CN113489562A - ONU (optical network unit), adjusting method for outputting PTP (precision time protocol) time information by ONU and application - Google Patents
ONU (optical network unit), adjusting method for outputting PTP (precision time protocol) time information by ONU and application Download PDFInfo
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Abstract
The application provides an ONU, an ONU output PTP time information adjusting method and an application, wherein the ONU comprises: the first interface is used for connecting the ODN so as to receive clock information issued by the OLT; a second interface for connecting a lower cascade device to transmit a message to the lower cascade device; and the processor is used for recovering the clock frequency from the received clock information to synchronize the internal clock timing frequency, sending a synchronization message to the subordinate cascade equipment through the second interface, and sending the optimized synchronization message sending time to the subordinate cascade equipment after sending the synchronization message so as to smooth the PTP time phase output by the ONU to the subordinate cascade equipment. By optimizing and processing the sending time of the synchronous message, the PTP time phase output by the ONU to the lower-level cascade equipment is smooth, and the influence of the changes of the quality precision difference of the hardware of the devices such as ONU clock data recovery, phase-locked loop or crystal oscillator and the like, the working temperature, the environmental humidity and the like is further reduced.
Description
Technical Field
The application relates to the technical field of network communication, in particular to an ONU (optical network unit) and an ONU (optical network unit) output PTP (precision time protocol) time information adjusting method and application.
Background
GPON is defined by the ITU-T G.984 standard, also known as gigabit Passive optical network. In the system model, the whole system is composed of an Optical Line Terminal (OLT) at the office end, an Optical Network Unit (ONU) at the user end, and an Optical Distribution Network (odn) (Optical Distribution Network), and adopts a point-to-multipoint Network structure; the ODN is composed of a single-mode optical fiber, an optical splitter, an optical connector and other passive optical devices, and provides an optical transmission medium for physical connection between the OLT and the ONU.
In the GPON system, in the downstream direction (OLT to ONU), a signal transmitted from the OLT reaches each ONU through the ODN, so that the OLT acquires PTP clock information from the upper device, synchronizes the frequency to the downstream optical signal, and transmits time information to each ONU having the PTP function through the TOD field in the OMCI message. The ONU recovers the clock frequency from the downlink signal of the optical fiber to synchronize the internal clock timing frequency; and after receiving the OMCI message sent by the OLT, synchronizing the internal timing time by using the TOD time information contained in the OMCI message.
When the ONU propagates PTP time information to the lower cascade device, the ONU performs a PTP Master clock port function (Master), and the lower cascade device performs a PTP Slave clock port function (Slave). The ONU and the subordinate cascade equipment use an IEEE 1588 time synchronization algorithm to periodically interact message messages with time stamps (timestamps), so that a receiving end can calculate the time delay and offset of the receiving end in the network. The ONU is used as a terminal product, and due to cost pressure, the quality of chips such as clock data recovery, phase-locked loop, crystal oscillator and the like is generally not very high, and the ONU is easily interfered by environmental factors such as temperature, humidity and the like during operation, so that the jitter of the output PTP time and the quality degradation are caused.
Disclosure of Invention
The application provides an ONU, an ONU PTP time information output adjusting method and application, and aims to ensure that the PTP time phase output by the ONU is smooth.
In a first aspect, an ONU provided in the present application includes:
the first interface is used for connecting the ODN so as to receive clock information issued by the OLT;
the second interface is used for connecting the lower-level cascade equipment to transmit a synchronous message to the lower-level cascade equipment, wherein the synchronous message carries a time stamp;
and the processor is used for recovering the clock frequency from the received clock information to synchronize the internal clock timing frequency, sending a synchronization message to the subordinate cascade equipment through the second interface, acquiring the time for sending the synchronization message, optimizing the time for sending the synchronization message according to the timing frequency error, and sending the optimized time for sending the synchronization message to the subordinate cascade equipment so as to enable the PTP time phase output by the ONU to the subordinate cascade equipment to be smooth.
