CN103576542B - The high precision time dissemination system of the ground Big Dipper is used for based on ground fiber optic network - Google Patents
The high precision time dissemination system of the ground Big Dipper is used for based on ground fiber optic network Download PDFInfo
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Abstract
Easily be disturbed for what solve that the satellite-based high precision time dissemination system of prior art exists, be subject to weather or climatic influences and the problems such as signal can only be adopted in place in the open, the present invention proposes a kind of ground Big Dipper high precision time dissemination system based on ground fiber optic network, comprise setting zero level, one-level, secondary and three grades totally four level optical networkings, adopt level calibration mechanism to keep the clock synchronous of each level optical networking, adopt single fiber bi-directional calibration steps to realize the clock synchronous of each level optical networking.The Advantageous Effects that the present invention is based on the ground Big Dipper high precision time dissemination system of ground fiber optic network to form the ground time dissemination system with space-based time dissemination system (such as GPS/GLONASS/ Beidou satellite navigation system) for subsequent use, mutual support each other, and there is the strong and survivability high of with low cost, antijamming capability, for the military-civil communication and navigation of China and positioning system provide the most basic time service service.
Description
Technical Field
The invention relates to the technical field of ground time service and optical fiber communication, in particular to a high-precision time service system for ground Beidou based on a ground optical fiber network.
Background
With the development of scientific technology, various devices and technologies need to be based on high-precision time and frequency. For example, the establishment of intelligent traffic systems and the implementation of digitized earth both need to be based on high precision time and frequency; various monitoring and weapon firing, etc. of modern wars also need to be based on high precision time and frequency. At present, the most widely used time service system is a time service system based on a satellite navigation system, and the time service system is also commonly called a space-based time service system because the time service system is based on the satellite navigation system. Such as GPS in the united states, GLONASS in russia, GALILEO in europe and the beidou system in china. The space-based time service system depends on satellite transmission signals, namely, the wireless network transmission signals are easy to be interfered by the outside and cannot be used (such as artificial electromagnetic wave interference), and are also easy to be influenced by weather or climate. Moreover, signals can only be used in open air, and the satellite signals cannot be used if the satellite signals are blocked by obstacles. Obviously, the high-precision time service system based on the satellite in the prior art has the problems of being easily interfered, being easily influenced by weather or climate, being only capable of adopting signals in an open place and the like.
Disclosure of Invention
The invention provides a high-precision time service system for ground Beidou based on a ground optical fiber network, which aims to solve the problems that the high-precision time service system based on a satellite in the prior art is easy to interfere, is easy to be influenced by weather or climate, can only adopt signals in open places and the like. The invention relates to a high-precision time service system for ground Beidou based on a ground optical fiber network, which comprises four levels of zero-level, first-level, second-level and third-level optical fiber networks, wherein a level calibration mechanism is adopted to keep the clock synchronization of each level of optical fiber network, a single-fiber bidirectional calibration method is adopted to realize the clock synchronization of each level of optical fiber network, wherein,
the zero-order optical fiber network is a polygonal grid node network and at least comprises more than two grid nodes, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; the grid nodes are system time service centers, wherein at least one time service center is provided with a cesium atomic clock with the precision of 600 ten-thousand years difference of 1 second, at least one time service center is provided with a high-grade cesium atomic clock with the precision of 1500 ten-thousand years difference of 1 second, and the relative time drift accumulation of the pulse per second 1PPS and the UTC is less than or equal to 0.5 ns/day; the zero-order optical fiber network takes the average time of each grid node as a time service reference;
