CN102098098B - System for detecting fiber faults of passive optical network - Google Patents

Abstract

The invention discloses a system for detecting fiber faults in passive optical networks, comprising: optical path detection (OTDR) equipment, wavelength division multiplexing couplers, wavelength selective couplers, branch fiber selectors and more than one optical splitter connected Wavelength selective router; wavelength division multiplexing coupler is connected with OTDR equipment and optical line terminal, and connected with wavelength selective coupler through trunk fiber; wavelength selective coupler is connected with optical splitter and branch fiber selector; branch fiber selector is connected with each Each wavelength selection router is connected to the optical network unit through a corresponding branch fiber. The present invention selects any branch fiber to be detected by an optical switch, avoids signal overlap of branch fibers with equal lengths, and cannot be distinguished, and makes the reflected signal of the OTDR of the branch fiber bypass the optical splitter and return to the main fiber, avoiding the optical splitter, especially the large branch fiber. The attenuation of the reflected signal by the optical splitter of the light ratio ensures that the detector of the OTDR can receive the signal.

Description

A System for Detecting Fiber Faults in Passive Optical Networks

technical field

The invention relates to an optical network system in the field of communication, in particular to a system for detecting fiber failures in a passive optical network.

Background technique

The rapid development, maturity and low cost of optical fiber communication technology in the past ten years have made fiber-to-the-home a more and more popular reality, so that optical fiber for broadband access gradually replaces the existing copper wire (wired) system, that is, optical fiber It has become a trend to advance copper and retreat. The passive optical network is one of the widest, fastest and most environmentally friendly broadband access technologies, which is being accepted and deployed by most operators to meet the growing number of communication users and faster and better service requirements.

Passive Optical Network (PON, Passive Optical Network) is a point-to-multipoint optical fiber access technology, as shown in Figure 1. A passive optical network includes an optical line terminal (OLT, Optical Line Terminal), an optical network unit (ONU, Optical Network Unit) and an optical distribution network (ODN, Optical Distribution Network). It is usually a point-to-multipoint structure composed of an optical line terminal OLT connected to multiple optical network units ONU through an optical power splitter (referred to as an optical splitter) of an optical distribution network ODN.

After the installation 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 optical fiber lines and the location of faults. In order to reduce operation and maintenance costs, operators hope to use an optical distance detection device (OTDR) at the OLT to detect the trunk and branch fibers of the entire passive optical network. If a branch fiber fails, it is hoped that the other branch fibers will not be affected In the case of business, faults can be quickly found and faults can be located and repaired.

When OTDR is used to detect this kind of point-to-multipoint network at the office OLT, the signal of the main fiber will generally have no problem, but the signal of the branch fiber will encounter the following two problems.

1. If the distance from part of the branch fiber to the splitter is approximately equal, the OTDR cannot tell which branch fiber is the signal, unless a high-resolution OTDR is used. But the highest resolution available now is 2 meters.

2. If the splitting ratio of the optical splitter is large, the Rayleigh reflection signal of the branch fiber will have a large loss when passing through the optical splitter. When it reaches the detector of the OTDR, the signal has been submerged in the noise.

For example: for a 10km ODN with a splitting ratio of 1:32, the loss of the optical splitter is 3*5+3=18dB, while the loss of the 10km optical fiber is 0.35*10=3.5dB. The dynamic range of general OTDR equipment is 35 to 40dB. For example, the signal of OTDR reaches the end of the branch fiber through the optical splitter, and then it is totally reflected (that is, regardless of the reflection loss) and reaches the detector of the OTDR through the optical splitter. If other losses (such as connection loss, etc.) are not considered, the full optical path loss of the OTDR signal will be 2*18+2*3.5=42dB. This has exceeded the working dynamic range of the OTDR equipment, so the signal of the branch fiber has been submerged in the noise. This shows that the traditional OTDR equipment used in the local office cannot measure the fault of the branch fiber of the ODN with a large splitting ratio. This phenomenon is relatively common. In the actual PON network, due to various reasons, even for PON with a small splitting ratio, the reflected signal of the branch fiber cannot be seen with ordinary OTDR instruments.

