CN115882951A - Detection method of relay equipment, optical line terminal and passive optical network system - Google Patents

Abstract

The embodiment of the application discloses a detection method of a relay device, an optical line terminal and a passive optical network system, which are used for improving the detection accuracy of the relay device. The method in the embodiment of the application comprises the following steps: the second device adjusts the transmitting optical power, and respectively transmits a first message and a second message to the first device based on different transmitting optical powers, and the first device detects a first receiving optical power when receiving the first message and a second receiving optical power when receiving the second message. And judging whether a relay device is connected between the first device and the second device according to the change condition of the second receiving optical power compared with the first receiving optical power.

Description

Detection method of relay equipment, optical line terminal and passive optical network system

Technical Field

The embodiment of the application relates to the field of communication, in particular to a detection method of a relay device, an optical line terminal and a passive optical network system.

Background

A Passive Optical Network (PON) is composed of an Optical Line Terminal (OLT) at the side of a central office (central office) and an Optical Network Unit (ONU) or an Optical Network Terminal (ONT) at the side of a user. The OLT provides a network side interface for the PON system, and the ONU provides a user side interface for the PON system. In the existing network, when the optical path from the OLT to the ONU is longer or the splitting ratio is too large, the optical path attenuation is larger, so that the receiving optical power of the OLT/ONU is not enough to enable the ONU to normally open the service, in the optical path from the OLT to the ONU, the repeater equipment for remote relaying the optical path can be adopted for carrying out remote relaying on the optical path by re-amplification, reshaping and timing (re-amplification, re-mapping, re-timing, 3R), so that the receiving optical power of the OLT/ONU can be in the normal receiving sensitivity range of the OLT/ONU optical module, and the ONU can normally open the service on the OLT.

When a fault occurs in the PON, it is necessary to detect and locate each passive optical network device in the PON. If the optical path from the OLT to the ONU is connected with a 3R remote relay device, the 3R remote relay device also needs to be detected and checked. For how to determine whether the optical path from the OLT to the ONU is connected to the 3R remote relay device, the optical path attenuation may be estimated. Specifically, the splitting ratio of the optical path is estimated according to the number of the on-line ONUs, the expected receiving optical power of the OLT/ONU is estimated according to the estimated splitting ratio and the optical fiber distance, and if the actual receiving optical power of the OLT/ONU is greater than the expected receiving optical power of the OLT/ONU, the 3R remote relay equipment is connected to the optical path.

However, the number of the online ONUs cannot truly reflect the actual splitting ratio and the optical path topology of the customer, so that the estimated optical path attenuation is inaccurate, and further, the misjudgment on whether the 3R remote relay equipment is connected or not is caused.

Disclosure of Invention

The embodiment of the application provides a detection method of a relay device, an optical line terminal and a passive optical network system, and aims to solve the problem that whether the relay device exists between the passive optical line terminal and the optical network device or not can not be detected accurately and with low cost.

A first aspect of an embodiment of the present application provides a method for detecting a relay device, where the method is applied to an optical line terminal OLT, and the method includes: the OLT acquires first receiving optical power when the first equipment receives a first message, wherein the first message is sent to the first equipment by the second equipment based on first sending optical power; the OLT acquires second receiving optical power when the first equipment receives a second message, wherein the second message is sent to the first equipment by the second equipment based on second sending optical power, and a first difference value between the first sending optical power and the second sending optical power is larger than a first threshold value; and the OLT judges whether the relay equipment is connected between the first equipment and the second equipment or not according to the first receiving optical power and the second receiving optical power. The first device is an OLT, the second device is an optical network unit ONU, and the ONU refers to an optical network terminal ONT capable of directly providing a user port function and an ONU providing a user side interface in this application. Or the first device is an ONU and the second device is an OLT. A relay device is a device in an optical path that can perform operations such as re-amplification of signals. And acquiring first receiving optical power and second receiving optical power when the first equipment receives the first message and the second message respectively by changing the transmitting optical power of the second equipment. Since the transmitting optical power of the relay device is stable, when the relay device is connected between the first device and the second device, the receiving optical power of the first device does not change as the transmitting optical power of the second device changes; when the relay device is not connected between the first device and the second device, the received optical power of the first device may vary with the transmitted optical power of the second device. Therefore, whether the relay equipment is connected between the first equipment and the second equipment can be accurately judged according to the change condition between the first receiving optical power and the second receiving optical power, and therefore the manpower and material resource investment of manual investigation is reduced.

In a first possible implementation manner of the first aspect, the step of determining whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power includes: the OLT calculates a second difference between the first received optical power and the second received optical power and compares the second difference with a second threshold. The second threshold is smaller than the first threshold so as to avoid misjudgment caused by measurement errors of the first equipment. When the second difference is greater than a second threshold, the OLT can determine that the relay device is not connected between the first device and the second device; and when the second difference is smaller than or equal to the second threshold, the OLT determines that the relay equipment is connected between the first equipment and the second equipment. By comparing the second difference with the second threshold, the OLT can determine whether the received optical power is stable or varies with the transmitted optical power, thereby accurately determining whether the relay device is connected between the first device and the second device.

In a second possible implementation manner of the first aspect, the step of determining whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power includes: the OLT acquires a first difference and a second difference between the first received optical power and the second received optical power, and calculates a third difference between the first difference and the second difference. And the OLT compares the third difference value with a third threshold value, wherein the third threshold value is smaller than the first threshold value. When the third difference is smaller than a third threshold value, the OLT determines that the relay equipment is not connected between the first equipment and the second equipment; and when the third difference is larger than or equal to the third threshold, the OLT determines that relay equipment is connected between the first equipment and the second equipment. And the OLT judges whether the received optical power changes correspondingly with the change of the transmitted optical power by comparing the third difference with the third threshold value, so as to accurately judge whether the relay equipment is connected between the first equipment and the second equipment.

In a third possible implementation manner of the first aspect, the first device is an OLT, and the second device is an ONU. In this implementation, the OLT controls the ONU to change the transmission optical power, and the OLT measures the reception optical power corresponding to the transmission optical power.

