A time transfer system based on frequency domain slicing technique

Abstract

A time transfer system and method based on frequency domain slicing technology, the system comprises a near-end device, an intermediate download device, a remote-end device; the near-end device and the remote-end device comprise a bidirectional connector, a wideband signal generator S1, a wideband signal generator S2, a transmitter, a receiver, an analog-digital conversion and filtering unit F1, an analog-digital conversion and filtering unit F2, a signal processing unit; the intermediate download device comprises: a download device, a wideband signal generator S1, a wideband signal generator S2, a receiver, an analog-digital conversion and filtering unit F1, a signal processing unit. The method encodes time information from a local clock source into a wideband signal, one way is sent through the transmitter, and the other way is cut into multiple narrowband signals, the received signals are operated in the same way, the corresponding narrowband signals are respectively operated in the cross-correlation operation, and all the narrowband signal measurement results are averaged as the result of this measurement. The intermediate site can obtain the bidirectional transmission signal, and distributed time service is realized.

Description

Technical Field

[0001] This invention belongs to the field of time comparison and frequency calibration technology, and in particular to a time transfer system and method based on frequency domain cutting technology. Background Technology

[0002] Time is one of the seven international base units and is currently the most precise unit of measurement. Precise time and frequency standards are essential for modern scientific research and industrial systems. However, high-precision time and frequency standards are often bulky, complex, and expensive, typically operating only at national metrology centers. Therefore, high-precision time and frequency transfer is an important research topic.

[0003] Currently, the mainstream time synchronization technologies are satellite-based microwave time synchronization and laser time synchronization. These technologies are easily affected by factors such as atmospheric turbulence and ionospheric interference, thus limiting their accuracy to the nanosecond level. While laser-based time synchronization technology can achieve sub-picosecond accuracy, such systems often require the introduction of complex and expensive optical frequency combs, making large-scale application difficult. Summary of the Invention

[0004] This invention aims to solve the above-mentioned technical problems and proposes a time transfer system and method based on frequency domain cutting technology. The device includes a near-end device, an intermediate download device, and a far-end device connected through a transmission channel. It can improve the accuracy of microwave time synchronization technology and achieve high-precision laser time synchronization without using an optical frequency comb.

[0005] The near-end device includes a first bidirectional connector, a first S1 broadband signal generator, a first S2 broadband signal generator, a first transmitter, a first receiver, a second F2 analog-to-digital converter and filter unit, a first F2 analog-to-digital converter and filter unit, and a first signal processing unit. The first port of the first bidirectional connector is connected to the second port of the first transmitter, the second port is connected to the transmission channel, and the third port is connected to the first port of the first receiver. The first port of the first S1 broadband signal generator is an external time reference input port, and its second port is connected to the first port of the first transmitter. The first port of the first S2 broadband signal generator is an external time reference input port, and its second port is connected to the first port of the first F2 analog-to-digital converter and filter unit. The first port of the second F2 analog-to-digital converter and filter unit is connected to the second port of the first receiver, and its second port is connected to the second port of the first signal processing unit. The second port of the first F2 analog-to-digital converter and filter unit is connected to the first port of the first signal processing unit.

[0006] The remote device includes a second bidirectional connector, a second S1 broadband signal generator, a second S2 broadband signal generator, a second transmitter, a second receiver, a second F1 analog-to-digital converter and filter unit, a first F1 analog-to-digital converter and filter unit, and a second signal processing unit. The first port of the second bidirectional connector is connected to the second port of the second transmitter, the second port is connected to the transmission channel, and the third port is connected to the first port of the second receiver. The first port of the second S1 broadband signal generator is an external time reference input port, and its second port is connected to the first port of the second transmitter. The first port of the second S2 broadband signal generator is also an external time reference input port, and its second port is connected to the first port of the first F1 analog-to-digital converter and filter unit. The first port of the second F1 analog-to-digital converter and filter unit is connected to the second port of the second receiver, and its second port is connected to the second port of the second signal processing unit. The second port of the first F1 analog-to-digital converter and filter unit is connected to the first port of the second signal processing unit.

