CN112702134A - Bidirectional time synchronization device, system and method - Google Patents
Bidirectional time synchronization device, system and method Download PDFInfo
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Abstract
The invention discloses a bidirectional time synchronization device, a system and a method, belonging to the field of optical fiber time synchronization, and comprising a near end A, an optical fiber link and a far end B; the near end A sends the optical pulse signal and the feedback signal to be multiplexed with the optical signal and the feedback optical signal of the far end B received from the optical fiber link, the optical signal transmitted from the far end B is converted into an electric signal and then sent to the time measuring module, and the control module judges the time difference T between the second pulse signal sent by the far end B and the second pulse signal sent by the near end A according to the random numberAAnd transmitted to the remote B via a fiber optic link. The far end B receives the pulse per second signal and the feedback signal sent by the near end A, and calculates the time difference T between the pulse per second signal sent by the near end A and the pulse per second signal sent by the far end BBUsing two time differences TAAnd TBAnd calculating the clock delay delta T for adjusting the time synchronization of the two clock sources at the two ends. The invention can safely transmit the pulse per second signal and improve the reliability and safety of the system.
Description
Technical Field
The invention belongs to the technical field of optical fiber time synchronization, and particularly relates to a bidirectional time synchronization device, system and method.
Background
With the development of communication technologies such as 5G and 6G, high-speed information transmission is realized, and the enthusiasm of technological revolution in the traditional and emerging fields such as military countermeasure, aerospace, remote control, high-speed traffic, automatic driving, Internet of things, VR and the like drives the wide fusion of multiple fields and multiple subjects, thereby providing wider application prospect and development space. These high precision and high stability time synchronization technologies have increasingly prominent effects in scientific research and national life because the essential condition of low time delay is that an 'absolute' reliable clock reference is required as a reference, and the applications related to the national strategic level, such as comparison and synchronization between atomic clocks, synchronization of long-base-line coherent radio telescopes, particle accelerators, or global positioning systems, rockets, missiles, accurate guidance, phased radar array coordination control, burst secrecy communication, and the like, are not away from high precision time synchronization.
Because satellite time synchronization is easily disturbed and has the disadvantages of low time synchronization precision, the optical fiber has the following advantages in comparison: the method has the advantages of large bandwidth, low loss, small temperature coefficient, low manufacturing cost, high stability, long relay distance and strong anti-interference capability, so that the time synchronization method based on the optical fiber link draws wide attention and obtains a plurality of achievements. The optical fiber time synchronization system is a time synchronization system using optical fiber to perform standard time signal transmission, and since the seventies of the twentieth century, along with the fact that optical fiber is more and more widely used, high-precision time transmission based on optical fiber is receiving more and more attention because of the excellent characteristics of transmission signals and the popularization of optical networks.
The optical fiber time synchronization is a novel high-precision time transmission means, and has the specific advantages of optical fiber transmission signals. The optical fiber time synchronization mainly sends pulse per second, and the pulse per second is fixedly generated and has a certain pulse width. By comparing the pulse per second, the time difference between the two places can be calculated by using a corresponding algorithm, so that the calibration is carried out.
At present, the common time synchronization method based on the optical fiber link mainly includes two modes of a loopback method and a bidirectional time comparison method. The loopback method calculates the time delay of the link by returning the signal sent by the near end through the far end, and performs corresponding time delay to achieve the purpose of time synchronization. The bidirectional comparison method is that the near end and the far end respectively send pulse signals, time intervals between the sent pulses and the received pulses are calculated, the measurement results are subjected to data communication to measure the time difference between the near end and the far end, and the far end adjusts the time delay of the far end according to the time difference to achieve the purpose of time synchronization.
In 2015, Beijing university uses forward digital feedback compensation technology to transmit frequency and time signals simultaneously, and the time synchronization precision after 120km optical fiber transmission is 40 ps. In 2016, the institute of communication, west ampere, uses FPGA to receive pulse-per-second signals in an optical fiber time synchronization system, and simultaneously, internal synchronization generates time codes for transmission, and the final time synchronization precision is 11.8 ns. In 2016, the university of polacrkov AGH technology used a single fiber bi-directional system, which was time compensated by controlling a pair of low noise, precisely matched delay lines, and transmitted for 615km, with a time synchronization accuracy of about 2 ps. In 2019, after 1000km of optical fiber, the time synchronization precision is 5ns and the system stability is 160ps by adopting an FPGA and using a pseudo-random number coding scheme at Beijing post and telecommunications university.
Disclosure of Invention
Based on the above, the invention provides a bidirectional time synchronization device, system and method, which improve the reliability and safety of the optical fiber bidirectional time synchronization system.
