CN103791935A - Processing method of pulse subdivision superposed signals - Google Patents
Processing method of pulse subdivision superposed signals Download PDFInfo
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- CN103791935A CN103791935A CN201410015444.2A CN201410015444A CN103791935A CN 103791935 A CN103791935 A CN 103791935A CN 201410015444 A CN201410015444 A CN 201410015444A CN 103791935 A CN103791935 A CN 103791935A
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Abstract
The invention discloses a processing method of pulse subdivision superposed signals, and provides the signal processing method capable of simultaneously improving spatial resolution and sensing distance of a BOTDR system. According to the technical scheme, the processing method of the pulse subdivision superposed signals comprises the steps that (1) obtained scattering spectra are respectively subtracted from a standard scattering spectrum to obtain a superposed information spectrum; (2) substraction is carried out on the (n+1)th spectral line and the nth spectral line in the obtained superposed information spectrum, n is a natural number equal to or more than two, and in this way, information spectral lines of the whole optical fiber are obtained in sequence; (3) finally, the frequency corresponding to the null point of each information spectral line is worked out, and temperature distribution of the whole optical fiber in each D/n optical fiber length can be obtained. The processing method of the pulse subdivision superposed signals solves the problem that the spatial resolution and the pulse width in a traditional BOTDR system are mutually restricted, is simple to operate, solves the problem that the spatial resolution and the sensing distance are contradictory, largely improves system performance, and is an ideal signal processing method.
Description
Technical field
The present invention relates to the signal processing method in optical technical field, particularly a kind of pulse segmentation superposed signal disposal route, the method is for the signal processing of distributed optical fiber sensing system.
Background technology
Distributing optical fiber sensing has anti-electromagnetic interference (EMI), the advantage such as highly sensitive, high pressure resistant, corrosion-resistant, has received in recent years more and more scholars' concern, has huge development prospect.The spatial resolution of distributing optical fiber sensing reduces along with the increase of direct impulse width, so conventionally adopt the way that reduces direct impulse width to improve spatial resolution, but be subject to the restriction of phonon lifetime, in the time that pulse width is less than phonon Henan and speeds the time, to cause phonon excitation insufficient, make brillouin gain reduce and Brillouin scattering spectrum widening and deteriorated, finally cause distributed fiberoptic sensor in theory limit space resolution can only reach 1m.But need centimetre-sized spatial resolution in fields such as the Gernral Check-up of aircraft hull and building structure health monitorings, therefore improve the method for spatial resolution in these field active demands.
Research is found, when in spatial resolution, length of fibre information measured changes, can there is micro-deformation in the backward Brillouin scattering spectra collecting, in this deformation, implying the information measured variation that conventional art cannot obtain, based on this, we propose a kind of pulse segmentation superposed signal disposal route, by direct impulse segmentation is obtained to implicit quantity of information in Brillouin scattering spectra, to obtain centimetre-sized spatial resolution, theoretical analysis proves its feasibility, and correctness and the validity of the method has also been verified in data analysis.
Summary of the invention
The object of this invention is to provide a kind of spatial resolution of BOTDR system and signal processing method of distance sensing of simultaneously improving.
The present invention carries out equivalence segmentation to direct impulse light, and the back scattering spectrum obtaining is processed according to the operation rule of the method regulation, improves spatial resolution with this.