The existing remedy is to add an optical filter in front of all ONUs, which transmits all light below 1625nm, but reflects OTDR light above 1625nm, as shown in Figure 2. After using the optical filter, the light reflected by the port can be increased by 6dB. Equipped with high-resolution OTDR equipment, it is possible to determine whether the branch fiber is faulty according to whether there is reflected light, but it is still impossible to determine the exact location of the branch fiber fault. If the lengths of some branch fibers are basically equal, the reflected light will overlap, and even high-resolution OTDR equipment cannot distinguish the difference. What's worse is that for ODN with a large splitting ratio (such as: above 1:128 splitting ratio), the gain brought by the filter may not be enough for the loss of the splitter, so the OTDR equipment at the local office may not be able to receive to any information from branch fibers.

Contents of the invention

The invention provides a system and method for detecting fiber optic faults in passive optical networks, which are used to solve the faults of any branch optical fiber that can be detected and located by OTDR equipment at the bureau.

A system for detecting fiber faults in passive optical networks provided by an embodiment of the present invention includes: an optical path detection OTDR device, a wavelength division multiplexing coupler, a wavelength selective coupler, a branch fiber selector, and more than one optical splitter. Wavelength selective router; wavelength division multiplexing coupler is connected with OTDR equipment and optical line terminal, and connected with wavelength selective coupler through trunk fiber; wavelength selective coupler is connected with optical splitter and branch fiber selector; branch fiber selector is connected with each Each wavelength selection router is connected to each wavelength selection router through a corresponding branch fiber and an optical network unit.

The OTDR device is used to transmit the OTDR control signal and the OTDR detection signal for the corresponding branch fiber to the wavelength division multiplexing coupler, and determine the main fiber or the corresponding branch according to whether the reflected signal corresponding to the received OTDR detection signal is abnormal Whether there is a fault in the optical fiber;

The wavelength division multiplexing coupler is used to introduce the OTDR signal and the downlink signal of the optical line terminal to the trunk fiber, and the OTDR signal is the OTDR control signal or OTDR detection signal for the corresponding branch fiber; the reflected signal separated from the trunk fiber The signal is transmitted to the OTDR equipment, and the separated uplink signal is transmitted to the optical line terminal;

The wavelength selective coupler is used to separate a part of the OTDR signal from the trunk fiber and pass it to the branch fiber selector; pass the other part of the OTDR signal to the splitter; guide the received reflected signal of the branch fiber back to the trunk On the optical fiber, at the same time, the uplink signal of the optical network unit passing through the optical splitter is transmitted to the backbone optical fiber; and the downlink signal of the optical line terminal is transmitted to the optical splitter;

The branch fiber selector is used to control the bypass switch of the corresponding branch fiber according to the OTDR control signal when the OTDR signal is an OTDR control signal, and send the reflected signal of the corresponding branch fiber to the wavelength selective coupler;

The wavelength selection router is used to transmit the downlink signal from the splitter to the branch fiber; separate the reflected signal from the uplink signal of the branch fiber to the branch fiber selector, and pass the separated uplink signal to the splitter.

The wavelength division multiplexing coupler is an optical filter, which is used to couple the OTDR signal output by the OTDR device into the main fiber, and separate the reflected signal on the main fiber and transmit it to the OTDR device.

The wavelength selective coupler includes: a first optical filter, a branch coupler and a second optical filter, wherein,

The first optical filter is used to separate the OTDR signal from the trunk fiber and guide it to the branch coupler; couple the reflected signal from the branch fiber of the branch coupler back to the trunk fiber; couple the upstream signal from the second optical filter back to the trunk fiber;

The branch coupler is used to split the OTDR signal, guide a part of the OTDR signal to the second optical filter, and guide the other part of the OTDR signal to the branch fiber selector; and pass the reflected signal of the branch fiber to the first optical filter ;

The second optical filter is used to guide the received OTDR signal to the optical splitter; guide the uplink signal from the optical splitter to the first optical filter.