The bidirectional time synchronization device comprises a near end A, an optical fiber link and a far end B.
The near end A consists of a first clock source, a first random number module, a first control module, a first light pulse sending module, a first multiplexing module, a first photoelectric detector and a first time measuring module;
the first control module is simultaneously connected with a first clock source, a first random number module, a first time measuring module and a first light pulse sending module. The first clock source generates a pulse-per-second signal and a local clock signal, and the random number generated by the first random digital module is simultaneously provided for the first control module; and the first control module converts the pulse-per-second signal into a pulse-per-second electrical signal and generates a feedback electrical signal according to the random number, and then sends the pulse-per-second electrical signal to the first optical pulse sending module to convert the pulse-per-second electrical signal into an optical signal S.
The first optical pulse sending module is connected with the first photoelectric detector and the optical fiber link through the first multiplexing module, the first photoelectric detector converts an optical signal P of a far end B on the optical fiber link into an electric signal after detection, the electric signal is sent to the first time measuring module, and the first time measuring module calculates the time difference T between second pulse electric signals in the optical signal S and the optical signal PAAnd the signal is transmitted to a far end B through a first control module through an optical fiber link to form a closed loop circuit of a transmitting end.
The far end B consists of a second clock source, a second random number module, a second control module, a second light pulse sending module, a second multiplexing module, a second photoelectric detector and a second time measuring module;
the second control module is simultaneously connected with a second clock source, a second random number module, a second optical pulse sending module and a second time measuring module. The second clock source generates a pulse-per-second signal, the random number generated by the second random digital module is shared with the random number of the first random number module, and the pulse-per-second signal and the shared random number are sent to the second control module;
in the second pulse signal effectiveness of the second clock source, the second control module converts the second pulse signal into a second pulse electrical signal and generates a feedback electrical signal according to the random number, and then sends the second pulse electrical signal to the second optical pulse sending module to convert the second pulse electrical signal into an optical signal P;
the second optical pulse sending module is connected with a second photoelectric detector and the optical fiber link through a second multiplexing module, the second photoelectric detector converts an optical signal S on the optical fiber link into an electric signal after detection, the electric signal is sent to a second time measuring module, and the second time measuring module calculates the time difference T between the second pulse electric signal in the optical signal P and the second pulse electric signal in the optical signal SBTime difference T transmitted in conjunction with the near end AACalculating clock difference delta T by the second control module, and adjusting the time synchronization of the clock signal of the second clock source and the first clock source of the near-end A to formAnd a closed loop circuit at the receiving end.
The specific working principle of the bidirectional time synchronization system is as follows:
for the near end a: in the effective second pulse signal, the first control module determines to convert the second pulse signal into a second pulse electric signal TA1 or generate a feedback electric signal TA2 in sequence at a fixed interval time T1 according to a random number; then, the two signals are converted into an optical signal S through the first optical pulse sending module at the same time, and the first time measuring module is controlled to start timing.
The first multiplexing module transmits the pulse-per-second signal and the feedback signal transmitted by the far end B of the optical fiber link transmission to the first photoelectric detector, the pulse-per-second signal and the feedback signal are converted into a pulse-per-second signal TB1 and a feedback signal TB2, and then the pulse-per-second signal TB1 and the feedback signal TB2 are transmitted to the first time measuring module, and the first time measuring module stops timing;
then, the first time measuring module respectively calculates the time difference T between the second pulse electric signal TA1 sent by the near end A and the second pulse electric signal TB1 sent by the far end BAAnd the time difference between the pulse-per-second signal TA1 and the feedback electric signal TB2, and then the results of the two time differences are sent to the first control module; the first control module selects the time difference T from the time differenceAAnd sending the signal to a far end B through an optical fiber link to form a closed loop circuit of a sending end.
For the far end B: when the pulse per second signal of the second clock source is effective, the second control module determines to convert the pulse per second signal into a pulse per second electrical signal TB1 or generate a feedback electrical signal TB2 at fixed intervals according to the random number; then, the two signals are converted into an optical signal P through a second optical pulse sending module at the same time, and a second time measuring module is controlled to start timing;
the second multiplexing module transmits the pulse-per-second signal and the feedback signal sent by the near end A of the optical fiber link transmission to the second photoelectric detector, the pulse-per-second signal and the feedback signal are converted into a pulse-per-second electric signal TA1 and a feedback electric signal TA2, the second time measurement module stops timing;
the second time measuring module respectively calculates the time difference T between the second pulse electric signal TB1 sent by the far end B and the second pulse electric signal TA1 sent by the near end ABAnd the time difference between the pulse-per-second electrical signal TB1 sent by the far end B and the feedback electrical signal TA2, and then the results of the two time differences are sent to the second control module;
the second control module receives the time difference T transmitted from the near end A through the second multiplexing moduleACombined time difference TBAnd calculating a clock difference delta T, and adjusting a clock signal of a second clock source according to the delta T so as to achieve time synchronization with a first clock source of the near end A and form a closed loop circuit of the receiving end.