the primary optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and at least three routes of the first-level optical fiber network are connected with the zero-level optical fiber network, wherein one route is a main route of the normal channel, and the other two routes are standby routes; the grid nodes of the first-level optical fiber network are all provided with cesium atomic clocks or hydrogen atomic clocks, and are synchronous with the clock of the zero-level optical fiber network, and the time frequency reference of the cesium atomic clocks or the hydrogen atomic clocks is as follows: the relative frequency deviation is less than or equal to +/-5E-15/day to +/-1E-14/day, the relative phase deviation is less than or equal to +/-1 ns/day, and the relative time interval deviation is less than or equal to 0.5 ns-1 ns;
the second-level optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and at least three routes of the secondary optical network are connected with the primary optical network, wherein one route is a main route of the normal channel, and the other two routes are standby routes; the grid nodes of the secondary optical fiber network are all provided with rubidium atomic clocks and are synchronous with the clock of the primary optical fiber network;
the three-level optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and, the tertiary optical network has at least three routes to link with second optical network, wherein, one is the route of normal open circuit, another two are the spare routes; the grid nodes of the three-level backbone optical fiber network are provided with rubidium atomic clocks or controlled crystal clocks X01 or X02 or X03 and are synchronous with the clock of the second-level optical fiber network; the controlled crystal clocks X01, X02 and X03 respectively adopt a digital compensation crystal oscillator DCXO, a voltage control type crystal oscillator VCXO-1 and a voltage control type crystal oscillator VCXO-2;
the step calibration mechanism is adopted to maintain the clock synchronization of each layer of optical fiber network, which means that the whole system automatically maintains the clock synchronization step by step uninterruptedly according to the sequence of a high-grade cesium atomic clock → a cesium atomic clock or a hydrogen atomic clock → rubidium atomic clock → DCXO → VCXO-1 → VCXO-2, and comprises the following steps: respectively setting master-slave synchronous relations according to the sequence, namely, the high-grade cesium atomic clock and the cesium atomic clock or the hydrogen atomic clock are in master-slave synchronous relation, the cesium atomic clock or the hydrogen atomic clock and the rubidium atomic clock are in master-slave synchronous relation, the rubidium atomic clock and the DCXO are in master-slave synchronous relation, and so on; the slave clocks are all kept synchronous by taking the master clock as a reference;
the method comprises the steps that a single-fiber ultra-high precision time transfer method is adopted between every two nodes connected with the two ends of a master-slave synchronization relation to ensure the clock synchronization between the two nodes, namely, a master synchronization device is arranged on a master synchronization side, a slave synchronization device is arranged on a slave synchronization side, and the master synchronization side and the slave synchronization side are connected by adopting a single-fiber multiplexing device; the optical fiber time delay value and the change value thereof between the main synchronous side synchronization equipment and the slave synchronous side synchronization equipment are accurately measured and then compensated; taking a clock at the master synchronization side as a time source; wherein,
a master synchronization device: the method mainly tracks a time source, modulates/demodulates time information to a single-fiber bidirectional optical transceiver module, and completes total time delay measurement and time signal bidirectional comparison;
the slave synchronization device: the method mainly realizes the phase-locked tracking technology of the clock, and realizes the ultra-high precision time synchronization and the coding and decoding of time signals;
a single fiber multiplexing device; the optical fiber delay compensation device comprises a delay processing module and a single-fiber bidirectional optical transceiver module, wherein the delay processing module is mainly used for eliminating asymmetric difference values caused by different wavelengths and completing dynamic compensation of transmission delay; the single-fiber bidirectional optical transceiver module adopts a wavelength division multiplexing technology to convert transmitted optical wavelengths, and then performs reverse conversion on the transmitted optical wavelengths to the opposite end, and simultaneously allows the two optical wavelengths to respectively transmit information through different optical channels in the same optical fiber, so that the two optical wavelengths respectively transmit information in different ways, thereby realizing the opposite transmission of optical signals on the same optical fiber;
moreover, jitter noise introduced in the optical fiber transmission process is filtered and compensated through repeated measurement for multiple times in a short time; the negative effects of delay skew, stripping and cleaving fiber delay drift accumulation due to temperature and aging are removed by periodic intermittent fiber delay testing.
