WO2012024982A1

WO2012024982A1 - System and method for detecting fiber failure

Info

Publication number: WO2012024982A1
Application number: PCT/CN2011/076601
Authority: WO
Inventors: 徐继东; 贝劲松; 袁立权
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-08-25
Filing date: 2011-06-29
Publication date: 2012-03-01
Also published as: CN101924962B; CN101924962A

Abstract

A system and method for detecting fiber failure is provided in the present invention. By using an optical path detecting system composed of a series of assistant optical function modules, the system can use a tunable Optical Time Domain Reflectometer (OTDR) equipment at the office party quickly to detect and locate the failures of the backbone fiber and one of branch fibers, and detect the related branch fibers by selecting the optical path detecting signals with different wavelengths, so as to avoid the disadvantages that the signals of the branch fibers are too weak to be detected and the signals can not be distinguished because the signals of the branch fibers that are equal in length are superposed, thus expediently allowing operators to maintain passive optical network system, and reducing maintenance cost of the operators.

Description

TECHNICAL FIELD The present invention relates to the field of communications, and in particular to a system and method for fiber fault detection. BACKGROUND OF THE INVENTION Today, network technologies are rapidly developing, and network applications are becoming more and more popular, such as network communication, online shopping, and online entertainment, which have become part of modern life. The existing access network copper (wired) system can not meet the needs of such high speed and broadband, and Passive Optical Network (PON) is a high-speed, environmentally friendly and energy-saving broadband access technology. It is the best candidate to replace the existing access network. Passive optical networks are being accepted and deployed by most operators to meet the growing number of communications users and faster and better service needs. Passive optical network is a point-to-multipoint fiber access technology. Figure 1 is a block diagram of a prior art passive optical network. As shown in FIG. 1 , the passive optical network includes an Optical Line Terminal (OLT), an Optical Network Unit (ONU), and an Optical Distribution Network (ODN). In general, an optical passive network can be simplified as a point-to-multipoint structure in which an OLT connects multiple ONUs through an optical power splitter (referred to as a splitter) of the ODN. 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 optical fiber lines and the location of faults. In order to reduce the operation and maintenance costs, the operator wants to use an Optical Time Domain Reflectometer (OTDR) at the OLT to detect the main and branch fibers of the entire passive optical network. If a branch fiber fails, hope In the case of not affecting the services of other branch fibers, it is possible to quickly detect faults and locate and repair faults. When an OTDR device is used to detect such a point-to-multipoint network at the OLT of the central office, the signal of the primary kilo-fiber is generally not problematic, but the signals of the branched fiber will encounter the following problems: 1) If the optical splitter The splitting ratio is very large. At this time, the Rayleigh reflected signal of the branch fiber will have a large loss when passing through the splitter. When it reaches the OTDR detector, the signal is already submerged in the noise; 2) If part of the branch fiber is When the distances of the splitters are approximately equal, the OTDR device cannot distinguish which branch fiber is the signal unless a high resolution OTDR device is used. But the highest resolution that can be provided now is 2 meters. For example, for a 10 km ODN with a 1:32 split ratio, the loss of the splitter is 3*5+3=18 dB. 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. Assume that the optical path detection signal passes through the beam splitter to the end of the branch fiber and then totally reflects (ie, does not count the reflection loss) through the beam splitter to the OTDR detector. If other losses (such as connection loss, etc.) are not counted, then the optical path detection signal has the maximum optical path. The loss will be 2* 18+2*4.0 = 44 dB. This has exceeded the operating dynamic range of the OTDR equipment, so the signal of the branch fiber has been submerged in the noise, which indicates that the OTDR equipment traditionally used in the local office is unable to measure the fault of the branch fiber of the ODN with large split ratio. This phenomenon is more common. 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 equipment. The existing remedy is to add an optical filter in front of all ONUs. FIG. 2 is a schematic diagram of optical path fault detection using a prior art scheme of applying an optical filter to the ONU. This filter transmits all of the light below 1625 nm, but reflects the optical path detection light of 1625 nm or more. 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 or not, but it is still impossible to determine the exact position where the branch fiber fault occurs. If some of the branched fiber lengths are substantially equal, the reflected light overlaps, and even a high-resolution OTDR device cannot distinguish the difference. To make matters worse, for ODNs with large split ratios (eg: 1:128 split ratio), the gain from the filter may not be enough for the loss of the splitter, so the OTDR device in the office may not receive it. Any information from the branch fiber. In the process of implementing the present invention, the inventors have realized that the prior art has the following drawbacks: The optical path detection signal is largely depleted during the passive optical network failure test. SUMMARY OF THE INVENTION A primary object of the present invention is to provide a system and method for detecting fiber faults to solve the problem of large loss of optical path detection signals in the passive optical network fault test process. According to an aspect of the present invention, a fiber fault detection system is provided, including an OTDR device, a wavelength division multiplexing coupler, a wavelength selective combiner, a beam splitter, a wavelength selective router, and a second path module, wherein: an OTDR device, The optical path detection signal is set to generate fault detection, and the optical path detection signal is sent to the wavelength division multiplexing coupler; the wavelength division multiplexing coupler is connected to the OTDR device, and is set to introduce the optical path detection signal into the main kilometer fiber; a coupler, connected to the main kilo-fiber, configured to transmit the optical