A high-precision time-providing device for fiber-optic hydrophone array system

Abstract

The application discloses a high-precision time service device for an optical fiber hydrophone array system, and belongs to the field of hydrophones, which comprises: a time synchronization receiving module, which is used for receiving time service information and generating a synchronization clock signal CLK, a synchronization second pulse signal PPS and absolute time information TOD; an optical path delay measuring module, which is used for measuring optical path delay; an algorithm delay measuring module, which is used for measuring algorithm delay; a time offset calibration module, which is used for measuring the sum of physical offset and packet delay; and a high-precision time service module, which is used for marking absolute time on output data according to the absolute time information TOD, optical path delay, algorithm delay, physical offset and packet delay. The application calculates the specific value of lag through the corresponding time delay calibration module, accurately calibrates and revises the TOD time input by the time service slave machine, realizes high-precision time service calibration of absolute time of optical fiber hydrophone array data, and the time service precision is less than 2us.

Description

Technical Field

[0001] This invention relates to the field of fiber optic hydrophones, and in particular to a high-precision timing device for fiber optic hydrophone array systems. Background Technology

[0002] Fiber optic hydrophones (FOHs) are a new type of underwater acoustic sensor based on fiber optic and optoelectronic technologies, using fiber optics as the information transmission and sensing medium. They have important applications in military and civilian fields such as underwater target detection, oil and gas exploration, and seismic detection. FOHs are characterized by high sensitivity, large dynamic range, strong resistance to electromagnetic interference, compact structure, and ease of large-scale arraying. They are also suitable for various harsh environments, leading to a variety of applications such as shore-based arrays, towed arrays, flank arrays, and submersible / buoy arrays. They have become an important development direction for modern fiber optic sensing technology and underwater acoustic sensing technology.

[0003] In practical engineering applications, to improve the detection capabilities of fiber optic hydrophones, multi-channel fiber optic hydrophone detection arrays are typically constructed using spatial division, wavelength division, or time division arrays. Furthermore, multiple arrays can be organically combined into ultra-large-scale underwater detection arrays to further enhance the detection capabilities of underwater sound fields. Moreover, with the increasing diversity of detection needs, passive underwater acoustic detection using a single all-fiber optic hydrophone is no longer sufficient. More and more detection instruments and platforms are being integrated for collaborative detection, forming comprehensive underwater detection networks.

[0004] When different types of detection equipment form a large-scale detection network for collaborative underwater detection, the data from the detectors need to carry absolute time information to achieve data fusion and maximize efficiency. Therefore, it is necessary to mark the absolute time on the output data of the detection equipment in real time, and the higher the absolute time accuracy, the more beneficial it is to data fusion. Currently, network time servers are widely used in fiber optic hydrophone array engineering applications to provide time synchronization for the fiber optic hydrophone arrays. However, the smallest time scale provided by the time synchronization server is in seconds. If it is directly injected into the data packet without processing, its accuracy cannot meet the requirements of engineering use.

[0005] The workflow of the fiber optic hydrophone array system is as follows:

[0006] 1. The timing master receives and locks onto BeiDou satellite signals via an antenna, and then transmits the timing information to the timing slave via a switch and network cable using the PTP timing protocol (or other protocols), thereby realizing network timing functionality. Since the timing master tracks and locks onto the satellite, its output time signal is a standard absolute time from the satellite. The timing master can only provide stable and reliable synchronization time information after locking onto the satellite.

[0007] 2. After receiving the time signal from the time master, the time slave device generates a local synchronization clock signal (CLK, e.g., 10MHz), a synchronization second pulse signal (PPS), and an absolute year, month, day, hour, minute, and second signal (TOD) from the timing information in the time master device using a certain algorithm. Figure 1 As shown in the figure, the synchronization accuracy between the PPS signal in the timing slave and the PPS signal in the timing master is within 100ns. The PPS signal has no accumulated error and can be used as trigger information for the subsequent fiber optic hydrophone array system. The time signal TOD is the accurate physical time.