For the technical matters that solves above-mentioned existence realizes goal of the invention, the inventive method is achieved through the following technical solutions:
A kind of pulse segmentation superposed signal disposal route, its content comprises the steps:
(1) the backward Brillouin's spectrum subtraction of standard obtaining at the real-time backward Brillouin scattering spectrum collecting and demarcation temperature is obtained to preliminary scattering spectral difference spectrum---overlapped information spectrum, n+1 article of spectral line and n article of spectral line in the scattering spectral difference spectrum of acquisition are done to poor (n=2,3,), so obtain successively the information spectral line of whole optical fiber, obtain every information spectral line frequency corresponding to zero point, finally utilize v
bT=2v-v
b, derive and calculate the Temperature Distribution that can obtain in the every D/n fiber lengths of whole optical fiber through theory; v
bTfor frequency displacement corresponding after temperature variation in spatial resolution, v
bfor the Brillouin shift under room temperature, v is frequency displacement corresponding to the zero point of each spectral line in Information Spectrum; D is spatial resolution, and n is the sampling number in each spatial resolution, depends on sampling rate;
(2) real-time back scattering spectral line is done poorly with demarcating the standard back scattering spectral line obtaining at temperature, obtain overlapped information spectrum;
(3) be one group of spectral line by the overlay information spectrum of acquisition, n+1 article of spectral line and n article of spectral line in this group spectral line are done to poor (n=2,3,) acquired information spectrum, deduct the n article of spectral line all spectral lines before in Information Spectrum with n article of scattering spectral line afterwards, so obtain successively the information spectral line of whole optical fiber;
(4) the frequency displacement v corresponding to zero point of each spectral line in acquired information spectrum, according to formula v
bT=2v-v
b, finally obtaining the Temperature Distribution in the every D/n fiber lengths of whole optical fiber, D is spatial resolution, n is the sampling number in each spatial resolution, depends on sampling rate, v
bTfor frequency displacement corresponding after temperature variation in spatial resolution, v
bfor the Brillouin shift under room temperature, v is frequency displacement corresponding to the zero point of each spectral line in Information Spectrum;
(5) so far obtain System spatial resolution D/n, this spatial resolution depends on the sample rate of data completely.
Owing to adopting technique scheme, a kind of pulse segmentation superposed signal disposal route provided by the invention, the beneficial effect compared with prior art having is:
The pulse that first the present invention is 1m by a spatial resolution is divided into some unit, when the light of each unit is propagated in optical fiber, can produce respectively back scattering, and the real-time back scattering spectrum of acquisition is the stack of all unit scattering spectra in a spatial resolution.Backward Brillouin scattering spectrum generation deformation in the fiber segment of temperature variation, has implied temperature information in deformation.Secondly back scattering spectrum now and the standard back scattering of corresponding position around of whole sensor fibre are composed and made the poor overlapped information spectrum spectral line that obtains.This spectral line is spatially deducted successively to the variable quantity of all spectral lines in front, remove the impact of temperature information implicit in spectrum above on temperature information implicit in the corresponding spectrum of this optical fiber, and then obtain the scattering spectra variable quantity information in the length of each sub-divided pulse unitary space.Finally, according to the linear relationship of frequency displacement and temperature variation existence, can obtain the now Temperature Distribution situation of whole section of optical fiber, what this Temperature Distribution situation embodied is the information in centimetre magnitude spatial resolution.Employing the inventive method spatial resolution only depends on sample rate, has solved the problem that traditional B OTDR System spatial resolution and pulse width restrict mutually.
The inventive method is simple to operate, has solved the problem that spatial resolution and distance sensing are conflicts, has greatly improved system performance, is a kind of desirable signal processing method.
Accompanying drawing explanation
Fig. 1 is the principle that Brillouin spectrum produces;
Fig. 2 is optical fiber when around occurrence temperature changes, once samples the 10m that obtains to the Brillouin's back scattering spectrum distribution situation in 11m every 0.1m, is standard spectral line;
Fig. 3 is after optical fiber environment temperature changes, and once samples the 10m that obtains to the Brillouin's back scattering spectrum distribution situation in 11m every 0.1m, is real-time spectral line;
Fig. 4 is the poor of standard spectral line and real-time spectral line, is overlapped information spectrum;
Fig. 5 is through overlapped information spectrum being processed to the spectral line obtaining, being Information Spectrum;
Fig. 6 be into the concrete frequency shift value that obtains of Information Spectrum;
Fig. 7 is the Temperature Distribution situation in every 0.1m.