[0007] The intermediate download device includes a first download device, a third S1 broadband signal generator, a third S2 broadband signal generator, a third receiver, a fourth receiver, a third F1 analog-to-digital converter and filter unit, a third F2 analog-to-digital converter and filter unit, a third signal processing unit, a fourth signal processing unit, a fourth F1 analog-to-digital converter and filter unit, and a fourth F2 analog-to-digital converter and filter unit. The first port of the first download device is connected to the transmission channel for transmitting time information near the near-end device, the second port is connected to the transmission channel for transmitting time information near the far-end device, the third port is connected to the first port of the third receiver, and the fourth port is connected to the first port of the fourth receiver; the first port of the third S1 broadband signal generator is an external time reference input port, and the second port is connected to the first port of the fourth F1 analog-to-digital converter and filter unit; the first port of the third S2 broadband signal generator is an external time reference input port, and the second port is connected to the first port of the fourth F2 analog-to-digital converter and filter unit; the first port of the third F1 analog-to-digital converter and filter unit is connected to the second port of the third receiver, and the second port is connected to the first port of the third signal processing unit; the first port of the third F2 analog-to-digital converter and filter unit is connected to the second port of the fourth receiver, and the second port is connected to the first port of the fourth signal processing unit; the second port of the third signal processing unit is connected to the second port of the fourth F1 analog-to-digital converter and filter unit; and the second port of the fourth signal processing unit is connected to the second port of the fourth F2 analog-to-digital converter and filter unit.

[0008] The signal transmission of the first bidirectional connector and the second bidirectional connector is as follows:

[0009] When a signal enters from the first port of the first bidirectional connector and the first port of the second bidirectional connector, it is output from the second port of the first bidirectional connector and the second port of the second bidirectional connector.

[0010] When a signal is input from the second port, the signal is output from the third port.

[0011] The signal transmission of the first downloading device is as follows:

[0012] If a signal enters from the first port, the signal is output from the second and third ports; if a signal enters from the second port, the signal is output from the first and fourth ports.

[0013] The signal output from the fourth port has the same wavelength as the first transmitter in the near-end device; the signal output from the third port has the same wavelength as the second transmitter in the far-end device.

[0014] The first S1 broadband signal generator, the second S1 broadband signal generator, and the third S1 broadband signal generator can detect and generate the same broadband signal S1 based on the time information received from the first port, and output it from the second port.

[0015] The first, second, and third S2 broadband signal generators can detect the time information received at the first port, generate the same broadband signal S2, and output it from the second port. The broadband signals S1 and S2 can be the same signal or different signals.

[0016] The first F1 analog-to-digital converter and filter unit, the second F1 analog-to-digital converter and filter unit, the third F1 analog-to-digital converter and filter unit, and the fourth F1 digital-to-analog converter and filter unit can cut the input broadband signal S1 into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals.

[0017] The first F2 analog-to-digital converter and filter unit, the second F2 analog-to-digital converter and filter unit, the third F2 analog-to-digital converter and filter unit, and the fourth F2 digital-to-analog converter and filter unit can cut the input broadband signal S2 into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals.

[0018] The first signal processing unit, the second signal processing unit, the third signal processing unit, and the fourth signal processing unit are used to perform cross-correlation operations on the input signals, perform weighted operations on the cross-correlation results of signals of different frequencies, and obtain the time interval between the local S1 signal, S2 signal and the received S1 signal, S2 signal based on the operation results.

[0019] It can use amplifiers to extend the transmission distance and increase the number of intermediate download devices, thus allowing for multiple intermediate download devices.

[0020] The carrier wavelengths used by the first transmitter and the second transmitter can be the same or different.

[0021] A time transfer method based on frequency domain segmentation technology includes the following steps:

[0022] 1) The time signal output from the near-end clock source is processed by the S1 wideband signal generator and the S2 wideband signal generator to generate a wideband signal. The signal generated by the S1 wideband signal generator is modulated and sent to the other end. The signal generated by the S2 wideband signal generator is sent to the second F2 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. The wideband signal from the other end, after being converted by the receiver, is sent to the first F2 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. Several narrowband signals from the first F2 analog-to-digital converter and filter unit and several narrowband signals from the second F2 analog-to-digital converter and filter unit are sent to the signal processing unit. The delay between the corresponding narrowband signals is obtained by cross-correlation, and the delay between all narrowband signals is averaged as the result of local time comparison.

[0023] 2) The time signal output from the remote end's clock source is processed by the S1 and S2 wideband signal generators to generate wideband signals. The signal generated by the S2 wideband signal generator is modulated and sent to the remote end. The signal generated by the S1 wideband signal generator is sent to the second F1 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. The wideband signal from the remote end, after being converted by the receiver, is sent to the first F1 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. The several narrowband signals from the first F1 analog-to-digital converter and filter unit and the several narrowband signals from the second F1 analog-to-digital converter and filter unit are sent to the signal processing unit. The delay between the corresponding narrowband signals is obtained by cross-correlation, and the delay between all narrowband signals is averaged as the result of local time comparison.