[0008] 3. Of the three signals (CLK, TOD, PPS) generated by the timing slave, CLK and PPS signals are generally connected to the FPGA signal processing system via RF cables, while the TOD signal is typically connected using protocols such as TTL, 232, or 485. The CLK signal serves as the master clock source for the FPGA signal processing system. The FPGA board uses an onboard clock chip and clock distribution chip to multiply and divide the input CLK clock before distributing it to the FPGA chip and ADC chip, thus synchronizing the clock between the FPGA signal processing board and the timing slave. The PPS and TOD signals are connected to the FPGA signal processing system, with the TOD signal lagging behind the PPS signal. This lag time interval is called the actual physical delay (Time_pps_tod_delay). Figure 2 As shown;

[0009] 4. The PPS signal is the original trigger pulse. When the rising edge of PPS arrives, it triggers the FPGA signal processing system to synchronously generate a modulation pulse signal TRIG. This modulation pulse signal TRIG can control the acousto-optic modulator in the FPGA signal processing system to generate the periodic interrogation optical pulses required for the operation of the fiber optic hydrophone array system. After these periodic interrogation optical pulses are transmitted to the fiber optic hydrophone array via the transmission optical path, they will return as array optical pulse signals, such as... Figure 2 As shown;

[0010] The time delay between the generation of the modulation pulse signal TRIG and the return of the corresponding array optical pulse to the signal processing system is called the optical path delay (Time_pulse_delay).

[0011] 5. When the array optical pulse signal enters the FPGA signal processing system, the board based on the FPGA chip will perform algorithm demodulation processing on the array optical pulse signal to recover the external information carried in the array optical pulse. The time delay between these two is the algorithm delay (Time_demo_delay).

[0012] 6. The PPS signal is the original trigger pulse. When the rising edge of PPS arrives, it triggers the FPGA signal processing system to generate the modulation pulse signal TRIG, and at the same time, it also triggers the FPGA signal processing system to read the TOD data sent by the timing slave and pack the TOD data into the demodulated output data. However, at this time, the demodulated result data may still be in the process of being generated, that is, the demodulated result data is not ready. Therefore, there is a time delay from the arrival of the rising edge of PPS to the accurate packing of the TOD data into the demodulated result data. This time delay is called the packet assembly delay (Time_assemble_delay).

[0013] In summary, the workflow of the fiber optic hydrophone array system and Figure 2 As can be seen, starting from the rising edge of the PPS, the corresponding demodulated data packet (marked by the black block in the figure) will be generated with a certain delay. The total delay time, Time_total_delay, equals the optical path delay (Time_pulse_delay) + the algorithm delay (Time_demo_delay) + the packet assembly delay (Time_assemble_delay). Therefore, the true absolute physical time Time on the demodulated result data packet equals the actual physical delay (Time_pps_tod_delay) + Time_total_delay.

[0014] Due to the existence of the aforementioned time delays, the processing result output by the FPGA signal processing system at a certain moment cannot represent the external sound signal at the current moment. At the same time, considering that the distance between each optical device and the hydrophone array and the FPGA signal processing system will also affect the specific value of the aforementioned optical path delay (Time_pulse_delay), the signal output by the FPGA signal processing system at a certain moment may also be a mixture of external sound signals collected by the fiber optic hydrophone unit at different moments earlier, resulting in a large error in the processing result output by the FPGA signal processing system.

[0015] Therefore, the latency caused by the array and signal processing stages must be eliminated. Only by calibrating the time provided by the time synchronization server can high-precision time synchronization of the data be obtained to meet actual needs. Summary of the Invention

[0016] To address the problem that the demodulation results output by existing fiber optic hydrophone array systems cannot accurately represent the external sound signal at the current moment, the present invention aims to provide a high-precision time synchronization device for fiber optic hydrophone array systems.

[0017] To achieve the above objectives, the technical solution of the present invention is as follows:

[0018] A high-precision time synchronization device for a fiber optic hydrophone array system, wherein the fiber optic hydrophone array system includes a signal processing system and a fiber optic hydrophone array. The signal processing system includes a signal demodulation device, an acousto-optic modulator, and a photoelectric conversion device. The signal demodulation device generates a modulation pulse signal TRIG based on a received synchronization second pulse signal PPS. The acousto-optic modulator generates periodic interrogation light pulses under the control of the modulation pulse signal TRIG. The fiber optic hydrophone array receives the periodic interrogation light pulses and returns a periodic light pulse train. The photoelectric conversion device converts the received periodic light pulse train into a periodic light pulse train signal. The signal demodulation device generates a demodulation result based on the periodic light pulse train signal and packages the absolute time information TOD into the demodulation result to form the output data of the fiber optic hydrophone array. The high-precision time synchronization device comprises:

[0019] The time synchronization receiving module is used to receive time information from the time synchronization device and generate a synchronization clock signal CLK, a synchronization second pulse signal PPS, and absolute time information TOD based on the time synchronization information.

