CN107063433B - Phase-sensitive optical time domain reflectometer and its implementation based on Golay complementary series - Google Patents
Phase-sensitive optical time domain reflectometer and its implementation based on Golay complementary series Download PDFInfo
- Publication number
- CN107063433B CN107063433B CN201710295503.XA CN201710295503A CN107063433B CN 107063433 B CN107063433 B CN 107063433B CN 201710295503 A CN201710295503 A CN 201710295503A CN 107063433 B CN107063433 B CN 107063433B
- Authority
- CN
- China
- Prior art keywords
- phase
- unit
- golay complementary
- signal
- time domain
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 230000000295 complement effect Effects 0.000 title claims abstract description 50
- 230000003287 optical effect Effects 0.000 title claims abstract description 39
- 239000013307 optical fiber Substances 0.000 claims abstract description 36
- 238000000034 method Methods 0.000 claims abstract description 17
- 230000010287 polarization Effects 0.000 claims abstract description 15
- 239000000835 fiber Substances 0.000 claims abstract description 9
- 238000001514 detection method Methods 0.000 claims description 17
- 238000005070 sampling Methods 0.000 claims description 8
- 108091026890 Coding region Proteins 0.000 claims description 6
- 238000005086 pumping Methods 0.000 claims description 2
- 238000011084 recovery Methods 0.000 claims description 2
- 238000012360 testing method Methods 0.000 abstract description 5
- 239000000523 sample Substances 0.000 abstract 2
- 238000007670 refining Methods 0.000 abstract 1
- 238000005259 measurement Methods 0.000 description 16
- 238000000253 optical time-domain reflectometry Methods 0.000 description 16
- 238000012935 Averaging Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000012544 monitoring process Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000001427 coherent effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000010355 oscillation Effects 0.000 description 3
- 230000009897 systematic effect Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 101100127891 Caenorhabditis elegans let-4 gene Proteins 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000009532 heart rate measurement Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optical Communication System (AREA)
Abstract
The present invention relates to a kind of phase-sensitive optical time domain reflectometer based on Golay complementary series, which includes that input light generates unit (1), polarization-maintaining beam splitter (2), coded sequence modulation unit (3), circulator (4), testing fiber (5), homodyne frequency shifter (6), polarization control unit (7), probe unit (8) and signal demodulation unit (9)；The method that phase-sensitive optical time domain reflectometer is realized based on Golay complementary series is also disclosed simultaneously.Probe unit of the present invention has used I/Q demodulating system, can restore whole field informations especially absolute phase information of true backward Rayleigh scattering light effectively in real time with the structure of refining；Its local oscillator gain of light makes the pole weak signal for demodulating optical fiber tail-end become possibility, so this system facilitates the distance sensing of extension system.
Description
Technical Field
The invention relates to a phase-sensitive optical time domain reflectometer, belongs to the field of optical fiber measurement and sensing, and particularly relates to a novel phase-sensitive optical time domain reflectometer based on a Golay complementary sequence and a method for realizing the phase-sensitive optical time domain reflectometer based on the Golay complementary sequence.
Background
Distributed Fiber Optic Sensors (DFOS) have extremely wide application in modern society, and especially have a very important position in the fields of petroleum transmission, power monitoring, large-scale structure safety, national border security and the like. The basic principle of distributed optical fiber sensing is that the change of external environmental factors, such as temperature, vibration, etc., causes the change of the characteristics of the optical fiber, such as refractive index, which further affects the transmission optical field in the optical fiber and changes the scattering optical field in the optical fiber. Therefore, by detecting the characteristics of the scattered light (rayleigh scattered light, brillouin scattered light, or raman scattered light), the affected position of the optical fiber can be obtained, and even the external temperature field or the vibration field can be reduced.