[0024] 3) The bidirectional transmission signals can be downloaded to the intermediate download device, and the receiver recovers the broadband signal S1 from the near end and the broadband signal S2 from the far end station, respectively. The time signal from the local time reference is used to generate broadband signal S1 by the S1 broadband signal generator and broadband signal S2 by the S2 broadband signal generator. The two S1 signals are sent to the F1 analog-to-digital converter and filter unit (converted into several narrowband digital signals), and then sent to the signal processing unit. The corresponding narrowband signals are cross-correlated to obtain the delay between the corresponding narrowband signals, and the delay between all narrowband signals is averaged as the result of local time comparison. The two S2 signals are sent to the F1 analog-to-digital converter and filter unit to be converted into several narrowband digital signals, and then sent to the signal processing unit. The corresponding narrowband signals are cross-correlated to obtain the delay between the corresponding narrowband signals, and the delay between all narrowband signals is averaged as the result of local time comparison.

[0025] Compared with the prior art, the beneficial effects of the present invention

[0026] By employing frequency domain segmentation, a time signal can be processed multiple times, enabling high-precision microwave / laser time synchronization. Compared to traditional time synchronization systems based on optical frequency combs, this method has lower cost and complexity. Attached Figure Description

[0027] Figure 1 This is a structural diagram of a time transfer system based on frequency domain cutting technology according to the present invention.

[0028] Figure 2 This is a feasible schematic diagram of the operation of the analog-to-digital conversion and filtering unit of a time transfer system based on frequency domain cutting technology according to the present invention.

[0029] Figure 3 This is another feasible schematic diagram of the operation of the analog-to-digital conversion and filtering unit of a time transfer system based on frequency domain cutting technology according to the present invention.

[0030] Figure 4 This is a schematic diagram of a system embodiment of a time transfer system based on frequency domain cutting technology according to the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0032] In the description of this invention, it should be understood that the term 'near end' refers only to the endpoint where the time-frequency reference source is located, and is not a fixed endpoint. The terms 'wideband' and 'narrowband' refer only to the width of the relative frequency spectrum, and do not specifically refer to a spectrum that is wider or narrower than a particular frequency range.

[0033] The following description, in conjunction with the accompanying drawings, illustrates a time transfer system based on frequency domain segmentation technology according to the present invention.

[0034] Please refer to Figure 1 , Figure 1 This is a structural diagram of a time transfer system based on frequency domain segmentation technology according to the present invention. As can be seen from the diagram, the time transfer system based on frequency domain segmentation technology according to the present invention includes: a near-end device, an intermediate download device, and a far-end device connected through a transmission channel; it can achieve high-precision time synchronization.

[0035] The near-end device includes a first bidirectional connector, a first S1 broadband signal generator, a first S2 broadband signal generator, a first transmitter, a first receiver, a second F2 analog-to-digital converter and filter unit, a first F2 analog-to-digital converter and filter unit, and a first signal processing unit. The first port of the first bidirectional connector is connected to the second port of the first transmitter, the second port is connected to the transmission channel, and the third port is connected to the first port of the first receiver. The first port of the first S1 broadband signal generator is an external time reference input port, and its second port is connected to the first port of the first transmitter. The first port of the first S2 broadband signal generator is an external time reference input port, and its second port is connected to the first port of the first F2 analog-to-digital converter and filter unit. The first port of the second F2 analog-to-digital converter and filter unit is connected to the second port of the first receiver, and its second port is connected to the second port of the first signal processing unit. The second port of the first F2 analog-to-digital converter and filter unit is connected to the first port of the first signal processing unit.

[0036] The remote device includes a second bidirectional connector, a second S1 broadband signal generator, a second S2 broadband signal generator, a second transmitter, a second receiver, a second F1 analog-to-digital converter and filter unit, a first F1 analog-to-digital converter and filter unit, and a second signal processing unit. The first port of the second bidirectional connector is connected to the second port of the second transmitter, the second port is connected to the transmission channel, and the third port is connected to the first port of the second receiver. The first port of the second S1 broadband signal generator is an external time reference input port, and its second port is connected to the first port of the second transmitter. The first port of the second S2 broadband signal generator is also an external time reference input port, and its second port is connected to the first port of the first F1 analog-to-digital converter and filter unit. The first port of the second F1 analog-to-digital converter and filter unit is connected to the second port of the second receiver, and its second port is connected to the second port of the second signal processing unit. The second port of the first F1 analog-to-digital converter and filter unit is connected to the first port of the second signal processing unit.

