Time synchronization method and equipment

Abstract

The invention provides a time synchronization method and equipment, and relates to the field of communication. The method and the device are used for realizing accurate clock synchronization under the condition that optical fibers are asymmetric. The method comprises the steps that the optical fiber length L and the absolute transmission delay D2 are determined according to the relative transmission delay difference D1 of a first optical signal and a second optical signal, the first optical signal and the second optical signal are optical signals sent by a first optical network device to a second optical network device through the same optical fiber in the same direction, and the first optical signal and the second optical signal are different in wavelength; determining a clock skew T between the first optical network equipment and the second optical network equipment according to the optical fiber length L and the absolute transmission delay D2; and performing clock synchronization on the first optical network equipment and the second optical network equipment according to the clock skew T.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of communication technology, and in particular, to a time synchronization method and device. Background Art

[0002] The communication network needs to synchronize the signal time when communicating. The signal time synchronization between two base stations can be achieved through the satellite network. The signal time synchronization can also be achieved through the bearer network. The base station transmits time information through network messages to synchronize the base station with the time server in the network.

[0003] Among the time synchronization schemes for signals implemented through bearer networks, 1588 hop-by-hop time synchronization is one of the implementation schemes for network clocks. It can be applied to Ethernet transmission networking. Network devices can exchange 1588V2 messages, calculate time and frequency offsets through precise timestamps, and implement frequency and time synchronization between network devices.

[0004] However, when the communication link between two devices is optical fiber, the different lengths of the transmitting and receiving optical fibers will cause asymmetric delays, resulting in clock synchronization deviations, which will affect the accuracy of time synchronization. Summary of the invention

[0005] The embodiments of the present application provide a time synchronization method and device, which can achieve accurate time synchronization in the case of optical fiber asymmetry.

[0006] In a first aspect, an embodiment of the present application provides a time synchronization method, the method comprising: determining an optical fiber length L and an absolute transmission delay D2 based on a relative transmission delay difference D1 between a first optical signal and a second optical signal, wherein the first optical signal and the second optical signal are optical signals sent by a first optical network device to a second optical network device through the same optical fiber in the same direction, and the first optical signal and the second optical signal have different wavelengths; determining a clock deviation T between the first optical network device and the second optical network device based on the optical fiber length L and the absolute transmission delay D2; and performing clock synchronization on the first optical network device and the second optical network device based on the clock deviation T.

[0007] In this possible implementation, the fiber length and absolute delay are calculated based on the relative transmission delay difference of two optical signals with different wavelengths, and then the time deviation between the two devices is calculated, thereby achieving synchronization between the two devices. This solves the problem of clock synchronization error caused by fiber asynchrony, is insensitive to the measurement accuracy of the dispersion coefficient and the speed of light in the optical fiber, has high accuracy and is easy to implement.

[0008] In a possible implementation, the above-mentioned determination of the optical fiber length L and the absolute transmission delay D2 based on the relative transmission delay difference D1 between the first optical signal and the second optical signal includes: determining the relative transmission delay difference D1 based on the first transmission time S1 of the first optical signal and the second transmission time S2 of the second optical signal; determining the optical fiber length L between the first optical network device and the second optical network device based on the transmission delay difference D1, a delay coefficient k1 related to the wavelength of the first optical signal, and a delay coefficient k2 related to the wavelength of the second optical signal; determining the absolute transmission delay D2 from the first optical network device to the second optical network device based on the optical fiber length L, the speed of light v in the optical fiber, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal.

[0009] In a possible implementation, the first optical network device includes a first optical module, the second optical network device includes a second optical module, the real-time clock frequencies of the first optical module and the second optical module are synchronized, and the reference clock of the second optical module is a clock data recovery (CDR) recovery clock.

[0010] In a possible implementation, the first optical network device includes a first optical module and a third optical module, the second optical network device includes a second optical module and a fourth optical module, the first optical signal is an optical signal sent by the first optical module to the second optical module, the second optical signal is an optical signal sent by the third optical module to the fourth optical module, the first optical module and the third optical module share a real-time clock, the second optical module and the fourth optical module share a real-time clock, and the reference clocks of the second optical module and the fourth optical module are CDR recovery clocks.

[0011] In this possible implementation, the reference clock of the transmitting optical module is also the clock source of the receiving optical module, so that the frequency synchronization of the devices at both ends is achieved, and the synchronization of the transmitting and receiving frequencies is simply achieved.

[0012] In a possible implementation manner, the light sources of the first optical signal and the second optical signal are optical frequency comb light sources.

[0013] In this possible implementation, an optical frequency comb is used as a laser source to avoid synchronization errors caused by common mode noise such as laser wavelength and error, thereby improving the accuracy of the time synchronization method provided in the embodiment of the present application.