[0020] An optical path delay measurement module is used to measure the optical path delay, which is the time delay from the time the signal processing system emits the modulation pulse signal TRIG to the time it receives the periodic optical pulse train signal.

[0021] An algorithm delay measurement module is used to measure the algorithm delay, which is the time delay from when the signal processing system receives the periodic optical pulse train signal to when it generates the demodulation result;

[0022] The time offset calibration module is used to measure the sum of physical offset and packet delay. The physical offset is the time delay between the synchronization second pulse signal PPS and the absolute time information TOD. The packet delay is the time delay from the generation of the demodulation result by the signal processing system to the packetization of the absolute time information TOD into the demodulation result.

[0023] And a high-precision time synchronization module, used to mark the output data with absolute time based on the absolute time information TOD, the optical path delay, the algorithm delay, the physical offset, and the packet assembly delay.

[0024] In a preferred embodiment, the step of the optical path delay measurement module measuring the optical path delay includes:

[0025] S1, when the rising edge of the synchronization second pulse signal PPS arrives, the signal processing system is triggered to generate the modulation pulse signal TRIG. At the same time, the COUNT_PULSE counter in the optical path delay measurement module starts counting synchronously.

[0026] S2, when the periodic optical pulse train signal corresponding to the modulation pulse signal TRIG is detected to arrive, the COUNT_PULSE counter stops counting and the count value is N;

[0027] S3, the optical path delay is the product of the clock frequency F of the COUNT_PULSE counter and the count value N;

[0028] The clock frequency F of the COUNT_PULSE counter is obtained by multiplying and / or dividing the synchronous clock signal CLK.

[0029] In a preferred embodiment, in S1, the time when the rising edge of the synchronization second pulse signal PPS arrives is denoted as time T0, and an enable signal is introduced into the modulation pulse signal TRIG at time T0.

[0030] In S2, starting from time T0, the power of the periodic optical pulse train signal received by the signal demodulation device is detected sequentially. When the detected power value is lower than the set energy threshold and the duration reaches the period T of the synchronous second pulse signal PPS, the count value M of the COUNT_PULSE counter is recorded. The optical path delay is MF-T.

[0031] In a preferred embodiment, the optical path delay measurement module further includes a threshold counter, the clock frequency of which is obtained by multiplying and / or dividing the synchronous clock signal CLK, and the threshold tachymeter is used to record the duration for which the power value of the periodic optical pulse train signal is lower than a set energy threshold.

[0032] In a preferred embodiment, the step of the algorithm delay measurement module measuring the algorithm delay includes:

[0033] S10, Construct a simulation test system, the simulation test system including the fiber optic hydrophone array system and a signal generator, the output end of the signal generator is connected to the input end of the fiber optic hydrophone array, and the input end of the signal generator synchronously receives the synchronous second pulse signal PPS and the absolute time information TOD with the signal demodulation device;

[0034] S20, the signal generator is set as an external clock source, the synchronous second pulse signal PPS is an external trigger source, and the BURST mode is selected. Under the action of the synchronous second pulse signal PPS, the signal generator generates a sine wave signal with a certain number of cycles and loads it into the fiber optic hydrophone array, which is then read by the signal demodulation device. The signal demodulation device also receives and demodulates the optical pulse train signal corresponding to the synchronous second pulse signal PPS.

[0035] S30, the time difference between the moment when the signal demodulation device obtains the demodulation result and the moment when the signal demodulation device reads the sine signal is the sum of the algorithm delay and the optical path delay.

[0036] In a preferred embodiment, when the synchronization second pulse signal PPS arrives, the counter in the algorithm delay measurement module is activated to record the count value cnt_rslt2 when the signal demodulation device obtains the demodulation result and the count value cnt_rslt1 when the signal demodulation device reads the sine signal. The sum of the algorithm delay and the optical path delay is the frequency of the counter in the algorithm delay measurement module multiplied by the difference between cnt_rslt2 and cnt_rslt1.

[0037] In a preferred embodiment, the timing device is a time synchronization module. The time synchronization module obtains standard time information from the satellite and distributes timing data packets to the time synchronization receiving module through the network, so that the time synchronization receiving module can generate a synchronization clock signal CLK, a synchronization second pulse signal PPS, and absolute time information TOD through an algorithm after receiving the timing data packets.

