to an embodiment of the present invention includes: an OTDR device capable of transmitting a monitoring command, a wavelength division multiplexing coupler, a wavelength selective coupler, a branch fiber selector, and more than one and a splitter Connected wavelength selection routers. Wherein, the wavelength division multiplexing coupler is connected to the OTDR device and the optical line terminal OLT, and is connected to the wavelength selective coupler through the trunk fiber; the wavelength selective coupler is connected to the beam splitter and the branch fiber selector; the branch fiber selector and each wavelength Select routers to connect; each wavelength selection router is connected to the optical network unit through the corresponding branch fiber. A splitter is connected to each wavelength selective router.

An OTDR device capable of transmitting a monitoring command for transmitting a command for detecting a corresponding branch fiber to a wavelength division multiplexing coupler (for example, transmitting an associated command for an optical switch), and subsequently emitting a signal for optical path detection; Determining whether there is a fault in the trunk fiber or the corresponding branch fiber according to whether the received reflected signal corresponding to the optical path detection signal is abnormal.

Here is a brief description of the difference between the command signal and the optical path detection signal. The optical path detection signal is a single-pulse optical signal, and the command signal is a one-byte eight-bit signal composed of eight optical pulses. It is easy to distinguish them; at the same time, the OTDR itself knows when to send the command signal, and when the illuminating path detects the signal, it only analyzes the reflected signal received by the optical path detection, and determines whether it is abnormal or not to determine the trunk fiber and corresponding Whether the branch fiber is faulty.

Here, if the reflected signal is a Fresnel reflected signal or the Rayleigh reflected signal has a sudden change, it can be determined that the trunk fiber or the corresponding branch fiber has a fault, and if it is a continuous Rayleigh reflected signal, it can be determined that the trunk fiber or the corresponding branch fiber has no fault.

a wavelength division multiplexing coupler for transmitting all the OTDR signals and the downlink signals of the optical line terminals to the trunk fiber, and transmitting the optical path detection reflection signals separated on the backbone fibers to the OTDR device, and separating The outgoing uplink signal is transmitted to the optical line terminal OLT.

a wavelength selective coupler for separating the OTDR signal from the downstream light of the backbone fiber and passing it to the branch fiber selector, the remaining downstream light being passed to the beam splitter; and the received light from the branch fiber selector The reflected signal detected by the process is guided back to the main fiber and will pass through the optical splitter. The upstream signal is transmitted to the backbone fiber.

a branch fiber optic selector, configured to turn on a wavelength selective router connected thereto according to an instruction in the OTDR signal, and transmit an optical path detection signal from the wavelength selective coupler through an optical path of the optical switch to the corresponding wavelength selective router, and Transmitting an optical path detection reflected signal from a branch fiber of the wavelength selective router to a wavelength selective coupler;

The branch fiber selector may include a passive light guiding module, an optical receiver, and a light-feeding switch control chip. Specifically, the branch fiber selector is configured to pass the OTDR signal from the wavelength selective coupler through the passive light guiding module, and divide a part of the light. On the monitored optical receiver (PD), the PD converts the received optical signal into an electrical signal to the optical switch control chip (Chip), and the optical switch control chip will judge according to the received signal, if it is a monitoring command The signal will issue relevant commands to the optical switch according to requirements. The optical switch accepts relevant instructions to perform related actions, such as: the optical switch is connected to the path between the wavelength selective coupler and the associated wavelength selective router; if it is not the monitoring command signal, that is, the light The detection signal, the controller will have no action, but the optical path detection signal will pass through the optical path of the optical switch, reach the corresponding wavelength selection router, and then enter the branch fiber, and the optical path detection reflection signal will also return to the trunk along the optical path. optical fiber.

a wavelength selection router for transmitting a downlink signal from the optical splitter to all of the branch fibers; and transmitting an optical path detection signal from the branch fiber selector to the corresponding branch fiber; and then separating the optical path from the uplink signal of the branch fiber The detected reflected signal is transmitted to the branch fiber selector, and the remaining separated uplink signals are transmitted to the beam splitter.