[0037] The intermediate download device includes a first download device, a third S1 broadband signal generator, a third S2 broadband signal generator, a third receiver, a fourth receiver, a third F1 analog-to-digital converter and filter unit, a third F2 analog-to-digital converter and filter unit, a third signal processing unit, a fourth signal processing unit, a fourth F1 analog-to-digital converter and filter unit, and a fourth F2 analog-to-digital converter and filter unit. The first port of the first download device is connected to the transmission channel for transmitting time information near the near-end device, the second port is connected to the transmission channel for transmitting time information near the far-end device, the third port is connected to the first port of the third receiver, and the fourth port is connected to the first port of the fourth receiver; the first port of the third S1 broadband signal generator is an external time reference input port, and the second port is connected to the first port of the fourth F1 analog-to-digital converter and filter unit; the first port of the third S2 broadband signal generator is an external time reference input port, and the second port is connected to the first port of the fourth F2 analog-to-digital converter and filter unit; the first port of the third F1 analog-to-digital converter and filter unit is connected to the second port of the third receiver, and the second port is connected to the first port of the third signal processing unit; the first port of the third F2 analog-to-digital converter and filter unit is connected to the second port of the fourth receiver, and the second port is connected to the first port of the fourth signal processing unit; the second port of the third signal processing unit is connected to the second port of the fourth F1 analog-to-digital converter and filter unit; and the second port of the fourth signal processing unit is connected to the second port of the fourth F2 analog-to-digital converter and filter unit.

[0038] The signal transmission of the first bidirectional connector and the second bidirectional connector is as follows:

[0039] When a signal enters from the first port of the first bidirectional connector and the first port of the second bidirectional connector, it is output from the second port of the first bidirectional connector and the second port of the second bidirectional connector.

[0040] When a signal is input from the second port, the signal is output from the third port.

[0041] The signal transmission of the first downloading device is as follows:

[0042] If a signal enters from the first port, the signal is output from the second and third ports; if a signal enters from the second port, the signal is output from the first and fourth ports.

[0043] The first S1 broadband signal generator, the second S1 broadband signal generator, and the third S1 broadband signal generator can detect and generate the same broadband signal S1 based on the time information received from the first port, and output it from the second port.

[0044] The first, second, and third S2 broadband signal generators can detect the time information received at the first port, generate the same broadband signal S2, and output it from the second port. The broadband signals S1 and S2 can be the same signal or different signals.

[0045] The first F1 analog-to-digital converter and filter unit, the second F1 analog-to-digital converter and filter unit, the third F1 analog-to-digital converter and filter unit, and the fourth F1 digital-to-analog converter and filter unit can cut the input broadband signal S1 into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals.

[0046] The first F2 analog-to-digital converter and filter unit, the second F2 analog-to-digital converter and filter unit, the third F2 analog-to-digital converter and filter unit, and the fourth F2 digital-to-analog converter and filter unit can cut the input broadband signal S2 into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals.

[0047] The first signal processing unit, the second signal processing unit, the third signal processing unit, and the fourth signal processing unit are used to perform cross-correlation operations on the input signals, perform weighted operations on the cross-correlation results of signals of different frequencies, and obtain the time interval between the local S1 signal, S2 signal and the received S1 signal, S2 signal based on the operation results.

[0048] It can use amplifiers to extend the transmission distance and increase the number of intermediate download devices, thus allowing for multiple intermediate download devices.

[0049] The carrier wavelengths used by the first transmitter and the second transmitter can be the same or different.

[0050] A time transfer method based on frequency domain segmentation technology includes the following steps:

[0051] 1) The time signal output from the near-end clock source is processed by the S1 wideband signal generator and the S2 wideband signal generator to generate a wideband signal. The signal generated by the S1 wideband signal generator is modulated and sent to the other end. The signal generated by the S2 wideband signal generator is sent to the second F2 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. The wideband signal from the other end, after being converted by the receiver, is sent to the first F2 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. Several narrowband signals from the first F2 analog-to-digital converter and filter unit and several narrowband signals from the second F2 analog-to-digital converter and filter unit are sent to the signal processing unit. The delay between the corresponding narrowband signals is obtained by cross-correlation, and the delay between all narrowband signals is averaged as the result of local time comparison.

[0052] 2) The time signal output from the remote end's clock source is processed by the S1 and S2 wideband signal generators to generate wideband signals. The signal generated by the S2 wideband signal generator is modulated and sent to the remote end. The signal generated by the S1 wideband signal generator is sent to the second F1 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. The wideband signal from the remote end, after being converted by the receiver, is sent to the first F1 analog-to-digital converter and filter unit to be converted into several narrowband digital signals. The several narrowband signals from the first F1 analog-to-digital converter and filter unit and the several narrowband signals from the second F1 analog-to-digital converter and filter unit are sent to the signal processing unit. The delay between the corresponding narrowband signals is obtained by cross-correlation, and the delay between all narrowband signals is averaged as the result of local time comparison.