The calculation formula of the clock difference Δ T is as follows: Δ T ═ TA-TB)/2+(TAB-TBA)/2+(tA-tB)/2+(rB-rA)/2；
Wherein, TABIs the transmission time, T, from the near end A to the far end BBAIs the time of transmission from the far end B to the near end A, tAIs the transmission delay of the near end A, rBIs the receive delay of the remote B; t is tBIs the transmission delay of the remote B, rAIs the receive delay of the near end a.
After the current adjustment period is finished, the first clock source of the near end a generates the pulse-per-second signal and the local clock signal again, and sends the second pulse signal and the local clock signal to the first control module for adjusting the clock signal of the next period by combining the random number generated by the first random number module.
The bidirectional time synchronization method comprises the following specific steps:
aiming at a near end A, when timing information of a first clock source is effective, a first control module sends a pulse per second signal and a feedback signal to a first optical pulse sending module in sequence;
the sending sequence of the pulse-per-second signal and the feedback signal is determined by the random number of the first random number module;
step two, the second pulse signal and the feedback signal are modulated into an optical signal S by the first optical pulse sending module and sent to the optical fiber link through the first multiplexing module to reach the far end B;
the modulated optical signal S comprises a pulse per second signal and a feedback signal.
Step three, a second multiplexing module of the far end B receives the optical signal S and sends the optical signal S to a second photoelectric detector;
and step four, the second photoelectric detector converts the optical signal S into an electric signal through detection and sends the electric signal to the second time measuring module.
The electric signals comprise a pulse per second electric signal and a feedback electric signal sent by a near end A;
fifthly, the second time measurement module makes a difference between the second pulse electrical signal and the feedback electrical signal sent by the near end A and the second pulse signal sent by the far end B respectively, and sends two difference results to the second control module;
the two difference results refer to: the time difference T between the second pulse electric signal TB1 sent by the far end B and the second pulse electric signal TA1 sent by the near end ABAnd the time difference between the second pulse electrical signal TB1 sent by the far end B and the feedback electrical signal TA 2.
TB＝-ΔT+TAB+tA+rB
Where Δ T is the clock difference between the near end A and the far end B, TABIs the transmission time, t, from the near end A to the far end BAIs the transmission delay of the near end A, rBIs the receive delay of the remote B;
and step six, the second control module provides the random number shared with the first random number module according to the second random number module to judge the sending sequence of the feedback signal and the pulse per second signal.
Step seven, the second optical pulse sending module modulates the pulse per second signal and the feedback signal sent by the second control module into an optical signal P, and the optical signal P is sent to the optical fiber link through the second multiplexing module and reaches the near end A;
the modulated optical signal comprises a pulse-per-second signal and a feedback signal.
And step eight, after the near end A receives the optical signal P sent by the far end B, the optical signal P is sent to the first photoelectric detector through the first multiplexing module to be converted into an electric signal, and the electric signal is sent to the first time measuring module.
The electric signals comprise a pulse per second electric signal and a feedback electric signal sent by a far end B;
step nine, the first time measurement module measures that the converted pulse per second electrical signal and the converted feedback electrical signal are respectively different from the time when the near end A sends the pulse per second electrical signal, and sends the two difference results to the first control module;
the two difference results refer to: the time difference T between the second pulse electric signal TA1 transmitted by the near end A and the second pulse electric signal TB1 transmitted by the far end BAAnd the time difference between the second pulse electrical signal TA1 sent by the near end a and the feedback electrical signal TB 2.
TA＝ΔT+TBA+tB+rA
tBIs the transmission delay of the remote B, rAIs the receive delay of the near end a;
step ten, the near end A measures the time difference TASent to the remote B through the optical fiber link, and the second control module combines the time difference TBCalculating to obtain a clock difference delta T between the near end A and the far end B;
ΔT＝(TA-TB)/2+(TAB-TBA)/2+(tA-tB)/2+(rB-rA)/2
TABand TBAThe two are transmitted on the same optical fiber and are equal.
Step eleven, the far end B adjusts the signal of the second clock source according to the clock delay delta T, and therefore the purpose of synchronizing with the first clock source of the near end A is achieved.
Compared with the prior art, the invention has the following advantages:
(1) a near end A and a far end B use shared random numbers to judge the sending sequence of a pulse per second signal and a feedback signal, and can ensure that the pulse per second signal and the feedback signal are accurately distinguished by the two parties and are not distinguished by a third party.
