CN109813348B - A distributed optical fiber sensing system and its control method - Google Patents

Abstract

The invention relates to a distributed optical fiber sensing system and its control method. The system includes: a high-speed A/D parallel acquisition unit, a digital down-converter, a parallel accumulative averager unit, and a signal extraction and calculation unit; the high-speed A/D The /D parallel acquisition unit, the digital down-converter, the parallel accumulative averager unit and the signal extraction and calculation unit are sequentially connected. The technical solution provided by the present invention reduces various noise interference introduced by multiple external functional modules in the traditional solution, increases the integration of the system, greatly shortens the time for signal analysis, and thus improves the stability of the distributed optical fiber sensing system sex and reliability.

Description

A distributed optical fiber sensing system and its control method

technical field

The invention relates to the technical field of distributed optical fiber sensing, in particular to a distributed optical fiber sensing system and a control method thereof.

Background technique

Optical fiber can not only be used as the transmission medium of light wave, but also when the light wave propagates in the optical fiber, the characteristic parameters (amplitude, phase, polarization state, wavelength, etc.) The role of the fiber can be changed indirectly or directly, so that the optical fiber can be used as a sensing element to detect various to be measured (physical quantity, chemical quantity and biomass, etc.), which is the basic principle of the fiber optic sensor.

Modern information technology is composed of information collection, transmission and processing technology, so sensor, communication and computer technology have become the three pillars of information technology. In particular, today's society has entered the information age characterized by optical fiber communication technology, and optical fiber sensing technology represents the development trend of a new generation of sensors.

According to different measurement methods, fiber optic sensors are divided into point type and distributed type. Distributed optical fiber sensors have the ability to extract the distribution information of a large-scale measurement field, and can solve many problems in the current measurement field. Among them, the distributed optical fiber temperature sensor can be used for temperature distribution measurement and monitoring of large or long equipment such as large power transformers, high-voltage power grids, and high-rise buildings. With the continuous deepening of research on distributed optical fiber sensing technology based on Brillouin scattering, real-time, stable, reliable and high-precision distributed sensing systems will be further developed.

The current distributed optical fiber sensing technology takes a long time to measure once. If in a multi-channel system, the cycle of scanning all channels will be longer, this will have a greater impact on the real-time performance of the sensing system; in addition, Since the signal processing module is built with discrete components and an additional frequency sweep module is introduced, external noise will be introduced to the entire digital signal processing channel, making the original weak reflection signal more difficult to identify and judge.

Contents of the invention

For the deficiencies in the prior art, the object of the invention is to construct a distributed optical fiber sensing system by utilizing a high-speed A/D parallel acquisition unit, a digital down-converter, a parallel accumulative averager unit, a signal extraction and calculation unit and a control unit, reducing It eliminates various noise interference introduced by multiple external functional modules in the traditional scheme, increases the integration of the system, greatly shortens the time of signal analysis, and thus improves the stability and reliability of the distributed optical fiber sensing system.

The object of the present invention is to adopt following technical scheme to realize:

A distributed optical fiber sensing system, which is improved in that the system includes: a high-speed A/D parallel acquisition unit, a digital down-converter, a parallel accumulative averager unit, and a signal extraction and calculation unit;

The high-speed A/D parallel acquisition unit, digital down-converter, parallel accumulative averager unit and signal extraction and calculation unit are sequentially connected;

The high-speed A/D parallel acquisition unit is used to convert the received analog electrical signal into 4 digital signals of different phases, combine the 4 digital signals of different phases into a serial sampling stream according to phase timing, and outputting the serial sample stream to the digital down converter;

The digital down converter is used to convert the received serial sampling stream into a plurality of parallel baseband digital signals, and output the plurality of parallel baseband digital signals to the parallel accumulative averager unit;

The parallel accumulative averager unit is used to separately obtain the average value of each baseband digital signal in the plurality of parallel baseband digital signals, and average the average value of each baseband digital signal in the plurality of parallel baseband digital signals The value is output to the signal extraction and calculation unit;

The signal extraction and calculation unit is configured to perform fast Fourier transform on the average value of each baseband digital signal in the plurality of parallel baseband digital signals, and obtain each baseband digital signal in the plurality of parallel baseband digital signals The frequency spectrum of the average value of the signal, and the frequency spectrum of the average value of each baseband digital signal in the plurality of parallel baseband digital signals is fitted to a Lorenz curve.

