CN113556203B

CN113556203B - Time synchronization method in PON system, OLT, ONU and PON system

Info

Publication number: CN113556203B
Application number: CN202110691960.7A
Authority: CN
Inventors: 张伦; 郑刚
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-03-28
Filing date: 2018-03-28
Publication date: 2022-12-13
Anticipated expiration: 2038-03-28
Also published as: RU2020135286A3; CN113556203A; CN110324104B; WO2019184733A1; RU2020135286A; CN110324104A

Abstract

The invention discloses a time synchronization method in a PON system, an OLT, an ONU and the PON system. The method comprises the following steps: the OLT broadcasts time synchronization data to the ONU, the time synchronization data including time count information and time information, the time information being associated with a time at which a local time count of the ONU reaches a count value indicated by the time count information, and the ONU receives the time synchronization data. And when the local time count of each ONU reaches the count value indicated by the time count information, performing time synchronization according to the time information. The OLT may broadcast the time synchronization data to the ONUs by broadcasting a gem port, or broadcasting an LLID, or broadcasting a PLOAM. The PON port of the OLT only needs to broadcast once, and all ONUs under the PON port can receive the time synchronization data without unicast for each ONU, thereby effectively reducing the load of the single board CPU of the OLT.

Description

Time synchronization method in PON system, OLT, ONU and PON system

Technical Field

The present invention relates to the field of optical communications, and more particularly, to a time synchronization method in a PON system, an optical line terminal, an optical network unit, and a PON system.

Background

Passive Optical Network (PON) technology is a point-to-multipoint Optical fiber access technology. The PON system may include an Optical Line Terminal (OLT), an Optical Distribution Network (ODN), and at least one Optical Network Unit (ONU). The OLT is connected with the ODN, and the ODN is connected with the ONU.

In the PON system, the time is transmitted from the OLT to the ONU in a one-way mode, and time synchronization is realized. In the prior art, an OLT sends an optical network management and control interface (OMCI) message to an ONU, where the OMCI message carries accurate sending time of the OLT, and the ONU can perform time synchronization by locally receiving the time of the OMCI message and the accurate sending time carried by the message.

In the prior art, an OLT generally sends an OMCI message to an ONU every 10 seconds, i.e., the packet sending rate is generally 1/10Hz. However, for a PON system requiring a high packet rate, for example, for a PON system requiring a packet rate of 16Hz, if 16 PON ports are provided on a board of the OLT and 64 ONUs are correspondingly provided under each PON port, each PON port needs to send 16 × 64=1024 OMCI messages per second, and each board needs to send 1024 × 16=16384 OMCI messages. This causes a large load on the single board CPU of the PON system, and even affects normal OMCI message interaction.

Disclosure of Invention

In view of this, the present application provides a time synchronization method in a PON system, an optical line terminal, an optical network unit, and a PON system, and aims to reduce a single-board CPU load caused by time synchronization in the PON system.

In a first aspect, a method for time synchronization in a PON system is provided, where the method is applied to an OLT, and the method includes: the method comprises the steps that an Optical Line Terminal (OLT) generates time synchronization data, wherein the time synchronization data comprise time counting information and time information; and the OLT broadcasts the time synchronization data to an optical network unit ONU. Wherein the time information is associated with a first time, the first time being a time when the local time count of the ONU reaches a count value indicated by the time count information. Therefore, only one time of broadcasting is needed for one PON port of the OLT, all the ONUs under the PON port can receive the time synchronization data, unicast aiming at each ONU is not needed, and therefore the load of a single-board CPU of the OLT is effectively reduced.

Wherein the time information associated with the first time may be: the time information indicates the first time, and each ONU can calculate the time when the local time count reaches the count value indicated by the time count information according to the first time; or, the time information indicates a time when the local time count of the OLT reaches the count value indicated by the time count information; or the time information indicates a second time, and a preset time difference value is formed between the second time and the first time.

The OLT can broadcast the time synchronization data to the ONU through a broadcast gem port, the time synchronization data is encapsulated in an ETH message, and the ETH message comprises a broadcast identifier; or, the OLT broadcasts the time synchronization data to the ONU through broadcasting the LLID, the time synchronization data is encapsulated in an OAM message, and the OAM message comprises a broadcast identifier; or, the OLT broadcasts the time synchronization data to the ONU through broadcasting PLOAM, the time synchronization data is encapsulated in PLOAM information, and the PLOAM information comprises a broadcast identifier.

The time counting information indicates a counting value of a superframe, and the PON system is a GPON system; or, the time count information indicates a count value of LocalTime, and the PON system is an EPON system.

Furthermore, a single board of the OLT is provided with at least two PON ports, the at least two PON ports are divided into a first PON port and a second PON port, and a preset time offset is provided between a first time when the first PON port sends data and a time when the second PON port sends data; the OLT generates time synchronization data including: the first PON port triggers the CPU interruption of the OLT; the CPU reads current time counting information and time information corresponding to a first PON port; the OLT generates first time synchronization data, wherein the first time synchronization data comprises the read time counting information and time information; the OLT determines time information corresponding to each second PON port according to the preset time deviation between the second PON port and the first PON port and the read time information; the OLT generates second time synchronization data, wherein the second time synchronization data comprises the read time counting information and the determined time information; the OLT broadcasting the time synchronization data to the ONU comprises: and the OLT broadcasts the first time synchronization data through the first PON port and broadcasts the second time synchronization data through the second PON port. The CPU interruption is triggered only through the first PON port, and the CPU interruption does not need to be triggered through the second PON port, so that the CPU interruption frequency can be further reduced, and the CPU load is further reduced.

