CN115250386A

CN115250386A - Optical communication system, optical signal transmission method and related equipment

Info

Publication number: CN115250386A
Application number: CN202110454388.2A
Authority: CN
Inventors: 周恩宇; 曾小飞; 林斌超
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-04-26
Filing date: 2021-04-26
Publication date: 2022-10-28
Also published as: WO2022227863A1

Abstract

The embodiment of the application discloses an optical communication system, an optical signal transmission method and related equipment. When the optical fiber transmission fails, the ONU closest to the main OLT starts the sub-OLT to replace the main OLT, so that the subsequent ONU can still normally communicate. The optical communication system comprises a main OLT, a first ONU, a second ONU, a first optical splitter and a second optical splitter. The first ONU comprises a first sub OLT and a first sub ONU. The first port of the first optical splitter is connected with the main OLT, the second port of the first optical splitter is connected with the first sub OLT, the third port of the first optical splitter is connected with the first sub ONU, the fourth port of the first optical splitter is connected with one port of the second optical splitter, and the other port of the second optical splitter is connected with the second ONU. The main OLT is used for sending a target optical signal. If the first sub-ONU cannot receive the target optical signal, the first sub-ONU is configured to send first indication information to the first sub-OLT. The first sub OLT is configured to send a first optical signal according to the first indication information. The second ONU is used for receiving the first optical signal.

Description

Optical communication system, optical signal transmission method and related equipment

Technical Field

The present application relates to the field of optical communications, and in particular, to an optical communication system, an optical signal transmission method, and a related device.

Background

Passive Optical Network (PON) is an implementation technology of an optical access network, and PON is an optical access technology of point-to-multipoint transmission. An Optical Line Terminal (OLT) is connected to a network side device of an upper layer, and the lower layer is connected to one or more Optical Distribution Networks (ODNs). The ODN includes an Optical splitter for Optical power distribution, a trunk fiber connected between the Optical splitter and the OLT, and branch fibers connected between the Optical splitter and Optical Network Units (ONUs). When data is transmitted in a downlink mode, the ODN transmits the data downlink from the OLT to each ONU through the optical splitter, and the ONU selectively receives the downlink data carrying the identification of the ONU. When data is transmitted in an uplink mode, the ODN combines optical signals sent by the ONU in one path and transmits the optical signals to the OLT.

The communication network within the mine needs to be scalable and can be extended back one by one based on the nodes that have been established. For example, the mine has N nodes, and the node N +1 and the node N +2 may be added after the node N according to actual requirements. In order to realize communication with large bandwidth and low time delay among nodes in a mine, the networking architecture of the PON can be applied to mine communication.

Specifically, the OLT transmits a downstream optical signal through an optical fiber. Each ONU is connected in series as a node on an optical fiber in order to receive a downstream optical signal. However, when any section of the optical fiber fails, the subsequent ONU cannot receive the optical signal, which results in abnormal communication.

Disclosure of Invention

The embodiment of the application provides an optical communication system, an optical signal transmission method and related equipment. When the optical fiber transmission is normal, sub-ONUs in the ONUs work to maintain the original functions of the ONUs. When the optical fiber transmission fails, the ONU closest to the main OLT starts the sub-OLT to replace the main OLT, so that the subsequent ONUs can still normally communicate, and the communication stability is improved.

In a first aspect, the present application provides an optical communication system. The optical communication system comprises a main OLT, a first ONU, a second ONU, a first optical splitter and a second optical splitter. The first ONU comprises a first sub OLT and a first sub ONU. The first port of the first optical splitter is connected to the main OLT. The second port of the first optical splitter is connected to the first sub OLT. And the third port of the first optical splitter is connected with the first sub-ONU. The fourth port of the first optical splitter is connected to one of the ports of the second optical splitter. The other port of the second optical splitter is connected with the second ONU. Specifically, the main OLT is configured to transmit the target optical signal. The first sub-ONU is used for receiving a target optical signal. If the optical power of the target optical signal received by the first sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is weakened and the optical power variation value is greater than the second threshold, the first sub-ONU is configured to send the first indication information to the first sub-OLT. The first sub-OLT is configured to send a first optical signal according to the first indication information, and the second ONU is configured to receive the first optical signal.

In this embodiment, a plurality of optical splitters are connected in series to an optical fiber connected to the main OLT, and each optical splitter is correspondingly connected to one ONU, so that each ONU can receive a downlink optical signal transmitted by the OLT through the optical fiber. Furthermore, each ONU is internally provided with a sub OLT and a sub ONU. Namely, the ONU in the system has the original functions of the ONU and also has the functions of the OLT. When optical fiber transmission is normal, sub-ONUs in the ONUs work to maintain the original functions of the ONUs. When the optical fiber transmission fails, the ONU closest to the main OLT starts the sub-OLT to replace the main OLT, so that the subsequent ONUs can still normally communicate, and the communication stability is improved.

In some possible embodiments, the first port of the first optical splitter is used for inputting a target optical signal. The third port of the first optical splitter is used for outputting the target optical signal to the first sub-ONU. And the fourth port of the first optical splitter is used for outputting the target optical signal to the second ONU. If the optical power of the target optical signal received by the first sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is reduced and the optical power variation value is greater than the second threshold, the second port of the first optical splitter is used for inputting the first optical signal. The third port of the first splitter is configured to output the first optical signal to the first sub-ONU. And the fourth port of the first optical splitter is used for outputting the first optical signal to the second ONU. In this embodiment, a 2 × 2 optical splitter is adopted, and there are two input ports and two output ports in the downstream direction, which is convenient for matching with the optical communication system provided in the present application.

In some possible embodiments, the optical communication system further includes a third optical splitter and a third ONU. The second ONU comprises a second sub OLT and a second sub ONU. The first port of the second optical splitter is connected with the fourth port of the first optical splitter. The second port of the second optical splitter is connected to the second sub OLT. And the third port of the second optical splitter is connected with the second sub-ONU. The fourth port of the second optical splitter is connected to one of the ports of the third optical splitter. And the other port of the third optical splitter is connected with a third ONU. The second sub-ONU is used for receiving the target optical signal. And if the optical power of the target optical signal received by the second sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the second sub-ONU is weakened and the optical power variation value is greater than the second threshold, the second sub-ONU is configured to send second indication information to the second sub-OLT. The second sub OLT is configured to send a second optical signal according to the second indication information. The third ONU is used for receiving the second optical signal. Through the mode, the third ONU can be continuously added in the optical communication system, and the optical communication system can be extended backwards one by one on the basis of the existing ONU, so that the optical communication system is convenient to expand continuously according to actual requirements.

