CN111106870B - Super-long-distance dual-fiber interconnected multistage optical fiber time frequency transmission system - Google Patents
Super-long-distance dual-fiber interconnected multistage optical fiber time frequency transmission system Download PDFInfo
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Abstract
The invention provides an ultra-long distance double-fiber interconnected multistage optical fiber time frequency transmission system, which is provided with one or more transmission units, wherein each transmission unit comprises a plurality of optical fiber single-channel time frequency high-precision transmission devices, a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion and optical fibers connected with the devices.
Description
Technical Field
The invention relates to a time frequency transmission system, in particular to an ultra-long distance multi-stage optical fiber time frequency transmission system, and belongs to the technical field of time frequency.
Background
At present, the transmission of the ultra-long distance time frequency mostly adopts optical fiber transmission, the transmission of time signals and the transmission of frequency signals are carried out separately, and the second pulse transmission synchronously occupies one channel; the frequency signal transmission occupies two channels, one channel is used for transmitting sine wave signals from a local end to a remote end, the other channel is used for transmitting sine wave signals returned from the remote end to the local end so as to eliminate the influence of line delay variation, and 3 optical fiber channels are used for the transmission of the whole time frequency, so that the waste of optical fiber resources is caused.
In particular, in the process of time frequency transmission, once an abnormality occurs in one device or optical fiber, signal interruption occurs in the whole system, and the system reliability is poor.
Therefore, it is necessary to research an ultra-long distance time-frequency transmission system with less fiber resource occupation and safe and reliable system.
Disclosure of Invention
In order to solve the above problems, the present inventors have made intensive studies to increase the number of devices to be arranged and to perform cross transmission in different stages of time-frequency signal transmission, thereby completing the present invention.
In one aspect, the invention provides an ultra-long distance dual-fiber interconnected multistage optical fiber time-frequency transmission system, which is provided with one or more transmission units.
The transmission unit comprises a plurality of optical fiber single-channel time frequency high-precision transmission devices, a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion and optical fibers connected with the time frequency signal synthesis devices.
The transmission unit comprises two optical fiber single-channel time frequency high-precision transmission devices and two time frequency signal synthesis devices based on multi-source time frequency signal fusion.
The plurality of transmission units can be connected with each other to realize multi-stage connection,
the time frequency signal received by the optical fiber single-channel time frequency high-precision transmission device is output by a local high-precision time frequency real-time synthesis device, and the time frequency signal comprises a frequency signal and a pulse per second signal.
The single-channel time frequency high-precision transmission device comprises a local end 1 and a remote end 2, signals between the local end 1 and the remote end 2 are transmitted in a single channel through optical fibers,
the local high-precision time-frequency real-time integrated device is connected with the local ends of a plurality of optical fiber single-channel time-frequency high-precision transmission devices in the first-stage transmission unit through cables.
The remote end of the optical fiber single-channel time frequency high-precision transmission device transmits the time frequency signals to a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion.
The time frequency signal synthesis device based on multi-source time frequency signal fusion at the previous stage is connected with the local end of the optical fiber single-channel time frequency high-precision transmission device at the next stage.
On the other hand, the invention also provides a method for transmitting the time frequency of the super-long-distance double-fiber interconnected multistage optical fiber, and the method can be used for performing cross transmission in different links of time frequency signal transmission by increasing the configuration number of devices, so that the operation of a time frequency transmission system is stable.
The method comprises the following processes:
1) establishing a transmission unit;
2) the local high-precision time frequency real-time comprehensive device is connected with the transmission unit;
3) and a plurality of transmission units are connected with each other.
The establishing and transferring unit comprises the following sub-processes:
11) the local end and the remote end of the multiple optical fiber single-channel time frequency high-precision transmission devices are respectively connected through independent optical fibers, so that the local end and the remote end of each optical fiber single-channel time frequency high-precision transmission device can transmit time frequency signals;
12) connecting a second crystal oscillator module at the far end of each optical fiber single-channel time frequency high-precision transmission device with down-conversion modules of a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables; connecting a pulse-per-second receiving and processing module at the far end of each optical fiber single-channel time frequency high-precision transmission device with pulse-per-second processing modules of a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables, so that the time frequency signals received by the plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion are the same;
the real-time integrated device of local high accuracy time frequency is connected with the transmission element, includes:
connecting a crystal oscillator unit of the local high-precision time-frequency real-time integrated device with a plurality of first down-conversion modules at the local end of the optical fiber single-channel time-frequency high-precision transmission device in a transmission unit through cables; the pulse per second generating unit of the local high-precision time frequency real-time integrated device is connected with the pulse per second sending and processing module at the local end of the multiple optical fiber single-channel time frequency high-precision transmission devices in the transmission unit through cables, so that time frequency signals received by the local end of the multiple optical fiber single-channel time frequency high-precision transmission devices are the same.
The super-long-distance dual-fiber interconnected multistage optical fiber time frequency transmission system provided by the invention has the following beneficial effects:
(1) the time frequency signal output precision is high;
(2) the time frequency signal output stability is good;
(3) the system has high reliability, and the normal operation of the transmission system cannot be influenced when one optical fiber or one device in the system is abnormal.
