CN108111245A - Optical fiber transport channel clock system and its method - Google Patents

Abstract

A clock synchronization system for an optical fiber transmission channel, including: a clock and SYNC processing subsystem for distributing clocks and SYNC signals to different remote nodes, a signal transmission subsystem for completing optical/electrical, electrical/optical conversion and transmission of signals, A clock phase adjustment subsystem for adjusting the clock phase in real time, and a SYNC resampling subsystem for completing the phase realignment of the clock and SYNC. Wherein, the clock and SYNC processing subsystem includes a clock cycle delay distribution module, SYNC distribution and receiving module; the signal transmission subsystem includes an electrical-to-optical module, an optical fiber transmission module, and an optical-to-electrical module; the clock phase The regulating subsystem includes a phase-locked loop module and a variable phase delay module. The present invention also includes a method of synchronizing a system using an optical fiber transport channel clock. The invention can effectively complete the clock synchronization and sampling synchronization functions of all remote measurement nodes and the local data processing center, can adapt to optical fibers of different lengths, and has a simple system structure.

Description

Fiber transmission channel clock synchronization system and method

technical field

The invention relates to a clock synchronization method and device for multi-channel optical fiber transmission channels.

Background technique

As a new type of transmission medium, optical fiber has many obvious advantages compared with traditional copper cables, such as good confidentiality, anti-electromagnetic interference, anti-nuclear radiation, small size, light weight, etc., making optical fiber widely used in civilian and military applications. There are more and more applications in electronic systems. In the field of radar, as an important development direction of phased array radar, digital array radar adopts distributed transmission and reception, the number of sending and receiving nodes is large, and the amount of transmitted data is large. In engineering, optical fiber has been used to realize large-capacity data transmission of digital array radar However, due to the use of equal-length optical fibers, the scope of application is greatly reduced. Using unequal-length optical fibers as data transmission channels still has many problems to be solved in engineering. In the field of power systems, it is necessary to measure parameters such as temperature and current in real time, such as the detection of the temperature of the stator and rotor of high-voltage transformers and large motors. Due to the complex electromagnetic interference in the field environment, the traditional copper wire data transmission effect is poor, and will gradually be replaced by optical fiber. Instead of transmission, for example, distributed optical fiber temperature sensor is a high-tech developed in recent years for real-time measurement of space temperature field.

Due to the many advantages of optical fiber, distributed measurement and control systems such as those mentioned above increasingly adopt optical fiber as the transmission medium of data and clock. All measurement nodes are separated from each other in space and have no information interaction with each other, and all measurement nodes are physically connected to the data processing center through optical fibers. However, there are many problems in the transmission channels of the distributed measurement and control system, such as unequal length of optical fiber transmission, and the performance of the optical fiber is very sensitive to external temperature and humidity changes, mechanical vibrations, etc., so that the distributed measurement and control system uses optical fibers to achieve large-scale high-speed transmission. The clocks are not synchronized, and the clocks are not synchronized, which will cause the measurement and control nodes to be unable to send and receive signals at the same time, deteriorating the overall performance of the system, and even causing the system to fail to work normally. Therefore, a set of correction method and device capable of correcting clock inconsistency between system channels is needed, but so far there is no feasible implementation scheme.

Contents of the invention

The present invention overcomes the problem of clock inconsistency between channels when the existing distributed measurement and control system utilizes optical fiber transmission technology to realize large-scale data transmission, and proposes a method that can automatically measure and correct clock inconsistency in optical fiber transmission channels without obtaining the length of optical fiber in advance A fiber transport channel clock synchronization system and method.

Above-mentioned purpose of the present invention can be achieved by following technical scheme:

A clock synchronization system for an optical fiber transmission channel, including: a clock and SYNC processing subsystem for distributing clocks and SYNC signals to different remote nodes, a signal transmission subsystem for completing optical/electrical, electrical/optical conversion and transmission of signals, A clock phase adjustment subsystem for adjusting the clock phase in real time, and a SYNC resampling subsystem for completing the phase realignment of the clock and SYNC.

Wherein, the clock and SYNC processing subsystem includes:

The clock cycle delay distribution module is used to provide one clock signal for each remote measurement node. Phase offset selection with coarse output delay adjustment, with a minimum delay step equal to half the input clock period. The amount of delay can be set individually for each output clock. The value of the block's output delay amount is determined by the SYNC distribution and reception blocks.

The SYNC distribution and receiving module is configured to provide one SYNC signal for each remote measurement node, and simultaneously receive the SYNC signal sent back by each remote measurement node. This module can measure the number of clock cycles experienced by the SYNC signal sent and received, and this value determines the delay amount of each output of the clock cycle delay distribution module.

