TIME SYNCHRONIZATION METHOD FOR PASSIVE OPTICAL NETWORK AND ELECTRONIC DEVICE AND STORAGE MEDIUM.

Abstract

A time synchronization method for a passive optical network and an electronic device and storage medium. The method applied to an OLT comprises: acquiring a first response time from a first ONU (S1100); performing a distance measurement calculation on the first ONU to obtain a first equalization delay (S1200); generating an equalization delay configuration message according to the first response time and the first equalization delay (S1300); and sending the equalization delay configuration message to a second ONU to configure a second equalization delay of the second ONU (S1400), wherein the first and second ONUs are ONUs connected to the same optical fiber branch.

Description

TIME SYNCHRONIZATION METHOD FOR PASSIVE OPTICAL NETWORK AND ELECTRONIC DEVICE AND STORAGE MEDIUM CROSS REFERENCE TO RELATED APPLICATION This application is based on Chinese patent application no. 202110284376.X filed on March 17, 2021, and claims priority from the Chinese patent application, the full content of which is incorporated herein by reference. TECHNICAL FIELD This disclosure relates to the technical field of communication, in particular to a method for time synchronization in a passive optical network, an electronic device, and a storage medium. BACKGROUND During the deployment of passive optical networks (PONs), different optical network units (ONUs) must be compatible so that uplink data from each ONU does not collide. For example, in a low-delay PON system, only low-delay-based reach is supported. Non-low-delay ONUs may not perform reach using the traditional reach method, nor do they support low-delay-based reach. Reaching of the non-low-delay ONU is performed with the help of a low-delay ONU or a low-delay reacher. Specifically, after the low-delay ONU or the low-delay reacher completes reach on a fiber branch and obtains the reach result, the non-low-delay ONU reuses the reach result and accesses the fiber branch. During time synchronization in related schemes, the OLT does not consider the local time variation parameters (such as response time) of the ONUs when calculating the equalization delay (EqD). Since the local time variation parameters of different ONUs are generally different, the reach result for a given ONU is usually specific to that ONU. Another ONU accessing the same fiber optic branch may not use the existing reach result from that ONU, leading to a time synchronization failure. SUMMARY zeon Ln / pznz / Β / γΐΛΐ The following is a summary of the subject matter described herein. This summary is not intended to limit the scope of protection of the claims. A method for time synchronization in passive optical networks, an electronic apparatus, and a storage medium are provided in some embodiments of this disclosure. According to one aspect of this disclosure, one embodiment provides a method for time synchronization in a PON, which is applied to an OLT, the method includes acquiring a first response time from a first ONU; performing a reach calculation on the first ONU to acquire a first equalization time delay; generating an equalization delay configuration message according to the first response time and the first equalization delay; sending the equalization delay configuration message to a second ONU to configure a second equalization delay of the second ONU; wherein the first ONU and the second ONU access the same optical fiber branch. According to another aspect of this disclosure, one embodiment provides a method for time synchronization in a PON, which is applied to a first ONU, and the method includes sending a first response time to an OLT, to instruct the OLT to carry out the method applied to the OLT as described above. According to another aspect of the present disclosure, one embodiment provides a method for time synchronization in a PON, which is applied to a second ONU. The method includes receiving an equalization delay configuration message from an OLT; configuring a second equalization delay of the second ONU according to the equalization delay configuration message; and the second equalization delay is acquired by the OLT through the method applied to the OLT as described above. According to another embodiment of the present disclosure, one embodiment provides a method for time synchronization in a PON, which includes sending a response time configuration instruction to a second ONU to configure the response time of the second ONU so that the response time of the second ONU matches the response time of the first ONU; and wherein the first ONU and the second ONU access the same fiber optic branch. zeon ιη / ρζηζ / Β / γίΛΐ According to another aspect of the present disclosure, one embodiment provides a method for time synchronization in a PON, which is applied to a second ONU, the method includes receiving a response time configuration instruction; configuring a response time of the second ONU according to the response time configuration instruction so that the response time of the second ONU matches the response time of the first ONU; wherein, the first ONU and the second ONU access the same fiber optic branch. According to another aspect of the present disclosure, one embodiment provides a time synchronization device in passive optical networks, the device includes an acquisition module, which is configured to acquire a first response time from a first ONU; a calculation module, which is configured to perform range calculations on the first ONU to obtain a first equalization delay; a generation module, which is configured to generate an equalization delay configuration message according to the first response time and the first equalization delay; and a sending module, which is configured to send an equalization delay configuration message to a second ONU to configure a second equalization delay for the second ONU; wherein the first ONU and the second ONU access the same optical fiber branch. According to another aspect of the present disclosure, an embodiment provides an electronic apparatus, including a memory, a processor, and a computer program stored in memory and executable on the processor, which, when executed by the processor, causes the processor to perform any one of the methods as described above. According to another aspect of this disclosure, an embodiment provides a computer-readable storage medium that stores a computer-executable instruction that, when executed by a processor, causes the processor to perform any of the methods as described above. BRIEF DESCRIPTION OF THE DRAWINGS To illustrate the technical scheme in the embodiments of this disclosure, the drawings related to the description of the embodiments or related technologies are briefly presented below. It is evident that the drawings described below are only some embodiments of this disclosure. Skilled workers can derive other drawings based on these drawings without expending creative effort. Figure 1 represents a schematic diagram showing the principle of range in a passive optical grating; Figure 2 represents a schematic diagram showing the operational sequence in a passive optical network; Figure 3 represents a schematic diagram showing a system architecture in which a time synchronization method is implemented in a passive optical network; Figure 4 represents a flowchart showing a method for time synchronization in a passive optical network according to an embodiment of the present disclosure; Figure 5 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 6 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 7 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 8 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 9 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 10 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 11 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; zeon Ln / pznz / B / γΐΛΐ Figure 12 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 13 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; Figure 14 represents a flowchart showing a method for time synchronization in a passive optical network according to another embodiment of the present disclosure; and Figure 15 represents a schematic diagram showing a device for time synchronization in a passive optical network according to an embodiment of the present disclosure. DETAILED DESCRIPTION The following description sets out specific details, such as the system's specific structure and technology, for illustrative purposes rather than as a limitation, to aid in understanding the embodiments of this disclosure. However, it should be clear to those skilled in the art that the embodiments of this disclosure can be implemented in other embodiments that do not have these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the embodiments in this disclosure with unnecessary detail. It should be noted that, in some cases, the steps shown or described may be performed in a different order than the logical order shown in the flowcharts. It should also be noted that the terms "first" and "second," if used