CN106027190B - A kind of clock synchronizing method and device - Google Patents

Abstract

The embodiment of the present invention discloses a clock synchronization method and device. The method and device are applied to a network where RoF and PON are integrated. The method includes: the hybrid optical line terminal OLT connects the The acquired simulated atomic clock synchronization signal is sent to the network module, and the network module extracts the simulated atomic clock synchronization signal; the network module calculates clock adjustment information through the recorded time information, and adjusts the clock of the network module. The method and device adopt a clock synchronization scheme based on RoF technology in a network where RoF and PON are integrated, that is, use a RoF link to transmit an accurate analog atomic clock synchronization signal obtained by a hybrid OLT, and the network module extracts the analog atomic clock The synchronization signal can effectively avoid the distortion problem after the clock synchronization signal is digitized, improve the clock synchronization accuracy of the network module on the access side, and realize accurate network clock synchronization.

Description

A clock synchronization method and device

technical field

The invention relates to the technical field of network communication, in particular to a clock synchronization method and device for a network based on the integration of wireless over light and passive optical networks.

Background technique

In the process of network communication, in order to ensure the quality of communication and make the business run normally, precise network clock synchronization must be required, that is, the time or frequency between network devices must be kept within a reasonable error level. Network clock synchronization includes time synchronization and frequency synchronization. Especially in the wireless access system, each base station node is required to strictly maintain the synchronization accuracy of the wireless interface, which requires each base station node to extract the clock through GPS to ensure its synchronization. However, the GPS clock synchronization solution requires the antenna to have a good view of the sky in order to ensure that the receiver can receive effective signals, which increases the difficulty of GPS site selection, and the feeder line needs to be erected between the antenna and the base station, which increases the erection cost. In addition, the base station has no other backup clocks, and the system reliability is low. Although the IEEE 1588V2 clock synchronization protocol can solve the problems of high time synchronization cost and insufficient precision, and its synchronization accuracy can reach sub-microsecond level, what is transmitted based on this protocol is a digital clock signal, that is, in the clock synchronization process, first To digitize the clock signal, this process will inevitably cause the loss of many attributes in the clock signal, resulting in the distortion of the clock signal recognized by the network module at the receiving end, which will have a certain impact on the synchronization delay and accuracy, and ultimately affect the communication quality.

Contents of the invention

The embodiment of the invention discloses a network clock synchronization method and device based on the integration of wireless over optical network and passive optical network, so as to improve the clock synchronization accuracy of the network module on the access side.

In order to achieve the above purpose, the embodiment of the present invention discloses a clock synchronization method, which is applied to a hybrid optical line terminal OLT in a network where RoF over light and PON are integrated, and the method includes:

Sending a clock synchronization message to the network module, so that the network module records the arrival time T2 of the clock synchronization message, and simultaneously acquires a simulated atomic clock synchronization signal _;

Send the simulated atomic clock synchronization signal to the network module through the RoF link, so that the network module extracts and records the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal;

Receiving the delay request message sent by the network module, recording the arrival time T4 _of the delay request message, and the network module recording the sending time T3 of the delay request message _;

_Sending a delay request feedback message with the arrival time T4 to the network module, so that the network module acquires and records the arrival time _T4 , and synchronizes the sending time T1 _of the message through the clock , the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate clock adjustment information, and adjust according to the clock adjustment information The clock of the network module.

Optionally, the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the delay request message The arrival time T ₄ , calculate the clock adjustment information, including:

The network module calculates the time offset T _offset between the network module and the hybrid OLT through T ₂ -T ₁ ;

By the following formula:

T _delay = (T ₂ -T ₁ +T ₄ -T ₃ )/2

_T'offset ＝(T ₂ -T ₁ -T ₄ +T ₃ )/2

The synchronization packet transmission delay T _delay and the corrected time offset T' _offset between the network module and the hybrid OLT are calculated.

Optionally, an optical splitter is provided in the RoF link, and the hybrid OLT uses the optical splitter to transmit the analog atomic clock synchronization signal to different network modules.

Optionally, the network module includes one or more of hybrid ONU, ONU-BS, and BS.