The signal transmission subsystem includes:

The electrical-to-optical module is used to convert the clock signal and SYNC signal in the form of electrical signal into optical signal.

The optical fiber transmission module uses optical fiber to distribute the clock signal and SYNC signal from the local data processing center to different remote measurement nodes.

The optical-to-electrical module is used to receive the optical signal of the optical fiber transmission module and convert it into an electrical signal.

The clock phase adjustment subsystem includes:

The phase-locked loop module is used to compare the phase difference between the transmitted clock and the received clock, output an adjustment voltage proportional to the phase difference, and control the variable phase delay module.

The variable phase delay module has a variable phase delay module on the clock sending link and the clock receiving link respectively, and the module is controlled by the regulation voltage of the phase locked loop module to delay the phase of the input clock signal.

The SYNC resampling subsystem exists on each remote measurement node, receives the clock signal and the SYNC signal sent by the local data processing center, and aligns the phases of the SYNC signal and the clock signal. Output a new SYNC signal and send it back to the local data processing center.

All remote measurement nodes regard the received SYNC signal as a trigger event, and when the trigger event occurs, the remote measurement nodes start to execute corresponding measurement and control tasks. The system has no limit to the number of remote measurement nodes, and there is no limit to the distance between different remote measurement nodes and the local data processing center. Each remote measurement node forms a clock signal and SYNC signal sending and receiving loop with the local data processing center. There is no data exchange between each remote measurement node. The clock and SYNC signal synchronization between all remote measurement nodes is completed by the local data processing center.

Further, in the SYNC distribution and receiving module, the measurement method of the number of clock cycles experienced by the SYNC signal is: while sending SYNC, the SYNC distribution and receiving module clears the internal counter, and at each clock signal A rising edge increments the counter by 1. When the SYNC distribution and receiving module receives the SYNC signal sent back by the remote measurement node, the counter stops accumulating, and sends the value of the counter to the clock cycle delay distribution module to adjust the cycle delay number of each clock output.

Furthermore, in the signal transmission subsystem, a total of 4 types of signals need to be transmitted through optical fibers, that is, the clock signal and SYNC signal sent by the local data processing center to the remote measurement node, and the remote measurement node sends back to the local data processing Central clock signal, SYNC signal. The optical fiber transmission module has two physical implementations. One is to use wavelength division multiplexing technology to modulate the four signals onto carriers of different wavelengths and transmit them on an optical fiber. The structure is relatively complicated. But it can save the number of optical fibers; the second is to modulate the four signals to the same wavelength carrier and transmit them on different optical fibers respectively. The structure is simple, but it is necessary to ensure that the four optical fibers are of equal length.

Finally, the clock and SYNC processing subsystem runs on the local data processing center, the signal transmission subsystem runs on the local data processing center and remote measurement nodes, the clock phase adjustment subsystem runs on the local data processing center, and the SYNC resampling sub-system The system runs on remote measurement nodes.

The method applicable to the aforementioned optical fiber transmission channel clock synchronization system includes the following steps:

Step 1. After the entire system is reset and powered on, the global reference clock input clock cycle delays the distribution module 2 . SYNC distribution and receiving module 1 sets the output delay of clock cycle delay distribution module 2 to 0, and clock cycle delay distribution module 2 outputs each reference clock without delay, and one reference clock enters SYNC distribution and receiving module 1, and one reference clock Enter the phase-locked loop module 3 and the variable phase delay module 4a.

Step 2. The reference clock signal entering the variable phase delay module 4a will be sent to the remote measurement node through the electrical-to-optical module 6a, the optical fiber 7a, and the optical-to-electrical module 5a. The remote measurement node obtains the reference clock signal from the output port of the optical-to-electrical module 5a, and uses it as the reference clock basis of the entire node. In addition, the reference clock is divided into two paths, one path is input to the SYNC resampling module 8, the other path is entered into the electrical-to-optical module 6b, and is sent back to the local data processing center through optical fiber.