The branch fiber selector includes:

The optical circulator is used to import the OTDR signal to the optical detector; the reflected signal of the branch fiber is sent to the wavelength selective coupler;

An optical detector is used to convert the OTDR signal into an electrical signal, and transmit the electrical signal to the optical switch controller;

The optical switch controller is used to judge according to the electrical signal from the optical detector. If the electrical signal is a switch control signal converted from an OTDR control signal, the optical switch is triggered to perform switch control on the bypass switch of the corresponding branch optical fiber. action; if the electrical signal is a signal converted from an OTDR detection signal, no action is performed and it is in a pending state;

The optical switch is configured to switch and control the bypass switch of the corresponding branch optical fiber according to the switch control signal sent by the optical switch controller.

The wavelength selection router includes: a first optical circulator, a second optical circulator, and an optical filter, wherein,

The first optical circulator is used to guide the downlink signal to the second optical circulator, and guide the uplink signal to the optical splitter;

The optical filter is used to separate the reflected signal of the branch fiber from the upstream signal and guide it to the branch fiber selector; guide the separated upstream signal to the first optical circulator;

The second optical circulator is used to guide the downlink optical signal to the branch optical fiber, and guide the uplink optical signal to the optical filter.

The branch fiber selector is used to generate a control signal for turning on the bypass switch of the corresponding branch fiber according to the OTDR control signal when the OTDR control signal is an indication for indicating that the corresponding branch fiber is closed, and turn on the corresponding wavelength selection router.

The branch fiber selector is used to generate a control signal for disconnecting the bypass switch of the corresponding branch fiber according to the OTDR control signal when the OTDR control signal is an indication for indicating that the corresponding branch fiber is disconnected, and disconnect the corresponding wavelength Select a router.

The branch fiber selector also includes a power module, which is used to supply power to the photodetector, the photoswitch controller and the photoswitch.

The optical switch controller is further configured to, if the switch control signal corresponding to the electrical signal is a control signal for closing the optical switch, before triggering the optical switch to perform an action of switching and controlling the bypass switch of the corresponding branch optical fiber, instruct The power module executes the operation of turning on the power supply of the optical switch; if the switch control signal corresponding to the electrical signal is a control signal for turning off the optical switch, after the optical switch is triggered to perform the switching control action of the bypass switch of the corresponding branch optical fiber , instructing the power module to perform the operation of disconnecting the power supply of the optical switch;

The power supply module is used to supply power to the optical detector and the optical switch controller all the time; and to control the power supply to the optical switch according to the instruction of the optical switch controller.

The system of the embodiment of the present invention can monitor, detect and locate the faults of the backbone of the passive optical network and all branch fibers, and any branch fiber that needs to be detected can be selected through the optical switch, thus avoiding the problem of equal length branch fibers The signals overlap and cannot be distinguished. At the same time, let the reflected signal of the OTDR of the branch fiber bypass the optical splitter and return to the main fiber, thus avoiding the attenuation of the reflected signal by the optical splitter, especially the optical splitter with a large splitting ratio, and ensuring that the detector of the OTDR can receive the signal .

Description of drawings

FIG. 1 is a schematic structural diagram of an existing passive optical network;

Fig. 2 is a schematic structural diagram of an existing optical path detection passive optical network system;

3 is a schematic structural diagram of the optical path detection passive optical network system of the present invention;

Fig. 4 is the structural representation of the wavelength division multiplexing coupler of the present invention;

FIG. 5 is a schematic structural diagram of a wavelength selective coupler of the present invention;

Fig. 6 is a schematic structural view of a branch fiber selector of the present invention;

FIG. 7 is a schematic structural diagram of a wavelength selection router according to the present invention.

Detailed ways

3, the system of the embodiment of the present invention includes: OTDR equipment 31, wavelength division multiplexing coupler 32, wavelength selective coupler 33, branch fiber selector 34 and more than one wavelength selective router 35 connected to the optical splitter. Wherein, the wavelength division multiplexing coupler 32 is connected with the OTDR equipment 31 and the optical line terminal; is connected with the wavelength selective coupler 33 through the trunk optical fiber; the wavelength selective coupler 33 is connected with the optical splitter and the branch fiber selector 34; the branch fiber selector 34 is connected to each wavelength selection router 35; each wavelength selection router 35 is respectively connected to an optical network unit through a corresponding branch optical fiber.

