CN103812593B - High precision distribution type fiber-optic clock synchronization system - Google Patents
High precision distribution type fiber-optic clock synchronization system Download PDFInfo
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- CN103812593B CN103812593B CN201410060009.1A CN201410060009A CN103812593B CN 103812593 B CN103812593 B CN 103812593B CN 201410060009 A CN201410060009 A CN 201410060009A CN 103812593 B CN103812593 B CN 103812593B
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Abstract
The present invention discloses a kind of high precision distribution type fiber-optic clock synchronization system, comprise: the synchronous center of optical fiber time, passive optical distribution network and the synchronous unit of multiple optical fiber time, described optical fiber time is synchronously centrally located at the conjunction terminal of passive optical distribution network, and the described synchronous unit of each optical fiber time lays respectively at each point of terminal of passive optical distribution network. The present invention realizes connection and the connection control of point-to-multipoint with passive optical distribution network and time division multiple access access technology, utilizes two-way Time transfer receiver method to realize the split-second precision comparison between point and point, thus realizes the distributed time lock of high precision.
Description
Technical field
The present invention relates to optical fiber time-frequency transmission technology neck system, specifically a kind of two-way Time transfer receiver system of high precision distribution type fiber-optic.
Background technology
The Time synchronization technique of high precision has important using value in satellite-navigation, aerospace, survey of deep space, geological mapping, communication, power transmission and the field such as scientific research and metering. At present tradition precise synchronization technology mainly contains that GPS looks altogether, satellite dual-time is than equity. It is relatively simple that GPS looks the equipment needed for method altogether, and cost is low, but precision is difficult to reach nanosecond order. Two Way Satellite Time Transfer is to the time lock that can realize high precision, it is possible to reach magnitude of subnanosecond, but needs to utilize specific satellite communication link. Owing to the stability of freeboard link is not good, being easily interfered, its precision is difficult to improve further, and there is the problem such as security and apparatus expensive.
Optical fibre channel has higher than freeboard path stability (particularly within the short period of time on yardstick), loss is low, be affected by the external environment little, bandwidth advantages of higher. The 80's of last century just cause the concern of investigator. Along with the fast development of opticfiber communication, optical-fiber network technology, and to the raising that time lock precision etc. requires, cause the concern of more and more investigators based on the time lock of optical fiber, achieve sizable progress, and obtained certain applications.
At present, two kinds of methods utilizing optical fiber to carry out time lock are mainly contained. One is based on optical fiber synchronous digital hierarchy (SDH:SynchronousDigitalHierarchy) link and equipment, by inserting time information realization time lock in the gap when SDH. The method can directly utilize traditional SDH equipment, but the uncertainty due to pointer regulation in the asymmetry of physics link and SDH equipment, the synchronization accuracy of report is in tens nanoseconds at present. Another kind of optical fiber time synchronous method is that direct full light passage and special time synchronism equipment based on bottom carries out two-way Time transfer receiver. The method can effectively ensure that the symmetry of physics link, and existing synchronization accuracy is better than the Experimental report of 1 nanosecond.
The synchronous scheme of optical fiber time of existing document report is substantially all point-to-point. In a lot of practical application, as the synchronous of the interior multiple equipment in station is located in navigation, it is necessary to the distributed high-accuracy time lock of point-to-multipoint. Have employed a kind of based on the distributed time lock scheme of electrical distributor and point-to-point optical fiber link in Technology of American Deep Space Network. But electrical distributor needs the process of the conversion of light/electrical/optical and electricity, and is active equipment, not only can introduce extra unstable, and safeguard, difficult management.
Summary of the invention
It is an object of the invention to overcome above-mentioned the deficiencies in the prior art, it is provided that a kind of two-way clock synchronization system of high precision distribution type fiber-optic, it is achieved the synchronous unit of multiple optical fiber time, to the timesharing multiplexing of uplink, avoids data conflict.