The phase-sensitive optical time domain reflectometer (Φ -OTDR) is one of the most rapidly developed branches in the field of distributed optical fiber sensing, and not only has the characteristics of high precision, high spatial resolution, robustness and insensitivity to external electromagnetic environment, etc. of the distributed optical fiber sensor, but also has the advantages of refined structure, single-ended measurement and capability of restoring an external vibration field, so that the optical time domain reflectometer is widely concerned. One of the most important applications of the phi-OTDR is a distributed acoustic wave sensing (DAS) system, namely, distributed monitoring is carried out according to the capability of the phi-OTDR in restoring an external vibration field, and the distributed monitoring system has great application prospects in the fields of earthquake monitoring, high-speed rail measurement and the like.
The principle of Φ -OTDR is as follows: after the narrow pulse output by the coherent light source enters the optical fiber to be detected, the narrow pulse continuously returns to the input end (point 0) along the backward Rayleigh scattered light (Rayleigh light) of the optical fiber; rayleigh light with the length of half pulse width on the optical fiber at a certain specific moment is coherent at a point 0, and finally the system is output; if the external vibration field changes, the frequency and the amplitude of the external vibration field are in direct proportion to the phase difference between two Rayleigh light points (one point is positioned before the disturbance influence, and the other point needs to pass through the disturbance position); the external vibration field can be recovered by demodulating the phase of the sensing system. From the principle of Φ -OTDR, it can be seen that the spatial resolution of this system is half the pulse width; and the system has high real-time performance, and can realize dynamic measurement by continuously driving pulses.
However, existing Φ -OTDRs have certain limitations. Higher input pulse peak power generally brings higher signal-to-noise ratio of the sensing signal, however, the high pulse peak power causes signal damage due to the generation of fiber nonlinearity phenomenon, and therefore the peak power of the input pulse needs to be limited; the system to achieve high spatial resolution may not have the pulse width too large. The two defects are key problems to be solved for realizing the long-distance phi-OTDR real-time measurement. The signal-to-noise ratio of the sensing signal can be improved to a certain extent by increasing the average times, so that the sensing distance is prolonged; however, excessive averaging times will sacrifice real-time performance and decrease the maximum detectable frequency, which highlights the necessity of applying optical pulse encoding techniques in long-distance Φ -OTDR systems.
Golay complementary sequence is one kind of related code, and is used in communication field and sensing field. The code is characterized in that the correlation between code words is used for solving the response of a single pulse. The Golay complementary sequence is a bipolar code, i.e., consisting of "+ 1" and "-1"; the Golay complementary sequence comprises two rows, each row having a codeword length N that is a positive power of 2. Let two rows of Golay complementary sequences be a and B. The Golay complementary sequence conforms to the correlation property shown in formula (1).
"⊕" in the formula (1) represents autocorrelation operation, N is the length of a single row of code words, k represents the number of shift bits when correlation operation is performed, and | k | ≦ N.
As shown in the formula (1), the multiple of the unit impact function can be obtained after the correlation operation is carried out on the two rows of code words of the Golay complementary sequence; and because the convolution of the delta function with any function is equal to the function itself, if a system can be written in the form of convolution, i.e. a linear system, then the system can use Golay's complementary sequence for encoding.
The Golay complementary sequence has the advantages of long-distance phi-OTDR application, Golay firstly has high coding gain compared with a single pulse, and the signal-to-noise ratio of demodulated signals of N bits Golay coding compared with single pulse averaging N times is improvedSince the unipolar Golay complementary sequence is always 4 rows, Golay requires the same measurement time as the single-pulse averaging of 4 measurements. For example, 128 bit Golay complementary sequence (N is 128), the signal-to-noise ratio of the code-demodulated signal is improved compared with the signal obtained by averaging 128 times of single pulseThe measurement time of about 5.6dB is 1/32 times the average elapsed time of 128 times. Golay's complementary sequences can both save measurement time and improve the signal-to-noise ratio of the measurement signal compared to single-pulse averaging. Golay has the greatest advantage over other coding schemes in that its measurement time does not increase with increasing number of code bits, and it requires a measurement time that is always the time required for 4 averages of a single pulse. For example, compared with another broader Simplex coding method applied to a distributed optical fiber sensing system, N-bit Simplex coding requires a measurement time of N times per pulse. Therefore, the measurement time required by comparing with other Golay complementary sequences does not increase with the increase of the coding length, which ensures the response speed of the system in a long-distance phi-OTDR system.