Drawings
FIG. 1 is a schematic diagram of a preferred embodiment of an ultra-long distance dual-fiber interconnected multi-stage fiber time-frequency transmission system;
FIG. 2 shows a schematic diagram of a single channel time-frequency high-precision delivery apparatus according to a preferred embodiment;
FIG. 3 is a block diagram showing a configuration of a single-channel time-frequency high-precision transmission apparatus according to a preferred embodiment;
fig. 4 shows a time-frequency signal synthesis device based on multi-source time-frequency signal fusion in a preferred embodiment.
Detailed Description
The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention, as illustrated in the accompanying drawings.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
In one aspect, the present invention provides an ultra-long distance dual-fiber interconnected multi-stage optical fiber time-frequency transmission system, as shown in fig. 1, having one or more transmission units,
the transmission unit comprises a plurality of optical fiber single-channel time frequency high-precision transmission devices, a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion and optical fibers connected with the devices,
in a preferred embodiment, the transmission unit comprises two optical fiber single-channel time frequency high-precision transmission devices and two time frequency signal synthesis devices based on multi-source time frequency signal fusion.
Further, the plurality of transmission units can be connected with each other to realize multi-level connection, so that ultra-long distance connection and multi-node connection can be realized.
In a preferred embodiment, in the first stage of transmission unit, the time frequency signal received by the optical fiber single-channel time frequency high-precision transmission device is output by the local high-precision time frequency real-time synthesis device, the time frequency signal comprises a frequency signal and a pulse per second signal,
the local high-precision time-frequency real-time comprehensive device comprises a double-mixing time difference measuring unit, a data acquisition and storage unit, a processing unit, a control unit and a crystal oscillator unit.
Because the frequency of different atomic clock outputs has uncertainty deviation, some atomic clock output frequency's stability is better, and some atomic clock output frequency's the degree of accuracy is better, when synthesizing a plurality of atomic clocks to adopt suitable algorithm, can obtain the output frequency that stability and degree of accuracy are all more excellent, and then revise the crystal oscillator, thereby reach the effect that makes the crystal oscillator output more accurate time frequency signal.
Specifically, the double-mixing time difference measuring unit can receive an atomic clock frequency signal and measure the atomic clock frequency signal.
Further, the atomic clock is provided with a plurality of atomic clocks, so that more accurate frequency deviation can be obtained through synthesis,
the atomic clock frequency signals are input to a double-mixing time difference measuring unit in a sine wave form, the double-mixing time difference measuring unit accurately measures a plurality of input frequency signals (sine wave phases) by using a double-mixing time difference measuring technology to obtain phase differences among the atomic clock frequency signals, and the ratio of the variation of the phase differences to the measuring time interval is the relative frequency deviation.
When the double mixing time difference measuring unit measures the frequency signals of the atomic clock, one or more frequency points in 1 MHz-200 MHz can be selected for measurement,
according to the invention, the selection of the frequency point during measurement is determined by the performance of a double mixing time difference measuring unit and a crystal oscillator unit, wherein the performance of the double mixing time difference measuring unit refers to the noise coefficient, the performance of the crystal oscillator unit refers to the frequency stability of the crystal oscillator, and specifically:
when the noise coefficient of the double-mixing time difference measuring unit is large, measuring by adopting a low frequency point so as to reduce the influence of the noise of the double-mixing time difference measuring unit on an analysis result as much as possible;
when the noise coefficient of the double-mixing time difference measuring unit is small, a high frequency point is adopted for measurement so as to increase the control frequency of the crystal oscillator and enable the frequency signal output by the crystal oscillator to be more accurate;
when the performance of the crystal oscillator unit is better, the control frequency of the crystal oscillator unit can be properly reduced, namely the measurement frequency of the double-mixing time difference measurement unit is properly reduced;
when the performance of the crystal oscillator unit is poor, in order to improve the accuracy of the frequency signal output by the crystal oscillator, the measurement frequency of the double-mixing time difference measurement unit is improved to increase the control frequency of the crystal oscillator.
At present, the output nominal frequency of the atomic clock at home and abroad is one or the combination of 5MHz, 10MHz and 100 MHz. The invention continues to use this nominal frequency to determine the phase difference between the atomic clocks by compatible measurement of the one or more frequency points.
Furthermore, according to the phase deviation between each atomic clock and the controlled crystal oscillator measured by the double mixing time difference measuring unit, the relative frequency deviation between the controlled crystal oscillator and each atomic clock can be determined.
The double mixing time difference measuring unit is also provided with a mixer and an AD chip,
the AD chip is used for converting the measured relative frequency deviation into a digital signal and outputting the digital signal to the data acquisition and storage unit,
further, the relative frequency deviation comprises the measured relative frequency deviation between the atomic clock frequency signals and the relative frequency deviation between the crystal oscillator unit frequency signal and each atomic clock frequency signal.
The frequency mixer filters the atomic clock frequency signal and the crystal oscillator unit frequency signal from high frequency to low frequency, preferably, the frequency after frequency mixing is 100 Hz-10 kHz, so that the data acquisition and storage unit can acquire the signals and convert the signals into digital signals; more preferably 100Hz to 1kHz, so as to reduce the requirement on the acquisition frequency of the AD chip and reduce the manufacturing cost of the device.