In a second aspect, the present application provides a method for adjusting an ONU to output PTP time information, where the method is used for the ONU, and the method includes:
receiving clock information issued by an OLT (optical line terminal) and recovering clock frequency from the received clock information to synchronize internal clock timing frequency;
sending a synchronization message to the subordinate cascading equipment through the second interface and recording the time for sending the synchronization message to the subordinate cascading equipment;
and optimizing the time for sending the synchronous message according to the timing frequency error, and sending the optimized time for sending the synchronous message to the subordinate cascade equipment.
In a third aspect, the method for adjusting PTP time information provided in the present application is used for a lower cascade device, and the method includes:
receiving a synchronization message sent by an ONU and recording the time of receiving the synchronization message;
receiving the time for sending the synchronization message after the optimization sent by the ONU;
sending a delay request message to an ONU (optical network Unit), and recording the time for sending the delay request message;
receiving the time of receiving the delay request message sent by the ONU;
calculating a time offset by combining the time of receiving the synchronization message, the time of sending the synchronization message after optimization, the time of sending the delay request message and the time of receiving the delay request message;
and correcting the PTP clock information according to the time offset.
The ONU receives clock information issued by an OLT through a first interface, recovers clock frequency from the received clock information to synchronize internal clock timing frequency, sends synchronization information to subordinate cascade equipment through a second interface, acquires time for sending the synchronization information, optimizes and processes the time for sending the synchronization information according to timing frequency error, sends the optimized and processed synchronization information sending time to the subordinate cascade equipment, and corrects PTP clock information in the subordinate cascade equipment by combining the optimized and processed synchronization information sending time. Therefore, in the application, the sending time of the synchronous message is optimized, so that the PTP time phase output by the ONU to the lower-stage cascade equipment is smooth, and further, the influence of the quality precision difference of hardware of devices such as ONU clock data recovery, phase-locked loops or crystal oscillators and the like, the change of the working temperature, the environmental humidity and the like is reduced, so that the PTP time information with smoother time phase and better quality is output under the condition of hardware with the same quality.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a diagram of a GPON system model;
fig. 2 is a diagram of a process of measuring a time offset between an ONU and a lower cascade device according to an embodiment of the present disclosure;
fig. 3 is a diagram of another process of measuring a time offset between an ONU and a downstream cascading device according to an embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
Fig. 1 is a model diagram of a GPON system. As shown in fig. 1, an OLT in a GPON system is correspondingly connected with a plurality of ONUs, a first interface of an ONU is connected with an interface of the OLT through an ODN, and a second interface of the ONU is connected with a lower-level cascade device; in the downlink direction of the GPON system, signals sent by the OLT reach each ONU through the ODN and reach corresponding lower-level cascade equipment through the corresponding ONU; in the upstream direction of the GPON system, signals sent by each ONU reach the OLT through the ODN.
The GPON system adopts IEEE 1588 for time synchronization, wherein IEEE 1588 is a Precision time Protocol (PTP-Precision Timing Protocol), which is called "Precision clock synchronization Protocol standard IEEE 1588 for network measurement and control system" and is used to synchronize clocks in a computer network. In a local area network it is possible to control the clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems. The IEEE 1588 standard defines a master-slave architecture for clock distribution, which consists of one or more clocks, but only one master clock can exist in a PTP network. 1588 basic principle of PTP operation is that synchronous data frames are periodically transmitted between master and slave clock nodes: recording the sending time and the receiving time information of the data frame, adding the time information into the data frame, enabling the slave node to acquire the time information, and calculating the time deviation between the local clock of the slave node and the master clock and the transmission delay between the network nodes, thereby correcting the local clock to be synchronous with the master clock.
In the downstream direction (from the OLT to the ONU), the OLT acquires PTP clock information (including time information and frequency, the source of the time information is from an optimal clock in the system, also called a highest level clock GMC-Grandmaster clock), that is, when the OLT acquires PTP clock information from the upper level device, the OLT performs a slave clock port function, and the upper level device performs a master clock port function. The OLT synchronizes the frequency to the downstream optical signal and sends the time information to each ONU with the PTP function through the TOD field in the OMCI message. The ONU recovers the clock frequency from the downlink signal of the optical fiber to synchronize the internal clock timing frequency; and after receiving the OMCI message sent by the OLT, synchronizing the internal timing time by using the TOD time information contained in the OMCI message.