in the description and drawings, are intended to distinguish similar objects and do not necessarily imply any specific order or sequence. It should also be understood that references to an embodiment or some embodiments, etc., described in the description of some embodiments in this disclosure mean that specific features, structures, or characteristics described in conjunction with this embodiment are included in one or more embodiments of this disclosure. Therefore, the expressions "in one embodiment," "in some embodiments," "in other embodiments," and "in additional embodiments" that appear in various places in this description do not necessarily all refer to the same embodiment, but rather mean one or more, but not all, embodiments unless emphasized otherwise. The terms "includes," "contains," "has," and their variations all mean "includes," but without limitation, unless specifically emphasized otherwise. Passive optical networks (PONs) typically adopt a point-to-multipoint network structure, with downlink data being broadcast. Through the optical distribution network (ODN), data can reach the optical network unit (ONU), and the ONU identifies the distributed data to itself according to its ONUID. In the uplink direction, since an optical fiber is shared, the ONU's uplink data is transmitted using TDMA mode, and only one ONU can send data to an optical line terminal (OLT) at a time; otherwise, it would lead to an uplink data collision. To avoid uplink data collisions, the PON protocol stipulates that the logical distance of all ONUs must be compensated at the same level through time-delay compensation. Because the distance from each ONU to the OLT is different, the signal transmission time on the optical fiber also varies.Therefore, it is necessary to measure the logical distance between each ONU and the OLT to calculate the equalization delay (EqD) of each ONU and send the corresponding delay to the ONU during the registration stage. The ONU delays the uplink data based on the downlink data and according to the assigned EqD to avoid collisions between the uplink data of each ONU. During PON deployment, different ONUs will be supported to prevent uplink data collisions between each ONU. For example, in a low-latency PON system, only low-latency reach is supported. Non-low-latency ONUs may not perform reach using the traditional reach method, nor do they support low-latency reach. Reaching of the non-low-latency ONU is performed with the help of a low-latency ONU or a low-latency reacher. Specifically, after the low-latency ONU or the low-latency reacher completes reach on a fiber optic branch and obtains the reach result, the non-low-latency ONU reuses the reach result and accesses the fiber optic branch. During time synchronization in related schemes, the OLT does not consider the local time variation parameters (such as response time) of the ONUs when calculating the EqD. Since the local time variation parameters of different ONUs are generally different, the reach result for a ONU is usually specific to that ONU. Another ONU accessing the same fiber optic branch may not use the existing reach result of the ONU, leading to a time synchronization failure. That is, although response time is normally included in the EqD calculation by the OLT (response time is typically taken as transmission delay during the calculation), in practical use the EqD does not include response time. Due to the differences in response time of each ONU, which is typically 35±1 ps, the EqD between ONUs cannot be reused. For example, as shown in Figures 1 and 2, where Figure 1 represents a schematic diagram showing the reach principle in a passive optical network; and Figure 2 represents a schematic diagram showing the operational sequence in a passive optical network. In the figures, PSBu indicates an uplink physical synchronization block; PSBd indicates a downlink physical synchronization block; PHY frame content indicates the physical frame content; and PLOAM indicates the Physical Layer Operations, Management, and Maintenance (PLOAM) channel. In the reach schemes, a reach request sent by an OLT reaches an ONU after a transmission delay time elapses. RspTime (response time) is the ONU's response time. StartTime specifies the time for the OLT to begin loading the response, which is typically set to 0 in PON reach.After processing the message, the ONU waits until a StartTime period elapses, then sends a response frame that experiences an uplink transmission delay and reaches the OLT. The OLT then calculates the ONU's Rtd (round-trip delay). Assuming the uplink and downlink transmission delays of the data are TPd_u and TPd_d respectively, then Rtd = TPd_d + RspTime + StartTime + TPd_u. Since the distance between each ONU and the OLT is different, the Rtd of each ONU is different. To ensure the same uplink data phase, the OLT calculates an EqD for each ONU, so that the sum of each ONU's Rtd and EqD is a fixed value. This value is also called equalized round-trip delay (Teqd).Teqd is a value set by the OLT based on the longest optical fiber length, which is greater than or equal to the ONU with the farthest logical distance. It represents the round-trip delay for each ONU on the same PON port after delay compensation. The Teqd of an ONU on the same PON port satisfies: Teqd = Rtd(n) + EqD(n), meaning EqD(n) = Teqd - Rtd(n). EqD can be obtained for the nth ONU, where n = 1, 2, 3... The ONU must wait until the EqD period has elapsed before processing the OLT request, thus ensuring time synchronization for all ONUs on the same PON port. During time synchronization in related schemes, the ONU does not report local time variation parameters (such as the response time, which is 35 ± 1 ps as specified in the standard) to the OLT.These parameters are invisible to the OLT, and the ONU response time parameters are not considered during the OLT's equalization delay calculation. Therefore, the reach result for an ONU is generally specific to that ONU. When another ONU accesses the same fiber optic branch again, the previous reach result of an existing ONU cannot be reused. In light of this, some embodiments of this disclosure provide a method for time synchronization in PONs, an electronic device, and a storage medium. By configuring the equalization delay or response time for the second ONU through the OLT, the equalization delay or response time of the second ONU matches that of the first ONU. As such, time synchronization can be achieved when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. In some implementations, the ONU can report its own reach-related response time to the OLT during ONU activation. Alternatively, the OLT can obtain the ONU's response time during normal ONU operation, such as the ONU's local response time. The OLT can record this information and calculate the ONU's reach result, and calculate the reach result of another ONU using this information across different ONUs, so that different ONUs can flexibly access the same branch. In other implementations, the response time of each ONU can be configured to be the same, so that different ONUs can reuse the same branch. EqD of other UNs. Some of the findings in this disclosure will be illustrated in more detail with reference to the drawings. Figure 3 represents a schematic diagram showing a system architecture in which a time synchronization method in passive optical networks is demonstrated according to one embodiment of this disclosure. As shown in Figure 3, the system architecture includes an optical line terminal (OLT) 100, a first optical network unit (ONU) 210 / a second ONU 220, and another ONU 230. In some embodiments, the second ONU 220 is an ONU that accesses a passive optical network to take the place of the first ONU 210. That is, the second ONU 220 uses the same optical fiber branch as the first ONU 210. In some embodiments, one or both of the first ONU 210 and the second ONU 220 may be a low-delay ONU or a non-low-delay ONU. The OLT 100 is communicatively connected to each ONU via optical fibers. For example, the OLT 100 is communicatively connected to the first and second ONUs via the first optical fiber branch L1. The OLT 100 is communicatively connected to the other ONUs 230 via the second optical fiber branch L2 and the third optical fiber branch L3, respectively. The first ONU 210 / second ONU 220 is connected to a return device 300 and a diagnostic and analysis system 100 via optical fibers. For example, the OLT 100 is communicatively connected to the first ONU / second ONU via the first L1 optical fiber branch. In some embodiments, the second ONU 220 is an ONU that accesses a passive optical network to take the place of the first ONU 210. That is, the second ONU 220 uses the same optical fiber branch as the first ONU 210. It should be noted that replacing the first ONU 210 optical network unit with the second ONU 220 optical network unit can be a direct replacement or a replacement of the ONU's MAC chip. The system architecture and application scenarios described in one embodiment of this application are intended for ease of understanding