Distributed strain measurement method with frequency selective damping.
Patent Information
- Authority / Receiving Office
- TR · TR
- Patent Type
- Applications
- Current Assignee / Owner
- BILKENT UNIVERSITY
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-22
Abstract
Description
1 TARIFF Distributed strain measurement method with frequency selective damping. RELATED TECHNICAL FIELD This invention relates to a fiber optic-based distributed strain measurement method, specifically a dual-pulse method. 5 using phase optical time domain reflectometer (OZAR) on a long optical fiber line The aforementioned dual-pulse phase enables measurements with nano-strain sensitivity. Measuring Rayleigh scattering of optical signals in OZAR provides scattering data. recording, reducing the frequency of the aforementioned Rayleigh scattering to radio frequency, Obtaining the optical signal spectrum using the numerical Fourier transform is related to the aforementioned Rayleigh method. the scattering undergoes frequency-selective damping and the damping occurs in 10 The steps involved in obtaining the strain value by measuring the change in frequencies. This relates to the distributed strain measurement method with frequency-selective damping. STATE OF THE ART Optical fiber is a 15-bit or 15-bit material that enables light to be transmitted from one point to another with low power loss. It is a material. As light passes through a fiber, it affects regions in the fiber that have different densities. It undergoes scattering. The main mechanisms causing this scattering are Rayleigh scattering, These are Brillouin scattering and Raman scattering. Rayleigh and Brillouin scattering; a laser source, a The measurement is taken using a light modulator and a detector, along a long line. It can display regional strain values. The sensors that measure these scatterings have 20 on their surface. These are sensors used to measure strains occurring within the structure in which they are located; The strain information provided by the sensors depends on the structure of the measured surface and the agents acting on that surface. It provides information about changes in environmental factors. Wheatstone Bridge, Compared to electronic devices such as piezoelectric materials, optics It has been observed that the systems are able to perform measurements with higher accuracy and in a distributed manner. 25 This allows for highly accurate strain measurement over a large area using a single fiber. It is possible to do so. In the relevant technical field, there are also other optical measurement methods developed for strain measurement. These include, one of which is the use of fiber Bragg grating. Fiber Bragg gratings This is achieved by periodic changes in the optical index along the optical path. The 30 in question... Due to their structure, grids allow light within a specific frequency range to pass through while blocking other frequencies. It reflects light. By changing the optical frequency of the light sent to the grids, the light from the grid is altered. There are frequencies that it does not transmit. In the event of strain occurring on the structure, 2 The core frequency of the grid shifts. By tracking the frequency shift, the strain on the structure can be determined. is being measured. This is based on publication number US7418171 B2, which is included in the known state of the art. A United States patent document describes fiber Bragg grid sensors. This is done by monitoring the shifting of the grid center when stress occurs in the structure. It is explained that strain is measured. In this method, fiber 5 is used along the line to be measured. The placement of Bragg gratings and the use of a wavelength-variable light source. It is required. Within the scope of the method described in the invention, which is detailed below. Measurements can be made using light sources with a fixed wavelength, thus allowing measurements to be placed on the fiber. The need for special structural placement is eliminated. However, Fiber Bragg In the method using grids, data is only collected from the locations where grids are located along the line. while it can be obtained from any part of the line with the invention described in detail below. It becomes possible to obtain data. Another method used for strain measurement is Brillouin scattering, United States patent with publication number US10677616 B2 included in the previous technique The document describes a strain measurement method using Brillouin scattering. This is document 15. According to the method, optical pulses are injected into the fiber, and the transmitted light interacts with acoustic phonons. It passes through and is scattered at a lower or higher frequency. The frequency of the scattered light, It depends on temperature and strain factors; strain information can be obtained by monitoring this frequency. This is obtained using Brillouin scattering on a standard fiber at a wavelength of 1,550 nm. Strain information can be obtained with a sensitivity of 41 kHz / με along the line. Details are given below. Thanks to the method described in the invention, which is explained in document US10677616 B2. The Brillouin scattering described has a lower