When the ONU propagates the PTP time information to the lower cascade device, the ONU plays a PTP Master clock port function (Master), and the lower cascade device plays a PTP Slave clock port function (Slave). The ONU and the subordinate cascade equipment use an IEEE 1588 time synchronization algorithm to periodically interact message messages with time stamps (timestamps). The lower cascade device has time record, namely the time delay and the offset of the lower cascade device in the network can be calculated, and then the clock information in the lower cascade device can be corrected.
In the embodiment of the present application, time offset between an ONU and a downstream cascading device is generally measured, and clock information between the ONU and the downstream cascading device is modified by using the measured time offset. The time offset measurement process, ONU sends out a synchronization message (Sync message) containing a time stamp with the expected time Ta of the data packet transmission, which is an estimate of t1 when the synchronization message was actually transmitted. Due to Sync eliminationThe message contains the expected time of issuance instead of the actual time of issuance, so that the ONU immediately issues a Follow-Up message (Follow _ Up message) after the Sync message is issued, which also contains a timestamp that accurately records the actual time of issuance t1 of the Sync message. This is done in order to allow the message transmission and the time measurement to be performed separately and without affecting each other. The next succeeding device can calculate the time offset T from the ONU using the real emission time T1 in the Follow Up information and the real reception time T2 when receiving the Sync messageOffset,TOffsetT2-t 1-Td. The lower cascade device may correct the time of the slave clock according to the time offset. However, the time offset calculated at this time includes the delay Td caused by the network transmission, so the delay Td caused by the network transmission needs to be determined by the transmission delay measurement. The ONU may periodically send a Sync message to measure the time offset between the ONU and the downstream cascading device.
In the embodiment of the application, the lower level concatenation device sends a Delay Request message packet Delay Request at time t3 after receiving the Sync message, the Delay Request message Delay Request includes time t3 for sending the Delay Request message Delay Request, the ONU receives the Delay Request message Delay Request and records time t4 for receiving the Delay Request message Delay Request, the ONU sends time t4 for receiving the Delay Request message Delay Request to the lower level concatenation device, and the lower level concatenation device calculates Delay Td caused by network transmission by combining t1, t2, t3 and t 4.
Fig. 2 is a process diagram of measuring a time offset between an ONU and a lower cascade device according to an embodiment of the present disclosure. As shown in fig. 2, the specific process of time offset measurement between an ONU and a subordinate tandem device is as follows: the ONU sends the Sync message to the lower-level cascade equipment, measures and records the time t1 for sending the Sync message, the ONU sends the Follow _ Up message to the lower-level cascade equipment, and the Follow _ Up message carries the time t1 for sending the Sync message; the lower cascade equipment receives the Sync message and the Follow _ Up message, records the time t2 of receiving the Sync message and obtains the time t1 of sending the Sync message from the received Follow _ Up message; the lower cascade equipment sends a Delay Request message Delay Request to the ONU and records the time t3 for sending the Delay Request message Delay Request; the ONU receives the Delay Request message Delay Request and records the time t4 when the Delay Request message is received; the ONU transmits a delay request message response to the lower cascade device to transmit a time t4 at which the delay request message is received to the lower cascade device.
According to
t2－t1＝Td+Toffset
t4－t3＝Td-Toffset
Can obtain the product
Td＝(T2－T1+T4－T3)/2
Toffset＝(T2－T1－T4+T3)/2
And then the subordinate cascade device according to ToffsetThe clock information in the lower cascade device is corrected, that is, the lower cascade device corrects the clock information in the lower cascade device in combination with t1, t2, t3, and t 4.