Preferably, the high-speed A/D parallel acquisition unit includes: an amplification circuit, four parallel ADC chips, a digital clock management module and an A/D sampling value buffer;

The amplifying circuit is used to amplify and filter the analog electrical signal provided by the photodetector, and transmit the amplified and filtered analog electrical signal to four parallel ADC chips respectively;

The digital clock management module is used to respectively provide a 0-degree phase clock signal, a 90-degree phase clock signal, a 180-degree phase clock signal and a 270-degree phase clock signal for four parallel ADC chips;

The ADC chip is used to convert the amplified and filtered analog electrical signal with a phase of x degrees into a digital signal if the phase of the received clock signal is x degrees, where x is 0, 90, 180 or 270;

The A/D sampling value buffer is used to combine digital signals with phases of 0 degrees, 90 degrees, 180 degrees and 270 degrees into a serial sampling stream according to phase timing, and output the serial sampling stream to the digital downconverter.

Further, the sampling rate and resolution of the ADC chip are 250MSPS and 16bit respectively;

The model of the ADC chip is AD9467-250 or AD9652;

The digital clock management module is a PLL or DCM unit inside the Xilinx FPGA.

Preferably, the parallel accumulative averager unit is composed of m accumulative averagers connected in parallel.

Further, the digital down converter is used for:

Perform frequency mixing operation, FIR filtering operation and extraction operation on the received serial sampling stream in sequence to obtain m parallel baseband digital signals, and output the m parallel baseband digital signals to the parallel accumulative averager unit respectively Among them, there are m parallel cumulative averagers, where m is a positive integer and m>1.

Specifically, the signal extraction and calculation unit includes: m FFT time-frequency transformation modules and a Lorentz curve fitting and analysis module;

The FFT time-frequency transformation module is used to perform fast Fourier transform on the average value of one baseband digital signal among the m parallel baseband digital signals, and obtain the frequency spectrum of the average value of the baseband digital signal;

The Lorentz curve fitting and analysis module is used to fit the frequency spectrum of the average value of each baseband digital signal in the m parallel baseband digital signals into a Lorentz curve.

Specifically, the FFT time-frequency transformation module is the FFT IP CORE of Xilinx FPGA;

The execution logic of the Lorenz curve fitting and analysis unit is written in VHDL or Verilog language.

Preferably, the system further includes: a control unit;

The control unit is respectively connected with the high-speed A/D parallel acquisition unit, digital down-converter, parallel accumulative averager unit and signal extraction and calculation unit;

The control unit is used to control the execution sequence of the high-speed A/D parallel acquisition unit, the digital down-converter, the parallel cumulative averager unit and the signal extraction and calculation unit.

Further, the control unit is specifically used for:

When the high-speed A/D parallel acquisition unit receives the analog electrical signal, the high-speed A/D parallel acquisition unit is controlled to convert the received analog electrical signal into 4 channels of digital signals with different phases, and the 4 channels of digital signals with different phases are converted into Combining phase timing into a serial sampling stream, and outputting the serial sampling stream to the digital down converter;

When the digital down-converter receives the serial sampling stream, the digital down-converter is controlled to convert the received sampling stream into multiple parallel baseband digital signals, and output the multiple parallel baseband digital signals to the parallel accumulation Averager unit;

When the parallel accumulative averager unit receives a plurality of parallel baseband digital signals, the parallel accumulative averager unit is controlled to obtain the average value of each baseband digital signal in the plurality of parallel baseband digital signals respectively, and the multiple The average value of each baseband digital signal in the parallel baseband digital signals is output to the signal extraction and calculation unit;

When the signal extraction and calculation unit receives the average value of each baseband digital signal in a plurality of parallel baseband digital signals, the control signal extraction and calculation unit controls each baseband digital signal in the plurality of parallel baseband digital signals Fast Fourier transform is performed on the average value of the multiple parallel baseband digital signals, and the frequency spectrum of the average value of each baseband digital signal in the multiple parallel baseband digital signals is obtained, and the average value of each baseband digital signal in the multiple parallel baseband digital signals is The spectrum is fitted to a Lorenz curve.

