CN115855129A - Brillouin distributed sensing method and equipment based on high-spectrum-efficiency frequency division multiplexing - Google Patents

Abstract

The invention provides a Brillouin distributed sensing method and equipment based on high-spectrum-efficiency frequency division multiplexing, which comprises the following steps of: the signal generator generates a pseudo-random signal and modulates the pseudo-random signal to obtain a modulation signal; arranging the modulation signals in a matrix form, and taking any two rows L1 and L2; constructing a non-orthogonal transformation matrix A; taking the first N rows and N columns of the non-orthogonal transformation matrix A to obtain a matrix A1; taking N rows and N columns to obtain a matrix A2; obtaining time domain sampling signals S1 and S2 according to the matrixes A1 and A2 and the matrixes L1 and L2; generating a complete time domain sampling signal according to the S1 and the S2; presetting a bandwidth B of an orthogonal frequency division multiplexing technology, and obtaining a digital signal by passing a complete time domain sampling signal through a digital-to-analog converter; the apparatus is configured to implement the method. The invention has the beneficial effects that: under the condition of ensuring the spatial resolution, the frequency detection precision can be improved, and the simplicity and the accuracy of the system are improved.

Description

Brillouin distributed sensing method and equipment based on high-spectrum-efficiency frequency division multiplexing

Technical Field

The invention relates to the field of optical pulse coding, in particular to a Brillouin distributed sensing method based on high-spectral-efficiency frequency division multiplexing.

Background

With the rapid development of the technology, the optical fiber sensing technology is mature day by day, and the development is great in the aspects of sensing distance, measurement accuracy and the like. However, with the layout of optical fiber sensing in high-precision dynamic measurement scenes such as civil engineering, bridges and spacecrafts, new requirements are put forward on the optical fiber sensing Brillouin optical time domain analysis technology. In recent years, researchers have proposed frequency comb, fast scan and other schemes, but these schemes are all frequency detection technologies based on traditional frequency sweep technology in nature, require additional equipment to be added, and have respective limitations. Further, there is a frequency detection technique using multiple carriers, such as an orthogonal frequency division multiplexing technique, which can achieve detection of a subcarrier frequency, but its pulse width and frequency detection accuracy are contradictory and cannot be adjusted due to the orthogonal characteristic.

Disclosure of Invention

In order to solve the problems, the invention adopts a scheme of non-orthogonal optical pulse coding, abandons the original simple optical amplitude pulse signal modulation or orthogonal frequency division multiplexing technology, designs a newly-developed non-orthogonal matrix, constructs a non-orthogonal multi-carrier pulse signal, can determine Brillouin frequency shift through the Brillouin effect of a subcarrier of the signal, and further determines the performance of a monitoring component according to the frequency shift.

The invention provides a Brillouin distributed sensing method based on high-spectrum-efficiency frequency division multiplexing, which specifically comprises the following steps of:

s1: the signal generator generates a pseudo-random signal and modulates the pseudo-random signal to obtain a modulation signal D; arranging the modulation signals D in a matrix form, and taking any two lines L1 and L2;

s2: constructing a non-orthogonal transformation matrix A; a is N/a row and N/a column; wherein a is a preset compression factor; n is a preset value;

s3: taking the first N rows and N columns of the non-orthogonal transformation matrix A to obtain a matrix A1; taking N rows and N columns behind the non-orthogonal transformation matrix A to obtain a matrix A2;

s4: obtaining a time domain sampling signal S1 according to the matrixes A1 and L1; obtaining a time domain sampling signal S2 according to the matrixes A2 and L2;

s5: generating a complete time domain sampling signal according to the time domain sampling signals S1 and S2;

s6: presetting a bandwidth B of an orthogonal frequency division multiplexing technology, and obtaining a digital signal by passing a complete time domain sampling signal through a digital-to-analog converter;

and S7, modulating the digital signal to an optical carrier by using the driving electro-optical modulator to finally obtain an optical fiber signal.

Brillouin distributed sensing equipment based on high-spectrum-efficiency frequency division multiplexing comprises:

a signal generator for generating a pseudo-random signal;

the signal modulator is used for modulating the pseudo-random signal to obtain a modulated signal D;

the signal processor is used for constructing a non-orthogonal transformation matrix A; a is N/a row and N/a column; wherein a is a preset compression factor; n is a preset value; taking the first N rows and N columns of the non-orthogonal transformation matrix A to obtain a matrix A1; taking N rows and N columns behind the non-orthogonal transformation matrix A to obtain a matrix A2; obtaining a time domain sampling signal S1 according to the matrixes A1 and L1; obtaining a time domain sampling signal S2 according to the matrixes A2 and L2; generating a complete time domain sampling signal according to the time domain sampling signals S1 and S2;

the digital-to-analog converter is used for converting the complete time domain sampling signal into a digital signal;

and driving an electro-optical modulator to modulate the digital signal onto an optical carrier to finally obtain an optical fiber signal.

