WO2018161282A1

WO2018161282A1 - Clock synchronization method and apparatus and passive optical network system

Info

Publication number: WO2018161282A1
Application number: PCT/CN2017/075992
Authority: WO
Inventors: 赵殿博; 殷锦蓉; 王苏; 隋猛
Original assignee: 华为技术有限公司
Priority date: 2017-03-08
Filing date: 2017-03-08
Publication date: 2018-09-13

Abstract

The present disclosure provides a clock synchronization method and apparatus and a passive optical network system, pertaining to the technical field of optical networks. The method is applicable to a first optical network unit (ONU) in a passive optical network (PON), the first ONU being an ONU configured with a clock source. The method comprises: synchronizing a first clock with a clock of a clock source, the first clock referring to a clock of the first ONU; and instructing an optical line terminal (OLT) to synchronize a second clock with the clock of the clock source, the second clock referring to a clock of the OLT. In the present disclosure, the first clock of the first ONU is synchronized with the clock of the clock source, and further the OLT is instructed to synchronize its own second clock with the clock of the clock source, realizing synchronization of the clocks of both the OLT and the ONU with the clock of the clock source in a scenario in which no clock source exists on the OLT side but a clock source exists on the ONU side, thus ensuring the accuracy and stability of a clock in an optical network, and further ensuring the reliability of a transmission process.

Description

Clock synchronization method, device and passive optical network system

Technical field

The present disclosure relates to the field of optical network technologies, and in particular, to a method and device for clock synchronization and a passive optical network system.

Background technique

Optical network technology is a point-to-multipoint optical fiber transmission and access technology. Generally, it can be connected by an optical line terminal (OLT), an optical network unit (ONU), an optical splitter, and the above. The fiber optic construction of the device. The OLT is used to control and manage each ONU in the optical network. The optical fiber is used to transmit data between the OLT and the ONU. The ONU is used for data interaction with the OLT to provide network services for user equipment connected to the ONU. In an optical network, in order to drive data transmission, an ONU or an OLT generally has its own clock, but in order to make the data transmission process orderly, the clocks of the OLT and the ONU are usually synchronized.

In clock synchronization, in order to ensure the accuracy of the clock in the optical network, the OLT generally obtains a clock from a high-precision clock source. The high-precision clock source can be Synchronization Ethernet (SyncE), Global Positioning System (Global). Positioning System (GPS) or single-board clock, etc., the OLT takes the acquired clock as its own working clock, and continuously transmits downlink data to the ONU according to the working clock, so that the ONU determines the clock edge through the transition edge of the downlink data, thereby acquiring the OLT. Clock. Furthermore, the ONU can use the clock of the OLT as a reference clock, and calibrate its own clock to the clock of the OLT through the phase locked loop to realize clock synchronization with the OLT.

In carrying out the process of the present disclosure, the inventors have found that the prior art has at least the following problems:

In the actual application scenario, the OLT side may not have a high-precision clock source, but a high-precision clock source exists on the ONU side. In this case, if the synchronous clock scheme of the prior art is still used, the clock of the ONU is synchronized to the clock of the OLT. Because the accuracy of the OLT's clock is not guaranteed, the clock is unstable, which may cause the transmission process to be disordered.

Summary of the invention

In order to solve the problems of the prior art, embodiments of the present disclosure provide a method, an apparatus, and a passive optical network system for clock synchronization. The technical solution is as follows:

The first aspect provides a clock synchronization method, which is applied to a first optical network unit ONU in a Passive Optical Network (PON), where the first ONU is an ONU configured with a clock source, Methods include:

Synchronizing the first clock to a clock of the clock source, where the first clock refers to a clock of the first ONU;

The optical line terminal OLT is instructed to synchronize the second clock to the clock of the clock source, and the second clock refers to the clock of the OLT.

In the embodiment of the present disclosure, the first clock of the first ONU is synchronized to the clock of the clock source, thereby instructing the OLT to synchronize the second clock of the first ONU to the clock of the clock source, so that the clock source does not exist on the OLT side, but the ONU side In the scenario of a clock source, the clocks of the OLT and the ONU are synchronized to the clock of the clock source, ensuring the accuracy and stability of the clock in the optical network, and further ensuring the reliability of the transmission process.

In a first possible implementation manner of the first aspect, the indicating that the optical line terminal OLT synchronizes the second clock to the clock of the clock source includes:

Obtaining a second clock according to the downlink data continuously sent by the OLT;

Obtaining a phase difference between the second clock and a clock of the clock source;

The phase difference is sent to the OLT.