rather than as limitations of the technical scheme of various embodiments of this disclosure. It is known to those skilled in the art that, with the evolution of system architecture and the emergence of new application scenarios, the technical scheme provided by the embodiment of this disclosure is also applicable to similar technical problems. It may be understood by those skilled in the art that the system architecture shown in Figure 3 does not constitute a limitation to the making of this disclosure, and may include more or fewer components than those shown, or some components may be combined or have different component arrangements. In the system architecture shown in Figure 3, each device can request its stored programs for passive optical network time synchronization to perform the passive optical network time synchronization method. Based on the above system architecture, several realizations of the time synchronization method in passive optical networks are proposed in this disclosure. Figure 4 represents a method for time synchronization in passive optical networks, which is applied to an OLT; the method includes the following operations. In S1100, a first response time of a first ONU is acquired. In S1200, a range calculation is performed to the first ONU to obtain a first equalization delay (EqD). In S1300, an equalization delay configuration message is generated according to the first response time and the first EqD. In S1400, the equalization delay configuration message is sent to the second ONU to configure the second Eqd for the second ONU. The first ONU and the second ONU access the same branch of fiber optic cable. In some implementations, S1100 can be performed in multiple communication processes between the OLT and the ONUs. For example, during the discovery process at ONU activation, S1100 is performed to obtain the first response time of the first ONU. S1100 can also be performed during the reach process at ONU activation to obtain the first response time of the first ONU. And S1100 can also be performed during normal ONU operation to read the first response time of the first ONU. The implementations described herein are not limited to these. In some implementations, the first equalization delay obtained in S1200 can be used to configure the first ONU. That is, the first equalization delay is sent to the first ONU, thus configuring its first equalization delay. For example, the OLT can configure the first equalization delay of the first ONU via the equalization delay configuration message. The equalization delay configuration message can be a Ranging Time result message, and its contents are shown in Table 2 below. When it is necessary to replace the first ONU, S1300 and S1400 are executed to configure the second equalization delay for the second ONU. It should be noted that the calculation of the second equalization delay can be performed on the OLT or the ONU (such as the second ONU). The realizations in this disclosure are not limited to this. According to various embodiments of this disclosure, the equalization delay of the second ONU is configured through the OLT, so that the equalization delay of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. In some implementations, the equalization delay configuration message includes a first response time and a first equalization delay. Accordingly, S1400, in which the equalization delay configuration message is sent to the second ONU to configure the second Eqd for the second ONU, includes the following operations. In S1410, the equalization delay configuration message is sent to the second ONU, instructing the second ONU to calculate the second equalization delay according to the first response time, the first equalization delay, and the second response time of the second ONU. In some implementations, the calculation of the second EqD can be performed on the second ONU. The OLT sends the first response time and the first equalization delay to the second ONU during the generation of the zeon Ln / pznz / B / γALA equalization delay configuration message. After receiving the equalization delay configuration message with the first response time and the first equalization delay, the second ONU calculates the second equalization delay along with the local response time, i.e., the second response time. For example, the second equalization delay EqD2 can be calculated using the following equation: EqD2 = RspTimen - EqDi - RspTime2, where RspTimen is the first response time, EqDi is the first equalization delay, and RspTime2 is the second response time. In some implementations, the first response time and the first equalization delay can be combined into a single equalization delay setting value, and a bitmask is set to indicate whether the equalization delay setting message contains the response time, so that it is compatible with the protocol of the equalization delay setting message sent by the OLT in related schemes, as detailed below. In some implementations, the equalization delay configuration message also includes a bitmask. The bitmask set in the first state indicates that the equalization delay configuration message contains the first response time and the first equalization delay. In some implementations, a bitmask can be set on the equalization delay configuration message. The bitmask's state indicates whether the equalization delay configuration message contains a response time. The first response time and the first equalization delay can be combined into a single equalization delay configuration value. For example, a bitmask set to the first state indicates that the equalization delay configuration value includes both the first response time and the first equalization delay. Alternatively, a bitmask set to the second state indicates that the equalization delay configuration value includes the equalization delay (either the first or second equalization delay, but not the response time). In some implementations, the equalization delay configuration message contains a second equalization delay. Consequently, as shown in Figure 5, S1300, in which the equalization delay configuration message is generated according to the first response time and the first EqD, includes the following operations. In S1310, a second response time is acquired from a second ONU. In S1320, the second equalization delay of the second ONU is calculated according to the first response time, the first equalization delay, and the second response time. In S1330, an equalization delay configuration message is generated according to the second equalization delay. In some implementations, the calculation of the second EqD can be performed on the OLT. The OLT can obtain the second response time via S1310. For example, the OLT can obtain the response time of the second ONU using the response information message, Serial_Number_ONU (ONU serial number report message, as shown in Table 1 below), in the related schematics. Alternatively, the OLT can also obtain the second response time of the second ONU using the response time feedback message (response time message), as shown in Table 4 below. In some implementations, the equalization delay configuration message also includes a bitmask. The bitmask set in the second state indicates that the equalization delay configuration message contains the second equalization delay. In some implementations, a bitmask can be set on the equalization delay configuration message. The bitmask's state indicates whether the equalization delay configuration message contains a response time. The first response time and the first equalization delay can be combined into a single equalization delay configuration value. For example, a bitmask set to the first state indicates that the equalization delay configuration value includes both the first response time and the first equalization delay. Alternatively, a bitmask set to the second state indicates that the equalization delay configuration value includes the equalization delay (either the first or second equalization delay, but not the response time). In some implementations, the OLT can calculate the second equalization delay EqD2 using the following equation: EqD2=RspTime1+EqD1 RspTime2, where RspTime1 is the first response time, EqD1 is the first equalization delay, and RspTime2 is the second response time. In some embodiments, as shown in Figure 6, S1100, in which the first response time of the first ONU is acquired and stored, includes the following operations. In S1110, the first ONU is sent one of, an SN request, a scope request, or a response time acquisition request. In S1120, the response information is received, which carries the first response time from the first ONU. In some implementations, the SN request or scope request may be an SN request or scope request during ONU activation in the related scheme. The response time acquisition request may be a defined response time acquisition request, as shown in Table 3 below. The response information from the first ONU may be the Serial_Number_ONU message (ONU serial number report message) in the related scheme, as shown in Table 