CN114826475A - Method for realizing high-precision time-frequency synchronization in Ethernet communication network - Google Patents
Method for realizing high-precision time-frequency synchronization in Ethernet communication network Download PDFInfo
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- CN114826475A CN114826475A CN202210547576.4A CN202210547576A CN114826475A CN 114826475 A CN114826475 A CN 114826475A CN 202210547576 A CN202210547576 A CN 202210547576A CN 114826475 A CN114826475 A CN 114826475A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0602—Systems characterised by the synchronising information used
- H04J3/0617—Systems characterised by the synchronising information used the synchronising signal being characterised by the frequency or phase
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
- H04J14/0202—Arrangements therefor
- H04J14/0213—Groups of channels or wave bands arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0658—Clock or time synchronisation among packet nodes
- H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
- H04J3/0667—Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
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Abstract
The invention discloses a method for realizing high-precision time frequency synchronization in an Ethernet communication network by fusion, which utilizes wavelength division multiplexing to fuse high-precision time frequency reference signals into Ethernet data; the exchange networking of Ethernet data and continuous time-frequency signals is realized by utilizing the add-drop multiplexing; and realizing the time-frequency signal accurate synchronization between the local node and the terminal node by utilizing bidirectional return control. The invention utilizes the networking data transmission advantage of the Ethernet, completes high-speed interconnection communication and simultaneously realizes high-precision time-frequency transmission and exchange. The invention further improves the time frequency synchronization performance of the Ethernet and better meets the requirements of distributed detection application on high-speed data communication, high-precision time, frequency and phase synchronization.
Description
Technical Field
The invention relates to the field of synchronous Ethernet, in particular to a method for realizing high-precision time-frequency synchronization in an Ethernet communication network in a fusion way.
Background
The time synchronization protocol of the ethernet goes through the development from ntp (network time protocol) to ptp (precision time protocol), and the synchronization precision thereof is also improved from millisecond level to nanosecond level. The White Rabbit protocol developed in recent years measures master-slave clock time delay through a digital double mixing time difference method, so that the precision of PTP is further improved to tens of picoseconds, and the requirements of multiple nodes of a large scientific device on high-precision time synchronization can be met, such as a large hadron collider in Europe, a large high-altitude air shower observation station in China and the like.
High-precision optical fiber time-frequency transmission is taken as a time-frequency transmission mode with the highest transmission precision at present, and has made a lot of important progress in application independent of Ethernet. And the transmission of similar networks is realized by means of multi-point downloading, uploading and the like in linear and ring networks, and compared with the Ethernet, the precision is high but the networking degree is limited.
Zhan Lu, Youzhen Gui, Jialiang Wang, Kang Ying Sun, yang Sun, Lei Liu, Nan Cheng, and Haiwen Cai, "Fiber-optical time-frequency transfer in gigabit ethernet networks over urethane Fiber links," op.express 29, 2021, 29 (8): 11693-11701, a new optical pulse amplitude modulation scheme based on White rabbitprotocol is proposed. The essence of the scheme is that a gigabit Ethernet-based White Rabbit module is adopted to realize time transmission, frequency transmission is realized by adopting a 100MHz radio frequency modulation and bidirectional compensation mode, and a radio frequency signal and a WR (White Rabbit) signal are fused together by optical and pulse intensity modulation in a Mach-Zehnder interferometer modulator, so that ultrastable time-frequency signals and gigabit Ethernet data transmission under the same laser wavelength are completed. The stable transmission of the frequency reference is also realized by modulating and transmitting the frequency reference signal while realizing the time synchronization of tens of picoseconds. This is in line with the frequency synchronization requirement that many distributed detection systems also propose on the basis of time synchronization.
However, since the time signal is a digitized signal and the frequency signal is a continuous analog signal, the difference between the two signals must be considered in the large-scale networking exchange of the ethernet, the digitized time signal can be exchanged together with the communication data in the form of an IP packet, and if the frequency signal with the continuous analog characteristic is also used in this way, the continuity of the frequency reference is lost, and a different exchange method must be used.
Disclosure of Invention
The invention aims to meet the application requirements and provides a method for realizing high-precision time-frequency synchronization in an Ethernet communication network in a fusion manner.