In this implementation, the phase difference between the second clock and the clock of the clock source is obtained, and the phase difference is sent to the OLT, so that when the OLT receives the phase difference, the second clock can be synchronized to the clock source according to the phase difference. The clock provides a clock that does not exist on the OLT side, but the clock of the OLT and the ONU is synchronized to the clock source of the clock source in the scenario where the clock source exists on the ONU side. This ensures the accuracy of the clock in the optical network. Stability further ensures the reliability of the transmission process.

In a second possible implementation manner of the first aspect, the acquiring a phase difference between the second clock and the first clock includes:

Comparing the second clock and the clock of the clock source;

Obtain the phase difference obtained by comparing the relatives.

In a third possible implementation manner of the first aspect, the sending the phase difference to the OLT includes:

If the phase difference is not constant, the phase difference is sent to the OLT.

In this implementation manner, after obtaining the phase difference, it may be determined whether the phase difference is a constant. If the phase difference is constant, it may be determined that the OLT has achieved clock synchronization with the first ONU, so there is no need to send the phase difference to the OLT, if The phase difference is not constant, indicating that the clock of the current OLT is not synchronized with the clock of the ONU, and the phase difference is sent to the OLT. Through the above judgment process, it is possible to determine whether to transmit the phase difference according to the specific situation, thereby saving transmission resources in the case where the phase difference is constant.

In a fourth possible implementation manner of the first aspect, the indicating that the optical line terminal OLT synchronizes the second clock to the clock of the clock source includes:

Synchronizing data is continuously transmitted to the OLT according to a clock of the clock source, where the synchronization data is used by the OLT to acquire a clock of the clock source.

In this implementation manner, the OLT continuously sends the synchronization data to the OLT according to the clock of the clock source, so that the OLT can synchronize the second clock of the clock to the clock source of the clock source according to the continuously transmitted synchronization data, and the clock is not present on the OLT side. On the other hand, in the scenario where the clock source exists on the ONU side, the clocks of the OLT and the ONU are synchronized to the clock source of the clock source. This ensures the accuracy and stability of the clock in the optical network and further ensures the reliability of the transmission process.

In a fifth possible implementation manner of the first aspect, the continuously sending the synchronization data to the OLT according to the clock of the clock source includes:

Synchronizing data is continuously transmitted to the OLT through an out-of-band channel according to the clock of the clock source, where the wavelength corresponding to the out-of-band channel is the same as the uplink wavelength corresponding to the data channel used for transmitting the uplink data, but the out-of-band channel The corresponding circuit domain spectrum is different from the circuit domain spectrum corresponding to the data channel.

In this implementation manner, a specific method for transmitting synchronization data is provided, and the synchronization data is sent to the OLT through an outband channel, so that uplink data and synchronization data are transmitted by using different transmission resources, thereby avoiding mutual interference between the synchronization data and the uplink data.

In a sixth possible implementation manner of the first aspect, the continuously sending the synchronization data to the OLT according to the clock of the clock source includes:

Synchronous data is continuously transmitted to the OLT through additional wavelengths according to a clock of the clock source, the additional wavelength being different from the upstream wavelength.

In this implementation manner, a specific method for transmitting synchronization data is provided, and the synchronization data is sent to the OLT through an additional wavelength, so that the uplink data and the synchronization data are transmitted by using different transmission resources, thereby avoiding mutual interference between the synchronization data and the uplink data.

In a second aspect, a method for clock synchronization is provided for an optical line terminal OLT in a passive optical network PON, the method comprising:

The second clock is synchronized to the clock source of the clock source according to the instruction of the first optical line terminal ONU, the first ONU is an ONU configured with a clock source, and the second clock is a clock of the OLT;

Downstream data is continuously sent to the second ONU according to the clock of the clock source, where the second ONU is an ONU with no clock source configured.

The OLT and the ONU are implemented in the scenario that the clock source is not present on the OLT side and the clock source exists on the ONU side in the scenario that the clock source is synchronized to the clock source according to the instruction of the first ONU. The clocks are synchronized to the clock source of the clock source, ensuring the accuracy and stability of the clock in the optical network, further ensuring the reliability of the transmission process. Moreover, after the second clock is synchronized with the clock of the clock source, the downlink data may be continuously sent to the second ONU according to the clock of the clock source, so that the second ONU synchronizes its own clock to the clock of the clock source according to the downlink data, thereby realizing the light. The clock synchronization of the network system ensures the accuracy and stability of the clock of the entire system, making the transmission process more reliable.