In some possible embodiments, the main OLT is further configured to send a notification message before the main OLT sends the target optical signal. If the optical power of the target optical signal received by the first sub-ONU is lower than a first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is reduced and the optical power variation value is greater than a second threshold, the first sub-ONU is configured to determine a first time period according to the notification message, and the first indication information includes the first time period. The first sub OLT is specifically configured to send a first optical signal at a first time period according to the first indication information. And if the optical power of the target optical signal received by the second sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the second sub-ONU is weakened and the optical power change value is greater than the second threshold, the second sub-ONU is configured to determine a second time period according to the notification message, and the second indication information includes the second time period. The second sub OLT is specifically configured to send a second optical signal in a second time period according to the second indication information. In this embodiment, the main OLT allocates a corresponding light-emitting time period to each ONU, and the sub-OLTs in each ONU emit light in the respective corresponding time period after the main OLT goes offline, so that each ONU can emit light according to a uniform rule, and the realizability of the scheme is enhanced.

In some possible embodiments, the notification message is further for indicating a total duration of the first time period and the second time period, the first time period and the second time period not overlapping. And if the second sub-ONU can only receive the second optical signal within the total time length, the second sub-ONU is used for sending third indication information to the second sub-OLT. The second sub OLT is configured to continuously send the second optical signal according to the third indication information. In this embodiment, the first sub OLT and the second sub OLT emit light in a time-sharing manner, so that light emission collision between the first sub OLT and the second sub OLT is avoided, and the second sub ONU can recognize the second optical signal transmitted by the second sub OLT.

In some possible embodiments, there is an overlapping period between the first period and the second period. And if the second sub-ONU can recognize the second optical signal in the second time interval, the second sub-ONU is configured to send third indication information to the second sub-OLT. The second sub OLT is configured to continuously send the second optical signal according to the third indication information. In this embodiment, the first sub OLT and the second sub OLT may emit light at the same time, which improves the flexibility of the scheme.

In some possible embodiments, the first sub OLT is further configured to receive an upstream optical signal from the second ONU, which improves the practicability of the present solution.

In some possible embodiments, the wavelength of the target optical signal is the same as the wavelength of the first optical signal to meet standard requirements.

In some possible embodiments, the target optical signal includes a target identifier of the main OLT, and the first optical signal includes a first identifier of the first sub-OLT, so that each sub-ONU can identify a transmitting end of the downstream optical signal.

In a second aspect, the present application provides a method for transmitting an optical signal. The method comprises the following steps. The first ONU detects a target optical signal from the main optical line terminal OLT through the first sub-ONU. The first ONU comprises a first sub-ONU and a first sub-OLT. And if the optical power of the target optical signal received by the first sub-ONU is lower than a first threshold value, and/or if the optical power of the target optical signal received by the first sub-ONU is weakened and the optical power change value is larger than a second threshold value, the first ONU sends the first optical signal through the first sub-OLT.

In some possible embodiments, a first optical splitter is connected between the first ONU and the main OLT, and a first port of the first optical splitter is connected to the main OLT. The second port of the first optical splitter is connected with the first sub OLT. And the third port of the first optical splitter is connected with the first sub-ONU. And the fourth port of the first optical splitter is connected with the first port of the second optical splitter, and the second port of the second optical splitter is connected with the second ONU.

In some possible embodiments, the first port of the first optical splitter is used for inputting a target optical signal. The third port of the first optical splitter is used for outputting the target optical signal to the first sub-ONU. And the fourth port of the first optical splitter is used for outputting the target optical signal to the second ONU. If the optical power of the target optical signal received by the first sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is reduced and the optical power variation value is greater than the second threshold, the second port of the first optical splitter is used for inputting the first optical signal. The third port of the first optical splitter is used for outputting the first optical signal to the first sub-ONU. And the fourth port of the first optical splitter is used for outputting the first optical signal to the second ONU.

In some possible embodiments, before the first ONU detects the target optical signal from the main OLT through the first sub-ONU, the method further includes: the first ONU receives a notification message from the main OLT. The first ONU transmitting the first optical signal through the first sub-OLT includes: the first ONU transmits the first optical signal at the first period indicated by the notification message through the first sub-OLT.

In some possible embodiments, if the first sub-ONU cannot detect the target optical signal, the method further includes: the first ONU detects the first optical signal and the second optical signal from the third ONU through the first sub-ONU. The third ONU is configured to transmit the second optical signal in the second period. Wherein the first time period and the second time period are not overlapped, and the notification message is further used for indicating the total duration of the first time period and the second time period. If the first sub-ONU can only receive the first optical signal within the total time length, the first ONU continuously transmits the first optical signal through the first sub-OLT.

In some possible embodiments, if the first sub-ONU cannot detect the target optical signal, the method further includes: the first ONU detects the first optical signal and the second optical signal from the third ONU through the first sub-ONU. The third ONU is configured to transmit the second optical signal in the second period. Wherein there is an overlapping period between the first period and the second period. If the first sub-ONU can recognize the first optical signal in the first period, the first ONU continuously transmits the first optical signal through the first sub-OLT.

In some possible embodiments, the wavelength of the target optical signal is the same as the wavelength of the first optical signal.

In some possible embodiments, the target optical signal comprises a target identification of the main OLT, and the first optical signal comprises a first identification of the first sub-OLT.

In a third aspect, the present application provides a method for transmitting an optical signal. The method comprises the following steps. The main OLT sends notification messages to the first ONU and the second ONU. The first ONU comprises a first sub OLT and a first sub ONU. The second ONU comprises a second sub-OLT and a second sub-ONU. A first optical splitter is connected between the first ONU and the main OLT. The first port of the first optical splitter is connected to the main OLT. The second port of the first optical splitter is connected to the first sub OLT. And the third port of the first optical splitter is connected with the first sub-ONU. The fourth port of the first optical splitter is connected with the first port of the second optical splitter. The second port of the second optical splitter is connected to the second sub OLT. And the third port of the second optical splitter is connected with the second sub-ONU. The main OLT transmits a target optical signal to the first ONU and the second ONU. If the first sub-ONU and the second sub-ONU cannot detect the target optical signal from the main OLT, the notification message is used to instruct the first sub-OLT to transmit the first optical signal in the first period. Wherein the notification message is used to instruct the second sub OLT to transmit the second optical signal in the second period.