[0038] The beneficial effects of the present invention using the above technical solution are as follows: Accurate calibration of the demodulated output data of the fiber optic hydrophone array system requires a series of measurements and mutual calibrations of TOD (received absolute time information), optical path delay (Time_pulse_delay), algorithm delay (Time_demo_delay), actual physical delay (Time_pps_tod_delay), and packet assembly delay (Time_assemble_delay). Only then can high-precision time synchronization of the demodulated output data of the fiber optic hydrophone array system over a certain distance be achieved at the 2μs level. This enables the system to achieve high-precision time information requirements for sensing and detection units when performing multi-array collaborative detection, multi-base collaborative detection, and collaborative detection of various types of sensors. This has significant application value. The core of this invention is to calculate the specific value of the lag through the corresponding time delay calibration module, thereby accurately calibrating and revising the TOD time input by the timing slave, thus achieving high-precision timing calibration of the absolute time of the fiber optic hydrophone array data. Actual measurements show that the timing accuracy is less than 2μs. This invention has significant application value in meeting the high-precision time information requirements of the sensing and detection units when the system performs multi-array collaborative detection, multi-base collaborative detection, and collaborative detection of various types of sensors. Attached Figure Description

[0039] Figure 1 A schematic diagram of the PPS, CLK, and TOD signals recovered by the timing slave device;

[0040] Figure 2 A schematic diagram illustrating the timing principle of a fiber optic hydrophone array system;

[0041] Figure 3 This is a schematic diagram illustrating the use of a high-precision time synchronization device for a fiber optic hydrophone array system according to the present invention;

[0042] Figure 4 This is a schematic diagram of the operation process of the optical path delay measurement module in this invention;

[0043] Figure 5 This is a schematic diagram of the simulation test system for the algorithm delay determination module built in this invention;

[0044] Figure 6 This is a schematic diagram of the test results of the algorithm delay measurement module in this invention;

[0045] Figure 7 This is a schematic diagram of the operation process of the time offset calibration module in this invention.

[0046] In the diagram: 1-Time synchronization receiving module, 2-Optical path delay measurement module, 3-Algorithm delay measurement module, 4-Time offset calibration module, 5-High-precision time synchronization module, 6-Time synchronization module. Detailed Implementation

[0047] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] A high-precision timing device for a fiber optic hydrophone array system is disclosed. The fiber optic hydrophone array system includes a signal processing system and a fiber optic hydrophone array. The signal processing system includes a signal demodulation device, an acousto-optic modulator, and a photoelectric conversion device. The signal demodulation device generates a modulation pulse signal TRIG based on the received synchronization second pulse signal PPS. The acousto-optic modulator generates periodic interrogation optical pulses under the control of the modulation pulse signal TRIG. After receiving the periodic interrogation optical pulses, the fiber optic hydrophone array returns a periodic optical pulse train. The photoelectric conversion device converts the received periodic optical pulse train into a periodic optical pulse train signal. The signal demodulation device generates a demodulation result based on the periodic optical pulse train signal and packages the absolute time information TOD into the demodulation result to form the output data of the fiber optic hydrophone array.

[0049] In practical applications, due to the existence of actual physical delay (Time_pps_tod_delay), optical path delay (Time_pulse_delay), algorithm delay (Time_demo_delay), and packet assembly delay (Time_assemble_delay), the absolute time information TOD carried in the demodulation result can no longer correspond to the external acoustic signal, and high-precision time synchronization is required.

[0050] like Figure 3 As shown, the high-precision time synchronization device provided in this embodiment includes a time synchronization receiving module 1, an optical path delay measurement module 2, an algorithm delay measurement module 3, a time offset calibration module 4, and a high-precision time synchronization module 5.

[0051] The time synchronization receiving module 1 is used to receive time information from the time synchronization device and generate a synchronization clock signal CLK, a synchronization second pulse signal PPS, and absolute time information TOD based on the time synchronization information.

[0052] In this embodiment, the timing device is configured as a time synchronization module 6. This time synchronization module 6 obtains standard time information from the satellite and distributes timing data packets to the time synchronization receiving module 1 via the network. This allows the time synchronization receiving module 1 to generate a synchronization clock signal CLK, a synchronization second pulse signal PPS, and absolute time information TOD after receiving the timing data packets. The synchronization second pulse signal PPS serves as the original trigger pulse. When the rising edge of PPS arrives, it triggers the FPGA in the signal demodulation device to synchronously generate a modulation pulse signal TRIG. This modulation pulse signal TRIG can control the acousto-optic modulator (which also receives continuous light emitted by the laser) to generate periodic interrogation light pulses required for the operation of the fiber optic hydrophone array system. After the periodic interrogation light pulses are transmitted to the fiber optic hydrophone array via the transmission optical path, they will return as array light pulse signals.