bandwidth than the photon according to the method used. Measurements can be made using the sensor unit, with a strain sensitivity of 151 MHz / με. It is higher. In the relevant technical field, in addition to the methods given above, strain measurement using Rayleigh scattering is also used. There are also various studies on the measurement method. In Rayleigh scattering, on the fiber... A pulse is sent, and the brightness of the reflected light is measured over time. In fiber optics... In the case of strain, the perceived brightness changes. In this method, optical frequency by modifying it to obtain the curve closest to the reference distance-brightness line. Studies are being conducted. The frequency at which the closest curve in question is obtained is 30 times the strain value. It provides an estimate. In current coherent optical time-domain reflectometry, the pair Studies are being conducted on strain measurement using the frequency method [1]. According to this method Distributed acoustic sensors are interrogated at two different optical frequencies, and the results obtained from these interrogations are... The covariance of the delay times of the obtained waveforms is calculated. Strain 35 is also calculated by determining the delay period at which the covariance has its highest value. 3 The value is obtained. This method is described in the invention detailed below. It is slower than the previous method. In the current invention, the optical frequency is reduced to radio frequency. This allows frequency changes caused by strain to be detected in just two consecutive measurements. This can be obtained using [method]. This step eliminates the need for covariance calculation. This allows measurements to be made at the Nyquist frequency. For example; 5 The invention, detailed below, describes a method that enables the production of 500 µs. When measurements are taken at intervals, a strain change of 1 kHz can be measured. In conclusion, beyond the methods described above in the known state of the art, there are more This will eliminate the problems encountered by enabling precise strain measurement. And a new method is needed to provide a solution to the problem. For this, 10 In the invention described in detail below, the spectrum of light undergoing Rayleigh scattering Nano-strain accuracy in strain measurement using frequency-selective damping. This is made possible by simple hardware requirements, signal processing and method. a strong alternative to current techniques due to its ease of application is presented. 15 Article Reference Used in the State of the Art [1] Liehr, Sascha, Yonas Seifu Muanenda, Sven Münzenberger, and Katerina Krebber. "Relative change measurement of physical quantities using dual-wavelength coherent OTDR." Optics express 25, no. 2 (2017): 720-729. PURPOSE OF THE INVENTION AND A BRIEF DESCRIPTION OF THE INVENTION This invention relates to a fiber optic-based distributed strain measurement method, specifically a dual-pulse method. Phase optical time domain reflectometry (OZAR) on a long optical fiber line The aforementioned dual-pulse phase enables measurements with nano-strain sensitivity. Measuring Rayleigh scattering of optical signals in OZAR, scattering data 25 recording, reducing the frequency of the aforementioned Rayleigh scattering to radio frequency, Obtaining the optical signal spectrum using the numerical Fourier transform is related to the aforementioned Rayleigh method. the scattering undergoes frequency-selective damping and where damping occurs The steps involved in obtaining the strain value by measuring the change in frequencies. This relates to the distributed strain measurement method with frequency-selective damping. 30 The primary aim of the invention is to analyze the frequency-selective fading spectrum in Rayleigh scattering. Nano-strain analysis using strain-optical theory based on frequency variations in regions. The goal is to develop a distributed strain measurement method that enables measurements with high accuracy. 4 One aim of the invention is to use a dual-pulse phase optical time-domain reflectometer (OZAR). It reduces optical frequency to radio frequency and enables the analysis of frequency changes. The aim is to develop a distributed strain measurement method using frequency-selective damping. One aim of the invention is to analyze the optical frequency variation occurring in the strain region in fiber optics. 5 that enable measurement with products used as standard in communication methods. The aim is to develop a distributed strain measurement method using frequency-selective damping. Another purpose of the invention was to eliminate the need for covariance calculation by eliminating the Nyquist method. Frequency-selective damping enables measurements at a specific frequency and distributes strain. The goal is to develop a measurement method. Another purpose of the invention is to make it possible to receive data from any part of the fiber optic line. Measurement with nano-strain sensitivity using frequency-selective damping. The goal is to develop a distributed strain measurement method that enables this. Another purpose of the invention is to enable data collection from a long fiber optic cable. or enables the measurement of regional or overall strains occurring in large structures. The aim is to develop a distributed strain measurement method with frequency-selective damping. 