When the ONU transmits a Sync message or receives a Delay Request message, hardware in the ONU records a real time point of message transmission. For example, when the ONU transmits the Sync message, the hardware in the ONU records the time t1 of transmitting the Sync message, and the time t1 of transmitting the Sync message is included in the Follow _ Up message and transmitted to the lower cascade device. In the conventional practice, when sending the Follow _ Up message, the time t1 of sending the Sync message is directly read from the hardware, placed in the Follow _ Up message, and then sent. In this way, when the clock error and jitter of the ONU occur, the clock error and jitter of the ONU are directly transmitted to the downstream cascade device, and therefore, even if the downstream cascade device corrects the clock information in the downstream cascade device, the clock error and jitter of the ONU are directly stored, and thus, if the time accuracy of the ONU is not high or is degraded, the time accuracy of the downstream cascade device is not high or is degraded.
In order to avoid the low time precision or the degradation of the ONU, which causes the low time precision or the degradation of the subordinate cascading devices, in the embodiment of the present application, before the time t1 at which the Sync message is sent to the subordinate cascading devices, the time t1 is optimized, the time t1 is optimized to smooth the time phase of the PTP output by the ONU to the subordinate cascading devices, and finally, the optimized time t1 of the Sync message is sent to the subordinate cascading devices, so that the subordinate cascading devices use the optimized sending time of the Sync message to correct the internal clock information. In some embodiments of the present application, the optimized sending time of the Sync message may be obtained according to a timing frequency error optimization processing, for example, the Sync message sending time t1+ the timing frequency error optimization processing is adopted to send the synchronization message.
In the ONU provided in the embodiment of the present application, the PTP time phase output by the ONU to the lower-stage cascade device is made smooth by optimizing the transmission time of the synchronization message, so that the influence of variations in the quality accuracy of hardware such as ONU clock data recovery, phase-locked loops or crystal oscillators, and the like, and the operating temperature, the ambient humidity, and the like is reduced, and PTP time information with a smoother time phase and better quality is output under the hardware condition with the same quality.
In some embodiments of the present application, a timing frequency optimization error is obtained through statistical calculation by using a timing frequency error of a current time T1 at the time of sending the Sync message and historical data of the timing frequency error before the current time T1, and then the Sync message sending time T1 after optimization processing is obtained by using the timing frequency optimization error to optimize the Sync message sending time T1, for example, T1 is T1+ F.
Thus, the present application provides another time offset measurement process between an ONU and a subordinate cascading device, and fig. 3 is a diagram of another time offset measurement process between an ONU and a subordinate cascading device according to an embodiment of the present application. As shown in fig. 3, unlike the time offset measurement process between the ONU and the lower cascade device shown in fig. 2, the ONU obtains the optimized Sync message transmission time T1 at the time T1 of the optimized Sync message after the time T1 of transmitting the Sync message, and then adds the optimized Sync message transmission time T1 to the Follow _ Up message to transmit to the lower cascade device.
In some embodiments of the present application, an ONU obtains a timing frequency error F of a current time of sending a Sync message1And counting and acquiring the timing frequency error N times before the current time by using the N +1 timing frequency errorsThe timing frequency of the Sync message current time optimizes the error. Wherein, N is more than 1, N can be 5, 6, 7, etc., and can be selected according to the actually selected statistical calculation method.
In some embodiments of the present application, a timing frequency error F of a current time of sending a Sync message is obtained1And timing frequency errors 9 times before the current time, and acquiring the timing frequency optimization errors of the current time of sending the Sync message by using the 10 timing frequency errors through statistical calculation. Using the timing frequency error F of the current time1And counting the timing frequency optimization error of the current time by 9 timing frequency errors before the current time is a specific example provided in the embodiment of the present application, and the embodiment of the present application is not limited thereto.
In some embodiments of the present application, a timing frequency error F of a current time of sending a Sync message is obtained1And forms a data pair with the time t1 of sending the Sync message (t1, F)1)0(ii) a The timing frequency error data pair 9 times before the current time is obtained, and the timing frequency error data pair 9 times before the current time is recorded as (t1, F)1)9、(t1，F1)8、(t1，F1)7、(t1，F1)6、(t1，F1)5、(t1，F1)4、(t1，F1)3、(t1，F1)2、(t1，F1)1(ii) a Combined timing frequency error F1And obtaining a timing frequency optimization error F through weighted average calculation with the timing frequency error 9 times before the current time. The calculation of the timing frequency optimization error F by weighted average is only one specific example provided in the embodiments of the present application, and is not limited thereto in the embodiments of the present application.