The wavelength division multiplexing coupler is located at the local OLT, and the purpose is to import and export the OTDR signal when the normal service is not affected. Referring to FIG. 4, the wavelength division multiplexing coupler may be composed of a thin film filter or may be composed of a wideband filter. The thin film filter has a light average reflection above 1625 nm (the OTDR wavelength ranges from 1625 nm to 1675 nm, which is in compliance with the International Telecommunications Union ITU-T L.66 standard), such as the R port [allows light above 1625 nm (OTDR wavelength)). Signal input or output], but for light less than 1625nm (non-OTDR wavelength), such as P port (allows light signal input or output less than 1625nm). The connection is as follows, the P port is connected to the OLT, the C port is connected to the backbone fiber, and the R port is connected to the OTDR device. The thin film filter is used to import the OTDR signal outputted by the OTDR device to the trunk optical fiber, and transmit the OTDR reflected signal to the OTDR device, while maintaining normal uplink and downlink communication between the OLT and the ONU. In the embodiment of the present invention, a wavelength selective coupler may be disposed at the entrance of the optical splitter. As shown in FIG. 5, the wavelength selective coupler may be composed of a thin film filter (TFF), or may be broadband filtered. Composition. The thin film filter reflects light above 1625 nm (or OTDR wavelength), such as R port, but transmits light less than 1625 nm (non-OTDR wavelength), such as P port. The connection is as follows, the P port is connected to the optical splitter, the C port is connected to the backbone fiber, and the R port is connected to the branch fiber selector. The thin film filter is used to introduce the OTDR signal to the branch fiber selector and direct the OTDR reflection signal of the branch fiber back to the trunk fiber, while maintaining normal uplink and downlink communication between the OLT and the ONU.

There is a branch fiber selector next to the optical splitter ODN splitter, which is an active device. Referring to Figure 7 or Figure 8, the branch fiber selector can be composed of three parts.

The first part is a passive light guiding module. As shown in Figure 7, it consists of a four-interface optical circulator and a splitter: The four-interface optical circulator has four interfaces, of which interface 1 is the input interface, that is, only light. Incoming, the light coming in from interface 1 can only be output from interface 2; interface 2 is the input and output interface, the light coming in from interface 2 can only be output from interface 3; interface 3 is the input and output interface, the light coming in from interface 3 Can only be output from interface 4; interface 4 is the output interface, that is, the light can only go out, only the light of interface 3 can be output from interface 4; the optical splitter is an optical power splitter, that is, Splitter, which determines the optical power The ratio is output from a different interface and is a two-way device. The splitter used in FIG. 7 has three interfaces, the C interface is a universal port, the interface 1 is a first split optical interface, and most of the light split from the C interface (for example, 90%) is output from the interface 1; the interface 2 is the second. The optical interface, the small part of the light (for example, 10%) separated from the C interface is output from the interface 1. The proportion of the splitting light can be adjusted by the user according to the actual situation; the connection is as shown in Fig. 7, and the optical circulator interface 3 and The wavelength selective coupler is connected, the interface 2 is connected with the universal interface of the optical switch, and the interface 1 is connected with the first interface of the optical splitter, the interface 4 is connected with the universal interface of the optical splitter, the second interface of the optical splitter and the optical switch controller The light receivers are connected.

FIG. 8 is another embodiment of a passive light guiding module. The optical circulator of the three interfaces is replaced by two optical circulators of three interfaces, and the interface 1 of the optical circulator of the three interfaces is an input interface. The interface 2 of the optical circulator of the three interfaces is an access interface, the light entering from the interface 1 is from the interface 2, and the light entering from the interface 2 is output from the interface 3; the interface 3 of the optical circulator of the third interface is the output interface The light only goes out; with this feature, the interface 3 of the first optical circulator and the interface 1 of the second optical circulator The optical circulator corresponding to the four interfaces is formed, and the interface 3 of the second optical circulator is equivalent to the interface 4 of the four-interface optical circulator; the interface 2 of the second optical circulator is equivalent to the four-interface optical circulator Interface 3; interface 2 of the first optical circulator is equivalent to interface 2 of the four-interface optical circulator; interface 1 of the first optical circulator is equivalent to interface 1 of the four-interface optical circulator; other connections and functions and figures 7—To.