path detection signal to the optical splitter; the optical splitter, connected to the wavelength selective coupler, configured to transmit the optical path detection signal to the wavelength selective router; the wavelength selective router, and the optical splitter The device is connected to transmit the optical path detection signal to the corresponding branch fiber; and receive the optical path detection reflection signal of the branch fiber transmission, and send the optical path detection reflection signal to the second path module parallel to the optical splitter; the second path module , setting In order to transmit the optical path detection reflection signal to the wavelength selective combiner; the wavelength selective coupler is connected to the second path module, and is further configured to send the optical path detection reflection signal to the wavelength division multiplexing coupler through the main kilo fiber; The multiplex coupler is further configured to separate the optical path detection reflection signal from the main kilo fiber and transmit the optical path detection reflection signal to the OTDR device; the OTDR device is further configured to determine the main kilo fiber and/or according to the optical path detection reflection signal The fiber of the branch fiber is faulty. During this detection process, the normal communication between the OLT and the ONU remains unchanged. Preferably, in the technical solution, the OTDR device is a tunable OTDR device, configured to generate an optical path detection signal of a preset wavelength for the target branch fiber, and determine the failure of the primary and target branch fibers according to the optical path detection and reflection signal. The second path module includes an AWG, and the universal port of the AWG is connected to the wavelength selective coupler, and the branch channel of the AWG is connected to the target branch fiber through a corresponding wavelength selection router, and is configured to receive the optical path detection reflection signal of the branch fiber, and Sending to the wavelength selective coupler; the OTDR device is configured to determine the failure of the target branch fiber according to the state of the optical path detection reflected signal. Preferably, in the technical solution, the preset wavelength number of the optical path detection signal is equal to the number of branch fibers. Preferably, in the present technical solution, the AWG should select a device that is independent of ambient temperature, preferably a passive device. Preferably, in the technical solution, the wavelength division multiplexing coupler is located on the OLT side, and includes: a first thin film filter, a P port of the first thin film filter is connected to the optical line terminal OLT, and a C port is connected to the main kilo fiber, R The port is connected to the OTDR device; the first thin film filter reflects the light of the optical path detection, and transmits the light for the non-optical path detection. Preferably, in the technical solution, the wavelength selective coupler comprises a four-interface optical circulator and a second thin film filter, the interface 1 of the optical circulator is connected to the C interface of the second thin film filter, and the interface 2 and the main of the optical circulator The optical fiber is connected, the interface 3 of the optical circulator is connected to the optical splitter, the interface 4 of the optical circulator is connected to the P interface of the second thin film filter; the second thin film filter reflects the light of the optical path, and the optical path is non-optical The detected light is transmitted. Preferably, in the technical solution, the wavelength selective coupler comprises two three-interface optical circulators and a fourth thin film filter, and the interface 1 of the first optical circulator is connected to the C interface of the fourth thin film filter, and the first optical ring is connected. The interface 2 of the device is connected to the main kilofiber, the interface 2 of the second optical circulator is connected to the optical splitter, the interface 3 of the second optical circulator is connected to the P interface of the fourth thin film filter, and the interface 3 of the first optical circulator versus The interface 1 of the second optical circulator is connected; the fourth thin film filter reflects the light of the optical path detection, and transmits the light for the non-optical path detection. Preferably, in the technical solution, the wavelength selective router includes a four-interface optical circulator and a third thin film filter, and the interface 1 of the optical circulator is connected to the P interface of the third thin film filter, and the interface 2 and the optical splitter of the optical circulator The interface 3 of the optical circulator is connected to the branch fiber, and the interface 4 of the optical circulator is connected to the C interface of the third thin film filter; the third thin film filter reflects the light of the optical path detection, and the non-optical path detection Light is transmitted. Preferably, in the technical solution, the wavelength selective router includes two three-interface optical circulators and a fifth thin film filter, and the interface 1 of the first optical circulator is connected to the P interface of the fifth thin film filter, and the first optical circulator The interface 2 is connected to the optical splitter, the interface 2 of the second optical circulator is connected to the branch optical fiber, the interface 3 of the second optical circulator is connected to the C interface of the fifth thin film filter, and the interface 3 of the first optical circulator The interface 1 of the optical circulator of the second is connected; the fifth thin film filter reflects the light of the optical path detection, and transmits the light for the non-optical path detection. Preferably, in the technical solution, the wavelength division multiplexing coupler is located at the OLT. According to another aspect of the present invention, a method for optical fiber fault detection is provided, comprising: an optical path detection signal for generating an error detection by an OTDR device, transmitting an optical path detection signal to a wavelength division multiplexing coupler; and a wavelength division multiplexing coupler Introducing the optical path detection signal into the primary kilo-fiber; the wavelength selective combiner connected to the primary kilo-fiber transmits the optical path detection signal to the optical splitter; the optical splitter transmits the optical path detection signal to the wavelength selective router; and the wavelength selective router detects the optical path The signal is transmitted to