The technical solution of the present invention is as follows:
A kind of high precision distribution type fiber-optic clock synchronization system, its feature is, comprise: the synchronous center of optical fiber time, passive optical distribution network and the synchronous unit of multiple optical fiber time, described optical fiber time is synchronously centrally located at the conjunction terminal of passive optical distribution network, and the described synchronous unit of each optical fiber time lays respectively at each point of terminal of passive optical distribution network.
The synchronous center of described optical fiber time comprises: center control and processing module, center time coding/decoding module, center timed interval test module, center light transceiver module and timer;
Described center control and processing module, for control center's time coding/decoding module, center timed interval test module, center light transceiver module and timer, complete the point-to-multipoint control of time division multiple access, the two-way Time transfer receiver control of timesharing, the monitoring of system state and maintenance.
Described center time coding/decoding module, center control and the processing module period coding/decoding module at the synchronous center of optical fiber time, for the Code And Decode of deadline code, encoding function exports to optical transceiver module by being encoded in downgoing time synchronous code from the timing wave (such as 1pps, 10pps etc.) of center time-frequency standard and the address of time information, control information, two-way pumping station test result and the current synchronous unit of optical fiber time; Decoding function decodes the address of corresponding timing wave, time information and the synchronous unit of optical fiber time from the time code from the synchronous unit of optical fiber time, timing wave is passed to timed interval test module, the address of synchronous for optical fiber time unit and time information are passed to center control and processing module.
Described center timed interval test module, the center control at the synchronous center of optical fiber time and processing module period interval test module, the time difference between the timing wave exported for test center's time coding/decoding module and center time-frequency standard timing signal;
Described center light transceiver module, the center control at the synchronous center of optical fiber time and the working order of processing module control optical transceiver module, for by the optical signal switching electrical signals from uplink fiber path, and after reverting to time code, pass to center time coding/decoding module; And be modulated to the time code that center time coding/decoding module exports along downlink fiber path on optical signal, and it is sent to the synchronous unit of optical fiber time through passive optical distribution network;
Described timer, the center control at the synchronous center of optical fiber time and the switch of processing module control timer, control to reach the moment at the synchronous center of optical fiber time with the processing module record synchronous unit of each optical fiber time for completing the center at the synchronous center of optical fiber time.
Described passive distribution optical-fiber network comprises passive light branching unit, optical fiber and bi-directional light amplifier.
The synchronous unit of described optical fiber time comprises: time coding/decoding module, optical transceiver module, control and processing module, timed interval test module, photoswitch and timing information adjusting module;
Described control and processing module, period coding/decoding module, timed interval test module, optical transceiver module photoswitch and timing information adjustment unit, for completing the connection control at center synchronous with optical fiber time, the two-way Time transfer receiver of timesharing controls and clock correction calculates.
Described time coding/decoding module, the control of the synchronous unit of optical fiber time and processing module period coding/decoding module, for the coding and decoding function of deadline code. Address coding from the timing wave of local user clock, time information, the synchronous unit of this optical fiber time is exported to optical transceiver module by encoding function; Decoding function decodes corresponding timing wave, time information, the address of the current synchronous unit of optical fiber time and the delay inequality etc. of optical fiber time synchronous center test from the time code from the synchronous center of optical fiber time;
Described timed interval test module, control and processing module period interval test module, the time difference between the timing wave of the timing wave exported for test duration coding/decoding module and local time-frequency standard output.
Described optical transceiver module, control and processing module control optical transceiver module working order, for by the optical signal switching electrical signals from downlink fiber path, the time code of reverting to passes to time coding/decoding module; And be modulated on optical signal by time code along uplink fiber path to send;
Described optical switch module, control controls the break-make of photoswitch with processing module, for the on-off control of upper row data.
Described timing information adjusting module, control and processing module control timing information adjusting module, for the adjustment of this locality timing information, prevent uplink transmission time code from conflicting in a link.
Compared with prior art, the useful effect of the present invention is as follows:
(1) adopt passive optical network structure, it is easy to management and safeguards;
(2) asymmetry of transmission link is overcome;
(3) distributed network does not need the process of light/electrical/optical conversion and electricity, adopts Passive Optical Components, extra unstable can not be introduced.