The second part is the optical switch controller, which consists of two parts, one is a photoelectric converter (PD), whose main function is to accept the OTDR's command to the optical switch at the OLT, and then convert the received optical signal into an electrical signal. It is transmitted to the optical switch control chip (ie, the controller), and the controller performs related operations on the optical switch according to the requirements of the instruction.

Further, the command system can be divided into four working states:

State 1: Turn on the power of the optical switch. The main reason is to save energy. In normal time, the optical switch is in the no-power off state. After the controller receives the command, the optical switch power is turned on, so that the optical switch is in the state of preheating and accepting commands.

State 2: Turn on the optical path of a branch fiber, and the controller requires the optical switch to turn on a certain branch according to the instruction, and the optical switch operates according to the requirements;

State 3: Disconnecting the optical path, the controller requests the optical switch to open a branch according to the instruction, and the optical switch operates according to the requirements;

State 4: The main reason for turning off the power of the optical switch is to save energy. After the controller receives the command, the optical switch power is turned off, so that the entire branch fiber selector is in a standby state, that is, only the optical switch controller has a small amount of power supply. .

State 2 and State 3 can be repeated throughout the instruction operation because more than one branch fiber may be tested during the test, and several, or all, may need to be detected. The operation process can be summarized as follows, state one to state two to state three to state two to state three ... until state four.

The connection is as shown in FIG. 7. The optical receiver is connected to the second interface of the optical splitter, and the electrical part is connected to the optical switch control chip through a wire, and the optical switch control chip is connected to the electrical part of the optical switch to be turned on or off. The power supply of the optical switch and the optical switch according to the command are connected.

The third part is the optical switch of ΙχΝ, where N is determined by the number of branching fibers, and its main function is to set a light path for the wavelength selective coupler and the selected wavelength selection router, so that the optical path inspection The measured signal reaches the branch fiber through the channel, and the optical path detection reflection signal of the branch fiber can also return to the trunk fiber through the path; the line connection is as shown in FIG. 7 or FIG. 8, and the interface of the optical switch and the optical circulator are connected. 2 is connected, and 1 to N branch ports are connected to the wavelength selective routers of the corresponding branch fibers. Once the connection is successful, the branch fibers are identified by the optical switches, which indicates that different branch ports are selected, and different branch fibers are selected accordingly. . The identification information will be stored by the OLT or the OTDR. After the information is obtained, if a branch fiber is to be detected, the optical switch can be connected to the optical path between the branch port and the common port of the branch fiber. The optical switch is connected to the optical switch controller and its operating state is determined by the optical switch controller.

A wavelength selective router is connected in front of each branch fiber of the optical splitter, and the optical splitter can be an equal power splitting device. As shown in FIG. 6, the wavelength selective router can be composed of a thin film filter (TFF). The thin film filter reflects light above 1625 nm (wavelength of OTDR) (such as R port), but transmits light below 1625 ( (non-OTDR wavelength) (such as P port). The connection is as follows, the P port is connected to the splitter, the C port is connected to the branch fiber, and the R port is connected to the branch fiber selector. The thin film filter is configured to introduce an optical path detection signal from the branch fiber selector onto the branch fiber, and direct the optical path detection reflection signal of the branch fiber to the branch fiber selector, and only the selected wavelength selection router can The above optical path detection signal and the optical path detection reflection signal are guided, and the normal uplink and downlink communication between the OLT and the ONU is maintained, and the selected wavelength selection router is not selected, and only the normal uplink and downlink communication between the OLT and the ONU is performed.