(2) In signal transmission, when a pulse-per-second signal and a feedback signal are transmitted in an optical fiber channel, physical characteristics such as pulse width, wavelength and the like are consistent, except a near end A and a far end B of two communication parties, other people cannot distinguish the two, and the safety of the system is enhanced.
Drawings
FIG. 1 is a schematic diagram of a bidirectional time synchronizer according to the present invention;
FIG. 2 is a flow chart of a two-way time synchronization method of the present invention;
FIG. 3 is a schematic diagram of a two-way time-synchronized operation of the present invention;
Detailed Description
The present invention will be described in further detail and with reference to the accompanying drawings so that those skilled in the art can understand and practice the invention.
The invention discloses a bidirectional time synchronization device, a system and a method, which add a feedback signal and simultaneously introduce the randomness of random numbers, and specifically comprise the following steps:
the bidirectional time synchronization device, as shown in fig. 1, includes a near end a, a fiber link, and a far end B.
The near end A consists of a first clock source, a first random number module, a first control module, a first light pulse sending module, a first multiplexing module, a first photoelectric detector and a first time measuring module;
the first control module is simultaneously connected with a first clock source, a first random number module, a first time measuring module and a first light pulse sending module. The first clock source generates a pulse-per-second signal and a local clock signal, and the random number generated by the first random digital module is simultaneously provided for the first control module; when the second pulse signal of the first clock source is effective, the first control module converts the second pulse signal into a second pulse electrical signal and simultaneously generates a feedback signal, and the generation sequence of the two signals is determined by a random number;
as shown in fig. 3, T, R of the pulses indicate a transmission pulse and a reception pulse, and the corresponding reference numerals are given below the respective pulses. The first control module converts the pulse-per-second signal into a pulse-per-second electrical signal TA1 according to the random number, and then generates a feedback electrical signal TA2 at a fixed time interval T1; then, the two signals are converted into an optical signal S through the first optical pulse sending module at the same time, and the first time measuring module is controlled to start timing.
Then, sending the second pulse electrical signal and the feedback signal to a first optical pulse sending module to be converted into an optical signal S, and simultaneously controlling a first time measuring module to start timing;
the first random number module is in a classical form or a quantum form;
the second pulse signal is consistent with parameters such as the wavelength and the pulse width of the feedback signal.
The first optical pulse sending module is connected with the first multiplexing module, the first multiplexing module is simultaneously connected with the first photoelectric detector and the optical fiber link, an optical signal S sent by the first optical pulse sending module and an optical signal P received from the optical fiber link are multiplexed on one optical fiber, and the optical signal P from the optical fiber link is transmitted to the first photoelectric detector;
the optical signal P received by the optical fiber link comprises a pulse per second signal and a feedback signal which are sent from a far end B;
the first photoelectric detector converts the optical signal P into an electric signal after detection and sends the electric signal to the first time measuring module, the first time measuring module makes difference between the time when the pulse-per-second electric signal and the feedback electric signal which are converted by the optical signal P arrive and the time when the second pulse signal is sent by the near end A, and sends the two difference results to the first control module;
wherein, the time difference between the time when the near end A sends the pulse per second signal and the time when the near end B receives the pulse per second signal sent by the far end B is TA；
The first control module compares the time difference TAAnd sending the signal to a far end B through an optical fiber link to form a closed loop circuit of a sending end.
The far end B consists of a second clock source, a second random number module, a second control module, a second light pulse sending module, a second multiplexing module, a second photoelectric detector and a second time measuring module;
the second clock source generates a pulse-per-second signal, the random number generated by the second random digital module is shared with the random number of the first random number module, and the pulse-per-second signal and the shared random number are sent to the second control module;
the second control module is simultaneously connected with a second clock source, a second random number module, a second optical pulse sending module and a second time measuring module. When the pulse per second signal of the second clock source is effective, the second control module converts the pulse per second signal into a pulse per second electrical signal and simultaneously generates a feedback signal, and the generation sequence of the two signals is determined by a random number; sending the pulse-per-second electrical signal and the feedback signal to a second optical pulse sending module to be converted into an optical signal P, and simultaneously controlling a second time measuring module to start timing;
the second pulse signal is consistent with parameters such as wavelength, pulse width and the like of the feedback signal.