[0053] 3) The bidirectional transmission signals can be downloaded to the intermediate download device, and the receiver recovers the broadband signal S1 from the near end and the broadband signal S2 from the far end station, respectively. The time signal from the local time reference is used to generate broadband signal S1 through the S1 broadband signal generator and broadband signal S2 through the S2 broadband signal generator. The two S1 signals are sent to the F1 analog-to-digital converter and filter unit, where they are converted into several narrowband digital signals and sent to the signal processing unit. The corresponding narrowband signals are cross-correlated to obtain the delay between them, and the delay between all narrowband signals is averaged as the result of local time comparison. The two S2 signals are sent to the F1 analog-to-digital converter and filter unit, where they are converted into several narrowband digital signals and sent to the signal processing unit. The corresponding narrowband signals are cross-correlated to obtain the delay between them, and the delay between all narrowband signals is averaged as the result of local time comparison.

[0054] Figure 2 This invention presents a feasible schematic diagram of the analog-to-digital conversion and filtering unit of a time transfer system based on frequency domain slicing technology. First, a broadband analog signal is converted into a digital signal, and then digital filtering is applied to achieve the output of multiple narrowband digital signals.

[0055] Figure 3 This invention presents a feasible schematic diagram of the analog-to-digital conversion and filtering unit of a time transfer system based on frequency domain slicing technology. First, the broadband analog signal is divided into several paths, and several narrowband signals are extracted using narrowband filters. Then, an analog-to-digital converter converts the different analog narrowband signals into digital signals, achieving the output of multiple narrowband signal digital quantities.

[0056] Then, in the signal processing unit, cross-correlation is performed on the corresponding narrowband signal and the peak position of the cross-correlation function is extracted and converted into the time difference between the two function inputs.

[0057] The correlated signal can be a chirped signal, a pseudo-random code signal, etc. Let the two cross-correlated signals be g1(t) and g2(t). Since the two signals are correlated, they have the following characteristics:

[0058] g2(t)=g1(t-Δt)

[0059] Performing a Fourier transform on it yields:

[0060] G2(w)=G1(w)e -2πi(uΔt)

[0061] Furthermore, based on the calculation method of the cross-correlation function, we know that:

[0062] R ccf (t)=g1(t)*g2(t)

[0063] Combining the convolution theorem, we can obtain:

[0064]

[0065] in By performing an inverse Fourier transform, we can obtain

[0066] R(t)=F(t)*δ(t-Δt)=F(t-Δt)

[0067] As can be seen from the properties of autocorrelation, the peak of the F(t) function appears at the origin, and the peak of the R(t) function appears at Δt, which is the offset between g1(t) and g2(t).

[0068] Then, the time differences extracted from all narrowband signals are weighted and calculated to achieve a single high-precision time interval measurement.

[0069] A schematic diagram of an embodiment of the time transfer system based on frequency domain segmentation technology of the present invention is shown below. Figure 4As shown, the external reference at the near-end station inputs time information to two identical chirped signal generators with a center frequency of f to generate broadband signals. One signal is input to an analog-to-digital converter (ADC) and digitally filtered, splitting it into 10 narrowband signals, which are then sent to the computer. The other broadband signal is modulated onto a wavelength 1 optical carrier by an optical transmitter and transmitted to the optical fiber via a wavelength division multiplexing (WDM) device. At the intermediate download device, the wavelength 1 signal is filtered out by the WDM device and received by the receiver. The ADC samples and converts it into a digital signal, which is then split into 10 narrowband signals by the same digital filter as in the near-end device. The digital signal is sent to the computer and cross-correlated with a locally generated signal with a center frequency of f1. After passing through the same ADC and digital filter, the signals are cross-correlated in the computer's signal processing unit and converted into the input time difference of the 20 narrowband signals. These 10 time differences are averaged to obtain the input time delay difference between the two broadband signals. A similar process is used at the far-end station to obtain the input time difference between the two signals. At the remote site, time information is input to two identical chirped signal generators with a center frequency of f to generate broadband signals. One signal is input to an analog-to-digital converter (ADC) and digitally filtered, splitting it into 10 narrowband signals, which are then sent to a computer. The other broadband signal is modulated onto a wavelength 2 optical carrier by an optical transmitter and transmitted into the optical fiber via a wavelength division multiplexing (WDM) device. At the intermediate download station, the wavelength 2 signal is filtered out using a WDM device. The intermediate download station obtains the input time difference between the two signals through a similar process.