the branch fiber corresponding thereto; and receives the optical path detection reflection signal of the branch fiber, transmits the optical path detection reflection signal to the second path module parallel to the optical splitter; and the second path module sends the optical path detection reflection signal to the wavelength Selecting a coupler; the wavelength selective coupler transmits the optical path detection reflection signal to the wavelength division multiplexing coupler through the main kilofiber; the wavelength division multiplexing coupler separates the optical path detection reflection signal from the main kilo fiber, and reflects the optical path detection The signal is sent to the OTDR device; the OTDR device determines the primary kilofiber and/or based on the optical path detection reflected signal The fiber of the branch fiber is faulty. Preferably, in the technical solution, the wavelength of the optical path detection signal is a preset wavelength corresponding to the target branch fiber; and the optical path detection reflected signal is sent to the wavelength selective coupler through the channel of the AWG of the second channel module for the target branch fiber. The OTDR device determines the fault of the target branch fiber based on the state of the optical path detection reflected signal. In the invention, the method for adding the second channel module provides an uplink channel for the optical path detection and reflection signal transmission without passing through the optical splitter, thereby reducing the loss of the reflected signal of the optical path detection, and ensuring the branch fiber of the OTDR device. Detection capability and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, In the drawings: FIG. 1 is a schematic structural diagram of a conventional passive optical network; FIG. 2 is a schematic diagram of an optical path fault detection using a scheme of a prior art optical filter applied to an ONU; FIG. FIG. 4 is a schematic diagram of a second channel module in a fiber fault detection system according to Embodiment 2 of the present invention; FIG. 5 is a schematic diagram of a second channel module according to the system embodiment of the present invention; FIG. 6 is a schematic diagram of a wavelength selective coupler in a three-fiber fault detection system according to an embodiment of the present invention; FIG. 7 is a third embodiment of the system according to the present invention. FIG. 8 is a schematic diagram of a wavelength selective router 1 in a three-fiber fault detection system according to an embodiment of the present invention; FIG. 9 is a third embodiment of a system according to the present invention. Schematic diagram of a wavelength selection router 2 in a fault detection system; FIG. 10 is a flowchart of a fiber fault detection method according to an embodiment of the method of the present invention BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. System Embodiment 1 FIG. 3 is a schematic diagram of a fiber fault detection system according to an embodiment of the system of the present invention. It should be noted that, in FIG. 3, the two-way arrow between the optical line terminal and the wavelength division multiplexing filter indicates the communication signal interaction between the two, and the communication signal interaction of other parts is not given; The arrows only indicate the flow direction of the optical path detection signal. As shown in FIG. 3, the system provided in this embodiment includes an OTDR device, a wavelength division multiplexing coupler, a wavelength selective coupler, a beam splitter, a wavelength selection router, and a second path module. The OTDR device is configured to generate an optical path detection signal for fault detection, and send an optical path detection signal to the wavelength division multiplexing coupler; the wavelength division multiplexing coupler is located at the local OLT, and is connected to the OTDR device, and is set to be The optical path detection signal is introduced into the main kilo-fiber; the wavelength selective coupler is connected to the main kilo-fiber, and is configured to transmit the optical path detection signal to the optical splitter; the optical splitter is connected to the wavelength selective coupler, and is configured to transmit the optical path detection signal To the wavelength selection router; the wavelength selection router is connected to the optical splitter, and is configured to transmit the optical path detection signal to the corresponding branch fiber; and receive the optical path detection reflection signal of the branch fiber, and send the optical path detection reflection signal to the optical splitter a parallel second path module; a second path module configured to transmit the optical path detection reflection signal to the wavelength selective coupler; a wavelength selection combiner connected to the second channel module, and configured to pass the optical path detection reflection signal through the main Thousands of optical fibers are sent to the WDM coupler; the WDM coupler is also set to be from the main thousand Defibrillation detecting the reflected signal light path, the optical path and detecting the reflected signal to the OTDR device; OTDR apparatus, further arranged to fiber backbones and / or branched optical fiber for faults detected reflected signal analysis path determination. Since the optical splitter is the main source of loss during the transmission of the optical path detection signal (optical path detection reflected signal), the optical splitter is also the object that needs to be detected in the fiber failure detection. In this embodiment, the optical path detection signal passes through the optical splitter in the downlink path; and in the uplink path, the optical path detection reflected signal does not pass through the optical splitter, but passes through the second path disposed in parallel with the optical splitter, thereby being to a certain extent The loss of the optical path detection reflected signal is reduced, the accuracy of the fiber fault detection is improved, and the accuracy requirement of the detection process for the OTDR device is reduced. System Embodiment 2: In the prior art, in addition to the high optical path detection signal loss, there is an exact position where the fiber failure cannot be confirmed, and if the length of the partial branch fibers is substantially equal, the reflected light overlaps even if It is a high-resolution OTDR device that cannot distinguish the difference between each branch fiber. As shown in FIG. 3, in this embodiment, the OTDR device is a tunable OTDR device, and is configured to generate an optical path detection signal of a preset wavelength for the target branch fiber, and determine the reflected signal according to the optical path detection signal corresponding to the optical path detection signal. The fault of the target branch fiber; the second path module includes an Arrayed Waveguide Grating (AWG), the universal port of the AWG is connected to the wavelength selective coupler, and the branch channel of the AWG is connected to the target branch fiber through the corresponding wavelength selection router. , set to receive the optical path detection reflection signal of the wavelength selection router, and send it to the wavelength selection combiner. For the sake of understanding, the second channel module will be described in detail below. 