1 below. Alternatively, the response information from the first ONU may be a response time feedback message (response time message), as shown in Table 4 below. In some implementations, the first ONU is a low-delay ONU, and the second ONU is a non-low-delay ONU. Alternatively, the first ONU is a non-low-delay ONU, and the second ONU is a low-delay ONU. For example, in a low-delay PON network, the first ONU is a low-delay ONU. If it is necessary to replace the first ONU with a second non-low-delay ONU, the method described above can be used to configure the equalization delay of the second ONU for compatibility. Conversely, in a non-low-delay PON network, the first ONU is a non-low-delay ONU. If it is necessary to replace the first ONU with a second low-delay ONU, the method described above can be used to configure the equalization delay of the second ONU for compatibility.It is evident that both the first UN and the second UN can also be a low-delay UN or a non-low-delay UN, and this disclosure is not limited to them. zeon ιη / ρζηζ / Β / γίΛΐ According to various embodiments of this disclosure, the equalization delay of the second ONU is configured through the OLT, so that the equalization delay of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. An embodiment of the present disclosure provides a method for time synchronization in passive optical networks, applicable to a first ONU; the method includes the following operations. In S2100, an initial response time is sent to an OLT, instructing the OLT to perform the time synchronization method in passive optical networks as described above. For example, steps S1100 to S1400, described in conjunction with Figure 4, S2311 to S2313, described in conjunction with Figure 5, or S2321 to S2324, described in conjunction with Figure 6, are carried out. In some embodiments, the method for time synchronization in passive optical networks also includes the following operations. An equalization delay configuration message is received from the OLT to configure the first ONU. That is, the first equalization delay of the first ONU is configured by the first equalization delay sent to the first ONU. The equalization delay configuration message can be a Ranging_Time message, and the content of the Ranging_Time message is shown in Table 2 below. According to various embodiments of this disclosure, the equalization delay of the second ONU is configured through the OLT, so that the equalization delay of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. In some implementations, as shown in Figure 7, before S2100 in which the first response time is sent to the OLT, the method also includes the following operations. In S2200, an SN request, a scope request, or a response time acquisition request is acquired from an OLT. zeon ιη / ρζηζ / Β / γίΛΐ In S2300, a local response time is acquired as a first response time according to one of the following: the SN request, the scope request, or the OLT response time acquisition request. In some implementations, the OLT sends a signal request, range request, or response time acquisition request to the first ONU by executing the S1110 above. The first ONU receives the signal request, range request, or response time acquisition request from the OLT by executing S2200. The SN request or scope request can be an SN request or scope request during ONU activation in the related scheme. The response time acquisition request can be a defined response time acquisition request, as shown in Table 3 below. The response information from the first ONU can be the Serial_Number_ONU message (ONU serial number report message) in the related scheme, as shown in Table 1 below. Alternatively, the response information from the first ONU can be a response time feedback message (response time message), as shown in Table 4 below. According to various embodiments of this disclosure, the equalization delay of the second ONU is configured through the OLT, so that the equalization delay of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. One embodiment of this disclosure provides a method for time synchronization in passive optical networks, applicable to a second ONU. As shown in Figure 8, the method includes the following operations. In S3100, an equalization delay configuration message is received from an OLT. In S3200, a second equalization delay is configured for the second ONU according to the equalization delay configuration message; the second equalization delay is obtained by the OLT performing the time synchronization method in passive optical networks as described above. For example, the second equalization delay is generated by the OLT performing steps S1100 to S1400 described above in conjunction with Figure 4, S2311 to S2313 described in conjunction with Figure 5, or S2321 to S2324 described in conjunction with Figure 6. According to various embodiments of this disclosure, the equalization delay of the second ONU is configured through the OLT, so that the equalization delay of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. In some implementations, the equalization delay configuration message includes a first response time and a first equalization delay. Consequently, as shown in Figure 9, S3200, in which the second equalization delay is configured for the second ONU according to the equalization delay configuration message, includes the following operations. In S3210, a second response time is acquired from a second ONU. In S3220, the second equalization delay is calculated according to the first response time, the first equalization delay, and the second response time. In some implementations, the OLT performs the S1410 command described above, in which an equalization delay configuration message is sent to the second ONU. Consequently, the second ONU executes S3210 and S3220 to calculate the second equalization delay. The calculation of the second EqD can be performed on the second ONU. The second ONU can obtain the local response time, i.e., the second response time, via S3210. After receiving the equalization delay configuration message with the first response time and the first equalization delay, the second ONU calculates the second equalization delay along with the local response time, i.e., the second response time.For example, the second equalization delay EqD2 can be calculated using the following equation: EqD2=RspTime1 +EqD1 -RspTime2, where RspTimel is the first response time, EqD1 is the first equalization delay and RspTime2 is the second response time. In some implementations, the equalization delay configuration message also includes a bitmask. Consequently, as shown in Figure 10, S3200, in which the second equalization delay is configured for the second ONU according to the equalization delay configuration message, also includes the following operations. The bitmask state is determined in S3230. In S3240, it is determined that the equalization delay configuration message contains the first response time and the first equalization delay, in response to the bitmask being in the first state. In some implementations, the second ONU can identify whether the equalization delay configuration message contains the response time by examining the bitmask state. For example, a bitmask set to the first state indicates that the equalization delay configuration value includes the first response time and the first equalization delay. Alternatively, a bitmask set to the second state indicates that the equalization delay configuration value includes the equalization delay (either the first or second equalization delay, but not the response time). In some implementations, S3230 and S3240 precede S3210 and S3220.That is, when the bitmask is in the first state, it is determined that the equalization delay configuration message contains the first response time and the first equalization delay, and then the above S3210 and S3220 are performed to calculate the second equalization delay. In some implementations, the equalization delay configuration message contains a second equalization delay. In some embodiments, as shown in Figure 11, the method for time synchronization in passive optical networks also includes the following operations. In S3300, a second response time is acquired from a second ONU. In S3400, the second response time is sent to the OLT, to give instruction to calculate the second equalization delay according to the first response time, the first equalization delay and the second response time.In some implementations, S3300 and S3400 correspond to S1310 through S1330 described above. For example, the ONU can send the second response time to the OLT by executing S3300 and S3400. Consequently, the OLT can calculate the second equalization delay and generate an equalization delay configuration message by executing S1310 through S1330. The calculation of the second EqD can be performed on the OLT. S3300 and S3400 precede S3100 and S3200. The second ONU can send a second response time to the OLT via S3300. For example, the second ONU can send the second response time to the OLT using the response information message