Embodiment
Below in conjunction with accompanying drawing and instantiation, the present invention is further illustrated:
A kind of pulse segmentation superposed signal disposal route, its content comprises the steps:
(1) the backward Brillouin's spectrum subtraction of standard obtaining at the real-time backward Brillouin scattering spectrum collecting and demarcation temperature is obtained to preliminary scattering spectral difference spectrum---overlapped information spectrum, n+1 article of spectral line and n article of spectral line in the scattering spectral difference spectrum of acquisition are done to poor (n=2,3,), so obtain successively the information spectral line of whole optical fiber, obtain every information spectral line frequency corresponding to zero point, finally utilize v
bT=2v-v
b, derive and calculate the Temperature Distribution that can obtain in the every D/n fiber lengths of whole optical fiber through theory; v
bTfor frequency displacement corresponding after temperature variation in spatial resolution, v
bfor the Brillouin shift under room temperature, v is frequency displacement corresponding to the zero point of each spectral line in Information Spectrum; D is spatial resolution, and n is the sampling number in each spatial resolution, depends on sampling rate;
As shown in Figure 1, c is the light velocity in vacuum, and τ is direct impulse width, and n is optical fibre refractivity.Dash area length c τ/n is direct impulse length, while supposing that pulsed light forward terminal is transmitted to optical fiber P1 place, produces scattering unit S1, and now pulsed light continues to propagate, and scattering unit S1 starts to propagate in opposite direction.In the time that pulsed light forward terminal is transmitted to P2 place, produce scattering unit S2, and now scattering unit S1 is transmitted to optical fiber P1 place just, the scattering unit producing at P1 place with pulsed light aft terminal overlaps.Be transmitted to from P1 at direct impulse light in the process at P4 place, except forward terminal, all the other each positions can produce scattering unit.So, when now the scattering unit at P5 place is direct impulse light forward terminal through whole P1 to optical fiber between P4, the stack of the sub-scattering spectrum producing in all positions, and P1 is the half of direct impulse space length to the distance of P5, so the spatial resolution of distributing optical fiber sensing is D=c τ/2n, i.e. the half of direct impulse space length.
Based on above scattering mechanism, when assumed temperature is 20 ℃, the Brillouin frequency displacement that general single mode fiber is corresponding is 11.2GHz.In any direct impulse width situation, suppose that whole sensor fibre front end 10m is placed under 20 ℃ of normal temperature, and by 10.1m to 10.2m, 10.5m to 10.6m and 10.7m be warming up to respectively 50 ℃, 70 ℃ and 60 ℃ to the optical fiber in 10.8m.
Now the direct impulse light of any width is injected to the sensor fibre that occurrence temperature changes, to the backward Brillouin scattering light obtaining, adopt 2GHz sampling rate to sample to back scattering spectrum, the 10m of acquisition composes as shown in Figure 2 to the interior backward Brillouin scattering of 11m optical fiber.Knownly compose as shown in Figure 3 with the standard backward Brillouin scattering obtaining in optical fiber and standard temperature when whole.
(2) real-time back scattering spectral line is done poorly with demarcating the standard back scattering spectral line obtaining at temperature, obtain overlapped information spectrum; First, the real-time back scattering spectrum standard spectrum corresponding with Fig. 3 corresponding Fig. 2 subtracted each other and obtain preliminary scattering spectral difference, be overlapped information spectrum, as shown in Figure 4.
(3) be one group of spectral line by the overlay information spectrum of acquisition, n+1 article of spectral line and n article of spectral line in this group spectral line are done to poor (n=2,3,) acquired information spectrum, deduct the n article of spectral line all spectral lines before in Information Spectrum with n article of scattering spectral line afterwards, so obtain successively the information spectral line of whole optical fiber;
Again, Article 2 spectral line on the space in Fig. 4 is deducted to Article 1 spectral line, then Article 3 spectral line is deducted to the poor of Article 1 and Article 2 spectral line, the like can obtain the positive section of information spectral line on optical fiber, as shown in Figure 5.
(4) the frequency displacement v corresponding to zero point of each spectral line in acquired information spectrum, according to formula v
bT=2v-v
b, finally obtain the Temperature Distribution in the every D/n fiber lengths of whole optical fiber;
(5) so far obtain System spatial resolution, this spatial resolution depends on the sample rate D/n of data completely.
Finally can obtain the frequency displacement at zero point of corresponding spectral line by Fig. 5 and Fig. 6, v proportion by subtraction is 11.228GHz, 11.223GHz and 11.217GHz, now passes through v
biT1=2v-v
bcan obtain the Brillouin shift information of 10m to the interior every 10cm of 11m fiber segment, i.e. v
bTbe respectively 11.234GHz, 11.256GHz and 11.245GHz, and then obtain temperature information, as shown in Figure 7.