Accompanying drawing explanation
Fig. 1 is the structural representation of the embodiment of the two-way clock synchronization system of high precision distribution type fiber-optic of the present invention;
Fig. 2 is the working process schematic diagram of the two-way clock synchronization system embodiment of high precision distribution type fiber-optic of the present invention.
Embodiment
Specific embodiment of the present invention is provided below in conjunction with accompanying drawing. The present embodiment is implemented premised on the technical scheme of the present invention, give detailed enforcement mode and and concrete workflow, but protection scope of the present invention is not limited to following embodiment.
Fig. 1 is the structural representation of the embodiment of the two-way clock synchronization system of high precision distribution type fiber-optic of the present invention, and as shown in the figure, wherein, optical branching device and optical fiber form the passive optical distribution network 2 of a 1 �� N. The synchronous center 1 of optical fiber time is positioned at the conjunction terminal of passive optical distribution network 2. The synchronous unit 3 of N number of optical fiber time lays respectively at N number of point of terminal of passive optical distribution network 2. System completes distributed bidirectional Time transfer receiver under the control at the synchronous center 1 of optical fiber time. Specifically comprise:
A kind of high precision distribution type fiber-optic clock synchronization system, comprise: the synchronous unit 3 of the synchronous center of optical fiber time 1, passive optical distribution network 2 and multiple optical fiber time, described optical fiber time is synchronously centrally located at the conjunction terminal of passive optical distribution network, and the described synchronous unit of each optical fiber time lays respectively at each point of terminal of passive optical distribution network.
The synchronous center 1 of described optical fiber time comprises: center control and processing module 1-1, center time coding/decoding module 1-2, the test of the center timed interval module 1-3, center light transceiver module 1-4 and timer 1-5;
Described center control and processing module, for control center's time coding/decoding module, center timed interval test module, center light transceiver module and timer, complete the point-to-multipoint control of time division multiple access, the two-way Time transfer receiver control of timesharing, the monitoring of system state and maintenance;
Described center time coding/decoding module, for the Code And Decode of deadline code,
Described coding refers to and is encoded to from the timing wave of center time-frequency standard and the address of time information, control information, two-way pumping station test result and the current synchronous unit of optical fiber time in downgoing time synchronous code, and exports to center light transceiver module;
Described decoding refers to the address decoding corresponding timing wave, time information and the synchronous unit of optical fiber time from the time code from the synchronous unit of optical fiber time, and timing wave is transferred to center timed interval test module, the address of synchronous for optical fiber time unit and time information are transferred to center control and processing module;
Described center timed interval test module, the time difference between the timing wave exported for measuring fiber time lock center time coding/decoding module and center time-frequency standard timing signal;
Described center light transceiver module, for by the optical signal switching electrical signals from uplink fiber path, and passes to center time coding/decoding module after reverting to time code; And be modulated to the time code that center time coding/decoding module exports along downlink fiber path on optical signal, and it is sent to the synchronous unit of optical fiber time through passive optical distribution network;
Described timer, controls to reach the moment at the synchronous center of optical fiber time with the processing module record synchronous unit of each optical fiber time for completing the center at the synchronous center of optical fiber time.
Described passive distribution optical-fiber network 2 comprises passive light branching unit 2-1, optical fiber and bi-directional light amplifier 2-2.