The coding at the coding strength on the phase of the comparison enables a return to zero codeword, so that intersymbol interference can be prevented. Specifically, the adjacent code words are separated by at least one pulse width so as not to cause the signal responses of the two code words to overlap at a certain position, and the zero-returning code of the intensity modulation can meet the condition only if the zero-returning code is properly set. Phase encoding has a problem of inter-symbol crosstalk because it cannot implement a return-to-zero code. Therefore, the system adopts the intensity coding mode.
Disclosure of Invention
In order to overcome the technical problem that the phase-sensitive optical time domain reflectometer in the prior art is limited in peak power and spatial resolution, the invention provides the phase-sensitive optical time domain reflectometer based on the Golay complementary sequence, and the optical time domain reflectometer can quickly and efficiently restore the frequency and amplitude information of an external vibration field and break through the limitation of the peak power and the spatial resolution in the phase-sensitive optical time domain reflectometer; meanwhile, the invention also discloses a method for realizing the phase-sensitive optical time domain reflectometer based on the Golay complementary sequence.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the phase-sensitive optical time domain reflectometer based on the Golay complementary sequence comprises an input light generating unit, a polarization-preserving beam splitter, a coding sequence modulation unit, a circulator, an optical fiber to be detected, a homodyne frequency shifter, a polarization control unit, a detection unit and a signal demodulation unit;
wherein,
the input light generating unit, the polarization-preserving beam splitter, the homodyne frequency shifter, the polarization control unit, the detecting unit and the signal demodulating unit are sequentially in signal connection;
the polarization-maintaining beam splitter is also sequentially connected with the coding sequence modulation unit, the circulator and the optical fiber to be detected, and the circulator and the detection unit are in signal connection with each other.
Compared with the prior art, the invention has the beneficial effects that: the detection unit of the invention uses an I/Q demodulation system, and can effectively reduce all light field information, especially absolute phase information, of real backward Rayleigh scattering light in real time by using a refined structure; meanwhile, the local oscillator optical gain makes it possible to demodulate the extremely weak signal at the tail end of the optical fiber, so the system is beneficial to prolonging the sensing distance of the system.
Meanwhile, based on the Golay complementary sequence-based phase-sensitive optical time domain reflectometer, the invention also discloses a method for realizing the phase-sensitive optical time domain reflectometer based on the Golay complementary sequence, which comprises the following steps:
1) the 4 rows of Golay complementary sequences which are subjected to intensity modulation and are suitable for the unipolar system are driven into the optical fiber to be detected, and backward Rayleigh scattering optical signals are received;
2) collecting backward Rayleigh scattering optical signals of the optical fiber to be detected as the system response of each row, performing autocorrelation operation decoding on the system responses of the 4 rows of Golay complementary sequences, and recovering to obtain single-pulse phase responses;
3) the obtained monopulse phase response is subjected to unwrapping operation to obtain phase information, and a phase difference between two sampling points of the monopulse is obtained; and periodically pumping Golay complementary sequences to obtain the variation of the phase difference between two sampling points along with time, and recovering the frequency and amplitude of the external vibration according to the direct proportion relation between the phase difference and the frequency and amplitude of the external vibration.
In step 2) of the above method, the method for recovering the monopulse phase response is as follows:
let 4 rows of Golay complementary sequences for a unipolar system hit in the fiber under test be A1、A2And B1、B2The corresponding obtained 4-row sequence system response is respectively RA1(t)、RA2(t) and RB1(t)、RB2(t)；
The rayleigh scattered light signal response based on the 4-row sequence will recover a single codeword (single pulse) system response, and the recovery formula is shown as expression (3).
In the formula,
⊕ denotes a cross-correlation operation;
w (t) represents the single-pulse response of the phase-sensitive optical time domain reflectometer.
Preferably, the Golay complementary sequence is encoded using intensity nulling.