With reference to the third possible implementation manner of the first aspect, before obtaining the first received optical power when the first device receives the first message, the method includes: the first device sends a third message to the second device, which sends the first message to the first device in response to the third message. The first message may carry the first transmitted optical power. The first device instructs the second device to send the first message to the first device through the third message so that the first device can measure the first received optical power when receiving the first message.

With reference to the third possible implementation manner of the first aspect, before the sending, by the first device, the third message to the second device, the method includes: the first device transmits a power adjustment message to the second device, and the second device adjusts the transmission optical power to the first transmission optical power in response to the power adjustment message. The first device separates two messages sent to the second device, so that the second device can have time to adjust the sending optical power to a stable state, the first sending optical power and the first receiving optical power are accurate, and the accuracy of the scheme is improved.

With reference to the third possible implementation manner of the first aspect, before the obtaining the second received optical power when the first device receives the second message, the method includes: the first device sends a power adjustment message to the second device, and the second device adjusts the sending light power from the first sending light power to the second sending light power according to the power adjustment message. The first device continues to send the third message to the second device, which sends the second message to the first device in response to the third message. The second message may carry a second transmitted optical power. The second device separates two messages sent to the first device, so that the first device can have time to adjust the sending optical power to a stable state, the second sending optical power and the second receiving optical power are accurate, and the accuracy of the scheme is improved.

In a fourth possible implementation manner of the first aspect, the first device is an ONU, and the second device is an OLT. In this implementation, the OLT changes the transmission optical power, and the ONU measures the reception optical power corresponding to the transmission optical power.

With reference to the fourth possible implementation manner of the first aspect, the obtaining the first received optical power when the first device receives the first message includes: the second device sends a first message to the first device, and the first device returns a first response message including the first received optical power to the second device in response to the first message. The second device receives the first response message and obtains the first received optical power from the first response message.

With reference to the fourth possible implementation manner of the first aspect, the obtaining the second received optical power when the first device receives the second message includes: and the second equipment sends a second message to the first equipment, and the first equipment returns a second response message of second received optical power to the second equipment in response to the second message. The second device receives the second response message and obtains a second received optical power from the second response message.

With reference to the fourth possible implementation manner of the first aspect, the first response message is sent by the first device based on a third sending power, the second response message is sent by the first device based on a fourth sending power, and a fourth difference between the fourth sending optical power and the third sending optical power is greater than a fourth threshold, and the method further includes: the second device acquires a third received optical power when receiving the first response message and a fourth received optical power when receiving the second response message. The step of judging whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power includes: and the second equipment judges whether the relay equipment is connected between the first equipment and the second equipment according to the first receiving optical power, the second receiving optical power, the third receiving optical power and the fourth receiving optical power. The second device obtains two groups of received optical power data through two times of interaction with the first device, so that the accuracy of detection on the relay device can be improved, and the detection efficiency can also be improved.

With reference to the fourth possible implementation manner of the first aspect, the determining, by the second device, whether a relay device is connected between the first device and the second device according to the first received optical power, the second received optical power, the third received optical power, and the fourth received optical power includes: the second device calculates a second difference between the first received optical power and the second received optical power, and a fifth difference between the third received optical power and the fourth received optical power. And the second equipment respectively compares the second difference value with a second threshold value, the magnitude of a fifth difference value with a fifth threshold value, and the second threshold value and the fifth threshold value are both smaller than the first threshold value. When the second difference is greater than the second threshold and the fifth difference is greater than the fifth threshold, indicating that the two groups of received optical powers change along with the adjustment of the transmitted optical power, it may be determined that the relay device is not connected between the first device and the second device; when the second difference is less than or equal to the second threshold and the fifth difference is less than or equal to the fifth threshold, which indicates that neither of the two sets of received optical powers changes with the adjustment of the transmitted optical power, it may be determined that a relay device is connected between the first device and the second device. Whether the relay equipment is connected or not is judged based on the two groups of receiving optical powers, and the accuracy of detection on the relay equipment can be improved.

A second aspect of the embodiments of the present application provides an OLT, where the OLT includes a processor and an optical transceiver, the processor is connected to the optical transceiver, and the processor is configured to execute instructions, and when the instructions are executed, the OLT executes any method of the first aspect and possible implementation manners thereof.

A third aspect of embodiments of the present application provides a passive optical network system including an optical distribution network, a plurality of optical network units, and an optical line terminal as in the second aspect, the optical line terminal being connected to the plurality of optical network units through the optical distribution network.

Drawings

Fig. 1 is a schematic structural diagram of a passive optical network system according to an embodiment of the present application;

fig. 2 is a schematic flowchart of a first embodiment of a detection method for a relay device according to an embodiment of the present application;

fig. 3 is an interaction flow diagram of a second embodiment of a detection method for a relay device according to an embodiment of the present application;

fig. 4 is an interaction flow diagram of a third embodiment of a detection method for a relay device according to an embodiment of the present application;

fig. 5 is an interaction flow diagram of a fourth embodiment of a detection method for a relay device according to an embodiment of the present application;

fig. 6 is a schematic structural diagram of an embodiment of an optical line terminal according to an embodiment of the present application;

fig. 7 is a schematic structural diagram of another embodiment of an optical line terminal according to an embodiment of the present application.

Detailed Description

The embodiment of the application provides a detection method of a relay device, an optical line terminal and a passive optical network system, which are used for accurately detecting whether the relay device is connected in the passive optical network system at low cost.

The technical scheme of the embodiment of the invention can be applied to various Passive Optical Networks (PONs), such as: gigabit Passive Optical Network (GPON), ethernet Passive Optical Network (EPON), ten gigabit passive optical network (XG-PON), ten gigabit symmetric passive optical network (XGs-PON), next Generation Passive Optical Network (NGPON), and the like.

As shown in fig. 1, fig. 1 is a schematic structural diagram of a passive optical network system according to an embodiment of the present application. In this embodiment, the PON system 100 includes at least one Optical Line Terminal (OLT) 110, at least one Optical Distribution Network (ODN) 120, and a plurality of Optical Network Units (ONUs)/Optical Network Terminals (ONTs) 130. It is understood that the number of ONUs in fig. 1 is only an example, and is not a limitation to the present application.