The optical path detecting system composed of the above series of auxiliary optical function modules can intelligently and quickly detect and locate the fault of the trunk fiber and any branch fiber by using an OTDR device capable of issuing commands. . Moreover, the l x N optical switch is used to select the branch fiber associated with it, thus avoiding signal overlap of the equal length branch fibers and being indistinguishable. At the same time, the optical path detection signal and the optical path detection reflection signal of the branch fiber are bypassed by the optical splitter and returned to the main fiber, thereby avoiding the attenuation of the optical path detection signal by the optical splitter, and ensuring that the OTDR instrument can receive the optical path of the branched optical fiber. Detect the reflected signal. The wavelength of the OTDR generally needs to avoid the uplink and downlink service wavelengths. According to ITU-T L.66, the wavelength is generally selected between 1625 nm and 1675 nm, and the non-OTDR wavelength generally refers to the uplink and downlink service wavelengths, and also includes the video signal wavelength. .

The system of the embodiment of the present invention can very effectively help the operator to quickly find the location of the fault, which will greatly shorten the maintenance time and reduce the maintenance cost. Especially when a branch fiber occurs In the case of a barrier, the operator can quickly detect and locate the fiber and perform maintenance without affecting the normal operation of other branch fibers. These will greatly reduce the operator's operating and maintenance costs.

The technical solutions of the present invention are described in detail below with reference to the accompanying drawings and preferred embodiments. The following examples are intended to illustrate and explain the present invention and are not intended to limit the invention.

In order to realize the intelligent detection of the optical fiber system of the passive optical network, the passive optical network is first modified to add some passive optical function modules. According to the requirements of Figure 3, a wavelength division multiplexing coupler is added at the OLT. Its main function is to connect the OTDR equipment to the trunk optical fiber, so that the optical path detection signal can enter the passive optical network system, and the corresponding reflected signal can Passed through the network to the OTDR detector.

Inserting a wavelength selective coupler in front of the optical splitter, its main function is to separate the OTDR signal from the backbone fiber and transmit it to the branch fiber selector, and transmit the optical path detection and reflection signal of the branch fiber back to the backbone fiber, while ensuring Normal communication of the line signal.

Inserting a wavelength selective router in front of each branch fiber after the optical splitter, its main function is to introduce the optical path detection signal from the branch fiber selector into the branch fiber, and to reflect the optical path detection reflection signal of the branch fiber from the uplink signal. It is separated and transmitted to the branch fiber optic selector, and the uplink and downlink communication is guaranteed to operate normally.

Place a branch fiber optic selector next to the splitter, as shown in Figure 7 or Figure 8. One end is connected to the wavelength selective coupler, and the other end is connected to each wavelength selective router. The main function is to connect the optical switch according to the OTDR command. Universal port and branch port.

When all of these modules are connected as shown in Figure 3, the OTDR equipment can intelligently test the entire passive optical network system. The entire optical path detection process will be described below. Including the following steps:

S10. The OTDR device sends an instruction for detecting a branch fiber. After receiving the instruction, the branch fiber selector connects to the optical path of the branch fiber specified by the instruction.

When the passive optical network needs to be detected, first connect the OTDR device to the wavelength division multiplexing coupling in the local office. On the combiner, and then for a desired measurement branch fiber, the OTDR meter uses the OTDR wavelength light to issue a command to turn on the optical switch to the branch fiber selector, and then wait a few seconds before issuing the command to turn on the desired measurement branch fiber. .

S20: After the optical path detection signal is sent, the OTDR device analyzes whether the reflected signal is abnormal according to the received reflected signal corresponding to the optical path detection signal to determine whether the corresponding branch fiber has a fault.

When the optical switch executes the command, the OTDR can emit an optical path detection signal, and the R interface of the WDM coupler connected to the OTDR is coupled into the main fiber for transmission, and the reflected signal returns the original path to the OTDR instrument. On the other hand, if there is any fault in the trunk fiber, its anomalous signal will be quickly detected by the OTDR and can be quickly located. If there is no problem with the backbone fiber, the detection signal will be transmitted to the C interface of the wavelength selective coupler and then separated from the R interface to the interface of the branch fiber selector circulator.