In a first possible implementation manner of the second aspect, the clock that synchronizes the second clock to the clock source according to the indication of the first optical line terminal ONU includes:

Receiving a phase difference sent by the first ONU, where the phase difference refers to a phase difference between the second clock and a clock of the clock source;

The second clock is synchronized to a clock of the clock source according to the phase difference.

In this implementation manner, by receiving the phase difference between the second clock and the clock of the clock source, the second clock can be synchronized to the clock of the clock source according to the phase difference, and the clock is not present on the OLT side, but the ONU side is provided. In the scenario of a clock source, the clocks of the OLT and the ONU are synchronized to the clock source of the clock source. This ensures the accuracy and stability of the clock in the optical network and further ensures the reliability of the transmission process.

In a second possible implementation manner of the second aspect, the clock that synchronizes the second clock to the clock source according to the indication of the first optical line terminal ONU includes:

Receiving synchronization data continuously sent by the first ONU;

Synchronizing the second clock to a clock of the clock source according to the synchronization data.

In this implementation manner, by receiving the synchronization data continuously sent by the first ONU, the second clock can be synchronized to the clock of the clock source according to the continuously transmitted synchronization data, and the clock is not present on the OLT side, but the clock is present on the ONU side. In the source scenario, the clocks of the OLT and the ONU are synchronized to the clock source of the clock source to ensure the accuracy and stability of the clock in the optical network, which further ensures the reliability of the transmission process.

In a third possible implementation manner of the second aspect, the receiving the synchronization data continuously sent by the first ONU includes:

And receiving, by the outband channel, the synchronization data continuously sent by the first ONU, where the wavelength corresponding to the outband channel is the same as the uplink wavelength corresponding to the data channel used for transmitting the uplink data, but the circuit domain spectrum corresponding to the outband channel And The circuit domain corresponding to the data channel has a different spectrum.

In this implementation manner, a specific method for receiving synchronization data is provided, and the synchronization data is received through the outband channel, so that the uplink data and the synchronization data are received by using different transmission resources, thereby avoiding mutual interference between the synchronization data and the uplink data.

In a fourth possible implementation manner of the second aspect, the receiving the synchronization data continuously sent by the first ONU includes:

The synchronization data continuously transmitted by the first ONU is received by an additional wavelength, the additional wavelength being different from the upstream wavelength.

In this implementation manner, a specific method for receiving synchronization data is provided, and the synchronization data is received through the additional wavelength, so that the uplink data and the synchronization data are received by using different transmission resources, thereby avoiding mutual interference between the synchronization data and the uplink data.

In a third aspect, a device for clock synchronization is provided, the device comprising a method comprising at least one module for implementing clock synchronization provided by any of the possible implementations of the first aspect or the first aspect.

In a fourth aspect, a device for clock synchronization is provided, the device comprising a method comprising at least one module for implementing clock synchronization provided by any of the possible implementations of the second aspect or the second aspect.

In a fifth aspect, a passive optical network PON system is provided, the system comprising an optical line terminal OLT, a beam splitter and an optical network unit ONU, the system further comprising a clock synchronization device and a fourth aspect according to the third aspect A clock synchronization device as described in the aspect.

In the embodiment of the present disclosure, the clock source refers to a high-precision clock source, such as a SyncE, a GPS, or a single-board clock.

The phase difference is used to represent a difference portion between the second clock and the clock of the clock source, and the phase difference may be a phase difference between the clock of the second clock and the clock source, or may be a voltage value or a current value related to the phase difference. .

Synchronous data refers to continuous data with at least one edge, such as 0101...

The data channel refers to the channel for transmitting uplink data, and its corresponding upstream wavelength is generally 1310 nm.

DRAWINGS

1 is a system block diagram of a passive optical network PON according to an embodiment of the present disclosure;

2 is a schematic structural diagram of a device for clock synchronization provided by an embodiment of the present disclosure;

3A is a flowchart of a method for clock synchronization provided by an embodiment of the present disclosure;

FIG. 3B is a flowchart of a method for clock synchronization provided by an embodiment of the present disclosure; FIG.

4 is a flowchart of a method for clock synchronization provided by an embodiment of the present disclosure;

FIG. 5 is a schematic diagram of a spectrum provided by an embodiment of the present disclosure;

6 is a block diagram of a device for clock synchronization provided by an embodiment of the present disclosure;

FIG. 7 is a block diagram of a device for clock synchronization provided by an embodiment of the present disclosure.

detailed description

The embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

FIG. 1 is a system block diagram of a passive optical network PON according to an embodiment of the present disclosure. Referring to FIG. 1, the system includes at least one OLT at least one splitter and a plurality of ONUs. The OLT is connected to the ONU or the optical splitter through an optical fiber. The OLT is provided with a network interface through which the public switched telephone network (Public Switched) Telephone Network, PSTN), Internet (Internet) or Community Antenna Television (CATV) connection. During data interaction, the OLT can receive data from the network interface and broadcast the data to the ONU through the optical fiber; or, the OLT receives the data of each ONU through the optical fiber, and sends the data to the PSTN, the Internet, or the CATV through the network interface. The beam splitter is used to separate or concentrate optical signals.