Step 3. Due to the randomness of the optical fiber length, the phase difference between the two input signals of the phase-locked loop module 3 is randomly distributed between 0° and 360°. The phase detector inside the phase locked loop module 3 compares the phase difference between the two input signals and generates a signal proportional to the phase difference. Subsequently, the loop filter inside the phase-locked loop module 3 averages the DC signal containing ripple components output by the phase detector, and changes this into a DC signal with less AC components, ranging from 0 to 5V, and the phase-locked loop module The final stage is an active loop filter formed by operational amplifiers. There are two options for this structure, inverting topology and non-inverting topology. The input impedance of the inverting topology is low, which is equivalent to adding a load to the previous stage, which changes the loop characteristics of the phase-locked loop module; the input impedance of the non-inverting topology is high, which will not make the previous stage bear the load; but using the inverting When the topology is used, the phase detector in the phase-locked loop module must have a polarity inversion function to offset the phase inversion effect brought by the inverting topology. Drive the variable phase delay block 4 with the correct polarity. The active loop filter amplifies the input DC signal of 0-5V into a DC signal of 0-12V, and simultaneously inputs the two variable phase delay modules 4a, 4b.

Step 4: The variable phase delay modules 4a and 4b change the phase delay amount according to the magnitude of the input DC signal, so that the output clocks of the variable phase delay modules 4a and 4b have a phase delay in the range of 0-180° relative to the input clock. When the DC signal value is 0V, the phase delay of the variable phase delay module 4 is 0°, and when the DC signal value is 12V, the phase delay of the variable phase delay module 4 is slightly greater than 180°; from the local data processing center There is a variable phase delay module 4a on the path to the remote measurement node, and there is also a variable phase delay module 4b on the path from the remote measurement node to the local data processing center. The entire clock transmission loop contains two variable phase delay modules 4a The variable phase delay modules 4a and 4b can cover the clock phase offset of a complete cycle of 0-360°.

Step 5. When the variable phase delay modules 4a and 4b change their own phase delays, the phase of the reference clock reference signal on the remote measurement node also changes correspondingly. Until the phase difference of the two input signals of the phase-locked loop module 3 is 0°, the output DC signal of the phase-locked loop module 3 no longer changes, and the phase delays of the variable phase delay modules 4a, 4b also no longer change. The reference clock reference signal of the remote measurement node is phase-aligned with the reference clock output by the clock cycle delay distribution module 2 .

Step 6. Due to the inconsistency of the optical fiber length, the 10MHz reference clock sent by the remote local data processing center needs to go through different clock cycles on the optical fiber to reach each remote measurement node. At this time, the system needs to start the SYNC distribution and reception module 1 to measure the number of clock cycles. The SYNC distribution and receiving module 1 sets the SYNC signal high at the rising edge of the reference clock, and starts an internal counter at the same time, and adds 1 to the value of the counter at each rising edge of the reference clock. The electrical-to-optical module 6c converts the SYNC signal into an optical signal, and transmits it to a remote measurement node through an optical fiber. The optical-to-electrical module 5c converts the SYNC signal into an electrical signal, and sends it to the SYNC resampling module 8 . Since the SYNC signal sent by the SYNC distribution and receiving module 1 is aligned with the rising edge of the reference clock, the link sending the reference clock has one more variable phase delay module 4a than the link sending SYNC, so that the The reference clock lags behind the SYNC signal by a random phase in the range of 0 to 180°. The function of the SYNC resampling module 8 on the remote measurement node is to eliminate this random phase deviation, so that the output SYNC signal is re-aligned with the rising edge of the reference clock. , as shown in Figure 5. SYNC is sent back to the SYNC distribution and receiving module 1 of the local data processing center. At this time, the SYNC distribution and receiving module 1 stops the internal counter, and the current value of the counter is twice the number of clock cycles experienced by the reference clock on a single optical fiber. .

Step 7, SYNC distribution and receiving module 1 obtains the number of clock cycles experienced on the optical fiber interconnected between all remote measurement nodes and the local data processing center according to step 6, and calculates the clock cycle delay of each output clock port of the distribution module 2 relative to The number of cycle delays of the global reference clock. For example, when the length of the optical fiber interconnecting the first remote measurement node and the local data processing center is 65 meters, and the length of the optical fiber interconnecting the second remote measurement node and the local data center is 85 meters, the SYNC distribution and receiving module 1 measures The number of clock cycle delays corresponding to the first remote measurement node is 8, and the number of clock cycle delays corresponding to the second remote measurement node is 10. At this time, the clock cycle delay distribution module 2 sets the cycle delay number of each output port to compensate the inconsistency of the clock cycle delay number brought by the optical fiber. If the clock cycle delay distribution module 2 outputs the delay to the first remote measurement node The number is N1, and the delay number output to the second remote measurement node is N2, then 8+N1=10+N2 is satisfied.