The frequency of the first PON port triggering the CPU interrupt of the OLT is at least 16Hz, and the frequency of each PON port of the OLT broadcasting the time synchronization data to the ONU is at least 16Hz, so that an IEEE1588V2 precise time transmission protocol proposed by an IEEE protocol organization can be met, and further ns-level precision time synchronization is realized.

In a second aspect, a method for time synchronization in a PON system is provided, where the method is applied to an ONU, and the method includes: an optical network unit ONU receives time synchronization data broadcasted by an OLT, wherein the time synchronization data comprises time counting information and time information; when the local time count of the ONU reaches the count value indicated by the time count information, time synchronization is carried out according to the time information; the ONU receives the time synchronization data through a broadcast gem port channel, and the time synchronization data is encapsulated in an ETH message; or, the ONU receives the time synchronization data through a broadcast LLID channel, and the time synchronization data is encapsulated in an OAM message; or, the ONU receives the time synchronization data through a broadcast PLOAM channel, and the time synchronization data is encapsulated in a PLOAM message. Therefore, only one time of broadcasting is needed for one PON port of the OLT, all the ONUs under the PON port can receive the time synchronization data, unicast aiming at each ONU is not needed, and therefore the load of a single-board CPU of the OLT is effectively reduced.

In a third aspect, an OLT is provided, and includes: a processor for generating time synchronization data, the time synchronization data including time count information and time information; a transceiver for broadcasting the time synchronization data to an optical network unit ONU. Wherein the time information is associated with a first time, the first time being a time when the local time count of the ONU reaches a count value indicated by the time count information. Therefore, only one time of broadcasting is needed for one PON port of the OLT, all the ONUs under the PON port can receive the time synchronization data, unicast aiming at each ONU is not needed, and therefore the load of a single-board CPU of the OLT is effectively reduced.

In a fourth aspect, an ONU is provided, comprising: the receiver is used for receiving time synchronization data broadcasted by the OLT, and the time synchronization data comprises time counting information and time information; a processor, configured to perform time synchronization according to the time information when a local time count of the ONU reaches a count value indicated by the time count information; the ONU receives the time synchronization data through a broadcast gem port, and the time synchronization data is encapsulated in an ETH message; or, the ONU receives the time synchronization data by broadcasting an LLID, and the time synchronization data is encapsulated in an OAM message; or, the ONU receives the time synchronization data through broadcasting PLOAM, and the time synchronization data is encapsulated in a PLOAM message. Therefore, only one broadcast is needed for one PON port of the OLT, all the ONUs under the PON port can receive the time synchronization data, unicast for each ONU is not needed, and therefore the load of a single-board CPU of the OLT is effectively reduced.

In a fifth aspect, a time synchronization apparatus in a PON system is provided, the apparatus being applied to an OLT, and the apparatus comprising a generation module and a transceiver module, wherein the generation module is configured to generate time synchronization data, and the time synchronization data comprises time count information and time information; the transceiver module is used for broadcasting the time synchronization data to an optical network unit ONU. Wherein the time information is associated with a first time, the first time being a time when the local time count of the ONU reaches a count value indicated by the time count information. Therefore, only one time of broadcasting is needed for one PON port of the OLT, all the ONUs under the PON port can receive the time synchronization data, unicast aiming at each ONU is not needed, and therefore the load of a single-board CPU of the OLT is effectively reduced.

In a sixth aspect, a time synchronization apparatus in a PON system is provided, the apparatus is applied to an ONU, and the apparatus includes a transceiver module, configured to receive time synchronization data sent by an OLT, where the time synchronization data includes time count information and time information; a synchronization module, configured to perform time synchronization according to the time information when a local time count of the ONU reaches a count value indicated by the time count information; the ONU receives the time synchronization data through a broadcast gem port, and the time synchronization data is encapsulated in an ETH message; or, the ONU receives the time synchronization data by broadcasting an LLID, and the time synchronization data is encapsulated in an OAM message; or, the ONU receives the time synchronization data through broadcasting PLOAM, and the time synchronization data is encapsulated in a PLOAM message. Therefore, only one time of broadcasting is needed for one PON port of the OLT, all the ONUs under the PON port can receive the time synchronization data, unicast aiming at each ONU is not needed, and therefore the load of a single-board CPU of the OLT is effectively reduced.

In a seventh aspect, a PON system is provided, where the PON system includes the OLT according to the third aspect and the ONU according to the fourth aspect.

In an eighth aspect, there is provided a computer readable storage medium having stored therein computer software instructions for use by the apparatus of the fifth or sixth aspect or for use by the apparatus of the third or fourth aspect, which when run on a computer, cause the computer to perform the method of the aspects.

Drawings

Fig. 1 is a schematic diagram of a PON system according to an embodiment of the present invention;

fig. 2 is an exemplary flowchart of a time synchronization method of a PON system according to an embodiment of the present invention;

fig. 3 is a flowchart illustrating a time synchronization method of a PON system according to an embodiment of the present invention;

fig. 4 is a schematic hardware structure diagram of an OLT according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a hardware structure of an ONU according to an embodiment of the present invention;

FIG. 6 is a diagram illustrating exemplary functional blocks of a time synchronization apparatus according to an embodiment of the present invention;

FIG. 7 is a diagram illustrating another exemplary functional blocks of a time synchronization apparatus according to an embodiment of the present invention;

Detailed Description

In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.