As shown in Figure 7, the branch fiber selector, if the optical circulator is a four-port optical circulator, the interface is the interface 3 of the optical circulator, and then the interface 4 of the optical circulator enters the common interface of the optical splitter. A small part of the light exits from the second interface of the optical splitter and enters the optical receiver of the optical switch controller. After the optical switch control chip determines that this is the optical path detection signal, then there is no action; and most of the light is from the optical splitter. The first interface is out, enters the interface 1 of the optical circulator, exits from the interface 2 of the optical circulator; reaches the universal port of the optical switch, exits from the branch port that communicates with the optical switch, and enters the wavelength selective router connected to the optical switch. The R interface is then output from the C interface of the wavelength selective router to the branch fiber connected to it, and transmitted to the ONU connected thereto.

The optical path detection reflection signal of the branch fiber returns to the original path through the R interface of the wavelength selection router to the branch port of the optical switch of the branch fiber selector, and is output from the general port of the optical switch, as shown in FIG. The interface 2 of the optical circulator enters the R interface of the wavelength selective coupler connected to the optical circulator after exiting the interface 3 of the optical circulator, and then exits from the C interface, enters the trunk optical fiber, and reaches the wavelength division through the transmission of the trunk optical fiber. The coupler's C interface is then separated and output from its R interface back to the OTDR, so each time the OTDR will show a reflected signal from the backbone fiber plus a branch fiber.

The branch fiber selector may also be composed of two three-interface optical circulators of FIG. 8, wherein the only difference is that two three-interface circulators are used instead of the four-interface circulator, that is, the second optical circulator The interface 2 is equivalent to the interface 3 of the four-interface circulator; the interface 2 of the first optical circulator is equivalent to the interface 2 of the four-interface circulator; the interface 3 of the second optical circulator is equivalent to the interface 4 of the four-interface circulator; The interface 1 of the optical circulator is equivalent to the interface 1 of the four-interface circulator; at the same time, the interface 3 of the first optical circulator is connected to the interface 1 of the second optical circulator, and the other connections are the same as those of FIG. The transmission of light here is consistent with the previous description and will not be repeated one by one.

If other branch fibers are to be detected, repeat the above steps, that is, the OTDR will issue an instruction to disconnect the path, then wait a few seconds to issue an instruction to connect the new branch fiber, and then issue a new optical path detection signal, OTDR. The instrument will detect whether the reflected signal is abnormal according to the received optical path and determine whether it is faulty and locate the fault. Repeat the above steps until the end of the measurement.

Further, after the detection is completed, the OTDR device issues a detection end command, and after receiving the instruction, the branch fiber optic selector disconnects the optical path specified by the instruction and turns off the optical switching power supply.

When the detection is completed, the OTDR device sends an instruction to disconnect the optical path to the branch fiber selector with the light of the OTDR wavelength, and then waits for a few seconds before issuing an instruction to turn off the optical switching power supply, so that the branch fiber selector returns to the original state. The state of waiting for electricity.

Now let's look at the communication between the OLT and the ONU during the detection process, as shown in Figure 3. The first is the downstream optical link, and the OLT emits the downstream light, which is transmitted through the wavelength division multiplexing coupler. See Figure 4, passing through the backbone fiber to the wavelength selective coupler, see Figure 5, and then through the filter to the splitter. The splitter passes through the splitter to each wavelength selective router. See Figure 6. The filter passing through the wavelength selective router reaches each branch fiber and then reaches the corresponding ONU through the branch fiber.

The upstream optical link is the upstream light sent by the ONU and passes through the branch fiber to the wavelength selective router. See Figure 6. First, the filter of the wavelength selective router is passed to the optical splitter, and passes through the optical splitter to reach the wavelength selective coupler. 5, through the wavelength selective coupler to the backbone fiber, through the trunk fiber to the wavelength division multiplexing coupler, see Figure 4, through the WDM coupler to the OLT. The OTDR signal and the reflected signal do not interfere with the downstream and upstream optical links throughout the transmission.