In order to achieve the above purpose, the embodiment of the present invention also discloses a clock synchronization method, which is applied to a network module in a network where RoF over fiber and PON are integrated, and the method includes:

Receiving the clock synchronization message sent by the hybrid optical line terminal OLT, and recording the arrival time T2 of the clock synchronization message, the hybrid OLT acquires a simulated atomic clock synchronization signal while sending the clock synchronization message _;

Receiving the simulated atomic clock synchronization signal sent by the hybrid OLT through the RoF link, extracting the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal and recording it;

Sending a delay request message to the hybrid OLT, so that the hybrid OLT records the arrival time T ₄ of the delay request message, and records the sending time T ₃ of the delay request message;

_Receiving the delay request feedback message with the arrival time T4 sent by the hybrid OLT, obtaining and recording the arrival time _T4 , and synchronizing the clock through the sending time T1 _of the clock synchronization message The arrival time T ₂ of the message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate the clock adjustment information, and adjust the clock adjustment information of the network module according to the clock adjustment information clock.

Optionally, the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the delay request message The arrival time T ₄ , calculate the clock adjustment information, including:

Calculate the time offset T _offset between the network module and the hybrid OLT through T ₂ -T ₁ ;

By the following formula:

T _delay = (T ₂ -T ₁ +T ₄ -T ₃ )/2

_T'offset ＝(T ₂ -T ₁ -T ₄ +T ₃ )/2

The synchronization packet transmission delay T _delay and the corrected time offset T' _offset between the network module and the hybrid OLT are calculated.

Optionally, an optical splitter is provided in the RoF link, and the hybrid OLT uses the optical splitter to transmit the analog atomic clock synchronization signal to different network modules.

Optionally, the network module includes one or more of hybrid ONU, ONU-BS, and BS.

In order to achieve the above purpose, the embodiment of the present invention discloses a clock synchronization device, which is applied to a hybrid optical line terminal OLT in a network where wireless over optical RoF and passive optical network PON are integrated, which includes:

A first sending unit, configured to send a clock synchronization message to the network module, so that the network module records the arrival time T2 of the clock synchronization message _;

a synchronization signal acquisition unit, configured to acquire an analog atomic clock synchronization signal while sending the clock synchronization message;

The second sending unit is configured to send the simulated atomic clock synchronization signal to the network module through the RoF link, so that the network module extracts the clock synchronization message through the simulated atomic clock synchronization signal Send time T ₁ and record;

The first receiving unit is used to receive the delay request message sent by the network module, and the network module records the sending time T3 _of the delay request message;

The first recording unit is used to record the arrival time T4 of the delay request message _; and

_A feedback unit, configured to send a delay request feedback message with the arrival time T4 to the network module, so that the network module acquires and records the arrival time _T4 , and synchronizes the message through the clock The sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate the clock adjustment information, according to the The clock adjustment information adjusts the clock of the network module.

In order to achieve the above purpose, the embodiment of the present invention also discloses a clock synchronization device, which is applied to the network module in the network where the radio-over-fiber RoF and the passive optical network PON are integrated, which includes:

The second receiving unit is used to receive the clock synchronization message sent by the hybrid optical line terminal OLT;

A _second recording unit, configured to record the arrival time T2 of the clock synchronization message;

A third receiving unit, configured to receive the simulated atomic clock synchronization signal obtained by the hybrid OLT while sending the clock synchronization message and sent through the RoF link;

A third recording unit, configured to extract and record the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal;

A third sending unit, configured to send a delay request message to the hybrid OLT, so that the hybrid OLT records the arrival time T4 of the delay request message _;

A fourth recording unit, configured to record the sending time T3 _of the delay request message;

A _fourth receiving unit, configured to receive a delay request feedback message sent by the hybrid OLT with the arrival time T4 of the transmission delay request message;

a fifth recording unit, configured to obtain and record the arrival time T ₄ ;

A clock adjustment unit, configured to pass the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the delay request message The clock adjustment information is calculated at the arrival time T ₄ of , and the clock of the network module is adjusted according to the clock adjustment information. The clock synchronization method and device based on the fusion of RoF over optical network and PON network provided by the embodiments of the present invention, in the fusion network of RoF and PON, through the clock synchronization scheme based on RoF technology, that is, using the RoF link Transmit the extremely accurate analog atomic clock signal obtained by the hybrid OLT, and extract the analog atomic clock signal by the network module, thereby effectively avoiding the distortion of the clock synchronization signal after digitization and improving the clock synchronization accuracy of the network module on the access side. Realize precise network clock synchronization.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 is a network architecture of RoF and PON fusion in the prior art;

FIG. 2 is a schematic flowchart of a clock synchronization method provided by an embodiment of the present invention;

FIG. 3 is a message sending process provided by an embodiment of the present invention;

FIG. 4 is a schematic flowchart of another clock synchronization method provided by an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a clock synchronization device provided by an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of another clock synchronization device provided by an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The embodiment of the present invention is based on the network realization of the fusion of RoF over optical fiber and passive optical network PON. Fig. 1 shows the network framework of RoF and PON fusion in the prior art. Firstly, the network framework based on RoF and PON fusion will be described below. brief introduction.