Concrete data are as shown in table 1.
The concrete data of table 1 Temperature Distribution
Table 1 has shown the concrete data of 10m to the interior concrete Brillouin frequency displacement of 11m optical fiber and Temperature Distribution, as can be seen from the table, pulse segmentation superimposing technique can demodulate the position that temperature variation in every 0.1m length of fibre section and occurrence temperature change in the time that pulse width is 10ns.Describe for example the party's ratio juris above, according to actual sample rate, can realize the resolution of centimetre magnitude.So theoretical analysis and l-G simulation test show, pulse segmentation superimposing technique has solved the problem that spatial resolution and direct impulse width restrict mutually, and spatial resolution is increased to a centimetre magnitude, for distributing optical fiber sensing provides a kind of effective method in high spatial resolution field of detecting.
Claims (1)
1. a pulse segmentation superposed signal disposal route, is characterized in that: the method content comprises the steps:
(1) the backward Brillouin's spectrum subtraction of standard obtaining at the real-time backward Brillouin scattering spectrum collecting and demarcation temperature is obtained to preliminary scattering spectral difference spectrum---overlapped information spectrum, n+1 article of spectral line and n article of spectral line in the scattering spectral difference spectrum of acquisition are done to poor (n=2,3,), so obtain successively the information spectral line of whole optical fiber, obtain every information spectral line frequency corresponding to zero point, finally utilize v
bT=2v-v
b, derive and calculate the Temperature Distribution that can obtain in the every D/n fiber lengths of whole optical fiber through theory; v
bTfor frequency displacement corresponding after temperature variation in spatial resolution, v
bfor the Brillouin shift under room temperature, v is frequency displacement corresponding to the zero point of each spectral line in Information Spectrum; D is spatial resolution, and n is the sampling number in each spatial resolution, depends on sampling rate;
(2) real-time back scattering spectral line is done poorly with demarcating the standard back scattering spectral line obtaining at temperature, obtain overlapped information spectrum;
(3) be one group of spectral line by the overlay information spectrum of acquisition, n+1 article of spectral line and n article of spectral line in this group spectral line are done to poor (n=2,3,) acquired information spectrum, deduct the n article of spectral line all spectral lines before in Information Spectrum with n article of scattering spectral line afterwards, so obtain successively the information spectral line of whole optical fiber;
(4) the frequency displacement v corresponding to zero point of each spectral line in acquired information spectrum, according to formula v
bT=2v-v
b, finally obtain the Temperature Distribution in the every D/n fiber lengths of whole optical fiber;
(5) so far obtain System spatial resolution, this spatial resolution D/n depends on the sample rate of data completely.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1568981A2 (en) * | 2004-02-25 | 2005-08-31 | Korea Advanced Institute of Science and Technology | Physical quantity measuring method using brillouin optical fiber sensor |
| CN101140175A (en) * | 2007-09-28 | 2008-03-12 | 南京大学 | Equivalent pulse spectral analysis method used for enhancing fiber optic sensor spatial resolution |
| CN101144729A (en) * | 2007-09-30 | 2008-03-19 | 南京大学 | Brillouin optical time domain reflection measuring method based on quick fourier transform |
| JP4933981B2 (en) * | 2007-08-14 | 2012-05-16 | 横河電機株式会社 | Optical fiber characteristic measuring device |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1568981A2 (en) * | 2004-02-25 | 2005-08-31 | Korea Advanced Institute of Science and Technology | Physical quantity measuring method using brillouin optical fiber sensor |
| JP4933981B2 (en) * | 2007-08-14 | 2012-05-16 | 横河電機株式会社 | Optical fiber characteristic measuring device |
| CN101140175A (en) * | 2007-09-28 | 2008-03-12 | 南京大学 | Equivalent pulse spectral analysis method used for enhancing fiber optic sensor spatial resolution |
| CN101144729A (en) * | 2007-09-30 | 2008-03-19 | 南京大学 | Brillouin optical time domain reflection measuring method based on quick fourier transform |
Non-Patent Citations (1)
| Title |
|---|
| 王峰 等: "提高布里渊光时域反射应变仪测量空间分辨力的等效脉冲光拟合法", 《光学学报》 * |
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