Serial_Number_ONU (ONU serial number report message, as shown in Table 1 below) in the related schemes.Alternatively, the second ONU can also send the second response time to the OLT by means of the response time feedback message (Response Time Message) as shown in Table 4 below. In some implementations, the equalization delay configuration message also includes a bitmask. Consequently, as shown in Figure 12, S3200, in which the second equalization delay is configured for the second ONU according to the equalization delay configuration message, includes the following operations. In S3250 the state of the bit mask is determined. In S3260, it is determined that the equalization delay configuration message contains the second equalization delay, in response to the bitmask being in the second state. In S3270, the second equalization delay is configured for the second ONU according to the equalization delay configuration message. In some implementations, after receiving the equalization delay configuration message from the OLT in the S3100, the second ONU can identify whether the equalization delay configuration message contains the response time by using a bitmask state. For example, a bitmask set to the first state indicates that the equalization delay configuration value includes the first response time and the first equalization delay. Alternatively, a bitmask set to the second state indicates that the equalization delay configuration value includes the equalization delay (either the first or second equalization delay, but not the response time).It is determined that the equalization delay configuration message contains the second equalization delay, in response to the bitmask being in the second state; in that case, the second equalization delay can be used directly. In some embodiments, as shown in Figure 13, prior to S3300 in which the second response time of a second ONU is acquired, the method includes the following operations. In S3310, an SN request, a scope request, or a response time acquisition request is acquired from an OLT. In S3320, a local response time is acquired as a second response time according to the SN request, scope request, or OLT response time acquisition request. In some implementations, the SN request or scope request may be an SN request or scope request during ONU activation in the related scheme. The response time acquisition request may be a defined response time acquisition request, as shown in Table 3 below. The response information from the second ONU may be the Serial_Number_ONU message (ONU serial number report message) in the related scheme, as shown in Table 1 below. Alternatively, the response information from the second ONU may also be a response time feedback message (response time message), as shown in Table 4 below. According to various embodiments of this disclosure, the equalization delay of the second ONU is configured through the OLT, so that the equalization delay of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. The following illustration is provided by means of three example situations, namely, ONU activation process, normal operation process, and restart process. zeon ιη / ρζηζ / Β / γίΛΐ Situation 1: Acquisition of UN response time during activation. During activation, the first ONU reads the local response time (first response time) and reports it to the OLT. The OLT records the first response time and the range result (first equalization delay) from the first ONU. When the first ONU is replaced by a second ONU, the OLT sends the first equalization delay and the first response time to the second ONU. The second ONU then recalculates and applies its own second equalization delay based on the local response time (second response time). The following operations are included. The first ONU responds to the SN request or OLT scope request and carries the first response time in the response, as shown in Table 1 below, which is the response information, message Serial_Number_ONU (ONU serial number report message), where 15 bytes of order 17-20 carry the local response time. zeon ιη / ρζηζ / Β / γίΛΐ Octet (bytes) Contents Description 1-2 0x03FF Unassigned ONU-ID. 3 0x01 Message Type ID Serial_Number_ONU. 4 0x00 Sequence Number. 5-8 VendorID The code established for Vendor ID is specified in [ATIS-0300220]. The four characters are mapped to the 4-byte field by taking each ASCII / ANSI character code and concatenating them. Example: Vendor_ID = ABCD -> Byte 5 = 0x41, Byte 6 = 0x42, Byte 7 = 0x43, Byte 8 = 0x44. 9-12 VSSN Vendor-Specific Serial Number. 13-16 Random_delay The random delay used by the ONU when sending this message, measured in bit times relative to the nominal upstream line rate of 2.48832 Gbit / s. 17-20 Response time The UN sends the local response time to the OLT. Octet (bytes) Content Description 21-40 Padding Set to 0x00 by the transmitter; treated as not matter by the receiver. 41-48 MIC Message integrity check calculated using the default PLOAM integrity key (see clause 15.8). Table 1 zeon ιη / ρζηζ / Β / γίΛΐ As shown in Table 1, bytes 1-2 are 0x03FF, which identifies the unassigned ONU-ID. Byte 3 is 0x01, which identifies the message type as an ONU serial number report message. Byte 4 is 0x00, which identifies the sequence number. Bytes 5-8 are the vendor identifier. Bytes 9-12 are the vendor serial number. Bytes 13-16 identify random delays. Bytes 17-20 identify the response time. Bytes 21-40 are padding fields. Bytes 41-48 are check fields. In Table 1, bytes 17-20 of the Serial_Number_ONU message (Uno serial number report message) were originally served as padding (padding bit) and are now modified to indicate the response time (response time), so that the response time can be reported by the Serial_Number_ONU message (Uno serial number report message). The OLT calculates the ONU's range result, records the first ONU's initial response time, and sends the range result to the first ONU according to the normal flow. The equalization delay configuration message can be a range result message (Ranging_Time message). The content of the range result message (Ranging_Time message) is shown in Table 2 below, where byte 5 is the bitmask (R bit). A bitmask set to 0 (second state) indicates that the equalization delay configuration value in bytes 6-9 (equalization delay) does not contain a response time. After receiving the range result message (Ranging_Time message), the first ONU can directly configure its initial equalization delay using the equalization delay configuration value. If the second ONU replaces the first ONU, the second equalization delay is configured for the second ONU according to Table 2. The R bit (bitmask) of byte 5 is set to 1 (first state), indicating that the equalization delay setting value, EqualizationDelay, in bytes 6-9, is the response time plus equalization delay. After receiving this message, the second ONU subtracts the local response time (second response time) from the EqualizationDelay in bytes 6-9, and the result is applied as the local equalization delay, EqD (the second equalization delay). zeon Ln / pznz / B / γΐΛΐ Octet (bytes) Contents Description 1-2 ONU-ID Message addressed to a ONU or message broadcast to all ONUs. As a broadcast to all ONUs, ONU-ID = 0x03FF. 3 0x04 Ranging_Time message type ID. 4 Seq. No. Unicast or broadcast PLOAM sequence number. 5 R000 00SP Bitmask indicating how the EqualizationDelay field is to be interpreted. R=0, EqualizationDelay does not include response time. R=1, EqualizationDelay includes response time. Bit P = 1 - Delay in bytes 6-9 is absolute; ignore S. Bit P = 0 - Delay in bytes 6-9 is relative; S determines the sign. Bit S = 0 - Positive: increases current EqD by the specified value. Bit S = 1 - Negative: decreases current EqD by the specified value. 6-9 EqualizationDelay Equalization delay value, bit times with respect to the nominal upstream line rate of 2.48832 Gbit / s. Octet (bytes) Content Description 10-40 Padding Set to 0x00 by the transmitter; treated as not important by the receiver. 41-48 MIC Message integrity check. Table 2 zeon Ln / pznz / Β / γΐΛΐ As shown in Table 2, bytes 1-2 identify the ONU-ID. Byte 3 is 0x04, which identifies the message type as a RangingTime result message. Byte 4 is the PLOAM sequence number. Byte 5 is a bitmask (with the R bit) that indicates how the EQ Delay field should be interpreted. Bytes 6-9 are the EQ Delay configuration values. Bytes 10-40 are padding fields. Bytes 41-48 are check fields. In Table 2, the first bit of byte 5 in the range result message (Ranging_Time message) is originally served as a bitmask (R bit), which is modified to identify the EqualizationDelay state of bytes 6-9, thereby improving protocol compatibility. It should be noted that, in the previous implementations, the ONU response time may or may not be fixed. That is, the response time of the same ONU during each information processing operation may be the same or different. When the ONU response time is not fixed, it is necessary to recalculate the local equalization delay each time. Situation 2: During normal UN operation, the OLT reads the UN response time. Once the activation of the first ONU is complete, the OLT can request the first response time from the first ONU through a response time acquisition request message (Request_ResponseTime message) as shown in Table 3. The first ONU can send the first response time read to the OLT through a response time feedback message (Response Time message) as shown in Table 4. Octet (bytes) Content Description 1-2 ONU-ID Message addressed to an ONU. 3 0x14 Message type ID Request_Response-Time. 4 Seq. No. Unicast PLOAM sequence number. 