The OLT110 is a central office device of the PON system 100 and is responsible for managing, monitoring and maintaining the entire PON system 100. The OLT110 provides a network-side interface for the PON system 100 to connect to one or more ODNs 120. The ONU130 is a remote device of the PON system 100, and is responsible for the access function of users and services. The ONU/ONT130 provides a user-side interface for the PON system 100 to connect to the ODN120. If the ONU130 directly provides the user port function, it is called ONT. For convenience of description, the ONU130 mentioned below refers to an ONT that can directly provide a user port function and an ONU that provides a user side interface. The ODN120 is a network composed of optical fibers and passive optical splitting devices, and is used for connecting the OLT110 and the ONUs 130, and distributing or multiplexing data signals between the OLT110 and the ONUs 130.

In a scenario that optical fiber communication needs to be extended, in order to compensate for loss of optical signals of an optical cable line and eliminate signal distortion and noise influence, a relay device (not shown) may be used in the optical path to perform remote relay on the optical path, so that the received optical power of the OLT110 or the ONU130 is within a normal receiving sensitivity range of an optical module of the OLT110 or the ONU130 without changing an original topology of the optical path, and thus the ONU130 may normally open a service on the OLT110. The relay device may be a re-amplifying and re-shaping (2R) relay device, or may also be a re-amplifying, re-shaping, and re-timing (3R) device to compensate for optical power attenuation of an optical signal in an optical path.

Specifically, the relay device is connected between the OLT110 and the ONUs 130. The relay devices are connected to the OLT110 and the ONUs 130 via optical fibers, respectively. The relay device includes a User Network Interface (UNI) optical module and a network to network interface (NNI) optical module. The UNI optical module is configured to transmit optical signals to the ONUs 130, and the NNI optical module is configured to transmit optical signals to the OLT110. The relay device adopts an optical-electrical-optical relay method, that is, an optical signal received from the OLT110 or the ONU130 is converted into an electrical signal, the electrical signal is re-amplified, re-shaped, re-timed and re-converted into an optical signal, and the optical signal is transmitted to the ONU130 or the OLT110 through the UNI optical module or the NNI optical module. Because the transmitting optical power of the UNI/NNI optical module of the relay device is stable, a relatively weak optical signal can be changed into a strong optical signal for retransmission after being subjected to relay regeneration transmission of the relay device, and further the optical power attenuation of optical path transmission is compensated. The transmission optical power of the UNI/NNI optical module of the relay device is not affected by the signal intensity of the received optical signal.

When the PON system 100 is overhauled, it is necessary to determine whether a relay device is connected between the OLT110 and the ONU 130. The manual examination along the optical path is time-consuming, labor-consuming and high in cost, and the estimated splitting ratio and the optical fiber distance are used for estimating the expected receiving optical power of the OLT110 or the ONU130 to judge whether the relay equipment exists or not, so that the misjudgment can be caused by inaccurate estimated splitting ratio.

Therefore, based on the passive optical network system 100, the present application provides the following embodiments to accurately and cost-effectively detect whether a relay device is connected between the OLT and the ONU.

As shown in fig. 2, fig. 2 is a flowchart illustrating a first embodiment of a method for detecting a relay device according to an embodiment of the present application. The embodiment comprises the following steps:

s201: the method comprises the steps of obtaining first receiving optical power when first equipment receives a first message, wherein the first message is sent to the first equipment by second equipment based on first sending optical power.

The first device may be an OLT, and the second device is an ONU. Or the first device is an ONU and the second device is an OLT. The first device and the second device each have an optical transceiver capable of transmitting or receiving the first message in the form of an optical signal.

The first transmitting optical power is an output optical power of the optical transceiver of the second device when transmitting the first message, and the first transmitting optical power is in direct proportion to a signal strength of the first message. The first receiving optical power is an optical power of the first device when the optical transceiver receives the first message, and the magnitude of the first receiving optical power is in direct proportion to the signal strength of the first message when the first message is received.

S202: and acquiring a second receiving optical power when the first device receives a second message, wherein the second message is sent to the first device by the second device based on a second sending optical power, and a first difference value between the first sending optical power and the second sending optical power is larger than a first threshold value.

The second device changes the transmission optical power and transmits a second message to the first device such that the signal strength of the second message is different from the signal strength of the first message. The second sending optical power may be greater than the first sending optical power or smaller than the first sending optical power, so that the signal strength of the second message can ensure that the optical module of the relay device or the first device can receive and normally work, and the application is not limited thereto.

In a case where the relay device is not connected between the first device and the second device, a change in the second transmission optical power as compared to the first transmission optical power causes a change in the signal strength of the second message, and the second reception optical power at the time of receiving the second message by the first device also changes. When the relay device is connected between the first device and the second device, the second message is re-amplified by the relay device and then transmitted to the first device, and since the optical power transmitted by the relay device is stable, and the optical power transmitted by the relay device when transmitting the second message to the first device is different from the optical power transmitted by the relay device when transmitting the first message, the second received optical power when the first device receives the second message is substantially the same as the first received optical power when receiving the first message, and the received optical power of the first device does not change with the change of the optical power transmitted by the second device.

It will be appreciated that in the case where the first device and the second device are connected to a relay device, the first received optical power and the second received optical power may be the same or different, but the received optical power will not vary much due to some measurement error of the first device and jitter of the signal during transmission. In this embodiment, in order to reduce the influence of measurement errors and the like, a first difference between the first transmitted optical power and the second transmitted optical power may be greater than a first threshold, where the first threshold is greater than an error range allowed when the first device receives different messages. Thus, when the second received optical power is different from the first received optical power, it can be determined whether it is caused by a measurement error or a change in the transmitted optical power of the second device.

Illustratively, the first threshold may be 2 decibel-milliwatts (dBm), 3dBm, 5dBm, or 7dBm, among others. In practical application, the first threshold may be determined according to the maximum transmitting optical power and the minimum transmitting optical power of the second device, and the receiving sensitivity and the overload optical power of the second device, so that it is sufficient to ensure that the first device and the second device/the relay device operate normally.

S203: and judging whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power.

When the first transmitting optical power and the second transmitting optical power are different, whether the relay device is connected between the first device and the second device can be accurately judged according to the change condition of the second receiving optical power compared with the first receiving optical power.

There are various ways of determining whether the relay device exists according to the first transmitting optical power and the second transmitting optical power.