The purpose of the invention is realized by the following technical scheme:
a method for realizing high-precision time frequency synchronization in an Ethernet communication network by fusion, which utilizes wavelength division multiplexing to fuse a high-precision time frequency reference signal into Ethernet data; the exchange networking of Ethernet data and continuous time-frequency signals is realized by utilizing the add-drop multiplexing; and realizing the time-frequency signal accurate synchronization between the local node and the terminal node by utilizing bidirectional return control. The method specifically comprises the following steps:
1) the reference frequency signal and the reference time signal are modulated onto laser carriers with different wavelengths, and are fused onto the data communication wavelength of the Ethernet through wavelength division multiplexing, so that the reference frequency signal and the reference time signal are transmitted in the same optical fiber with the Ethernet communication data, and after the receiving end carries out wavelength division multiplexing, the time signal, the frequency signal and the communication data are obtained through demodulation;
2) step 1) the communication data completes route planning selection, network management and control signal uploading and downloading at a switching node in an IP packet mode;
step 1) the time frequency signal enters the next node in an optical-electrical-optical cascade mode, namely the time frequency signal is demodulated through photoelectric conversion after reaching the node and is transmitted back to the previous node to enable a link between the two nodes to be independently stabilized, so that a high-quality time frequency signal is obtained at the node, then the time frequency signal is converted into an optical signal through the photoelectric conversion, and the optical signal is transmitted to the next node determined by a route through an optical switch, so that the time frequency signal is continuously and accurately switched and cascaded;
3) the frequency signal in the step 2) obtains the noise of the link by a round-trip phase measurement mode, and then actively compensates the phase fluctuation caused by the noise by a delay line device to realize the stable transmission and synchronization of the frequency signal;
and 2) the time signal adopts a spread spectrum measurement method to realize high-precision time delay measurement of the PPS time pulse signal, then time delay calibration is carried out to realize high-precision time synchronization, and absolute consistency of time information is realized through time pulse sequence marking and real-time communication interaction.
Further, the reference time signal and the reference frequency signal in the step 1) are generated by a high-precision atomic clock.
Further, the time signal and the frequency signal in the step 1) are demodulated and recovered through a photoelectric detector, and the communication data are demodulated and recovered through a modem.
Furthermore, the delay line device is an optical fiber delay line driven by a circuit, and comprises a fast-changing delay line and a slow-changing delay line.
Furthermore, the spread spectrum measurement method is to spread the 1PPS time signal into N PPS time signals, and take the average value of the N time delays as the final time delay value.
Further, the time pulse sequence marking principle is as follows: and after the system is started, counting the second according to the trigger of the rising edge of the frequency division 1PPS time pulse, and finally forming the time information from day to picosecond by combining the time delay value measured in the transmission process.
Compared with the prior art, the invention has the following beneficial effects:
by utilizing the advantages of networking data transmission and high-precision optical fiber time-frequency transmission of the Ethernet, high-speed interconnection communication is completed, high-precision time-frequency transmission and exchange are realized, and the time frequency synchronization performance of the Ethernet is further improved.
Drawings
Fig. 1 is a schematic diagram of an embodiment of implementing high-precision time-frequency synchronization in an ethernet communication network according to the present invention.
Fig. 2 is a schematic diagram of fusion, transmission and exchange of time-frequency signals and communication data in the embodiment of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples and drawings, but the scope of the present invention should not be limited thereto.
Referring to fig. 1, fig. 1 is a schematic diagram of an embodiment of implementing high-precision time-frequency synchronization in an ethernet communication network according to the present invention, where as shown in the figure, the ethernet network in this embodiment includes 1 local node, 3 switching nodes and 1 terminal node, and an adopted communication rate is 115.2 MHz. Fig. 2 is a schematic diagram of fusion, transmission and exchange of time-frequency signals and communication data in the embodiment of the present invention, where the reference time-frequency source is provided by a rubidium atomic clock, the reference time signal is a 1PPS signal output by the rubidium atomic clock, and the reference frequency signal is a 1GHz frequency signal generated by frequency doubling of 10MHz frequency output by the rubidium atomic clock. The fusion realization of high-precision time frequency synchronization in the Ethernet communication network comprises the following steps:
1. the reference 1GHz frequency signal and the reference 1PPS time signal are modulated onto laser carriers with different wavelengths through a laser, and are fused onto the data communication wavelength of the Ethernet through a wavelength division multiplexer, so that the Ethernet communication data are transmitted in the same optical fiber, and after the receiving end performs wavelength division multiplexing, the 1PPS time signal, the 1GHz frequency signal and the communication data are obtained through demodulation;