And the data acquisition and storage unit is used for acquiring the digital signals output by the double-mixing time difference measurement unit and storing the measurement results to form historical data.
The processing unit can acquire the historical data in the data acquisition and storage unit and carry out comprehensive processing according to the historical data,
according to the invention, the comprehensive processing comprises the steps of integrating the frequency stability of a plurality of atomic clocks and/or the frequency accuracy of a plurality of atomic clocks and calculating the relative frequency deviation of the crystal oscillator.
The frequency accuracy of the integrated atomic clocks is processed according to the historical data of the relative frequency deviation among the atomic clocks and the accuracy weight,
specifically, the accuracy weight is obtained according to the accuracy degree of the output signal of each atomic clock, when the deviation of the frequency output by the atomic clock from the nominal value is smaller, the accuracy is higher,
and is
Wherein n represents the number of atomic clocks, i represents different atomic clocks, AiIndicating the accuracy of the atomic clock relative to a nominal value, derived from the atomic clock nominal,
represents the relative weight of the ith atomic clock, and the accuracy of the atomic clock is weighted by
The stability weight is obtained according to the stability of the output signals of each atomic clock, when the continuous output frequency of the atomic clocks is higher, the stability sigma is higher, and
where n denotes the number of atomic clocks, i denotes different atomic clocks, σiRepresents the ithStability of atomic clocks.
The Allen deviation of the relative frequency deviation of an atomic clock from a nominal value over a historical period of time can be defined as the stability of the atomic clockiThe historical time may be 1 hour to 1 month, more preferably 1 day to 10 days, and the weight of the stability of the atomic clock is
In a preferred embodiment, the processing unit integrates the frequency deviations of the plurality of atomic clocks by the following formula:
frequency deviation from accuracy weight
Wherein phiiThe current data of the frequency deviation of the crystal oscillator and the ith atomic clock are shown, n represents the number of the atomic clocks, i represents the ith atomic clock
Frequency deviation derived from stability weights
Wherein phiiThe current data is the frequency deviation current data of the crystal oscillator and the ith atomic clock, n represents the number of the atomic clocks, i represents the ith atomic clock, the current data is the data of the time interval from the last adjustment of the crystal oscillator to the current adjustment, and the time interval is preferably 1-100 seconds.
Further, the frequency deviation psi obtained by integrating the frequency stability weights of the multiple atomic clocksσFrequency deviation psi from frequency accuracy weights of multiple atomic clocksAA more stable and accurate frequency deviation can be obtained, preferably the final frequency deviation is obtained by the following formula: ΨZ＝αΨA+(1-α)ΨσWherein alpha is more than or equal to 0 and less than or equal to 1, alpha represents the specific gravity of the accuracy degree of the clock group,
this frequency deviation ΨZUsed as the increment of the crystal oscillator control voltage, by adjusting the crystal oscillator control voltage, psi is enabledZAs much as 0 as possible.
In a preferred embodiment, in order to ensure the adjustment accuracy, in the actual control, the frequency difference tracking control of the crystal oscillator is converted into the phase tracking control, and the phase alignment condition of the sine wave signal output by the crystal oscillator in each device is considered, so that the phase of the sine wave signal output by the crystal oscillator is uniformly coordinated in a whole network. The adjustment method is within the ability of those skilled in the art, and the specific adjustment method can be selected by those skilled in the art according to actual needs, which is not described herein.
In general, α is 0.5, so that the final frequency deviation can equivalently balance both the stability and the accuracy.
In another preferred embodiment, the value of α is adjusted according to the actual requirement, and the relative proportions of accuracy and stability are adjusted according to the specific application.
In the present invention, the control unit is able to obtain Ψ in the processing unitZAnd the relative frequency deviation value of the crystal oscillator unit, and the crystal oscillator unit is adjusted according to the value so as to correct the frequency signal output by the crystal oscillator, so that the frequency signal is more stable and accurate.
In the invention, the control unit can adjust the crystal oscillator unit by changing the crystal oscillator voltage.
Specifically, the control unit is provided with a DA module, the output end of the DA module is connected to the voltage control end of the crystal oscillator, and the control unit adjusts the output voltage of the DA module according to the relative frequency deviation value acquired from the processing unit, so that the final frequency deviation psi is achievedZAnd 0 is obtained as much as possible, so that the adjustment of the output frequency of the crystal oscillator unit is completed.
The local high-precision time-frequency real-time synthesis device is also provided with a pulse per second generation unit which can acquire the frequency output by the crystal oscillator unit and an external pulse per second signal and takes the external pulse per second signal as a reference signal for generating the pulse per second signal,
the second pulse generation unit can generate a plurality of second pulse signals from the zero crossing point of the frequency signal output by the crystal oscillation unit as the rising edge of the second pulse,
further, the pulse-per-second generating unit may be further configured to select one closest to the reference signal from the plurality of generated pulse-per-second signals as the pulse-per-second output signal.
According to the present invention, the optical fiber single-channel time-frequency high-precision transmission device is a transmission device capable of transmitting time frequency, preferably a single-channel time-frequency transmission device capable of saving channel resources is adopted, and more preferably, as shown in fig. 2, the single-channel time-frequency high-precision transmission device comprises a local end 1 and a remote end 2.