The second multiplexing module is simultaneously connected with the second optical pulse sending module, the second photoelectric detector and the optical fiber link, multiplexes the optical signal P sent by the second optical pulse sending module and the optical signal S received from the optical fiber link on one optical fiber, and transmits the optical signal S from the optical fiber link to the second photoelectric detector;
the optical signal S received by the optical fiber link comprises a pulse per second signal and a feedback signal which are sent from a near end A;
the second photo detector converts the optical signal S into an electrical signal after detection, and sends the electrical signal to the second time measuring module, and the second time measuring module calculates the time difference T between the pulse-per-second electrical signal TB1 sent by the far end B and the pulse-per-second electrical signal TA1 sent by the near end a, as shown in fig. 3, when the pulse-per-second electrical signal and the feedback electrical signal arrive after the optical signal S is converted by the second time measuring module, respectivelyBAnd the time difference between the pulse-per-second electrical signal TB1 sent by the remote end B and the feedback electrical signal TA2 respectively sends the two timing results to the second control module;
the second random number module provides a random number shared with the first random number module, and the shared random number is realized by quantum key distribution and the like;
the second control module also receives the time difference T sent by the near end A through the second multiplexing moduleADifference value T of combination timeB(ii) a And calculating the clock delay delta T of the first clock source and the second clock source, and adjusting the clock signal of the second clock source according to the clock delay delta T so as to achieve time synchronization with the first clock source of the near end A and form a closed loop circuit of the receiving end.
The second control module needs to control the delay time of the pulse per second signal and also needs to control the delay time of the feedback signal, judges whether the pulse per second signal or the feedback signal is selected according to the shared random number, and then controls different delay times of the pulse per second signal and the feedback signal to form a sending sequence of the pulse per second signal and the feedback signal.
The specific working principle of the bidirectional time synchronization system is as follows:
firstly, when a pulse per second signal is effective, a near end A sends the pulse per second signal and a feedback signal in sequence according to a random number, and sends the pulse per second signal and the feedback signal to a far end B through an optical fiber link after the pulse per second signal is converted into an optical signal S through a first optical pulse sending module;
the near end A receives the pulse per second signal and the feedback signal sent by the far end B, the first photoelectric detector converts the pulse per second signal into an electric signal and sends the electric signal to the first time measuring module, the first time measuring module makes difference between the converted pulse per second signal and the converted feedback electric signal and the time when the near end A sends the pulse per second signal respectively, and sends two difference results to the first control module;
the first control module judges according to the random number: the time difference between the pulse per second signal sent by the far end B and the feedback signal and the time difference between the pulse per second signal sent by the near end A and the pulse per second signal sent by the near end A are respectively obtained through calculation, and the time between the pulse per second signal sent by the near end A and the pulse per second signal sent by the far end B is TA(ii) a Will transmit time TASending the data to a far end B through an optical fiber link;
the first control module judges the sending sequence of the pulse-per-second signal and the feedback signal according to the shared random number.
When the pulse per second signal is effective, the far end B sends the pulse per second signal and the feedback signal in sequence according to the random number, converts the pulse per second signal into an optical signal P through a first optical pulse sending module, and sends the optical signal P to the near end A through an optical fiber link;
the far end B receives the pulse per second signal and the feedback signal sent by the near end A, the second photoelectric detector converts the pulse per second signal into an electric signal and sends the electric signal to the second time measuring module, the second time measuring module makes difference between the pulse per second signal and the feedback electric signal converted by the near end A and the time when the far end B sends the pulse per second signal respectively, and sends two difference results to the second control module;
second oneThe control module judges according to the random number: the time difference between the pulse per second signal and the feedback signal of the near end A and the pulse per second signal sent by the far end B is respectively calculated, and the time T between the pulse per second signal sent by the far end B and the pulse per second signal sent by the near end A is obtainedB；
The second control module receives the time difference T transmitted from the near end A through the second multiplexing moduleAAnd calculating the clock difference delta T between the first clock source and the second clock source, and adjusting according to the clock signal of the second clock source so as to achieve time synchronization with the near-end A.
And the second control module judges the sending sequence of the pulse-per-second signal and the feedback signal according to the shared random number.
The bidirectional time synchronization method comprises the steps that firstly, a near end A sends an optical second pulse signal S to a far end B through an optical fiber link when the time information of a local clock source is effective; receiving a pulse-per-second signal and a feedback signal sent by a far end B, wherein the two signals judge the arrangement sequence of the two signals in a random number mode shared by the two parties, and the pulse-per-second signal and the feedback signal have the same parameters such as wavelength, pulse width and the like; the time T between the start of calculation of the second pulse signal transmitted by the near end A and the reception of the second pulse signal transmitted by the far end B is obtained at the same timeA. Then, the far-end B sends an optical second pulse signal P to the near-end A through the optical fiber link when the time information of the local clock source is effective; receiving a pulse per second signal and a feedback signal sent by a near end A, wherein the two signals judge the arrangement sequence of the two signals in a random number mode shared by the two parties, and the pulse per second signal and the feedback signal have the same parameters such as wavelength, pulse width and the like; the time T between the start of calculation of the second pulse signal sent by the far end B and the reception of the second pulse signal sent by the near end A is calculated at the same timeB. Finally, the near end A will TAData is sent to the remote B, and the remote B sends the data to the remote B according to the time difference TA、TBAnd calculating corresponding time delay delta T by the data, and adjusting the clock signal of the second clock source to achieve time synchronization with the first clock source of the near-end A.