A control method for a distributed optical fiber sensing system, the improvement is that the method includes:

S1. The number of initialization iterations n=0, n∈[1,N];

S2. The control unit controls the high-speed A/D parallel acquisition unit to convert the received analog electrical signal into 4 digital signals of different phases, and combine the 4 digital signals of different phases into a serial sampling stream according to phase timing, and outputting the serial sample stream to the digital down converter;

S3. The control unit controls the digital down-converter to sequentially perform frequency mixing operation, FIR filtering operation and extraction operation on the received serial digital signal to obtain m parallel baseband digital signals, and separate the m parallel baseband digital signals output to m parallel cumulative averagers in the parallel cumulative averager unit;

Wherein, m is a positive integer and m>1;

S4. The control unit judges whether the number of iterations n is equal to N, if n is equal to N, then execute step S5; if n is not equal to N, then make n=n+1, and execute step S2;

S5. The control unit controls the parallel accumulative averager unit to respectively obtain the average value of each baseband digital signal in the m parallel baseband digital signals, and average the average value of each baseband digital signal in the m parallel baseband digital signals The value is output to the signal extraction and calculation unit;

S6. The control unit controls the signal extraction and calculation unit to perform fast Fourier transform on the average value of each baseband digital signal in the m parallel baseband digital signals, and obtain each baseband digital signal in the m parallel baseband digital signals The frequency spectrum of the average value of the signal, and the frequency spectrum of the average value of each baseband digital signal in the m parallel baseband digital signals is fitted to a Lorenz curve.

Compared with the closest prior art, the present invention has the beneficial effects:

The technical scheme provided by the present invention constructs a distributed optical fiber sensing system through a high-speed A/D parallel acquisition unit, a digital down-converter, a parallel accumulative averager unit, a signal extraction and calculation unit, and a control unit, reducing multiple All kinds of noise interference introduced by external functional modules increase the integration of the system and greatly shorten the time of signal analysis, thus improving the stability and reliability of the distributed optical fiber sensing system;

The technical solution provided by the present invention, by adopting a high-speed A/D parallel acquisition unit and a digital down-converter, the signals of m frequency bands can be processed in parallel after one acquisition, and the original processing time is shortened to 1/m, thereby greatly Reduced signal extraction time.

Description of drawings

Fig. 1 is the structural representation of a kind of distributed optical fiber sensing system in the embodiment of the present invention;

Fig. 2 is a schematic structural view of a high-speed A/D parallel acquisition unit, a parallel accumulative averager unit, and a signal extraction and calculation unit in a distributed optical fiber sensing system in an embodiment of the present invention;

Fig. 3 is the structure schematic diagram of the amplifying circuit in the high-speed A/D parallel acquisition unit of a kind of distributed optical fiber sensing system in the embodiment of the present invention;

Fig. 4 is the working principle diagram of the A/D sampling value buffer in the high-speed A/D parallel acquisition unit of a kind of distributed optical fiber sensing system in the embodiment of the present invention;

5 is a schematic structural diagram of a digital downconverter in a distributed optical fiber sensing system in an embodiment of the present invention;

Fig. 6 is another schematic structural diagram of a distributed optical fiber sensing system in an embodiment of the present invention;

Fig. 7 is a schematic flowchart of a control method of a distributed optical fiber sensing system in an embodiment of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The present invention provides a distributed optical fiber sensing system, as shown in Figure 1, the system includes: a high-speed A/D parallel acquisition unit, a digital down-converter, a parallel accumulative averager unit, and a signal extraction and calculation unit;

The high-speed A/D parallel acquisition unit, digital down-converter, parallel accumulative averager unit and signal extraction and calculation unit are sequentially connected;

The high-speed A/D parallel acquisition unit is used to convert the received analog electrical signal into 4 digital signals of different phases, combine the 4 digital signals of different phases into a serial sampling stream according to phase timing, and outputting the serial sample stream to the digital down converter;

The digital down converter is used to convert the received serial sampling stream into a plurality of parallel baseband digital signals, and output the plurality of parallel baseband digital signals to the parallel accumulative averager unit;

The parallel accumulative averager unit is used to separately obtain the average value of each baseband digital signal in the plurality of parallel baseband digital signals, and average the average value of each baseband digital signal in the plurality of parallel baseband digital signals The value is output to the signal extraction and calculation unit;

The signal extraction and calculation unit is configured to perform fast Fourier transform on the average value of each baseband digital signal in the plurality of parallel baseband digital signals, and obtain each baseband digital signal in the plurality of parallel baseband digital signals The frequency spectrum of the average value of the signal, and the frequency spectrum of the average value of each baseband digital signal in the plurality of parallel baseband digital signals is fitted to a Lorenz curve.