15 All the advantages mentioned above and which will be understood from the detailed explanation below. The present invention aims to realize a fiber optic-based distributed strain sensor (DGS). a long-term study using a dual-pulse phase optical time-domain reflectometer (OZAR) in the device Nano-strain sensitivity using frequency-selective damping in optical fiber lines. It relates to a distributed strain measurement method that enables measurements, and specifically; 20 - generation of optical signal, frequency difference (Δf) between pulse pair and delay its duration is determined by the modulation signal sent to the optical modulator, - the aforementioned optical signal is used as a sensor with the help of an optical circulator. sequentially injected into the fiber optic line, - The paths taken by successive pulses in the optical signal are different within the fiber optic cable, 25 Reflection by Rayleigh scattering, - Measurement of the aforementioned Rayleigh scattering using a photodetector unit, - Processing and recording the measured scattering data via the data acquisition card, - reducing the frequency of the aforementioned Rayleigh scattering to radio frequency, - Optical signal detected by the photodetector unit via numerical Fourier transform 30 obtaining the spectrum, - Change in refractive index (Δn) after voltage is applied and the light path on the fiber optic cable The duration of light passing through the photodetector unit (Δx / c) due to the effect of the change (Δx) along its path arriving so late, - due to the phase difference caused by this time difference, in the photodetector unit shift in extinction frequencies in the measured optical signal spectrum, - the aforementioned Rayleigh scattering undergoes frequency-selective damping and the amount of slip and the direction of slip at the frequencies where damping occurs measuring the change, and 5 - the process of obtaining the strain value in units of με from these measurement results It includes the steps. The structural and characteristic features and all the advantages of the invention are given in the figures below. Thanks to the detailed explanation written with references to the figures, it becomes clearer. This will be understood, and therefore the evaluation should also take these forms and detailed explanations into account. 10 It needs to be done by taking precautions. BRIEF DESCRIPTION OF THE FIGURES The invention concerns an example of a distributed strain measurement method using frequency-selective damping. The applications are shown in the attached figures, of which: 15 Figure 1. A diagram of the distributed strain sensor (DSS) device assembly, which is the subject of the invention. This is an example block diagram. Figure 2. Steps for obtaining strain information in the DGS device that is the subject of the invention. This is an example flowchart related to the topic. Figure 3. Scattering detected from a region of the fiber optic line with the DGS device, which is the subject of the invention. 20 a data spectrum showing the change over time in the absence of strain This is an example graph. Figure 4. Scattering detected from a region of the fiber optic cable using the DGS device, which is the subject of the invention. the data spectrum was analyzed by applying strain at a frequency of 0.1 Hz and an amplitude of 0.2 με. This is an example graph showing the change over time. 25 Figure 5. Scattering detected from a region of the fiber optic cable using the DGS device, which is the subject of the invention. Strain information obtained from the spectrum of the data is 0.03 με at a frequency of 200 Hz. amplitude showing the change over time when strain is applied. This is an example graph. The parts in the figures are individually numbered, and the corresponding numbers are listed below. 30 It has been given. DGS device (100) 6 light source (1) high power optical amplifier (2) optical modulator (3) optical circulator (4) high gain optical amplifier (5) 5 optical band-pass filter (6) photo sensor unit (7) data collection card (8) modulation signal (9) fiber line (10) 10 DETAILED DESCRIPTION OF THE INVENTION This invention relates to a fiber optic-based distributed strain measurement method, specifically a dual-pulse method. Phase optical time domain reflectometry (OZAR) on a long optical fiber line The aforementioned dual-pulse phase 15 enables measurements with nano-strain sensitivity. Measuring Rayleigh scattering of optical signals in OZAR provides scattering data. recording, reducing the frequency of the aforementioned Rayleigh scattering to radio frequency, Obtaining the optical signal spectrum using the numerical Fourier transform is related to the aforementioned Rayleigh method. the scattering undergoes frequency-selective damping and where damping occurs The steps for obtaining the strain value by measuring the change in frequencies are 20. This relates to the distributed strain measurement method with frequency-selective damping. (Figure 1 shows this). The invention concerns a fiber optic-based