Furthermore, the invention discloses a high-precision time service system for ground Beidou based on a ground optical fiber network, which adopts the optical fiber time delay value and the change value between the master synchronization side synchronization equipment and the slave synchronization side synchronization equipment to be accurately measured and then compensated, and comprises the following steps:
(1) setting the time synchronization of the main synchronization equipment as a clock for tracking the optical fiber network of the current level, wherein the tracking precision is +/-1 ns; modulating/demodulating a 1PPS frame header signal with a time signal to a single-fiber bidirectional optical transceiver module;
(2) the slave synchronization equipment carries out frequency synchronization, and the tracking precision is less than or equal to 5 multiplied by 10E-14;
(3) the total delay value is measured, and the master-slave delay T is calculated by the following formulaABThe master synchronizing device advances the time information by T through a phase-shifting networkABTherefore, the synchronous time precision can reach +/-5 ns;
C＝TAB+TBA＝(TASS+TABλ1+TBSR)+(TBSS+TBAλ2+TASR)(1)
in the formula, TABIs the time delay from the master synchronous side to the slave synchronous side, TBAFor time delay from the synchronizing side to the master synchronizing side, TASSIn the master synchronous side equipmentTransmission delay, TABλ1Is the optical fiber transmission time delay from the master synchronous side to the slave synchronous side, TBSRFor receiving time delay, T, from the device on the synchronization sideBSSFor transmitting time delay, T, from within the synchronization-side deviceBAλ2For the fibre transmission delay from the synchronous side to the primary synchronous side, TASRReceiving time delay in the main synchronization side equipment; the master synchronization side comprises master synchronization equipment, a time delay processing module and a single-fiber bidirectional optical transceiver module, and the slave synchronization side comprises slave synchronization equipment, a time delay processing module and a single-fiber bidirectional optical transceiver module;
(4) the slave synchronization side performs frequency synchronization and time synchronization for a long time, and ensures that an accurate pulse per second 1PPS signal can be obtained, and the slave synchronization side clock and the master synchronization side clock are synchronized.
Furthermore, the high-precision time service system for the ground Beidou based on the ground optical fiber network carries out repeated measurement for many times in a short time and compensates and filters the jitter noise introduced in the optical fiber transmission process, and comprises the steps of accurately measuring the optical fiber time delay value and the change value between the master synchronization equipment and the slave synchronization equipment, then compensating, and carrying out measurement and compensation for more than 80 times in 1 second.
Furthermore, the high-precision time service system for the ground Beidou based on the ground optical fiber network removes the time delay deviation generated by temperature and aging through periodic discontinuous total time delay test, and comprises the steps of accurately measuring the optical fiber time delay value and the change value between the master and slave synchronous equipment and then compensating, wherein the interval time is more than 500 seconds, so that the negative influence of accumulated time delay drift of the stripped and cut optical fiber is eliminated.
The ground optical fiber network-based high-precision time service system for the ground Beidou has the beneficial technical effects that a ground time service system which is mutually standby and mutually supported with a space-based time service system (such as a GPS/GLONASS/Beidou satellite navigation system) can be formed, and the ground time service system has the characteristics of low cost, strong anti-interference capability, high survivability and the like and provides the most basic time service for military and civil communication navigation and positioning systems in China.
Drawings
FIG. 1 is a schematic structural diagram of a zero-level network and a first-level network of a high-precision time service system for ground Beidou based on a ground optical fiber network;
FIG. 2 is a master-slave synchronization schematic diagram of a high-precision time service system for ground Beidou based on a ground optical fiber network.
The high-precision time service system for ground Beidou based on the ground optical fiber network is further described below with reference to the accompanying drawings and the specific implementation mode.
Detailed Description
FIG. 1 is a schematic structural diagram of a zero-order network and a first-order network of a high-precision time service system for ground Beidou based on a ground optical fiber network, wherein L0-L6 are zero-order optical fiber network grid nodes, and F0-F6 are first-order optical fiber network grid nodes. As can be seen from the figure, the high-precision time service system for the ground Beidou based on the ground optical fiber network comprises four levels of optical fiber networks, namely a zero level optical fiber network, a first level optical fiber network, a second level optical fiber network and a third level optical fiber network, wherein a level calibration mechanism is adopted to keep the clock synchronization of each level of optical fiber network, a single-fiber bidirectional calibration method is adopted to realize the clock synchronization of each level of optical fiber network, wherein,