The technical scheme of the embodiment of the invention can be applied to various Ethernet Passive Optical Networks (EPONs) and Gigabit Passive Optical Networks (GPONs), such as 10G EPON, single-wave 25G EPON, 2 x 25G EPON, single-wave 50G EPON, 2 x 50G EPON, 100G EPON and the like, GPON, XGPON, DMTWPON or other types of GPON.

Fig. 1 is a schematic diagram of an architecture of a PON system to which various embodiments of the present invention are applied, and as shown in fig. 1, the PON system 100 includes at least one OLT110, at least one ODN120, and a plurality of ONUs 130. The OLT110 provides a network side interface for the PON system 100, and the ONU130 provides a user side interface for the PON system 100, and is connected to the ODN 120. If ONU130 directly provides the user port function, it is called Optical Network Terminal (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 device and the ONU130 device, and for distributing or multiplexing data signals between the OLT110 and the ONU130.

In the PON system 100, a direction from the OLT110 to the ONUs 130 is defined as a downstream direction, and a direction from the ONUs 130 to the OLT110 is defined as an upstream direction. In the downlink direction, the OLT110 broadcasts downlink data to a plurality of ONUs 130 managed by the OLT110 in a Time Division Multiplexing (TDM) manner, and each ONU130 only receives data carrying its own identifier; in the uplink direction, the ONUs 130 communicate with the OLT110 in a Time Division Multiple Access (TDMA) manner, and each ONU130 transmits uplink data according to the Time domain resource allocated to it by the OLT 110. With the above mechanism, the downstream optical signal transmitted by the OLT110 is a continuous optical signal, and the upstream optical signal transmitted by the ONU130 is a burst optical signal.

The OLT110 is usually located in a Central Office (CO), and can collectively manage at least one ONU130 and transmit data between the ONU130 and an upper network. In particular, the OLT110 may act as an intermediary between the ONUs 130 and the upper Network (e.g., the Internet, a Public Switched Telephone Network (PSTN)), forwarding data received from the upper Network to the ONUs 130, and forwarding data received from the ONUs 130 to the upper Network, the particular configuration of the OLT110 may vary depending on the particular type of PON system 100. For example, in one embodiment, the OLT110 may include a transmitter configured to transmit downstream continuous optical signals to the ONUs 130 and a receiver configured to receive upstream optical burst signals from the ONUs 130, wherein the downstream optical signals and the upstream optical signals may be transmitted through the ODN120, although embodiments of the invention are not limited in this respect.

The OLT110 may include a board, where the board includes a TM module, a Media Access Control (MAC) module, and a Central Processing Unit (CPU). The TM receives a PPS (Pulse Per Second) signal and a clock signal, and synchronizes its own time information according to the received PPS signal and clock signal. The MAC periodically generates an interrupt at intervals according to the configured time interval, locks a local time count value (for example, a count value of a superframe may be in a GPON, and a count value of a LocalTime may be in an EPON), and simultaneously sends an interrupt notification to the CPU, and after receiving the interrupt notification, the CPU reads current local time count information of the MAC module and reads current time information of the TM.

The ONUs 130 may be distributed at customer-side locations (e.g., customer premises). The ONU130 may be a network device for communicating with the OLT110 and a user, in particular, the ONU130 may act as an intermediary between the OLT110 and the user, e.g. the ONU130 may forward data received from the OLT110 to the user and forward data received from the user to the OLT 110.

The ODN120 may be a data distribution network and may include optical fibers, optical couplers, optical splitters, or other devices. In one embodiment, the optical fiber, optical coupler, optical splitter or other device may be a passive optical device, and in particular, the optical fiber, optical coupler, optical splitter or other device may be a device that does not require power support when distributing data signals between the OLT110 and the ONUs 130. Specifically, taking an optical Splitter (Splitter) as an example, the optical Splitter may be connected to the OLT110 through a trunk optical fiber and connected to the plurality of ONUs 130 through a plurality of branch optical fibers, respectively, thereby implementing point-to-multipoint connection between the OLT110 and the ONUs 130. Additionally, in other embodiments, the ODN120 may also include one or more processing devices, such as optical amplifiers or Relay devices (Relay devices). In addition, the ODN120 may specifically extend from the OLT110 to multiple ONUs 130, but may also be configured in any other point-to-multipoint structure, and the embodiment of the present invention is not limited thereto.

A time synchronization method in a PON system is provided below, and the time synchronization method provided in the embodiment of the present invention will be described in detail below with reference to the accompanying drawings, as shown in fig. 2, the method includes steps S100 to S105, and the specific implementation manner of each step is as follows:

s100, the OLT generates time synchronization data, where the time synchronization data includes time count information and time information, the time information is associated with a first time, and the first time is a time when the local time count of the ONU reaches a count value indicated by the time count information.