Compared with the prior art, the invention has the beneficial effects that: the method can only process the modulation signal under the condition of not changing the system structure, can improve the detection precision of the frequency (the carrier wave interval is small) under the condition of ensuring the spatial resolution (the pulse width), and improves the simplicity and the accuracy of the system.

Drawings

FIG. 1 is a schematic of the process of the present invention;

fig. 2 is a schematic diagram of the working principle of the device of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

Referring to FIG. 1, FIG. 1 is a schematic flow chart of a method according to the present invention;

the invention provides a Brillouin distributed sensing method based on high-spectrum-efficiency frequency division multiplexing, which specifically comprises the following steps of:

s1: the signal generator generates a pseudo-random signal and modulates the pseudo-random signal to obtain a modulated signal D; arranging the modulation signals D in a matrix form, and taking any two lines L1 and L2;

for example, the pseudo-random signal data generated in the present invention is (0, 1,0, 1.);

it should be noted that, in step S1, the modulation signal D is one of a return-to-zero code, a non-return-to-zero code, or a gray code pattern. Of course, the modulated signal may also be other relevant code patterns, which are illustrated schematically here.

As an embodiment, the pseudo-random signal is modulated into a non-return-to-zero code, the modulation signal is D, and if K x N data exist in D, the D is subjected to serial-parallel conversion to form a matrix with K rows and N columns; n is a predetermined value, such as 128;

the present invention takes any two rows L1 and L2, such as L1= [1,0,1 ].] ^T And L2= [1,0,1 ].] ^T ；

S2: constructing a non-orthogonal transformation matrix A; a is N/a row and N/a column; wherein a is a preset compression factor; n is a preset value;

it should be noted that, by using the compression factor a of the non-orthogonal multi-carrier technique, the non-orthogonal transformation matrix a is constructed as follows:

generally speaking, the smaller a is, the higher the spectral resolution is, but the more complicated the information processing is, generally speaking, a takes the range of 0.7-0.9, and assuming that a =0.8, a non-orthogonal transformation matrix a is constructed based on the above parameters, which is a 160 × 160 matrix.

S3: taking the first N rows and N columns of the non-orthogonal transformation matrix A to obtain a matrix A1; taking N rows and N columns behind the non-orthogonal transformation matrix A to obtain a matrix A2;

s4: obtaining a time domain sampling signal S1 according to the matrixes A1 and L1; obtaining a time domain sampling signal S2 according to the matrixes A2 and L2;

the first N =128 (1-128) rows and N =128 (1-128) columns of the non-orthogonal transformation matrix a are taken to form a matrix A1, and the first N =128 (1-128) rows and the second N =128 (33-160) columns are taken to form A2. Based on the matrices A1 and L1, a non-orthogonal multi-carrier signal generation may be performed to form a time-domain sampled signal S, comprising 2 symbols S1 and S2, as follows, equations S1= A1 × L1 and S2= A2 × L2. S1 and S2 are formed as vector signals of 128 elements.

S5: generating a complete time domain sampling signal according to the time domain sampling signals S1 and S2;

in step S5, the time domain sampling signals S1 and S2 are converted in series-parallel and transmitted alternately, and finally a complete time domain sampling signal is obtained.

Specifically, in the application, the two signals are subjected to serial-parallel conversion and are alternately transmitted, i.e., the signal is transmitted in the s1s2s1s2.

S6: presetting a bandwidth B of an orthogonal frequency division multiplexing technology, and obtaining a digital signal by passing a complete time domain sampling signal through a digital-to-analog converter;

in step S6, the bandwidth B is greater than the bandwidth of the brillouin frequency domain analysis, and the sampling rate of the digital-to-analog converter is greater than B.

The bandwidth B is typically larger than the frequency sweep range of the brillouin signal and should typically be 200MHz.

And S7, modulating the digital signal to an optical carrier by using the driving electro-optical modulator to finally obtain an optical fiber signal.

And forming an optical pulse code signal through the steps, and replacing the original optical pulse signal with the signal to obtain a time domain signal of the Brillouin optical time domain analysis optical sensing technology.

From the above results, it can be seen that 128 subcarriers are included in each bandwidth aB, and the brillouin carrier frequency position can be obtained by detecting the conversion of the subcarriers, without additional devices. Meanwhile, for the orthogonal signal bandwidth B, the bandwidth of the non-orthogonal multi-carrier generation scheme adopted here is compressed, and the sub-carrier interval is changed into aB/N, so that the spectrum detection precision is improved.

In addition, because the signal sampling is 128 points of one symbol, and the sampling rate is consistent, as long as the known pulse width is the same, the spatial resolution of the Brillouin optical time domain analysis technology is not changed, and the frequency resolution of the system can be improved without influencing the spatial resolution based on the system.