For example, it may be determined whether or not the relay apparatus is present from only the second difference value between the first received optical power and the second received optical power. Specifically, a second difference between the first received optical power and the second received optical power is calculated, and it is determined whether the second difference is greater than a second threshold. The second threshold is greater than or equal to the maximum value of the detection error range allowed by the first device, and the second threshold is smaller than the first threshold, so that the accuracy of the judgment result is improved. Illustratively, the second threshold may be 1dBm, 1.2dBm, 1.5dBm, or the like. The second threshold may be specifically adjusted according to the first threshold, for example, the first threshold is directly proportional to the second threshold, and certainly, the first threshold may also be a fixed value and does not change with the change of the second threshold, which is not limited in this application.

When the second difference is greater than the second threshold, it is indicated that the variation between the second received optical power and the first received optical power exceeds the error range and is affected by the variation of the transmitted optical power, and it can be determined that the relay device is not connected between the first device and the second device. When the second difference is smaller than or equal to the second threshold, it is indicated that the second received optical power is the same as the first received optical power, or the change between the second received optical power and the first received optical power is affected by measurement errors and other factors, and the second received optical power is not affected by the second transmitted optical power, it can be determined that a relay device is connected between the first device and the second device.

Also for example, it may be determined whether or not a relay apparatus is present based on the first difference value and the second difference value. Specifically, a first difference value and a second difference value between the first received optical power and the second received optical power are obtained. And calculating a third difference value between the first difference value and the second difference value, and judging the size of the third difference value and a third threshold value. Wherein the third threshold is smaller than the first threshold, and the third threshold is larger than the maximum value of the error range allowed by the second device. Illustratively, the third threshold may be 1dBm, 1.2dBm, 1.5dBm, or the like. Generally, in the case where no relay device is connected between the first device and the second device, the first difference is substantially equal to the second difference, such that the third difference is equal to or about 0dBm; in the case where a relay device is connected between the first device and the second device, the first difference is large, and the second difference is less than or equal to about 0dBm, so the third difference is also large.

When the third difference is smaller than the third threshold, it is determined that the first difference and the second difference are relatively close, and the second receiving power is affected by the second transmitting power, and it can be determined that the relay device is not connected between the first device and the second device. When the third difference is greater than or equal to the third threshold, it is determined that the relay device is connected between the first device and the second device if the second reception power is the same as or almost the same as the first reception power and the second reception power is not affected by the second transmission power.

It will be appreciated that to facilitate comparison between the first difference, the second difference, and the third difference, the first difference, the second difference, and the third difference may each be absolute values.

Of course, in addition to determining whether or not there is a relay device between the first device and the second device based on the first difference value or the like, the determination may be made based on a first ratio of the first received optical power to the second received optical power. When the relay device is present, the first received optical power and the second received optical power are the same or substantially the same, and the first ratio is around 1. And further calculating a sixth difference value between the first ratio and 1, and judging whether the sixth difference value is greater than a sixth threshold value. If the sixth difference is smaller than the sixth threshold, determining that relay equipment exists between the first equipment and the second equipment; and if the sixth difference is greater than or equal to the sixth threshold, determining that no relay device exists between the first device and the second device. Wherein, the sixth threshold value may be 0.1, 0.2, 0.25, etc.

In other embodiments, the determination may be further performed according to a first ratio and a second ratio between the first transmitted optical power and the second transmitted optical power. Specifically, for example, whether the second received optical power is affected by the second transmitted optical power is determined according to a difference or a ratio between the first ratio and the second ratio, so as to determine whether the relay device is connected between the first device and the second device, which is not described herein again.

In order to improve the detection accuracy of the relay device, S201 to S202 may be performed multiple times, and the average values of the first received optical power and the second received optical power are taken and substituted into S203 to calculate and determine whether the relay device is connected between the first device and the second device.

In the embodiment of the present application, by changing the transmission optical power of the second device, the first receiving optical power and the second receiving optical power when the first device receives the first message and the second message, respectively, are obtained. Since the transmission optical power of the relay device is stable, when the relay device is connected between the first device and the second device, the received optical power does not change with the change of the transmission optical power; when the relay device is not connected between the first device and the second device, the received optical power glow varies with a variation in the transmitted optical power. Therefore, whether the relay equipment is connected between the first equipment and the second equipment or not can be accurately judged according to the change condition between the first received optical power and the second received optical power, and therefore the manpower and material resource investment of manual investigation is reduced.

As shown in fig. 3, fig. 3 is an interaction flow diagram of a second embodiment of a detection method for a relay device according to an embodiment of the present application. In this embodiment, the first device is an OLT, and the second device is an ONU. The transmitting optical power is changed by the ONU, and the OLT measures the receiving optical power. The main execution body of the embodiment is the OLT. The embodiment comprises the following steps:

s301: the OLT sends a third message to the ONU.

And the third message is used for instructing the ONU to send the first message to the OLT. The third message may specifically instruct the ONU to return the first message carrying the first transmitted optical power. The third message may not indicate what kind of content is carried by the first message returned by the ONU, that is, the first message may carry the random parameter, or the third message only needs to indicate the ONU to send the first message to the OLT, so that the OLT can receive the first message.

The ONU generates a first message in response to the third message and transmits the first message to the OLT based on the first transmission optical power. If the third message indicates that the first message carries the first sending light power, the first message includes the first sending light power.

Wherein the first transmitted optical power may be OLT indication adjusted. Specifically, the OLT sends a power adjustment message to the ONU before sending the third message to the ONU, where the power adjustment message instructs the ONU to adjust the transmission optical power to the first transmission optical power. The power adjustment message may instruct the ONU to increase or decrease the transmission optical power on the basis of the initial transmission optical power to adjust to the first transmission optical power, for example, the power adjustment message instructs the transmission optical power of the ONU to increase by 2dBm, 3dBm, 5dBm, or 7dBm, etc., or instructs the transmission optical power of the ONU to decrease by 2dBm, 3dBm, 5dBm, or 7dBm, etc. The power adjustment message may also instruct the ONU to adjust to a specific transmitted optical power, i.e. the first transmitted optical power is a value specified by the OLT, e.g. the power adjustment message instructs the ONU to adjust the transmitted optical power to 5dBm.