The signal between the local end 1 and the remote end 2 is transmitted by a single channel through an optical fiber, the local end 1 includes a first time-sharing module 11, the remote end 2 includes a second time-sharing module 21, the first time-sharing module 11 and the second time-sharing module 21 complete the transmission of the pulse-per-second signal and the frequency signal between the local end 1 and the remote end 2 in a time-sharing manner, wherein each 1 second of the single channel signal transmission is divided into 2N time periods, N is greater than or equal to 2, specifically:
in a period T1, the local end 1 sends a pulse per second signal to the remote end 2, and the remote end 2 receives the pulse per second signal; in the time period T2, the remote end 2 is switched to send a pulse per second signal, and the local end 1 receives the signal; after receiving the second pulse signal sent back by the remote end, the local end measures the time difference of sending the second pulse signal to the receiving end, deducts the fixed time delay of sending and receiving of the local end and the remote end to obtain the single transmission delay of the signal of the line, and can realize the preliminary synchronization of the second pulse signal of the remote end and the second pulse of the local end by controlling the delay value of a delay device;
in a time period T2N-1, N is 2-N, the state of sending a frequency signal by the local end 1 and receiving the frequency signal by the remote end 2 is switched, and the phase relation between the phase of the frequency signal received by the remote end and the phase relation between the frequency signal of the crystal oscillator output by the remote end crystal oscillator is measured;
in the time period of T2n, the state of sending frequency signal from the remote end 2 and receiving frequency signal from the local end 1 is switched, the phase relation between the frequency signal phase received by the local end 1 and the crystal oscillator frequency signal output by the local end crystal oscillator is measured, the crystal oscillator frequency phase change is controlled, the phase of the crystal oscillator frequency signal output by the remote end crystal oscillator is consistent with the phase of the standard frequency signal input to the local end,
the frequency signal and the pulse per second signal are used as a time signal mark, the pulse per second signal is used as a time coarse mark, the phase of the frequency signal is used as a time fine mark, and the phase of the frequency signal and the phase of the pulse per second signal keep a fixed alignment relation.
The single-channel time frequency high-precision transmission device realizes data communication and time and frequency high-precision transmission synchronization by utilizing digital measurement and control and time-sharing operation in a single channel.
Preferably, the first time-sharing module 11 and the second time-sharing module 21 complete the transmission of the pulse-per-second signal, the data coding pulse signal and the frequency signal between the local end 1 and the remote end 2 in a time-sharing manner, in a time period T1, the local end 1 sequentially sends the pulse-per-second signal and the data coding pulse signal to the remote end 2, and the remote end 2 sequentially receives the pulse-per-second signal and the data coding pulse signal; and in a period T2, switching to the remote end 2 to sequentially send a pulse per second signal and a data coding pulse signal, and the local end 1 receives the state, wherein the data coding pulse signal represents the characteristics of a source atomic clock, a transmission path and the like.
Preferably, the first time-sharing module 11 and the second time-sharing module 21 divide each 1 second of the single channel signal transmission into 2N +1 time periods, in the T2N +1 time period, the single channel is in an idle state, the local end does not signal to the remote end, the remote end does not signal to the local end, when a laser is used as a carrier wave in an optical fiber or a light with small interference is directionally propagated in space, there may be no idle time period of T2N +1, and when a wave with poor directivity is used as a carrier wave for radio waves, the idle time period of T2N +1 is used for not generating interference when other nearby local and remote ends communicate with each other to transfer time-frequency signals.
Preferably, the frequency signal is a sine wave signal, the frequency of the sine wave signal is an integer, and the fixed alignment relationship is that the zero-crossing point of the sine wave signal is aligned with the rising edge of the pulse per second signal.
According to the single-channel time frequency high-precision transmission device, on the basis that the phase of a frequency signal (sine wave signal) is consistent with that of a local frequency signal (sine wave signal) at a far end and the phase of a second pulse signal at the far end is initially synchronous with that of the second pulse at the local end, the zero crossing point of the frequency signal is converted into the rising edge of the second pulse, the second pulse in initial synchronization is used as a second pulse selection switch, and the pulse closest to the second pulse in initial synchronization is selected as the second pulse from a large number of pulses with the rising edge at the zero crossing point, so that the accurate second pulse signal is recovered.