Referring to fig. 2, fig. 2 is a schematic diagram illustrating the operation principle of the apparatus of the present invention; brillouin distributed sensing equipment based on high-spectrum-efficiency frequency division multiplexing comprises:

a signal generator for generating a pseudo-random signal;

the signal modulator is used for modulating the pseudo-random signal to obtain a modulated signal D;

the signal processor is used for constructing a non-orthogonal transformation matrix A; a is N/a row and N/a column; wherein a is a preset compression factor; n is a preset value; taking the first N rows and N columns of the non-orthogonal transformation matrix A to obtain a matrix A1; taking N rows and N columns behind the non-orthogonal transformation matrix A to obtain a matrix A2; obtaining a time domain sampling signal S1 according to the matrixes A1 and L1; obtaining a time domain sampling signal S2 according to the matrixes A2 and L2; generating a complete time domain sampling signal according to the time domain sampling signals S1 and S2; it should be noted that the signal processor is implemented by processing with a computer or a corresponding control chip.

The digital-to-analog converter is used for converting the complete time domain sampling signal into a digital signal;

and driving an electro-optical modulator to modulate the digital signal onto an optical carrier to finally obtain an optical fiber signal.

The invention has the beneficial effects that: extra equipment is not needed to be added, only the modulation signal is processed, and only the position of the subcarrier affected by the optical fiber sensing is searched, so that the Brillouin frequency shift can be determined, and the external information sensing is obtained; and the detection precision of the frequency (the carrier wave interval is small) can be improved under the condition of ensuring the spatial resolution (the pulse width), and the simplicity and the accuracy of the system are improved.

It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.

Claims (7)

1. The Brillouin distributed sensing method based on the high-spectrum-efficiency frequency division multiplexing is characterized by comprising the following steps of: the method comprises the following steps:

s1: the signal generator generates a pseudo-random signal and modulates the pseudo-random signal to obtain a modulated signal D; arranging the modulation signals D in a matrix form, and taking any two lines L1 and L2;

s2: constructing a non-orthogonal transformation matrix A; a is N/a row and N/a column; wherein a is a preset compression factor; n is a preset value;

s3: taking the first N rows and N columns of the non-orthogonal transformation matrix A to obtain a matrix A1; taking N rows and N columns behind the non-orthogonal transformation matrix A to obtain a matrix A2;

s4: obtaining a time domain sampling signal S1 according to the matrixes A1 and L1; obtaining a time domain sampling signal S2 according to the matrixes A2 and L2;

s5: generating a complete time domain sampling signal according to the time domain sampling signals S1 and S2;

s6: presetting a bandwidth B of an orthogonal frequency division multiplexing technology, and obtaining a digital signal by passing a complete time domain sampling signal through a digital-to-analog converter;

and S7, modulating the digital signal to an optical carrier by using the driving electro-optical modulator to finally obtain an optical fiber signal.

2. The brillouin distributed sensing method based on high spectral efficiency frequency division multiplexing according to claim 1, wherein: in step S1, the modulation signal D is one of a return-to-zero code, a non-return-to-zero code, or a gray code pattern.

3. The Brillouin distributed sensing method based on high-spectrum-efficiency frequency division multiplexing is characterized by comprising the following steps of: the formula of the non-orthogonal transformation matrix a in step S2 is as follows:

4. the brillouin distributed sensing method based on high spectral efficiency frequency division multiplexing according to claim 1, wherein: in step S4, the time domain sampling signals S1 and S2 are processed by using a non-orthogonal multi-carrier signal generation method.

5. The brillouin distributed sensing method based on high spectral efficiency frequency division multiplexing according to claim 1, wherein: in step S5, the time domain sampling signals S1 and S2 are converted in series-parallel and transmitted alternately, and finally a complete time domain sampling signal is obtained.

6. The brillouin distributed sensing method based on high spectral efficiency frequency division multiplexing according to claim 1, wherein: in step S6, the bandwidth B is greater than the bandwidth of the brillouin frequency domain analysis, and the sampling rate of the digital-to-analog converter is greater than B.

7. Brillouin distributed sensing equipment based on high-spectrum-efficiency frequency division multiplexing is characterized in that: the method comprises the following steps:

a signal generator for generating a pseudo-random signal;

the signal modulator is used for modulating the pseudo-random signal to obtain a modulated signal D;

the signal processor is used for constructing a non-orthogonal transformation matrix A; a is N/a row and N/a column; wherein a is a preset compression factor; n is a preset value; taking the first N rows and N columns of the non-orthogonal transformation matrix A to obtain a matrix A1; taking N rows and N columns behind the non-orthogonal transformation matrix A to obtain a matrix A2; obtaining a time domain sampling signal S1 according to the matrixes A1 and L1; obtaining a time domain sampling signal S2 according to the matrixes A2 and L2; generating a complete time domain sampling signal according to the time domain sampling signals S1 and S2;

the digital-to-analog converter is used for converting the complete time domain sampling signal into a digital signal;

and driving an electro-optical modulator to modulate the digital signal onto an optical carrier to finally obtain an optical fiber signal.

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