5-40 Padding Set to 0x00 by the transmitter; treated as do not matter by the receiver. 41-48 MIC Message integrity check calculated using the default PLOAM integrity key (see clause 15.8). Table 3 zeon ιη / ρζηζ / Β / γίΛΐ As shown in Table 3, bytes 1-2 indicate the ONU-ID. Byte 3 is 0x14, which identifies the message type as a response time acquisition request message. Byte 4 identifies the PLOAM sequence number. Bytes 5-40 are padding fields. Bytes 41-48 are check fields. Octet (byte) Contents Description 1-2 ONU-ID Sender identity 3 0x11 Message type ID Response time. 4 Sec. No. Repeated from the downstream Request_Response-Time message, or 0 if generated in response to a scope grant in scope state (04). 5-40 Response time A 36-octet string that may be useful for identifying a particular ONU installed at a particular location. The default value is an octet string of 0x00 (Note). 41-48 MIC Message integrity check calculated using the default PLOAM integrity key (see clause 15.8). Table 4 As shown in Table 4, bytes 1-2 indicate the ONU-ID. Byte 3 is 0x11, which identifies the message type as a response time feedback message. Byte 4 identifies the PLOAM sequence number. Bytes 5-40 identify the response time. Bytes 41-48 are check fields. If it is necessary to apply the equalization delay from the first ONU to the second ONU, the second ONU's equalization delay can be configured via the RangingTime message, as shown in Table 2. In such a case, the R bit (bitmask) of byte 5 of the RangingTime message is set to 1 (first state). Then, the EqualizationDelay setting value in bytes 6-9 is the first response time plus the first equalization delay. After receiving this message, the low-delay ONU subtracts the local response time (second response time) from the EqualizationDelay in bytes 6-9, and the result is applied as the local equalization delay (the second equalization delay). Situation 3: Acquisition of UN response time during the restart of the second UN. For example, in a low-delay PON network, the first ONU is a low-delay ONU, and the second ONU is a non-low-delay ONU that replaces the first. For the reboot of a non-low-delay ONU, based on scenario 2, the OLT can also acquire the second response time of the non-low-delay ONU through the message interaction shown in Tables 3 and 4. The OLT performs a local calculation to acquire the second equalization delay, that is, the second equalization delay EqD2 = RspTime1 + EqD1 - RspTime2, where RspTime1 is the first response time, EqD1 is the first equalization delay, and RspTime2 is the second response time. The second equalization delay of the non-low-delay ONU is acquired and sent to the second ONU. An embodiment of the present disclosure provides a method for time synchronization in passive optical networks; the method includes the following operations. In S4100, a response time configuration instruction is sent to a second ONU to configure the response time of the second ONU, so that the response time of the second ONU matches the response time of the first ONU. The first ONU and the second ONU access the same branch of fiber optic cable. zeon Ln / pznz / B / γΐΛΐ In some implementations, this method can be applied to an OLT and can also be applied to the factory configuration equipment for the ONU. The response time of all ONUs can be configured to be the same, so different ONUs can reuse the EqD equalization delay of other ONUs. For example, the second ONU can reuse the equalization delay of the first ONU. For example, the response time of all ONUs can be set and the ONU can obtain the response time, such as by setting the response time to the maximum value of 35+1 ps. In some implementations, the method described in this disclosure can be applied to the factory-configured equipment for OLTs. The ONU factory standard can be modified, and the response time can be adjusted to the maximum value of 35+1 ps. However, such a modification is not compatible with older equipment. In other embodiments, the method provided by some implementations of this disclosure can be applied to OLTs. Using an additional message (response-time configuration instruction), the OLT can assign the response time to the ONU. The response-time configuration instruction can be a Set_Responsetime message, as shown in Table 5 below. After receiving this message, the ONU sets the local response time to the value indicated by the Response_time field in the Set_Response-time message. zeon ιη / ρζηζ / Β / γίΛΐ Octet (byte) Contents Description 1-2 ONU-ID Message addressed to an ONU. 3 0x13 Message type ID Set_Response-Time. 4 Seq. No. Unicast PLOAM sequence number. 5-8 Response time The OLT assigns the response time to the ONU. 9-40 Padding Set to 0x00 by the transmitter; treated as not important by the receiver. Octet (byte) Content Description 41-48 MIC Message integrity check calculated using the default PLOAM integrity key (see clause 15.8). Table 5 zeon ιη / ρζηζ / Β / γίΛΐ In Table 5, bytes 1-2 indicate the ONU-ID. The third byte is 0x13, indicating that the message type is response time configuration instruction; the fourth byte is the PLOAM sequence number; bytes 5-8 are the response time; bytes 9-40 are padding fields; bytes 41-48 are check fields. In this way, the response time of each ONU is the same, and the EqD of different ONUs on the same fiber branch is also the same, so the second ONU can reuse the EqD of the first ONU. For example, a non-low-delay ONU can reuse the EqD of a low-delay ONU or a low-delay rangefinder. According to various realizations of this disclosure, the response time of the second ONU is configured through the OLT, so that the response time of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. One embodiment of this disclosure provides a method for time synchronization in passive optical networks, applicable to a second ONU. As shown in Figure 14, the method includes the following operations. In S5100, a response time configuration instruction is received. In S5200, the response time of the second ONU is configured according to the response time configuration instruction so that the response time of the second ONU matches the response time of the first ONU. The first ONU and the second ONU access the same branch of fiber optic cable. In some implementations, the response time configuration instruction may come from the OLT or it may come from the factory configuration equipment for the ONU. The response time of all ONUs can be configured to be the same, so different ONUs can reuse the EqD equalization delay of other ONUs. For example, the second ONU can reuse the equalization delay of the first ONU. For example, the response time of all ONUs can be set and the ONU can obtain the response time, such as by setting the response time to the maximum value of 35+1 ps. In some implementations, the response time configuration instruction may originate from the factory configuration equipment for the ONU. The ONU factory default can be modified, and the ONU response time can be changed to the maximum value of 35+1 ps. However, such a modification is not compatible with older equipment. In other implementations, the response time configuration instruction may originate from the OLT. Using an additional message (response time configuration instruction), the OLT can assign the response time to the ONU. This response time configuration instruction can be a Set_Response-time message, as shown in Table 5 below. Upon receiving this message, the ONU sets the local response time to the value specified by the Response_time field in the Set_Response-time message. zeon ιη / ρζηζ / Β / γίΛΐ Octet (byte) Contents Description 1-2 ONU-ID Message addressed to an ONU. 3 0x13 Message type ID Set_Response-Time. 4 Seq. No. Unicast PLOAM sequence number. 5-8 Response time The OLT assigns the response time to the ONU. 9-40 Padding Set to 0x00 by the transmitter; treated as not important by the receiver. 