[0053] Among them, the optical path delay measurement module 2 is used to measure the optical path delay, which is the time delay from the time the signal processing system sends out the modulation pulse signal TRIG to the time it receives the corresponding periodic optical pulse train signal.

[0054] In this embodiment, as Figure 4 As shown, the steps for measuring optical path delay by the optical path delay measurement module 2 include:

[0055] S1, When the rising edge of the synchronization second pulse signal PPS arrives, the signal processing system is triggered to generate the modulation pulse signal TRIG. At the same time, the COUNT_PULSE counter in the optical path delay measurement module starts counting synchronously.

[0056] S2, when the periodic optical pulse train signal corresponding to the modulation pulse signal TRIG is detected, the COUNT_PULSE counter stops counting and the count value is N;

[0057] S3, the optical path delay is the product of the clock frequency F of the COUNT_PULSE counter and the count value N;

[0058] The clock frequency F of the COUNT_PULSE counter is obtained by multiplying and / or dividing the synchronous clock signal CLK.

[0059] In this embodiment, in order to facilitate the detection of the corresponding periodic optical pulse train signal, in S1, the time when the rising edge of the synchronization second pulse signal PPS arrives is denoted as time T0, and an enable signal is introduced into the modulation pulse signal TRIG at time T0. The enable signal is used to make the modulation pulse signal TRIG emit.

[0060] Simultaneously in S2, starting from time T0, the power of the periodic optical pulse train signal received by the signal demodulation device is detected sequentially. When the detected power value is lower than the set energy threshold and the duration reaches the period T of the synchronous second pulse signal PPS, the count value M of the COUNT_PULSE counter is recorded. The optical path delay is MF-T.

[0061] In this embodiment, the optical path delay measurement module also includes a threshold counter. The clock frequency of the threshold counter is obtained by multiplying and / or dividing the synchronous clock signal CLK. The threshold tachymeter is used to record the duration for which the power value of the periodic optical pulse train signal is lower than the set energy threshold.

[0062] Among them, the algorithm delay measurement module 3 is used to measure the algorithm delay, which is the time delay from receiving the periodic optical pulse train signal to generating the demodulation result in the signal processing system.

[0063] In this embodiment, the steps of the algorithm delay measurement module 3 in measuring the algorithm delay include:

[0064] S10, Build a simulation test system, such as Figure 5 As shown, the simulation test system includes a fiber optic hydrophone array system and a signal generator. The output of the signal generator is connected to the input of the fiber optic hydrophone array. The input of the signal generator synchronously receives the synchronous second pulse signal PPS and the absolute time information TOD with the signal demodulation device.

[0065] S20, set the signal generator as the external clock source, the synchronous second pulse signal PPS as the external trigger source, select the BURST mode, under the action of the synchronous second pulse signal PPS, the signal generator generates a sine signal with a certain number of cycles and loads it into the fiber optic hydrophone array, and then reads it by the signal demodulation device. The signal demodulation device also receives and demodulates the optical pulse train signal corresponding to the synchronous second pulse signal PPS.

[0066] S30, the time difference between the moment when the signal demodulation device obtains the demodulation result and the moment when the signal demodulation device reads the sine signal is the sum of the algorithm delay and the optical path delay.

[0067] When the synchronous second pulse signal PPS arrives, the counter in the algorithm delay measurement module is activated to record the count value cnt_rslt2 when the signal demodulation device obtains the demodulation result and the count value cnt_rslt1 when the signal demodulation device reads the sinusoidal signal. The sum of the algorithm delay and the optical path delay is the frequency of the counter in the algorithm delay measurement module multiplied by the difference between cnt_rslt2 and cnt_rslt1. Figure 6 As shown, read Figure 6 The COUNT_RESULT values ​​(denoted as cnt_rslt1, cnt_rslt2) corresponding to midpoint 1 (X:5440, Y:1) and point 2 (X:5458, Y:-0.01652) are given by: Time_delay = algorithm delay (Time_demo_delay) + optical path delay (Time_pulse_delay) = 5 (frequency of the counter in the algorithm delay measurement module) × (cnt_rslt2 - cnt_rslt1) (unit: ns). Since the optical path delay measurement module has measured the value of optical path delay (Time_pulse_delay), the algorithm delay (Time_demo_delay) = 5 × (cnt_rslt2 - cnt_rslt1) - optical path delay (Time_pulse_delay). The algorithm delay is a constant value. The simulation system constructed in this embodiment has three measured algorithm delay (Time_demo_delay) values ​​of 1.9179ms, 1.9180ms, and 1.9180ms, respectively, which shows that its error is less than 1μs.