The synchronous unit 3 of described optical fiber time comprises: time coding/decoding module 3-3, optical transceiver module 3-2, control and processing module 3-5, timed interval test module 3-4, photoswitch 3-1 and timing information adjusting module 3-6;
Described control and processing module, time coding/decoding module, timed interval test module, optical transceiver module, photoswitch and timing information adjusting module, for completing the connection control at center synchronous with optical fiber time, the two-way Time transfer receiver of timesharing controls and clock correction calculates;
Described time coding/decoding module, for the Code And Decode of deadline code;
Described coding refers to and goes out to optical transceiver module by the address coding transmission from the timing wave of local user clock, time information, the synchronous unit of this optical fiber time;
Described decoding refers to and decodes corresponding timing wave, time information, the address of the current synchronous unit of optical fiber time and the delay inequality of optical fiber time synchronous center test from the time code from the synchronous center of optical fiber time;
Described timed interval test module, the time difference between the timing wave of the timing wave exported for test duration coding/decoding module and local time-frequency standard output;
Described optical transceiver module, for by the optical signal switching electrical signals from downlink fiber path, the time code of reverting to passes to time coding/decoding module; And be modulated on optical signal by time code along uplink fiber path to send;
Described optical switch module, for the on-off control of upper row data.
Described timing information adjustment, for the adjustment of this locality timing information, prevents uplink transmission time code from conflicting in a link.
Specific implementation process is as follows:
When center control and processing module 1-1 are when receiving after time lock instruction, entering the presynchronization stage: first synchronous unit of optical fiber time 3 is set to the synchronous unit of current optical fiber time, enable center time coding/decoding module 1-2 also sends the address of synchronous for current optical fiber time unit to center time coding/decoding module 1-2. Center time coding/decoding module 1-2 encodes the connection request producing to comprise the synchronous unit address of current optical fiber time, and when local timing signal being detected, by center light transceiver module 1-4, connection request is sent to passive optical distribution network 2, and center control starts timer 1-5 with processing module 1-1.
The connection request received is reverted to electrical signal and passes to time coding/decoding module 3-3 by the optical transceiver module 3-2 of the synchronous unit 3 of optical fiber time. Time coding/decoding module 3-3 from connection request time code extracts the address of the synchronous unit of current optical fiber time, and it is transferred to control and processing module 3-5. Control to be compared address encoded to the address of the synchronous unit of current optical fiber time obtained and the synchronous unit of this optical fiber time from processing module 3-5: if the address of the address of the current synchronous unit of optical fiber time and the synchronous unit of this optical fiber time is different, then control and processing module 3-5 continue to monitor. If the address of the address unit synchronous with this optical fiber time of the current synchronous unit of optical fiber time is identical, the transmitting then controlling to open photoswitch 3-1 with processing module 3-5 is enable, simultaneously, coding of enable time coding/decoding module 3-3 produces to connect and confirms, and when controlling local timing signal to be detected with processing module 3-5, through optical transceiver module 3-2 by passive optical distribution network 2 by connecting the center light transceiver module 1-4 confirming to be sent to the synchronous center 1 of optical fiber time, send the transmission closing photoswitch 3-1 after connecting confirmation enable. Connect and confirm to arrive center control and processing module 1-1 through center light transceiver module 1-4 and center time coding/decoding module 1-2 successively. Center controls and the connection of processing module 1-1 confirmation synchronous unit with current optical fiber time, the time t ' at optical fiber time synchronous revenue centre control center synchronous with processing module 1-1 record connection acknowledgement signal arrival optical fiber time before timer 1-5 expires1, and reset timer 1-5. Then the synchronous center of optical fiber time 1 continues to send connection request to the next synchronous unit of optical fiber time, and same record connects the time t ' that acknowledgement signal arrives the synchronous center of optical fiber time2Then continue to send connection request to the next synchronous unit of optical fiber time, until the synchronous center of optical fiber time 1 is after the connection request and confirmation of unit synchronous with each optical fiber time successively, center controls with processing module 1-1 according to the time t ' at the connection acknowledgement signal arrival synchronous center of optical fiber time of the synchronous unit of each optical fiber timei, check t 'iWhether it is greater than 1, if t 'iIt is greater than 1, then ti=t 'i-1; Otherwise, ti=t 'i. Center control detects t with processing module 1-1iRelation each other, if detection tiRelation each other does not meet | tj-ti| >=�� t, i, j=1,2 ..., N and i �� j, the control of optical fiber time synchronous center press optical fiber time synchronous unit numbering order from big to small and is calculated the adjustment amount needing the adjustment regularly synchronous unit of information optical fiber time regularly information with processing module 1-1, and the adjustment amount of corresponding timing information is �� ti=ti+(��t-|tj-ti|). The control of optical fiber time synchronous center and processing module 1-1 after calculating and needing the synchronous unit timing information adjustment amount of the optical fiber time of adjustment local timing information, enable center time coding/decoding module 1-2 also will need the address of the adjustment timing synchronous unit of information optical fiber time and corresponding optical fiber time lock unit regularly information adjustment amount send center time coding/decoding module 1-2 to. Center time coding/decoding module 1-2 encodes and produces to comprise address and the corresponding optical fiber time lock unit timing information adjustment amount that needs adjust the timing synchronous unit of information optical fiber time, and when local timing signal being detected, by optical transceiver module 1-4, connection request is sent to passive optical distribution network 2. The synchronous unit of optical fiber time receive adjustment request after, according to the adjustment amount �� t receivediBy the timing information that the adjustment of timing information adjusting module is local. After the timing information adjustment of the synchronous unit of all optical fiber times is complete, enter the two-way Time transfer receiver stage.