In a fourth aspect, an embodiment of the present application provides an ONU, where the ONU includes a sub OLT unit and a sub ONU unit. The sub-ONU unit is used for detecting a target optical signal from the main OLT. And if the optical power of the target optical signal received by the sub-ONU unit is lower than a first threshold value, and/or if the optical power of the target optical signal received by the sub-ONU unit is weakened and the optical power change value is larger than a second threshold value, the sub-ONU unit is used for sending indication information to the sub-OLT unit. The sub OLT unit is used for sending the first optical signal according to the indication information.

In some possible embodiments, a first optical splitter is connected between the ONU and the main OLT. The first port of the first optical splitter is connected with the main OLT. The second port of the first optical splitter is connected with the sub OLT unit. And the third port of the first optical splitter is connected with the sub-ONU unit. The fourth port of the first optical splitter is connected with the first port of the second optical splitter. And the second port of the second optical splitter is connected with the second ONU.

In some possible embodiments, the first port of the first optical splitter is used to input a target optical signal. The third port of the first splitter is used to output the target optical signal to the sub-ONU unit. And the fourth port of the first optical splitter is used for outputting the target optical signal to the second ONU. If the optical power of the target optical signal received by the sub-ONU unit is lower than the first threshold, and/or if the optical power of the target optical signal received by the sub-ONU unit decreases and the optical power variation value is greater than the second threshold, the second port of the first optical splitter is used for inputting the first optical signal. The third port of the first optical splitter is used for outputting the first optical signal to the sub-ONU unit. And the fourth port of the first optical splitter is used for outputting the first optical signal to the second ONU.

In some possible embodiments, the sub-ONU unit is further configured to receive a notification message from the main OLT before the sub-ONU unit is configured to detect the target optical signal from the main OLT. And if the sub-ONU unit cannot receive the target optical signal, the sub-ONU unit is used for determining a first time interval according to the notification message. Wherein the indication information includes the first period. The sub OLT unit is specifically configured to send the first optical signal at the first time period according to the indication information.

In some possible embodiments, the sub-ONU unit is further configured to detect the first optical signal and the second optical signal from the third ONU if the sub-ONU unit cannot detect the target optical signal. The third ONU is configured to transmit the second optical signal in the second period. Wherein the first time period and the second time period are not overlapped, and the notification message is further used for indicating the total duration of the first time period and the second time period. And if the sub ONU unit can only receive the first optical signal in the total time length, the sub OLT unit continuously sends the first optical signal.

In some possible embodiments, the sub-ONU unit is further adapted to detect the first optical signal and a second optical signal from a third ONU if the sub-ONU unit cannot detect the target optical signal. The third ONU is configured to transmit the second optical signal in the second period. Wherein there is an overlapping period between the first period and the second period. If the sub-ONU unit can recognize the first optical signal in the first period, the sub-OLT unit continuously transmits the first optical signal.

In some possible embodiments, the target optical signal comprises a target identification of the main OLT, and the first optical signal comprises a first identification of the sub-OLT unit.

In a fifth aspect, embodiments of the present application provide an OLT including a processor and an optical transceiver. The processor and the optical transceiver are connected to each other by wires. The processor is adapted to perform the steps as in the method of the third aspect.

In some possible embodiments, the OLT further comprises a memory, and the processor calls the program code in the memory for performing the steps as in the method of the third aspect.

In this application embodiment, a plurality of optical splitters are connected in series on the optical fiber connected with the main OLT, and each optical splitter can be correspondingly connected with one ONU, so that each ONU can receive the downstream optical signal sent by the OLT through the optical fiber. Furthermore, each ONU is internally provided with a sub OLT and a sub ONU. That is, the ONU in the system has both the original function of the ONU and the function of the OLT. When optical fiber transmission is normal, sub-ONUs in the ONUs work to maintain the original functions of the ONUs. When the optical fiber transmission fails, the ONU closest to the main OLT starts the sub-OLT to replace the main OLT, so that the subsequent ONUs can still normally communicate, and the communication stability is improved.

Drawings

Fig. 1 is a schematic structural diagram of a PON system in a mine;

fig. 2 is a schematic structural diagram of an optical communication system in an embodiment of the present application;

fig. 3 is a schematic structural diagram of an ONU in the embodiment of the present application;

fig. 4 is a schematic flowchart of a method for transmitting an optical signal according to an embodiment of the present disclosure;

fig. 5 is a schematic structural diagram of a possible ONU in the present application;

fig. 6 is a schematic structural diagram of another possible ONU in the present application;

fig. 7 is a schematic structural diagram of another possible main OLT in the present application.

Detailed Description

It should be noted that the terms "first," "second," "third," and "fourth," etc. in the description and claims of this application and in the accompanying drawings are used for distinguishing between similar elements and not necessarily for limiting a particular order or sequence. It is to be understood that the terms so described are interchangeable under appropriate circumstances such that the embodiments described herein are capable of operation in other sequences than described of illustrated herein. Furthermore, the terms "comprising" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, article, or apparatus.

The embodiment of the application is mainly applied to a communication system in a mine, and all nodes in the mine are sequentially connected in series through a line. Firstly, the communication system in the mine is required to have expandability, and can be extended backwards one by one on the basis of the existing nodes, for example, the node N +1 is continuously added after the node N, and the like. Secondly, the communication system in the mine needs to be capable of realizing ad hoc networking, for example, when a line between any two nodes fails, other nodes can still communicate with each other. In order to realize communication with large bandwidth and low time delay among nodes in a mine, a networking architecture of a Passive Optical Network (PON) can also be applied to mine communication.

Fig. 1 is a schematic structural diagram of a PON system in a mine. As shown in fig. 1, the PON system adopts a chain type networking structure. The main OLT is connected with the trunk optical fiber, and a plurality of optical splitters are sequentially connected in series on the trunk optical fiber. And each optical splitter is also connected with the corresponding ONU through one branch optical fiber. That is, each ONU can be regarded as a node, and the nodes are connected in series to the trunk optical fiber through the respective connected optical splitters. The main OLT transmits a downlink optical signal through the trunk optical fiber, and each ONU receives the downlink optical signal through the branch optical fiber and selects required information from the downlink optical signal. However, when any section of the trunk optical fiber fails, the subsequent ONU cannot receive the optical signal, which results in abnormal communication. For example, if the main optical fiber between ONU1 and ONU2 fails, all ONUs, including ONU2, behind ONU1 cannot receive the downstream optical signal transmitted by the main OLT. Resulting in abnormal communication in the mine, and bringing great potential safety hazard.