The OTDR device 31 is used to transmit the OTDR control signal and the OTDR detection signal for the corresponding branch fiber to the wavelength division multiplexing coupler, and determine the trunk fiber and the corresponding branch according to whether the reflected signal corresponding to the OTDR detection signal is abnormal after analyzing Check whether the optical fiber is faulty.

Here, if the reflection signal is a Fresnel reflection signal or there is a sudden change in the Rayleigh reflection signal, it can be determined whether there is a fault in the main fiber or the corresponding branch fiber; if it is a continuous Rayleigh reflection signal, it can be determined that there is no failure in the main fiber or the corresponding branch fiber .

Wavelength division multiplexing coupler 32 is used to import the received OTDR signal and the downlink signal of the optical line terminal onto the trunk fiber, and the OTDR signal is an OTDR control signal or an OTDR detection signal for the corresponding branch fiber; The separated reflection signal is transmitted to the OTDR equipment, and the separated uplink signal is transmitted to the optical line terminal.

The wavelength selective coupler 33 is used to separate a part of the OTDR signal from the trunk fiber and pass it to the branch fiber selector; pass the other part of the OTDR signal to the splitter; guide the reflected signal of the received branch fiber back to On the trunk fiber, at the same time, the uplink signal of the optical network unit passing through the optical splitter is transmitted to the trunk fiber; at the same time, the downlink signal transmitted from the trunk fiber is transmitted to the optical splitter. However, in the embodiment of the present invention, the optical splitter transmits the received downlink signal to the corresponding wavelength selective router, and can also be used to transmit the received uplink signal to the wavelength selective coupler.

Branch fiber selector 34, used to control the bypass switch of the corresponding branch fiber according to the OTDR control signal when the OTDR signal is an OTDR control signal, and send the reflected signal of the corresponding branch fiber to the wavelength selective coupler ;

The wavelength selection router 35 is used to transmit the downlink signal from the splitter to the branch fiber; separate the reflected signal from the uplink signal of the branch fiber and send it to the branch fiber selector, and pass the separated uplink signal to the splitter.

The wavelength division multiplexing coupler 32 is located at the office OLT, and its purpose is to import and export OTDR signals without affecting normal services. Referring to Fig. 4, the WDM coupler can be composed of a thin film filter (TFF). The thin film filter all reflects light above 1625nm, but transmits all light below 1625nm. The connection between them is as follows, the P port is connected to the OLT, the C port is connected to the main optical fiber of the ODN, and the R port is connected to the OTDR equipment. The thin-film filter is used to guide the OTDR signal output by the OTDR device to the main fiber, and transmit the reflected signal on the main fiber to the OTDR device, while maintaining the normal uplink and downlink communication between the OLT and the ONU.

In the embodiment of the present invention, a wavelength selective coupler can be set at the entrance of the optical splitter, as shown in FIG. optical filter 52, wherein,

The first optical filter 51, it is a sideband filter, to the total reflection of light above 1625nm, the light total transmission of other wavelengths, the transmission port (P) of the first optical filter 51 and the second optical filter 52 The transmission port (P) is connected; the common port (C) of the first optical filter 51 is connected with the trunk fiber, and the reflection port (R) of the first optical filter 51 is connected with the branch coupler 53 interface. The first optical filter 51 is used to separate the OTDR signal from the trunk fiber and guide it to the branch coupler 53; the reflected signal from the branch fiber of the branch coupler 53 is coupled back in the trunk fiber; The uplink signal is coupled back into the backbone fiber.

Branch coupler (Tap Coupler) 53, is used for shunting OTDR signal, guides a part of OTDR signal to the R mouth of second optical filter 52, guides another part of OTDR signal to branch optical fiber selector, if OTDR signal is to control signal, then the branch fiber selector will execute relevant commands, such as requiring to select a certain branch fiber, etc.; and pass the reflected signal of the branch fiber to the first optical filter 51, so that the reflected signal of the branch fiber can pass through the branch coupler 53 and the first optical filter 51 lead back to the trunk fiber.

The second optical filter 52, it is a sideband filter, it is to the light total reflection above 1625nm, other light all transmits, and its transmission port (P) and the transmission port (P) of the first optical filter 51 Its common port (C) is connected with the optical splitter interface, and its reflection port (R) is connected with the branch coupler 53 main branch port. The second optical filter 52 is used to guide the received OTDR signal to the optical splitter; guide the uplink signal from the optical splitter to the first optical filter 51 . At the same time, ensure smooth uplink and downlink light, without splitting to the OTDR branch.