During the entire optical path detection from the beginning to the end, the communication between the OLT and the ONU of the passive optical network is always smooth, that is, their services are not interrupted. If a branch fiber fails, the user of other branch fibers will not be aware of the OTDR for detection and fault location, and subsequent repair and recovery of normal operation. This will be greatly reduced The cost of the operator's repairs.

The spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the inventions

INDUSTRIAL APPLICABILITY Embodiments of the present invention provide a system and method for detecting a fiber fault of a passive optical network, which can monitor, detect, and locate faults of a trunk of the passive optical network and all branch fibers, and select by selecting an OTDR monitoring signal. The branch fiber corresponding to the detection is detected, thereby avoiding the problem that the signals of the equal-length branch fibers overlap and cannot be distinguished. At the same time, the detection signal and the reflection signal of the OTDR are bypassed by the optical splitter and returned to the main fiber, so that the loss of the optical splitter is independent of the optical path detection signal, which ensures the detection capability and accuracy of the OTDR instrument for the branched optical fiber.

Claims

Claim

A passive optical network fiber fault detection system, comprising: an optical time domain reflectometer (OTDR) device, a wavelength division multiplexing coupler, a wavelength selective coupler, a branch fiber selector, and a beam splitter and a branch fiber a wavelength selective router, wherein the wavelength division multiplexing coupler is connected to the OTDR device and an optical line terminal (OLT), and is connected to the wavelength selective coupler through a trunk fiber; the wavelength selective coupler and the a splitter is connected to the branch fiber selector; the branch fiber selector is connected to the wavelength selective coupler and each of the wavelength selective routers; each of the wavelength selection routers is further connected to a corresponding branch fiber, Connected to the optical network unit by the branch fiber, where

2. The system of claim 1 wherein

The OTDR device is further configured to: send a command signal for detecting a branch fiber to the wavelength division multiplexing coupler before the optical path detection signal is sent to the wavelength division multiplexing coupler or after the detection ends Transmitting, by the wavelength division multiplexing coupler and the wavelength selective coupling The combiner is passed to the branch fiber selector,

The branch fiber selector is further configured to: after receiving the command signal, turn on or off the wavelength selection router according to the command signal.

3. The system of claim 2, wherein the branch fiber selector comprises: a passive optical module, an optical switch controller, and an lxN optical switch, wherein:

4. The system of claim 3, wherein

The optical circulator module is a four-interface optical circulator, or

5. The system of claim 3, wherein the optical switch controller comprises a light receiver and an optical switch control module,

The optical receiver is configured to: convert the received optical signal into an electrical signal, and then transmit the optical signal to the optical switch control module; The optical switch control module is configured to: after receiving the electrical signal, if it is determined that the electrical signal is a monitoring command signal, issue an relevant control command to the optical switch.

6. The system of claim 3, wherein

The optical splitting module is configured to: divide an optical signal that is to be input from the common interface into an optical signal of a first optical power and an optical signal of a second optical power, where the optical signal of the first optical power is from the first optical split The interface outputs an optical signal of the second optical power output from the second optical splitting interface.

7. The system of any of claims 1-6, wherein

8. The system of claim 1 wherein

The wavelength selective coupler is further configured to: separate the downlink signal from the trunk fiber, and transmit the downlink signal to the optical splitter; and direct the received uplink signal to the trunk optical fiber;

A method for detecting a fiber optic fault in a passive optical network, the system for detecting according to any one of claims 1-8, comprising: The OTDR device sends an instruction for detecting a branch fiber, and after receiving the instruction, the branch fiber selector connects to the optical path of the branch fiber specified by the instruction;

10. The method of claim 9, wherein

After receiving the end detection command, the branch fiber selector disconnects the optical path specified by the instruction.

11. The method of claim 9 or 10, wherein

The wavelength of the optical path detection signal is selected to avoid the uplink and downlink service wavelengths.

12. The method of claim 11 wherein

The wavelength of the optical path detection signal is between 1625 nm and 1675 nm.