Further, as shown in Figure 2, the high-speed A/D parallel acquisition unit includes: an amplification circuit, four parallel ADC chips, a digital clock management module and an A/D sampling value buffer;

The amplifying circuit is used to amplify and filter the analog electrical signal provided by the photodetector, and transmit the amplified and filtered analog electrical signal to four parallel ADC chips, for example, as shown in Figure 3;

The digital clock management module is used to respectively provide a 0-degree phase clock signal, a 90-degree phase clock signal, a 180-degree phase clock signal and a 270-degree phase clock signal for four parallel ADC chips;

The ADC chip is used to convert the amplified and filtered analog electrical signal with a phase of x degrees into a digital signal if the phase of the received clock signal is x degrees, where x is 0, 90, 180 or 270;

The A/D sampling value buffer is used to combine digital signals with phases of 0 degrees, 90 degrees, 180 degrees and 270 degrees into a serial sampling stream according to phase timing, and output the serial sampling stream to The digital down converter; for example, as shown in FIG. 4 .

Specifically, the sampling rate and resolution of the ADC chip are 250MSPS and 16bit respectively;

The model of the ADC chip is AD9467-250 or AD9652;

The digital clock management module is a PLL or DCM unit inside the Xilinx FPGA.

Further, as shown in FIG. 2 , the parallel accumulative averager unit is composed of m accumulative averagers connected in parallel.

Further, as shown in Figure 5, the digital down converter is used for:

Perform frequency mixing operation, FIR filtering operation and extraction operation on the received serial sampling stream in sequence to obtain m parallel baseband digital signals, and output the m parallel baseband digital signals to the parallel accumulative averager unit respectively Among them, there are m parallel cumulative averagers, where m is a positive integer and m>1.

Further, as shown in FIG. 2, the signal extraction and calculation unit includes: m FFT time-frequency transformation modules and a Lorentz curve fitting and analysis module;

The FFT time-frequency transformation module is used to perform fast Fourier transform on the average value of one baseband digital signal among the m parallel baseband digital signals, and obtain the frequency spectrum of the average value of the baseband digital signal;

The Lorentz curve fitting and analysis module is used to fit the frequency spectrum of the average value of each baseband digital signal in the m parallel baseband digital signals into a Lorentz curve.

Specifically, the FFT time-frequency transformation module is the FFT IP CORE of Xilinx FPGA;

The execution logic of the Lorenz curve fitting and analysis unit is written in VHDL or Verilog language.

Preferably, as shown in FIG. 6, the system further includes: a control unit;

The control unit is respectively connected with the high-speed A/D parallel acquisition unit, digital down-converter, parallel accumulative averager unit and signal extraction and calculation unit;

The control unit is used to control the execution sequence of the high-speed A/D parallel acquisition unit, the digital down-converter, the parallel cumulative averager unit and the signal extraction and calculation unit.

Further, the control unit is specifically used for:

When the high-speed A/D parallel acquisition unit receives the analog electrical signal, the high-speed A/D parallel acquisition unit is controlled to convert the received analog electrical signal into 4 channels of digital signals with different phases, and the 4 channels of digital signals with different phases are converted into Combining phase timing into a serial sampling stream, and outputting the serial sampling stream to the digital down converter;

When the digital down-converter receives the serial sampling stream, the digital down-converter is controlled to convert the received sampling stream into multiple parallel baseband digital signals, and output the multiple parallel baseband digital signals to the parallel accumulation Averager unit;

When the parallel accumulative averager unit receives a plurality of parallel baseband digital signals, the parallel accumulative averager unit is controlled to obtain the average value of each baseband digital signal in the plurality of parallel baseband digital signals respectively, and the multiple The average value of each baseband digital signal in the parallel baseband digital signals is output to the signal extraction and calculation unit;

When the signal extraction and calculation unit receives the average value of each baseband digital signal in a plurality of parallel baseband digital signals, the control signal extraction and calculation unit controls each baseband digital signal in the plurality of parallel baseband digital signals Fast Fourier transform is performed on the average value of the multiple parallel baseband digital signals, and the frequency spectrum of the average value of each baseband digital signal in the multiple parallel baseband digital signals is obtained, and the average value of each baseband digital signal in the multiple parallel baseband digital signals is The spectrum is fitted to a Lorenz curve.

The technical solution provided by this embodiment introduces the key technology in software radio technology - digital down conversion (DDC) technology by improving and optimizing the Brillouin signal detection and processing module in the traditional BOTDR system, replacing the traditional The frequency sweeping module can carry out parallel processing on the signals of m frequency bands once collected, shortening the original processing time to 1/m, thus greatly shortening the signal extraction time;

In addition, by introducing the digital clock management module (DCM) and the DDS frequency synthesis method using all-digital technology in the DDC module, all the processing of the reflected signal is by digital means, and the analog plus digital signal processing method is used in the traditional solution. It has been optimized and has significant advantages such as high frequency resolution, short frequency conversion time and continuous output phase when frequency changes.