[0014] In a possible implementation, before determining the relative transmission delay difference D1 according to the first transmission time S1 of the first optical signal and the second transmission time S2 of the second optical signal, the method further includes: determining the first transmission time S1 of the first optical signal and the second transmission time S2 of the second optical signal by coherent optical detection.

[0015] In this possible implementation, the first transmission time S1 and the second transmission time S2 are determined by coherent detection, and the optical frequency comb is used as a laser source to avoid synchronization errors between the first optical signal and the second optical signal due to frequency deviation and phase deviation, thereby improving the accuracy of time synchronization.

[0016] In a second aspect, an embodiment of the present application provides an optical network device, including: a processor and a memory. The processor is coupled to the memory; the memory is used to store computer instructions, and the computer instructions are loaded and executed by the processor to enable the optical network device to implement any one of the methods provided in the first aspect.

[0017] In a third aspect, an embodiment of the present application provides a chip, comprising: a processor and an interface circuit; the interface circuit is used to receive code instructions and transmit them to the processor; the processor is used to run the code instructions to execute any one of the methods provided in the first aspect.

[0018] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, in which at least one computer program instruction is stored, and the computer program instruction is loaded and executed by a processor to implement any one of the methods provided in the first aspect above.

[0019] In a fifth aspect, an embodiment of the present application provides a computer program product, including computer execution instructions, which, when executed on a computer, enable the computer to execute any one of the methods provided in the first aspect.

[0020] The technical effects brought about by any implementation method in the second to fifth aspects can refer to the technical effects brought about by the corresponding implementation methods in the first and second aspects, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the slope of dispersion and transmission delay;

[0022] Figure 2 A schematic diagram of a scenario of a global navigation satellite system signal time synchronization solution;

[0023] Figure 3 A schematic diagram of a scenario of a bearer network signal time synchronization solution;

[0024] Figure 4 A schematic diagram of a 1588 hop-by-hop time synchronization solution;

[0025] Figure 5 A schematic diagram of a 1588 transparent transmission time synchronization solution;

[0026] Figure 6A schematic diagram of a signal transmission scenario of an asymmetric optical fiber;

[0027] Figure 7 A schematic diagram of a scenario of optical signal transmission;

[0028] Figure 8 A schematic diagram of the architecture of a communication system provided in an embodiment of the present application;

[0029] Fig. 9 A schematic diagram of a time synchronization method provided in an embodiment of the present application;

[0030] Fig.10 A schematic diagram of a time synchronization method provided in an embodiment of the present application;

[0031] Fig.11 A schematic diagram of a scenario of optical signal transmission provided in an embodiment of the present application

[0032] Fig.12 A schematic diagram of another time synchronization method provided in an embodiment of the present application;

[0033] Fig.13 A schematic diagram of another optical signal transmission scenario provided in an embodiment of the present application;

[0034] Fig.14 A schematic diagram of a scenario of generating an optical frequency comb provided in an embodiment of the present application;

[0035] Fig.15 A schematic diagram of a CDR loop scenario provided in an embodiment of the present application;

[0036] Fig.16 A schematic diagram of the structure of an optical network device provided in an embodiment of the present application;

[0037] Fig.17 A schematic diagram of the structure of another optical network device provided in an embodiment of the present application;

[0038] Fig.18 A schematic diagram of the structure of a communication system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] In the description of this application, unless otherwise specified, " / " indicates that the objects associated with each other are in an "or" relationship, for example, A / B can represent A or B; "and / or" in this application is merely a description of the association relationship between associated objects, indicating that three relationships may exist, for example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural.

[0040] In the description of this application, unless otherwise specified, "plurality" means two or more than two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0041] In addition, in order to clearly describe the technical solutions of the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish the same items or similar items with substantially the same functions and effects. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit the difference.

[0042] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0043] It is understood that the "embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, the various embodiments in the entire specification do not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It is understood that in various embodiments of the present application, the size of the sequence number of each process does not mean the order of execution, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0044] It can be understood that some optional features in the embodiments of the present application may be implemented independently in certain scenarios without relying on other features, such as the solution on which they are currently based, to solve corresponding technical problems and achieve corresponding effects, or may be combined with other features according to needs in certain scenarios. Accordingly, the devices provided in the embodiments of the present application may also realize these features or functions accordingly, which will not be elaborated here.

[0045] In this application, unless otherwise specified, the same or similar parts between the various embodiments can refer to each other. In this application, if there is no special description or logical conflict between the various embodiments, the terms and / or descriptions between different embodiments are consistent and can be referenced to each other, and different embodiments can be combined to form new embodiments according to their inherent logical relationships. The following implementation methods of this application do not constitute a limitation on the scope of protection of this application.

[0046] In order to facilitate understanding of the technical solutions of the embodiments of the present application, a brief introduction to the relevant technologies of the embodiments of the present application is given below:

[0047] First, wavelength delay.