Preferably, in the Golay complementary sequence with intensity return to zero, the length of return to zero between code words is larger than the length of one code word when the Golay complementary sequence is actually set.
Based on the method, the invention only uses 4 times of time of single pulse measurement to complete better effect than average N (N is the length of a single row code word of the Golli complementary sequence), and ensures the real-time performance of the phi-OTDR system; the corresponding spatial resolution is half of the width of a single code word, so that the method improves the average power of an input signal under the condition of ensuring the spatial resolution, further enables the signal to be transmitted farther and is beneficial to long-distance sensing; compared with other coding modes, the measurement time of the Golay complementary sequence cannot be increased along with the increase of the number of the coding bits, so that the response speed of the whole set of system and the quick dynamic measurement of the system are guaranteed.
Drawings
FIG. 1 is a schematic diagram of a linear system phase sensitive optical time domain reflectometer;
FIG. 2 is a diagram illustrating that the length of the return-to-zero between codewords may not be less than one codeword length;
FIG. 3 is a block diagram of a system architecture for implementing a phase-sensitive optical time domain reflectometer using Golay complementary sequences;
FIG. 4 is a graph of the experimental effect of Rayleigh scattered light intensity response AC components obtained by driving 4 rows of Golay complementary sequences;
FIG. 5 is a graph showing the experimental effect of the phase difference change with time after a specific frequency disturbance is added to the fiber under test;
FIG. 6 is a frequency domain diagram of demodulating an external disturbance signal after adding a disturbance of a specific frequency to the fiber under test;
the labels in the figure are: 1. an input light generating unit; 2. a polarization maintaining beam splitter; 3. a coded sequence modulation unit; 4. a circulator; 5. an optical fiber to be tested; 6. a homodyne frequency shifter; 7. a polarization control unit; 8. a detection unit; 9. a signal demodulation unit.
Detailed Description
The invention will be further described with reference to the accompanying drawings. Embodiments of the present invention include, but are not limited to, the following examples.
First, the phase is explainedThe demodulated phase sensitive optical time domain reflectometer (Φ -OTDR) is a linear system. Linear systems are the basis and precondition for the possibility of implementing coding. Setting the code word repetition period (bit rate) to be the same as the sampling time interval (sampling rate); setting the phi-OTDR system response of a pulse with amplitude of 1 and initial phase of 0 as r (t); let an arbitrary code sequence of length S +1 beIf the total number of points sampled on the optical fiber is H +1, the single-pulse system response is r (t) ═ r0exp(jρ0)，...，rHexp(jρH)]T. Fig. 1 schematically illustrates the response of the system when S is 2 and H is 1. The code word in FIG. 1 is [1, 1 ]]TThe curves labeled ①, ②, and ③ correspond to the systematic responses of the 1 st, 2 nd, and 3 rd codewords, respectively, it can be seen from fig. 1 that the length of the systematic response to the code r (t) should be S + H +1, i.e., the length of the systematic response to the code r (t) should be S + H +1
R(t)＝[R(t0)，...，R(tS+H)]T. The general situation can be inferred from fig. 1. The response of the phi-OTDR system to an arbitrary code sequence can be represented by equation (4).
As can be seen from the definition of convolution, the matrix representation of equation (4) can be equivalent to a convolution operation, as shown in equation (5).
R＝A*r (5)
Equation (5) indicates convolution operation. Since the response of the phi-OTDR system to encoding can be expressed as a convolution operation, the phase-demodulated phi-OTDR system is a linear system.
If two adjacent codewords are injected into the optical fiber, the time for the first (second) codeword to completely enter the optical fiber is α Δ t (β Δ t), as shown in fig. 2, the region labeled ① (②) represents the relationship between the position of the first (second) codeword received at the receiving end from the optical fiber under test and the sampling duration, as can be seen from fig. 2, if the region ① does not coincide with the region ②, α and β need to satisfy the relationship shown in formula (6).
β≥α+1 (6)
As can be seen from fig. 2 and equation (6), the length of zero between two adjacent codewords needs to be greater than a codeword length Δ t, otherwise, for a certain position, signals of two codewords will generate aliasing, and the system loses linearity.