the zero-order optical fiber network is a polygonal grid node network and at least comprises more than two grid nodes, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; the grid nodes are system time service centers, wherein at least one time service center is provided with a cesium atomic clock with the precision of 600 ten-thousand years difference of 1 second, at least one time service center is provided with a high-grade cesium atomic clock with the precision of 1500 ten-thousand years difference of 1 second, and the comparison time drift accumulation of pulse 1PPS and UTC per second is less than or equal to 0.5 ns/day; the zero-order optical fiber network takes the average time of each grid node as a time service reference;
the primary optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and at least three routes of the first-order optical fiber network are connected with the zero-order optical fiber network, wherein one route is a normal-open route, and the other two routes are standby routes; the grid nodes of the first-level optical fiber network are all provided with cesium atomic clocks or hydrogen atomic clocks, and are synchronous with the clock of the zero-level optical fiber network, and the time frequency reference of the cesium atomic clocks or the hydrogen atomic clocks is as follows: the relative frequency deviation is less than or equal to +/-5E-15/day to +/-1E-14/day, the relative phase deviation is less than or equal to +/-1 ns/day, and the relative time interval deviation is less than or equal to 0.5 ns-1 ns;
the second-level optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and at least three routes of the secondary optical network are connected with the primary optical network, wherein one route is a normal-open route, and the other two routes are standby routes; the grid nodes of the secondary optical fiber network are all provided with rubidium atomic clocks and are synchronous with the clock of the primary optical fiber network;
the three-level optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and, the tertiary optical network has at least three routes to link with second optical network, wherein, one is the route of normal open circuit, another two are the spare routes; the grid nodes of the three-level backbone optical fiber network are provided with rubidium atomic clocks or controlled crystal clocks X01 or X02 or X03 and are synchronous with the clock of the second-level optical fiber network; the controlled crystal clocks X01, X02 and X03 respectively adopt a digital compensation crystal oscillator DCXO, a voltage control type crystal oscillator VCXO-1 and a voltage control type crystal oscillator VCXO-2;
the step calibration mechanism is adopted to maintain the clock synchronization of each layer of optical fiber network, which means that the whole system automatically maintains the clock synchronization step by step uninterruptedly according to the sequence of a high-grade cesium atomic clock → a cesium atomic clock or a hydrogen atomic clock → rubidium atomic clock → DCXO → VCXO-1 → VCXO-2, and comprises the following steps: respectively setting master-slave synchronous relations according to the sequence, namely, the high-grade cesium atomic clock and the cesium atomic clock or the hydrogen atomic clock are in master-slave synchronous relation, the cesium atomic clock or the hydrogen atomic clock and the rubidium atomic clock are in master-slave synchronous relation, the rubidium atomic clock and the DCXO are in master-slave synchronous relation, and so on; the slave clocks are all kept synchronous by taking the master clock as a reference;
the clock synchronization of each layer of optical fiber network is realized by adopting a single-fiber bidirectional calibration method, and the clock synchronization between the master and slave synchronization relationship is ensured by adopting a single-fiber ultra-high precision time transfer method between every two nodes connected with the two ends of the master-slave synchronization relationship, namely, a master synchronization device is arranged at a master synchronization side, a slave synchronization device is arranged at a slave synchronization side, the master and slave synchronization sides are connected by adopting a single-fiber multiplexing device, and the optical fiber time delay value and the change value thereof between the master and slave synchronization side synchronization devices are accurately measured and then compensated; and the clock of the master synchronization side is used as a time source, wherein,
a master synchronization device: the method mainly tracks a time source, modulates/demodulates time information to a single-fiber bidirectional optical transceiver module, and completes total time delay measurement and time signal bidirectional comparison;
the slave synchronization device: the method mainly realizes the phase-locked tracking technology of the clock, and realizes the ultra-high precision time synchronization and the coding and decoding of time signals;
single-fiber multiplexing equipment: the optical fiber delay compensation device comprises a delay processing module and a single-fiber bidirectional optical transceiver module, wherein the delay processing module is mainly used for eliminating asymmetric difference values caused by different wavelengths and completing dynamic compensation of transmission delay; the single-fiber bidirectional optical transceiver module adopts a wavelength division multiplexing technology to convert transmitted optical wavelengths, and then performs reverse conversion on the transmitted optical wavelengths to the opposite end, and simultaneously allows the two optical wavelengths to respectively transmit information through different optical channels in the same optical fiber, so that the two optical wavelengths respectively transmit information in different ways, thereby realizing the opposite transmission of optical signals on the same optical fiber;
moreover, jitter noise introduced in the optical fiber transmission process is filtered and compensated through repeated measurement for multiple times in a short time; the negative effects of accumulated delay variation, stripping and splitting of the optical fiber due to temperature and aging are removed by periodic intermittent total delay testing.