In this embodiment, the association between the time information and the first time may be understood as that the time indicated by the time information and the first time have a certain relationship, and may be equal to or unequal to each other. For example, the time information associated with the first time may be: the time information may indicate a first time instant; alternatively, since the local time count of the OLT and the local time count of the ONU may be regarded as having a correlation, the time at which the local time counts of the OLT and the ONU reach the count value indicated by the time count information may also have a correlation, and the time information may be associated with the first time: the time information may further indicate a time at which the local time count of the OLT reaches the count value indicated by the time count information; alternatively, the association of the time information with the first time may be: the time information indicates a second moment, and a preset time difference value is formed between the second moment and the first moment.

When the PON system is a GPON system, the time count information may indicate a count value (also referred to as super count) of a super frame. When the PON system is an EPON system, the time count information may indicate a count value of LocalTime.

S101, the OLT broadcasts the time synchronization data to the ONU.

The OLT may broadcast time synchronization data to at least two ONUs, or may broadcast time synchronization data to all ONUs under the PON port. For example, a board of the OLT is provided with 16 PON ports, and 64 ONUs are correspondingly disposed below each PON port. For a PON port, time synchronization data may be broadcast to all ONUs (for example, 64 ONUs) under the PON port, and each ONU may receive the time synchronization data and perform time synchronization according to the time synchronization data. The message or message for carrying the time synchronization data may include a broadcast identifier, and the message or message for carrying the time synchronization data may be distinguished from a unicast message by the broadcast identifier, so that the ONU may identify the message or message as a broadcast, thereby ensuring correct reception of the ONU.

The OLT can broadcast the time synchronization data to the ONU through a broadcast gem port, and the time synchronization data is encapsulated in an ETH message; the ETH message includes a broadcast identifier.

Or, the OLT broadcasts the time synchronization data to the ONU through a Logical Link Identifier (LLID), where the time synchronization data is encapsulated in an Operation, administration and Maintenance (OAM) message; the OAM message includes a broadcast identifier.

Or, the OLT broadcasts the time synchronization data to the ONU through a broadcast physical layer Operation and management (PLOAM), and the time synchronization data is encapsulated in a PLOAM message. The PLOAM message includes a broadcast identifier.

In one embodiment, the time at which the OLT broadcasts the time synchronization data to the ONUs may be before the first time. That is, the OLT broadcasts the time synchronization data to the ONUs, and then after a period of time, when the local time count of the ONUs reaches the time of the count value indicated by the time count information, the ONUs may perform time synchronization.

In another embodiment, the time at which the OLT broadcasts the time synchronization data to the ONUs may also be equal to or after the first time. The ONU may perform corresponding compensation on the time indicated by the time information, and synchronize the time to the compensated time.

S102, the ONU receives the time synchronization data.

And after receiving the time synchronization data, the ONU extracts the time counting information and the time information in the time synchronization data and stores the time counting information and the time information in an associated manner.

And S103, when the local time count of the ONU reaches the count value indicated by the time count information, performing time synchronization according to the time information.

The ONU's local time count may be synchronized with the OLT at registration time. The local time count may also be synchronized with the OLT periodically after registration.

The ONU can receive the time synchronization data through a broadcast gem port, and the time synchronization data is encapsulated in an ETH message; as shown in table 1, an embodiment of an ETH message is shown.

TABLE 1

Or, the ONU receives the time synchronization data through broadcasting the LLID, and the time synchronization data is encapsulated in the OAM message; as shown in table 2, an embodiment of an OAM message is provided.

TABLE 2

Or, the ONU receives the time synchronization data through broadcasting PLOAM, and the time synchronization data is encapsulated in a PLOAM message. As shown in table 3, an embodiment of a PLOAM message is shown.

TABLE 3

In one embodiment, the ONU receives the time synchronization data first and stores the time counting information and the time information in the time synchronization data in an associated manner; then, the local time count of the ONU reaches the count value indicated by the time count information, and the ONU carries out time synchronization according to the time information. For example, the time of the ONU may be synchronized to the time indicated by the time information when the ONU local time count reaches the count value indicated by the time count information; or calculating the accurate time of the ONU side according to the time indicated by the time information, and setting the current time of the ONU as the accurate time when the local time count of the ONU reaches the count value indicated by the time count information.

In another embodiment, the ONU may also receive the time synchronization data when or after the ONU local time count reaches the count value indicated by the time count information. The time of ONU time synchronization may be a time when the ONU local time count value reaches a value a, and the value a may be a sum of the time count information and a preset count value. The time indicated by the time information may be the sum of the time at which the ONU local time count reaches the count value indicated by the time count information and a preset time value, or may also be the sum of the time at which the OLT local time count reaches the count value indicated by the time count information and a preset time value, and the duration of the preset time value may be set according to time needs, so that the ONU may correctly perform time synchronization.

Further describing the present solution by taking GPON as an example, the description is given by taking the time information indicating the first time as an example:

the OLT and the upper-level equipment complete time synchronization;

then calculating the time ToD-X when the OLT reaches the Xth superframe (Super Frame) (namely the local time count of the OLT reaches X);

the OLT generates time synchronization data, time counting information in the time synchronization data indicates X, and time information indicates ToD-X;

the OLT can encapsulate the time synchronization data in an ETH message, then broadcasts the ETH message to the ONU through a broadcast gem port channel, and the ONU receives the ETH message, analyzes and learns the time when the OLT reaches the Xth superframe;

or, the OLT may encapsulate the time synchronization data in a PLOAM message, and then broadcast the PLOAM message to the ONU through the broadcast PLOAM channel, and the ONU receives the PLOAM message, and analyzes and learns the time when the OLT reaches the xth superframe;

the ONU locally counts the superframes, and it can be understood that, ideally, the ONU local superframe count and the OLT local superframe count are identical, that is, the OLT and the ONU reach the xth superframe simultaneously. In some cases, there is a deviation between the ONU local superframe count and the OLT local superframe count, and the ONU may perform corresponding compensation on the ToD-X to obtain an accurate time real-ToD-X from the ONU local time count to the xth superframe.