RoF technology is a technology that modulates the radio frequency signal subcarrier onto the optical carrier to realize technical optical fiber network transmission. It makes full use of the advantages of optical fiber anti-electromagnetic interference and effectively solves the problem of large power loss in wireless signal transmission in the atmosphere. In addition, the RoF technology greatly simplifies the remote base station, realizes the concentration of functions in the central office, the sharing of devices and equipment, and the dynamic allocation of spectrum bandwidth resources, thereby reducing the cost of the entire broadband wireless access. The development trend of the next generation communication network requires sufficient bandwidth and high flexibility. Not only the baseband signal of PON needs to be transmitted by optical fiber, but also the RoF signal needs to be transmitted by optical fiber, so as to better provide users with broadband wireless access services. Therefore, the integration of RoF and PON converged transmission platforms is of great significance. It integrates wired and wireless services into the same network structure, reduces configuration costs, performs transparent service upgrades, and meets the service needs of different end users.

The central station (CS) in the RoF system has high compatibility with the optical line terminal (OLT) in the PON, the base station (BS) and the hybrid optical network unit (ONU) in the PON, and both are based on optical fiber Transmission, which can solve the problem of bandwidth mismatch between high-speed wireless access and optical fiber access, thus providing the basis of physical architecture for the integration of the two.

At present, there are several solutions for the integration of RoF and PON; one is that the wired baseband signal is carried by the optical carrier of the optical millimeter wave, and the wireless access signal is carried by the sideband of the optical millimeter wave; the other is to realize the wired and wireless communication through orthogonal modulation. fusion. The third is to set the laser source at the base station, and perform homodyne and heterodyne detection to generate wired and wireless access signals. In the first two schemes, because wired and wireless signals occupy different transmission signals, channel resources cannot be fully utilized. The third solution introduces active equipment such as lasers in the base station, which increases the cost of the receiving end.

FIG. 2 is a schematic flow chart of a clock synchronization method provided by an embodiment of the present invention. The clock synchronization method is applied to a hybrid optical line terminal OLT in a network where radio-over-fiber RoF and passive optical network PON are integrated, and the hybrid optical line terminal OLT That is, an optical line terminal capable of transmitting both analog and digital signals, including the following steps:

S201: Send a clock synchronization message Sync to a network module, so that the network module records the arrival time T ₂ of the clock synchronization message Sync, and acquires an analog atomic clock synchronization signal Follow_up at the same time.

Wherein, the network module is a hybrid ONU, ONU-BS and BS. It should be emphasized that the above-mentioned network modules are only examples and should not limit the embodiment of the present invention, and there may be only one network module.

It should be emphasized that the simulated atomic clock synchronization signal is the electromagnetic wave emitted by the atomic clock at all times, and the acquisition of the simulated atomic clock synchronization signal can refer to the atomic clock acquisition method in the prior art, for example: the pulse generated by the atomic clock can be The signal is obtained by frequency standard counting. Specifically, no limitation is made here.

S202: Send the simulated atomic clock synchronization signal Follow_up to the network module through the RoF link, so that the network module extracts the sending time of the clock synchronization message Sync through the simulated atomic clock synchronization signal Follow_up T ₁ and record.

Wherein, the atomic clock synchronization signal is carried by a radio frequency signal, and the hybrid OLT sends the simulated atomic clock synchronization signal by modulating the simulated atomic clock synchronization signal onto an optical carrier, and transmitting it to each network module through the RoF link.

In an implementation manner, an optical splitter may be provided in the RoF link, and the hybrid OLT transmits the analog atomic clock synchronization signal to different network modules by using the optical splitter.

S203: Receive the delay request message Delay_req sent by the network module, record the arrival time T ₄ of the delay request message Delay_req, and record the sending time T ₃ of the delay request message Delay_req by the network module.

S204: Send a delay request feedback message _{Delay_resq} with the arrival time T4 to the network module, so that the network module acquires and records the arrival time _T4 , and synchronizes the sending of the message through the clock time T ₁ , the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate the clock adjustment information, and calculate the clock adjustment information according to the clock The adjustment information adjusts the clock of the network module.