The beneficial effects of the present invention are mainly manifested in:

1) The present invention does not need to add an additional optical fiber transmission channel, and only relies on the phase-locked loop and variable phase delay module on the optical fiber clock transmission channel to realize the edge alignment of all remote measurement nodes and the clock signal of the local data processing center Function;

2) The clock cycle inconsistency correction function between all remote measurement nodes can be completed only by using the SYNC signal and the clock signal;

3) The SYNC signal can also be used as a trigger command for all remote measurement nodes to complete the synchronous sampling and output functions of all nodes;

4) The present invention can adapt to optical fiber transmission channels of various lengths, adopts optical fiber as the transmission medium, and has strong anti-electromagnetic interference and confidentiality; no physical electrical connection is required between nodes, the system structure is simple, and engineering implementation is easy.

Description of drawings

Fig. 1 is a schematic diagram of the optical fiber transmission channel clock synchronization system of the present invention.

Fig. 2 is a schematic diagram of the layout and interconnection of the calibration module of the present invention, wherein the thin solid line represents the clock path, and the thin dotted line represents the SYNC path.

FIG. 3 is an inverting topology of the active loop filter of the present invention.

Fig. 4 is a non-inverting topology of the active loop filter of the present invention.

Fig. 5 is a functional schematic diagram of the SYNC resampling module of the present invention.

Fig. 6 is the relationship between the control voltage of the controllable phase delay module and the amount of phase delay.

Detailed ways

The invention will be further described below in conjunction with the accompanying drawings.

A common application scenario of the present invention is shown in FIG. 1 . There are a plurality of discretely distributed remote measurement nodes in the system, and they are respectively interconnected with a local data processing center through optical fibers of unequal length. The local data processing center is responsible for transmitting the clock signal and the SYNC signal as a trigger event to all remote measurement nodes. The system requires that the clocks reaching all remote measurement nodes maintain phase consistency, and all SYNC signals can reach all remote measurement nodes at the same time.

Referring to Fig. 1 and Fig. 2, a kind of optical fiber transmission channel clock synchronization system includes: clock and SYNC processing subsystem for distributing clock and SYNC signal for different remote nodes, optical/electrical, electrical/optical conversion and The signal transmission subsystem for transmission, the clock phase adjustment subsystem for adjusting the clock phase in real time, and the SYNC resampling subsystem for completing phase realignment of clock and SYNC.

The clock and SYNC processing subsystem includes: clock cycle delay distribution module 1, SYNC distribution and receiving module 2; signal transmission subsystem includes: electrical to optical module 6, optical fiber transmission module 7, optical to electrical module 5; clock phase adjustment subsystem It includes: a phase-locked loop module 3 and a variable phase delay module 4.

Since the structures of all remote measurement nodes are the same, only one remote measurement node is described. The method is also applicable to other remote measurement nodes.

The clock cycle delay distribution module 2 of Fig. 2 produces a system reference clock signal, and simultaneously sends it to the first input port of the SYNC distribution and receiving module 1, the first input port of the phase-locked loop module 3, and the input port of the variable phase delay module 4a ; The clock signal output by the variable phase delay module 4a reaches the remote measurement node after passing through the electrical-to-optical module 6a, the optical fiber transmission channel 7a, and the optical-to-electrical module 5a; the remote measurement node divides the CLK signal into 3 paths, and one path is used as a remote The reference clock of the measurement node enters the first input port of the SYNC resampling module 8 one way, and the other way enters the phase-locked loop module after passing through the electrical-to-optical module 6b, the optical fiber transmission channel 7b, the optical-to-electrical module 5b, and the variable phase delay module 4b The second input port of 3; the phase-locked loop module 3 controls the two variable phase delay modules 4a by comparing the phase difference of the clock signal of the first input port and the second input port, outputting an adjustment voltage proportional to the phase difference , 4b, thereby changing the phase shift amount of the two variable phase delay modules 4a, 4b until the phase difference between the signals of the two input ports of the phase-locked loop module 3 is 0, and the whole loop is in a state of dynamic balance, and the variable phase The phase shift of the delay modules 4a and 4b no longer changes, and the phase difference between the reference clock of the remote measurement node and the reference clock of the local data processing center is 0; due to the use of multiple groups of remote measurement nodes, different measurement nodes use unequal lengths The optical fiber is connected to the local data processing center. The above method can ensure that the phase difference between the reference clock of each remote measurement node and the reference clock of the local data processing center is 0, but the unequal length of the optical fiber will lead to A reference clock needs to go through different numbers of reference clock cycles to reach different remote measurement nodes; when the number of cycles needs to be measured and corrected, the SYNC distribution and receiving module 1 generates a SYNC signal, which is aligned with the rising edge of the reference clock; The SYNC signal enters the second input port of the SYNC resampling module 8 on the far-end measurement node after passing through the electrical-to-optical module 6c, the optical fiber transmission channel 7c, and the optical-to-electrical module 5c; the reference clock of the SYNC resampling module 8 at the first input port The rising edge of the second input port SYNC signal is resampled to eliminate the phase difference between the reference clock and SYNC brought by the variable phase delay module 4a; the new SYNC signal output by the SYNC resampling module 8 is divided into two paths, one path As the SYNC signal on the remote measurement node, the other path enters the SYNC distribution and receiving module 1 through the electrical-to-optical module 6d, the optical fiber transmission channel 7d, and the optical-to-electrical module 5d; the SYNC distribution and receiving module 1 records the difference between sending SYNC and receiving SYNC The number of reference clocks between the local data processing center and different remote measurement nodes can be known; the SYNC distribution and receiving module 1 controls the clock cycle delay distribution module 2 to make the clock cycle delay distribution module 2 for Different remote measurement nodes compensate for different clock cycle delays, and finally make different remote measurement nodes relative to the global reference clock9 have the same amount of reference clock cycle delay.