And when the ONU reaches the Xth superframe, the ONU sets the local time as real-ToD-X and finishes time synchronization.

It can be understood that, when the ONU is registering, the count of the ONU's local superframe and the count of the OLT's superframe are synchronized. The local time of the ONU is equal to the superframe count value multiplied by the time unit of the superframe, which is the duration of one superframe and may be, for example, 125us.

The EPON is taken as an example to further describe the present solution, and the time information indicates the first time as an example to explain:

the OLT and the upper-level equipment complete time synchronization;

then calculating the time ToD-Y when the LocalTime of the OLT is Y (namely the local time count of the OLT reaches Y);

the OLT generates time synchronization data, time counting information in the time synchronization data is indication Y, and time information is indication ToD-Y;

the OLT can package the time synchronization data in an OAM message, then broadcasts the OAM message to the ONU through the broadcast LLID channel, and the ONU receives the OAM message, analyzes and learns the time ToD-Y when the LocalTime of the OLT is Y;

the ONU locally counts the time, and it can be understood that, ideally, the ONU local time count is consistent with the OLT local time count, that is, the OLT and the ONU reach the Y-th LocalTime at the same time. In some cases, the ONU local time count and the OLT local time count have a deviation, and the ONU may perform corresponding compensation on ToD-Y to obtain an accurate time real-ToD-Y from the ONU local time count to the Y-th LocalTime.

And when the LocalTime of the ONU counts to Y, the ONU sets the local time to real-ToD-Y to finish time synchronization.

It can be understood that, when the ONU is registered, the local loactime count of the ONU and the LocalTime count of the OLT are synchronized. The local time of the ONU is equal to the count value of LocalTime multiplied by the time unit of LocalTime, where the time unit of LocalTime is the time interval between two adjacent LocalTime counts, and may be 16ns, for example, or other time intervals.

In the time synchronization process of the PON system, the OLT broadcasts time synchronization data to the ONUs, for example, if 64 ONUs are correspondingly arranged under each PON port of the OLT, time synchronization data corresponds to one time, the PON port only needs to broadcast once, all the ONUs under the PON port can receive the time synchronization data, unicast aiming at each ONU is not needed, and therefore the load of a single-board CPU of the OLT is effectively reduced.

In order to further reduce the load of the single board CPU caused by time synchronization in the OLT, the number of times of interruption of the CPU for time synchronization may also be reduced.

In this embodiment, a PON port used for triggering an interrupt of a CPU of the board during time synchronization is referred to as the first PON port, and the remaining PON ports are referred to as second PON ports. A preset time deviation exists between the first moment when the first PON port sends data and the moment when the second PON port sends data. In GPON, the preset time offset is smaller than the period length of the superframe (e.g., 125 us), and in EPON, the preset time offset is smaller than the period length of LocalTime. Each second PON port may also have a preset time offset, and in each PON port on the board, the preset time offset between any two PON ports is smaller than the cycle length (e.g., the cycle length in GPON is smaller than the superframe, and the cycle length in EPON is smaller than the LocalTime). For example, a GPON has a cycle length of 125us, and it is assumed that a single board is provided with 8 PON ports, and among the 8 PON ports, one PON port is used as a first PON port, and the remaining PON ports are used as second PON ports, the first PON port may transmit data at 0us at the start of each 125us cycle, and the remaining 7 second PON ports may transmit data after 0us at the start of the 125us cycle, for example, the 7 second PON ports transmit data at 125/8us,125/8 × 2us,125/8 × 3us,125/8 × 4us,125/8 × 5us,125/8 × 6us, and 125/8 × 7us, respectively, so as to avoid each PON from transmitting data at a certain time too much, which is beneficial to reducing the load of the CPU.

As shown in fig. 3, S100 includes the steps of:

s200, the first PON port triggers the CPU interrupt of the OLT;

in an embodiment, when the counter count of the first PON port reaches a preset value, the MAC generates an interrupt notification to the CPU, so that the CPU is interrupted.

S201, when the CPU is interrupted, the CPU reads the current time counting information and the time information corresponding to the first PON port;

for example, in GPON, the CPU reads the count value X of the current superframe; in EPON, the CPU reads the count value of the current LocalTime register.

S202, the OLT generates first time synchronization data, wherein the first time synchronization data comprises read time counting information and time information;

s203, the OLT determines time information corresponding to each second PON port according to the preset time deviation between the second PON port and the first PON port and the read time information;

assuming that the read time information corresponding to the first PON port is TOD0, and the time information corresponding to the 7 second PON ports are TOD1, TOD2, TOD3, TOD4, TOD5, TOD6, and TOD7, respectively, the time information corresponding to each second PON port can be determined by the following formula:

TOD1＝TOD0+125/8us；

TOD2＝TOD0+125/8*2us；

TOD3＝TOD0+125/8*3us；

TOD4＝TOD0+125/8*4us；

TOD5＝TOD0+125/8*5us；

TOD6＝TOD0+125/8*6us；

TOD7＝TOD0+125/8*7us；

s204, the OLT generates second time synchronization data, wherein the second time synchronization data comprises the read time counting information and the determined time information;

in this embodiment, the OLT may generate 7 pieces of second time synchronization data, where each piece of second time synchronization data carries the determined TOD1, TOD2, TOD3, TOD4, TOD5, TOD6, and TOD7. Since the time count information of each PON port may be the same, the second time synchronization data further includes the determined time count information of the first PON port.