Therefore, the application provides an optical communication system, when optical fiber transmission fails, the ONU closest to the main OLT activates the sub-OLT to replace the main OLT, so that the subsequent ONUs can still normally communicate, and the communication stability is improved.

Fig. 2 is a schematic structural diagram of an optical communication system in an embodiment of the present application. As shown in fig. 2, the optical communication system includes, but is not limited to, a main OLT 10, an ONU 20, an ONU 30, an ONU 40, an optical splitter 50, an optical splitter 60, and an optical splitter 70. The ONU 20 includes a sub OLT 201 and a sub ONU 202, the ONU 30 includes a sub OLT 301 and a sub ONU 302, and the ONU 40 includes a sub OLT 401 and a sub ONU 402. The

beam splitters

50, 60 and 70 are all 2 x 2 beam splitters, i.e. each beam splitter has two input ports and two output ports. Specifically, port 1 of the optical splitter 50 is connected to the main OLT 10, port 2 of the optical splitter 50 is connected to the sub OLT 201, and port 3 of the optical splitter 50 is connected to the sub ONU 202. Port 1 of the optical splitter 60 is connected to port 4 of the optical splitter 50, port 2 of the optical splitter 60 is connected to the sub OLT 301, and port 3 of the optical splitter 60 is connected to the sub ONU 302. Port 1 of the optical splitter 70 is connected to port 4 of the optical splitter 60, port 2 of the optical splitter 70 is connected to the sub OLT 401, and port 3 of the optical splitter 70 is connected to the sub OLT 402. It should be understood that, on the basis of the system structure shown in fig. 2, it is also possible to sequentially expand more ONUs and optical splitters in the connection manner described above, where each of the subsequently expanded ONUs also has a sub OLT and a sub ONU, and each of the subsequently expanded optical splitters is a 2 × 2 optical splitter.

It should be noted that, the ONU in the optical communication system is different from the conventional ONU, and the ONU provided in the present application has both the function of the ONU and the function of the OLT. That is, the sub-ONUs in each ONU are used to implement the functions of the ONUs, and the sub-OLT in each ONU is used to implement the functions of the OLT. The ONU 20 is further described below as an example.

Fig. 3 is a schematic structural diagram of an ONU in the embodiment of the present application. As shown in fig. 3, the sub OLT 201 includes an optical module 201a and a Media Access Control (MAC) chip 201b, and the sub ONU 202 includes an optical module 202a and a MAC chip 202b. That is, the sub OLT 201 and the sub ONU 202 are two mutually independent devices, each having its own optical module and MAC chip. The sub OLT 201 is similar in structure to a conventional OLT, and the sub ONU 202 is also similar in structure to a conventional ONU. The ONU 20 provided in the present application may be regarded as a device that integrates the sub OLT 201 and the sub ONU 202, and the sub OLT 201 and the sub ONU 202 may also perform communication.

It should be understood that the main purpose of configuring the sub OLT in each ONU is to allow the sub OLT to replace the main OLT after the line fails, so as to ensure that the system can continue to operate normally. Specifically, when the lines of the optical communication system are all normal, each ONU may receive a downstream optical signal transmitted by the main OLT. At this time, each ONU only needs to enable the local sub-ONU to maintain the function of the respective ONU. However, if a fault occurs in one of the lines, the ONUs behind the faulty line cannot receive the optical signal transmitted by the main OLT. At this time, after the faulty line, an ONU closest to the main OLT activates the local sub-OLT to transmit a downlink optical signal instead of the main OLT, so as to ensure that the subsequent other ONUs can communicate normally. Taking fig. 2 as an example, if a line between the optical splitter 50 and the optical splitter 60 fails, the ONU 30 and the ONU 40 cannot receive the downstream optical signal from the main OLT. At this time, the ONU 30 is required to enable the local sub OLT 301 to transmit the downstream optical signal instead of the main OLT. That is, the ONU 30 enables the OLT function, and the ONU 40 maintains the original ONU function. The ONU which starts the local sub OLT and other ONUs form a new PON system, and the other ONUs register on line again.

Each ONU may determine whether or not to receive the optical signal from the main OLT based on the optical power of the received optical signal. The determination condition that each ONU cannot receive the optical signal transmitted by the main OLT includes, but is not limited to, the following conditions. Firstly, the optical power of the optical signal received by the ONU is lower than a first threshold value. Secondly, the optical power of the optical signal received by the ONU is weakened, and the optical power change value is larger than a second threshold value.

It should also be understood that, based on the particular structure of the ONU provided in this application, this application employs a 2 × 2 splitter, with two input ports and two output ports in the downstream direction. Taking the optical splitter 50 as an example, the downstream optical signal transmitted by the main OLT 10 is input from port 1, output from port 3 to the sub-ONU 202, and output from port 4 to the optical splitter 60. After the sub OLT 201 operates instead of the main OLT 10, the downstream optical signal transmitted by the sub OLT 201 is input from the port 2 and output from the port 4 to the optical splitter 60. In the present application, a 2 × 3 spectrometer, a 2 × 4 spectrometer, or the like may be used, and the present invention is not limited to this.

In some possible embodiments, after the sub OLT in a certain ONU starts to operate instead of the main OLT, the sub ONU in the ONU may stop operating to reduce power consumption, or the sub ONU in the ONU may continue to operate, which is not limited herein. Similarly, if a sub-ONU in a certain ONU keeps working normally, the local sub-OLT may not be enabled temporarily. After the sub OLT operates instead of the main OLT, the wavelength of the downlink optical signal transmitted by the sub OLT should be the same as the wavelength of the downlink optical signal transmitted by the main OLT to meet the standard requirement. The downlink optical signal sent by the main OLT and the downlink optical signal sent by each sub-OLT should have their own identifiers, so that the other ONUs can distinguish the received optical signals. Further, each sub OLT may receive an upstream optical signal in addition to transmitting a downstream optical signal, similar to the main OLT. However, the received upstream optical signal may not be processed until the sub OLT is actually operated in place of the main OLT.

First, the specific operation mode of the ONU in this embodiment is described below by taking the ONU 20 as an example. Specifically, the sub-ONU 202 is configured to receive a downstream optical signal from the main OLT 10. If the line between the main OLT 10 and the ONU 20 fails, the sub-ONU 202 cannot receive the downstream optical signal from the main OLT 10. Then, the sub-ONU 202 may send indication information to the sub-OLT 201 to instruct the sub-OLT 201 to send a downstream optical signal. It should be understood that since the ONU 20 is the ONU closest to the main OLT 10, the sub-OLT 201 is enabled as long as the sub-ONU 202 does not receive the downstream optical signal, and the determination logic is relatively simple.