As shown in fig. 2, the specific steps are as follows:
step one, aiming at a near end A, when timing information of a first clock source 1-1 is effective, a first control module 1-3 sends a pulse per second signal and generates a feedback signal to a first optical pulse sending module 1-4;
the sending sequence of the pulse per second signal and the feedback signal is determined by the random number of the first random number module 1-2;
step two, the second pulse signal and the feedback signal sent by the first control module 1-3 are modulated into an optical signal S by the first optical pulse sending module 1-4, and the optical signal S is sent to the optical fiber link through the first multiplexing module 1-5 to reach the far end B;
the modulated optical signal S comprises a pulse per second signal and a feedback signal.
After the far end B receives the optical signal S sent by the near end A, the second multiplexing module 2-5 sends the optical pulse signal to the second photoelectric detector 2-6;
and step four, the second photoelectric detector 2-6 converts the optical signal S into an electric signal through detection, and sends the electric signal to the second time measuring module 2-7.
The electrical signal S includes the pulse-per-second signal and the feedback signal sent from the near end a,
step five, the second time measurement module 2-7 measures the converted pulse per second electrical signal and the feedback electrical signal, makes difference with the time when the far end B sends the pulse per second electrical signal respectively, and sends the two difference results to the second control module 2-3;
the two difference results refer to: the time difference T between the second pulse electric signal TB1 sent by the far end B and the second pulse electric signal TA1 sent by the near end ABAnd the time difference between the second pulse electrical signal TB1 sent by the far end B and the feedback electrical signal TA 2.
TB＝-ΔT+TAB+tA+rB
Where Δ T is the clock difference between the near end A and the far end B, TABIs the transmission time, t, from the near end A to the far end BAIs the transmission delay of the near end A, rBIs the receive delay of the remote B;
step six, the second control module 2-3 judges according to the random number: the sending time of the pulse per second signal and the feedback signal of the near end A is respectively time-different from the sending time of the pulse per second signal sent by the far end B;
the second control module 2-3 judges the sending sequence of the feedback signal and the pulse per second signal according to the random number shared by the first random number module and provided by the second random number module 2-2.
Wherein, the time difference between the time when the far end B transmits the pulse per second signal and the time when the near end A receives the pulse per second signal is TB；
TB＝-ΔT+TAB+tA+rB；
Where Δ T is the clock difference between the near end A and the far end B, TABIs the transmission time, t, from the near end A to the far end BAIs the transmission delay of the near end A, rBIs the receive delay of the remote B;
step seven, the second optical pulse sending module 2-4 modulates the pulse-per-second signal and the feedback signal sent by the second control module 2-3 into an optical signal P, and sends the optical signal P to the optical fiber link through the second multiplexing module 2-5 to reach the near end A;
the modulated optical signal P comprises a pulse per second signal and a feedback signal.
Step eight, after the near end A receives the optical signal P sent by the far end B, the optical signal is sent to the first photoelectric detector 1-6 through the first multiplexing module 1-5, the optical signal is converted into an electric signal through detection, and the electric signal is sent to the first time measuring module 1-7.
The electric signal comprises a pulse per second signal and a feedback signal sent by a far end B;
step ten, the first time measuring module 1-7 measures the converted pulse per second electrical signal and the feedback electrical signal to respectively make a difference with the time when the near end A sends the pulse per second electrical signal, and sends the two difference results to the first control module 1-3;
the first control module 1-3 judges according to the random number: the time of the pulse per second signal and the feedback signal sent by the far end B is respectively different from the time of the pulse per second signal sent by the near end A, and the time difference between the pulse per second signal sent by the near end A and the pulse per second signal sent by the far end B is calculated to be TA；
TA＝ΔT+TBA+tB+rA
Where Δ T is the clock difference between the near end A and the far end B, TBAIs the time of transmission from the far end B to the near end A, tBIs the transmission delay of the remote B, rAIs the receive delay of the near end a;
step eleven, the near end A measures the time difference TASending the data to a far end B through an optical fiber link, and receiving T by the far end BACalculating to obtain the clock difference delta T between the near end A and the far end B;
ΔT＝(TA-TB)/2+(TAB-TBA)/2+(tA-tB)/2+(rB-rA)/2
step eleven, the far-end B adjusts the time delay of the clock signal of the second clock source to be delta T, and therefore clock synchronization with the first clock source of the near-end A is achieved.