The S101 includes: and the OLT broadcasts the first time synchronization data through the first PON port and broadcasts the second time synchronization data through the second PON port. That is, each of the 7 second PON ports broadcasts the second time synchronization data corresponding to the lattice code.

In the invention, the CPU interruption is triggered only by the first PON port, and the CPU interruption is not required to be triggered by the second PON port, so that the CPU interruption times can be further reduced, and the CPU load is further reduced.

Furthermore, the frequency of the first PON port triggering the CPU interruption of the OLT is at least 16Hz, and the frequency of each PON port of the OLT broadcasting the time synchronization data to the ONU is at least 16Hz, so that the IEEE1588V2 precise time transmission protocol proposed by an IEEE protocol organization can be met, and further ns-level precision time synchronization is realized.

In the following, each PON port of the OLT broadcasts the time synchronization data to the ONUs at a frequency of 16Hz. Taking 8 PON ports on a board as an example, and 64 ONUs are correspondingly disposed under each PON port, according to the method described in the background art, each PON port needs to send 16 × 64=1024 OMCI messages per second, and all PON ports on each board need to send 1024 × 8=8192 OMCI messages. The CPU of the OLT needs to be interrupted 8192 times per second according to the prior art.

According to the method of the invention, one PON port is used as a first PON port, the other 7 PON ports are used as second PON ports, the first PON port needs to be interrupted 16 times per second, and time synchronization data are broadcasted to 64 ONUs below the first PON port once every interruption; the remaining second PON ports do not need to be interrupted, and may broadcast time synchronization data. Therefore, the CPU of the OLT only needs to be interrupted 16 times per second. Compared with the prior art, the interrupt frequency of the CPU is greatly reduced, and the load of the CPU is effectively reduced.

The invention also provides an optical line terminal OLT. As shown in fig. 4, the OLT includes a processor 310, a memory 320, a Media Access Control (MAC) chip 330, a transceiver 340, and a wavelength division multiplexer 350.

The processor 310 may be a general Central Processing Unit (CPU), a microprocessor, an application specific integrated circuit ASIC, or at least one integrated circuit, and is configured to execute related programs to implement the technical solutions provided in the embodiments of the present invention.

The Memory 320 may be a Read Only Memory (ROM), a static Memory device, a dynamic Memory device, or a Random Access Memory (RAM). The memory 320 may store an operating system and other application programs. When the technical solution provided by the embodiment of the present invention is implemented by software or firmware, a program code for implementing the technical solution provided by the embodiment of the present invention is stored in the memory 320 and executed by the processor 310.

In one embodiment, the processor 310 may include memory 320 therein. In another embodiment, the processor 310 and the memory 320 are two separate structures.

In one embodiment, processor 310 and MAC chip 330 may be two separate structures. In another embodiment, MAC chip 330 may be included in processor 310.

Transceiver 340 may include an optical transmitter and/or an optical receiver. The optical transmitter may be used to transmit optical signals and the optical receiver may be used to receive optical signals. The light emitter may be implemented by a light emitting device, such as a gas laser, a solid laser, a liquid laser, a semiconductor laser, a direct modulation laser, and the like. The optical receiver may be implemented by a photodetector, such as a photodetector or a photodiode (e.g., an avalanche diode), etc. The transceiver 340 may also include a digital-to-analog converter and an analog-to-digital converter. The transceiver 340 may also include the PON port in the various embodiments described above.

Wavelength division multiplexer 350 is connected to transceiver 340 and functions as a multiplexer when OLT300 transmits an optical signal. When OLT300 receives an optical signal, the wavelength division multiplexer acts as a demultiplexer. Wavelength division multiplexers may also be referred to as optical couplers.

As can be seen from the above embodiments, the processor 310 of the OLT is configured to perform steps S100, S201, S202, S203, S204, and the transceiver 340 is configured to perform steps S101, S200.

For more details of the steps executed by the processor 310 and the transceiver 340, reference may be made to the description of the embodiments of the method and the related drawings, and further description is omitted here.

The embodiments of the present invention also have various beneficial effects described in the above embodiments of the method, and are not described herein again.

The invention also provides an optical line terminal ONU400. As shown in fig. 5, the ONU400 includes a processor 410, a memory 420, a Medium Access Control (MAC) chip 430, a transceiver 440, and a wavelength division multiplexer 450.

The processor 410 may be a general-purpose Central Processing Unit (CPU), a microprocessor, an application specific integrated circuit ASIC, or at least one integrated circuit, and is configured to execute related programs to implement the technical solutions provided in the embodiments of the present invention.

The Memory 420 may be a Read Only Memory (ROM), a static Memory device, a dynamic Memory device, or a Random Access Memory (RAM). The memory 420 may store an operating system and other application programs. When the technical solution provided by the embodiment of the present invention is implemented by software or firmware, a program code for implementing the technical solution provided by the embodiment of the present invention is stored in the memory 420 and executed by the processor 410.