[0048] When optical signals of different wavelengths are transmitted in optical fibers, the difference in wavelength will cause a difference in the delay of the optical signals. For example, for optical signals of wavelength λ1 and wavelength λ2, the wavelength delay of the optical signal K = K3*(λ-M)3+K2*(λ-M)2+K1*(λ-M)+K0, where λ is the wavelength, K3, K2, K1, K0 and M are all optical fiber related parameters, and the difference in the wavelength delay of the optical signal of λ1 and the optical signal of wavelength λ2 can be realized by the above calculation method of calculating the wavelength delay K.

[0049] Second, dispersion and transmission delay.

[0050] like Figure 1 As shown, for G.652 type optical fiber, the slope of the oblique line is the dispersion slope of the optical fiber, k = 0.093ps / (nm2*km). Figure 1 It can be seen that for an optical signal with a wavelength of 1550nm, D = 0.093λ-124.15. According to the relationship between dispersion and transmission delay, the transmission delay difference △t can be obtained:

[0051]

[0052] For example, if the optical fiber length L = 1 km, λ1 = 1310 nm, λ2 = 1550 nm, then △t = 2.1216 ns, that is, the transmission delay difference is 2.1216 ns per kilometer.

[0053] Communication networks need to synchronize signals during communication. Different wireless standards have different requirements for signal synchronization. Figure 2 As shown, the base station can be synchronized through the global navigation satellite system (GNSS), and the time synchronization of the signal can be achieved through the base station, satellite, fronthaul network, wireless baseband, backhaul network and time server.

[0054] In addition, Figure 3As shown, the communication network can also achieve signal time synchronization through the bearer network. The base station transmits time information through network messages to achieve synchronization between the base station and the time server in the network. Usually, a network system has a primary time server and a backup time server. When the bearer network is used to achieve signal time synchronization, multiple base stations can be synchronized with the primary time server. Among them, the bearer network from the time server to the base station can be divided into: access layer, aggregation layer, scheduling layer and core layer. The base station is connected to the access layer equipment, and the time server is connected to the core layer equipment.

[0055] like Figure 4 As shown in the figure, in the time synchronization scheme of signals through the bearer network, 1588 hop-by-hop time synchronization is one of the network clock implementation schemes, which can be applied to Ethernet transmission networking. Network devices can exchange 1588V2 messages, calculate time and frequency offsets through accurate timestamps, and achieve frequency synchronization and time synchronization between network devices. In order to implement this scheme, all intermediate devices in the bearer network support the boundary clock (BC) function and transparent clock (TC) function defined by the 1588V2 protocol.

[0056] like Figure 5 As shown, relative to Figure 4 The 1588 hop-by-hop time synchronization and 1588 transparent transmission time synchronization shown in the figure are low-cost and easy-to-deploy solutions. The 1588V2 clock server deployed on the core network side carries the synchronization information, which is transparently transmitted to the base station through the intermediate transmission network, and the base station restores the synchronization technology of frequency and time information. This solution does not require the intermediate transmission network to support the 1588V2 BC function hop by hop, but can require the transparent transmission of the intermediate transmission network, and has low requirements for intermediate devices.

[0057] like Figure 6 As shown in FIG, when the communication link between device A and device B is an optical fiber, the different lengths of the transmitting and receiving optical fibers will cause asymmetric delays, resulting in clock synchronization deviations. Figure 7 As shown, device A sends a first optical signal to device B at timestamp t1, and device B receives the first optical signal sent by device A at timestamp t2; device B sends a second optical signal to device A at timestamp t3, and device A receives the second optical signal sent by device B at timestamp t4. In the network, there is a time deviation offset between the master clock and the slave clock and a delay time Delay caused by network transmission. According to the transmission process of optical signals in the communication network, it can be seen that:

[0058] The transmission delay from device A to B optical fiber Delay_AB = (t2-t1) + time deviation offset;

[0059] Transmission delay from device B to optical fiber A Delay_BA = (t4-t3)-time offset offset;

[0060] Time deviation offset = ((t4-t3)-(t2-t1)-(Delay_BA-Delay_AB)) / 2;

[0061] It can be seen from this that the error T introduced by the asymmetric delay of the transmitting and receiving optical fibers is (Delay_BA-Delay_AB) / 2.

[0062] In summary, in the existing optical fiber communication network, clock synchronization errors may occur due to optical fiber asynchrony, thereby affecting the transmission of messages.