Preferably, as shown in fig. 3, the local end 1 further includes:
the first signal comprehensive modulation module 15 modulates the pulse-per-second signal and the frequency signal to be transmitted on the carrier wave of the single channel at different times according to the instruction of the first time division module 11 in the transmission time period of the local end 1 and transmits the modulated signals to the remote end 2;
the first signal detection demodulation module 16 demodulates the pulse per second signal and the frequency signal sent by the remote end 2 from the carrier wave modulated by the single channel in the receiving period of the local end 1, and respectively outputs the pulse per second signal and the frequency signal to the pulse per second sending processing module 14 and the first down-conversion module 17;
a pulse per second transmission processing module 14 for obtaining the delay advance of a pulse per second signal, wherein an initial pulse per second signal is transmitted to the far-end 2 through the first signal comprehensive modulation module 15, the pulse per second signal demodulated by the first signal detection demodulation module 16 and sent back from the far-end 2 is received, the time interval between the rising edges of the two pulse per second signals is measured, the time interval is divided by 2 after the transmission and reception delays of the far-end and the local-end are deducted, a delay value of signal one-way transmission in a single channel is obtained, and the transmission delay of the local-end 1 and the reception delay of the far-end 2 are added as the next delay advance for transmitting the pulse per second signal;
the first crystal oscillator module 12 generates a crystal oscillator frequency signal and sends the crystal oscillator frequency signal to the first down-conversion module 17; the crystal oscillator frequency signal processed by the first signal acquisition processing control module 13 is used as a frequency signal to be transmitted in the local end 1 transmission time period and is transmitted to the first signal comprehensive modulation module 15;
the plurality of first down-conversion modules 17 down-convert the input standard frequency signal and send the signal to the first signal acquisition processing control module 13; performing down-conversion on the crystal oscillator frequency signal generated by the first crystal oscillator module 12, and sending the down-converted crystal oscillator frequency signal to the first signal acquisition processing control module 13; the frequency signal returned by the remote end 2 and passing through the first signal detection demodulation module 16 is subjected to down-conversion and sent to the first signal acquisition processing control module 13;
the first signal acquisition processing control module 13 includes a first a/D acquisition unit and a first D/a unit with multiple channels, the first a/D acquisition unit acquires a crystal oscillator frequency signal and a standard frequency signal after down-conversion and receives a frequency signal returned by the remote end 2 and demodulated by the first signal detection demodulation module 16 and down-converted by the first down-conversion module 17 to obtain a relative phase between the signals, and the D/a unit controls the crystal oscillator frequency signal output by the first crystal oscillator module 12 to make the phase of the signal after single-pass transmission of the crystal oscillator frequency signal through a single channel consistent with the phase of the standard frequency signal.
In the above local terminal, the standard frequency signal is input to the first down-conversion module and the pulse-per-second signal is input to the pulse-per-second transmission processing module, and preferably, a zero-crossing point of the standard frequency signal input to the local terminal 1 is aligned with a rising edge of the pulse-per-second signal.
Further, preferably, the local end 1 further includes:
the first data sending and receiving module 18 adds the data signal to be sent to the second pulse signal to generate a data coding pulse signal, and sends the data coding pulse signal to the first signal comprehensive modulation module 15; the data signal which is sent back by the remote end 2 and demodulated by the first detection demodulation module is received, the data signal to be sent is generated according to the operating condition of the local end 1, the data signal to be sent is added to the pulse per second signal generated by the pulse per second sending processing module 14, a data coding pulse signal to be sent in the sending time period of the local end 1 is formed, and the data coding pulse signal is sent to the first signal comprehensive modulation module 15.
Preferably, as shown in fig. 3, the distal end 2 further comprises:
the second signal detection demodulation module 26 demodulates the received pulse-per-second signal and frequency signal sent by the local end from the carrier wave modulated by the single channel in the receiving period of the remote end 2, and outputs the pulse-per-second signal and frequency signal to the pulse-per-second receiving processing module 24 and the second down-conversion module 27 respectively;
the second crystal oscillator module 22 generates a crystal oscillator frequency signal and sends the crystal oscillator frequency signal to the second down-conversion module 27; the crystal oscillator frequency signal processed by the second signal acquisition processing control module 23 is used as a frequency signal to be returned in the sending time period of the remote end 2 and sent to the second signal comprehensive modulation module 25; the crystal oscillator frequency signal processed by the second signal acquisition processing control module is output as a standard frequency signal of a time fine mark and is sent to the pulse per second receiving and processing module 24;
a plurality of second down-conversion modules 27, which down-convert the frequency signal demodulated by the second signal detection demodulation module 26 and the crystal oscillator frequency signal output by the second crystal oscillator module 22, and send the frequency signal to the second signal acquisition processing control module 23;
the second signal acquisition processing control module 23 includes a second a/D acquisition unit and a second D/a unit with multiple channels, the second a/D acquisition unit acquires a crystal oscillator frequency signal after down-conversion and a frequency signal demodulated by the second signal detection demodulation module 26 to obtain a relative phase between the crystal oscillator frequency signal and the frequency signal, and the second D/a unit controls the crystal oscillator frequency signal output by the second crystal oscillator module 22 to make the phase of the output crystal oscillator frequency signal consistent with the phase of the standard frequency signal input to the local terminal;
a second pulse-per-second receiving and processing module 24, which receives the pulse-per-second signal sent by the local terminal 1 and demodulated by the second signal detecting and demodulating module 26, takes the pulse-per-second signal as a reference signal for generating the pulse-per-second signal, outputs a zero-crossing point of a frequency signal from the second crystal oscillating module 22 as a rising edge of the pulse-per-second signal, generates a plurality of pulse-per-second signals, selects the pulse-per-second signal closest to the reference signal from the plurality of pulses to output as the pulse-per-second signal of the remote terminal 2, and sends the received pulse-per-second signal sent by the local terminal and demodulated by the second signal detecting and demodulating module to the second signal comprehensive modulating module 25 after a fixed delay;
the second signal comprehensive modulation module 25 modulates the pulse-per-second signal, the data coding pulse signal and the frequency signal to be transmitted in the transmission time interval of the remote end 2 at different times according to the instruction of the second time division module 21, and transmits the modulated signals to the local end 1 on a single-channel carrier.