There is a branch fiber selector next to the optical splitter of the optical distribution network ODN. The branch fiber selector is an active device, which can be powered locally or by a battery. Of course, if the cost is not considered, remote use of light for power supply can be considered. In order to reduce power consumption as much as possible, it should be in the pending state when not detecting. Referring to FIG. 6 , the branch fiber selector 34 includes: an optical switch 61 , an optical circulator 62 , an optical detector 63 and an optical switch controller 64 .

The optical switch 61 is used to switch and control the bypass switch of the corresponding branch fiber according to the switch control signal sent by the optical switch controller, that is, select the branch fiber to be measured, and transmit the reflected signal of the branch fiber to the optical circulator .

The optical circulator 62 is used to guide the OTDR signal to the optical detector; to send the reflected signal of the branch fiber to the wavelength selective coupler. For example, when the OTDR signal is an OTDR control signal, the control signal for turning on the optical switch can be selected to connect or close the corresponding branch optical fiber.

The optical detector 63 is used to convert the OTDR signal into an electrical signal, and transmit the electrical signal to the optical switch controller.

The optical switch controller 64 is used to judge according to the electrical signal from the photodetector, if the electrical signal is a switch control signal converted from an OTDR control signal, trigger the optical switch to switch the bypass switch of the corresponding branch optical fiber The action of control; if the electrical signal is a signal converted from the OTDR detection signal, no action is performed and it is in a pending state.

It may further include: a power module, not shown in the figure, for supplying power to the photodetector, the photoswitch controller and the photoswitch.

The power module can always supply power to the photodetector, the photoswitch controller and the photoswitch. Of course, in order to save power, it can be used to supply power to the photodetector and the photoswitch controller all the time, but it is necessary to control the power supply to the photoswitch according to the instructions of the photoswitch controller. This requires the optical switch controller, which is further used to trigger the optical switch to perform switch control on the bypass switch of the corresponding branch optical fiber if the switch control signal corresponding to the electrical signal is a control signal for closing the corresponding optical switch. Before the action, instruct the power supply module to perform the operation of turning on the power supply of the optical switch; if the switch control signal corresponding to the electrical signal is the control signal to turn off the corresponding optical switch, then the bypass switch for the corresponding branch optical fiber is executed after triggering the optical switch After performing the switch control action, instruct the power module to perform the operation of disconnecting the optical switch power supply.

A wavelength selection router is connected before each branch fiber of the optical splitter. Referring to FIG. 7 , the wavelength selection router 35 includes: a first optical circulator 71 , a second optical circulator 72 and an optical filter 73 .

The first optical circulator 71 is used to guide the downlink signal to the second optical circulator 72, and guide the uplink signal to the optical splitter, that is, the downlink light passes through port 2 to port 3, and then reaches the branch through the second optical circulator 72 The optical fiber receives the uplink light transmitted through the thin film filter at port 1, and transmits the uplink light through port 2 to the optical splitter.

The optical filter 73 is a sideband filter, which is the same as the previous sideband filter. It reflects light above 1625nm and transmits the rest of the light, and is used to separate the reflected signal of the branch optical fiber from the upstream signal of the ONU. Separated and guided to the branch fiber selector; guided the separated uplink signal to the first optical circulator 71;

The second optical circulator 72 is used to guide the downlink optical signal to the branch optical fiber through the port 1 to the port 2 , and guide the uplink optical signal to the sideband filter 73 through the port 2 to the port 3 .

In the embodiment of the present invention, through the optical path detection system composed of the above series of auxiliary optical functional modules, an ordinary OTDR device can be used at the local office to intelligently and quickly detect and locate the fault of the main optical fiber and any branch optical fiber. Moreover, any branch fiber to be detected can be selected through the optical switch, thus avoiding signal overlap and indistinguishability of branch fibers with equal lengths. At the same time, let the reflected signal of the OTDR of the branch fiber bypass the optical splitter and return to the main fiber, thus avoiding the attenuation of the reflected signal by the optical splitter, especially the optical splitter with a large splitting ratio, and ensuring that the OTDR instrument can receive the signal.