In the GPON/XG-PON/XGs-PON, the third message and the power adjustment message may adopt an optical network unit management and control interface (OMCI) message. The OMCI transmits the OMCI message by establishing a proprietary transmission channel between the OLT and the ONU. And when the ONU registers with the OLT, an OMCI channel is established, the OMCI is a master-slave management protocol, the OLT is a master device, the ONT is a slave device, and the OLT controls a plurality of ONU devices below the OLT through the OMCI channel. The message interaction between the OLT and the ONU is completed by adopting the Test operation interaction of an ANI-G entity defined by ITU-T G.988 standard established by the International Telecommunication Union (ITU). And the ONU analyzes the parameter value of the ONU optical power adjustment mark after receiving the power adjustment message sent by the OLT according to the ITU-TG.988 standard definition message format, and performs the sending optical power adjustment according to the parameter value.

In the EPON/10GEPON, the third message and the power adjustment message may be operation and maintenance administration (OAM) messages. The message format of the third message and the power adjustment message complies with the IEEE 802.3 standard set by the Institute of Electrical and Electronics Engineers (IEEE).

Of course, the OLT may not adjust the transmission optical power of the ONU before transmitting the third message to the ONU, and the first transmission optical power may be the currently set transmission optical power of the ONU.

S302: the OLT acquires first receiving optical power when receiving the first message.

And the OLT receives a first message returned by the ONU in response to the third message, and measures the first receiving optical power when receiving the first message so as to acquire the first receiving optical power.

And if the third message indicates that the ONU returns a first message carrying the first sending light power, the OLT analyzes the first message to obtain the first sending light power.

S303: the OLT sends a power adjustment message to the ONU.

And after receiving the first message, the OLT sends a power adjustment message to the ONU so as to control the sending optical power of the ONU to be adjusted from the first sending optical power to the second sending optical power. And the ONU adjusts the sending optical power according to the power adjustment message, wherein the adjusted sending optical power is the second sending optical power. A first difference between the second transmitted optical power and the first transmitted optical power is greater than a first threshold.

The format and function of the power adjustment message in this step are consistent with those of the power adjustment message described in S301, and therefore are not described herein again.

S304: the OLT sends a third message to the second device.

And the third message is used for instructing the ONU to send a second message to the OLT. The format and function of the third message in this step are consistent with those of the third message described in S301, and are not described herein again.

Since the ONU needs a certain time to adjust the transmission optical power, the OLT may send a third message to the ONU after sending the preset time length of the power adjustment message to the ONU, so that the second transmission optical power is accurate and stable. The preset time duration is, for example, 10 seconds, 12 seconds, 15 seconds, 20 seconds, or the like, and in practical application, it is only required to ensure that the third message is sent after the sending optical power of the ONU is adjusted, and the specific preset time duration is not limited in this application.

S305: the OLT acquires second receiving optical power when receiving the second message.

And the OLT receives a second message returned by the ONU in response to the third message and measures a second receiving optical power when receiving the second message.

And if the third message indicates that the ONU returns a second message carrying the second sending optical power, the OLT analyzes the second message to obtain the second sending optical power.

S306: and the OLT judges whether relay equipment is connected between the OLT and the ONU according to the first receiving optical power and the second receiving optical power.

And after determining that a first difference value between the first transmitting optical power and the second transmitting optical power is larger than a first threshold value according to the first transmitting optical power and the second transmitting optical power, the OLT judges whether relay equipment is connected between the OLT and the ONU according to the first receiving optical power and the second receiving optical power.

S203 is referred to according to a specific manner of whether the relay device is connected between the first receiving optical power and the second receiving optical power OLT and the ONU, and therefore, details are not described herein.

In this embodiment, the OLT controls the ONU to change the transmission optical power by sending the power adjustment message to the ONU, so that the ONU sends the first message and the second message to the OLT under different transmission optical powers, the OLT measures the first receiving optical power when receiving the first message and the second receiving optical power when receiving the second message, and determines whether the relay device is connected between the OLT and the ONU by determining whether the first receiving optical power and the second receiving optical power are approximately consistent. The light splitting ratio and the like do not need to be estimated, whether the relay equipment exists or not can be judged rapidly and accurately, manual investigation is not needed, the labor cost can be reduced, and the detection efficiency is improved.

As shown in fig. 4, fig. 4 is an interaction flow diagram of a third embodiment of a method for detecting a relay device according to an embodiment of the present application. In this embodiment, the first device is an ONU, and the second device is an OLT. In this embodiment, the OLT changes the transmission optical power, and the ONU measures the reception optical power. The main execution body of the embodiment is the OLT. The embodiment comprises the following steps:

s401: the OLT transmits a first message to the ONU based on the first transmitted optical power.

In this embodiment, the first message is used to instruct the ONU to return the first received optical power to the OLT. The ONU measures a first received optical power when receiving the first message, and writes the first received optical power in a first response message in response to the first message. The ONU transmits the first response message to the OLT.

S402: the OLT receives a first response message.

S403: the OLT acquires the first receiving optical power from the first response message.

The OLT analyzes the first response message to obtain the first receiving optical power.

S404: the OLT sends a second message to the ONU.

The OLT adjusts the transmitting optical power to a second transmitting optical power and enables a first difference value between the second transmitting optical power and the first transmitting optical power to be larger than a first threshold value. And after the OLT adjusts the transmitting optical power, the OLT transmits a second message to the ONU based on the second transmitting optical power. And the second message is used for indicating the ONU to return the second receiving optical power to the OLT.

The ONU measures a second received optical power when receiving the second message, and writes the second received optical power in a second response message in response to the second message. The ONU sends the second response message to the OLT.

S405: the OLT receives the second response message.

S406: the OLT acquires the second receiving optical power from the second response message.

And the OLT analyzes the second response message to acquire second receiving optical power.

S407: and the OLT judges whether relay equipment is connected between the OLT and the ONU according to the first receiving optical power and the second receiving optical power.

S203 is referred to according to a specific manner of whether the relay device is connected between the first receiving optical power and the second receiving optical power OLT and the ONU, and therefore, details are not described herein.