Wherein, the network module calculates clock adjustment information, including:

The first stage: calculate the time offset T _offset between each network module and the hybrid OLT through T ₂ -T ₁ ;

The second stage: through the following formula:

T _delay = (T ₂ -T ₁ +T ₄ -T ₃ )/2

_T'offset ＝(T ₂ -T ₁ -T ₄ +T ₃ )/2

The synchronization packet transmission delay T _delay and the corrected time offset T' _offset between each network module and the hybrid OLT are calculated.

After the time _{offset T'offset} is calculated, each network module can adjust and adjust the clock of the network module according to the time _{offset T'offset} . The specific clock adjustment process can be the same as that of the prior art, and will not be repeated here.

Thus, each network module completes a clock synchronization.

It should be noted that when the number of network modules is more than 2, each network module needs to calculate the adjustment information corresponding to each network module according to the relevant steps of the first stage and the second stage above: (1) Time offset T _offset , (2) synchronous message transmission delay T _delay and (3) time offset T' _offset between hybrid OLTs, and adjust each network module according to the adjustment information (1)-(3) The clock of the network module.

It should be emphasized that although each network module has recorded the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the arrival time of the delay request message T ₄ . However, since each network module records its corresponding time, the specific values of T ₁ , T ₂ , T ₃ , and T ₄ are not necessarily the same.

Fig. 3 shows the message sending process provided by the embodiment of the present invention.

As shown in Figure 3, the hybrid OLT sends the clock synchronization message Sync to the network module, so that the network module records the arrival time T2 of the clock synchronization message Sync, and simultaneously obtains the simulated atomic clock synchronization signal _{Follow_up} ;

The hybrid OLT sends the simulated atomic clock synchronization signal Follow_up to the network module through the RoF link, so that the network module extracts the sending time of the clock synchronization message Sync through the simulated atomic clock synchronization signal Follow_up T ₁ and record;

Hybrid OLT receives the delay request message Delay_req sent by the network module, records the arrival time T4 of the delay request message _{Delay_req} , and the network module records the sending time T3 of the delay request message _{Delay_req} ;

The hybrid OLT sends a delay request feedback message Delay_resq with the arrival time T ₄ to the network module, so that the network module acquires and records the arrival time T ₄ .

FIG. 4 is a schematic flowchart of another clock synchronization method provided by an embodiment of the present invention. The clock synchronization method is applied to a network module in a network where RoF over fiber and PON are integrated, and includes the following steps:

S401: Receive a clock synchronization message sent by the hybrid optical line terminal OLT, and record the arrival time _T2 of the clock synchronization message, and the hybrid OLT obtains a simulated atomic clock synchronization signal while sending the clock synchronization message .

S402: Receive the simulated atomic clock synchronization signal sent by the hybrid OLT through the RoF link, extract and record the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal.

S403: Send a delay request message to the hybrid OLT, so that the hybrid OLT records the arrival time T ₄ of the delay request message and records the sending time T ₃ of the delay request message.

S404: Receive the delay request feedback message with the arrival time T ₄ sent by the hybrid OLT, obtain and record the arrival time T ₄ , and synchronize the sending time T ₁ of the message through the clock, the The arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate clock adjustment information, and adjust the network according to the clock adjustment information The module's clock.

It can be seen from the above-mentioned embodiments that the clock synchronization method provided by the embodiments of the present invention adopts a clock synchronization scheme based on RoF technology under the network architecture where RoF and PON are integrated, that is, the timing obtained by using the RoF link to transmit the hybrid OLT is extremely accurate. The analog atomic clock synchronization signal is extracted by the network module, which can effectively avoid the distortion of the digital clock synchronization signal, improve the clock synchronization accuracy of the network module on the access side, and achieve accurate network clock synchronization.