Through the system of the embodiment of the present invention, the operator can be very effectively helped 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 fails, the operator can quickly detect, locate the fault, and perform maintenance on the branch fiber without affecting the normal services of other branch fibers. These will greatly reduce the operator's operation and maintenance costs.

The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and preferred embodiments. The following examples are only used to illustrate and explain the present invention, but not to limit the technical solution of the present invention.

In order to realize the intelligent detection of the optical fiber system of the passive optical network, some modifications are made to the passive optical network first, and some active and passive optical function modules are added. 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 backbone optical fiber, so that the OTDR signal can enter the passive optical network system, and the corresponding reflected signal can pass through The network is transmitted to the detector of the OTDR.

Insert a wavelength selective coupler before the splitter, its main function is to transmit the OTDR indication signal to the branch fiber selector, and transmit the reflected signal of the branch fiber back to the main fiber. At the same time, it ensures the normal communication of uplink and downlink signals and the passage of OTDR detection signals.

After the optical splitter, a wavelength selection router is inserted in front of each branch fiber. Its main function is to transmit the reflected signal of the branch fiber to the branch fiber selector, and at the same time, the uplink and downlink communication is running normally.

A branch fiber selector is placed next to the optical splitter, one end of which is connected to the wavelength selective coupler, and the other end is connected to each wavelength selective router. Its main function is to open the branch fiber selector according to the requirements of the OTDR, connect the bypass of the corresponding branch fiber, and close the bypass after the test is completed. Since the branch optical fiber selector is an active device, in order to meet the general power saving and environmental protection requirements in the industry, it is generally in a pending state when not testing, that is, only the optical detector and optical switch controller have induction power supply, and other parts have no power supply; When testing is required, first the OTDR control signal needs to issue an activation command, the optical switch controller commands to restore power supply, and all modules are powered normally, and the branch fiber selector is in an activated state at this time: then the OTDR control signal sends out relevant commands, and the optical switch The controller commands the relevant modules to perform relevant operations. At this time, the branch fiber selector is in the state of executing the command; when the task is completed, the OTDR control signal will issue a shutdown or pending instruction, and the optical switch controller commands to turn off the power supply of the relevant modules. At this time The branch fiber selector returns a status of Pending.

Specifically, the entire working process and state changes of the branch fiber selector are as follows: (1) When receiving the power-on command, the branch fiber selector switches from the pending state to the active state; (2) receiving the OTDR control signal to control the corresponding branch When the fiber is closed, the branch fiber selector commands to perform relevant actions to connect the optical link of the corresponding branch fiber; (3) when the OTDR detection signal is received, the branch fiber selector is in the testing state; (4) after the test is completed, The branch optical fiber selector receives the OTDR control signal to disconnect the power supply of the corresponding optical switch; (5) After executing the power disconnection command, it returns to the pending state.

When all these modules are connected according to Figure 3, the OTDR equipment can intelligently test the entire passive optical network system. The entire optical path detection process is described below.

When the passive optical network needs to be detected, first connect the OTDR equipment to the wavelength division multiplexing coupler at the local office, and then the OTDR sends signals to the branch fiber selector with light of 1625nm or above, and the light passes through the wavelength selective coupler The C port of the first optical filter to the branch B port of the branch coupler, then the optical circulator of the branch fiber selector reaches the optical detector PD, and the detector converts the optical signal into an electrical signal, and at the same time according to the requirements of the control signal Turn on the optical switch, and at the same time tell the optical switch to connect the optical path of the branch fiber to be detected. The optical switch connects the link of the branch fiber according to the requirements.