The present invention also provides a control method for a distributed optical fiber sensing system, as shown in FIG. 7, the method includes:

101. The number of initialization iterations n=0, n∈[1,N];

102. The control unit controls the high-speed A/D parallel acquisition unit to convert the received analog electrical signal into 4 digital signals of different phases, and combine the 4 digital signals of different phases into a serial sampling stream according to phase timing, and outputting the serial sample stream to the digital down converter;

103. The control unit controls the digital down-converter to sequentially perform frequency mixing operation, FIR filtering operation and extraction operation on the received serial digital signal to obtain m parallel baseband digital signals, and separate the m parallel baseband digital signals output to m parallel cumulative averagers in the parallel cumulative averager unit;

Wherein, m is a positive integer and m>1;

104. The control unit judges whether the number of iterations n is equal to N, if n is equal to N, then execute step 105; if n is not equal to N, then make n=n+1, and execute step 102;

105. The control unit controls the parallel accumulative averager unit to respectively obtain the average value of each baseband digital signal in the m parallel baseband digital signals, and average the average value of each baseband digital signal in the m parallel baseband digital signals The value is output to the signal extraction and calculation unit;

106. The control unit controls the signal extraction and calculation unit to perform fast Fourier transform on the average value of each baseband digital signal in the m parallel baseband digital signals, and obtain each baseband digital signal in the m parallel baseband digital signals The frequency spectrum of the average value of the signal, and the frequency spectrum of the average value of each baseband digital signal in the m parallel baseband digital signals is fitted to a Lorenz curve.

Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowcharts and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the claims of the present invention.

Claims (2)

1. A distributed fiber optic sensing system, comprising: the device comprises a high-speed A/D parallel acquisition unit, a digital down converter, a parallel accumulation averager unit and a signal extraction and calculation unit;

the high-speed A/D parallel acquisition unit, the digital down converter, the parallel accumulation averager unit and the signal extraction and calculation unit are sequentially connected;

the high-speed A/D parallel acquisition unit is used for converting received analog electric signals into 4 paths of digital signals with different phases, combining the 4 paths of digital signals with different phases into a serial sampling stream according to a phase time sequence, and outputting the serial sampling stream to the digital down converter;

the digital down converter is used for converting a received serial sampling stream into a plurality of parallel baseband digital signals and outputting the plurality of parallel baseband digital signals to the parallel accumulation averager unit;

the parallel accumulation averager unit is used for respectively acquiring the average value of each baseband digital signal in the plurality of parallel baseband digital signals and outputting the average value of each baseband digital signal in the plurality of parallel baseband digital signals to the signal extraction and calculation unit;

the signal extracting and calculating unit is configured to perform fast fourier transform on an average value of each baseband digital signal in the plurality of parallel baseband digital signals, obtain a spectrum of the average value of each baseband digital signal in the plurality of parallel baseband digital signals, and fit the spectrum of the average value of each baseband digital signal in the plurality of parallel baseband digital signals into a lorentzian curve;

the high-speed A/D parallel acquisition unit comprises: the device comprises an amplifying circuit, four ADC chips connected in parallel, a digital clock management module and an A/D sampling value buffer area;

the amplifying circuit is used for amplifying and filtering the analog electric signals provided by the photoelectric detector and respectively transmitting the amplified and filtered analog electric signals to four parallel ADC chips;

the digital clock management module is used for respectively providing a 0-degree phase clock signal, a 90-degree phase clock signal, a 180-degree phase clock signal and a 270-degree phase clock signal for the four ADC chips which are connected in parallel;

the ADC chip is used for converting the amplified and filtered analog electric signal with the phase of x degrees into a digital signal if the phase of the received clock signal is x degrees, wherein x is 0, 90, 180 or 270;

the A/D sampling value buffer area is used for combining digital signals with phases of 0 degree, 90 degrees, 180 degrees and 270 degrees into a serial sampling stream according to a phase sequence and outputting the serial sampling stream to the digital down converter;

the sampling rate and the resolution of the ADC chip are respectively 250MSPS and 16bit;

the model of the ADC chip is AD9467-250 or AD9652;

the digital clock management module is a PLL or DCM unit in the XilinxFPGA;