Fig. 5 is a schematic structural diagram of a hybrid optical line terminal OLT provided by an embodiment of the present invention, which corresponds to the process shown in Fig. 2, and the hybrid optical line terminal OLT is applied to the integration of wireless over optical RoF and passive optical network PON network, which includes:

The first sending unit 501 is configured to send a clock synchronization message to the network module, so that the network module records the arrival time T2 of the clock synchronization message _;

A synchronization signal acquisition unit 502, configured to acquire an analog atomic clock synchronization signal while sending the clock synchronization message;

The second sending unit 503 is configured to send the simulated atomic clock synchronization signal to the network module through the RoF link, so that the network module extracts the clock synchronization message through the simulated atomic clock synchronization signal The sending time T ₁ of and record;

The first receiving unit 504 is configured to receive the delay request message sent by the network module, and the network module records the sending time T3 _of the delay request message;

The first recording unit 505 is configured to record the arrival time T4 of the delay request message _; and

_A feedback unit 506, configured to send a delay request feedback message with the arrival time T4 to the network module, so that the network module obtains and records the arrival time _T4 , and synchronizes the message with the clock The sending time T ₁ of the message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate the clock adjustment information, according to The clock adjustment information adjusts the clock of the network module.

Fig. 6 is a schematic structural diagram of a network module provided by an embodiment of the present invention, which corresponds to the process shown in Fig. 4. The network module is applied to a network in which wireless over optical RoF and passive optical network PON are integrated, and includes:

The second receiving unit 601 is configured to receive the clock synchronization message sent by the hybrid optical line terminal OLT;

The _second recording unit 602 is configured to record the arrival time T2 of the clock synchronization message;

The third receiving unit 603 is configured to receive the simulated atomic clock synchronization signal obtained by the hybrid OLT while sending the clock synchronization message and sent through the RoF link;

The third recording unit 604 is configured to extract and record the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal;

A third sending unit 605, configured to send a delay request message to the hybrid OLT, so that the hybrid OLT records the arrival time T4 of the delay request message _;

A fourth recording unit 606, configured to record the sending time T3 _of the delay request message;

The _fourth receiving unit 607 is configured to receive the delay request feedback message sent by the hybrid OLT with the arrival time T4 of the transmission delay request message;

A fifth recording unit 608, configured to obtain and record the arrival time T ₄ ;

The clock adjustment unit 609 is configured to use the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the delay request message At the arrival time T ₄ of the text, clock adjustment information is calculated, and the clock of the network module is adjusted according to the clock adjustment information.

It can be seen from the above-mentioned embodiments that the clock synchronization device provided by the embodiments of the present invention adopts a clock synchronization solution based on RoF technology under the network architecture where RoF and PON are integrated, that is, the timing obtained by using the RoF link to transmit the hybrid OLT is extremely accurate. The analog atomic clock synchronization signal is extracted by the network module, which can effectively avoid the distortion of the digital clock synchronization signal, improve the clock synchronization accuracy of the network module on the access side, and achieve accurate network clock synchronization.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. any such actual relationship or order exists between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Each embodiment in this specification is described in a related manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, as for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and for relevant parts, please refer to part of the description of the method embodiment.

Those of ordinary skill in the art can understand that all or part of the steps in the implementation of the above method can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, referred to herein as Storage media, such as: ROM/RAM, disk, CD, etc.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims (10)