One of the plurality of ONUs is an ONU (hereinafter referred to as a clock source) configured with a high-precision clock source. The clock source is used to provide a high-precision clock for the ONU, and the remaining ONUs are ONUs that are not configured with a clock source. Each ONU is provided with a network interface, so that the ONU is connected to the user equipment through the network interface, thereby transmitting data exchanged between the user and the network.

In the embodiment of the present disclosure, the ONU configured with the clock source can synchronize its own clock to the clock of the clock source, and instruct the OLT to synchronize its own clock to the clock of the clock source, thereby enabling the ONU and the OLT without the clock source to be configured. When clock synchronization is performed, it is also possible to synchronize its own clock to the clock of the clock source, thereby ensuring the accuracy and stability of the clock of the entire PON system.

FIG. 2 is a schematic structural diagram of a device for clock synchronization provided by an embodiment of the present disclosure. Referring to FIG. 2 (1), the first ONU includes at least a system clock module, a clock input module, a phase detector, and a Media Access Control (MAC) layer. The system clock module is configured to generate a clock of the first ONU itself, drive the first ONU data transmission, acquire a clock of the OLT, and input the clock of the OLT into the phase detector; the clock input module is used to input the phase to the phase detector. The clock of the precision clock source; the phase detector is configured to compare the phase difference between the two according to the clock input by the clock input module and the system clock module, and package the phase difference as a phase difference message to the MAC layer; The layer is configured to send data of the first ONU to the OLT, receive data sent by the OLT, and input the received data into the system clock module.

Referring to FIG. 2 (2), the OLT includes at least a message extraction module, a frequency synthesizer, and a system clock module MAC layer. The packet extraction module is configured to extract the data carried in the packet according to the protocol adopted by the packet, and if the phase difference carried in the phase difference packet is extracted, the packet extraction module may further input the extracted phase difference into the frequency. Synthesizer; frequency synthesizer is used to calibrate the output frequency according to the phase difference, and input the output frequency into the system clock module; the system clock module is used to obtain the output frequency of the frequency synthesizer as its own clock, and drive the data transmission of the OLT; The data between the OLT and the ONU is transmitted.

Referring to FIG. 2 (3), the second ONU includes at least a system clock module and a MAC layer. The MAC layer is configured to send data of the second ONU to the OLT, receive data sent by the OLT, and input the received data into the system clock module; the system clock module is configured to generate a clock of the second ONU itself, and continuously send according to the OLT. Downstream data, synchronizing its own clock to the clock of the OLT.

Any of the above devices may also include a switch to transmit data without conflict. Moreover, any of the above ONUs may further include an Ethernet interface and a SyncE, such that the ONU performs data interaction with the user equipment through the SyncE and the Ethernet interface.

FIG. 3A is a flowchart of a method for clock synchronization provided by an embodiment of the present disclosure. Referring to FIG. 3A, the embodiment can be applied to the PON system shown in FIG. 1. The system can include a first ONU, an OLT, and at least one second ONU. The first ONU refers to an ONU that is provided with a clock source, and second. The ONU is a clock that is not configured with a clock source. The embodiment may be: the first ONU synchronizes the clock of the clock source with the first clock of the first ONU, and instructs the OLT to synchronize its second clock to the clock of the clock source, so that the OLT When the downlink data is continuously transmitted to the second ONU according to the clock of the clock source, the second ONU can synchronize its own clock to the clock of the clock source according to the received downlink data, thereby ensuring the clock precision of the entire PON system. And stability.

FIG. 3B is a flowchart of a method for clock synchronization provided by an embodiment of the present disclosure. Referring to FIG. 3B, the embodiment can be applied to the PON system shown in FIG. 1, and specifically includes the following steps:

300. The first ONU synchronizes the first clock to a clock of a clock source, where the first clock refers to a clock of the first ONU.

In this step, the first ONU is an ONU configured with a clock source. To ensure the clock accuracy in the PON system, the first ONU tracks the clock of the clock source through the phase locked loop, thereby synchronizing the first clock to the clock of the clock source.