In some embodiments of the present application, a timing frequency error F is incorporated1And obtaining a timing frequency optimization error F through weighted average calculation with the timing frequency error 9 times before the current time, wherein the method comprises the following steps: according to the formula F ═ (t1, F)1)0*19/100+(t1，F1)1*17/100+(t1，F1)2*15/100+(t1，F1)3*13/100+(t1，F1)4*11/100+(t1，F1)5*9/100+(t1，F1)6*7/100+(t1，F1)7*5/100+(t1，F1)8*3/100+(t1，F1)91/100 weighted average calculation yields the timing frequency optimization error F.
From the above technical formula, in the present embodiment, the timing frequency error F1The timing frequency error 9 times before the current time is weighted 19/100, 17/100, 15/100 … … 1/100, and the closer to the current time when the Sync message is transmitted, the higher the weight. Timing frequency error F1The weighting 19/100, 17/100, 15/100 … … 1/100 of the timing frequency error 9 times before the current time is only a specific example provided in the embodiment of the present application, and the present application is not limited thereto, and the timing frequency error F may be adjusted according to the need or the statistical result1The weight of the timing frequency error 9 times before the current time.
In the embodiment of the application, the timing frequency error F of the current time of sending the Sync message is utilized1And a timing frequency error 9 times before the current time, the calculation utilization data being (t1, F)1)0、(t1，F1)1、(t1，F1)2、(t1，F1)3、(t1，F1)4、(t1，F1)5、(t1，F1)6、(t1，F1)7、(t1，F1)8And (t1, F)1)9When the next sending of the Sync message is carried out, the timing frequency error of the next sending of the Sync message is recorded as F1And forms a data pair with the time t1 of the next sending of the Sync message (t1, F)1)0And the data pair in the last calculation (t1, F)1)9Will be aged off and subsequent data pairs aged in sequence (t1, F)1)0→(t1，F1)1、(t1，F1)1→(t1，F1)2、(t1，F1)2→(t1，F1)3、(t1，F1)3→(t1，F1)4、(t1，F1)→(t1，F1)5、(t1，F1)5→(t1，F1)6、(t1，F1)6→(t1，F1)7、(t1，F1)→(t1，F1)8And (t1, F)1)8→(t1，F1)9. Therefore, the data volume used in the subsequent optimization processing of the synchronous message sending time is the same, and the used data can be ensured to be combined with the actual change of the data.
Based on the ONU provided by the embodiment of the present application, the embodiment of the present application further provides an adjusting method for the ONU to output PTP time information, and the adjusting method is used for the ONU. The method for adjusting the output PTP time information of the ONU provided by the embodiment of the application comprises the following steps:
receiving clock information issued by an OLT (optical line terminal) and recovering clock frequency from the received clock information to synchronize internal clock timing frequency;
sending a synchronization message to the subordinate cascading equipment through the second interface and recording the time for sending the synchronization message to the subordinate cascading equipment;
and optimizing the time for sending the synchronous message, and sending the optimized time for sending the synchronous message to a lower cascade device.
In some embodiments of the present application, an adjusting method for an ONU to output PTP time information, further includes: receiving a delay request message sent by a lower cascade device through the second interface and recording the time of receiving the delay request message;
and sending the time of receiving the delay request message to the lower cascade equipment so that the lower cascade equipment modifies the clock in the lower cascade equipment in combination with the time of receiving the delay request message.
In some embodiments of the present application, optimizing the time for sending the synchronization message includes:
recording the time for sending the synchronization message to the subordinate cascading devices as t 1;
obtaining a timing frequency error F of the current time of sending the synchronization message1And whenTiming frequency errors N times before the previous time;
a timing frequency error F according to the current time of the synchronization message1Acquiring a timing frequency optimization error F by N timing frequency errors before the current time;
and obtaining the synchronization message sending time after the optimization processing according to the T-T1 + F.