In the two-way Time transfer receiver stage, center time coding/decoding module 1-2 at the synchronous center 1 of optical fiber time produces the time code comprising time-frequency standard timing signal, time information and two-way pumping station test result, and each the local timing signal start time after receiving connection confirmation is sent to the synchronous unit of current optical fiber time; Simultaneously, when timing information is effective, optical fiber time lock unit i controls to open photoswitch with processing module, the time coding/decoding module of the synchronous unit i of optical fiber time produces the time code comprising user clock timing wave and time information, is sent to the synchronous center 1 of optical fiber time. The synchronous center of optical fiber time 1 and the synchronous unit i of optical fiber time are after receiving the time code of the other side, from time code, extract timing wave and time information by respective time coding/decoding module, and test, by the respective timed interval, the delay inequality that module testing goes out timing wave and the local clock timing signal separately extracted. The delay inequality that optical fiber time synchronous center 1 timed interval test module 1-3 records is coded in downgoing time synchronous code through time coding/decoding module 1-2 to be sent to the synchronous unit i of corresponding optical fiber time. Optical fiber time synchronous unit i utilize the local delay inequality surveyed and and from the synchronous receive centre of optical fiber time to delay inequality calculate clock correction, and the clock correction of calculating and the timing wave that recovers are exported to local user clock, make it central synchronous synchronous with optical fiber time.
The Small frequency offset that exists due to two places clock, the dynamic change of transmission route time delay etc., in the two-way Time transfer receiver stage, it may be necessary to the timing information of the synchronous unit i of each optical fiber time adjusted, to avoid the conflict of adjacent node. The control of optical fiber time synchronous center calculates ATA actual time of arrival t ' receive the time code arrival synchronous center of optical fiber time of the synchronous unit of each optical fiber time with processing module 1-1 afterAWith t predetermined time of arrivalADifference DELTA tA=t 'A-tA, and this difference is coded in descending time code, it is broadcast to the synchronous unit of all optical fiber times, after corresponding optical fiber time lock unit receives descending time code, extracts difference, the timing information that adjustment is local
When receiving termination instruction or comparison reaches precision, enter comparison ending phase, complete comparison end operation; Otherwise, proceed two-way Time transfer receiver.