Based on the above, the Golay complementary sequence based phase-sensitive optical time domain reflectometer is described below with reference to fig. 3:
the phase-sensitive optical time domain reflectometer based on the Golay complementary sequence comprises an input light generating unit 1, a polarization-preserving beam splitter 2, a coding sequence modulation unit 3, a circulator 4, an optical fiber to be detected 5, a homodyne frequency shifter 6, a polarization control unit 7, a detection unit 8 and a signal demodulation unit 9; the input light generating unit 1, the polarization-maintaining beam splitter 2, the homodyne frequency shifter 6, the polarization control unit 7, the detection unit 8 and the signal demodulation unit 9 are sequentially in signal connection; the polarization-preserving beam splitter 2 is also sequentially connected with the coding sequence modulation unit 3, the circulator 4 and the optical fiber 5 to be detected, and the circulator 4 and the detection unit 8 are in signal connection with each other.
In the above-mentioned phase-sensitive optical time domain reflectometer, the polarization maintaining beam splitter 2 includes a path of input end a, two paths of output ends b, and an output end c, and the circulator 4 includes a path of input end a ', two paths of output ends b ', and an output end c '.
The input light generation unit 1 generates an optical signal as input light; the polarization-maintaining beam splitter 2 divides the light signal output by the light generating unit input at the input end a into two paths under the condition of not changing the polarization state of the input light signal, wherein one path output by the output end b is used as the signal light input into the optical fiber to be detected, and one path output by the output end c is used as the local oscillation light required by coherent demodulation; the coded sequence modulation unit 3 modulates the signal light output from the port b of the polarization-maintaining beam splitter 2 into a Golay complementary sequence; the circulator 4 inputs the modulated sequence from the input end a 'to the optical fiber to be tested connected with the output end b'; backward Rayleigh scattered light of the optical fiber 5 to be detected is output to an output end c 'from an output end b' of the circulator 4; the homodyne frequency shifter 6 performs frequency shift processing on the optical signal which is output by the output end c of the polarization-maintaining beam splitter 2 and is used as local oscillator light, so that the frequency of the optical signal is the same as that of backward Rayleigh scattering light; the polarization control unit 7 adjusts the polarization state of the continuous light output from the homodyne frequency shifter, so that the detection unit has the optimal local oscillation light gain; the detection unit 8 mixes backward Rayleigh scattered light (namely a signal to be detected) output by the output end c' of the circulator 4 with intrinsic light output by the polarization control unit by using an I/Q demodulation technology, and finally outputs a Golay complementary sequence backward Rayleigh scattered light field with local oscillator light gain; the signal demodulation unit 9 demodulates the backward Rayleigh scattering light field with the local oscillator light gain output by the detection unit to obtain single pulse response; and then, the phase difference between sampling points is obtained by calculating the phase of the backward Rayleigh scattering light, so that the amplitude and the frequency of an external vibration field are reduced.
When the phase-sensitive optical time domain reflectometer is used, the input power of the input light generating unit 1 is adjusted firstly, namely the peak power of a code word is input later, then the input power is input into the code sequence modulating unit through the output end b of the polarization-preserving beam splitter 2 to generate a Golay complementary sequence, and then the input power is input into an optical fiber to be detected through the output end b' of the circulator 4. The backward rayleigh scattered light is input to the detection unit 8 through the output end c' of the circulator 4 and the local oscillation light optimized by the homodyne frequency shifter 6 and the polarization control unit 7 for I/Q modulation, so that the signal light and the intrinsic light are mixed, and the rayleigh scattered light field is input. The detection signal finally enters a signal demodulation unit 9, a single pulse response is demodulated, then a signal phase is demodulated through an uncoiling algorithm, and the frequency and the amplitude of an external vibration field are restored according to the phase difference.
The following describes the use of the phase-sensitive optical time domain reflectometer with reference to specific examples.