However, if the downstream optical signal from the main OLT 10 cannot be received by the other ONUs behind the ONU 20, the local sub-OLT is not necessarily directly started. The local sub OLT is not enabled unless the ONU cannot receive the downstream optical signal previously sent by the other sub OLT. For example, none of the

ONUs

20, 30, and 40 can receive the downstream optical signal transmitted by the main OLT 10, and the line between the main OLT 10 and the ONU 20 is definitely faulty. However, it is not known whether or not the line between the

ONUs

20 and 30 and the line between the

ONUs

30 and 40 are faulty. If the ONU 30 cannot receive the downstream optical signal from the sub OLT 201, it indicates that the line between the ONU 20 and the ONU 30 is also faulty, and then the sub OLT 301 needs to be enabled.

Therefore, the present application provides multiple detection mechanisms for helping each ONU determine whether to enable the local sub OLT. It should be noted that the various detection mechanisms described below are applicable to each ONU in the optical communication system.

Detection mechanism 1:

the main OLT allocates a corresponding light-emitting time slot to each ONU, so that after each ONU cannot receive a downlink optical signal from the main OLT, the sub-OLTs in each ONU transmit optical signals in different time periods. Specifically, the main OLT sends a notification message to notify each ONU of the corresponding light-emitting timeslot and the total light-emitting duration of all ONUs. For example, if none of the

ONUs

20, 30, and 40 receive the downlink optical signal transmitted by the main OLT 10, the sub OLT 201 emits light in a time period delayed by 20ms to 40ms, the sub OLT 301 emits light in a time period delayed by 40ms to 60ms, the sub OLT 401 emits light in a time period delayed by 60ms to 80ms, and so on. By the mode, each sub OLT emits light in sequence, so that the conflict caused by the simultaneous light emission of a plurality of sub OLTs is avoided, and each sub ONU can conveniently identify the received optical signal. The following describes a method for determining whether to enable the local sub-OLT by taking the ONU 40 as an example.

The sub-ONU 402 is required to receive the optical signal transmitted by the local sub-OLT 401 in addition to the optical signals transmitted by the sub-OLT 201 and the sub-OLT 301. And, the sub-ONU 402 can know the light-emitting time slot of the sub-OLT 401 and the total light-emitting time length of all sub-OLTs through the notification message sent by the main OLT. Therefore, if the sub-ONU 402 can only receive the optical signal transmitted by the sub-OLT 401 within the total time period of all the sub-OLTs emitting light, the sub-ONU 402 instructs the sub-OLT 401 to continuously transmit the optical signal. Otherwise, the sub-ONU 402 instructs the sub-OLT 401 to suspend transmitting optical signals and maintain the operation of the sub-ONU 402. It should be noted that the optical signal sent by each sub OLT carries a respective identifier, so that the sub-ONUs 402 can identify the received optical signal.

Detection mechanism 2:

unlike the detection mechanism 1 described above, the sub OLTs in each ONU do not emit light sequentially, and the light emission periods of each sub OLT may overlap. In one possible implementation, the main OLT issues a notification message to inform each ONU of its corresponding light-emitting timeslot. Wherein, the light-emitting time slots of the sub-OLT in each ONU are completely overlapped or partially overlapped. In another possible implementation, the sub OLT in each ONU may emit light with a random delay, and due to the randomness of the delay, it may happen that multiple sub OLTs emit light at the same time period. For example, if all of the

ONUs

20, 30, and 40 cannot receive the downstream optical signal transmitted by the main OLT 10, the sub OLT 201 emits light at a time delayed by 20ms to 40ms, the sub OLT 301 emits light at a time delayed by 30ms to 50ms, and the sub OLT 401 emits light at a time delayed by 25ms to 45 ms. Compared with the detection mechanism 1, the determination method of whether to enable the local sub-OLT is also changed accordingly. The following describes a method for determining whether to enable the local sub-OLT by taking the ONU 40 as an example.

Sub ONU 402 needs to receive optical signals transmitted from local sub OLT 401 in addition to optical signals transmitted from sub OLT 201 and sub OLT 301. It should be understood that there are other sub-OLTs that emit light during the period when the sub-OLT 401 emits light, and if the sub-ONU 402 receives optical signals transmitted by a plurality of sub-OLTs during the period when the sub-OLT 401 emits light, a collision may be caused, so that the sub-ONU 402 cannot identify the optical signal transmitted by the sub-OLT 401. Therefore, if the sub-ONU 402 can recognize the optical signal transmitted by the sub-OLT 401 during the period in which the sub-OLT 401 emits light, the sub-ONU 402 instructs the sub-OLT 401 to continuously transmit the optical signal. Otherwise, the sub-ONU 402 instructs the sub-OLT 401 to suspend transmitting optical signals and maintain the operation of the sub-ONU 402. By the method, each sub OLT is not strictly required to emit light at different time intervals, the light emitting mode of each sub OLT is more flexible, and each ONU can be helped to judge whether the local sub OLT needs to be started or not in a relatively short time.

It should be noted that, in practical applications, in addition to the two detection mechanisms listed above, other methods may be used for detection, and the method is not limited herein. For example, in the detection mechanism 2, when the sub OLT in each ONU emits light with a random delay, the sub ONU 402 stops emitting light from the sub OLT 401 when recognizing an optical signal transmitted from the sub OLT other than the sub OLT 401.

It should be understood that the sub OLT and the sub-ONU in each ONU need to operate simultaneously during the period of time in which the above-described detection mechanism is performed. This stage enables the sub OLT only for the purpose of coordinating the detection of temporary lighting, and not for the official enablement. The sub OLT formally enabled after the detection is finished needs to continuously emit light instead of the main OLT. In addition, the ONU 20 closest to the main OLT 10 also needs to perform the above-mentioned detection mechanism, and if the sub-ONU 202 cannot receive the optical signal transmitted by the sub-OLT 201, it is necessary to suspend the light emission of the sub-OLT 201, which indicates that the line between the ONU 20 and the optical splitter 50 may be faulty.

In this application embodiment, a plurality of optical splitters are connected in series on the optical fiber connected with the main OLT, and each optical splitter can be correspondingly connected with one ONU, so that each ONU can receive the downstream optical signal sent by the OLT through the optical fiber. Furthermore, each ONU is internally provided with a sub OLT and a sub ONU. Namely, the ONU in the system has the original functions of the ONU and also has the functions of the OLT. When optical fiber transmission is normal, sub-ONUs in the ONUs work to maintain the original functions of the ONUs. When the optical fiber transmission fails, the ONU closest to the main OLT starts the sub-OLT to replace the main OLT, so that the subsequent ONUs can still normally communicate, and the communication stability is improved.