After waiting for a few seconds, the OTDR starts to emit test light pulses. The signal enters the trunk fiber through a wavelength division multiplexing coupler. At this time, the reflected signal of the main fiber is transmitted back to the detector of the OTDR through the main fiber. If there is any fault in the main fiber, OTDR will be able to find it quickly and locate it quickly. The OTDR signal arriving at the wavelength selective coupler is reflected from the C port of the first optical filter to the R port to reach the branch coupler, most of the OTDR signal is shunted to the second optical filter, and reaches the splitter through its C port , and then enter each branch fiber. First, it needs to go through each wavelength selection router, that is, through the first optical circulator and the second optical circulator, to reach each branch optical fiber, and then pass through each branch optical fiber to reach the ONU. At this time, the reflected signal of the branch fiber reaches the wavelength selection router through the branch fiber, and then is guided to the sideband filter through the second optical circulator, and enters the optical switch branch through reflection. If the branch has been connected, then the reflected signal will be led to the wavelength selective coupler through the optical switch path, and then through the branch coupler, the sideband filter returns to the main fiber. It is obvious that the signal has bypassed the optical splitter and is transmitted through the backbone optical fiber to the detector of the OTDR. If the branch is not connected, the signal will terminate its travel. So only one branch fiber can be measured at a time.

After the measurement, the OTDR re-transmits the closing signal, and reaches the branch fiber selector through the wavelength selective coupler, and the optical switch controller closes the optical switch according to the signal instruction. The entire branch fiber selector will be in a pending state of low energy consumption.

Now let's look at the communication between OLT and ONU during the detection process. See Figure 3. The first is the downlink optical link. The downlink light sent by the OLT is transmitted through the wavelength division multiplexing coupler, as shown in Figure 4, and then passes through the trunk fiber to the wavelength selective coupler, as shown in Figure 5, and then passes through the first optical filter and The second optical filter reaches the optical splitter, and the light split by the optical splitter reaches each wavelength selection router, as shown in Figure 7, passes through the first optical circulator and the second optical circulator to each branch fiber, and then passes through the branch fiber to reach the corresponding The ONU. The uplink optical link is the uplink light sent by the ONU, which passes through the branch fiber to the wavelength selection router, as shown in Figure 7. First, it passes through the second optical circulator to the sideband filter, and then passes through the sideband filter to the first optical ring line. through the first optical circulator to the optical splitter, through the optical splitter to the wavelength selective coupler, as shown in Figure 5, through the second optical filter and the first optical filter to the trunk fiber, through the trunk fiber to the wavelength division coupler The multiplexing coupler, as shown in Figure 4, reaches the OLT through the coupler. During the entire transmission process, the OTDR signal and reflected signal do not interfere with the downlink and uplink optical links.

During the entire process from the beginning to the closing of the optical path detection, the communication between the OLT and the ONU of the passive optical network remains unimpeded, that is, their services are not interrupted. If a branch fiber fails, users of other branch fibers will not be aware of it during the inspection and fault location by OTDR, subsequent repair and restoration of normal working status. This will greatly reduce the maintenance cost of the operator.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (9)