In an embodiment, the processor 410 may include memory 420 therein. In another embodiment, processor 410 and memory 420 are two separate structures.

In one embodiment, processor 410 and MAC chip 430 may be two separate structures. In another embodiment, MAC chip 430 may be included in processor 410.

The transceiver 440 may include an optical transmitter and/or an optical receiver. The optical transmitter may be used to transmit optical signals and the optical receiver may be used to receive optical signals. The light emitter may be implemented by a light emitting device, such as a gas laser, a solid laser, a liquid laser, a semiconductor laser, a direct modulation laser, and the like. The optical receiver may be implemented by a photodetector, such as a photodetector or a photodiode (e.g., an avalanche diode), etc. The transceiver 440 may also include a digital-to-analog converter and an analog-to-digital converter.

The wavelength division multiplexer 450 is connected to the transceiver 440, and functions as a multiplexer when the ONU400 transmits an optical signal. When the ONU400 receives an optical signal, the wavelength division multiplexer functions as a demultiplexer. Wavelength division multiplexers may also be referred to as optical couplers.

As can be seen from the above embodiments, the processor 410 of the ONU is configured to execute step S103, and the transceiver 440 is configured to execute step S102.

For more details of the steps executed by the processor 410 and the transceiver 440, reference may be made to the description of the embodiments of the method and the accompanying drawings, which are not repeated herein.

The embodiments of the present invention also have various beneficial effects described in the above method embodiments, and details are not repeated herein.

The present invention also provides a time synchronization apparatus 500 in the PON system. The apparatus can be applied to an OLT. As shown in fig. 6, the apparatus includes: as can be seen from the foregoing embodiments, the generating module 501 of the OLT is configured to execute steps S100, S202, and S204, and the transceiver module 502 is configured to execute steps S101 and S200. The reading module 503 is configured to execute S201, and the determining module 504 is configured to execute S203.

For more details of the steps executed by each module of the apparatus, reference may be made to the relevant description of each embodiment of the method and the accompanying drawings, which are not described herein again.

The present invention also provides a time synchronization apparatus 600 in the PON system. The apparatus may be applied to an ONU. As shown in fig. 7, the apparatus includes: the transceiver module 601 and the synchronization module 602, as can be seen from the above embodiments, the transceiver module 601 of the OLT is configured to execute step S102. The synchronization module 602 is configured to execute step S103.

For more details of the steps executed by each module of the apparatus, reference may be made to the description of each embodiment of the method and the accompanying drawings, which are not described herein again.

The invention also provides a PON system, which comprises the optical line terminal and the optical network unit.

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

In summary, the above description is only an example of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for time synchronization in a PON system, the method comprising:

an Optical Line Terminal (OLT) generates time synchronization data, wherein the time synchronization data comprise time counting information and time information, the time information is associated with a first moment, and the first moment is the moment when the local time count of the OLT reaches a count value indicated by the time counting information;

the OLT broadcasts the time synchronization data to an optical network unit ONU;

the single board of the OLT is provided with at least two PON ports, the at least two PON ports are divided into a first PON port and a second PON port, and a preset time deviation exists between a first moment when the first PON port sends data and a moment when the second PON port sends data; the OLT generates the time synchronization data and comprises:

the first PON port triggers the CPU interruption of the OLT;

the CPU reads the current time counting information and the time information corresponding to the first PON port;

the OLT generates first time synchronization data, wherein the first time synchronization data comprise the read time counting information and time information;

the OLT determines time information corresponding to each second PON port according to the preset time deviation between the second PON port and the first PON port and the read time information;

the OLT generates second time synchronization data, which includes the read time count information and the determined time information.

2. The method of claim 1, wherein the time information indicates the first time instant; or the time information indicates a time when the local time count of the ONU reaches the count value indicated by the time count information; or the time information indicates a second time, and a preset time difference value is formed between the second time and the first time.

3. The method of claim 1 or 2, wherein the OLT broadcasting the time synchronization data to the ONUs comprises:

the OLT broadcasts the time synchronization data to the ONU through a broadcast gem port, and the time synchronization data is encapsulated in an ETH message;

or, the OLT broadcasts the time synchronization data to the ONU through broadcasting the LLID, and the time synchronization data is packaged in an OAM message;

or, the OLT broadcasts the time synchronization data to the ONU through broadcasting PLOAM, and the time synchronization data is encapsulated in a PLOAM message.

4. The method of claim 3, wherein said ETH message includes a broadcast identification; or, the OAM message includes a broadcast identifier; alternatively, the PLOAM message includes a broadcast identity.

5. The method of claim 1, wherein the time count information indicates a count value of superframes, the PON system being a GPON system; or, the time count information indicates a count value of LocalTime, and the PON system is an EPON system.

6. The method of claim 1, wherein a frequency at which the first PON port triggers the CPU interrupt of the OLT is at least 16Hz, and a frequency at which each PON port of the OLT broadcasts the time synchronization data to the ONUs is at least 16Hz.