Based on the above-described technique of the optical communication system, a transmission method of an optical signal applied to the optical communication system will be described below. It should be noted that the system structure corresponding to the transmission method of the optical signal described below can be as described in the embodiment of the optical communication system. However, it is not limited to the optical communication system described above.

Fig. 4 is a flowchart illustrating a method for transmitting an optical signal according to an embodiment of the present disclosure. The optical communication system in this embodiment may specifically be the optical communication system shown in fig. 2. For convenience of description, the following embodiments are mainly described in terms of an optical communication system including a main OLT and two ONUs. In this example, the transmission method of the optical signal includes the following steps.

401. The main OLT transmits a notification message to the first ONU and the second ONU.

In this embodiment, the first ONU is the ONU closest to the main OLT, for example, the first ONU may correspond to the ONU 20 shown in fig. 2, and the second ONU may correspond to the ONU 30 shown in fig. 2. The main OLT allocates corresponding light-emitting time periods for the first ONU and the second ONU respectively and informs the first ONU and the second ONU by sending notification messages.

402. The first ONU determines a first time period in which the first sub OLT emits light according to the notification message.

Specifically, after receiving the notification message, the first sub-ONU determines the first time period corresponding to the notification message, and further, the first sub-ONU may notify the first time period to the first sub-OLT by sending a message to the first sub-OLT.

403. And the second ONU determines a second time interval of the second sub OLT light according to the notification message.

Specifically, the second sub-ONU determines the second time period corresponding to the notification message after receiving the notification message, and further, the second sub-ONU may notify the second time period to the second sub-OLT by sending a message to the second sub-OLT.

404. The main OLT transmits a target optical signal to the first ONU and the second ONU.

405. The first sub-ONU determines whether the target optical signal is detected, if so, step 406 is executed, and if not, step 407 is executed.

406. And if the first sub-ONU detects the target optical signal, the first ONU maintains the first sub-ONU to work.

407. If the first sub-ONU does not detect the target optical signal, the first sub-ONU sends first indication information to the first sub-OLT, for indicating the first sub-OLT to send the first optical signal.

408. The second sub-ONU determines whether the target optical signal is detected, if so, performs step 409, and if not, performs step 410.

409. And if the second sub-ONU detects the target optical signal, the second ONU maintains the second sub-ONU to work.

410. And if the second sub-ONU does not detect the target optical signal, the second sub-ONU sends second indication information to the second sub-OLT, and the second indication information is used for indicating the second sub-OLT to send a second optical signal.

411. The first sub OLT transmits a first optical signal at a first period according to the first indication information.

412. And the second sub OLT transmits a second optical signal in a second time interval according to the second indication information.

413. The first ONU detects the first optical signal and selects a working mode according to a detection result.

Specifically, the first sub-ONU is configured to detect a first optical signal sent by the first sub-OLT. If the first sub-ONU can detect the first optical signal, the first sub-ONU will notify the first sub-OLT to continuously transmit the first optical signal. Namely, the first ONU formally enables the first sub OLT. Otherwise, the first sub-ONU notifies the first sub-OLT to suspend sending the first optical signal, and maintains the operation of the first sub-ONU.

414. The second ONU detects the first optical signal and the second optical signal and selects a working mode according to a detection result.

Specifically, the second sub-ONU is configured to detect the first optical signal and the second optical signal. It should be appreciated that based on whether the first time period and the second time period overlap, the second sub-ONU will employ a different detection mechanism to determine whether the second sub-OLT needs to be enabled. Please specifically refer to the various detection mechanisms provided in the embodiment shown in fig. 2, which are not described herein again. If the second sub-ONU determines by detection that the second OLT is to be formally enabled, the second sub-ONU will inform the second sub-OLT to continue sending the second optical signal. Otherwise, the second sub-ONU notifies the second sub-OLT to suspend sending the second optical signal, and maintains the operation of the second sub-ONU.

The main OLT and the ONU provided in the present application are introduced below.

Fig. 5 is a schematic structural diagram of a possible ONU in the present application. The ONU includes a sub-OLT unit 501 and a sub-ONU unit 502, and the sub-OLT unit 501 and the sub-ONU unit 502 are connected to each other by a line. Specifically, the ONU may be any one of the ONUs in the embodiments shown in fig. 2 and fig. 4. The sub-OLT unit 501 is configured to perform the operation of any one sub-OLT in the embodiments shown in fig. 2 and fig. 4, and the sub-ONU unit 502 is configured to perform the operation of any one sub-ONU in the embodiments shown in fig. 2 and fig. 4.

Fig. 6 is a schematic structural diagram of another possible ONU in the present application. The sub OLT unit 501 includes a processor 501a and an optical transceiver 501c. The processor 501a and the optical transceiver 501c are connected to each other by a line. It should be noted that the optical transceiver 501c is configured to perform the signal transceiving operation of the sub OLT in the embodiments shown in fig. 2 and 4. The processor 501a is configured to perform other operations of the sub OLT in addition to signal transceiving in the embodiments shown in fig. 2 and 4. Optionally, the sub OLT unit 501 further comprises a memory 501b, wherein the memory 501b is used for storing program instructions and data. The sub-ONU unit 502 includes a processor 502a and an optical transceiver 502c. The processor 502a and the optical transceiver 502c are interconnected by wires. It should be noted that the optical transceiver 502c is configured to perform the operations of transmitting and receiving signals by the sub-ONU in the embodiments shown in fig. 2 and 4. The processor 502a is configured to perform other operations of the sub-ONUs besides signal transceiving in the embodiments shown in fig. 2 and 4. Optionally, sub-ONU unit 502 further comprises a memory 501b, wherein memory 502b is used for storing program instructions and data.

In one possible implementation, the processor 501a includes a MAC chip 201b as shown in fig. 3, and the optical transceiver 501c includes an optical module 201a as shown in fig. 3. The processor 502a includes the MAC chip 202b shown in fig. 3, and the optical transceiver 502c includes the optical module 202a shown in fig. 3.