4 is a schematic diagram of a second channel module in a fiber fault detection system according to a second embodiment of the system of the present invention. As shown in Figure 4, the second channel module is composed of AWG. In order to make the second channel module truly passive, its AWG must be independent of the ambient temperature, that is, the ambient temperature changes such as -20 ° C 70 ° C The AWG operating parameters and performance have no effect, otherwise the AWG needs a temperature control device to keep its operation stable, which will increase the working cost and maintenance difficulty, so the passive AWG is more suitable than the active AWG in this embodiment. However, those skilled in the art should understand that an active AWG should be able to achieve the same effect as long as the corresponding temperature control device is provided, that is, in the second channel module, including the AWG (active AWG). Temperature control equipment that stabilizes the working environment, in conjunction with the use of active AWGs, should also be within the scope of the present invention. Therefore, the passive working characteristics of the AWG are very important. The choice of the operating wavelength range of the AWG is related to the tuning range of the tunable OTDR equipment used by the customer. In order to reduce the work of the PON, the wavelength must be chosen to avoid the upstream and downstream wavelength bands, according to ITU-T. The wavelength of the optical path detection of L.66 is usually specified in the U-band, that is, 1625nm - 1675nm. If necessary, the C-band can be selected, that is, 1525nm - 1565nm, as long as it does not overlap with its upstream and downstream wavelengths. However, the filters and tunable OTDR devices are also adjusted accordingly. The channel spacing of the AWG is typically 100 GHz, and an AWG of 50 GHz spacing can be selected as needed. The number of channels should be selected corresponding to the splitter number of the splitter. For example, the ODN of the split ratio of 1:32 is matched with 32 channels of AWG. The basic working principle is that different wavelengths of light travel in different channels in the AWG, and the channels are connected to the branch fiber through the wavelength selection router, so that the branch fiber is identified by the optical wavelength of the optical path detection, that is, optical path detection of different wavelengths. The signal can only detect its corresponding branch fiber. When a branch fiber is detected, the AWG channel corresponding to the branch fiber has a smaller loss equivalent to the turn-on, and the other channel has a loss that is too close to the turn-off. In this embodiment, by the fault signal, it can be known which position of the optical fiber has failed. In this embodiment, the optical path detecting system composed of the above series of auxiliary optical function modules can quickly detect and locate the faults of the main kilofiber and any one branch fiber by using a tunable OTDR device in the office. And detecting branch light associated with it by selecting optical path detection signals of different wavelengths Fiber, thus avoiding the attenuation of the optical fiber path detection reflection signal of the branch fiber by the optical splitter, and the overlapping of the signals of the equal length branch fiber, which cannot be distinguished, thereby facilitating the user's maintenance and repair of the system. System Embodiment 3: In this embodiment, a specific scenario is performed on the light fault detection system in combination with a specific scenario. As shown in FIG. 3, the light failure detecting system of this embodiment includes: a tunable OTDR device, a wavelength division multiplexing coupler, a wavelength selector, a second channel module, and one or more wavelength selective routers connected to the optical splitter. Wherein the wavelength division multiplexing coupler is connected to the OTDR device and the optical line terminal; the main kilo fiber is connected to the wavelength selective coupler; the wavelength selective coupler is connected to the optical splitter and the second channel module; the second channel module and each wavelength Selecting a router to connect; each wavelength selection router is connected to the optical splitter, and is respectively connected to the optical network unit through the corresponding branch optical fiber. The tunable OTDR device is configured to transmit a detection signal for optical path detection of a specific wavelength of the corresponding branch fiber to the wavelength division multiplexing coupler, and determine the main kilo fiber and corresponding according to whether the received optical path detection reflection signal is abnormal 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 whether the main kilo fiber or the corresponding branch fiber has a fault. If it is a continuous Rayleigh reflected signal, it can be determined that the main kilo fiber or the corresponding branch fiber does not have error occured. The wavelength division multiplexing coupler is configured to introduce the optical path detection signal and the downlink signal of the optical line terminal to the main kilometer fiber, and transmit the optical path detection reflection signal separated on the main kilo fiber to the OTDR device, and separate the signal The outgoing uplink signal is transmitted to the optical line terminal OLT. The wavelength division multiplexing coupler is located at the local OLT to import and export optical path detection signals without affecting normal services. Figure 5 is a schematic illustration of a wavelength division multiplexing coupler in a three fiber fault detection system in accordance with an embodiment of the present invention. As shown in Figure 5, the wavelength division multiplexing coupler can be composed of a Thin Film Filter (TFF). The thin film filter reflects the wavelength of the optical path detection, but transmits the light for the non-optical path detection. For example, the following edge filter can be selected, which reflects the light above 1625 nm and the light below 1625 nm. Light is transmitted. The