In this embodiment, the OLT sends the first message and the second message to the ONU by changing its own sending optical power, and controls the ONU to return the first receiving optical power when receiving the first message and the second receiving optical power when receiving the second message. The OLT determines whether the relay equipment is connected between the OLT and the ONU by judging whether the first receiving optical power and the second receiving optical power are approximately consistent. The light splitting ratio and the like do not need to be estimated, whether the relay equipment exists or not can be judged rapidly and accurately, manual investigation is not needed, the labor cost can be reduced, and the detection efficiency is improved.

In order to ensure the detection accuracy of the relay device, the OLT or the ONU needs to adjust the transmitting optical power many times, and the OLT and the ONU need to interactively obtain multiple sets of the first transmitting optical power, the second transmitting optical power, the first receiving optical power and the second receiving optical power many times to determine whether the relay device is connected between the OLT and the ONU. Increasing the number of interactions between the OLT and the ONU will reduce the detection efficiency. Therefore, in order to improve the detection message for the relay device, the present application also provides a fourth embodiment of the detection method for the relay device. As shown in fig. 5, fig. 5 is an interaction flow diagram of a fourth embodiment of a method for detecting a relay device according to an embodiment of the present application. In the first to third embodiments of the detection method of the relay device, the transmitting optical power is changed on one side of the OLT or the ONU, and the receiving optical power is measured on the opposite side, but in this embodiment, both the OLT and the ONU adjust the transmitting optical power and measure the receiving optical power, so that two sets of transmitting optical power and two sets of receiving optical power can be obtained by two interactions of the OLT and the ONU, and the measurement efficiency can be improved on the premise of improving the accuracy of the scheme. The embodiment comprises the following steps:

s501: the OLT sends a power adjustment message to the ONU.

The power adjustment message is used for controlling the ONU to adjust the transmitted optical power to a third transmitted optical power.

S502: and the ONU adjusts the transmitting optical power into a third transmitting optical power according to the power adjustment message.

S503: the OLT adjusts the transmitting optical power to a first transmitting optical power.

The OLT may first send the power adjustment message to the ONU, and then adjust the sending optical power of the OLT to the first sending optical power. Since the OLT and the ONU need a certain time for adjusting the transmitting optical power, the OLT adjusts the transmitting optical power after informing the ONU to adjust the transmitting optical power, and the OLT and the ONU can almost synchronously adjust the transmitting optical power, so that the time can be saved and the efficiency can be improved.

Of course, the OLT may first adjust the transmitting optical power to the first transmitting optical power and then send the power adjustment message to the ONU, which is not limited in this application.

S504: the OLT sends a first message to the ONU.

Specifically, the OLT transmits a first message to the ONU with a first transmission optical power.

The first message may include two control commands, which may save network resources and improve interaction efficiency. One control instruction in the first message is used for indicating the OMU to return a first response message, wherein the first response message comprises first receiving optical power when the ONU receives the first message; and the other control instruction is used for indicating the ONU to return a third sending optical power when the ONU sends the first response message.

Of course, the two control commands may also be divided into two messages to be sent to the ONU, which is not limited in this application.

S505: the ONU receives the first message and measures the first received optical power.

S506: the ONU responds to the first message and sends a first response message to the OLT.

Specifically, the ONU transmits the first response message to the OLT at the third transmitted optical power. The first response message includes the first received optical power and the third transmitted optical power.

S507: the OLT receives the first response message and measures a third received optical power.

And the third receiving optical power is the receiving optical power when the OLT receives the first response message.

S508: the OLT acquires the first receiving optical power from the first response message.

The OLT analyzes the first response message to obtain a first receiving optical power and a third sending optical power.

S509: the OLT sends a power adjustment message to the ONU.

The power adjustment message is used for controlling the ONU to adjust the transmitting optical power to a fourth transmitting optical power. A fourth difference between the fourth transmitted optical power and the third transmitted optical power is greater than a fourth threshold. Illustratively, the fourth threshold may be 2dBm, 3dBm, 5dBm, 7dBm, or the like. The fourth threshold may be the same as or different from the first threshold, and the application is not limited thereto.

S510: and the ONU adjusts the transmitting optical power into a fourth transmitting optical power according to the power adjustment message.

S511: the OLT adjusts the transmitting optical power to a second transmitting optical power.

The OLT may first send the power adjustment message to the ONU, and then adjust the sending optical power of the OLT to the second sending optical power. Since the OLT and the ONU need a certain time for adjusting the transmitting optical power, the OLT adjusts the transmitting optical power after informing the ONU to adjust the transmitting optical power, and the OLT and the ONU can almost synchronously adjust the transmitting optical power, so that the time can be saved and the efficiency can be improved. Of course, the OLT may first adjust the transmitting optical power to the second transmitting optical power and then send a power adjustment message to the ONU, which is not limited in this application.

Optionally, a first difference between the second transmitted optical power and the first transmitted optical power is the same as a fourth difference between the fourth transmitted optical power and the third transmitted optical power, so as to facilitate a subsequent determination of whether the relay device is present based on the transmitted optical power calculation. The first difference and the fourth difference may also be different, and the application is not limited thereto.

S512: the OLT sends a second message to the ONU.

Specifically, the OLT transmits a second message to the ONU with a second transmission optical power. And the second message is used for instructing the ONU to return the second receiving optical power and the fourth transmitting optical power to the OLT.

S513: the ONU receives the second message and measures a second received optical power.

S514: the ONU sends a second response message to the OLT.

Specifically, the ONU transmits the second response message to the OLT at the fourth transmission optical power. Wherein the second response message includes the second received optical power and the fourth transmitted optical power.

S515: the OLT receives the second response message and measures a fourth received optical power.

And the fourth receiving optical power is the receiving optical power when the OLT receives the second response message.

S516: the OLT acquires the second receiving optical power and the fourth transmitting optical power from the second response message.

The OLT analyzes the first response message to obtain the second receiving optical power and the fourth transmitting optical power.

S517: and the OLT judges whether relay equipment is connected between the OLT and the ONU according to the first receiving optical power, the second receiving optical power, the third receiving optical power and the fourth receiving optical power.

Optionally, in order to ensure the reliability of the received optical power data, the OLT may determine that a first difference is greater than a first threshold according to the first transmitted optical power, the second transmitted optical power, the third transmitted optical power, and the fourth transmitted optical power, and determine whether a relay device is connected between the OLT and the ONU according to the received optical power after the second difference is greater than the first threshold.