Fig. 7 is a schematic structural diagram of another possible main OLT in the present application. A main OLT packet processor 701 and an optical transceiver 703. The processor 701 and the optical transceiver 703 are connected to each other by a line. It should be noted that the optical transceiver 703 is configured to perform the signal transceiving operation of the main OLT in the embodiments shown in fig. 2 and 4. The processor 701 is configured to perform other operations of the main OLT in addition to signal transceiving in the embodiments shown in fig. 2 and 4. Optionally, the main OLT further comprises a memory 702, wherein the memory 702 is adapted to store program instructions and data.

It should be noted that the processors shown in fig. 6 and fig. 7 may be a general Central Processing Unit (CPU), a microprocessor, an application specific integrated circuit ASIC, or at least one integrated circuit, and are configured to execute related programs to implement the technical solutions provided by the embodiments of the present application. The memory shown in fig. 6 and 7 described above may store an operating system and other applications. When the technical solution provided by the embodiments of the present application is implemented by software or firmware, program codes for implementing the technical solution provided by the embodiments of the present application are stored in a memory and executed by a processor. In one embodiment, the processor may include memory internally. In another embodiment, the processor and memory are two separate structures.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, and the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a random access memory, or the like. Specifically, for example: the processing unit or processor may be a central processing unit, a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, a transistor logic device, a hardware component, or any combination thereof. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

When implemented in software, the method steps described in the above embodiments may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the application to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid State Disk (SSD)), among others.

Claims

1. An optical communication system, comprising a main optical line terminal OLT, a first optical network unit ONU, a second ONU, a first optical splitter and a second optical splitter, wherein the first ONU comprises a first sub-OLT and a first sub-ONU, a first port of the first optical splitter is connected to the main OLT, a second port of the first optical splitter is connected to the first sub-OLT, a third port of the first optical splitter is connected to the first sub-ONU, a fourth port of the first optical splitter is connected to one port of the second optical splitter, and another port of the second optical splitter is connected to the second ONU;

the main OLT is used for sending a target optical signal;

the first sub-ONU is configured to receive the target optical signal, and send first indication information to the first sub-OLT if optical power of the target optical signal received by the first sub-ONU is lower than a first threshold, and/or if optical power of the target optical signal received by the first sub-ONU is reduced and an optical power variation value is greater than a second threshold;

the first sub OLT is used for sending a first optical signal according to the first indication information;

the second ONU is used for receiving the first optical signal.

2. The optical communication system according to claim 1, wherein the first port of the first optical splitter is configured to input the target optical signal, the third port of the first optical splitter is configured to output the target optical signal to the first sub-ONU, and the fourth port of the first optical splitter is configured to output the target optical signal to the second ONU;

if the optical power of the target optical signal received by the first sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is reduced and the optical power variation value is greater than the second threshold, the second port of the first optical splitter is configured to input the first optical signal, the third port of the first optical splitter is configured to output the first optical signal to the first sub-ONU, and the fourth port of the first optical splitter is configured to output the first optical signal to the second ONU.

3. The optical communication system according to claim 1 or 2, wherein the optical communication system further comprises a third optical splitter and a third ONU, wherein the second ONU comprises a second sub OLT and a second sub ONU, the first port of the second optical splitter is connected to the fourth port of the first optical splitter, the second port of the second optical splitter is connected to the second sub OLT, the third port of the second optical splitter is connected to the second sub ONU, the fourth port of the second optical splitter is connected to one of the ports of the third optical splitter, and the other port of the third optical splitter is connected to the third ONU;

the second sub-ONU is configured to receive the target optical signal, and if the optical power of the target optical signal received by the second sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the second sub-ONU is reduced and the optical power variation value is greater than the second threshold, the second sub-ONU is configured to send second indication information to the second sub-OLT;

the second sub OLT is configured to send a second optical signal according to the second indication information;

the third ONU is used for receiving the second optical signal.

4. The optical communication system of claim 3, wherein the main OLT is further configured to send a notification message before the main OLT sends the target optical signal;

if the optical power of the target optical signal received by the first sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is weakened and the optical power variation value is greater than the second threshold, the first sub-ONU is configured to determine a first time period according to the notification message, where the first indication information includes the first time period;

the first sub OLT is specifically configured to send the first optical signal at the first time period according to the first indication information;

if the optical power of the target optical signal received by the second sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the second sub-ONU is weakened and the optical power variation value is greater than the second threshold, the second sub-ONU is configured to determine a second time period according to the notification message, where the second indication information includes the second time period;

the second sub OLT is specifically configured to send the second optical signal in the second time period according to the second indication information.

5. The optical communication system of claim 4, wherein the notification message is further configured to indicate a total duration of the first time period and the second time period, and wherein the first time period and the second time period do not overlap;

if the second sub-ONU can only receive the second optical signal within the total duration, the second sub-ONU is configured to send third indication information to the second sub-OLT;

the second sub OLT is configured to continuously send the second optical signal according to the third indication information.

6. The optical communication system of claim 4, wherein there is an overlapping period of time between the first period of time and the second period of time;

if the second sub-ONU can recognize the second optical signal in the second time period, the second sub-ONU is configured to send third indication information to the second sub-OLT;

7. The optical communication system according to any of claims 1 to 6, wherein the first sub OLT is further configured to receive an upstream optical signal from the second ONU.

8. The optical communication system according to any one of claims 1 to 7, wherein the wavelength of the target optical signal is the same as the wavelength of the first optical signal.

9. The optical communication system according to any of claims 1 to 8, wherein the target optical signal comprises a target identification of the main OLT, and wherein the first optical signal comprises a first identification of the first sub-OLT.

10. A method for transmitting an optical signal, comprising:

a first optical network unit ONU detects a target optical signal from a main optical line terminal OLT through a first sub-ONU, wherein the first ONU comprises the first sub-ONU and a first sub-OLT;

and if the optical power of the target optical signal received by the first sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is weakened and the optical power variation value is greater than the second threshold, the first ONU sends the first optical signal through the first sub-OLT.

11. The method according to claim 10, wherein a first optical splitter is connected between the first ONU and the main OLT, a first port of the first optical splitter is connected to the main OLT, a second port of the first optical splitter is connected to the first sub-OLT, a third port of the first optical splitter is connected to the first sub-ONU, a fourth port of the first optical splitter is connected to a first port of a second optical splitter, and a second port of the second optical splitter is connected to the second ONU.

12. The method according to claim 11, wherein a first port of the first optical splitter is configured to input the target optical signal, a third port of the first optical splitter is configured to output the target optical signal to the first sub-ONU, and a fourth port of the first optical splitter is configured to output the target optical signal to the second ONU;

if the optical power of the target optical signal received by the first sub-ONU is lower than the first threshold, and/or if the optical power of the target optical signal received by the first sub-ONU is weakened and the optical power variation value is greater than the second threshold, the second port of the first optical splitter is used for inputting the first optical signal, the third port of the first optical splitter is used for outputting the first optical signal to the first sub-ONU, and the fourth port of the first optical splitter is used for outputting the first optical signal to the second ONU.