the parallel accumulation averager unit is formed by connecting m accumulation averagers in parallel;

the digital down converter is configured to:

sequentially performing frequency mixing operation, FIR filtering operation and extraction operation on a received serial sampling stream to obtain m parallel baseband digital signals, and respectively outputting the m parallel baseband digital signals to m parallel accumulation averagers in the parallel accumulation averager unit, wherein m is a positive integer and m is greater than 1;

the signal extraction and calculation unit comprises: m FFT time-frequency transformation modules and Lorentz curve fitting and analyzing modules;

the FFT time-frequency transformation module is used for carrying out fast Fourier transformation on the average value of 1 baseband digital signal in the m parallel baseband digital signals to obtain the frequency spectrum of the average value of the baseband digital signals;

the Lorentz curve fitting and analyzing module is used for fitting the frequency spectrum of the average value of each baseband digital signal in the m parallel baseband digital signals into a Lorentz curve;

the FFT time-frequency transformation module is FFTIPCORE of the XilinxFPGA;

the execution logic of the Lorentz curve fitting and analyzing unit is written by adopting VHDL or Verilog language;

the system, still include: a control unit;

the control unit is respectively connected with the high-speed A/D parallel acquisition unit, the digital down converter, the parallel accumulation averager unit and the signal extraction and calculation unit;

the control unit is used for controlling the execution sequence of the high-speed A/D parallel acquisition unit, the digital down converter, the parallel accumulation averager unit and the signal extraction and calculation unit;

the control unit is specifically configured to:

when the high-speed A/D parallel acquisition unit receives an analog electric signal, the high-speed A/D parallel acquisition unit is controlled to convert the received analog electric signal into 4 paths of digital signals with different phases, the 4 paths of digital signals with different phases are combined into a serial sampling stream according to a phase sequence, and the serial sampling stream is output to the digital down converter;

when the digital down converter receives the serial sampling stream, the digital down converter is controlled to convert the received sampling stream into a plurality of parallel baseband digital signals and output the plurality of parallel baseband digital signals to the parallel accumulation averager unit;

when the parallel accumulation averager unit receives a plurality of parallel baseband digital signals, the parallel accumulation averager unit is controlled to respectively obtain the average value of each baseband digital signal in the plurality of parallel baseband digital signals, and the average value of each baseband digital signal in the plurality of parallel baseband digital signals is output to the signal extraction and calculation unit;

when the signal extracting and calculating unit receives the average value of each baseband digital signal in the plurality of parallel baseband digital signals, the signal extracting and calculating unit is controlled to perform fast Fourier transform on the average value of each baseband digital signal in the plurality of parallel baseband digital signals, obtain the frequency spectrum of the average value of each baseband digital signal in the plurality of parallel baseband digital signals, and simulate the frequency spectrum of the average value of each baseband digital signal in the plurality of parallel baseband digital signals into a Lorentz curve.

2. A method of controlling a distributed fibre optic sensing system according to claim 1, the method comprising:

s1, initializing iteration times n =0, n belongs to [1, N ];

s2, the control unit controls the high-speed A/D parallel acquisition unit to convert the received analog electric signals into 4 paths of digital signals with different phases, the 4 paths of digital signals with different phases are combined into a serial sampling stream according to a phase sequence, and the serial sampling stream is output to the digital down converter;

s3, the control unit controls the digital down converter to sequentially perform frequency mixing operation, FIR filtering operation and extraction operation on the received serial digital signals to obtain m parallel baseband digital signals, and the m parallel baseband digital signals are respectively output to m parallel accumulation averagers in the parallel accumulation averager unit;

wherein m is a positive integer and m > 1;

s4, the control unit judges whether the iteration number N is equal to N, and if the iteration number N is equal to N, the step S5 is executed; if N is not equal to N, let N = N +1, and execute step S2;

s5, the control unit controls the parallel accumulation averager unit to respectively obtain the average value of each baseband digital signal in the m parallel baseband digital signals, and outputs the average value of each baseband digital signal in the m parallel baseband digital signals to the signal extraction and calculation unit;

and S6, the control unit controls the signal extraction and calculation unit to perform fast Fourier transform on the average value of each baseband digital signal in the m parallel baseband digital signals, so that the frequency spectrum of the average value of each baseband digital signal in the m parallel baseband digital signals is obtained, and the frequency spectrum of the average value of each baseband digital signal in the m parallel baseband digital signals is simulated into a Lorentz curve.

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