In some embodiments of the present application, a timing frequency error F of a current time of sending the synchronization message is obtained1And timing frequency errors N times before the current time, including:
obtaining a timing frequency error F of the current time of sending the synchronization message1Form a data pair with t1 (t1, F)1)0；
The timing frequency error data pair 9 times before the current time is obtained, and the timing frequency error data pair 9 times before the current time is recorded as (t1, F)1)9、(t1，F1)8、(t1，F1)7、(t1，F1)6、(t1，F1)5、(t1，F1)4、(t1，F1)3、(t1，F1)2、(t1，F1)1；
A timing frequency error F according to the current time of the synchronization message1And acquiring a timing frequency optimization error F by the timing frequency error for N times before the current time, wherein the method comprises the following steps:
combined timing frequency error F1And obtaining a timing frequency optimization error F through weighted average calculation with the timing frequency error 9 times before the current time.
In some embodiments of the present application, a timing frequency error F is incorporated1And obtaining a timing frequency optimization error F through weighted average calculation with the timing frequency error 9 times before the current time, wherein the method comprises the following steps:
according to the formula F ═ (t1, F)1)0*19/100+(t1，F1)1*17/100+(t1，F1)2*15/100+(t1，F1)3*13/100(t1，F1)4*11/100+(t1，F1)5*9/100+(t1，F1)6*7/100+(t1，F1)7*5/100+(t1，F1)8*3/100+(t1，F1)91/100 weighted average calculation yields the timing frequency optimization error F.
Based on the ONU and the adjusting method for the ONU to output the PTP time information provided by the embodiment of the application, the application also provides an adjusting method for the PTP time information. The method for adjusting the PTP time information comprises the following steps: receiving a synchronization message sent by an ONU and recording the time of receiving the synchronization message;
receiving the time for sending the synchronization message after the optimization sent by the ONU;
sending a delay request message to an ONU (optical network Unit), and recording the time for sending the delay request message;
receiving the time of receiving the delay request message sent by the ONU;
calculating a time offset by combining the time of receiving the synchronization message, the time of sending the synchronization message after optimization, the time of sending the delay request message and the time of receiving the delay request message;
and correcting the PTP clock information according to the time offset.
The 1588-PTP tester is used for testing, and the adjusting method of the PTP time information output by the ONU and the adjusting method of the PTP time information which are passed by the embodiment of the application can be used for ensuring the precision/jitter and other qualities of the ONU time information.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. An ONU, comprising:
the first interface is used for connecting the ODN so as to receive clock information issued by the OLT;
a second interface for connecting a lower cascade device to transmit a message to the lower cascade device;
and the processor is used for recovering the clock frequency from the received clock information to synchronize the internal clock timing frequency, sending a synchronization message to the subordinate cascade equipment through the second interface, acquiring the time for sending the synchronization message, optimizing the time for sending the synchronization message according to the timing frequency error, and sending the optimized time for sending the synchronization message to the subordinate cascade equipment so as to enable the PTP time phase output by the ONU to the subordinate cascade equipment to be smooth.
2. The ONU of claim 1, wherein acquiring the time for sending the synchronization message and sending the time for sending the synchronization message according to timing frequency error optimization processing, and sending the time for sending the synchronization message after the optimization processing to a subordinate tandem device comprises:
recording the time for sending the synchronization message to the subordinate cascading devices as t 1;
obtaining a timing frequency error F of the current time of sending the synchronization message1And timing frequency error N times before the current time, wherein N is more than 1;
a timing frequency error F according to the current time of the synchronization message1Acquiring a timing frequency optimization error F by N timing frequency errors before the current time;
and obtaining the optimized synchronization message sending time according to the value of T1+ F, and sending the optimized synchronization message sending time T to a lower cascade device.
3. The ONU of claim 1, wherein the processor is further configured to:
receiving a delay request message sent by a lower cascade device through the second interface and recording the time of receiving the delay request message;
and sending the time of receiving the delay request message to the lower cascade equipment so that the lower cascade equipment modifies the clock in the lower cascade equipment in combination with the time of receiving the delay request message.