Further, preferably, the remote end 2 further comprises:
the second data sending and receiving module 28 receives the data signal sent by the local end 1 demodulated by the second signal detection demodulation module 26, generates a data signal to be sent according to the operating condition of the remote end 2, adds the data signal to be sent to the pulse-per-second receiving and processing module 24 to generate a pulse-per-second signal, forms a data coding pulse signal to be returned in the sending period of the remote end 2, and sends the data coding pulse signal to the second signal comprehensive modulation module 25.
According to the invention, the local high-precision time-frequency real-time synthesis device is connected with the local ends of a plurality of optical fiber single-channel time-frequency high-precision transmission devices in the first-stage transmission unit through cables,
specifically, the crystal oscillator unit is connected with the first down-conversion module, the pulse-per-second generation unit is connected with the pulse-per-second sending and processing module, the frequency signal and the pulse-per-second signal are transmitted to the local end of the optical fiber single-channel time frequency high-precision transmission device, and the local end is transmitted to the remote end through an independent optical fiber.
According to the present invention, the remote ends of the plurality of optical fiber single channel time frequency high precision transmission devices respectively restore the signals to time frequency signals, and since the local ends of the plurality of optical fiber single channel time frequency high precision transmission devices receive the same time frequency signals, the time frequency signals restored by the remote ends of the plurality of optical fiber single channel time frequency high precision transmission devices are also the same.
According to the invention, the optical fiber single-channel time frequency high-precision transmission device is connected with the time frequency signal synthesis device based on multi-source time frequency signal fusion through a cable.
The time-frequency signal synthesis device based on multi-source time-frequency signal fusion is a device capable of fusing time-frequency signals, and has the characteristics that a certain source of the previous stage fails and the frequency signals are not directly interrupted to influence the high-precision transmission of the time frequency of the optical fiber of the next stage, preferably, as shown in figure 4,
the synthesis apparatus synthesizes signals of a plurality of sources, each of which outputs a frequency signal and a pulse per second signal, and includes: and a plurality of channels, some of which are used for simultaneously inputting a plurality of frequency signals (frequency signals 1, 2, …, n), some of which are used for simultaneously inputting a plurality of second pulse signals (second pulse signals 1, 2, …, n), the plurality of frequency signals transmitted through the channels are weighted and averaged to be used as standard frequency signals, the plurality of second pulse signals are averaged to obtain the second pulse signal closest to the averaged second pulse as a reference signal, the plurality of second pulse signals are generated by taking the zero-crossing point of the standard frequency signals as the rising edge of the second pulse signals, and the second pulse signal generated by the standard frequency signal closest to the reference signal is used as the output second pulse signal.
Preferably, as shown in fig. 4, the time-frequency signal synthesis apparatus based on multi-source time-frequency signal fusion further includes:
the plurality of down-conversion modules 10 are used for performing down-conversion on the frequency signals output by the plurality of sources and the crystal oscillator frequency signals output by the crystal oscillator module 20, and transmitting the frequency signals to the signal acquisition processing control module 30;
the crystal oscillator module 20 generates a crystal oscillator frequency signal and sends the crystal oscillator frequency signal to the down-conversion module 10; the crystal oscillator frequency signal processed by the signal acquisition processing control unit is used as an output standard frequency signal and is transmitted to the pulse per second receiving and processing module 40;
the signal acquisition processing control module 30 comprises a multi-channel A/D acquisition unit and a multi-channel D/A unit, wherein the A/D acquisition unit acquires frequency signals of a plurality of channels subjected to down-conversion to obtain relative phases among the frequency signals of the channels, a standard frequency signal is obtained by adopting weighted average, and the D/A unit controls the crystal oscillator frequency signal output by the crystal oscillator module 20 to enable the phase of the crystal oscillator frequency signal to be consistent with the phase of the standard frequency signal;
the pulse-per-second processing module 40 averages the pulse-per-second signals input to the respective channels, selects a pulse-per-second signal closest to the average value as a reference signal, generates a plurality of pulse-per-second signals by using a zero-crossing point position of the standard frequency signal of the crystal oscillator module 20 as a rising edge of the pulse-per-second, and outputs a pulse-per-second signal generated from the standard frequency signal closest to the reference signal.
Further, preferably, the time-frequency signal synthesis apparatus based on multi-source time-frequency signal fusion further includes:
and the data receiving and processing module 50 receives the data signals (data signals 1, 2, …, n) of each channel, fuses the data signals of each source, and generates a new data signal, wherein the data signal comprises the characteristics of the original source atomic clock, the time frequency signal transmission path and the important correction value.
In addition, preferably, the signal acquisition processing control module 30 further calculates the frequency stability of each channel frequency signal, and obtains a standard frequency signal by using a weighted average of a plurality of frequency signals meeting the frequency stability requirement, for example, the frequency stability of each channel frequency signal is calculated according to the international Allan variance.