See Figure 1. In the embodiment described below, the optical fiber transmission channel clock synchronization system includes a local data processing center and multiple remote measurement nodes, and each node uses a group of 4 optical fibers to communicate with the local data processing center for clock transmission and SYNC control. The lengths of each group of optical fibers are not equal, and the 4 optical fibers inside each group of optical fibers are guaranteed to be of equal length. The local data processing center needs to transmit the 10MHz reference clock to the remote measurement node. Since the length of the optical fiber interconnected with the local data processing center is distributed from 60 meters to 120 meters, the signal transmission rate in the optical fiber is about 2×10 ⁸ m/s , so the wavelength of the 10MHz clock is about 2×10 ⁸ /(10×10 ⁶ )m=20m, which is equivalent to a clock signal with 3 to 6 periods on the optical fiber. Even if the local data processing center distributes the reference clock to different remote measurement nodes at the same time, the reference clock will reach different remote measurement nodes at different times through the effect of unequal-length optical fibers, resulting in different remote measurement Clocks are not synchronized between nodes. The same problem also exists in the SYNC signal, because the SYNC signal is used to send synchronization signals to different remote measurement nodes. The SYNC signals between remote measurement nodes are not synchronized.

Taking the first remote measurement node and the local data processing center as an example, referring to Figure 2, the specific implementation steps are as follows:

1. After the entire system is reset and powered on, the global reference clock input clock cycle delays the distribution module 2 . The SYNC distribution and receiving module 1 sets the output delay of the clock cycle delay distribution module 2 to 0, and the clock cycle delay distribution module 2 outputs each reference clock without delay, and one reference clock enters the SYNC distribution and receiving module 1, and one reference clock Enter the phase-locked loop module 3 and the variable phase delay module 4a.

2. The reference clock signal entering the variable phase delay module 4a will be sent to the remote measurement node through the electrical-to-optical module 6a, the optical fiber 7a, and the optical-to-electrical module 5a. The remote measurement node obtains a reference clock signal from the output port of the optical-to-electrical module 5a, and uses it as a reference clock reference for the entire node. In addition, the reference clock is divided into two channels, one channel is input to the SYNC resampling module 8, and the other channel is input to the electrical-to-optical module 6b, and is sent back to the local data processing center through an optical fiber.

3. Due to the randomness of the optical fiber length, the phase difference between the two input signals of the phase-locked loop module 3 is randomly distributed between 0° and 360°. The phase detector inside the phase locked loop module 3 compares the phase difference between the two input signals and generates a signal proportional to the phase difference. Subsequently, the loop filter inside the phase-locked loop module 3 averages the DC signal containing ripple components output by the phase detector, and changes this into a DC signal with less AC components, ranging from 0 to 5V, and the phase-locked loop module The final stage is an active loop filter formed by operational amplifiers. There are two options for this structure, inverting topology and non-inverting topology. The input impedance of the inverting topology is low, which is equivalent to adding a load to the previous stage and changing the loop characteristics of the phase-locked loop module, as shown in Figure 3. The input impedance of the non-inverting topology is high, which will not cause the pre-stage to bear the load, as shown in Figure 4. However, when an inverting topology is used, the phase detector in the phase-locked loop module must have a polarity inversion function to offset the phase inversion effect brought by the inverting topology. Drive the variable phase delay block 4 with the correct polarity. The active loop filter amplifies the input DC signal of 0-5V into a DC signal of 0-12V, and simultaneously inputs the two variable phase delay modules 4a and 4b.