[0068] Among them, the time offset calibration module 4 is used to measure the sum of physical offset and packet delay. The physical offset is the time delay between the synchronous second pulse signal PPS and the absolute time information TOD, and the packet delay is the time delay from the generation of demodulation result to the packaging of absolute time information TOD into the demodulation result by the signal processing system.

[0069] In this embodiment, as Figure 7As shown, the steps of the time offset calibration module 4 in measuring the sum of physical offset and packet assembly delay include:

[0070] 1) When the rising edge of the synchronization second pulse signal PPS arrives (referred to as time T0), the FPGA signal processing system is triggered to generate a periodic modulation pulse signal TRIG;

[0071] 2) At time T0, the COUNT_RESULT counter in the time offset calibration module starts counting from 1. The clock frequency of the counter is 200MHz. Each increment of COUNT_RESULT by 1 indicates that the time has incremented by 5ns. When the rising edge of the next synchronization second pulse signal PPS arrives, the COUNT_RESULT counter starts counting again from 1, and the cycle repeats.

[0072] 3) DEMODULTIONRESULTS is the demodulation result signal output. The demodulation result signal is synchronized with the synchronization second pulse signal PPS. After the demodulation result is generated, TOD data is packaged, such as... Figure 7 As shown, the TOD data is updated with a certain time lag (Time_pps_tod_delay) relative to the rising edge (T0) of the synchronous second pulse signal PPS. At the same time, the demodulated result signal also has a certain time delay relative to the synchronous second pulse signal PPS (Time_assemble_delay). Therefore, when the demodulated result signal is fed into the TOD data, in order to eliminate errors, this invention introduces a COUNT_RESULT counter. The COUNT_RESULT counter starts counting from the rising edge of the synchronous second pulse signal PPS. When the demodulated result is packaged into TOD data, the total time delay relative to the rising edge of the synchronous second pulse signal PPS can be represented by the time represented by the value of the COUNT_RESULT counter at this time. Thus, the actual physical delay (Time_pps_tod_delay) + packet assembly delay (Time_assemble_delay) = 5 × COUNT_RESULT (unit: ns).

[0073] Among them, the high-precision time synchronization module 5 is used to mark the absolute time on the output data of the fiber optic hydrophone array system based on the absolute time information TOD, optical path delay, algorithm delay, physical offset, and packet delay that have been obtained above.

[0074] That is, by adding the absolute time information TOD to the results measured by the optical path delay measurement module 2, the algorithm delay measurement module 3, and the time offset calibration module 4, the output data of the fiber optic hydrophone array system is marked with absolute time. Among them, the time offset calibration module 4 can simultaneously measure the sum of the actual physical delay (Time_pps_tod_delay) and the packet assembly delay (Time_assemble_delay).

[0075] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A high precision time transfer device for fiber optic hydrophone array systems, wherein, The fiber-optic hydrophone array system comprises a signal processing system and a fiber-optic hydrophone array, the signal processing system comprises a signal demodulation device, an acousto-optic modulator and an opto-electric conversion device, the signal demodulation device generates a modulation pulse signal TRIG according to a received synchronization second pulse signal PPS, the acousto-optic modulator generates a periodic inquiry light pulse under the control of the modulation pulse signal TRIG, the fiber-optic hydrophone array returns a periodic light pulse train after receiving the periodic inquiry light pulse, the opto-electric conversion device converts the received periodic light pulse train into a periodic light pulse train signal, the signal demodulation device generates a demodulation result according to the periodic light pulse train signal, and packs absolute time information TOD in the demodulation result to form output data of the fiber-optic hydrophone array, characterized in that the high-precision time service device comprises: a time synchronization receiving module for receiving time service information from a time service device and generating a synchronization clock signal CLK, a synchronization second pulse signal PPS and absolute time information TOD according to the time service information; an optical path delay measuring module for measuring an optical path delay, which is a time delay from the signal processing system sending the modulation pulse signal TRIG to receiving the periodic light pulse train signal; an algorithm delay measuring module for measuring an algorithm delay, which is a time delay from the signal processing system receiving the periodic light pulse train signal to generating the demodulation result; a time offset calibration module for measuring a sum of a physical offset and a packet delay, the physical offset being a time delay between the synchronization second pulse signal PPS and the absolute time information TOD, and the packet delay being a time delay from the signal processing system generating the demodulation result to packing the absolute time information TOD into the demodulation result; and a high-precision time service module for marking absolute time on the output data according to the absolute time information TOD, the optical path delay, the algorithm delay, the physical offset and the packet delay.