41-48 MIC Message integrity check calculated using the default PLOAM integrity key (see clause 15.8). Table 5 zeon ιη / ρζηζ / Β / γίΛΐ As shown in Table 5, bytes 1-2 indicate the ONU-ID. Byte 3 is 0x13, indicating that the message type is a response time configuration instruction. Byte 4 is the PLOAM sequence number. Bytes 5-8 indicate the response time. Bytes 9-40 are padding fields. Bytes 41-48 are check fields. In this way, the response time of each ONU is the same, and the EqD of different ONUs on the same fiber branch is also the same, so the second ONU can reuse the EqD of the first ONU. For example, a non-low-delay ONU can reuse the EqD of a low-delay ONU or a low-delay rangefinder. According to various realizations of this disclosure, the response time of the second ONU is configured through the OLT, so that the response time of the second ONU coincides with that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. As shown in Figure 15, one embodiment of the present disclosure provides a time synchronization device in passive optical networks; the device includes the following modules. A 110 acquisition module, which is configured to acquire a first response time from a first ONU. A calculation module 120, which is configured to perform a range calculation to the first ONU to obtain a first equalization delay. A generation module 130, which is configured to generate an equalization delay configuration message according to the first response time and the first equalization delay. A send module 140, which is configured to send an equalization delay configuration message to a second ONU to configure a second equalization delay for the second ONU. The first ONU and the second ONU access the same branch of fiber optic cable. In some embodiments, the acquisition module 110 is configured to perform the S1100 operation described above. The calculation module 120 is configured to perform the S1200 operation described above. The generation module 130 is configured to perform the S1300 operation described above. And the transmission module 140 is configured to perform the S1400 operation described above. It should be noted that the time synchronization device in passive optical networks in this embodiment can be implemented as the time synchronization device in passive optical networks in the system architecture of the embodiment shown in Figure 3. Furthermore, the time synchronization device in passive optical networks in this embodiment can perform the time synchronization method in passive optical networks in the embodiment shown in Figure 4.That is, the time synchronization device in passive optical networks in this embodiment, the time synchronization device in passive optical networks in the system architecture of the embodiment shown in Figure 3, and the time synchronization method in passive optical networks in the embodiment shown in Figure 4, shall all have the same inventive concept, so these embodiments have the same implementation principle and technical effect, and will not be described in detail at this point. The device embodiments described above are for illustrative purposes only. The units shown as separate components may or may not be physically separate; that is, they may be located in one place or distributed across several network units. Some or all of the modules may be selected according to practical requirements to achieve the purpose of this embodiment. An embodiment of the present disclosure provides an electronic apparatus, including a memory, a processor, and a computer program stored in memory and executable on the processor, which, when executed by the processor, causes the processor to carry out the method as described above. As a non-transient, computer-readable storage medium, memory can be configured to store non-transient software programs and non-transient computer executable programs. Furthermore, memory may include high-speed random-access memory and non-transient memory, such as at least one disk memory device, a flash memory device, or other non-transient solid-state memory devices. In some embodiments, memory includes memories located remotely from the processor, and these remote memories may be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof. It should be noted that the electronic device in this embodiment can be implemented as the electronic device in the system architecture of the embodiment shown in Figure 3. Furthermore, the electronic device in this embodiment can implement the time synchronization method in passive optical networks in the embodiment shown in Figure 4. That is, the electronic device in this embodiment, the electronic device in the system architecture of the embodiment shown in Figure 3, and the time synchronization method in passive optical networks in the embodiment shown in Figure 4, all must have the same inventive concept, so these embodiments have the same implementation principle and technical effect, and will not be described in detail at this point. The non-transient software programs and instructions for the time synchronization method in passive optical networks in any of the above embodiments are stored in a memory which, when executed by a processor, causes the processor to carry out the time synchronization method in passive optical networks of any of the above embodiments, for example, operations S1100 to S1400 described in conjunction with Figure 4, S1310 to S1330 described in conjunction with Figure 5, S1110 to S1120 described in conjunction with Figure 6, S2200, S2300 and S2100 described in conjunction with Figure 7, S3100 to S3200 described in conjunction with Figure 8, S3210 to S3220 described in conjunction with Figure 9, S3240, S3210 and S3220 described in conjunction with Figure 10, S3300, S3400, S3100 and S3200 described together with Figure 11, S3100, S3250, S3260 and S3270 described together with Figure 12, S3310 to S3320 described together with Figure 13, S5100 to S5200 described together with Figure 14. An embodiment of the present disclosure provides a computer-readable storage medium that stores a computer-executable instruction that, when executed by a processor, causes the processor to carry out the time synchronization method on a passive optical network as described above. In one embodiment, the computer-readable medium stores a computer-executable program which, when executed by a processor or controller (such as a processor in the diagnostic and analysis system 100), causes the processor or controller to perform the time synchronization method in passive optical networks of any one of the above embodiments, for example, operations S1100 to S1400 described in conjunction with Figure 4, S1310 to S1330 described in conjunction with Figure 5, S1110 to S1120 described in conjunction with Figure 6, S2200, S2300 and S2100 described in conjunction with Figure 7, S3100 to S3200 described in conjunction with Figure 8, S3210 to S3220 described in conjunction with Figure 9, S3240, S3210 and S3220 described in conjunction with Figure 10, S3300, S3400, S3100 and S3200 described together with Figure 11, S3100, S3250, S3260 and S3270 described together with Figure 12, S3310 to S3320 described together with Figure 13, S5100 to S5200 described together with Figure 14. An embodiment of the present disclosure provides a method for time synchronization in a PON, which applies to an OLT, the method includes acquiring a first response time from a first ONU; performing a reach calculation on the first ONU to acquire a first equalization time delay; generating an equalization delay configuration message in accordance with the first response time and the first equalization delay; sending the equalization delay configuration message to a second ONU to configure a second equalization delay of the second ONU; wherein, the first ONU and the second ONU access the same optical fiber branch.According to various embodiments of this disclosure, the equalization delay or response time of the second ONU is configured through the OLT, so that the equalization delay or response time of the second ONU matches that of the first ONU, and time synchronization can be performed when different ONUs access the fiber optic branch, thereby improving the compatibility of passive optical networks. A person skilled in the art will appreciate that all or some of the stages and systems described above can be implemented as software, firmware, hardware, and appropriate combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on computer-readable media, which may include computer storage media (or non-transient media) and communication media (or transient media).As is well known to anyone skilled in the field, the term "computer storage media" includes volatile and non-volatile, removable and non-removable media implemented using any method or technology for storing information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile discs (DVDs) or other optical disc storage, magnetic cartridges, tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store information desired and accessible by a computer.Furthermore, it is well known to experts in the field that media normally contain instructions, data structures, program modules, or other computer-readable data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any means of information delivery. The foregoing is a description of some embodiments of the present disclosure, but the embodiments of the present disclosure are not limited to the embodiments mentioned above, and those skilled in the art may make various equivalent modifications or alterations without departing from the scope of the present disclosure; such modifications or equivalent alterations fall within the scope defined by the claims of the present disclosure.