Claims

1. A time transfer system based on frequency domain segmentation, characterized in that, include: A near-end device, at least one intermediate download device, and a remote device connected via a transmission channel; The near-end device includes a first bidirectional connector (a1), a first S1 broadband signal generator (a2), a first S2 broadband signal generator (a3), a first transmitter (a4), a first receiver (a5), a second F2 analog-to-digital converter and filter unit (a6), a first F2 analog-to-digital converter and filter unit (a7), and a first signal processing unit (a8). The first port (a1-1) of the first bidirectional connector (a1) is connected to the second port (a4-2) of the first transmitter (a4), the second port (a1-2) is connected to the transmission channel, and the third port (a1-3) is connected to the first port (a5-1) of the first receiver (a5). The first port (a2-1) of the first S1 broadband signal generator (a2) is an external time reference input port. The second port (a2-2) is connected to the first port (a4-1) of the first transmitter (a4); the first port (a3-1) of the first S2 broadband signal generator (a3) ​​is an external time reference input port, and the second port (a3-2) is connected to the first port (a7-1) of the first F2 analog-to-digital converter and filter unit (a7); the first port (a6-1) of the second F2 analog-to-digital converter and filter unit (a6) is connected to the second port (a5-2) of the first receiver, and the second port (a6-2) is connected to the second port (a8-2) of the first signal processing unit (a8); the second port (a7-2) of the first F2 analog-to-digital converter and filter unit (a7) is connected to the first port (a8-1) of the first signal processing unit (a8); The remote device includes a second bidirectional connector (b1), a second S1 broadband signal generator (b2), a second S2 broadband signal generator (b3), a second transmitter (b4), a second receiver (b5), a second F1 analog-to-digital converter and filter unit (b6), a first F1 analog-to-digital converter and filter unit (b7), and a second signal processing unit (b8). The first port (b1-1) of the second bidirectional connector (b1) is connected to the second port (b4-2) of the second transmitter (b4), the second port (b1-2) is connected to the transmission channel, and the third port (b1-3) is connected to the first port (b5-1) of the second receiver (b5). The first port (b2-1) of the second S1 broadband signal generator (b2) is an external time reference input port. The second port (b2-2) is connected to the first port (b4-1) of the second transmitter (b4); the first port (b3-1) of the second S2 broadband signal generator (b3) is an external time reference input port, and the second port (b3-2) is connected to the first port (b7-1) of the first F1 analog-to-digital converter and filter unit (b7); the first port (b6-1) of the second F1 analog-to-digital converter and filter unit (b6) is connected to the second port (b5-2) of the second receiver, and the second port (b6-2) is connected to the second port (b8-2) of the second signal processing unit (b8); the second port (b7-2) of the first F1 analog-to-digital converter and filter unit (b7) is connected to the first port (b8-1) of the second signal processing unit (b8); The intermediate download device includes a first download device (c1), a third S1 broadband signal generator (c2), a third S2 broadband signal generator (c3), a third receiver (c4), a fourth receiver (c5), a third F1 analog-to-digital converter and filter unit (c6), a third F2 analog-to-digital converter and filter unit (c7), a third signal processing unit (c8), a fourth signal processing unit (c9), a fourth F1 analog-to-digital converter and filter unit (c10), and a fourth F2 analog-to-digital converter and filter unit (c11); the first port (c1-1) of the first download device (c1) is close to... The second port (c1-2) is connected to the transmission channel for transmitting time information of the terminal device, the third port (c1-3) is connected to the first port (c4-1) of the third receiver (c4), and the fourth port (c1-4) is connected to the first port (c5-1) of the fourth receiver (c5). The first port (c2-1) of the third S1 broadband signal generator (c2) is an external time reference input port, and the second port (c2-2) is connected to the first port (c10) of the fourth F1 analog-to-digital conversion and filtering unit (c10). -1) connected; the first port (c3-1) of the third S2 broadband signal generator (c3) is an external time reference input port, and the second port (c3-2) is connected to the first port (c11-1) of the fourth F2 analog-to-digital converter and filter unit (c11); the first port (c6-1) of the third F1 analog-to-digital converter and filter unit (c6) is connected to the second port (c4-2) of the third receiver (c4), and the second port (c6-2) is connected to the first port (c8-1) of the third signal processing unit (c8); the third F2 analog-to-digital converter and filter unit The first port (c7-1) of (c7) is connected to the second port (c5-2) of the fourth receiver (c5), and the second port (c7-2) is connected to the first port (c9-1) of the fourth signal processing unit (c9); the second port (c8-2) of the third signal processing unit (c8) is connected to the second port (c10-2) of the fourth F1 analog-to-digital converter and filter unit (c10); the second port (c9-2) of the fourth signal processing unit (c9) is connected to the second port (c11-2) of the fourth F2 analog-to-digital converter and filter unit (c11). The first S1 broadband signal generator (a2), the second S1 broadband signal generator (b2), and the third S1 broadband signal generator (c2) are used to generate the same broadband signal S1 according to an external time reference; the first S2 broadband signal generator (a3), the second S2 broadband signal generator (b3), and the third S2 broadband signal generator (c3) are used to generate the same broadband signal S2 according to an external time reference. The signal generated by the first S1 broadband signal generator (a2) is modulated and then sent to the other end; The signal generated by the first S2 broadband signal generator (a3) ​​is sent to the first F2 analog-to-digital conversion and filtering unit (a7). The first F2 analog-to-digital converter and filter unit (a7) is used to cut the local broadband signal into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals; The second F2 analog-to-digital converter and filter unit (a6) is used to cut the wideband signal at the other end into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals; The first signal processing unit (a8) is used to receive narrowband digital signals from the first F2 analog-to-digital conversion and filtering unit (a7) and the second F2 analog-to-digital conversion and filtering unit (a6), obtain the delay between the corresponding narrowband signals by cross-correlation of the corresponding narrowband signals, and average the delay between all narrowband signals as the result of local time comparison. The signal generated by the second S1 broadband signal generator (b2) is modulated and then sent to the other end; The signal generated by the second S2 broadband signal generator (b3) is sent to the first F1 analog-to-digital conversion and filtering unit (b7). The first F1 analog-to-digital converter and filter unit (b7) is used to cut the local broadband signal into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals; The second F1 analog-to-digital converter and filter unit (b6) is used to cut the wideband signal at the other end into several narrowband signals in the frequency domain and output the digital quantities corresponding to these narrowband signals; The second signal processing unit (b8) is used to receive narrowband digital signals from the first F1 analog-to-digital conversion and filtering unit (b7) and the second F1 analog-to-digital conversion and filtering unit (b6), obtain the delay between the corresponding narrowband signals by cross-correlation of the corresponding narrowband signals, and average the delay between all narrowband signals as the result of local time comparison. The first bidirectional connector (a1) is used to realize bidirectional optical communication; The second bidirectional connector (b1) is used to realize bidirectional optical communication; The first receiver (a5) is used to convert optical signals from a remote device into electrical signals; The second receiver (b5) is used to convert optical signals from the near-end device into electrical signals; The third receiver (c4) is used to convert optical signals from the remote device into electrical signals; The fourth receiver (c5) is used to convert the optical signal from the near-end device into an electrical signal; The third F2 analog-to-digital converter and filter unit (c7) and the fourth F2 analog-to-digital converter and filter unit (c11) are used to convert the analog broadband signal S2 into several narrowband digital signals; The third F1 analog-to-digital converter and filter unit (c6) and the fourth F1 analog-to-digital converter and filter unit (c10) are used to convert the analog broadband signal S1 into several narrowband digital signals. The third signal processing unit (c8) is used to perform cross-correlation on the corresponding narrowband signals to obtain the delay between the corresponding narrowband signals, and to average the delay between all narrowband signals as the result of local time comparison. The fourth signal processing unit (c9) is used to perform cross-correlation on the corresponding narrowband signals to obtain the delay between the corresponding narrowband signals, and to average the delay between all narrowband signals as the result of local time comparison.

2. The time transfer system based on frequency domain segmentation according to claim 1, characterized in that, The signal transmission of the first bidirectional connector (a1) and the second bidirectional connector (b1) is as follows: When a signal enters from the first port (a1-1) of the first bidirectional connector (a1) and the first port (b1-1) of the second bidirectional connector (b1), it is output from the second port (a1-2) of the first bidirectional connector (a1) and the second port (b1-2) of the second bidirectional connector (b1). When a signal is input from the second port (a1-2, b1-2), the signal is output from the corresponding third port (a1-3, b1-3).

3. The time transfer system based on frequency domain segmentation according to claim 1, characterized in that, The signal transmission of the intermediate download device (c1) is as follows: If the signal enters from the first port (c1-1), the signal will be output from the second port (c1-2) and the third port (c1-3); If the signal is input from the second port (c1-2), the signal is output from the first port (c1-1) and the fourth port (c1-4).

4. The time transfer system based on frequency domain segmentation according to claim 1, characterized in that, The first S1 broadband signal generator (a2), the second S1 broadband signal generator (b2), and the third S1 broadband signal generator (c2) generate the same broadband signal S1 and output it from the corresponding second port (a2-2, b2-2, c2-2).

5. The time transfer system based on frequency domain segmentation according to claim 1, characterized in that, The first S2 broadband signal generator (a3), the second S2 broadband signal generator (b3), and the third S2 broadband signal generator (c3) detect the time information received from the first port (a3-1, b3-1, c3-1), generate the same broadband signal S2, and output it from the corresponding second port (a3-2, b3-2, c3-2).

6. The time transfer system based on frequency domain segmentation according to claim 1, characterized in that, The first signal processing unit (a8), the second signal processing unit (b8), the third signal processing unit (c8), and the fourth signal processing unit (c9) are used to perform cross-correlation operations on the input signals, perform weighted operations on the cross-correlation results of signals of different frequencies, and obtain the time interval between the local S1 signal, S2 signal and the received S1 signal, S2 signal based on the operation results.

7. The time transfer system based on frequency domain segmentation according to claim 1, characterized in that, There are multiple intermediate download devices, which are arranged between the near-end device and the far-end device.

8. The time transfer system based on frequency domain segmentation according to claim 1, characterized in that, The first transmitter (a4) and the second transmitter (b4) use the same or different carrier wavelengths.

9. A time transfer method for a time transfer system based on frequency domain segmentation as described in any one of claims 1-8, characterized in that, The method includes the following steps: Step 1. The time signal output from the clock source of the near-end device is processed by the first S1 wideband signal generator (a2) and the first S2 wideband signal generator (a3) ​​to generate a wideband signal. The signal generated by the first S1 wideband signal generator (a2) is modulated and sent to the other end. The signal generated by the first S2 wideband signal generator (a3) ​​is sent to the first F2 analog-to-digital converter and filter unit (a7) to be converted into several narrowband digital signals. The wideband signal from the other end converted by the first receiver (a5) is sent to the second F2 analog-to-digital converter and filter unit (a6) to be converted into several narrowband digital signals. The several narrowband signals from the second F2 analog-to-digital converter and filter unit (a6) and the several narrowband signals from the first F2 analog-to-digital converter and filter unit (a7) are sent to the first signal processing unit (a8). The delay between the corresponding narrowband signals is obtained by cross-correlation of the corresponding narrowband signals, and the delay between all narrowband signals is averaged as the result of local time comparison. Step 2. The time signal output from the clock source of the remote device is processed by the second S1 wideband signal generator (b2) and the second S2 wideband signal generator (b3) to generate a wideband signal. The signal generated by the second S1 wideband signal generator (b2) is modulated and sent to the other end. The signal generated by the second S2 wideband signal generator (b3) is sent to the first F1 analog-to-digital converter and filter unit (b7) to be converted into several narrowband digital signals. The wideband signal from the other end converted by the second receiver (b5) is sent to the second F1 analog-to-digital converter and filter unit (b6) to be converted into several narrowband digital signals. The several narrowband signals from the second F1 analog-to-digital converter and filter unit (b6) and the several narrowband signals from the first F1 analog-to-digital converter and filter unit (b7) are sent to the second signal processing unit (b8). The delay between the corresponding narrowband signals is obtained by cross-correlation of the corresponding narrowband signals, and the delay between all narrowband signals is averaged as the result of local time comparison. Step 3. Download the bidirectional transmission signal at the intermediate download device. The broadband signal S1 from the near-end device is recovered by the third receiver (c4), and the broadband signal S2 from the far-end device is recovered by the fourth receiver (c5). The local time reference signal is used to generate broadband signal S1 via the third S1 broadband signal generator (c2), and broadband signal S2 via the third S2 broadband signal generator (c3). The recovered broadband signal S1 and the local broadband signal S1 are sent to the third F1 analog-to-digital converter and filter unit (c6) and the fourth F1 analog-to-digital converter and filter unit (c10) to be converted into several narrowband digital signals, and then sent to the third signal... The first processing unit (c8) obtains the delay between the corresponding narrowband signals by cross-correlation of the corresponding narrowband signals, and averages the delay between all narrowband signals as the result of local time comparison; the recovered wideband signal S2 and the local wideband signal S2 are respectively sent to the third F2 analog-to-digital conversion and filtering unit (c7) and the fourth F2 analog-to-digital conversion and filtering unit (c11) to be converted into several narrowband digital signals, and sent to the fourth signal processing unit (c9) to obtain the delay between the corresponding narrowband signals by cross-correlation of the corresponding narrowband signals, and averages the delay between all narrowband signals as the result of local time comparison.

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