The OLT may use the first received optical power and the second received optical power as a set of data, and use the third received optical power and the fourth received optical power as a set of data to respectively determine whether a relay device is connected between the OLT and the ONU. And further judging whether the results of the two groups of data are consistent, and if so, determining the consistent result as a final result. For example, if a result that the relay device is connected between the OLT and the ONU is obtained according to the first received optical power and the second received optical power, and a result that the relay device is connected between the OLT and the ONU is also obtained according to the third received optical power and the fourth received optical power, it can be determined that the relay device is connected between the OLT and the ONU.

Specifically, the second device calculates a second difference between the first received optical power and the second received optical power, and a fifth difference between the third received optical power and the fourth received optical power. And the second equipment respectively compares the second difference value with a second threshold value, the magnitude of a fifth difference value with a fifth threshold value, and the second threshold value and the fifth threshold value are both smaller than the first threshold value. When the second difference is greater than the second threshold and the fifth difference is greater than the fifth threshold, it is indicated that both the two sets of received optical powers change with the adjustment of the transmitted optical power, and it may be determined that the relay device is not connected between the first device and the second device; when the second difference is less than or equal to the second threshold and the fifth difference is less than or equal to the fifth threshold, it is indicated that neither of the two sets of received optical powers changes with the adjustment of the transmitted optical power, and it may be determined that a relay device is connected between the first device and the second device.

Of course, a first average value between the first received optical power and the third received optical power and a second average value between the second received optical power and the fourth received optical power may also be calculated, and whether a relay device is connected between the OLT and the ONU may be determined according to the first average value and the second average value.

The specific manner of determining whether the relay device is connected between the OLT and the ONU is similar to S203, and therefore, the detailed description is omitted here.

In another embodiment, it may be determined whether a relay device is connected between the OLT and the ONU according to the first transmitting optical power, the second transmitting optical power, the third transmitting optical power, the fourth transmitting optical power, the first receiving optical power, the second receiving optical power, the third receiving optical power, and the fourth receiving optical power. Likewise, whether a relay device is connected between the OLT and the ONU can be determined by grouping or averaging data. The specific calculation method is similar to S203, and therefore, the detailed description thereof is omitted.

In this embodiment, the OLT changes its own transmitting optical power, and also controls the ONU to change the transmitting optical power, and the OLT and the ONU both measure the receiving optical power, so that two sets of transmitting optical powers and two sets of receiving optical powers can be obtained after two times of interaction between the OLT and the ONU, and the measurement efficiency can be improved on the premise of improving the accuracy of the scheme.

In some other embodiments, the OLT may not perform S501 and/or S503, and the ONU does not perform S502. That is, in the process of the first interaction between the OLT and the ONU (i.e. obtaining the message traffic between the first received optical power OLT and the ONU), the OLT and/or the ONU do not adjust the transmitted optical power, and only sends the message with the currently set transmitted optical power of the OLT and/or the ONU, so that the time for adjusting the transmitted optical power can be reduced, and the detection efficiency can be improved.

As shown in fig. 6, fig. 6 is a schematic structural diagram of an embodiment of an optical line terminal according to the embodiment of the present application. The optical line terminal 600 in this embodiment includes an acquisition module 601 and a determination module 602. The obtaining module 601 is configured to obtain a first receiving optical power when the first device receives the first message, and obtain a second receiving optical power when the first device receives the second message. The first message is sent by the second device to the first device based on the first sending optical power, the second message is sent by the second device to the first device based on the second sending optical power, and a first difference value between the first sending optical power and the second sending optical power is larger than a first threshold value. The determining module 602 is configured to determine whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power.

In some embodiments, the determining module 602 is specifically configured to calculate a second difference between the first received optical power and the second received optical power; when the second difference is larger than a second threshold value, determining that the relay equipment is not connected between the first equipment and the second equipment, wherein the second threshold value is smaller than the first threshold value; and when the second difference is smaller than or equal to a second threshold value, determining that the relay equipment is connected between the first equipment and the second equipment.

In some embodiments, the determining module 602 is specifically configured to obtain a first difference value; calculating a second difference between the first received optical power and the second received optical power; when a third difference between the first difference and the second difference is smaller than a third threshold, determining that the relay equipment is not connected between the first equipment and the second equipment, wherein the third threshold is smaller than the first threshold; and when the third difference is larger than or equal to the third threshold, determining that the relay equipment is connected between the first equipment and the second equipment.

In some embodiments, the first device is an optical line terminal and the second device is an optical network unit. The optical line terminal 600 further comprises a sending module 603. The sending module 603 is configured to send a power adjustment message to the second device, and send a third message to the second device. The power adjustment message is used for instructing the second device to adjust the transmitting optical power to the first transmitting optical power, and the third message is used for instructing the second device to transmit the first message to the first device.

In some embodiments, the sending module 603 is further configured to send a power adjustment message to the second device, and send a third message to the second device. The power adjustment message is used for instructing the second device to adjust the first sending optical power to the second sending optical power, and the third message is used for instructing the second device to send a second message to the first device.

In other embodiments, the first device is an optical network unit and the second device is an optical line terminal. The optical line terminal 600 further comprises a sending module 603 and a receiving module 604. The sending module 603 is configured to send, by the first device, a first message, where the first message is used to instruct the first device to return the first received optical power to the second device. The receiving module 604 is configured to receive a first response message of the first message, where the first response message includes a first received optical power when the first device receives the first message.

The obtaining module 601 is specifically configured to obtain the first received optical power from the first response message. The sending module 603 is further configured to send a second message to the first device, where the second message is used to instruct the first device to return the second received optical power to the second device. The receiving module 604 is further configured to receive a second response message of the second message, where the second response message includes a second received optical power when the first device receives the first message. The obtaining module 601 is specifically configured to obtain the second received optical power from the second response message.

In other embodiments, the obtaining module 601 is further configured to obtain a third received optical power when the first response message is received, and obtain a fourth received optical power when the second response message is received. The determining module 602 is specifically configured to determine whether a relay device is connected between the first device and the second device according to the first received optical power, the second received optical power, the third received optical power, and the fourth received optical power.