Setting the length of the optical fiber to be detected as 2 km; the duration of a single codeword (single pulse) is 80ns, and the corresponding spatial resolution is about 8 m; the repetition period of the code words is 40 mus; the single row length of the Golay complementary sequence is 32 bits.
A90-degree optical mixer and two detectors with the bandwidth of 10M are used for forming a detection unit 8 for I/Q demodulation. A piezoelectric ceramic (PZT) wound by 10m optical fiber is added at the tail end of the optical fiber for simulating an external vibration field, and the external applied vibration frequency is 355 Hz.
Fig. 4 shows the intensity of the backward rayleigh scattered light (dc response is abolished) for 4 rows of code words output from the detection unit after the Golay complementary sequence for the unipolar system is hit. Fig. 4(a), (b), (c) and (d) show the intensity of the backward rayleigh scattered light detected at point 0 after the code words of lines 1, 2, 3 and 4 of the Golay complementary sequence have been hit in the sensing system, respectively. As can be seen from fig. 4, the response of each row of code words has the following trend: the strength is greater in the middle and lower at the ends. This is due to the fact that the front-end code word has not yet completely "entered" into the fiber and the back-end already has a partial code word "exited" out of the fiber. Since a larger intensity results in a better demodulation signal-to-noise ratio, it can be seen from fig. 4 that the Golay complementary sequence is a significant help for the intensity enhancement of the signal.
Fig. 5 and fig. 6 respectively show time domain and frequency domain signals of the external vibration field demodulated by the signal demodulation unit. FIG. 5 shows the relationship between time and phase difference; the demodulation curve in fig. 5 is sinusoidal in form, in remote concert with the signal applied to the trailing PZT. Fig. 6 shows a frequency domain signal corresponding to the demodulated time domain signal shown in fig. 5, and it can be seen from fig. 6 that the demodulated signal has a peak value around 355Hz and exhibits a high signal-to-noise ratio. Fig. 5 and 6 prove that the system can restore the external vibration field to a higher degree.
The above description is an embodiment of the present invention. The foregoing is a preferred embodiment of the present invention, and the preferred embodiments in the preferred embodiments can be combined and used in any combination if not obviously contradictory or prerequisite to a certain preferred embodiment, and the specific parameters in the embodiments and examples are only for the purpose of clearly illustrating the invention verification process of the inventor and are not intended to limit the patent protection scope of the present invention, which is subject to the claims and the equivalent structural changes made by the content of the description and the drawings of the present invention are also included in the protection scope of the present invention.
Claims (3)
1. The method for realizing the phase-sensitive optical time domain reflectometer based on the Golay complementary sequence comprises an input light generating unit (1), a polarization-preserving beam splitter (2), a coding sequence modulating unit (3), a circulator (4), an optical fiber to be tested (5), a homodyne frequency shifter (6), a polarization control unit (7), a detection unit (8) and a signal demodulating unit (9); the input light generating unit (1), the polarization-maintaining beam splitter (2), the homodyne frequency shifter (6), the polarization control unit (7), the detection unit (8) and the signal demodulation unit (9) are sequentially in signal connection; the polarization-preserving beam splitter (2) is also sequentially connected with the coding sequence modulation unit (3), the circulator (4) and the optical fiber (5) to be detected, and the circulator (4) and the detection unit (8) are in signal connection with each other;
the method is characterized by comprising the following steps:
1) 4 rows of Golay complementary sequences which are subjected to intensity modulation and are suitable for a unipolar system are driven into an optical fiber (5) to be detected, and backward Rayleigh scattering light signals are received;
2) collecting backward Rayleigh scattering optical signals of an optical fiber (5) to be detected as the system correspondence of each row, performing autocorrelation operation decoding on the system responses of the 4 rows of Golay complementary sequences, and recovering to obtain single pulse phase responses;
the recovery method of the single-pulse phase response is as follows:
the complementary sequence of intensity modulation Golay for a unipolar system is A, assuming 4 rows of fibers (5) to be tested1、A2And B1、B2The corresponding obtained 4-row sequence system response is respectively RA1(t)、RA2(t) and RB1(t)、RB2(t)；
The rayleigh scattered light signal response based on the 4-row sequence will recover a single codeword, i.e. the system response of a single pulse, with the following formula:
in the formula,representing a cross-correlation operation;
w (t) represents the single pulse response of the phase-sensitive optical time domain reflectometer;
3) the obtained monopulse phase response is subjected to unwrapping operation to obtain phase information, and a phase difference between two sampling points of the monopulse is obtained; and periodically pumping Golay complementary sequences to obtain the variation of the phase difference between two sampling points along with time, and recovering the frequency and amplitude of the external vibration according to the direct proportion relation between the phase difference and the frequency and amplitude of the external vibration.