301. The first ONU acquires a second clock according to downlink data continuously sent by the OLT.

The second clock refers to the clock of the OLT. The OLT can receive the downlink data continuously sent by the OLT, and the first ONU can identify the edge of the downlink data, for example, The downlink data is 01010, and the first ONU can recognize a transition edge of 0 to 1 or a transition edge of 1 to 0. Since the downlink data is driven by the second clock of the OLT, the first ONU can determine the identified edge of the transition as the clock edge of the second clock, thereby determining the clock oscillation law of the OLT, and acquiring the second clock of the OLT.

302. The first ONU acquires a phase difference between the second clock and the clock of the clock source.

In this step, the first ONU may acquire a phase difference between the clock of the second clock and the clock source according to the acquired second clock and the clock of the current clock source. The embodiment of the present disclosure does not limit the process of acquiring the phase difference. For example, the first ONU compares the clock of the second clock and the clock source, and obtains the phase difference obtained by comparing the relatives. During the acquisition process, the first ONU can input the acquired second clock and the clock of the clock source into the phase detector, and compare the phase difference between the clock of the second clock and the clock source through the phase detector. It should be noted that the output of the general phase detector is a voltage value (or current value) related to the phase difference. Therefore, the “phase difference” acquired by the first ONU may also be a voltage value (or current value) related to the phase difference. ).

303. The first ONU sends the phase difference to the OLT.

Based on the phase difference acquired in step 302, the first ONU may uplink the phase difference to the OLT. In fact, the first ONU can encapsulate the phase difference into a phase difference message, so that the phase difference is sent to the OLT in the form of a message, and the protocol used by the phase difference message is not limited to the optical network unit management control interface (Optical Network) Unit Management and Control Interface (OMCI) protocol.

In a practical application scenario, the clocks of the first ONU and the OLT may also be synchronized, that is, the current clock of the first ONU is the same as the clock of the OLT, and then the phase difference between the clock of the second clock and the clock source is constant, and then The first ONU may also be in phase with the OLT, and the phase difference between the second clock and the clock of the clock source is zero. Wherein, the clock is the frequency, the oscillation law of the second clock is s in(f1*t+a), and the oscillation law of the clock of the clock source is s in(f2*t+b), then the second clock and the clock source The phase difference of the clock is t*(f1-f2)+(ab). When the second clock is the same as the clock of the clock source, f1=f2, that is, the variable t does not exist, and the phase difference no longer changes with time and is constant. In the above case, the first ONU does not need to send the phase difference to the OLT again. Therefore, in order to save transmission resources, the first ONU may first determine whether the phase difference is constant; if the phase difference is constant, determine that the OLT has been associated with the first ONU. Clock synchronization is implemented; if the phase difference is not constant, the ONU sends the phase difference to the OLT.

304. When the OLT receives the phase difference, the second clock is synchronized to the clock of the clock source according to the phase difference.

In this step, when the OLT receives the phase difference message sent by the first ONU, the phase difference message can be parsed according to the protocol adopted by the phase difference message, thereby obtaining the phase difference (the voltage value or current related to the phase difference). value). Further, the OLT may calibrate the second clock based on the phase difference, for example, calibrating the output frequency of the frequency synthesizer based on the phase difference, and making the output frequency coincide with the clock of the clock source, thereby acquiring the clock of the clock source as its own clock, and realizing The ONU's clock is synchronized. During the calibration process, if the second clock is smaller than the clock of the clock source and the phase difference is negative, the output frequency of the frequency synthesizer is increased compared to the second clock. If the second clock is greater than the clock of the clock source, the phase difference is With a positive value, the output frequency of the frequency synthesizer is reduced compared to the second clock, so that the output frequency tends to the clock of the clock source.

The embodiment of the present disclosure obtains a phase difference between the second clock and the clock of the clock source, and sends the phase difference to the OLT, so that when the OLT receives the phase difference, the second clock can be synchronized to the clock source according to the phase difference. The clock provides a specific method of synchronizing the clocks of the OLT and the ONU to the clock source of the clock source in the scenario where the clock is not present on the OLT side, and the clock is accurate and stable in the optical network. Sexuality further ensures the reliability of the transmission process.

305. The OLT continuously sends downlink data to the second ONU according to the clock of the clock source.

In this step, the second ONU is an ONU that does not have a clock source, and the downlink data refers to data when the OLT and the second ONU interact normally. In order to realize the clock synchronization of the entire PON system and further ensure the accuracy and stability of the clock of the entire system, the transmission process is more reliable, and the OLT can continuously send downlink data to the second ONU according to the clock of the synchronized clock source, of course, The OLT broadcasts the feature that the OLT continuously transmits downlink data to each ONU in the optical network.