Claims (6)
1. A bidirectional time synchronization device is characterized by comprising a near end A, an optical fiber link and a far end B;
the near end A consists of a first clock source, a first random number module, a first control module, a first light pulse sending module, a first multiplexing module, a first photoelectric detector and a first time measuring module;
the first control module is simultaneously connected with a first clock source, a first random number module, a first time measuring module and a first light pulse sending module; the first control module converts the pulse-per-second signal generated by the first clock source into a pulse-per-second electrical signal, generates a feedback electrical signal, and transmits the feedback electrical signal to the first optical pulse transmitting module to convert the feedback electrical signal into an optical signal S;
the first optical pulse sending module is connected with the first photoelectric detector and the optical fiber link through the first multiplexing module, the first photoelectric detector converts an optical signal P of a far end B on the optical fiber link into an electric signal after detection, the electric signal is sent to the first time measuring module, and the first time measuring module calculates the time difference T between second pulse electric signals in the optical signal S and the optical signal PAThe signal is transmitted to a far end B through a first control module through an optical fiber link to form a closed loop circuit of a transmitting end;
the far end B consists of a second clock source, a second random number module, a second control module, a second light pulse sending module, a second multiplexing module, a second photoelectric detector and a second time measuring module;
the second control module is simultaneously connected with a second clock source, a second random number module, a second optical pulse sending module and a second time measuring module; the second control module converts the pulse-per-second signal generated by the second clock source into a pulse-per-second signal, generates a feedback signal, and transmits the feedback signal to the second optical pulse transmitting module to convert the feedback signal into an optical signal P;
the second optical pulse sending module is connected with a second photoelectric detector and the optical fiber link through a second multiplexing module, the second photoelectric detector converts an optical signal S on the optical fiber link into an electric signal after detection, the electric signal is sent to a second time measuring module, and the second time measuring module calculates the time difference T between the second pulse electric signal in the optical signal P and the second pulse electric signal in the optical signal SBTime difference T transmitted in conjunction with the near end AAAnd calculating a clock difference delta T through the second control module, and adjusting the time synchronization of the clock signal of the second clock source and the first clock source of the near end A to form a closed loop circuit of the receiving end.
2. The bi-directional time synchronizer as claimed in claim 1, wherein said first control module is required to control the delay time of the pulse per second signal and also to control the delay time of the feedback signal, and determines whether the pulse per second signal or the feedback signal is selected according to the shared random number, and then controls the different delay times of the pulse per second signal and the feedback signal to form the transmission sequence of the pulse per second signal and the feedback signal.
3. A two-way time synchronizer according to claim 1, wherein the random number generated by said second random number module is shared with the random number of said first random number module.
4. A bidirectional time synchronizer as recited in claim 1 wherein said first multiplexing module multiplexes the optical signal transmitted by the first optical pulse transmitting module with the optical signal received from the optical fiber link onto an optical fiber and transmits the optical signal from the optical fiber link to the first photodetector.
5. The two-way time synchronization system using the two-way time synchronization device according to claim 1, wherein the specific operation principle is as follows:
for the near end a: in the effective second pulse signal, the first control module determines to convert the second pulse signal into a second pulse electric signal TA1 or generate a feedback electric signal TA2 at fixed intervals according to the random number; then, the two signals are converted into an optical signal S through a first optical pulse sending module at the same time, and a first time measuring module is controlled to start timing;
the first multiplexing module transmits the pulse-per-second signal and the feedback signal transmitted by the far end B of the optical fiber link transmission to the first photoelectric detector, the pulse-per-second signal and the feedback signal are converted into a pulse-per-second signal TB1 and a feedback signal TB2, and then the pulse-per-second signal TB1 and the feedback signal TB2 are transmitted to the first time measuring module, and the first time measuring module stops timing;
then, the first time measuring module respectively calculates the time difference T between the second pulse electric signal TA1 sent by the near end A and the second pulse electric signal TB1 sent by the far end BAAnd the time difference between the pulse-per-second signal TA1 and the feedback electric signal TB2, and then the results of the two time differences are sent to the first control module; the first control module selects the time difference T from the time differenceAThe signal is sent to a far end B through an optical fiber link to form a closed loop circuit of a sending end;
for the far end B: when the pulse per second signal of the second clock source is effective, the second control module determines to convert the pulse per second signal into a pulse per second electrical signal TB1 or generate a feedback electrical signal TB2 at fixed intervals according to the random number; then, the two signals are converted into an optical signal P through a second optical pulse sending module at the same time, and a second time measuring module is controlled to start timing;