4. The variable phase delay modules 4a, 4b change the phase delay amount according to the magnitude of the input DC signal, so that the output clock of the variable phase delay module 4a, 4b produces a phase delay in the range of 0-180° relative to the input clock. When the DC signal value is 0V, the phase delay of the variable phase delay module 4 is 0°, and when the DC signal value is 12V, the phase delay of the variable phase delay module 4 is slightly greater than 180°. The relationship between the control voltage of the variable phase delay module and the amount of phase delay is shown in Fig. 6 . Because there is a variable phase delay module 4a on the path from the local data processing center to the remote measurement node, and there is also a variable phase delay module 4b on the path from the remote measurement node to the local data processing center, the entire clock transmission loop It includes two variable phase delay modules 4a, 4b, which can cover the clock phase offset of a complete cycle of 0-360°.

5. When the variable phase delay modules 4a and 4b change their own phase delays, the phase of the reference clock reference signal on the remote measurement node also changes correspondingly. Until the phase difference of the two input signals of the phase-locked loop module 3 is 0°, the output DC signal of the phase-locked loop module 3 no longer changes, and the phase delays of the variable phase delay modules 4a, 4b also no longer change. The reference clock reference signal of the remote measurement node is phase-aligned with the reference clock output by the clock cycle delay distribution module 2 .

6. Due to the inconsistency of the length of the optical fiber, the 10MHz reference clock sent by the remote local data processing center needs to go through different clock cycles on the optical fiber to reach each remote measurement node. At this time, the system needs to start the SYNC distribution and reception module 1 to measure the number of clock cycles. The SYNC distribution and receiving module 1 sets the SYNC signal high at the rising edge of the reference clock, and starts an internal counter at the same time, and adds 1 to the value of the counter at each rising edge of the reference clock. The electrical-to-optical module 6c converts the SYNC signal into an optical signal, and transmits it to a remote measurement node through an optical fiber. The optical-to-electrical module 5c converts the SYNC signal into an electrical signal, and sends it to the SYNC resampling module 8 . Since the SYNC signal sent by the SYNC distribution and receiving module 1 is aligned with the rising edge of the reference clock, the link sending the reference clock has one more variable phase delay module 4a than the link sending SYNC, so that the The reference clock lags behind the SYNC signal by a random phase in the range of 0 to 180°. The function of the SYNC resampling module 8 on the remote measurement node is to eliminate this random phase deviation, so that the output SYNC signal is re-aligned with the rising edge of the reference clock. , as shown in Figure 5. SYNC is sent back to the SYNC distribution and receiving module 1 of the local data processing center. At this time, the SYNC distribution and receiving module 1 stops the internal counter, and the current value of the counter is twice the number of clock cycles experienced by the reference clock on a single optical fiber. .

7. According to step 6, SYNC distribution and receiving module 1 obtains the number of clock cycles experienced on the optical fiber interconnected between all remote measurement nodes and the local data processing center, and calculates the clock cycle delay of each output clock port of distribution module 2 relative to the global The number of cycle delays of the reference clock. For example, when the length of the optical fiber interconnecting the first remote measurement node and the local data processing center is 65 meters, and the length of the optical fiber interconnecting the second remote measurement node and the local data center is 85 meters, the SYNC distribution and receiving module 1 measures The number of clock cycle delays corresponding to the first remote measurement node is 8, and the number of clock cycle delays corresponding to the second remote measurement node is 10. At this time, the clock cycle delay distribution module 2 sets the cycle delay number of each output port to compensate the inconsistency of the clock cycle delay number brought by the optical fiber. If the clock cycle delay distribution module 2 outputs the delay to the first remote measurement node The number is N1, and the delay number output to the second remote measurement node is N2, then 8+N1=10+N2 is satisfied.

8. Since the optical fiber used by the SYNC signal and the reference signal is the same length, the propagation time of the SYNC signal and the reference clock on the optical fiber is the same, the SYNC distribution and receiving module 1 can use the number of clock cycles experienced by the reference clock signal on the optical fiber to adjust the transmission SYNC signals sent to different remote measurement nodes are sent at intervals so that all SYNC signals can reach all remote measurement nodes at the same time.

The content described in the embodiments of this specification is only an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments. Equivalent technical means that a person can think of based on the concept of the present invention.