306. When receiving the downlink data continuously sent by the OLT, the second ONU synchronizes its own clock to the clock of the clock source according to the downlink data continuously sent by the OLT.

When the second ONU receives the downlink data continuously sent by the OLT, the current clock of the OLT, that is, the clock of the clock source, may be acquired, and the acquisition process is the same as the process of acquiring the second clock by the first ONU. Furthermore, the second ONU can track the clock of the clock source through the phase locked loop, thereby synchronizing its own clock to the clock of the clock source.

When the first ONU receives the downlink data continuously sent by the OLT, the current clock of the OLT can also be obtained. At this time, the first ONU can continue to steps 302 and 303 to perform the clock synchronization process again. It should be noted that, because clock skew and clock jitter are unavoidable, in order to maintain the accuracy of the clock, the process of clock synchronization is often performed along with data transmission. The embodiment of the present disclosure does not limit the period of clock synchronization. For example, clock synchronization is performed every 125 microseconds, and the first ONU performs a relative comparison every 125 microseconds, so that the OLT can perform clock calibration every 125 microseconds.

FIG. 4 is a flowchart of a method for clock synchronization provided by an embodiment of the present disclosure. Referring to FIG. 4, the embodiment can be applied to the PON system shown in FIG. 1, and specifically includes the following steps:

400. The first ONU synchronizes the first clock to a clock of a clock source, where the first clock refers to a clock of the first ONU.

This step is the same as step 300 above.

401. The first ONU continuously sends synchronization data to the OLT according to the clock of the clock source, where the synchronization data is used by the OLT to acquire a clock of the clock source.

The first ONU and the OLT are the same as the ONU and the OLT in step 301. The synchronization data is one channel of data sent by the first ONU to the OLT separately, which is different from the uplink data, and the synchronization data has at least one edge, that is, the synchronization data includes at least one set of adjacent 01 (or 10), so that The OLT acquires the clock of the clock source based on the edge of the transition in the synchronous data.

In this step, in order to avoid mutual interference between the synchronization data and the uplink data sent by the first ONU, the synchronization data and the uplink data may use different transmission resources, such as the frequency of the circuit domain spectrum or the optical domain, and the corresponding specific transmission process. See the following two examples (1) and (2):

(1) The first ONU continuously sends synchronization data to the OLT through the outband channel according to the clock of the clock source, and the wavelength corresponding to the outband channel is the same as the uplink wavelength corresponding to the data channel used for transmitting the uplink data, but the outband channel corresponds to Electricity The path spectrum of the road domain is different from the circuit domain corresponding to the data channel.

Generally, the uplink wavelength corresponding to the data channel is 1310 nm, and the spectrum of the uplink wavelength mapped in the circuit domain can reach 2.5 GHz. Therefore, the first ONU can adjust the spectrum of the uplink data and the synchronous data, so that the spectrums of the two data are different. Thus, the OLT distinguishes two kinds of data. For example, FIG. 5 is a schematic diagram of a spectrum provided by an embodiment of the present disclosure. As shown in FIG. 5, the spectrum of the uplink data is 20M-2.5 GHz, and the spectrum of the synchronous data is 0-20M. It should be noted that the spectrum of the uplink data and the spectrum of the synchronization data may partially overlap, or the spectrum of the uplink data and the spectrum of the synchronization data do not overlap at all. For the OLT, low-frequency data can be obtained through low-pass filtering, or high-frequency data can be obtained through high-pass filtering.

(2) The first ONU continuously transmits the synchronization data to the OLT through the extra wavelength according to the clock of the clock source, and the extra wavelength is different from the uplink wavelength.

In this example, the first ONU may transmit the synchronization data by using an optical signal of an additional wavelength, and transmit the uplink data by using the optical signal of the uplink wavelength. For the OLT, the optical signals of the two wavelengths can be separated by the splitter, and the synchronous data or the uplink data is further recovered by the optical receiver.

402. When the OLT receives the synchronous data continuously sent by the first ONU, synchronizes the second clock to the clock of the clock source according to the ONU synchronization data.

In this step, the process of synchronizing the clock by the OLT according to the synchronous data is the same as the process of synchronizing the clock with the second ONU in step 306.

The embodiment of the present disclosure continuously sends synchronization data to the OLT according to the clock of the clock source, so that the OLT can synchronize its second clock to the clock of the clock source according to the continuously transmitted synchronization data, thereby providing no clock on the OLT side. In the scenario where the clock source exists on the ONU, the clocks of the OLT and the ONU are synchronized to the clock source of the clock source. This ensures the accuracy and stability of the clock in the optical network and further ensures the reliability of the transmission process.

403. The OLT continuously sends downlink data to the second ONU according to the clock of the clock source.

This step is the same as step 305.

404. When receiving the downlink data continuously sent by the OLT, the second ONU synchronizes its own clock to the clock of the clock source according to the downlink data continuously sent by the OLT.

This step is the same as step 306.

FIG. 6 is a block diagram of a device for clock synchronization provided by an embodiment of the present disclosure. Referring to Figure 6, the apparatus includes:

a synchronization module 601, configured to perform the process involved in step 300 above;

The indicating module 602 is configured to perform the process involved in the foregoing steps 301, 302 or 303.

In a possible implementation, the synchronization module 601 is further configured to perform the process involved in step 300 above.

In one possible implementation, the indication module 602 is further configured to perform the process involved in step 401 above.

FIG. 7 is a block diagram of a device for clock synchronization provided by an embodiment of the present disclosure. Referring to Figure 7, the device includes:

a synchronization module 701, configured to perform the process involved in step 304 above;

The sending module 702 is configured to perform the process involved in step 305 above.

In a possible implementation, the synchronization module 701 is further configured to perform the process involved in step 402 above.

In a possible implementation, the sending module 702 is further configured to perform the process involved in step 403 above.

It should be noted that, in the clock synchronization, the device for clock synchronization provided in the above embodiment is only illustrated by the division of each functional device. In actual applications, the function distribution may be completed by different functional devices as needed. The internal structure of the device that synchronizes the clock is divided into different functional devices to perform all or part of the functions described above. In addition, the method for the clock synchronization provided by the foregoing embodiment is the same as the method for the clock synchronization. The specific implementation process is described in detail in the method embodiment, and details are not described herein again.

The above description is only an alternative embodiment of the present disclosure, and is not intended to limit the disclosure, and any modifications, equivalents, improvements, etc., made within the spirit and principles of the present disclosure should be included in the protection of the present disclosure. Within the scope.

Claims

A method for clock synchronization is characterized in that it is applied to a first optical network unit ONU in a passive optical network PON, and the first ONU is an ONU configured with a clock source, and the method includes:

Synchronizing the first clock to a clock of the clock source, where the first clock refers to a clock of the first ONU;

The optical line terminal OLT is instructed to synchronize the second clock to the clock of the clock source, and the second clock refers to the clock of the OLT.
The method according to claim 1, wherein the instructing the optical line terminal OLT to synchronize the second clock to the clock of the clock source comprises:

Obtaining a second clock according to the downlink data continuously sent by the OLT;

Obtaining a phase difference between the second clock and a clock of the clock source;

The phase difference is sent to the OLT.
The method according to claim 2, wherein the acquiring a phase difference between the second clock and the first clock comprises:

Comparing the second clock and the clock of the clock source;

Obtain the phase difference obtained by comparing the relatives.
The method according to claim 2, wherein the sending the phase difference to the OLT comprises:

If the phase difference is not constant, the phase difference is sent to the OLT.
The method according to claim 1, wherein the instructing the optical line terminal OLT to synchronize the second clock to the clock of the clock source comprises:

Synchronizing data is continuously transmitted to the OLT according to a clock of the clock source, where the synchronization data is used by the OLT to acquire a clock of the clock source.
The method according to claim 5, wherein the continuously transmitting the synchronization data to the OLT according to the clock of the clock source comprises:

Synchronizing data is continuously transmitted to the OLT through an out-of-band channel according to the clock of the clock source, where the wavelength corresponding to the out-of-band channel is the same as the uplink wavelength corresponding to the data channel used for transmitting the uplink data, but the out-of-band channel The corresponding circuit domain spectrum is different from the circuit domain spectrum corresponding to the data channel.
The method according to claim 5, wherein the continuously transmitting the synchronization data to the OLT according to the clock of the clock source comprises:

Synchronous data is continuously transmitted to the OLT through additional wavelengths according to a clock of the clock source, the additional wavelength being different from the upstream wavelength.
A method for clock synchronization, which is applied to an optical line terminal OLT in a passive optical network PON, The methods include:

The second clock is synchronized to the clock source of the clock source according to the instruction of the first optical line terminal ONU, the first ONU is an ONU configured with a clock source, and the second clock is a clock of the OLT;

Downstream data is continuously sent to the second ONU according to the clock of the clock source, where the second ONU is an ONU with no clock source configured.
The method according to claim 8, wherein the clock that synchronizes the second clock to the clock source according to the indication of the first optical line terminal ONU comprises:

Receiving a phase difference sent by the first ONU, where the phase difference refers to a phase difference between the second clock and a clock of the clock source;

The second clock is synchronized to a clock of the clock source according to the phase difference.
The method according to claim 8, wherein the clock that synchronizes the second clock to the clock source according to the indication of the first optical line terminal ONU comprises:

Receiving synchronization data continuously sent by the first ONU;

Synchronizing the second clock to a clock of the clock source according to the synchronization data.
The method according to claim 10, wherein the receiving the synchronization data continuously sent by the first ONU comprises:

And receiving, by the outband channel, the synchronization data continuously sent by the first ONU, where the wavelength corresponding to the outband channel is the same as the uplink wavelength corresponding to the data channel used for transmitting the uplink data, but the circuit domain spectrum corresponding to the outband channel The circuit domain spectrum corresponding to the data channel is different.
The method according to claim 10, wherein the receiving the synchronization data continuously sent by the first ONU comprises:

The synchronization data continuously transmitted by the first ONU is received by an additional wavelength, the additional wavelength being different from the upstream wavelength.
A device for clock synchronization, characterized in that the device comprises:

a synchronization module, configured to synchronize a first clock to a clock of the clock source, where the first clock refers to a clock of the first ONU;

The indication module is configured to instruct the optical line terminal OLT to synchronize the second clock to the clock of the clock source, and the second clock refers to the clock of the OLT.
The apparatus according to claim 13, wherein said indication module is configured to:

Obtaining a second clock according to the downlink data continuously sent by the OLT;

Obtaining a phase difference between the second clock and a clock of the clock source;

The phase difference is sent to the OLT.
The device according to claim 14, wherein the indication module is configured to:

Comparing the second clock and the clock of the clock source;

Obtain the phase difference obtained by comparing the relatives.
The device according to claim 14, wherein the indication module is configured to:

If the phase difference is not constant, the phase difference is sent to the OLT.
The apparatus according to claim 13, wherein said indication module is configured to:

Synchronizing data is continuously transmitted to the OLT according to a clock of the clock source, where the synchronization data is used by the OLT to acquire a clock of the clock source.
The apparatus according to claim 17, wherein said indication module is configured to:

Synchronizing data is continuously transmitted to the OLT through an out-of-band channel according to the clock of the clock source, where the wavelength corresponding to the out-of-band channel is the same as the uplink wavelength corresponding to the data channel used for transmitting the uplink data, but the out-of-band channel The corresponding circuit domain spectrum is different from the circuit domain spectrum corresponding to the data channel.
The apparatus according to claim 17, wherein said indication module is configured to:

Synchronous data is continuously transmitted to the OLT through additional wavelengths according to a clock of the clock source, the additional wavelength being different from the upstream wavelength.
A device for clock synchronization, characterized in that the device comprises:

a synchronization module, configured to synchronize the second clock to a clock source of the clock source according to the indication of the first optical line terminal ONU, where the first ONU is an ONU configured with a clock source, and the second clock refers to the OLT clock;

And a sending module, configured to continuously send downlink data to the second ONU according to the clock of the clock source, where the second ONU is an ONU that is not configured with a clock source.
The apparatus according to claim 20, wherein said synchronization module is configured to:

Receiving a phase difference sent by the first ONU, where the phase difference refers to a phase difference between the second clock and a clock of the clock source;

The second clock is synchronized to a clock of the clock source according to the phase difference.
The apparatus according to claim 20, wherein said synchronization module is configured to:

Receiving synchronization data continuously sent by the first ONU;

Synchronizing the second clock to a clock of the clock source according to the synchronization data.
The apparatus according to claim 22, wherein said synchronization module is configured to:

And receiving, by the outband channel, the synchronization data continuously sent by the first ONU, where the wavelength corresponding to the outband channel is the same as the uplink wavelength corresponding to the data channel used for transmitting the uplink data, but the circuit domain spectrum corresponding to the outband channel The circuit domain spectrum corresponding to the data channel is different.
The apparatus according to claim 22, wherein said synchronization module is configured to:

The synchronization data continuously transmitted by the first ONU is received by an additional wavelength, the additional wavelength being different from the upstream wavelength.
A passive optical network PON system comprising an optical line termination OLT, a beam splitter and an optical network unit ONU, characterized in that the system further comprises a clock synchronization device according to claims 13-19 and claims A clock synchronization device as described in 20-24.