2. The method of claim 1, wherein the Golay complementary sequence is encoded using intensity nulling.
3. The method of claim 2, wherein the length of the zero-return between codewords is larger than the length of one codeword when the Golay complementary sequence with zero-return strength is actually set.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710295503.XA CN107063433B (en) | 2017-04-28 | 2017-04-28 | Phase-sensitive optical time domain reflectometer and its implementation based on Golay complementary series |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710295503.XA CN107063433B (en) | 2017-04-28 | 2017-04-28 | Phase-sensitive optical time domain reflectometer and its implementation based on Golay complementary series |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN107063433A CN107063433A (en) | 2017-08-18 |
| CN107063433B true CN107063433B (en) | 2019-06-25 |
Family
ID=59605230
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710295503.XA Active CN107063433B (en) | 2017-04-28 | 2017-04-28 | Phase-sensitive optical time domain reflectometer and its implementation based on Golay complementary series |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN107063433B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107782346B (en) * | 2017-10-27 | 2019-08-27 | 武汉理工大学 | Large-scale optical fiber grating sensing network demodulation system and method based on Gray code |
| CN109579887A (en) * | 2018-12-04 | 2019-04-05 | 上海第二工业大学 | A kind of time division multiplex optical fiber grating sensing system and method based on composite coding |
| CN109506686B (en) * | 2018-12-19 | 2021-03-23 | 武汉理工光科股份有限公司 | Method for improving detection performance of isotactic fiber bragg grating |
| US10727937B1 (en) * | 2019-03-01 | 2020-07-28 | Huawei Technologies Co., Ltd. | Multi-layer encoding of optical signals |
| CN112414584B (en) * | 2020-10-19 | 2022-11-22 | 太原理工大学 | Brillouin optical time domain analysis device and method based on pi-pulse Gray code coding |
| CN114061736B (en) * | 2021-11-18 | 2022-11-25 | 北京邮电大学 | Rayleigh distributed phase demodulation optical fiber sensing method and system based on frequency and intensity encoding and decoding |
| CN114838804B (en) * | 2022-05-09 | 2023-06-09 | 武汉理工大学 | Distributed vibration measuring device and method based on weak grating array and pulse coding |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63275916A (en) * | 1987-05-08 | 1988-11-14 | Nec Corp | Optical fiber hydrophone |
| JP2009156718A (en) * | 2007-12-27 | 2009-07-16 | Yokogawa Electric Corp | Optical pulse testing device |
| CN101765763A (en) * | 2007-07-27 | 2010-06-30 | 泰科电子海底通信有限责任公司 | System and method for optical time domain reflectometry using multi-resolution code sequences |
| CN102761364A (en) * | 2011-04-29 | 2012-10-31 | 华为海洋网络有限公司 | Method and device for detecting optical time domain detection signal |
| CN103217226A (en) * | 2013-03-26 | 2013-07-24 | 太原理工大学 | Passive homodyne demodulation device and passive homodyne demodulation method for fai-OTDR (optical time domain reflectometer) |
| CN103900623A (en) * | 2014-04-16 | 2014-07-02 | 武汉理工光科股份有限公司 | Optical time domain reflectometer based on double acoustic-optical modulators and common-mode rejection method of optical time domain reflectometer |
| CN105466548A (en) * | 2015-12-16 | 2016-04-06 | 上海大学 | Phase sensitive optical time domain reflection fiber sensing system positioning method |
-
2017
- 2017-04-28 CN CN201710295503.XA patent/CN107063433B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63275916A (en) * | 1987-05-08 | 1988-11-14 | Nec Corp | Optical fiber hydrophone |
| CN101765763A (en) * | 2007-07-27 | 2010-06-30 | 泰科电子海底通信有限责任公司 | System and method for optical time domain reflectometry using multi-resolution code sequences |