13. The method according to any of claims 10-12, wherein before the first ONU detects the target optical signal from the main OLT through the first sub-ONU, the method further comprises:

the first ONU receives a notification message from the main OLT;

the first ONU transmitting the first optical signal through the first sub OLT includes:

the first ONU transmits the first optical signal at a first period indicated by the notification message through the first sub-OLT.

14. The method according to claim 13, wherein if the first sub-ONU cannot detect the target optical signal, the method further comprises:

the first ONU detects the first optical signal and a second optical signal from a third ONU through a first sub-ONU, the third ONU is used for sending the second optical signal in a second time interval, wherein the first time interval and the second time interval are not overlapped, and the notification message is also used for indicating the total time length of the first time interval and the second time interval;

and if the first sub-ONU can only receive the first optical signal within the total time length, the first ONU continuously sends the first optical signal through the first sub-OLT.

15. The method according to claim 13, wherein if the first sub-ONU cannot detect the target optical signal, the method further comprises:

the first ONU detects the first optical signal and a second optical signal from a third ONU through a first sub-ONU, the third ONU is used for transmitting the second optical signal in a second time interval, wherein, the first time interval and the second time interval have an overlapped time interval;

if the first sub-ONU can recognize the first optical signal in the first time period, the first ONU continuously transmits the first optical signal through the first sub-OLT.

16. The method of any one of claims 10 to 15, wherein the wavelength of the target optical signal is the same as the wavelength of the first optical signal.

17. The method according to any of the claims 10 to 16, wherein the target optical signal comprises a target identification of the main OLT and the first optical signal comprises a first identification of the first sub-OLT.

18. A method for transmitting an optical signal, comprising:

a main OLT sends a notification message to a first ONU and a second ONU, the first ONU comprises a first sub OLT and a first sub ONU, the second ONU comprises a second sub OLT and a second sub ONU, a first optical splitter is connected between the first ONU and the main OLT, a first port of the first optical splitter is connected with the main OLT, a second port of the first optical splitter is connected with the first sub OLT, a third port of the first optical splitter is connected with the first sub ONU, a fourth port of the first optical splitter is connected with a first port of a second optical splitter, a second port of the second optical splitter is connected with the second sub OLT, and a third port of the second optical splitter is connected with the second sub ONU;

the main OLT sends a target optical signal to the first ONU and the second ONU, and if the first sub-ONU and the second sub-ONU cannot detect the target optical signal from the main OLT, the notification message is used to instruct the first sub-OLT to send a first optical signal in a first time period, and the notification message is used to instruct the second sub-OLT to send a second optical signal in a second time period.

19. An optical network unit, ONU, comprising: a sub OLT unit and a sub ONU unit;

the sub ONU unit is used for detecting a target optical signal from the main OLT;

if the optical power of the target optical signal received by the sub-ONU unit is lower than the first threshold, and/or if the optical power of the target optical signal received by the sub-ONU unit is weakened and the optical power variation value is greater than the second threshold, the sub-ONU unit is configured to send indication information to the sub-OLT unit;

and the sub OLT unit is used for sending a first optical signal according to the indication information.

20. The ONU of claim 19, wherein a first optical splitter is connected between the ONU and the main OLT, wherein a first port of the first optical splitter is connected to the main OLT, wherein a second port of the first optical splitter is connected to the sub-OLT unit, wherein a third port of the first optical splitter is connected to the sub-ONU unit, wherein a fourth port of the first optical splitter is connected to a first port of a second optical splitter, and wherein a second port of the second optical splitter is connected to a second ONU.

21. The ONU of claim 20, wherein the first port of the first optical splitter is configured to input the target optical signal, wherein the third port of the first optical splitter is configured to output the target optical signal to the sub-ONU unit, and wherein the fourth port of the first optical splitter is configured to output the target optical signal to the second ONU unit;

if the optical power of the target optical signal received by the sub-ONU unit is lower than the first threshold, and/or if the optical power of the target optical signal received by the sub-ONU unit is reduced and the optical power variation value is greater than the second threshold, the second port of the first optical splitter is configured to input the first optical signal, the third port of the first optical splitter is configured to output the first optical signal to the sub-ONU unit, and the fourth port of the first optical splitter is configured to output the first optical signal to the second ONU unit.

22. The ONU of any one of claims 19-21, wherein before the sub-ONU unit is configured to detect a target optical signal from a main OLT, the sub-ONU unit is further configured to receive a notification message from the main OLT;

if the sub-ONU unit cannot receive the target optical signal, the sub-ONU unit is used for determining a first time period according to the notification message, and the indication information comprises the first time period;

the sub OLT unit is specifically configured to send the first optical signal at the first time period according to the indication information.

23. The ONU of claim 22, wherein if the sub-ONU unit cannot detect the target optical signal, the sub-ONU unit is further configured to detect the first optical signal and a second optical signal from a third ONU, and wherein the third ONU is configured to transmit the second optical signal for a second time period, wherein the first time period and the second time period do not overlap, and wherein the notification message is further configured to indicate a total duration of the first time period and the second time period;

and if the sub ONU unit can only receive the first optical signal within the total time length, the sub OLT unit continuously sends the first optical signal.

24. The ONU of claim 22, wherein if the sub-ONU unit cannot detect the target optical signal, the sub-ONU unit is further configured to detect the first optical signal and a second optical signal from a third ONU, and wherein the third ONU is configured to transmit the second optical signal for a second time period, wherein there is an overlapping time period between the first time period and the second time period;

if the sub-ONU unit can recognize the first optical signal in the first period, the sub-OLT unit continuously transmits the first optical signal.

25. The ONU of any one of claims 19-24, wherein the wavelength of the target optical signal is the same as the wavelength of the first optical signal.

26. The ONU of any one of claims 19-25, wherein the target optical signal comprises a target identification of the main OLT, and wherein the first optical signal comprises a first identification of the sub-OLT units.

27. An Optical Line Terminal (OLT) comprising a processor and an optical transceiver, the processor and the optical transceiver being interconnected by a line, the processor being configured to perform the method of claim 18.

28. The OLT of claim 27, wherein the OLT further comprises a memory, and wherein the processor invokes program code in the memory to perform the method of claim 18.