2. step 1, the communication data completes route planning selection, network management and control signal uploading and downloading at a switching node in a packet mode;
3. step 1, the 1PPS time signal and the 1GHz frequency signal enter a next node in an optical-electrical-optical cascade mode, namely, the 1PPS time signal and the 1GHz frequency signal are demodulated through a photoelectric detector after arriving at the node and are transmitted back to the previous node to enable a link between the two nodes to be independently stabilized, so that the 1PPS time signal and the 1GHz frequency signal with high quality are obtained at the node, then are converted into optical signals through a laser, and are transmitted to the next node with determined route through an optical switch, so that the time-frequency signals are continuously and accurately exchanged and cascaded;
4. 3, the 1GHz frequency signal obtains the noise of a link in a round-trip phase measurement mode, a phase discriminator is used for measuring the phase difference between the 1GHz frequency signal of the node and the 1GHz frequency signal returned by the next node, then an optical fiber delay line is driven to actively compensate phase fluctuation caused by the noise, stable transmission and synchronization of the 1GHz frequency signal are realized, the short-term stability of the transmission of the 1GHz frequency signal between the node 1 and the node 4 obtained by measurement at a certain time is superior to 5E-15@1s, and the long-term stability is superior to 5E-19@10000 s;
5. generating a 100PPS time signal by the 1PPS time signal in the step 3 by adopting spread spectrum, measuring the time delay between the 100PPS time signal of the node and the 100PPS time signal returned by the next node by using a time interval measuring instrument, using the 100 time delay average values as time signal time delay measurement values, and then performing time delay calibration to realize high-precision time synchronization, wherein the 1PPS time signal synchronization accuracy between the node 1 and the node 4 obtained by measurement at a certain time is superior to 70 ps; absolute consistency of time information is achieved through time pulse sequence marking and real-time communication interaction, and the time information synchronization error between the node 1 and the node 4 obtained through measurement at a certain time is controlled within 60 ps.
Claims (7)
1. A method for realizing high-precision time frequency synchronization in an Ethernet communication network is characterized in that the method utilizes wavelength division multiplexing to fuse high-precision time frequency reference signals into Ethernet data; the exchange networking of Ethernet data and continuous time-frequency signals is realized by utilizing the add-drop multiplexing; and realizing the time frequency signal accurate synchronization between the local node and the terminal node by utilizing bidirectional return control.
2. The method for realizing high-precision time-frequency synchronization in Ethernet communication network according to claim 1, comprising the following steps:
1) the reference frequency signal and the reference time signal are modulated onto laser carriers with different wavelengths, and are fused onto a data communication link of the Ethernet through wavelength division multiplexing, so that the reference frequency signal and the reference time signal are transmitted in the same optical fiber with the Ethernet communication data, and after the receiving end carries out wavelength division multiplexing, the time signal, the frequency signal and the communication data are obtained through demodulation;
2) completing route planning selection, network management and control signal uploading and downloading of the communication data obtained in the step 1) at a switching node in a packet mode;
enabling the time signal and the frequency signal obtained in the step 1) to enter the next node in an optical-electrical-optical cascade mode to realize continuous and accurate exchange cascade of the time-frequency signal;
3) the frequency signal in the step 2) obtains the noise of the link by a round-trip phase measurement mode, and then actively compensates the phase fluctuation caused by the noise by a delay line device to realize the transmission and synchronization of the frequency signal;
the time signal in the step 2) adopts a spread spectrum measurement method to realize high-precision time delay measurement of the time pulse signal, then time delay calibration is carried out to realize high-precision time synchronization, and absolute consistency of time information is realized through time pulse sequence marking and real-time communication interaction.
3. The method for realizing high-precision time-frequency synchronization in an ethernet communication network according to claim 1, wherein the reference time signal and the reference frequency signal of step 1) are generated by an atomic clock.
4. The method for realizing high-precision time-frequency synchronization in an ethernet communication network in a converged manner according to claim 1, wherein the time signal and the frequency signal in step 1) are demodulated and recovered by a photodetector, and the communication data are demodulated and recovered by a modem.
5. The method according to claim 1, wherein the delay line device in step 4) is an optical fiber delay line driven by a circuit, and includes two parts, namely a fast-changing delay line and a slow-changing delay line.
6. The method according to claim 1, wherein the spread spectrum measurement method is to spread a 1PPS (pulse per second) time signal into an N PPS time signal, and take an average value of the N delays as a final delay value.
7. The method according to claim 1, wherein the time pulse sequence marker is a second count triggered by the rising edge of the frequency-divided 1PPS time pulse after the system is turned on, and finally forms day-to-picosecond timing information by combining with the measured delay value during transmission.
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