connections between them are as follows. The P port is connected to the OLT, the C port is connected to the main kilofiber, and the R port is connected to the OTDR device. The thin film filter is configured to introduce an optical path detection signal output by the OTDR device to the primary kilo-fiber, and transmit the optical path detection reflection signal to the OTDR device while maintaining normal uplink and downlink communication between the OLT and the ONU. The wavelength selective coupler is configured to transmit the downstream light to the optical splitter; and combine the received optical path detection reflected signal from the second channel module with the uplink signal passing through the optical splitter, and then lead back to the primary optical fiber. In this embodiment, a wavelength selective coupler is provided at the entrance of the beam splitter. The wavelength selective coupler can consist of a four-interface optical circulator and a thin film filter (TFF). Figure 6 is a schematic illustration of a wavelength selective coupler 1 in a three fiber fault detection system in accordance with an embodiment of the present invention. Referring to Figure 6, the optical circulator has four interfaces, wherein the interface 1 is the light inlet, that is, the light can only enter and exit; the interface 2 is the light inlet and outlet, that is, the light enters from the interface 1, and the interface 2 Output, and the light coming in from interface 2 can only go to interface 3; interface 3 is the light inlet and outlet, that is, the light from interface 2 can be output from interface 3, and the light coming in from interface 3 can only be connected to the interface. 4; interface 4 is the light exit, that is, the light can only be out; and the thin film filter reflects the wavelength of the optical path detection, but transmits the light for non-optical detection, such as: Generally, it can be used. An edge filter that reflects light above 1625 nm and transmits light below 1625 nm. The connection between them is as follows. The interface 1 of the optical circulator is connected to the C interface of the filter, the interface 2 of the optical circulator is connected to the main 1000 fiber, the interface 3 of the optical circulator is connected to the optical splitter, and the interface 4 of the optical circulator Connected to the P interface of the filter. The main function of the coupler is to direct the optical path detection and reflection signal from the second channel module back to the main kilofiber, while maintaining the normal uplink and downlink communication between the OLT and the ONU. In this embodiment, the wavelength selector can also be composed of two three-interface optical circulators and a thin film filter. Figure 7 is a schematic diagram of a wavelength selective coupler 2 in a three-fiber fault detection system according to an embodiment of the present invention. Referring to FIG. 7, the first optical circulator and the second optical circulator have three interfaces, wherein the interface 1 is an optical inlet, that is, the light can only enter and exit; the interface 2 is an optical import and export, that is, light. From the interface 1, it can be output from the interface 2, and the light coming in from the interface 2 can only go to the interface 3; the interface 3 is the light exit, that is, the light from the interface 2 can be output from the interface 3; As shown in FIG. 7, the interface 3 of the first optical circulator is connected to the interface 1 of the second optical circulator, and the main kilofiber is connected to the interface 2 of the first optical circulator, and the C interface and the first optical ring of the optical filter are connected. The interface 1 of the second optical circulator is connected to the optical splitter, the interface 3 of the second optical circulator is connected to the interface P of the optical filter, and the second channel module is connected to the R interface of the thin film filter. A second channel module is arranged to send an optical path detection reflected signal from the branch fiber of the wavelength selective router to the wavelength selective coupler. The second channel module is located in the optical distribution network ODN to form a parallel path with the optical splitter, and the second channel module is a passive device. Referring to Figure 4, the second channel module is composed of (AWG). In order for the second channel module to be truly passive, the AWG must be independent of the ambient temperature, that is, the ambient temperature changes, such as -20 °C-- 70 °C has no effect on AWG operating parameters and performance, or set a temperature control Equipment to keep the AWG work stable, of course, this will increase the cost of work and maintenance, so the choice of AWG with passive operating characteristics is a preferred implementation. The choice of the operating wavelength range of the AWG is related to the tuning range of the tunable OTDR equipment used by the customer. In order to reduce the interference to the PON operation, the wavelength must be avoided by the upstream and downstream wavelength bands, according to ITU-T L.66. The optical path detection wavelength is usually specified in the U band, that is, 1625 nm to 1675 nm. . If necessary, you can also choose the C-band, which is 1525nm - 1565nm, as long as it does not overlap with its upstream and downstream wavelengths. However, filters and tunable OTDR devices should also be adjusted accordingly. The channel spacing of the AWG is typically 100 GHz, and an AWG of 50 GHz spacing can be selected as needed. The number of channels should be selected corresponding to the number of splits of the splitter. For example, the ODN of the split ratio of 1:32 should be matched with 32 channels of AWG. The basic working principle is that different wavelengths of light travel in different channels in the AWG, and the channels are connected to the branch fiber through the wavelength selection router, so that the branch fiber is identified by the optical wavelength of the optical path detection, that is, optical path detection of different wavelengths. The signal can only detect its corresponding branch fiber. a wavelength selection router, located at each branch fiber front end of the optical splitter, configured to transmit a downlink signal from the optical splitter to the branch optical fiber; and separating the optical path detection reflected signal from the uplink signal of the branch optical fiber to the branch optical fiber selector, and The separated upstream signal is led back to the splitter. The wavelength selective router can consist of a four-interface optical circulator and a thin film filter (TFF). Figure 8 is a schematic diagram of a wavelength selective router 1 in a three-fiber fault detection system in accordance with an embodiment of the present invention. Referring to Figure 8, the optical circulator has four interfaces, wherein the interface 1 is the light inlet, that is, the light can only enter and exit; the interface 2 is the light inlet and outlet, that is, the light enters from the interface 1, and the interface 2 Output, and the light coming in from interface 2 can only go to interface 3; interface 3 is the light inlet and outlet, that is, the light from interface 2 can be output from interface 3, and the light coming in from interface 3 can only be connected to the interface. 4; interface 4 is the light exit, that is, the light can only be out; and the thin film filter reflects the wavelength of the optical path detection, but transmits the light for non-optical detection, such as: Generally, it can be used. An edge filter that reflects light above 1625 nm and transmits light below 1625 nm. The connection between them is as follows, the interface 1 of the optical circulator is connected to the P interface of the filter, the interface 2 of the optical circulator is connected to the optical splitter, the interface 3 of the optical circulator is connected to the branch optical fiber, and the interface 4 of the optical circulator is The C interface of the filter is connected. The main function of the coupler is to separate the optical path detection and reflection signal from the downstream light to the second channel module, and maintain the normal uplink and downlink communication between the OLT and the ONU. In this embodiment, the wavelength selective router may also be composed of two three-interface optical circulators and a thin film filter. Figure 9 is a schematic diagram of a wavelength selective router 2 in a three-fiber fault detection system according to an embodiment of the present invention. Referring to FIG. 9, the first optical circulator and the second optical circulator have three interfaces, wherein the interface 1 is an optical inlet, that is, the light can only enter and exit; the interface 2 is an optical import and export. That is, light enters from interface 1 and can be output from interface 2, and light coming in from interface 2 can only go to interface 3; interface 3 is the exit of light, that is, light from interface 2, which can be output from interface 3; The connection is shown in Figure 9. The interface 3 of the first optical circulator is connected to the interface 1 of the second optical circulator, the optical splitter is connected to the interface 2 of the first optical circulator, and the P interface of the thin film filter is connected to the interface 1 of the first optical circulator. The interface 2 of the second optical circulator is connected to the branch fiber, the interface 3 of the second optical circulator is connected to the interface C of the thin film filter, and the interface P of the thin film filter is connected to the second channel module. In this embodiment, through the optical path detecting system composed of the above series of auxiliary optical function modules, a tunable OTDR device can be used in the office to intelligently and quickly detect and locate the faults of the main kilofiber and any one branch fiber. Moreover, by selecting the optical path detection signals of different wavelengths to detect the branch fibers associated with them, the signal overlap of the equal length branch fibers is avoided and cannot be distinguished. At the same time, the optical path detection reflection signal bypasses the optical splitter and returns to the main kilometer fiber, which reduces the attenuation of the optical path detection signal by the optical splitter, and ensures that the OTDR device can receive the reflected signal. Through the system of the embodiment, the operator can be very effectively helped to quickly find the location of the fiber fault, which will greatly shorten the maintenance time and reduce the maintenance cost. In particular, when a branch fiber fails, the operator can quickly detect and locate the fiber and perform maintenance without affecting the normal service of other branch fibers. These will greatly reduce the operator's operating and maintenance costs. Method Embodiment 1 FIG. 10 is a flowchart of a method for detecting a fiber fault according to an embodiment of the method of the present invention. As shown in FIG. 10, the embodiment includes: Step S1002: The OTDR device generates an optical path detection signal for fault detection, and sends an optical path detection signal to the wavelength division multiplexing coupler; wherein, the OTDR device can be tuned to generate a target branch Optical path detection signal of a predetermined wavelength of the optical fiber. Step S1004, the wavelength division multiplexing coupler introduces the optical path detection signal into the main kilofiber; step S1006, the wavelength selective coupler connected to the main kilo fiber transmits the optical path detection signal to the optical splitter; step S1008, the optical splitter Transmitting the optical path detection signal to the wavelength selective router; Step S1010: The wavelength selection router transmits the optical path detection signal to the branch fiber corresponding thereto, and receives the optical path detection reflection signal corresponding to the optical path detection signal transmitted by the branch optical fiber, and sends the optical path detection reflection signal to be parallel with the optical splitter. a second path module; step S1012, the second path module sends the optical path detection reflection signal to the wavelength selective combiner; and in step S1014, the wavelength selection combiner transmits the optical path detection reflection signal to the wavelength division multiplexing through the primary kilofiber a coupler; step S 1016, the wavelength division multiplexing coupler separates the optical path detection reflection signal from the main kilo fiber, and transmits the optical path detection reflection signal to the OTDR device; Step S1018, the OTDR device determines the main according to the optical path detection reflection signal Fiber failure of a thousand fiber or branch fiber. The device implemented in this embodiment is the first embodiment of the system, and has all the beneficial effects of the embodiment, and will not be repeated here. Method Embodiment 2: This embodiment will further describe the fiber fault detection method based on the first embodiment of the method. In this embodiment, the wavelength of the optical path detection signal is a preset wavelength corresponding to the target branch fiber; the optical path detection reflected signal is sent to the wavelength selective combiner through the channel of the AWG of the second channel module for the target branch fiber; the OTDR device The failure of the target branch fiber is determined according to the state of the optical path detection reflected signal. The device implemented in this embodiment is the second embodiment of the system, and has all the beneficial effects of the embodiment, and is not repeated in J3⁄4. Method Embodiment 3: This embodiment will further describe the fiber fault detection method based on Embodiments 1 and 2. When the passive optical network needs to be detected, the OTDR device is first connected to the WDM coupler, and then the corresponding optical path detection wavelength is selected for a required measurement branch fiber, and the OTDR device detects The wavelength of the signal is adjusted to this wavelength, and the wavelength range is generally between 1625 and 1675 nm, or between 1525 nm and 1565 nm in the C-band, as long as the upstream and downstream wavelengths are avoided. What needs to be explained here is the relationship between the grating interface of the AWG and the branch fiber after the placement of the second channel module is completed. It is fixed, and different grating interfaces correspond to different wavelengths in and out. Therefore, the branch fiber is identified by the optical wavelength, and the corresponding wavelength is required for the detection of different branch fibers. 4 to 8, when the OTDR device adjusts the wavelength corresponding to the branch fiber to be measured, and then sends a detection signal with the wavelength, the R interface of the wavelength division multiplexing filter connected to the OTDR device is integrated into the main kilo fiber. For transmission, the reflected signal returns the original path to the OTDR device. If there is any fault in the main kilofiber, its abnormal signal will be quickly discovered by the OTDR device and can be quickly located. If there is no problem with the main kilofiber, the optical path detection signal will be transmitted to the wavelength selective coupler. As shown in Fig. 6, the optical path detection signal will be output from the interface 2 of the four-interface optical circulator to the optical splitter, and will be split. After reaching each wavelength selection router, as shown in Fig. 8, the optical path detection signal will be output from the interface 2 of the optical circulator 2 to the branch fiber, and transmitted to the ONU connected thereto, and the optical path detection of the branch fiber is performed. The reflected signal is output from the interface 3 of the optical circulator of the wavelength selection router to the interface 4 of the optical filter, and enters the C interface of the filter. After being separated, it is output from the R interface of the filter and enters the grating port of the AWG of the second channel module, and the common AWG is output. The port enters the C interface of the R interface of the filter of the wavelength selective combiner connected thereto, enters the interface 1 of the interface 1 of the four-interface optical circulator, reaches the main 1000 fiber, and reaches the wavelength division multiplexing filter by the transmission of the main kilo fiber. The C interface of the device is then separated and returned from its R interface output to the OTDR device, so each time the OTDR device will display a primary kilo fiber plus a branch light The reflected signal of the fiber. If the other steps of the branch fiber are to be detected, the optical wavelength of the optical path detection is adjusted to the wavelength corresponding to the branch fiber, and then the detection signal is sent, and the OTDR device will receive the reflected signal, and it can be judged according to whether the signal is abnormal or not. Whether it is faulty and locate the fault. Repeat the above steps until the end of the measurement. The communication process between the OLT and the ONU during the detection process is described in detail below, as shown in Figure 3. The first is the downstream optical link. The OLT emits the downstream light, which is transmitted through the wavelength division multiplexing coupler. See Figure 5, passing through the main kilofiber to the wavelength selective coupler, see Figure 6, and then through its optical circulator interface. 2 Outlet interface 3, reaching the optical splitter, passing through the splitter to reach each wavelength selection router, as shown in Fig. 8, passing through the interface 2 of the optical circulator 2 to reach each branch fiber, and then reaching the corresponding fiber through the branch fiber ONU. 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 8. First, it enters the interface C of the optical circulator through the interface 3 of the optical circulator, and enters the C interface of the filter. Then enter the interface 1 of the optical circulator, the output interface 2, reaches the optical splitter, passes through the optical splitter to reach the wavelength selective combiner, as shown in Fig. 6, through the interface 3 of the optical circulator, the interface 4 enters the filter P The interface exits the C interface and enters the interface 1 of the optical circulator. It reaches the main 1000 fiber and passes through the main kilofiber to the WDM coupler. See Figure 5, through the coupler to the OLT. The optical path detection signal and the reflected signal do not have any interference with the downlink and uplink optical links throughout the transmission. The wavelength selector and the wavelength selective router of this embodiment are each constituted by a four-interface optical circulator and a thin film filter. In addition, the wavelength selective coupler and the wavelength selective router implementing the technical solution may also be composed of two three-interface optical circulators and a thin film filter. Referring to FIG. 7 , FIG. 9 and the related description of the third embodiment of the system, the optical path is defined. The flow of the detection signal is similar to this and will not be repeated here. During the entire optical path detection from start to shutdown, 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 users of other branch fibers will not be aware of the detection and fault location by the OTDR device, and the subsequent repair and recovery of the normal working state. This will greatly reduce the cost of the operator's maintenance. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A fiber fault detection system, comprising an optical path detection OTDR device, a wavelength division multiplexing coupler, a wavelength selective combiner, a beam splitter, a wavelength selection router, and a second path module, wherein: the OTDR device is set to Generating an optical path detection signal for fault detection, transmitting the optical path detection signal to the wavelength division multiplexing coupler;

The wavelength division multiplexing coupler is connected to the OTDR device and configured to introduce the optical path detection signal into the primary kilo-fiber;

The wavelength selective coupler is connected to the main kilofiber, and is configured to transmit the optical path detection signal to the optical splitter;

The optical splitter is coupled to the wavelength selective coupler and configured to transmit the optical path detection signal to the wavelength selective router;

The wavelength selection router is connected to the optical splitter, and configured to transmit the optical path detection signal to a corresponding branch optical fiber; and receive an optical path detection reflection signal transmitted by the branch optical fiber, and send the optical path detection reflection Signaling to the second path module in parallel with the beam splitter;

The second path module is configured to send the optical path detection reflection signal to the wavelength selective coupler;

The wavelength selective coupler is connected to the second path module, and is further configured to send the optical path detection reflection signal to the wavelength division multiplexing coupler through the main kilofiber;

The wavelength division multiplexing coupler is further configured to separate an optical path detection reflection signal from the main kilofiber, and send the optical path detection reflection signal to an OTDR device;

The OTDR device is further configured to determine a fiber failure of the primary and/or branch fibers according to the optical path detection reflected signal.

2. The system of claim 1 wherein

The OTDR device is a tunable OTDR device, configured to generate an optical path detection signal of a preset wavelength for the target branch fiber, and determine, according to the optical path detection reflection signal, the failure of the primary kilo fiber or the target branch fiber. ; The second path module includes an arrayed waveguide grating AWG, the universal port of the AWG is connected to the wavelength selective coupler, and the branch channel of the AWG is connected to the target branch fiber through a corresponding wavelength selection router, the AWG Arranging to receive an optical path detection reflected signal of the branch fiber and transmitting it to the wavelength selective combiner;

The OTDR device is configured to determine a fault of the target branch fiber according to a state of the optical path detection reflected signal.

3. The system according to claim 2, wherein

The predetermined number of wavelengths of the optical path detection signal is equal to the number of the branch fibers.

4. The system of claim 2, wherein

The AWG is independent of ambient temperature.

The system of claim 1, wherein the wavelength division multiplexing coupler is located on the OLT side, and includes: a first thin film filter,

The P port of the first thin film filter is connected to the optical line terminal OLT, the C port is connected to the main kilo fiber, and the R port is connected to the OTDR device;

The first thin film filter reflects light of the optical path detection, and transmits light of the non-optical path detection.

6. The system of claim 1, wherein the wavelength selector comprises a four interface optical circulator and a second thin film filter,

The interface 1 of the optical circulator is connected to the C interface of the second thin film filter, the interface 2 of the optical circulator is connected to the main optical fiber, and the interface 3 of the optical circulator is connected to the optical splitter, and the optical ring is connected. The interface 4 of the device is connected to the P interface of the second thin film filter;

The second thin film filter reflects light of the optical path detection, and transmits light of the non-optical path detection.

7. The system of claim 1, wherein the wavelength selector comprises two three interface optical circulators and a fourth thin film filter,

An interface 1 of the first optical circulator is connected to a C interface of the fourth thin film filter, an interface 2 of the first optical circulator is connected to the main optical fiber, and an interface 2 of the second optical circulator is a splitter connection, an interface 3 of the second optical circulator and the fourth thin film filter The P interface is connected, and the interface 3 of the first optical circulator is connected to the interface 1 of the second optical circulator;

The fourth thin film filter reflects light of the optical path detection, and transmits light of the non-optical path detection.

8. The system of claim 1, wherein the wavelength selective router comprises a four interface optical circulator and a third thin film filter,

The interface 1 of the optical circulator is connected to the P interface of the third thin film filter, the interface 2 of the optical circulator is connected to the optical splitter, and the interface 3 of the optical circulator is connected to the branch optical fiber, the optical ring The interface 4 of the row is connected to the C interface of the third thin film filter;

The third thin film filter reflects light of the optical path detection, and transmits light of the non-optical path detection.

9. The system of claim 1, wherein the wavelength selective router comprises two three interface optical circulators and a fifth thin film filter,

The interface 1 of the first optical circulator is connected to the P interface of the fifth thin film filter, the interface 2 of the first optical circulator is connected to the optical splitter, and the interface 2 and the branch of the second optical circulator The optical fiber is connected to the interface of the second optical circulator, and the interface 3 of the first optical circulator is connected to the interface 1 of the second optical circulator;

The fifth thin film filter reflects the light of the optical path detection, and transmits the light for the non-optical path detection.

The system according to any one of claims 1-9, wherein the wavelength division multiplexing coupler is located at the OLT.

11. A method of fiber fault detection, comprising:

Optical path detection The OTDR device generates an optical path detection signal for fault detection, and transmits the optical path detection signal to the wavelength division multiplexing coupler;

The wavelength division multiplexing coupler directs the optical path detection signal into a primary kilo-fiber; a wavelength selective coupler coupled to the primary kilo-fiber transmits the optical path detection signal to a beam splitter;

The optical splitter transmits the optical path detection signal to a wavelength selective router; The wavelength selection router transmits the optical path detection signal to a branch fiber corresponding thereto; and receives an optical path detection reflection signal of the branch fiber, and sends the optical path detection reflection signal to a parallel with the optical splitter a second path module; the second path module sends the optical path detection reflection signal to the wavelength selective combiner;

The wavelength selective coupler transmits the optical path detection reflected signal to the wavelength division multiplexing coupler through the main kilofiber;

The wavelength division multiplexing coupler separates an optical path detection reflection signal from the main kilofiber, and transmits the optical path detection reflection signal to an OTDR device;

The OTDR device determines the fiber failure of the primary and/or branch fibers based on the optical path detection reflected signal.

12. The method according to claim 11, wherein

The wavelength of the optical path detection signal is a preset wavelength corresponding to the target branch fiber; the optical path detection reflected signal is sent to the wavelength selection by a channel of the AWG of the second channel module for the target branch fiber Coupler

The OTDR device determines a failure of the target branch fiber according to a state of the optical path detection reflected signal.