[0063] Based on this, an embodiment of the present application provides a time synchronization method. In a scenario where a first optical network device is connected to a second optical network device via an optical fiber, a first transmission time S1 of a first optical signal and a second transmission time S2 of a second optical signal can be determined. The first optical signal and the second optical signal are optical signals sent by the first optical network device to the second optical network device via the same optical fiber, and the first optical signal and the second optical signal have different wavelengths. A transmission delay difference D1 between the first optical signal and the second optical signal is determined based on the first transmission time S1 and the second transmission time S2. A delay coefficient k related to the transmission delay difference D1 and the wavelength of the first optical signal is determined. 1. Determine the optical fiber length L between the first optical network device and the second optical network device according to the delay coefficient k2 related to the wavelength of the second optical signal; determine the absolute transmission delay D2 from the first optical network device to the second optical network device according to the optical fiber length L, the speed of light v in the optical fiber, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal; determine the clock deviation T between the first optical network device and the second optical network device according to the absolute transmission delay D2, the first transmission time S1 and the second transmission time S2; and perform clock synchronization on the first optical network device and the second optical network device according to the clock deviation T.

[0064] like Figure 8 As shown, the time synchronization method provided in the embodiment of the present application can be applied to Figure 8 In the communication system shown, the first optical network device and the second optical network device are connected via an optical fiber, and the first optical network device sends a first optical signal and a second optical signal with different wavelengths to the second optical network device via the same optical fiber, thereby determining the clock deviation between the first optical network device and the second optical network device, and then performing clock synchronization based on the clock deviation. It can be understood that the time synchronization method provided in the embodiment of the present application can be applied to the first optical network device in the system, and can also be applied to the second optical network device in the system, and the specific details are not limited here.

[0065] It is understandable that in the embodiments of the present application, the execution subject may execute some or all of the steps in the embodiments of the present application, and these steps or operations are only examples. The embodiments of the present application may also execute other operations or variations of various operations. In addition, the various steps may be executed in different orders presented in the embodiments of the present application, and it is possible that not all operations in the embodiments of the present application need to be executed.

[0066] It should be noted that the message names between the devices or the names of the parameters in the messages in the following embodiments of the present application are only examples, and other names may be used in the specific implementation, and the embodiments of the present application do not specifically limit this.

[0067] like Fig. 9 As shown, a time synchronization method provided by an embodiment of the present application is taken as an example of a second optical network device executing the method, and the method includes the following steps:

[0068] 901. A first optical network device determines an optical fiber length L and an absolute transmission delay D2 according to a relative transmission delay difference D1 between a first optical signal and a second optical signal.

[0069] The first optical network device determines the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 of the first optical signal and the second optical signal, wherein the first optical signal and the second optical signal are optical signals sent by the first optical network device to the second optical network device through the same optical fiber in the same direction, and the first optical signal and the second optical signal have different wavelengths.

[0070] In a possible implementation manner, the first optical network device first receives the first optical signal and the second optical signal from the first optical network device.

[0071] Specifically, the first optical network device sends a first optical signal to device B at timestamp t1 and simultaneously sends timestamp t1; device B receives the first optical signal sent by device A at timestamp t2 and also receives timestamp t1 corresponding to the first optical signal.

[0072] The first optical network device will also send a second optical signal to device B at timestamp t3, and send timestamp t3 at the same time; device B receives the second optical signal sent by device A at timestamp t4, and also receives timestamp t1 corresponding to the second optical signal.

[0073] In the embodiment of the present application, the first optical signal and the second optical signal have different wavelengths, the wavelength of the first optical signal is λ1, and the wavelength of the second optical signal is λ2.

[0074] In the embodiment of the present application, the first optical network device sends the first optical signal and the second optical signal to the second optical network device through the same optical fiber.

[0075] In one possible implementation, Fig.10 and Fig.11 As shown, in the embodiment of the present application, the first optical network device includes a first optical module, the second optical network device includes a second optical module, and the first optical module is frequency synchronized with the real-time clock of the second optical module. Specifically, the first real-time clock (RTC) module of the first optical module and the second RTC module of the second optical module are frequency synchronized, the clock source of the light source output port of the first optical module is the reference clock of the first RTC, and the second RTC module of the second optical module uses the clock and data recovery (CDR) recovery clock as the reference clock of the second RTC module.

[0076] In another possible implementation, Fig.12 and Fig.13 As shown, in an embodiment of the present application, the first optical network device includes a first optical module and a third optical module, the first optical module is used to generate a first optical signal and send it to the second optical module, and the third optical module is used to generate a second optical signal and send it to the fourth optical module. The first optical module and the third optical module share a first RTC module, and the clock source of the light source output port of the first optical module and the third optical module is the reference clock of the first RTC. The second optical network device includes a second optical module and a fourth optical module, the second optical module is used to receive the first optical signal from the first optical module, the fourth optical module is used to receive the second optical signal from the third optical module, the second optical module and the fourth optical module share a second RTC module, and the second optical module and the fourth optical module use the CDR recovery clock as the reference clock.

[0077] In this possible implementation, the first optical signal of the first optical module of the first optical network device and the second optical signal of the third optical module can be processed by the first wavelength combination / demultiplexing module and the first optical amplifier module and transmitted to the second optical network device through the same optical fiber. Correspondingly, the second optical network device receives the first optical signal through the second optical amplifier module and the second wavelength combination / demultiplexing module, and the fourth optical module of the second optical network device receives the second optical signal.

[0078] In the embodiment of the present application, the reference clock of the RTC module of the transmitting optical module is also the clock source of the RTC module of the receiving optical module, thereby achieving RTC frequency synchronization of the devices at both ends and achieving transmission and reception frequency synchronization.

[0079] In the present application embodiment, Fig.14As shown, in a possible implementation, the laser sources of the optical modules of the first optical network device and the second optical network device are both optical frequency combs. The optical frequency comb as a laser source can generate a plurality of equally spaced optical frequency teeth, and the frequency of the plurality of optical frequency teeth Fn = n*frep, where frep is the repetitive frequency. The plurality of equally spaced optical frequency teeth generated by the optical frequency comb as a laser source have good coherence characteristics. The coherent optical frequency teeth Tx_λ1 and Tx_λ2 have the same frequency deviation and phase deviation; the coherent optical frequency teeth Rx_λ1 and Rx_λ2 have the same frequency deviation and phase deviation.

[0080] In this possible implementation, an optical frequency comb is used as a laser source at the transceiver node to avoid synchronization errors caused by common mode noise such as laser wavelength and error, thereby improving the accuracy of the time synchronization method provided in the embodiment of the present application.

[0081] After the first optical network device receives the first optical signal and the second optical signal from the first optical network device, the second optical network device may determine the first transmission time S1 and the second transmission time S2.

[0082] Specifically, the second optical network device determines a first transmission time S1 and a second transmission time S2. The first transmission time S1 is equal to the timestamp t2 of the second optical network device receiving the first optical signal minus the timestamp t1 of the first optical network device sending the first optical signal, that is, S1 = t2-t1. The second transmission time S2 is equal to the timestamp t4 of the second optical network device receiving the second optical signal minus the timestamp t3 of the first optical network device sending the first optical signal, that is, S2 = t4-t3.

[0083] In a possible implementation, the timestamps t1, t2, t3 and t4 may be measured by the first optical network device and the second optical network device, so as to determine the first transmission time S1 and the second transmission time S2.

[0084] In another possible implementation, when the optical frequency comb is used as the laser source, the second optical network device can determine the first transmission time S1 and the second transmission time S2 through correlation detection.

[0085] Specifically, the wavelength of the first optical signal is λ1, and the angular frequency is ω1; the wavelength of the second optical signal is λ2, and the angular frequency is ω2. The second optical network device at the receiving end has a frequency deviation ωe and a phase deviation θe. The absolute transmission delay of the first optical signal between the first optical network device and the second optical network device is D_AB_λ1, and the absolute transmission delay of the second optical signal between the first optical network device and the second optical network device is D_AB_λ2.

[0086] On the transmitting laser side of the first optical network device:

[0087] t1=exp(ω1*t+ω1*θ); t2=exp(ω2*t+ω2*θ).

[0088] On the receiving laser side of the second optical network device:

[0089] r1=exp(ω1*t+ωe*t+ω1*θe); r2=exp(ω2*t+ωe*t+ω2*ωe).

[0090] The optical signal received by the second optical network device:

[0091] t3=exp(ω1*t+ω1*θ+ω1*S1); t4=exp(ω2*t+ω2*θ+ω2*S2).

[0092] Through coherent detection, we get:

[0093] t3 / r1=exp(ω1*t+ω1*θ+ω1*S1) / exp(ω1*t+ωe*t+ω1*θe)=exp(-ωe*t+ω1*S1+ω1*θ-ω1*θe).

[0094] t4 / r2=exp(ω2*t+ω2*θ+ω2*S2) / exp(ω2*t+ωe*t+ω2*ωe)=exp(-ωe*t+ω2*S2+ω2*θ-ω2*θe).

[0095] It can be further determined that:

[0096] In(t3 / r1)=-ωe*t+ω1*S1+ω1*θ-ω1*θe.

[0097] In(t4 / r2)=-ωe*t+ω2*S2+ω2*θ-ω2*θe.

[0098] By coherent detection of the first optical signal, S1 = -ωe / ω1*t-θe+θ+D_AB_λ1 is obtained.

[0099] By coherently detecting the second optical signal, S2 = -ωe / ω2*t-θe+θ+D_AB_λ2 is obtained.

[0100] It can be understood that the first transmission time S1 and the second transmission time S2 here are values ​​that can be calculated by the device, and are determined values ​​after this step is executed.

[0101] like Fig.15As shown, in the embodiment of the present application, the second network device can extract the RTC clock of the second network device and the first transmission time S1 and the second transmission time S2 from the CDR loop. The CDR loop may include a CDR module, an analog to digital converter (ADC), a digital-controlled oscillator (DCO), and a filter.

[0102] In this possible implementation, the solution of determining the RTC clock, the first transmission time S1 and the second transmission time S2 from the CDR loop has higher accuracy, thereby improving the accuracy of time synchronization.

[0103] In an embodiment of the present application, the second optical network device can determine the first transmission time S1 and the second transmission time S2 through coherent detection, and cooperate with the optical frequency comb as a laser source to avoid the synchronization error between the two first optical signals and the second optical signal due to frequency deviation and phase deviation, thereby improving the accuracy of time synchronization.

[0104] Then the second optical network device determines the transmission delay difference D1 according to the first transmission time S1 and the second transmission time S2, and the transmission delay difference D1 is the difference between the actual transmission time of the first optical signal and the actual transmission time of the second optical signal, that is, the transmission delay difference D1 = S2 - S1.

[0105] The second optical network device then determines the optical fiber length L between the first optical network device and the second optical network device.

[0106] Specifically, the second optical network device determines the optical fiber length L between the first optical network device and the second optical network device according to the transmission delay difference D1, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal.

[0107] Specifically, the optical fiber length L can be calculated based on the delay difference. For the first optical signal, the first transmission time S1 determined by the second optical network device is L / v+k_λ1*L+T. Where v is the speed of the optical signal transmitted in the optical fiber, k_λ1 is the wavelength-related delay coefficient of the first optical signal with a wavelength of λ1, and T is the clock deviation between the first optical network device and the second optical network device. Accordingly, the second transmission time S2 is L / v+k_λ2*L+T, and k_λ2 is.

[0108] That is, D1=S2-S1=L / v+k_λ2*L+T-(L / v+k_λ1*L+T)=(k_λ2-k_λ1)*L;

[0109] Optical fiber length L = D1 / (k_λ2-k_λ1).

[0110] Therefore, the second optical network device can determine the optical fiber length L between the first optical network device and the second optical network device according to the transmission delay difference D1, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal.

[0111] The second optical network device determines an absolute transmission delay D2 from the first optical network device to the second optical network device.

[0112] Specifically, the second optical network device determines the absolute transmission delay D2 from the first optical network device to the second optical network device based on the optical fiber length L, the speed of light v of the optical signal in the optical fiber, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal.

[0113] Specifically, the second optical network device determines the absolute transmission delay D2 from the first optical network device to the second optical network device through the following process:

[0114] Absolute transmission delay D2 + clock deviation T = first transmission time S1 = L / v + k_λ1*L+T;

[0115] Absolute transmission delay D2 = L / v + k_λ1*L;

[0116] Fiber length L = D1 / (k_λ2-k_λ1);

[0117] Absolute transmission delay D2 = [D1 / (k_λ2-k_λ1)] / v+k_λ1*[D1 / (k_λ2-k_λ1)];

[0118] 902. The second optical network device determines a clock deviation T between the first optical network device and the second optical network device.

[0119] The second optical network device determines the clock deviation T between the first optical network device and the second optical network device according to the absolute transmission delay D2, the first transmission time S1 and the second transmission time S2.

[0120] Specifically, the second optical network device determines the clock deviation T between the first optical network device and the second optical network device = S1 - absolute transmission delay D2 = S1 - D2 = S1 - L / v - k_λ1*L.

[0121] 903. The second optical network device performs clock synchronization according to the clock deviation T.

[0122] The second optical network device performs clock synchronization on the first optical network device and the second optical network device according to the clock deviation T

[0123] Specifically, after determining the clock deviation T between the first optical network device and the second optical network device, the second optical network device can adjust the device clock of the second optical network to be synchronized with the clock of the first optical network device, that is, determine the device clock of the second optical network before adjustment plus the clock deviation T as the adjusted clock. For example, if the device clock of the first optical network device before adjustment is Tb1, then the device clock of the first optical network device after adjustment is Tb2=Tb1+T.

[0124] In the embodiment of the present application, the problem of clock synchronization error caused by optical fiber asynchrony is solved, the calculation accuracy of the absolute delay is only related to the measurement accuracy of the delay difference D1, and is not sensitive to the measurement accuracy of the dispersion coefficient and the speed of light in the optical fiber. The solution is easy to implement.

[0125] The embodiment of the present application provides an optical network device 1600. In the embodiment of the present application, the optical network device 1600 can be divided into functional modules according to the above method example. For example, each functional module can be divided corresponding to each function, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0126] In the case of dividing each functional module into corresponding functional modules, Fig.16 A possible structural diagram of the optical network device 1600 involved in the above embodiment is shown. Fig.16 As shown, the optical network device 1600 includes:

[0127] The first determination module 1601 is used to determine the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 between the first optical signal and the second optical signal, wherein the first optical signal and the second optical signal are optical signals sent by the first optical network device to the second optical network device through the same optical fiber in the same direction, and the first optical signal and the second optical signal have different wavelengths; for example, executing step 901 in the above method embodiment: the first optical network device determines the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 between the first optical signal and the second optical signal.

[0128] In a possible implementation, the first determining module 1601 includes:

[0129] The fourth determining unit 1602 is configured to determine the first transmission time S1 of the first optical signal and the second transmission time S2 of the second optical signal by coherent optical detection. For example, step 901 in the above method embodiment is performed: the first optical network device determines the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 of the first optical signal and the second optical signal.

[0130] The first determination unit 1603 is used to determine the relative transmission delay difference D1 according to the first transmission time S1 of the first optical signal and the second transmission time S2 of the second optical signal; for example, executing step 901 in the above method embodiment: the first optical network device determines the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 of the first optical signal and the second optical signal.

[0131] The second determination unit 1604 is used to determine the optical fiber length L between the first optical network device and the second optical network device according to the transmission delay difference D1, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal; for example, executing step 901 in the above method embodiment: the first optical network device determines the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 between the first optical signal and the second optical signal.

[0132] The third determining unit 1605 is configured to determine the absolute transmission delay D2 from the first optical network device to the second optical network device according to the optical fiber length L, the light speed v in the optical fiber, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal. For example, step 901 in the above method embodiment is performed: the first optical network device determines the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 between the first optical signal and the second optical signal.

[0133] The second determination module 1606 is used to determine the clock deviation T between the first optical network device and the second optical network device according to the optical fiber length L and the absolute transmission delay D2; for example, executing step 902 in the above method embodiment: the second optical network device determines the clock deviation T between the first optical network device and the second optical network device.

[0134] The synchronization module 1607 is used to perform clock synchronization on the first optical network device and the second optical network device according to the clock deviation T. For example, step 903 in the above method embodiment is performed: the second optical network device performs clock synchronization according to the clock deviation T.

[0135] Each module of the above optical network device can also be used to perform other actions in the above method embodiment. All relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module and will not be repeated here.

[0136] Fig.17 It is a schematic diagram of the structure of an optical network device provided in an embodiment of the present application. The optical network device 1700 may include one or more central processing units (CPU) 1701 and a memory 1705. The memory 1705 stores one or more application programs or data.

[0137] The memory 1705 may be a volatile storage or a persistent storage. The program stored in the memory 1705 may include one or more modules, each of which may include a series of instruction operations in the optical network device. Furthermore, the central processor 1701 may be configured to communicate with the memory 1705 and execute a series of instruction operations in the memory 1705 on the optical network device 1700.

[0138] The central processor 1701 is used to execute the computer program in the memory 1705, so that the optical network device 1700 is used to execute: determine the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 between the first optical signal and the second optical signal, the first optical signal and the second optical signal are optical signals sent by the first optical network device to the second optical network device through the same optical fiber in the same direction, and the first optical signal and the second optical signal have different wavelengths; determine the clock deviation T between the first optical network device and the second optical network device according to the optical fiber length L and the absolute transmission delay D2; synchronize the clocks of the first optical network device and the second optical network device according to the clock deviation T. For specific implementation methods, please refer to Fig. 9 Steps 901-903 in the illustrated embodiment are not described in detail here.

[0139] The optical network device 1700 may also include one or more power supplies 1702, one or more wired or wireless network interfaces 1703, one or more input and output interfaces 1704, and / or one or more operating systems, such as Windows ServerTM, Mac OS XTM, UnixTM, LinuxTM, FreeBSDTM, etc.

[0140] The optical network device 1700 can perform the aforementioned Fig. 9 The operations performed by the optical network device in the illustrated embodiment will not be described in detail here.

[0141] The embodiment of the present application provides an optical communication system 1800, the optical network device management system 1800 includes a first optical network device 1801 and a second optical network device 1802, wherein the optical network device 1801 can execute the aforementioned Fig. 9The operations performed by the first optical network device in the embodiment shown in the figure may be performed by the second optical network device 1802. Fig. 9 The operations performed by the second optical network device in the illustrated embodiment will not be described in detail herein.

[0142] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using a software program, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loading and executing computer program instructions on a computer, all or part of the processes (or functions) described in the embodiments of the present application are implemented. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (digital subscriber line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or may contain one or more servers, data centers and other data storage devices that can be integrated with the medium. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a DVD), or a semiconductor medium (eg, a solid state disk (SSD)), etc. In the embodiment of the present application, the computer may include the aforementioned device.

[0143] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in a claim. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

Claims

1. A time synchronization method, characterized in that: The method comprises: Determine the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 between the first optical signal and the second optical signal, wherein the first optical signal and the second optical signal are optical signals sent by the first optical network device to the second optical network device through the same optical fiber in the same direction, and the first optical signal and the second optical signal have different wavelengths; Determine a clock deviation T between the first optical network device and the second optical network device according to the optical fiber length L and the absolute transmission delay D2; The clocks of the first optical network device and the second optical network device are synchronized according to the clock deviation T.

2. The method according to claim 1, characterized in that The method of determining the optical fiber length L and the absolute transmission delay D2 according to the relative transmission delay difference D1 between the first optical signal and the second optical signal comprises: Determine a relative transmission delay difference D1 according to a first transmission time S1 of the first optical signal and a second transmission time S2 of the second optical signal; Determine the optical fiber length L between the first optical network device and the second optical network device according to the transmission delay difference D1, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal; The absolute transmission delay D2 from the first optical network device to the second optical network device is determined according to the optical fiber length L, the light speed v in the optical fiber, the wavelength-related delay coefficient k1 of the first optical signal, and the wavelength-related delay coefficient k2 of the second optical signal.

3. The method according to claim 2, characterized in that The first optical network device includes a first optical module, and the second optical network device includes a second optical module. The real-time clock frequencies of the first optical module and the second optical module are synchronized, and the reference clock of the second optical module is a clock data recovery (CDR) recovery clock.

4. The method according to claim 2, characterized in that: The first optical network device includes a first optical module and a third optical module, the second optical network device includes a second optical module and a fourth optical module, the first optical signal is an optical signal sent by the first optical module to the second optical module, the second optical signal is an optical signal sent by the third optical module to the fourth optical module, the first optical module and the third optical module share a real-time clock, the second optical module and the fourth optical module share a real-time clock, and the reference clock of the second optical module and the fourth optical module is a CDR recovery clock.

5. The method according to any one of claims 1 to 4, characterized in that: The light sources of the first optical signal and the second optical signal are optical frequency comb light sources.

6. The method according to claim 5, characterized in that Before determining the relative transmission delay difference D1 according to the first transmission time S1 of the first optical signal and the second transmission time S2 of the second optical signal, the method further includes: A first transmission time S1 of the first optical signal and a second transmission time S2 of the second optical signal are determined by coherent optical detection.

7. An optical network device, characterized in that: The optical network equipment comprises: A first determining module, configured to determine the optical fiber length L and the absolute transmission delay D2 according to a relative transmission delay difference D1 between a first optical signal and a second optical signal, wherein the first optical signal and the second optical signal are optical signals sent by a first optical network device to a second optical network device through the same optical fiber in the same direction, and the first optical signal and the second optical signal have different wavelengths; A second determination module, configured to determine a clock deviation T between the first optical network device and the second optical network device according to the optical fiber length L and the absolute transmission delay D2; A synchronization module is used to perform clock synchronization on the first optical network device and the second optical network device according to the clock deviation T.

8. The optical network device according to claim 7, characterized in that: The first determining module comprises: A first determining unit, configured to determine a relative transmission delay difference D1 according to a first transmission time S1 of the first optical signal and a second transmission time S2 of the second optical signal; A second determining unit, configured to determine an optical fiber length L between the first optical network device and the second optical network device according to the transmission delay difference D1, a delay coefficient k1 related to the wavelength of the first optical signal, and a delay coefficient k2 related to the wavelength of the second optical signal; The third determining unit is used to determine the absolute transmission delay D2 from the first optical network device to the second optical network device according to the optical fiber length L, the speed of light v in the optical fiber, the delay coefficient k1 related to the wavelength of the first optical signal, and the delay coefficient k2 related to the wavelength of the second optical signal.

9. The optical network device according to claim 8, characterized in that: The light sources of the first optical signal and the second optical signal are optical frequency comb light sources.

10. The optical network device according to claim 9, characterized in that: The first determining module also includes: The fourth determining unit is configured to determine the first transmission time S1 of the first optical signal and the second transmission time S2 of the second optical signal by coherent optical detection.

11. An optical network device, characterized in that: The optical network device comprises a processor and a memory; the processor is coupled to the memory; the memory is used to store computer instructions, and the computer instructions are loaded and executed by the processor to enable the optical network device to implement the method according to any one of claims 1-6.

12. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores at least one computer program instruction, and the computer program instruction is loaded and executed by a processor to implement the method according to any one of claims 1 to 6.

13. An optical communication system, characterized in that: The optical communication system comprises a first optical network device and a second optical network device, wherein the first optical network device is used to execute the method according to any one of claims 1 to 6, and the second optical network device is used to execute the method according to any one of claims 1 to 6.

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