7. A method of time synchronization in a PON system, the method comprising:

an optical network unit ONU receives time synchronization data broadcasted by an optical line terminal OLT, wherein the time synchronization data comprises time counting information and time information;

the ONU receives second time synchronization data broadcasted by the OLT;

the time information is associated with a first time, and the first time is the time when the local time count of the OLT reaches the count value indicated by the time count information; the single board of the OLT is provided with at least two PON ports, the at least two PON ports are divided into a first PON port and a second PON port, and a preset time deviation exists between a first moment when the first PON port sends data and a moment when the second PON port sends data; the OLT generates time synchronization data including: the first PON port triggers the CPU interrupt of the OLT; the CPU reads the current time counting information and the time information corresponding to the first PON port; the OLT generates first time synchronization data, wherein the first time synchronization data comprises the read time counting information and time information; the OLT determines time information corresponding to each second PON port according to the preset time deviation between the second PON port and the first PON port and the read time information; the OLT generates second time synchronization data, wherein the second time synchronization data comprises the read time counting information and the determined time information;

and the ONU carries out time synchronization according to the time information when the local time count of the ONU reaches a first count value, wherein the first count value is the count value indicated by the time count information, or the first count value is the sum of the count value indicated by the time count information and a preset count value.

8. The method of claim 7, wherein the ONU receives the time synchronization data by broadcasting a gem port, the time synchronization data being encapsulated in an ETH message; or, the ONU receives the time synchronization data by broadcasting an LLID, and the time synchronization data is encapsulated in an OAM message; or, the ONU receives the time synchronization data through broadcasting PLOAM, and the time synchronization data is encapsulated in a PLOAM message.

9. The method according to claim 7 or 8, wherein the frequency at which the ONU receives the time synchronization data broadcast from the same PON port of the OLT is at least 16Hz.

10. An optical line terminal, OLT, characterized in that the OLT comprises:

a processor configured to generate time synchronization data, where the time synchronization data includes time count information and time information, where the time information is associated with a first time at which a local time count of the OLT reaches a count value indicated by the time count information;

a transceiver for broadcasting the time synchronization data to an optical network unit ONU;

the transceiver comprises at least two PON ports, the at least two PON ports are divided into a first PON port and a second PON port, and a preset time deviation exists between a first moment when the first PON port sends data and a moment when the second PON port sends data;

the first PON port triggers the processor interrupt;

the processor reads current time counting information and time information corresponding to the first PON port;

the processor generating first time synchronization data, the first time synchronization data including the read time count information and time information;

the processor determines time information corresponding to each second PON port according to the preset time deviation between the second PON port and the first PON port and the read time information;

the processor generates second time synchronization data including the read time count information and the determined time information.

11. The OLT of claim 10, wherein the time information indicates the first time, or the time information indicates a time at which a local time count of the ONU reaches a count value indicated by the time count information, or the time information indicates a second time, the second time having a preset time difference from the first time.

12. The OLT of claim 10 or 11, wherein the transceiver broadcasts the time synchronization data to the ONUs via a broadcast gem port, the time synchronization data being encapsulated in an ETH message;

or, the transceiver broadcasts the time synchronization data to the ONU by broadcasting LLID, and the time synchronization data is encapsulated in an OAM message;

or, the transceiver broadcasts the time synchronization data to the ONU through broadcasting PLOAM, and the time synchronization data is encapsulated in a PLOAM message.

13. The OLT of claim 10, wherein the first PON port triggers the processor interrupt at a frequency of at least 16Hz, and wherein each PON port of the OLT broadcasts the time synchronization data to the ONUs at a frequency of at least 16Hz.

14. An optical network unit, ONU, comprising:

the system comprises a transceiver and a receiver, wherein the transceiver is used for receiving time synchronization data broadcasted by an optical line terminal OLT, and the time synchronization data comprises time counting information and time information;

the ONU receives second time synchronization data broadcast by the OLT;

the time information is associated with a first time, and the first time is the time when the local time count of the OLT reaches the count value indicated by the time count information; the single board of the OLT is provided with at least two PON ports, the at least two PON ports are divided into a first PON port and a second PON port, and a preset time deviation exists between a first moment when the first PON port sends data and a moment when the second PON port sends data; the OLT generates time synchronization data including: the first PON port triggers the CPU interrupt of the OLT; the CPU reads current time counting information and time information corresponding to a first PON port; the OLT generates first time synchronization data, wherein the first time synchronization data comprises the read time counting information and time information; the OLT determines time information corresponding to each second PON port according to the preset time deviation between the second PON port and the first PON port and the read time information; the OLT generates second time synchronization data, wherein the second time synchronization data comprises the read time counting information and the determined time information;

and the processor is used for carrying out time synchronization according to the time information when the local time count of the ONU reaches a first count value, wherein the first count value is the count value indicated by the time count information, or the first count value is the sum of the count value indicated by the time count information and a preset count value.

15. The ONU of claim 14, wherein the ONU receives the time synchronization data by broadcasting a gem port, the time synchronization data being encapsulated in an ETH message; or, the ONU receives the time synchronization data by broadcasting an LLID, and the time synchronization data is encapsulated in an OAM message; or, the ONU receives the time synchronization data through broadcasting PLOAM, and the time synchronization data is encapsulated in a PLOAM message.

16. The ONU of claim 14 or 15, wherein the frequency at which the ONU receives the time-synchronization data broadcast from the same PON port of the OLT is at least 16Hz.

17. A passive optical network, PON, system comprising an OLT according to any of claims 10 to 13 and an ONU according to any of claims 14 to 16.