1. A system for detecting a passive optical network fiber failure, characterized in that it includes: optical path detection OTDR equipment, wavelength division multiplexing coupler, wavelength selective coupler, branch fiber selector and more than one connected to the optical splitter Wavelength selective router; wavelength division multiplexing coupler is connected with OTDR equipment and optical line terminal, and connected with wavelength selective coupler through trunk fiber; wavelength selective coupler is connected with optical splitter and branch fiber selector; branch fiber selector is connected with each Each wavelength selection router is connected to each wavelength selection router through a corresponding branch fiber and an optical network unit. The OTDR device is used to transmit the OTDR control signal and the OTDR detection signal for the corresponding branch fiber to the wavelength division multiplexing coupler, and determine the main fiber or the corresponding branch according to whether the reflected signal corresponding to the received OTDR detection signal is abnormal Whether there is a fault in the optical fiber; The wavelength division multiplexing coupler is used to introduce the OTDR signal and the downlink signal of the optical line terminal to the trunk fiber, and the OTDR signal is the OTDR control signal or OTDR detection signal for the corresponding branch fiber; the reflected signal separated from the trunk fiber The signal is transmitted to the OTDR equipment, and the separated uplink signal is transmitted to the optical line terminal; The wavelength selective coupler is used to separate a part of the OTDR signal from the trunk fiber and pass it to the branch fiber selector; pass the other part of the OTDR signal to the splitter; guide the received reflected signal of the branch fiber back to the trunk On the optical fiber, at the same time, the uplink signal of the optical network unit passing through the optical splitter is transmitted to the backbone optical fiber; and the downlink signal of the optical line terminal is transmitted to the optical splitter; The branch fiber selector is used to control the bypass switch of the corresponding branch fiber according to the OTDR control signal when the OTDR signal is an OTDR control signal, and send the reflected signal of the corresponding branch fiber to the wavelength selective coupler; The wavelength selection router is used to transmit the downlink signal from the splitter to the branch fiber; separate the reflected signal from the uplink signal of the branch fiber to the branch fiber selector, and pass the separated uplink signal to the splitter; The branch fiber selector includes: The optical circulator is used to import the OTDR signal to the optical detector; the reflected signal of the branch fiber is sent to the wavelength selective coupler; An optical detector is used to convert the OTDR signal into an electrical signal, and transmit the electrical signal to the optical switch controller; The optical switch controller is used to judge according to the electrical signal from the optical detector. If the electrical signal is a switch control signal converted from an OTDR control signal, the optical switch is triggered to perform switch control on the bypass switch of the corresponding branch optical fiber. action; if the electrical signal is a signal converted from an OTDR detection signal, no action is performed and it is in a pending state; The optical switch is configured to switch and control the bypass switch of the corresponding branch optical fiber according to the switch control signal sent by the optical switch controller. 2. The system according to claim 1, wherein the wavelength division multiplexing coupler is an optical filter, which is used to couple the OTDR signal output by the OTDR device into the backbone optical fiber, and the reflection on the backbone optical fiber After the signal is separated, it is sent to the OTDR equipment. 3. The system according to claim 1, wherein the wavelength selective coupler comprises: a first optical filter, a branch coupler and a second optical filter, wherein, The first optical filter is used to separate the OTDR signal from the trunk fiber and guide it to the branch coupler; couple the reflected signal from the branch fiber of the branch coupler back to the trunk fiber; couple the upstream signal from the second optical filter back to the trunk fiber; The branch coupler is used to split the OTDR signal, guide a part of the OTDR signal to the second optical filter, and guide the other part of the OTDR signal to the branch fiber selector; and pass the reflected signal of the branch fiber to the first optical filter ; The second optical filter is used to guide the received OTDR signal to the optical splitter; guide the uplink signal from the optical splitter to the first optical filter. 4. The system according to claim 1, wherein the wavelength selection router comprises: a first optical circulator, a second optical circulator and an optical filter, wherein, The first optical circulator is used to guide the downlink signal to the second optical circulator, and guide the uplink signal to the optical splitter; The optical filter is used to separate the reflected signal of the branch fiber from the upstream signal and guide it to the branch fiber selector; guide the separated upstream signal to the first optical circulator; The second optical circulator is used to guide the downlink optical signal to the branch optical fiber, and guide the uplink optical signal to the optical filter. 5. The system according to claim 1, wherein the branch fiber selector is configured to generate a corresponding branch according to the OTDR control signal when the OTDR control signal is an indication for indicating that the corresponding branch fiber is closed The control signal of the bypass switch of the optical fiber is connected to the corresponding wavelength selection router. 6. The system according to claim 1, wherein the branch fiber selector is used to generate a corresponding disconnection response according to the OTDR control signal when the OTDR control signal is an indication for indicating that the corresponding branch fiber is disconnected. The control signal of the bypass switch of the branch fiber disconnects the corresponding wavelength selection router. 7. The system according to claim 1, wherein the branch fiber selector further comprises a power supply module, configured to supply power to the optical detector, the optical switch controller and the optical switch. 8. The system according to claim 7, wherein the optical switch controller is further configured to trigger the optical switch to execute the corresponding switch control signal if the switch control signal corresponding to the electrical signal is a control signal for closing the optical switch. Before the bypass switch of the branch optical fiber performs the switch control action, instruct the power module to perform the operation of turning on the power supply of the optical switch; After the bypass switch of the branch optical fiber performs the switching control action, instruct the power module to perform the operation of disconnecting the optical switching power supply; The power supply module is used to supply power to the optical detector and the optical switch controller all the time; and to control the power supply to the optical switch according to the instruction of the optical switch controller. 9 . The system according to claim 1 , wherein the working states of the branch fiber selector include: activated state, connected state, test state, closed state and pending state.