Fig. 2 is a master-slave synchronization schematic diagram of a high-precision time service system for ground Beidou based on a ground optical fiber network, wherein 1 is a master synchronization device, 2 is a slave synchronization device, 3 is a single-fiber multiplexing device, 4 is a master synchronization side clock, and 5 is a slave synchronization side clock. It can be known from the figure that the clock synchronization of each level of the optical fiber network is realized by adopting a single-fiber bidirectional calibration method, including that a single-fiber ultra-high precision time transfer method is adopted between every two nodes connecting the two ends of the master-slave synchronization relationship to ensure the clock synchronization between the two nodes, namely, a master synchronization device is arranged at the master synchronization side, a slave synchronization device is arranged at the slave synchronization side, the master synchronization side and the slave synchronization side are connected by adopting a single-fiber multiplexing device, and the compensation is carried out after the optical fiber time delay value and the variation value thereof between the master synchronization device and the slave synchronization device are accurately measured; and the clock of the master synchronization side is used as a time source, wherein,
a master synchronization device: the method mainly tracks a time source, modulates/demodulates time information to a single-fiber bidirectional optical transceiver module, and completes total time delay measurement and time signal bidirectional comparison;
the slave synchronization device: the method mainly realizes the phase-locked tracking technology of the clock, and realizes the ultra-high precision time synchronization and the coding and decoding of time signals;
single-fiber multiplexing equipment: the optical fiber delay compensation device comprises a delay processing module and a single-fiber bidirectional optical transceiver module, wherein the delay processing module is mainly used for eliminating asymmetric difference values caused by different wavelengths and completing dynamic compensation of transmission delay; the single fiber multiplexing equipment adopts the wavelength division multiplexing technology to convert the transmitted optical wavelength, and then carries out reverse conversion to the opposite end, and simultaneously two optical wavelengths transmit information respectively through different optical channels in the same optical fiber, so that the two optical wavelengths respectively transmit information in different ways, thereby realizing the opposite transmission of optical signals on the same optical fiber;
the method comprises the following specific steps:
(1) setting the time synchronization of the main synchronization equipment as a clock for tracking the optical fiber network of the current level, wherein the tracking precision is +/-1 ns; modulating/demodulating a 1PPS frame header signal with a time signal to a single-fiber bidirectional optical transceiver module;
(2) the slave synchronization equipment carries out frequency synchronization, and the tracking precision is +/-5E-14;
(3) the total delay value is measured, and the master-slave delay T is calculated by the following formulaABThe master synchronizing device advances the time information by T through a phase-shifting networkABTherefore, the synchronous time precision can reach +/-5 ns;
C＝TAB+TBA＝(TASS+TABλ1+TBSR)+(TBSS+TBAλ2+TASR)(1)
in the formula, TABIs the time delay from the master synchronous side to the slave synchronous side, TBAFor time delay from the synchronizing side to the master synchronizing side, TASSFor transmission delay, T, in the master synchronization side equipmentABλ1Is the optical fiber transmission time delay from the master synchronous side to the slave synchronous side, TBSRFor receiving time delay, T, from the device on the synchronization sideBSSFor transmitting time delay, T, from within the synchronization-side deviceBAλ2For the fibre transmission delay from the synchronous side to the primary synchronous side, TASRReceiving time delay in the main synchronization side equipment; the master synchronization side comprises master synchronization equipment, a time delay processing module and a single-fiber bidirectional optical transceiver module, and the slave synchronization side comprises slave synchronization equipment, a time delay processing module and a single-fiber bidirectional optical transceiver module;
(4) the slave synchronization side performs frequency synchronization and time synchronization for a long time, and ensures that an accurate pulse per second 1PPS signal can be obtained, and the slave synchronization side clock and the master synchronization side clock are synchronized.
In order to filter out jitter noise introduced in the optical fiber transmission process, the high-precision time service system for the ground Beidou based on the ground optical fiber network is filtered by repeatedly measuring and compensating for many times in a short time, and comprises the steps of accurately measuring and compensating for optical fiber time delay values and change values between master and slave synchronous equipment, and measuring and compensating for more than 80 times in 1 second.
In order to remove time delay deviation caused by temperature and aging, the high-precision time service system for the ground Beidou based on the ground optical fiber network is removed through intermittent total time delay test, the high-precision time service system comprises a main synchronous device and a slave synchronous device, optical fiber time delay values and change values of the optical fiber time delay values are accurately measured and then compensated, and the interval time is more than 500 seconds.