As shown in fig. 7, fig. 7 is a schematic structural diagram of another embodiment of an optical line terminal according to the embodiment of the present application. In this embodiment, the olt 700 may include one or more processors 701 and an optical transceiver 702. The processor 701 and the optical transceiver 702 are connected by wires. The processor 701 is configured to execute instructions, and the optical transceiver 703 is configured to transmit and receive optical signals to and from an optical transceiver of an ONU.

The processor 701 may be one or more chips or one or more integrated circuits. For example, the processor 701 may be one or more field-programmable gate arrays (FPGAs), application-specific integrated chips (ASICs), system on chips (socs), central Processing Units (CPUs), network Processors (NPs), digital signal processing circuits (DSPs), micro Controller Units (MCUs), programmable Logic Devices (PLDs), or other integrated chips, or any combination of the above chips or processors, etc.

The processor 701 may perform the operations performed by the OLT in the embodiments shown in fig. 2 to 5, which are not described herein again.

Optionally, the optical line terminal 700 further includes a memory 703. The memory 703 stores one or more applications or data. The memory 703 may be volatile storage or persistent storage. The program stored in memory 703 may include one or more modules, each of which may include a sequence of instructions that operate on the optical line terminal 700. Further, the processor 701 may be arranged to communicate with the memory 703 to execute a series of instruction operations in the memory 703 on the olt 700.

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

The terms "first," "second," "third," "fourth," and the like in the description and claims of this application and in the foregoing drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a read-only memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

Claims (13)

1. A method for detecting a relay device, the method comprising:

acquiring a first receiving optical power when first equipment receives a first message, wherein the first message is sent to the first equipment by second equipment based on a first sending optical power;

acquiring a second receiving optical power when the first device receives a second message, wherein the second message is sent to the first device by the second device based on a second sending optical power, and a first difference between the first sending optical power and the second sending optical power is larger than a first threshold;

and judging whether a relay device is connected between the first device and the second device or not according to the first receiving optical power and the second receiving optical power.

2. The method of claim 1, wherein the determining whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power comprises:

calculating a second difference between the first received optical power and the second received optical power;

when the second difference is greater than a second threshold, determining that the relay device is not connected between the first device and the second device, wherein the second threshold is smaller than the first threshold;

when the second difference is smaller than or equal to the second threshold, it is determined that the relay device is connected between the first device and the second device.

3. The method of claim 1, wherein the determining whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power comprises:

acquiring the first difference value;

calculating a second difference between the first received optical power and the second received optical power;

determining that the relay device is not connected between the first device and the second device when a third difference between the first difference and the second difference is less than a third threshold, the third threshold being less than the first threshold;

when the third difference is greater than or equal to the third threshold, it is determined that the relay device is connected between the first device and the second device.

4. The method according to any of claims 1 to 3, wherein the first device is an optical line terminal and the second device is an optical network unit.

5. The method of claim 4, wherein obtaining the first received optical power when the first device receives the first message comprises:

and the first equipment sends a third message to the second equipment, wherein the third message is used for indicating the second equipment to send the first message to the first equipment.

6. The method of claim 5, wherein before the first device sends the third message to the second device, comprising:

the first device sends a power adjustment message to the second device, where the power adjustment message is used to instruct the second device to adjust the sending optical power to the first sending optical power.

7. The method of claim 5 or 6, wherein before obtaining the second received optical power when the first device receives the second message, the method comprises:

the first device sends the power adjustment message to the second device, where the power adjustment message is used to instruct the second device to adjust the first sending optical power to the second sending optical power;

and the first equipment sends the third message to the second equipment, wherein the third message is used for indicating the second equipment to send the second message to the first equipment.

8. The method according to any of claims 1 to 3, wherein the first device is an optical network unit and the second device is an optical line terminal.

9. The method of claim 8, wherein obtaining the first received optical power when the first device receives the first message comprises:

the second device sends the first message to the first device, wherein the first message is used for instructing the first device to return the first received optical power to the second device;

the second device receiving a first response message of the first message, the first response message including the first received optical power at the time the first device receives the first message;

the second equipment acquires the first receiving optical power from the first response message;

the obtaining of the second receiving optical power when the first device receives the second message includes:

the second device sends the second message to the first device, wherein the second message is used for instructing the first device to return the second received optical power to the second device;

the second device receives a second response message of the second message, wherein the second response message comprises second received optical power when the first device receives the first message;

the second device obtains the second received optical power from the second response message.

10. The method of claim 9, wherein the first response message is sent by the first device based on a third transmit power, wherein the second response message is sent by the first device based on a fourth transmit power, wherein a fourth difference between the fourth transmit optical power and the third transmit optical power is greater than a fourth threshold, and wherein the method further comprises:

the second equipment acquires third receiving optical power when receiving the first response message;

the second equipment acquires fourth receiving optical power when receiving the second response message;

the determining whether a relay device is connected between the first device and the second device according to the first received optical power and the second received optical power includes:

and the second equipment judges whether relay equipment is connected between the first equipment and the second equipment according to the first receiving optical power, the second receiving optical power, the third receiving optical power and the fourth receiving optical power.

11. The method of claim 10, wherein the determining whether a relay device is connected between the first device and the second device according to the first received optical power, the second received optical power, the third received optical power, and the fourth received optical power comprises:

the second device calculating a second difference between the first received optical power and the second received optical power, a fifth difference between the third received optical power and the fourth received optical power;

when the second difference is greater than a second threshold and the fifth difference is greater than a fifth threshold, the second device determines that the relay device is not connected between the first device and the second device, and the second threshold and the fifth threshold are both smaller than the first threshold;

when the second difference is less than or equal to the second threshold and the fifth difference is less than or equal to the fifth threshold, the second device determines that the relay device is connected between the first device and the second device.

12. An olt comprising a processor and an optical transceiver, the processor coupled to the optical transceiver, the processor configured to execute instructions that, when executed, cause the olt to perform the method of any of claims 1-11.

13. A passive optical network system comprising an optical line terminal, an optical distribution network and a plurality of optical network units, the optical line terminal being connected to the plurality of optical network units via the optical distribution network, the optical line terminal being as claimed in claim 12.

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