In the time frequency signal synthesis device based on multi-source time frequency signal fusion, frequency signals (sine waves) output by each input channel and the crystal oscillator module are down-converted into low-frequency sine wave signals; the signal acquisition processing control module acquires low-frequency sine wave signals to obtain relative phases and changes of the sine wave signals of all channels, the relative phases and the changes of the sine wave signals are weighted and averaged to obtain a crystal oscillator control frequency phase value, and the low-noise D/A unit is used for controlling the frequency signals output by the crystal oscillator module to enable the frequency and the phase of the frequency signals output by the crystal oscillator module to be consistent with the frequency and phase weighted and averaged result of the input frequency signals.
Furthermore, it is preferable that the relative phases of the frequency signals input to the channels from the plurality of sources are consistent within a certain range (within 200 ps), but are not arbitrary, and if they are arbitrary, the time represented by the zero-crossing point of the sine wave is confused. The phase of the output standard frequency signal is also required to be consistent with the phase of the input frequency signal. The input frequency signals with relative phases beyond a certain range (within 200ps range) are subjected to error alarm processing, that is, the method further preferably comprises an alarm module, and the relative phases of the frequency signals input into each channel are not within 200ps range, so that an alarm signal is sent out.
Preferably, the rising edge position of the pulse per second signal input by each channel is aligned with the zero crossing position of the frequency signal input by the channel.
Preferably, a part of the channels for simultaneously inputting the plurality of frequency signals further inputs a digital status signal (digital status signal 1-n) corresponding to each frequency signal for indicating whether the frequency signal inputted by each channel is normal or abnormal.
According to the invention, the far end of the optical fiber single-channel time frequency high-precision transmission device transmits the time frequency signals to a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion,
specifically, the second crystal oscillator module at the far end of each optical fiber single-channel time frequency high-precision transmission device is connected with the down-conversion modules of a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables, the second pulse receiving and processing module at the far end of each optical fiber single-channel time frequency high-precision transmission device is connected with the second pulse processing modules of the plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables, so that the time frequency signals recovered by the far end of each optical fiber single-channel time frequency high-precision transmission device can be transmitted to all the time frequency signal synthesis devices based on multi-source time frequency signal fusion, and each time frequency signal synthesis device based on multi-source time frequency signal fusion can receive the time frequency signals recovered by the far ends of all the optical fiber single-channel time frequency high-precision transmission devices,
because the time frequency signals restored by the far ends of the optical fiber single-channel time frequency high-precision transmission devices are the same, the time frequency signals received by any one time frequency signal synthesis device based on multi-source time frequency signal fusion are the same, and the time frequency signals output by the time frequency signal synthesis devices based on multi-source time frequency signal fusion after fusion are still the same.
Because the time frequency signal synthesis device based on multi-source time frequency signal fusion receives time frequency signals from a plurality of sources, when a certain optical fiber or other equipment in the transmission unit breaks down, the normal output time frequency signals of the time frequency signal synthesis device based on multi-source time frequency signal fusion cannot be influenced.
In the invention, the transmission of the time frequency signal to the next transmission unit is realized by connecting the time frequency signal synthesis device based on multi-source time frequency signal fusion of the previous stage with the local end of the optical fiber single-channel time frequency high-precision transmission device of the next stage,
specifically, the crystal oscillator module 20 of each frequency signal synthesis device based on multi-source time frequency signal fusion of the previous stage transmission unit is respectively connected with the first down-conversion module of the local end of the multiple optical fiber single-channel time frequency high-precision transmission devices of the next stage transmission unit through a cable; the pulse per second processing module of each frequency signal synthesis device based on multi-source time frequency signal fusion of the upper stage transmission unit is respectively connected with the pulse per second sending processing module of the local end of the plurality of optical fiber single-channel time frequency high-precision transmission devices of the lower stage transmission unit,
through the link mode of the cable, the optical fiber single-channel time frequency high-precision transmission device of any one of the next-stage transmission units can receive the time frequency signal output by the frequency signal synthesis device of any one of the previous-stage transmission units based on multi-source time frequency signal fusion.
In the invention, when a certain transmission unit in the transmission system breaks down, the normal operation of the whole time frequency transmission system is not influenced, and meanwhile, the equipment can be replaced and maintained under the condition of not influencing the transmission of time frequency signals.
On the other hand, the invention also provides a method for transmitting the time frequency of the super-long-distance dual-fiber interconnected multistage optical fiber, which carries out cross transmission in different links of time frequency signal transmission by increasing the configuration number of devices and ensures the stable operation of a time frequency transmission system, and comprises the following processes:
1) establishing a transmission unit;
2) the local high-precision time frequency real-time comprehensive device is connected with the transmission unit;
3) and a plurality of transmission units are connected with each other.
The establishing and transferring unit comprises the following sub-processes:
11) the local end and the remote end of the multiple optical fiber single-channel time frequency high-precision transmission devices are respectively connected through the independent optical fibers, so that the local end and the remote end of each optical fiber single-channel time frequency high-precision transmission device can transmit time frequency signals.
12) Connecting a second crystal oscillator module at the far end of each optical fiber single-channel time frequency high-precision transmission device with down-conversion modules of a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables; and connecting the pulse-per-second receiving and processing module at the far end of each optical fiber single-channel time frequency high-precision transmission device with the pulse-per-second processing modules of the multiple time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables, so that the time frequency signals received by the multiple time frequency signal synthesis devices based on multi-source time frequency signal fusion are the same.