Claims (5)

1. a kind of optical fiber transport channel clock system, it is characterised in that：The clock system includes：For different distal ends Node distribute the clock of clock and SYNC signal with SYNC processing subsystems, for complete the optical electrical of signal, electrical/optical conversion and The signal transmission subsystem of transmission, for adjust in real time the clock phase of clock phase adjust subsystem, for complete clock and The SYNC resampling subsystems that the phase of SYNC is alignd again；

Wherein, the clock includes with SYNC processing subsystems：

Clock cycle delay distribution module, for providing clock signal all the way for each far-end measuring node.Prolong with output The phase detuning selection function of slow coarse adjustment, minimum delay stepping are equal to the half of input clock cycle, and each output clock can To be separately provided retardation, the value of the clock output retardation of the module is determined by SYNC distributions and receiving module；

SYNC distributes and receiving module, for providing SYNC signal all the way for each far-end measuring node, while receives each The SYNC signal that a far-end measuring node postbacks；The module, which is measured, sends and receives the clock cycle that SYNC signal is undergone Number, clock periodicity determine clock cycle delay distribution module per the retardation exported all the way；

The signal transmission subsystem includes：

Electricity turns optical module, for existing clock signal, SYNC signal in electrical signal form to be converted into optical signal；

Optical fiber transmission module using optical fiber, from local data processing center is distributed to clock signal, SYNC signal different remote Hold measuring node；

Light turns electric module, for the optical signal of reception optical fiber transport module, and is converted to electric signal；

The clock phase, which adjusts subsystem, to be included：

Phase-locked loop module, for comparing the phase difference between the clock of transmission, the clock received, output is directly proportional to the phase difference Adjusting voltage, control variable phase delay module；

Variable phase delay module, it is each there are one variable phase delay module in clock transmission link and clock receives link, The module is adjusted controlling for voltage by phase-locked loop module, and phase delay is carried out to the clock signal of input；

The SYNC resampling subsystems, are present on each far-end measuring node, receive local data processing center hair The clock signal and SYNC signal brought, and SYNC signal and clock signal are carried out phase alignment；Export new SYNC letters Number return to local data processing center；

Far-end measuring node is using the SYNC signal received as trigger event, when the triggering event occurs, far-end measuring node Start to perform corresponding TT＆C task；Far-end measuring node all forms clock signal, SYNC signal with local data processing center Transmitting-receiving circuit；There is no data exchange between far-end measuring node；By local data processing center complete far-end measuring node it Between clock it is synchronous with SYNC signal.

2. optical fiber transport channel clock system as described in claim 1, it is characterised in that：The SYNC distributions and reception The mode of clock periodicity of module measurement SYNC signal experience is：While SYNC is sent, SYNC distributions and receiving module Internal counter is reset, and the value of counter is added 1 in the rising edge of each clock signal；When SYNC distributions and receiving module When receiving the SYNC signal that far-end measuring node postbacks, counter stops adding up, and the value of counter is sent to the clock cycle Postpone distribution module, the cycle delay number per the output of clock all the way is adjusted.

3. optical fiber transport channel clock system as described in claim 1, it is characterised in that：The signal transmission subsystem In system, sharing 4 class signals needs to be transmitted by optical fiber, i.e., local data processing center be sent to far-end measuring node when Clock signal, SYNC signal, clock signal of the far-end measuring node back to local data processing center, SYNC signal.

4. optical fiber transport channel clock system as described in claim 1, it is characterised in that：Clock handles subsystem with SYNC System is operated in local data processing center, and signal transmission subsystem operates in local data processing center and far-end measuring node On, for clock phase regulator system operation in local data processing center, SYNC resampling subsystems operate in far-end measuring On node.

5. suitable for the method for optical fiber transport channel clock system described in claim 1, include the following steps：

Step 1, whole system reset after the power is turned on, global reference clock input clock cycle delay distribution module (2)；SYNC distributes The output retardation of clock cycle delay distribution module (2) is arranged to 0 with receiving module (1), clock cycle delay distribution mould Block (2) is exported without delay per reference clock all the way, and reference clock enters SYNC distributions and receiving module (1) all the way, joins all the way It examines clock and enters phase-locked loop module (3), variable phase delay module (4a)；

Step 2, the reference clock signal into variable phase delay module (4a) will turn optical module (6a), optical fiber by electricity (7a), light turn electric module (5a) and are sent to far-end measuring node；The delivery outlet that far-end measuring node turns electric module (5a) from light obtains Reference clock signal is obtained, and in this, as the reference clock benchmark of entire node；The reference clock will additionally be divided into two-way, and one Road input SYNC resamplings module (8), another way enter electricity and turn optical module (6b), and pass through fiber pass-back and give local data processing Center；