Claims

1. A time synchronization method in a passive optical network (PON), applied to an optical line terminal (OLT), the method comprising acquiring a first response time from a first optical network unit (ONU); performing a range calculation on the first ONU to acquire a first equalization time delay; generating an equalization delay configuration message according to the first response time and the first equalization delay; and sending the equalization delay configuration message to a second ONU to configure a second equalization delay for the second ONU; wherein the first ONU and the second ONU access the same optical fiber branch.

2. The method according to claim 1, wherein the equalization delay configuration message comprises the first response time and the first equalization delay; and accordingly, sending the equalization delay configuration message to the second ONU to configure the second equalization delay for the second ONU comprises sending the equalization delay configuration message to the second ONU, instructing the second ONU to calculate the second equalization delay according to the first response time, the first equalization delay, and the second response time of the second ONU.

3. The method according to claim 2, wherein the equalization delay configuration message further comprises a bitmask; and the bitmask set in a first state indicates an inclusion of both the first response time and the first equalization delay within the equalization delay configuration message.

4. The method according to claim 1, wherein the equalization delay configuration message comprises the second equalization delay; and accordingly, generating the equalization delay configuration message according to the first response time and the first equalization delay comprises, acquiring the second response time of the second ONU; calculating a second equalization delay for the second ONU according to the first response time, the first equalization delay and the second response time; and generating the equalization delay configuration message according to the second equalization delay.

5. The method according to claim 4, wherein the equalization delay configuration message further comprises a bitmask; and the bitmask set in a second state indicates an inclusion of the second equalization delay within the equalization delay configuration message.

6. The method according to any one of claims 1 to 5, wherein acquiring and recording the first response time of the first UN comprises sending to the first UN one of, an SN request, a scope request or a response time acquisition request; and receiving response information carrying the first response time from the first UN.

7. A time synchronization method in a passive optical network (PON), applicable to a first optical network unit (ONU), the method comprising sending a first response time to an optical line terminal (OLT), to instruct the OLT to perform the method according to any one of claims 1 to 6.

8. The method according to claim 7, wherein before sending the first response time to the OLT, the method further comprises acquiring from the OLT one of, an SN request, a range request or a response time acquisition request; and acquiring a local response time as a first response time according to one of, the SN request, the range request or the response time acquisition request from the OLT.

9. A time synchronization method in a passive optical network (PON), applicable to a second optical network unit (ONU), the method comprising receiving an equalization delay configuration message from an optical line terminal (OLT); and configuring a second equalization delay for the second ONU in accordance with the equalization delay configuration message; wherein the OLT acquires the second equalization delay by performing the method in accordance with any one of claims 1 to 6.

10. The method according to claim 9, wherein the equalization delay configuration message comprises the first response time and the first equalization delay; and accordingly, configuring the second equalization delay for the second ONU according to the equalization delay configuration message comprises, acquiring a second response time from the second ONU; and calculating the second equalization delay according to the first response time, the first equalization delay, and the second response time.

11. The method according to claim 10, wherein the equalization delay configuration message further comprises a bitmask; and accordingly, configuring the second equalization delay for the second ONU according to the equalization delay configuration message further comprises determining a state of the bitmask; and determining an inclusion of both the first response time and the first equalization delay within the equalization delay configuration message, in response to a determination that the bitmask is in a first state.

12. The method according to claim 11, wherein the equalization delay configuration message comprises the second equalization delay; and the method further comprises acquiring a second response time from the second ONU; and sending the second response time to the OLT, instructing the OLT to calculate the second equalization delay according to the first response time, the first equalization delay, and the second response time.

13. The method according to claim 12, wherein the equalization delay configuration message further comprises a bitmask; and accordingly, configuring the second equalization delay for the second ONU according to the equalization delay configuration message comprises, determining a state of the bitmask; determining an inclusion of the second equalization delay within the equalization delay configuration message, in response to a determination that the bitmask is in a second state; and configuring a second equalization delay for the second ONU according to the equalization delay configuration message.

14. The method according to claim 12 or claim 13, wherein acquiring the second response time of the second ONU comprises acquiring from the OLT one of, an SN request, a range request, or a response time acquisition request; and acquiring a local response time as a second response time according to one of, the SN request, the range request, or the response time acquisition request from the OLT.

15. A method for time synchronization in a passive optical network (PON), comprising sending a response time configuration instruction to a second optical network unit (ONU) to configure a response time of the second ONU such that the response time of the second ONU matches a response time of a first ONU; and wherein the first ONU and the second ONU access the same optical fiber branch.

16. A time synchronization method in a passive optical network (PON), applied to a second optical network unit (ONU), the method comprising receiving a response time configuration instruction; and configuring a response time of the second ONU in accordance with the response time configuration instruction so that the response time of the second ONU matches a response time of a first ONU; wherein the first ONU and the second ONU access the same optical fiber branch.

17. An electronic apparatus comprising a memory, a processor, and a computer program stored in the memory and executable by the processor, which, when executed by the processor, causes the processor to carry out the method according to any one of claims 1 to 16.

18. A computer-readable storage medium that stores a computer-executable instruction that, when executed by a processor, causes the processor to carry out the method according to any one of claims 1 to 16.

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