| JP2009156718A (en) * | 2007-12-27 | 2009-07-16 | Yokogawa Electric Corp | Optical pulse testing device |
| CN102761364A (en) * | 2011-04-29 | 2012-10-31 | 华为海洋网络有限公司 | Method and device for detecting optical time domain detection signal |
| CN103217226A (en) * | 2013-03-26 | 2013-07-24 | 太原理工大学 | Passive homodyne demodulation device and passive homodyne demodulation method for fai-OTDR (optical time domain reflectometer) |
| CN103900623A (en) * | 2014-04-16 | 2014-07-02 | 武汉理工光科股份有限公司 | Optical time domain reflectometer based on double acoustic-optical modulators and common-mode rejection method of optical time domain reflectometer |
| CN105466548A (en) * | 2015-12-16 | 2016-04-06 | 上海大学 | Phase sensitive optical time domain reflection fiber sensing system positioning method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN107063433A (en) | 2017-08-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107063433B (en) | Phase-sensitive optical time domain reflectometer and its implementation based on Golay complementary series | |
| CN102636251B (en) | Phase sensitivity light time domain reflection system and method for improving SNR (signal to noise ratio) thereof | |
| CN109489801B (en) | Multi-core optical fiber distributed acoustic wave sensing system based on space division multiplexing | |
| Pan et al. | Interference-fading-free phase-demodulated OTDR system | |
| CN105004355B (en) | Phi-OTDR reinforcing method based on polarized orthogonal optical pulse pair and device thereof | |
| CN109540280B (en) | Signal processing method for improving efficiency of phase-sensitive optical time domain reflection system | |
| CN106768277B (en) | A kind of demodulation method of distributed optical fiber vibration sensing device | |
| CN109297425B (en) | Brillouin optical time domain reflectometer modulated by physical random number | |
| CN112713929A (en) | Optical time domain reflectometer based on chirped pulses | |
| CN109579887A (en) | A kind of time division multiplex optical fiber grating sensing system and method based on composite coding | |
| CN104158587A (en) | Optical time domain reflect method based on period on-off key chaos signals | |
| CN106953687B (en) | POTDR system based on Simplex coding and signal determination method thereof | |
| Shiloh et al. | Highly-sensitive distributed dynamic strain sensing via perfect periodic coherent codes | |
| CN102564481A (en) | Method and device for improving signal-to-noise ratio of distributed optical fiber Brillouin sensor | |
| Li et al. | Broadband vibration signal measurement based on multi-coset sampling in phase-sensitive OTDR system | |
| Liu et al. | Golay coding Φ-OTDR with distributed frequency-drift compensation | |
| CN103954378A (en) | BOTDR system based on Bark sequences and long-distance detection method thereof | |
| CN106610303A (en) | BOTDR sensing method and system based on FFT and coding | |
| CN114111860B (en) | Distributed phi-OTDR sensing method and system based on multi-frequency pulse coding | |
| CN116086591A (en) | Distributed acoustic wave sensing method and system using time-frequency multiplexing and phase base value reference | |
| Wu et al. | Bipolar coding for phase-demodulated Φ-OTDR with coherent detection | |
| Gu et al. | Performance comparison of combining algorithms for polarization-diversity receiving in phase-sensitive OTDR | |
| Zhao et al. | Frequency Multiplexed Scheme for Optical Pulse-Coding φ-OTDR Based on Golay Complementary Sequence | |
| CN114485905A (en) | Distributed optical fiber vibration and strain sensing method based on optical signals with different pulse widths | |
| Hong et al. | Large dynamic strain measurement in Φ-OTDR based on ultra-weak FBG array |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |