CN101924962A - System and method for optical fiber fault detection - Google Patents

Abstract

The invention discloses a system and a method thereof for detecting fiber faults. The system is an optical path detection system comprising a series of auxiliary optical function modules, and can quickly detect and position the faults of a backbone fiber and one of branch fibers through tunable OTDR equipment in a local place. Besides, the system can detect related branch fibers through selecting optical path detection signals with different wave lengths. Thus, the system can avoid the faults that the signals of a branch fiber are too weak to be detected and signals of branch fibers with identical wave length are overlapped and can not be distinguished, thereby being convenient for the maintenance of a passive optical network for operators, and lowering the maintenance cost.

Description

System and method for optical fiber fault detection

technical field

The invention relates to the technical field of passive optical networks in the communication industry, in particular to a system and method for optical fiber fault detection.

Background technique

Today, with the rapid development of network technology, network applications are gradually becoming popular, such as network communication, network shopping, and network entertainment, which have become a part of modern people's life. The existing access network copper wire (wired) system has been far from meeting this high-speed and broadband demand. The Passive Optical Network (PON) is a broadband and high-speed, environmentally friendly and energy-saving broadband access technology, and is the best candidate to replace the existing access network. Passive optical networks are being accepted and deployed by most operators to meet the increasing communication users and demand for faster and better services.

Passive optical network is a point-to-multipoint optical fiber access technology. FIG. 1 is a structural diagram of a passive optical network in the prior art. As shown in Figure 1. Passive optical network includes Optical Line Terminal (OLT for short), Optical Network Unit (ONU for short) and Optical Distribution Network (ODN for short). Usually, an optical passive network is simplified as a point-to-multipoint structure in which an OLT connects multiple ONUs through an ODN optical power splitter (optical splitter for short).

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 Time Domain Reflectometer (OTDR) at the OLT to detect the backbone and branch fibers of the entire passive optical network. In the case of affecting the business of other branch optical fibers, the fault can be quickly found, located and repaired.

When an OTDR device is used to detect this point-to-multipoint network at the office OLT, the signal of the main fiber will generally not have any problems, but the signals of the branch fibers will encounter the following problems: 1) If the optical splitter The splitting ratio is very large. At this time, the Rayleigh reflection signal of the branch fiber will have a large loss when it passes through the splitter. When it reaches the detector of the OTDR, the signal has been submerged in the noise; When the distance between the optical fiber and the optical fiber is approximately equal, the OTDR equipment cannot tell which branch optical fiber signal it is, unless a high-resolution OTDR equipment is used. But the highest resolution available now is 2 meters.

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 0.40*10=4.0dB. Generally, the maximum dynamic range of OTDR equipment is about 40dB. For example, the optical path detection signal reaches the end of the branch fiber through the optical splitter, and then the total reflection (that is, regardless of the reflection loss) passes through the optical splitter to the detector of the OTDR. If other losses (such as connection loss, etc.) are not considered, the maximum optical path loss of the optical path detection signal at this time will be 2*18+2*4.0=44dB. 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 PONs with a small splitting ratio, the reflected signal of the branch fiber cannot be seen with ordinary OTDR equipment.

The existing remedy is to add an optical filter before all ONUs. FIG. 2 is a schematic diagram of optical path fault detection using a scheme of adding an optical filter in front of an ONU in the prior art. The filter transmits all the light below 1625nm, but reflects the optical path detection 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.

In the process of realizing the present invention, the inventor realized that the prior art has the following defects: the loss of the optical path detection signal is relatively large during the fault test of the passive optical network.

Contents of the invention

The main purpose of the present invention is to provide a system and method for optical fiber fault detection, so as to solve the above-mentioned problem of large loss of optical path detection signals during passive optical network fault testing.

According to one aspect of the present invention, a system for optical fiber fault detection is provided, including an optical path detection OTDR device, a wavelength division multiplexing coupler, a wavelength selective coupler, an optical splitter, a wavelength selective router, and a second path module, wherein: The OTDR equipment is used to generate the optical path detection signal for fault detection, and sends the optical path detection signal to the wavelength division multiplexing coupler; the wavelength division multiplexing coupler is connected to the OTDR equipment, and is used to guide the optical path detection signal into the main fiber; The wavelength selective coupler is connected with the trunk optical fiber for transmitting the optical path detection signal to the optical splitter; the optical splitter is connected with the wavelength selective coupler for transmitting the optical path detection signal to the wavelength selective router; the wavelength selective router is used for transmitting the optical path detection signal to the wavelength selective router. The optical splitter connection is used to transmit the optical path detection signal to the corresponding branch optical fiber; and receive the optical path detection reflection signal transmitted by the branch optical fiber, and send the optical path detection reflection signal to the second channel module parallel to the optical splitter; the second channel The module is used 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 also used to send the optical path detection reflection signal to the wavelength division multiplexing coupler through the trunk optical fiber; The wavelength division multiplexing coupler is also used to separate the optical path detection reflection signal from the trunk fiber, and sends the optical path detection reflection signal to the OTDR device; the OTDR device is also used to judge the trunk fiber and/or The fiber fault of the branch fiber, during this detection process, the normal communication between the OLT and the ONU remains unchanged.

Preferably, in this technical solution, the OTDR device is a tunable OTDR device, which is used to generate an optical path detection signal for a preset wavelength of the target branch fiber, and judge the failure of the trunk fiber and the target branch fiber according to the optical path detection reflection signal; The second channel module includes an arrayed waveguide grating AWG. The general port of the AWG is connected to the wavelength selective coupler. The branch channel of the AWG is connected to the target branch fiber through the corresponding wavelength selection router, and is used to receive the optical path detection reflection signal of the branch fiber. And send it to the wavelength selective coupler; OTDR equipment is used to judge the fault of the target branch optical fiber according to the optical path detection reflection signal.

Preferably, in this technical solution, the number of preset wavelengths of the optical path detection signal is equal to the number of branch fibers; the AWG has nothing to do with the ambient temperature, or the second channel module also includes: a temperature control device for maintaining the stability of the AWG working environment.

According to another aspect of the present invention, a method for detecting an optical fiber fault is provided, including: an OTDR device generates an optical path detection signal for fault detection, and sends the optical path detection signal to a wavelength division multiplexing coupler; the wavelength division multiplexing coupler The optical path detection signal is introduced into the trunk fiber; the wavelength selective coupler connected with the trunk fiber transmits the optical path detection signal to the optical splitter; the optical splitter transmits the optical path detection signal to the wavelength selection router; the wavelength selection router transmits the optical path detection signal to the branch fiber corresponding to it; and receive the optical path detection reflection signal of the branch fiber, and send the optical path detection reflection signal to the second path module parallel to the optical splitter; the second path module sends the optical path detection reflection signal to the wavelength selective coupling The wavelength selective coupler sends the optical path detection reflection signal to the wavelength division multiplexing coupler through the trunk fiber; the wavelength division multiplexing coupler separates the optical path detection reflection signal from the trunk fiber, and sends the optical path detection reflection signal to the OTDR Equipment; OTDR equipment judges the fiber fault of the trunk fiber and/or branch fiber according to the optical path detection reflection signal.

In the present invention, the method of adding the second channel module is adopted to provide an uplink channel that does not pass through the optical splitter for the transmission of the optical path detection reflected signal, thereby reducing the loss of the reflected signal of the optical path detection, and ensuring the OTDR equipment to the branch optical fiber. Detection capability and accuracy.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

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

Fig. 2 is the schematic diagram that prior art adopts the scheme that adds optical filter before ONU to carry out optical path fault detection;

3 is a schematic diagram of an optical fiber fault detection system according to a system embodiment of the present invention;

4 is a schematic diagram of a second channel module in the optical fiber fault detection system according to the second embodiment of the system of the present invention;

5 is a schematic diagram of a wavelength division multiplexing coupler in a three-fiber fiber fault detection system according to a system embodiment of the present invention;

6 is a schematic diagram of wavelength selective coupler 1 in the optical fiber fault detection system according to the system embodiment 3 of the present invention;

7 is a schematic diagram of a second wavelength selective coupler in the optical fiber fault detection system according to the third embodiment of the system of the present invention;

8 is a schematic diagram of a wavelength selection router 1 in the optical fiber fault detection system according to the system embodiment 3 of the present invention;

9 is a schematic diagram of a second wavelength selection router in the optical fiber fault detection system according to the third embodiment of the system of the present invention;

Fig. 10 is a flow chart of a method for detecting an optical fiber fault according to a method embodiment of the present invention.

Detailed ways

Hereinafter, the present invention will be described in detail with reference to the drawings and examples. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

System embodiment one:

FIG. 3 is a schematic diagram of an optical fiber fault detection system according to a system embodiment of the present invention. It should be noted that, in FIG. 3 , the bidirectional arrow between the optical line terminal and the wavelength division multiplexing filter indicates the communication signal interaction between the two, while the communication signal interaction of other parts is not shown. Each small unidirectional arrow only indicates the flow direction of the optical path detection signal. As shown in FIG. 3 , this embodiment includes an OTDR device, a wavelength division multiplexing coupler, a wavelength selective coupler, an optical splitter, a wavelength selective router, and a second path module. Among them, the OTDR equipment is used to generate the optical path detection signal for fault detection, and sends the optical path detection signal to the wavelength division multiplexing coupler; the wavelength division multiplexing coupler is located at the office OLT and is connected to the OTDR equipment for The optical path detection signal is introduced into the trunk fiber; the wavelength selective coupler is connected with the trunk fiber for transmitting the optical path detection signal to the optical splitter; the optical splitter is connected with the wavelength selective coupler for transmitting the optical path detection signal to the wavelength Selection router; wavelength selection router, connected to the optical splitter, used to transmit the optical path detection signal to the corresponding branch optical fiber; and receive the optical path detection reflection signal of the branch optical fiber, and send the optical path detection reflection signal to the optical path detection reflection signal parallel to the optical splitter The second channel module; the second channel module is used to send the reflection signal of the optical distance detection to the wavelength selective coupler; the wavelength selective coupler is connected to the second channel module and is also used to send the reflection signal of the optical distance detection through the trunk optical fiber To the wavelength division multiplexing coupler; the wavelength division multiplexing coupler is also used to separate the optical path detection reflection signal from the main fiber, and sends the optical path detection reflection signal to the OTDR equipment; the OTDR equipment is also used for optical path detection Reflected signal analysis determines whether the trunk fiber and/or branch fiber is faulty.

Because in the transmission process of the optical path detection signal (optical path detection reflection signal), the optical splitter is the main source of loss, and the optical splitter is also an object that needs to be mainly detected in the optical fiber fault detection. In this embodiment, the downlink path passes through the optical splitter; while in the uplink path, instead of passing through the optical splitter, it passes through the second path arranged in parallel with the optical splitter, thereby reducing the optical path detection reflection signal to a certain extent The loss improves the accuracy of optical fiber fault detection and reduces the accuracy requirements of the detection process for OTDR equipment.

System embodiment two:

In the prior art, in addition to the high loss of the optical path detection signal, the exact location of the optical fiber fault cannot be confirmed. Moreover, 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 between each branch fiber.

As shown in Figure 3, in this embodiment, the OTDR device is a tunable OTDR device, which is used to generate an optical path detection signal with a preset wavelength for the target branch fiber, and judge according to the optical path detection reflection signal corresponding to the optical path detection signal The fault of the target branch fiber; the second channel module includes an arrayed waveguide grating AWG, the general port of the AWG is connected to the wavelength selective coupler, the branch channel of the AWG is connected to the target branch fiber through the corresponding wavelength selection router, and is used to receive the wavelength selection router The reflected signal is detected by the optical path and sent to the wavelength selective coupler.

For the convenience of understanding, the second channel module will be described in detail below. Fig. 4 is a schematic diagram of a second channel module in the optical fiber fault detection system according to the second embodiment of the system of the present invention. As shown in Figure 4, the second channel module is composed of arrayed waveguide grating AWG. In order to make the second channel module truly passive, its AWG must have nothing to do with the ambient temperature, that is, the ambient temperature changes such as -20℃- -70°C has no effect on AWG working parameters and performance, otherwise AWG needs a temperature control device to keep its work stable, which will increase work cost and maintenance difficulty, so the passive working characteristics of AWG are very important. The selection of AWG's working wavelength range is related to the tuning range of the tunable OTDR equipment used by customers. In order to reduce the interference to PON work, its wavelength must avoid the uplink and downlink wavelength bands. According to ITU-T L.66 optical Generally, its operating wavelength range is in the U-band, that is, 1625-1675nm. If necessary, its wavelength range can be extended to 1600--1700nm. But filters and tunable OTDR equipment should be adjusted accordingly. The channel spacing of AWG is generally 100GHz, and AWG with a spacing of 50GHz can also be selected according to needs. The selection of the number of channels should correspond to the splitting number of the optical splitter. For example, the ODN with a splitting ratio of 1:32 should be equipped with an AWG with 32 channels. The basic working principle is that different wavelengths of light go through 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 marked by the optical wavelength of the optical path detection, that is, the optical path detection of different wavelengths A signal can only detect its corresponding branch fiber. When testing a certain branch fiber, the loss of the AWG channel corresponding to the branch fiber is small, which is equivalent to opening, and when the loss of other channels is too large, it is equivalent to closing. In this embodiment, it can be known which segment of the optical fiber is faulty based on the location of the faulty signal.

In this embodiment, through the optical path detection system composed of the above series of auxiliary optical functional modules, a tunable OTDR device can be used at the office to quickly detect and locate the fault of the main fiber and any branch fiber. And by selecting the optical path detection signals of different wavelengths to detect the branch fibers related to it, this avoids the attenuation of the optical splitter to the branch fiber optical path detection reflection signal, and the signal overlap of the branch fibers with equal lengths cannot be distinguished, which is convenient. User maintenance and repair of the system.

System embodiment three:

In this embodiment, specific scenarios will be implemented for the optical fault detection system in combination with specific scenarios.

As shown in FIG. 3 , the optical fault detection system of this embodiment includes: a tunable OTDR device, a wavelength division multiplexing coupler, a wavelength selective coupler, a second channel module, and more than one wavelength selective router connected to the optical splitter. Among them, the wavelength division multiplexing coupler is connected with the OTDR equipment and the optical line terminal; it is connected with the wavelength selective coupler through the trunk fiber; the wavelength selective coupler is connected with the optical splitter and the second channel module; the second channel module is connected with each wavelength selection The routers are connected; each wavelength selection router is connected with the optical splitter, and is respectively connected with the optical network unit through the corresponding branch optical fiber.

The tunable OTDR equipment is used to transmit the detection signal of the optical path detection for the specific wavelength of the corresponding branch fiber to the wavelength division multiplexing coupler, and determine the main fiber and the corresponding branch according to the analysis of whether the received optical path detection reflection signal is abnormal 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 .

The wavelength division multiplexing coupler is used to introduce the optical path detection signal and the downlink signal of the optical line terminal to the trunk fiber, and transmit the optical path detection reflection signal separated from the trunk fiber to the OTDR device, and the separated The uplink signal is transmitted to the optical line terminal OLT.

The wavelength division multiplexing coupler is located at the office OLT, and its purpose is to import and export the optical path detection signal without affecting the normal business. FIG. 5 is a schematic diagram of a wavelength division multiplexing coupler in a three-fiber fiber fault detection system according to a system embodiment of the present invention. Referring to Fig. 5, the wavelength division multiplexing coupler can be composed of a thin film filter (TFF, Thin Film Filter). The thin film filter all reflects light above 1625nm (the wavelength of optical path detection), 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, and the R port is connected to the OTDR equipment. The thin-film filter is used to introduce the optical path detection signal output by the OTDR equipment to the main fiber, and transmit the optical path detection reflection signal to the OTDR equipment, while maintaining the normal uplink and downlink communication between the OLT and the ONU.

The wavelength selective coupler is used to transmit the downlink light to the optical splitter; and combine the received optical path detection reflection signal from the second channel module with the uplink signal passing through the optical splitter, and guide it back to the main optical fiber. In this embodiment, a wavelength selective coupler is provided at the entrance of the optical splitter.

The wavelength selective coupler can be composed of a four-port optical circulator and a thin film filter (TFF). FIG. 6 is a schematic diagram of wavelength selective coupler 1 in the optical fiber fault detection system according to system embodiment 3 of the present invention. As shown in Figure 6, the optical circulator has four interfaces, among which interface 1 is the entrance of light, that is, light can only enter but not exit; interface 2 is the entrance and exit of light, that is, light enters through interface 1, and can enter from output, and the light coming in from port 2 can only go to port 3; port 3 is the import and export of light, that is, the light coming from port 2 can be output from port 3, while the light coming in from port 3 can only go to the port 4; interface 4 is the exit of light, that is, light can only go out but not in; and the film filter reflects light above 1625nm (the wavelength of optical path detection), but transmits light below 1625nm. The connection between them is as follows, the interface 1 of the optical circulator is connected with the C interface of the filter, the interface 2 of the optical circulator is connected with the trunk fiber, the interface 3 of the optical circulator is connected with the splitter, and the interface 4 of the optical circulator is connected with The P interface of the filter is connected. The main function of the coupler is to guide the reflection signal of the optical path detection from the second channel module back to the main optical fiber, and at the same time maintain the normal uplink and downlink communication between the OLT and the ONU.

In this embodiment, the wavelength selective coupler may also be composed of two three-port optical circulators and a thin film filter. 7 is a schematic diagram of a second wavelength selective coupler in the optical fiber fault detection system according to the third embodiment of the system of the present invention. Referring to Fig. 7, the first optical circulator and the second optical circulator have three interfaces, wherein interface 1 is the entrance of light, that is, light can only enter but not exit; interface 2 is the entrance and exit of light, that is, light Entering from interface 1, it can be output from interface 2, and the light coming in from interface 2 can only go to interface 3; interface 3 is the output of light, that is, the light coming from interface 2 can be output from interface 3; the connection is as follows As shown in Figure 7, the interface 3 of the first optical circulator is connected to the interface 1 of the second optical circulator, the trunk fiber is connected to the interface 2 of the first optical circulator, and the C interface of the optical filter is connected to the first optical circulator The interface 1 of the second optical circulator is connected with the optical splitter, the interface 3 of the second optical circulator is connected with the interface P of the optical filter, and the second channel module is connected with the R interface of the thin film filter.

The second channel module is used to send the optical path detection reflection signal from the branch fiber of the wavelength selection router to the wavelength selection coupler.

The second channel module is located in the optical distribution network ODN to form a path parallel to the optical splitter, and the second channel module is a passive device. 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 have nothing to do with the ambient temperature, that is, the ambient temperature changes such as -20°C-70°C ℃ has no effect on AWG working parameters and performance, otherwise AWG needs a temperature control device to keep its work stable, which will increase work cost and maintenance difficulty, so the passive working characteristics of AWG are very important. The selection of AWG's working wavelength range is related to the tuning range of the tunable OTDR equipment used by customers. In order to reduce the interference to PON work, its wavelength must avoid the uplink and downlink wavelength bands. According to ITU-T L.66 optical Generally, its operating wavelength range is in the U-band, that is, 1625-1675nm. If necessary, its wavelength range can be extended to 1600--1700nm. But filters and tunable OTDR equipment should be adjusted accordingly. The channel spacing of AWG is generally 100GHz, and AWG with a spacing of 50GHz can also be selected according to needs. The selection of the number of channels should correspond to the splitting number of the optical splitter. For example, the ODN with a splitting ratio of 1:32 should be equipped with an AWG with 32 channels. The basic working principle is that different wavelengths of light go through 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 marked by the optical wavelength of the optical path detection, that is, the optical path detection of different wavelengths A signal can only detect its corresponding branch fiber.

A wavelength selection router, located at the front end of each branch fiber of the optical splitter, is used to transmit the downstream signal from the optical splitter to the branch fiber; and separate the optical path detection reflection signal from the upstream signal of the branch fiber to the branch fiber selector, and Guide the separated upstream signal back to the optical splitter.

A wavelength selective router may consist of a four-port optical circulator and a thin film filter (TFF). FIG. 8 is a schematic diagram of wavelength selection router 1 in the optical fiber fault detection system according to the system embodiment 3 of the present invention. As shown in Figure 8, the optical circulator has four interfaces, among which interface 1 is the entrance of light, that is, light can only enter but not exit; interface 2 is the entrance and exit of light, that is, light enters through interface 1, and can enter from output, and the light coming in from port 2 can only go to port 3; port 3 is the import and export of light, that is, the light coming from port 2 can be output from port 3, while the light coming in from port 3 can only go to the port 4; interface 4 is the exit of light, that is, light can only go out but not in; and the film filter reflects light above 1625nm (the wavelength of the optical path detection signal), but transmits light below 1625nm. The connection between them is as follows, the interface 1 of the optical circulator is connected with the P interface of the filter, the interface 2 of the optical circulator is connected with the optical splitter, the interface 3 of the optical circulator is connected with the branch optical fiber, the interface 4 of the optical circulator is connected with The C interface of the filter is connected. The main function of the coupler is to separate the optical path detection reflection signal from the downlink light and direct it to the second channel module, while maintaining the normal uplink and downlink communication between the OLT and the ONU.

In this embodiment, the wavelength selection router may also be composed of two three-interface optical circulators and a thin film filter. FIG. 9 is a schematic diagram of a second wavelength selection router in the optical fiber fault detection system according to the third embodiment of the system of the present invention. Referring to Fig. 9, the first optical circulator and the second optical circulator have three interfaces, wherein interface 1 is the entrance of light, that is, light can only enter but not exit; interface 2 is the entrance and exit of light, that is, light Entering from interface 1, it can output through interface 2, and the light coming in from interface 2 can only go to interface 3; interface 3 is the output of light, that is, the light coming from interface 2 can be output through interface 3;

Its connections are shown in Figure 9. Wherein the interface 3 of the first optical circulator is connected with the interface 1 of the second optical circulator, the optical splitter is connected with the interface 2 of the first optical circulator, and the P interface of the thin film filter is connected with the interface 1 of the first optical circulator, 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 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 detection system composed of the above series of auxiliary optical functional modules, a tunable OTDR device can be used at the office to intelligently and quickly detect and locate the fault of the main fiber and any branch fiber. Moreover, by selecting optical path detection signals of different wavelengths to detect the branch fibers related to it, it is avoided that the signals of branch fibers with equal length overlap and cannot be distinguished. At the same time, let the optical path detection reflection signal bypass the optical splitter and return to the main fiber, which reduces the attenuation of the optical path detection signal by the optical splitter and ensures that the OTDR equipment can receive its reflection signal.

Through the system of this embodiment, it is very effective to help the operator to quickly find the location of the optical fiber fault, which will greatly shorten the repair 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.

Method embodiment one:

Fig. 10 is a flow chart of a method for detecting an optical fiber fault according to a method embodiment of the present invention. As shown in Figure 10, this embodiment includes:

Step S 1002, the OTDR device generates an optical path detection signal for fault detection, and sends the optical path detection signal to the wavelength division multiplexing coupler;

Wherein, the OTDR device can be tuned to generate an optical path detection signal of a preset wavelength for the target branch fiber.

Step S1004, the wavelength division multiplexing coupler guides the optical path detection signal into the trunk optical fiber;

Step S1006, the wavelength selective coupler connected to the trunk optical fiber transmits the optical path detection signal to the optical splitter;

Step S1008, the optical splitter transmits the optical path detection signal to the wavelength selection router;

Step S1010, the wavelength selection router transmits the optical path detection signal to the corresponding branch fiber; and receives the optical path detection reflection signal corresponding to the optical path detection signal transmitted by the branch fiber, and sends the optical path detection reflection signal to the first optical path detection signal parallel to the optical splitter Two-channel module;

Step S1012, the second path module sends the optical path detection reflection signal to the wavelength selective coupler;

Step S1014, the wavelength selective coupler sends the optical path detection reflection signal to the wavelength division multiplexing coupler through the trunk optical fiber;

Step S1016, the wavelength division multiplexing coupler separates the optical path detection reflection signal from the trunk fiber, and sends the optical path detection reflection signal to the OTDR device;

Step S1018, the OTDR device judges the fiber fault of the trunk fiber or the branch fiber according to the optical path detection reflection signal.

The device implemented in this embodiment is the first system embodiment, and has all the beneficial effects of this embodiment, which will not be repeated here.

Method embodiment two:

This embodiment will further describe the optical fiber fault detection method on the basis of the first method embodiment.

In this embodiment, the wavelength of the optical path detection signal is the preset wavelength corresponding to the target branch fiber; the optical path detection reflection signal is sent to the wavelength selective coupler through the channel of the AWG of the second channel module for the target branch fiber; OTDR equipment The fault of the target branch optical fiber is judged according to the optical path detection reflection signal.

The equipment implemented in this embodiment is the second embodiment of the system, and has all the beneficial effects of this embodiment, which will not be repeated here.

Method embodiment three:

This embodiment will further describe the optical fiber fault detection method on the basis of the first and second embodiments.

When the passive optical network needs to be tested, first connect the OTDR equipment to the wavelength division multiplexing coupler at the local office, and then select the corresponding optical path detection wavelength for a required measurement branch fiber, and the OTDR equipment will detect The wavelength of the signal is tuned to this wavelength, and its wavelength range is generally between 1625-1675nm. What needs to be explained here is that after the installation of the second channel module is completed, the relationship between the AWG grating interface and the branch fiber is fixed, and different grating interfaces correspond to different wavelengths in and out, so the branch fiber is controlled by the optical wavelength. To identify different branch optical fibers, you need to select their corresponding wavelengths for detection.

Referring to Figures 4 to 8, when the OTDR equipment is adjusted to the wavelength corresponding to the branch fiber to be measured, then use this wavelength to send a detection signal, which is coupled into the trunk fiber through the R interface of the wavelength division multiplexing filter connected to the OTDR equipment. Transmission, the reflected signal will return to the OTDR equipment in the original way, if there is any fault in the main fiber, the abnormal signal will be quickly found by the OTDR equipment, and can be quickly located. If there is no problem with the trunk fiber, the optical path detection signal will be transmitted to the wavelength selective coupler. As shown in Figure 6, the optical path detection signal will go from interface 2 of the four-port optical circulator to interface 3, enter the optical splitter, and be split Reach each wavelength selection router, as shown in Figure 8, the optical path detection signal will exit the interface 3 from the interface 2 of the optical circulator, enter the branch fiber, and reach the ONU connected to it after transmission, the optical path detection reflection of the branch fiber The signal exits interface 4 from interface 3 of the optical circulator of the wavelength selection router, enters the C interface of the filter, is separated and outputs from the R interface of the filter, enters the grating port of the AWG of the second channel module, and exits the general port of the AWG Enter the R interface of the filter of the wavelength selective coupler connected to it, exit the C interface, enter the interface 1 of the four-interface optical circulator and exit the interface 2, reach the trunk fiber, and reach the C of the wavelength division multiplexing filter through the transmission of the trunk fiber. The interface is then separated from its R interface output and returned to the OTDR device, so each time the OTDR device will show a reflected signal of a trunk fiber plus a branch fiber. If you want to detect other branch optical fibers, repeat the above steps, that is, adjust the optical wavelength of the optical path detection to the wavelength corresponding to the branch optical fiber, and then send out a detection signal, and the OTDR equipment will receive the reflected signal, and judge according to whether the signal is abnormal Whether it is faulty and locate the fault. Repeat the above steps until the end of the measurement.

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 5, and then passes through the trunk fiber to the wavelength selective coupler, as shown in Figure 6, and then passes through the interface 2 of its optical circulator The output interface 3 reaches the optical splitter, and the light split by the optical splitter reaches each wavelength selection router, as shown in Figure 8, through the interface 2 of the optical circulator, the output interface 3 reaches each branch fiber, and then reaches the corresponding ONU through the branch fiber . 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 8. First, it passes through the interface 3 of the optical circulator and exits the interface 4, and enters the C interface of the filter and exits the P interface. It enters the interface 1 of its optical circulator and exits interface 2, reaches the optical splitter, passes through the optical splitter and reaches the wavelength selection coupler, as shown in Figure 6, passes through the interface 3 of its optical circulator and exits interface 4, and enters the P The interface exits the C interface, and then enters the optical circulator's interface 1 and exits the interface 2, reaches the trunk fiber, passes through the trunk fiber to the wavelength division multiplexing coupler, see Figure 5, and reaches the OLT through the coupler. During the whole transmission process, the optical distance detection signal and the reflected signal do not interfere with the downlink and uplink optical links.

Both the wavelength selective coupler and the wavelength selective router in this embodiment are composed of four-interface optical circulators and thin film filters. In addition, the wavelength selective coupler and the wavelength selective router for realizing this technical solution may also be composed of two optical circulators with three interfaces and a thin-film filter. Referring to FIG. 7, FIG. The flow direction of the detection signal is similar to this and will not be repeated here.

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 detection and fault location with OTDR equipment, subsequent repairs and restoration of normal working conditions. This will greatly reduce the maintenance cost of the operator.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (12)

1. a system of optical fiber fault detection, it is characterized in that, comprises optical path detection OTDR equipment, wavelength division multiplexing coupler, wavelength selection coupler, optical splitter, wavelength selection router, the second path module, wherein: The OTDR device is used to generate an optical path detection signal for fault detection, and send the optical path detection signal to the wavelength division multiplexing coupler; The wavelength division multiplexing coupler is connected with the OTDR device, and is used to introduce the optical path detection signal into the trunk optical fiber; The wavelength selective coupler is connected to the trunk optical fiber, and is used to transmit the optical path detection signal to the optical splitter; The optical splitter, connected to the wavelength selective coupler, is used to transmit the optical path detection signal to the wavelength selective router; The wavelength selection router is connected to the optical splitter, and is used to transmit the optical path detection signal to the corresponding branch optical fiber; and receive the optical path detection reflection signal transmitted by the branch optical fiber, and send the optical path detection reflection signal a signal to the second path module in parallel with the 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 also used to send the optical path detection reflection signal to the wavelength division multiplexing coupler through the trunk optical fiber; The wavelength division multiplexing coupler is also used to separate the optical path detection reflection signal from the trunk fiber, and send the optical path detection reflection signal to the OTDR device; The OTDR device is further configured to judge the fiber fault of the trunk fiber and/or the branch fiber according to the optical path detection reflection signal. 2. The system of claim 1, wherein: The OTDR device is a tunable OTDR device, which is used to generate an optical path detection signal for a preset wavelength of the target branch fiber, and judge the fault of the trunk fiber or the target branch fiber according to the optical path detection reflection signal; The second access module includes an arrayed waveguide grating AWG, the common port of the AWG is connected to the wavelength selective coupler, the branch channel of the AWG is connected to the target branch optical fiber through a corresponding wavelength selective router, and the The AWG is used to receive the optical path detection reflection signal of the branch fiber, and send it to the wavelength selective coupler; The OTDR device is configured to judge the fault of the target branch optical fiber according to the optical path detection reflection signal. 3. The system of claim 2, wherein: The number of preset wavelengths of the optical path detection signal is equal to the number of branch optical fibers. 4. The system of claim 2, wherein: The AWG is independent of ambient temperature, or The second channel module also includes: a temperature control device for maintaining a stable working environment of the AWG. 5. The system according to claim 1, wherein the wavelength division multiplexing coupler is located at the OLT side, comprising: 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 trunk optical fiber, and the R port is connected to the OTDR device; The first thin film filter all reflects light with a wavelength above 1625nm and transmits all light with a wavelength below 1625nm. 6. The system according to claim 1, wherein the wavelength selective coupler comprises a four-port optical circulator and a second thin-film filter, The interface 1 of the optical circulator is connected with the C interface of the second film filter, the interface 2 of the optical circulator is connected with the trunk optical fiber, the interface 3 of the optical circulator is connected with the optical splitter, and the optical circulator The interface 4 is connected with the P interface of the second thin film filter; The second thin film filter all reflects light with a wavelength above 1625nm and transmits all light with a wavelength below 1625nm. 7. The system according to claim 1, wherein the wavelength selective coupler comprises two three-port optical circulators and a fourth thin-film filter, The interface 1 of the first optical circulator is connected to the C interface of the fourth thin-film filter, the interface 2 of the first optical circulator is connected to the trunk optical fiber, and the interface 2 of the second optical circulator is connected to the optical splitter The interface 3 of the second optical circulator is connected with the P interface of the fourth thin film filter, and the interface 3 of the first optical circulator is connected with the interface 1 of the second optical circulator; The fourth film filter all reflects light with a wavelength above 1625nm and transmits all light with a wavelength below 1625nm. 8. The system according to claim 1, wherein the wavelength selective router comprises a four-port optical circulator and a third thin-film filter, The interface 1 of the optical circulator is connected with the P interface of the third film filter, the interface 2 of the optical circulator is connected with the optical splitter, the interface 3 of the optical circulator is connected with the branch optical fiber, and the optical ring The interface 4 of the liner is connected with the C interface of the third film filter; The third film filter all reflects light with a wavelength above 1625nm and transmits all light with a wavelength below 1625nm. 9. The system of claim 1, wherein the wavelength selective router comprises two three-port optical circulators and a fifth thin-film filter, The interface 1 of the first optical circulator is connected with the P interface of the fifth film filter, the interface 2 of the first optical circulator is connected with the optical splitter, and the interface 2 of the second optical circulator is connected with the branch Optical fiber connection, the interface 3 of the second optical circulator is connected with the C interface of the fifth film filter, and the interface 3 of the first optical circulator is connected with the interface 1 of the second optical circulator; The fifth film filter all reflects light with a wavelength above 1625nm and transmits all light with a wavelength below 1625nm. 10. The system according to any one of claims 1-9, wherein the wavelength division multiplexing coupler is located at the OLT. 11. A method for optical fiber fault detection, comprising: The optical path detection OTDR device generates an optical path detection signal for fault detection, and sends the optical path detection signal to the wavelength division multiplexing coupler; The wavelength division multiplexing coupler guides the optical path detection signal into the trunk optical fiber; A wavelength selective coupler connected to the trunk optical fiber transmits the optical path detection signal to an optical splitter; The optical splitter transmits the optical path detection signal to a wavelength selection router; The wavelength selection router transmits the optical path detection signal to the corresponding branch optical fiber; and receives the optical path detection reflection signal of the branch optical fiber, and sends the optical path detection reflection signal to the first optical path detection signal parallel to the optical splitter Two-channel module; The second path module sends the optical path detection reflection signal to the wavelength selective coupler; The wavelength selective coupler sends the optical path detection reflection signal to the wavelength division multiplexing coupler through the trunk optical fiber; The wavelength division multiplexing coupler separates the optical path detection reflection signal from the trunk fiber, and sends the optical path detection reflection signal to the OTDR device; The OTDR device judges the fiber fault of the trunk fiber and/or the branch fiber according to the optical path detection reflection signal. 12. The method of claim 11, wherein, The wavelength of the optical path detection signal is a preset wavelength corresponding to the target branch optical fiber; The optical path detection reflection signal is sent to the wavelength selective coupler through the channel of the AWG of the second channel module for the target branch optical fiber; The OTDR device judges the fault of the target branch optical fiber according to the optical path detection reflection signal.

Images