The ground optical fiber network-based high-precision time service system for the ground Beidou has the beneficial technical effects that a ground time service system which is mutually standby and mutually supported with a space-based time service system (such as a GPS/GLONASS/Beidou satellite navigation system) can be formed, and the ground time service system has the characteristics of low cost, strong anti-interference capability, high survivability and the like and provides the most basic time service for military and civil communication navigation and positioning systems in China.
Claims (4)
1. The utility model provides a be used for high accuracy time service system of ground big dipper based on ground optical fiber network which characterized in that: the system comprises four levels of optical fiber networks including zero level, first level, second level and third level, a level calibration mechanism is adopted to keep the clock synchronization of each level of optical fiber network, a single-fiber bidirectional calibration method is adopted to realize the clock synchronization of each level of optical fiber network, wherein,
the zero-order optical fiber network is a polygonal grid node network and at least comprises more than two grid nodes, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; the grid nodes are system time service centers, wherein at least one time service center is provided with a cesium atomic clock with the precision of 600 ten-thousand years difference of 1 second, at least one time service center is provided with a high-grade cesium atomic clock with the precision of 1500 ten-thousand years difference of 1 second, and the relative time drift accumulation of the pulse per second 1PPS and the UTC is less than or equal to 0.5 ns/day; the zero-order optical fiber network takes the average time of each grid node as a time service reference;
the primary optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and at least three routes of the first-level optical fiber network are connected with the zero-level optical fiber network, wherein one route is a main route of the normal channel, and the other two routes are standby routes; the grid nodes of the first-level optical fiber network are all provided with cesium atomic clocks or hydrogen atomic clocks, and are synchronous with the clock of the zero-level optical fiber network, and the time frequency reference of the cesium atomic clocks or the hydrogen atomic clocks is as follows: the relative frequency deviation is less than or equal to +/-5E-15/day to +/-1E-14/day, the relative phase deviation is less than or equal to +/-1 ns/day, and the relative time interval deviation is less than or equal to 0.5 ns-1 ns;
the second-level optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and at least three routes of the secondary optical network are connected with the primary optical network, wherein one route is a main route of the normal channel, and the other two routes are standby routes; the grid nodes of the secondary optical fiber network are all provided with rubidium atomic clocks and are synchronous with the clock of the primary optical fiber network;
the three-level optical fiber network is an annular, tree-shaped or honeycomb grid node network, and at least three routes are arranged between every two grid nodes, wherein one route is a normally open route, and the other two routes are standby routes; and, the tertiary optical network has at least three routes to link with second optical network, wherein, one is the route of normal open circuit, another two are the spare routes; the grid nodes of the three-level backbone optical fiber network are provided with rubidium atomic clocks or controlled crystal clocks X01 or X02 or X03 and are synchronous with the clock of the second-level optical fiber network; the controlled crystal clocks X01, X02 and X03 respectively adopt a digital compensation crystal oscillator DCXO, a voltage control type crystal oscillator VCXO-1 and a voltage control type crystal oscillator VCXO-2;
the step calibration mechanism is adopted to maintain the clock synchronization of each layer of optical fiber network, which means that the whole system automatically maintains the clock synchronization step by step uninterruptedly according to the sequence of a high-grade cesium atomic clock → a cesium atomic clock or a hydrogen atomic clock → rubidium atomic clock → DCXO → VCXO-1 → VCXO-2, and comprises the following steps: respectively setting master-slave synchronous relations according to the sequence, namely, the high-grade cesium atomic clock and the cesium atomic clock or the hydrogen atomic clock are in master-slave synchronous relation, the cesium atomic clock or the hydrogen atomic clock and the rubidium atomic clock are in master-slave synchronous relation, the rubidium atomic clock and the DCXO are in master-slave synchronous relation, and so on; the slave clocks are all kept synchronous by taking the master clock as a reference;
the method comprises the steps that a single-fiber ultra-high precision time transfer method is adopted between every two nodes connected with the two ends of a master-slave synchronization relation to ensure the clock synchronization between the two nodes, namely, a master synchronization device is arranged on a master synchronization side, a slave synchronization device is arranged on a slave synchronization side, and the master synchronization side and the slave synchronization side are connected by adopting a single-fiber multiplexing device; the optical fiber time delay value and the change value thereof between the main synchronous side synchronization equipment and the slave synchronous side synchronization equipment are accurately measured and then compensated; taking a clock at the master synchronization side as a time source; wherein,