According to the connection method, the time frequency signals restored by the far end of each optical fiber single-channel time frequency high-precision transmission device can be transmitted to all the time frequency signal synthesis devices based on multi-source time frequency signal fusion, and each time frequency signal synthesis device based on multi-source time frequency signal fusion can receive the time frequency signals restored by the far end of each optical fiber single-channel time frequency high-precision transmission device.
The real-time integrated device of local high accuracy time frequency is connected with the transmission element, includes:
connecting a crystal oscillator unit of the local high-precision time-frequency real-time integrated device with a plurality of first down-conversion modules at the local end of the optical fiber single-channel time-frequency high-precision transmission device in a transmission unit through cables; the pulse per second generating unit of the local high-precision time frequency real-time integrated device is connected with the pulse per second sending and processing module at the local end of the multiple optical fiber single-channel time frequency high-precision transmission devices in the transmission unit through cables, so that time frequency signals received by the local end of the multiple optical fiber single-channel time frequency high-precision transmission devices are the same.
The transmission units are connected, the transmission unit connected with the local high-precision time-frequency real-time comprehensive device is used as a previous transmission unit, the newly-added transmission unit is used as a next transmission unit, and the process is repeated, so that the connection among the transmission units is completed.
Specifically, a crystal oscillator module 20 of each frequency signal synthesis device based on multi-source time frequency signal fusion of the previous stage transmission unit is respectively connected with a first down-conversion module at the local end of a plurality of optical fiber single-channel time frequency high-precision transmission devices of the next stage transmission unit through a cable; the pulse per second processing module of each frequency signal synthesis device based on multi-source time frequency signal fusion of the upper stage transmission unit is respectively connected with the pulse per second sending processing module of the local end of the plurality of optical fiber single-channel time frequency high-precision transmission devices of the lower stage transmission unit,
according to the connection method, any one optical fiber single-channel time frequency high-precision transmission device of the next-stage transmission unit can receive the time frequency signal output by any one frequency signal synthesis device based on multi-source time frequency signal fusion of the previous-stage transmission unit.
It should be noted that the processes described in the present invention are not in sequential order, and the ordering in the present invention is only for the purpose of clearer illustration.
In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", and the like indicate orientations or positional relationships based on operational states of the present invention, and are only used for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
Claims (2)
1. A method for transmitting time frequency of multi-stage optical fiber by ultra-long distance dual-fiber interconnection features that the configuration number of devices is increased, and the signals are transmitted in different links to make the time frequency transmission system stable in running,
the method comprises the following steps:
1) establishing a transmission unit;
2) the local high-precision time frequency real-time comprehensive device is connected with the transmission unit;
3) the plurality of transmission units are connected;
the transmission unit comprises a plurality of optical fiber single-channel time frequency high-precision transmission devices, a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion and optical fibers connected with the devices;
the establishing and transferring unit comprises the following sub-processes:
11) the local end and the remote end of the multiple optical fiber single-channel time frequency high-precision transmission devices are respectively connected through independent optical fibers, so that the local end and the remote end of each optical fiber single-channel time frequency high-precision transmission device can transmit time frequency signals;
12) connecting a second crystal oscillator module at the far end of each optical fiber single-channel time frequency high-precision transmission device with down-conversion modules of a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables; connecting a pulse-per-second receiving and processing module at the far end of each optical fiber single-channel time frequency high-precision transmission device with pulse-per-second processing modules of a plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion through cables, so that the time frequency signals received by the plurality of time frequency signal synthesis devices based on multi-source time frequency signal fusion are the same;
the real-time integrated device of local high accuracy time frequency is connected with the transmission element, includes:
connecting a crystal oscillator unit of the local high-precision time-frequency real-time integrated device with a plurality of first down-conversion modules at the local end of the optical fiber single-channel time-frequency high-precision transmission device in a transmission unit through cables; the pulse per second generating unit of the local high-precision time frequency real-time integrated device is connected with pulse per second sending and processing modules at the local end of a plurality of optical fiber single-channel time frequency high-precision transmission devices in the transmission unit through cables, so that time frequency signals received by the local end of the plurality of optical fiber single-channel time frequency high-precision transmission devices are the same;
the transmission units are connected, in order to take the transmission unit which is connected with the local high-precision time frequency real-time synthesis device as the upper-stage transmission unit and the newly-added transmission unit as the lower-stage transmission unit, the process is repeated,
the crystal oscillator module of each frequency signal synthesis device based on multi-source time frequency signal fusion of the upper stage transmission unit is respectively connected with the first down-conversion modules of the local ends of the multiple optical fiber single-channel time frequency high-precision transmission devices of the lower stage transmission unit through cables; and (3) connecting the pulse per second processing module of each frequency signal synthesis device based on multi-source time frequency signal fusion of the previous stage of transmission unit with the pulse per second sending processing module of the local end of the multiple optical fiber single-channel time frequency high-precision transmission devices of the next stage of transmission unit respectively.
2. The method of claim 1, wherein the step of transmitting the time frequency of the ultra-long-distance dual-fiber interconnected multi-stage optical fiber comprises,
the number of the plurality of the circuits is two, and the time frequency signals comprise frequency signals and pulse per second signals.
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