2. The high precision time keeping device of claim 1, wherein: The step of measuring the optical path delay by the optical path delay measuring module comprises: S1, when a rising edge of the synchronization second pulse signal PPS arrives, triggering the signal processing system to generate the modulation pulse signal TRIG, and at the same time, a COUNT_PULSE counter in the optical path delay measuring module is synchronously started to count; S2, when detecting that the periodic light pulse train signal corresponding to the modulation pulse signal TRIG arrives, the COUNT_PULSE counter stops counting, and the count value is N; S3, the optical path delay is a product of a clock frequency F at which the COUNT_PULSE counter works and the count value N; wherein the clock frequency F at which the COUNT_PULSE counter works is obtained by frequency multiplication and / or frequency division of the synchronization clock signal CLK.

3. The high precision time keeping device of claim 2, wherein: In S1, the time when the rising edge of the synchronization second pulse signal PPS arrives is denoted as a T0 moment, and an enable signal is introduced into the modulation pulse signal TRIG at the T0 moment; then in S2, the power of the periodic light pulse train signal received by the signal demodulation device is detected in time sequence from the time T0, when the detected power value is lower than the set energy threshold and the duration reaches the period T of the synchronization second pulse signal PPS, the count value M of the COUNT_PULSE counter is recorded, and the count value The optical path delay is MF-T.

4. The high precision time-presentation device according to claim 3, characterized in that: The light path delay measurement module further comprises a threshold counter, a clock frequency of the threshold counter is obtained by frequency multiplication and / or frequency division of the synchronization clock signal CLK, and the threshold counter is used to record a duration that a power value of the periodic optical pulse train signal is lower than a set energy threshold.

5. The high-precision time service apparatus according to claim 2 or 3 or 4, characterized by: The step of measuring the algorithm delay of the algorithm delay measurement module comprises: S10, constructing an analog test system, the analog test system comprising the fiber-optic hydrophone array system and a signal generator, an output end of the signal generator being connected with an input end of the fiber-optic hydrophone array, and an input end of the signal generator receiving the synchronization second pulse signal PPS and the absolute time information TOD synchronously with the signal demodulation device; S20, setting the signal generator as an external clock source, the synchronization second pulse signal PPS as an external trigger source, and selecting a BURST mode, under the action of the synchronization second pulse signal PPS, the signal generator generates a sine signal with a certain number of periods and loads the sine signal into the fiber-optic hydrophone array, and then the signal demodulation device reads the sine signal, and the signal demodulation device also receives and demodulates an optical pulse train signal corresponding to the synchronization second pulse signal PPS; S30, recording a time difference between a time when the signal demodulation device obtains a demodulation result and a time when the signal demodulation device reads the sine signal, the time difference being a sum of the algorithm delay and the light path delay.

6. The high precision time-presentation device according to claim 5, characterized in that: When the synchronization second pulse signal PPS arrives, a counter in the algorithm delay measurement module is started, a count value cnt_rslt2 when the signal demodulation device obtains a demodulation result and a count value cnt_rslt1 when the signal demodulation device reads the sine signal are recorded respectively, and the sum of the algorithm delay and the light path delay is a frequency of the counter in the algorithm delay measurement module multiplied by a difference between the cnt_rslt2 and the cnt_rslt1.

7. The high precision time-presentation device of claim 1, wherein: The time synchronization device is a time synchronization module, the time synchronization module obtains standard time information from a satellite, and distributes a timing data packet to the time synchronization receiving module through a network, so that the time synchronization receiving module generates a synchronization clock signal CLK, a synchronization second pulse signal PPS and absolute time information TOD through an algorithm after receiving the timing data packet.

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