Claims (3)
1. a high precision distribution type fiber-optic clock synchronization system, it is characterized in that, comprise: the synchronous center of optical fiber time, passive optical distribution network and the synchronous unit of multiple optical fiber time, described optical fiber time is synchronously centrally located at the conjunction terminal of passive optical distribution network, and the described synchronous unit of each optical fiber time lays respectively at each point of terminal of passive optical distribution network;
The synchronous center of described optical fiber time comprises: center control and processing module, center time coding/decoding module, center timed interval test module, center light transceiver module and timer;
Described center control and processing module, for control center's time coding/decoding module, center timed interval test module, center light transceiver module and timer, complete the point-to-multipoint control of time division multiple access, the two-way Time transfer receiver control of timesharing, the monitoring of system state and maintenance;
Described center time coding/decoding module, for the Code And Decode of deadline code,
Described coding refers to and is encoded to from the timing wave of center time-frequency standard and the address of time information, control information, two-way pumping station test result and the current synchronous unit of optical fiber time in downgoing time synchronous code, and exports to center light transceiver module;
Described decoding refers to the address decoding corresponding timing wave, time information and the synchronous unit of optical fiber time from the time code from the synchronous unit of optical fiber time, and timing wave is transferred to center timed interval test module, the address of synchronous for optical fiber time unit and time information are transferred to center control and processing module;
Described center timed interval test module, the time difference between the timing wave exported for measuring fiber time lock center time coding/decoding module and center time-frequency standard timing signal;
Described center light transceiver module, for by the optical signal switching electrical signals from uplink fiber path, and passes to center time coding/decoding module after reverting to time code; And be modulated to the time code that center time coding/decoding module exports along downlink fiber path on optical signal, and it is sent to the synchronous unit of optical fiber time through passive optical distribution network;
Described timer, controls to reach the moment at the synchronous center of optical fiber time with the processing module record synchronous unit of each optical fiber time for completing the center at the synchronous center of optical fiber time.
2. high precision distribution type fiber-optic clock synchronization system according to claim 1, it is characterised in that, described passive distribution optical-fiber network comprises passive light branching unit, optical fiber and bi-directional light amplifier.
3. high precision distribution type fiber-optic clock synchronization system according to claim 1, it is characterized in that, the synchronous unit of described optical fiber time comprises: time coding/decoding module, optical transceiver module, control and processing module, timed interval test module, photoswitch and timing information adjusting module;
Described control and processing module, period coding/decoding module, timed interval test module, optical transceiver module, photoswitch and timing information adjusting module, for completing the connection control at center synchronous with optical fiber time, the two-way Time transfer receiver of timesharing controls and clock correction calculates;
Described time coding/decoding module, for the Code And Decode of deadline code;
Described coding refers to and goes out to optical transceiver module by the address coding transmission from the timing wave of local user clock, time information, the synchronous unit of this optical fiber time;
Described decoding refers to and decodes corresponding timing wave, time information, the address of the current synchronous unit of optical fiber time and the time difference of optical fiber time synchronous center test from the time code from the synchronous center of optical fiber time;
Described timed interval test module, the time difference between the timing wave of the timing wave exported for test duration coding/decoding module and local time-frequency standard output;
Described optical transceiver module, for by the optical signal switching electrical signals from downlink fiber path, the time code of reverting to passes to time coding/decoding module; And be modulated on optical signal by time code along uplink fiber path to send;
Described optical switch module, for the on-off control of upper row data;
Described timing information adjusting module, for the adjustment of this locality timing information, prevents uplink transmission time code from conflicting in a link.
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| CN104168077B (en) * | 2014-07-04 | 2017-02-08 | 上海交通大学 | High accuracy optical fiber bidirectional time comparison method and system |
| CN105790845B (en) * | 2016-04-08 | 2017-12-26 | 上海交通大学 | Single fiber bi-directional time division multiplexing optical amplification device |
| CN106209295B (en) * | 2016-07-20 | 2018-09-14 | 上海交通大学 | The control method of two-way time division multiplexing Time Transmission system |
| CN106788840B (en) * | 2016-11-30 | 2018-06-05 | 中国科学院国家授时中心 | A kind of high-precision optical fiber method for synchronizing time based on optical fiber Frequency Transfer |
| CN109921872B (en) * | 2018-11-29 | 2020-11-10 | 上海交通大学 | Optical fiber time transmission system and transmission method |
| CN109981211B (en) * | 2019-03-21 | 2020-02-07 | 上海交通大学 | Distributed optical fiber time frequency joint transmission system and transmission method |
| CN111770396B (en) * | 2020-06-04 | 2022-02-11 | 中国人民解放军国防科技大学 | Signal generating and comparing device and method based on optical fiber transmission |
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