a master synchronization device: the method mainly tracks a time source, modulates/demodulates time information to a single-fiber bidirectional optical transceiver module, and completes total time delay measurement and time signal bidirectional comparison;
the slave synchronization device: the method mainly realizes the phase-locked tracking technology of the clock, and realizes the ultra-high precision time synchronization and the coding and decoding of time signals;
a single fiber multiplexing device; the optical fiber delay compensation device comprises a delay processing module and a single-fiber bidirectional optical transceiver module, wherein the delay processing module is mainly used for eliminating asymmetric difference values caused by different wavelengths and completing dynamic compensation of transmission delay; the single-fiber bidirectional optical transceiver module adopts a wavelength division multiplexing technology to convert transmitted optical wavelengths, and then performs reverse conversion on the transmitted optical wavelengths to the opposite end, and simultaneously allows the two optical wavelengths to respectively transmit information through different optical channels in the same optical fiber, so that the two optical wavelengths respectively transmit information in different ways, thereby realizing the opposite transmission of optical signals on the same optical fiber;
moreover, jitter noise introduced in the optical fiber transmission process is filtered and compensated through repeated measurement for multiple times in a short time; the delay variation due to temperature and aging is removed by periodic intermittent fiber delay testing.
2. The ground-based optical fiber network-based high-precision time service system for the ground Beidou according to claim 1, characterized in that: the method adopts the optical fiber time delay value and the change value between the main synchronous side and the slave synchronous side synchronous equipment to be accurately measured and then compensated, and comprises the following steps:
(1) setting the time synchronization of the main synchronization equipment as a clock for tracking the optical fiber network of the current level, wherein the tracking precision is +/-1 ns; modulating/demodulating a 1PPS frame header signal with a time signal to a single-fiber bidirectional optical transceiver module;
(2) the slave synchronization equipment carries out frequency synchronization, and the tracking precision is less than or equal to 5 multiplied by 10E-14;
(3) the total delay value is measured, and the master-slave delay T is calculated by the following formulaABThe master synchronizing device advances the time information by T through a phase-shifting networkABTherefore, the synchronous time precision can reach +/-5 ns;
in the formula, TABIs the time delay from the master synchronous side to the slave synchronous side, TBAFor time delay from the synchronizing side to the master synchronizing side, TASSFor the transmission delay in the master synchronization side device,is the optical fiber transmission time delay from the master synchronous side to the slave synchronous side, TBSRFor receiving time delay, T, from the device on the synchronization sideBSSIn order to transmit the time delay from within the synchronization side device,to be slave-synchronizedSide-to-master synchronization side optical fiber transmission delay, TASRReceiving time delay in the main synchronization side equipment; the master synchronization side comprises master synchronization equipment and single-fiber multiplexing equipment, and the single-fiber multiplexing equipment comprises a time delay processing module and a single-fiber bidirectional optical transceiver module; the slave synchronization side comprises slave synchronization equipment and single-fiber multiplexing equipment, wherein the single-fiber multiplexing equipment comprises a time delay processing module and a single-fiber bidirectional optical transceiver module;
(4) the slave synchronization side performs frequency synchronization and time synchronization for a long time, and ensures that an accurate pulse per second 1PPS signal can be obtained, and the slave synchronization side clock and the master synchronization side clock are synchronized.
3. The ground-based optical fiber network-based high-precision time service system for the ground Beidou according to claim 1, characterized in that: the method comprises the steps of carrying out repeated measurement for many times in a short time and compensating and filtering jitter noise introduced in the optical fiber transmission process, accurately measuring the optical fiber time delay value and the change value thereof between the master and slave synchronous devices, then compensating, and carrying out measurement and compensation for more than 80 times in 1 second.
4. The ground-based optical fiber network-based high-precision time service system for the ground Beidou according to claim 1, characterized in that: the time delay deviation caused by temperature and aging is removed through periodic discontinuous total time delay test, the time delay deviation is compensated after the optical fiber time delay value and the change value thereof between the master and slave synchronous equipment are accurately measured, and the interval time is more than 500 seconds, so that the negative influence of the accumulated time delay drift of the stripped and divided optical fiber is avoided.
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