the second multiplexing module transmits the pulse-per-second signal and the feedback signal sent by the near end A of the optical fiber link transmission to the second photoelectric detector, the pulse-per-second signal and the feedback signal are converted into a pulse-per-second electric signal TA1 and a feedback electric signal TA2, the second time measurement module stops timing;
the second time measuring module respectively calculates the time difference T between the second pulse electric signal TB1 sent by the far end B and the second pulse electric signal TA1 sent by the near end ABAnd the time difference between the pulse-per-second electrical signal TB1 sent by the far end B and the feedback electrical signal TA2, and then the results of the two time differences are sent to the second control module;
the second control module receives the time difference T transmitted from the near end A through the second multiplexing moduleACombined time difference TBCalculating a clock difference delta T, and adjusting a clock signal of a second clock source according to the delta T so as to achieve time synchronization with a first clock source at a near end A and form a closed loop circuit at a receiving end;
the calculation formula of the clock difference Δ T is as follows: Δ T ═ TA-TB)/2+(TAB-TBA)/2+(tA-tB)/2+(rB-rA)/2；
Wherein, TABIs the transmission time, T, from the near end A to the far end BBAIs the time of transmission from the far end B to the near end A, tAIs the transmission delay of the near end A, rBIs the receive delay of the remote B; t is tBIs the transmission delay of the remote B, rAIs the receive delay of the near end a;
after the current adjustment period is finished, the first clock source of the near end a generates the pulse-per-second signal and the local clock signal again, and sends the second pulse signal and the local clock signal to the first control module for adjusting the clock signal of the next period by combining the random number generated by the first random number module.
6. The bidirectional time synchronization method using the bidirectional time synchronization device according to claim 1, comprising the following steps:
aiming at a near end A, when timing information of a first clock source is effective, a first control module sends a pulse per second signal and a feedback signal to a first optical pulse sending module in sequence;
step two, the second pulse signal and the feedback signal are modulated into an optical signal S by the first optical pulse sending module and sent to the optical fiber link through the first multiplexing module to reach the far end B;
step three, a second multiplexing module of the far end B receives the optical signal S and sends the optical signal S to a second photoelectric detector;
step four, the second photoelectric detector converts the optical signal S into an electric signal through detection and sends the electric signal to a second time measuring module;
fifthly, the second time measurement module makes a difference between the second pulse electrical signal and the feedback electrical signal sent by the near end A and the second pulse signal sent by the far end B respectively, and sends two difference results to the second control module;
the two difference results refer to: the time difference T between the second pulse electric signal TB1 sent by the far end B and the second pulse electric signal TA1 sent by the near end ABAnd the time difference between the second pulse electrical signal TB1 sent by the far end B and the feedback electrical signal TA 2;
TB＝-ΔT+TAB+tA+rB
where Δ T is the clock difference between the near end A and the far end B, TABIs the transmission time, t, from the near end A to the far end BAIs the transmission delay of the near end A, rBIs the receive delay of the remote B;
the second control module provides a random number shared with the first random number module according to the second random number module to judge the sending sequence of the feedback signal and the pulse per second signal;
step seven, the second optical pulse sending module modulates the pulse per second signal and the feedback signal sent by the second control module into an optical signal P, and the optical signal P is sent to the optical fiber link through the second multiplexing module and reaches the near end A;
step eight, after receiving the optical signal P sent by the far end B, the near end A sends the optical signal P to a first photoelectric detector through a first multiplexing module to be converted into an electric signal and sends the electric signal to a first time measuring module;
step nine, the first time measurement module measures that the converted pulse per second electrical signal and the converted feedback electrical signal are respectively different from the time when the near end A sends the pulse per second electrical signal, and sends the two difference results to the first control module;
the two difference results refer to: the time difference T between the second pulse electric signal TA1 transmitted by the near end A and the second pulse electric signal TB1 transmitted by the far end BAAnd nearTime difference between the pulse-per-second electric signal TA1 sent by the terminal A and the feedback electric signal TB 2;
TA＝ΔT+TBA+tB+rA
tBis the transmission delay of the remote B, rAIs the receive delay of the near end a;
step ten, the near end A measures the time difference TASent to the remote B through the optical fiber link, and the second control module combines the time difference TBCalculating to obtain a clock difference delta T between the near end A and the far end B;
ΔT＝(TA-TB)/2+(TAB-TBA)/2+(tA-tB)/2+(rB-rA)/2
TABand TBAThe transmission is carried out on the same optical fiber, and the transmission are equal;
step eleven, the far end B adjusts the signal of the second clock source according to the clock delay delta T, and therefore the purpose of synchronizing with the first clock source of the near end A is achieved.
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