1. A clock synchronization method, characterized in that, it is applied to the hybrid optical line terminal OLT in the network where wireless over light RoF and passive optical network PON merge, and the method includes: Sending a clock synchronization message to the network module, so that the network module records the arrival time T2 of the clock synchronization message, and simultaneously acquires a simulated atomic clock synchronization signal _; Send the simulated atomic clock synchronization signal to the network module through the RoF link, so that the network module extracts and records the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal; Receiving the delay request message sent by the network module, recording the arrival time T4 _of the delay request message, and the network module recording the sending time T3 of the delay request message _{; Sending} a delay request feedback message with the arrival time T4 to the network module, so that the network module acquires and records the arrival time _T4 , and synchronizes the sending time T1 _of the message through the clock , the arrival time T2 of the clock synchronization message, the sending time T3 of the delay request message, and the arrival time _{T4 of} the delay request _message , calculate clock adjustment information, and adjust according to the clock adjustment information The clock of the network module. 2. The method according to claim 1, characterized in that, the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the delay request message sending At time T ₃ and the arrival time T ₄ of the delay request message, calculate clock adjustment information, including: The network module calculates the time offset T _offset between the network module and the hybrid OLT through T ₂ -T ₁ ; By the following formula: T _delay = (T ₂ -T ₁ +T ₄ -T ₃ )/2 _T'offset ＝(T ₂ -T ₁ -T ₄ +T ₃ )/2 The synchronization packet transmission delay T _delay and the corrected time offset T' _offset between the network module and the hybrid OLT are calculated. 3. The method according to claim 1, wherein an optical splitter is provided in the RoF link, and the hybrid OLT uses the optical splitter to transmit the simulated atomic clock synchronization signal to different network module. 4. The method according to claim 1, wherein the network module comprises one or more of hybrid ONU, ONU-BS, and BS. 5. A clock synchronization method, characterized in that it is applied to a network module in a network where wireless over light RoF and passive optical network PON merge, and the method includes: Receiving the clock synchronization message sent by the hybrid optical line terminal OLT, and recording the arrival time T2 of the clock synchronization message, the hybrid OLT acquires a simulated atomic clock synchronization signal while sending the clock synchronization message _; Receiving the simulated atomic clock synchronization signal sent by the hybrid OLT through the RoF link, extracting the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal and recording it; Sending a delay request message to the hybrid OLT, so that the hybrid OLT records the arrival time T ₄ of the delay request message, and records the sending time T ₃ of the delay request message; _Receiving the delay request feedback message with the arrival time T4 sent by the hybrid OLT, obtaining and recording the arrival time _T4 , and synchronizing the clock through the sending time T1 _of the clock synchronization message The arrival time T ₂ of the message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate clock adjustment information, and adjust the clock adjustment information of the network module according to the clock adjustment information clock. 6. The method according to claim 5, characterized in that, the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the delay request message sending At time T ₃ and the arrival time T ₄ of the delay request message, calculate clock adjustment information, including: Calculate the time offset T _offset between the network module and the hybrid OLT through T ₂ -T ₁ ; By the following formula: T _delay = (T ₂ -T ₁ +T ₄ -T ₃ )/2 _T'offset ＝(T ₂ -T ₁ -T ₄ +T ₃ )/2 The synchronization packet transmission delay T _delay and the corrected time offset T' _offset between the network module and the hybrid OLT are calculated. 7. The method according to claim 5, wherein an optical splitter is provided in the RoF link, and the hybrid OLT uses the optical splitter to transmit the simulated atomic clock synchronization signal to different network module. 8. The method according to claim 5, wherein the network module comprises one or more of hybrid ONU, ONU-BS, and BS. 9. A clock synchronization device, characterized in that it is applied to the hybrid optical line terminal OLT in the network where the wireless over light RoF and the passive optical network PON merge, and it includes: A first sending unit, configured to send a clock synchronization message to the network module, so that the network module records the arrival time T2 of the clock synchronization message _; a synchronization signal acquisition unit, configured to acquire an analog atomic clock synchronization signal while sending the clock synchronization message; The second sending unit is configured to send the simulated atomic clock synchronization signal to the network module through the RoF link, so that the network module extracts the clock synchronization message through the simulated atomic clock synchronization signal Send time T ₁ and record; The first receiving unit is used to receive the delay request message sent by the network module, and the network module records the sending time T3 _of the delay request message; The first recording unit is used to record the arrival time T4 of the delay request message _; and _A feedback unit, configured to send a delay request feedback message with the arrival time T4 to the network module, so that the network module acquires and records the arrival time _T4 , and synchronizes the message through the clock The sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the arrival time T ₄ of the delay request message, calculate the clock adjustment information, according to the The clock adjustment information adjusts the clock of the network module. 10. A clock synchronization device, characterized in that it is applied to a network module in a network where wireless over light RoF and passive optical network PON merge, and it includes: The second receiving unit is used to receive the clock synchronization message sent by the hybrid optical line terminal OLT; A _second recording unit, configured to record the arrival time T2 of the clock synchronization message; A third receiving unit, configured to receive the simulated atomic clock synchronization signal obtained by the hybrid OLT while sending the clock synchronization message and sent through the RoF link; A third recording unit, configured to extract and record the sending time T1 _of the clock synchronization message through the simulated atomic clock synchronization signal; A third sending unit, configured to send a delay request message to the hybrid OLT, so that the hybrid OLT records the arrival time T4 of the delay request message _; A fourth recording unit, configured to record the sending time T3 _of the delay request message; A _fourth receiving unit, configured to receive a delay request feedback message sent by the hybrid OLT with the arrival time T4 of the transmission delay request message; a fifth recording unit, configured to obtain and record the arrival time T ₄ ; A clock adjustment unit, configured to pass the sending time T ₁ of the clock synchronization message, the arrival time T ₂ of the clock synchronization message, the sending time T ₃ of the delay request message, and the delay request message The clock adjustment information is calculated at the arrival time T ₄ of , and the clock of the network module is adjusted according to the clock adjustment information.