Step 3, the randomness due to fiber lengths, the phase difference between two input signals of phase-locked loop module (3) divide at random It is distributed between 0 °~360 °；The internal phase discriminator of phase-locked loop module (3) compares the phase difference between two input signals, generates one A signal proportional to the phase difference；The internal loop filter of subsequent phase-locked loop module (3) contains what phase discriminator exported This variation is the less direct current signal of alternating component by the direct current signal equalization of ripple component, and scope is 0~5V, phaselocked loop The afterbody of module is the active loop wave filter that operational amplifier is formed；There are two types of selection, inversion topologies for the structure With positive topological structure；The input impedance of inversion topology is low, is equivalent to and adds load to previous stage, changes phaselocked loop The loop characteristics of module；Input impedance with phase topological structure is high, and prime will not be made to bear to load；Use inversion topology When, the phase discriminator in phase-locked loop module must have the function of polarity inversion, to offset the phasing back that inversion topology is brought Effect；With correct polarity driven variable phase delay module 4；Active loop wave filter puts 0~5V direct current signals of input Greatly 0~12V DC signal, while input two variable phase delay modules (4a, 4b)；

Step 4, variable phase delay module (4a, 4b) change phase-delay quantity according to the size of the direct current signal of input, and making can The output clock of changeable phases Postponement module (4a, 4b) generates the phase delay in the range of 0~180 ° compared with input clock；When straight When stream signal value is 0V, the phase-delay quantity of variable phase delay module (4) is 0 °, can be covert when direct current signal value is 12V The phase-delay quantity of position Postponement module (4) is slightly larger than 180 °；Path from local data processing center to far-end measuring node has 1 A variable phase delay module (4a), from far-end measuring node to also have on the path of local data processing center 1 can be covert Position Postponement module (4b) just comprising two variable phase delay modules (4a, 4b) on entire clock transfer circuit, can cover 0 The clock phase offset of~360 ° of complete cycles；

Step 5, when variable phase delay module (4a, 4b) changes the phase-delay quantity of itself, the ginseng on far-end measuring node The phase for examining clock reference signal also changes accordingly；Until the phase difference of two input signals of phase-locked loop module (3) For 0 °, the output direct current signal of phase-locked loop module (3) no longer changes at this time, and the phase of variable phase delay module (4a, 4b) is prolonged Amount also no longer changes late, reference clock reference signal and clock cycle delay distribution module (2) output of far-end measuring node Reference clock phase alignment；

Step 6, the inconsistency due to fiber lengths, the 10MHz references that distal end local data processing center can also be brought to send Clock needs undergo different clock periodicities on optical fiber and get to each far-end measuring node；System needs to start at this time SYNC distributes and receiving module 1 measures clock periodicity；SYNC distributes the rising edge in reference clock with receiving module (1), will SYNC signal puts height, while starts internal counter, and the value of counter is added 1 in the rising edge of each reference clock；Electricity Turn optical module (6c) and the SYNC signal is converted into optical signal, and pass through optical fiber and be transferred to far-end measuring node, electric mould is turned by light SYNC signal is become electric signal by block (5c), and is sent into SYNC resamplings module (8)；Due to SYNC distributions and receiving module (1) The SYNC signal of transmission aligns with the rising edge of reference clock, and the link for sending reference clock is more than the link for sending SYNC One variable phase delay module (4a), so as to get up to far-end measuring node reference clock lagged 0 than SYNC signal~ Random phase in the range of 180 °, SYNC resamplings module (8) effect on far-end measuring node is to eliminate this random phase Deviation so that the SYNC signal of output realizes the rising edge alignment with reference clock again；SYNC is returned at local data again The SYNC distributions at reason center and receiving module (1), SYNC distributions at this time and receiving module (1) stop internal counter, counter Currency be twice of the clock periodicity that reference clock is undergone on simple optical fiber；

Step 7, SYNC distributions and receiving module (1) obtain all far-end measuring nodes according to step 6 and local data is handled The clock periodicity undergone on the optical fiber of hub interconnection, calculating clock cycle delay distribution module (2), each exports clock Port compared with global reference clock cycle delay number；Clock cycle delay distribution module (2) sets each output terminal at this time The cycle delay number of mouth, the inconsistency for the clock cycle delay number that compensated optical fiber is brought, if time clock cycle delay distributes mould It is N1 that block (2), which is exported to the delay number of the first far-end measuring node, and it is N2 to export to the delay number of the second far-end measuring node, that Meet 8+N1=10+N2；

Step 8, due to optical fiber used in SYNC signal and reference signal it is isometric, SYNC signal and reference clock are on optical fiber Propagation time is the same, and SYNC distributions and receiving module (1) can utilize the clock cycle that reference clock signal is undergone on optical fiber Number adjusts the SYNC signal transmission interval for being sent to different far-end measuring nodes so that all SYNC signals can be same Time reaches all far-end measuring nodes.