4. The ONU of claim 2, wherein a timing frequency error F of a current time of sending the synchronization message is obtained1And timing frequency errors N times before the current time, including:
obtaining a timing frequency error F of the current time of sending the synchronization message1And t1 form a data pair (t1, F)1)0；
The timing frequency error data pair 9 times before the current time is obtained, and the timing frequency error data pair 9 times before the current time is recorded as (t1, F)1)9、(t1，F1)8、(t1，F1)7、(t1，F1)6、(t1，F1)5、(t1，F1)4、(t1，F1)3、(t1，F1)2、(t1，F1)1；
A timing frequency error F according to the current time of the synchronization message1Acquiring a timing frequency optimization error F by N timing frequency errors before the current time; the method comprises the following steps:
combined timing frequency error F1And obtaining a timing frequency optimization error F through weighted average calculation with the timing frequency error 9 times before the current time.
5. The ONU of claim 4, wherein the combined timing frequency error F1And obtaining a timing frequency optimization error F through weighted average calculation with the timing frequency error 9 times before the current time, wherein the method comprises the following steps:
according to the formula F ═ (t1, F)1)0*19/100+(t1，F1)1*17/100+(t1，F1)2*15/100+(t1，F1)3*13/100(t1，F1)4*11/100+(t1，F1)5*9/100+(t1，F1)6*7/100+(t1，F1)7*5/100+(t1，F1)8*3/100+(t1，F1)91/100 weighted average calculation yields the timing frequency optimization error F.
6. An adjusting method for an ONU to output PTP time information, which is used for the ONU, and comprises the following steps:
receiving clock information issued by an OLT (optical line terminal) and recovering clock frequency from the received clock information to synchronize internal clock timing frequency;
sending a synchronization message to the subordinate cascading equipment through the second interface and recording the time for sending the synchronization message to the subordinate cascading equipment;
and optimizing the time for sending the synchronous message according to the timing frequency error, and sending the optimized time for sending the synchronous message to the subordinate cascade equipment.
7. The method of claim 6, further comprising:
receiving a delay request message sent by a lower cascade device through the second interface and recording the time of receiving the delay request message;
and sending the time of receiving the delay request message to the lower cascade equipment so that the lower cascade equipment modifies the clock in the lower cascade equipment in combination with the time of receiving the delay request message.
8. The method of claim 7, wherein processing the time at which the synchronization message is sent according to timing frequency error optimization comprises:
recording the time for sending the synchronization message to the subordinate cascading devices as t 1;
obtaining a timing frequency error F of the current time of sending the synchronization message1And timing frequency errors N times before the current time;
a timing frequency error F according to the current time of the synchronization message1Acquiring a timing frequency optimization error F by N timing frequency errors before the current time;
and obtaining the synchronization message sending time after the optimization processing according to the T-T1 + F.
9. Method according to claim 8, characterized in that the timing frequency error F of the current time of sending the synchronization message is obtained1And timing frequency errors N times before the current time, including:
obtaining a timing frequency error F of the current time of sending the synchronization message1Form a data pair with t1 (t1, F)1)0；
The timing frequency error data pair 9 times before the current time is obtained, and the timing frequency error data pair 9 times before the current time is recorded as (t1, F)1)9、(t1，F1)8、(t1，F1)7、(t1，F1)6、(t1，F1)5、(t1，F1)4、(t1，F1)3、(t1，F1)2、(t1，F1)1；
A timing frequency error F according to the current time of the synchronization message1And acquiring a timing frequency optimization error F by the timing frequency error for N times before the current time, wherein the method comprises the following steps:
combined timing frequency error F1And obtaining a timing frequency optimization error F through weighted average calculation with the timing frequency error 9 times before the current time.
10. A method for adjusting PTP time information, which is used for a lower cascade device, the method comprises:
receiving a synchronization message sent by an ONU and recording the time of receiving the synchronization message;
receiving the time for sending the synchronization message after the optimization sent by the ONU;
sending a delay request message to an ONU (optical network Unit), and recording the time for sending the delay request message;
receiving the time of receiving the delay request message sent by the ONU;
calculating a time offset by combining the time of receiving the synchronization message, the time of sending the synchronization message after optimization, the time of sending the delay request message and the time of receiving the delay request message;
and correcting the PTP clock information according to the time offset.
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