distributed system, which is the apparatus used to apply the measurement method. An example block diagram of a strain sensor (SSS) device (100) is given. With the help of the device, light is sent in the form of pulses on a fiber line (10); this light, The energy is scattered in the fiber line (10) and returns to the place where it was sent. The strain subject of the invention is 25 In the measurement method, the frequency distribution of the light obtained from the aforementioned fiber line (10) It is being examined. The invention specifically concerns the apparatus in which the strain measurement method is applied; It is used to measure quantities such as strain, temperature, and vibration, via fiber optic cable. (10) Which scattering method was used to obtain the light obtained is the most basic method of such applications. It determines the difference. 30 7 The DGS device (100), an example block diagram of which is given in Figure-1, is narrow for the production of optical signals. a band light source (1), high which amplifies the power of the light coming from this light source (1) powerful optical amplifier (2) to shape the optical signal sent through the fiber, its frequency an optical modulator (3) for shifting and converting into a pulse series, converting into a pulse series Optical entanglement (4) which injects a given optical signal into the fiber, measures the detected light. 5 high gain optical amplifier (5) which increases the power of light, produced by the optical amplifier an optical band that prevents the spontaneous emission from being transmitted forward in the optical system permeable filter (6), a photodetector unit (7), processing the detected optical distributed sensor data It includes a data collection card (8) for the DGS device (100) which is the subject of the invention, optical signal, The modulation signal (9) sent to the optical modulator (3) is shaped and its frequency is 10 It is being changed. Scattering centers, which enable measurements using the Rayleigh scattering mechanism, are C- Production of a fiber line (10) that provides single-mode light transmission in the band (1.550 nm). This occurs during the process. These scattering centers are considered a manufacturing defect in the fiber line (10). These are the differences in optical index and material defects that exist. 15 from the scattering centers The scattered and remaining parts of the light in the fiber's numerical aperture are collected with the same fiber and DGS It returns via the same optical fiber line (10) to be processed in the device (100). DGS In the device (100), the modulation signal (9) which drives the optical modulator (3) is a double pulse It is formed, and there is a delay time and frequency difference (Δf) between the pulses. The double pulse is injected sequentially into the fiber line (10) via the optical converger (4). 20 Successive pulses in the optical signal scatter through successive regions of the fiber via Rayleigh scattering. It is reflected. The optical signal reflected from different parts of the reflection zones is the same. The reflections reach the photosensitive unit (7) in time; the said reflections are fiber line (10) They have different phases because of the different paths they take. Therefore, the signal It has been observed that some of its components are strengthening while others are weakening. These 25 components have been observed. Strengthening and weakening; the bandwidth of the optical signal is greater than the bandwidth of its components. Because it is wide, it is frequency selective. This means the signal has different frequencies. This causes its components to have different sizes. Sizes The difference between them can also be observed in the spectrum of the signal. Strain in the fiber line (10) When the signal changes, the length of the optical path followed by each signal also changes, and the signal's 30 The traces in its spectrum also change. Strain information can be obtained by tracking these traces. This can be done. For this purpose, the optical signal detected in the photodetector unit (7) in this invention After the spectrum is generated using the numerical Fourier transform, the observed frequency in the spectrum, is converted into strain. Strain, as modeled in strain-optical theory, is refractive index. This causes a change in the index. 35 8 This change; “Δn=-0.5n3{P12-ζ(P11 + P12)}ε “ This is according to the formula. In this formula; Δn: change in refractive index, 5 P11 and P12: Pockel coefficients; ζ is the Poisson coefficient. ε represents the strain amount. These values, P11, P12, and ζ, are for glass fiber, respectively. It has values of 0.113, 0.252, and 0.16 for glass (SiO2) fiber at a wavelength of 1,550 nm. “Δn=-0.22nε”. In addition to the change in the refractive index, the strain causes the elongation of the fiber to increase by 10. This also leads to the path that light takes within the fiber after strain is applied. The change can be expressed as “Δx=x(1+ε)(n+Δn)”. This formula is “Δx=xn(1+αε+γε2)” When rephrased as such, α and γ are represented at a wavelength of 1,550 nm in a glass medium. The coefficients are 0.79 and 0.21 respectively. Due to these two effects, light, photo It arrives at the sensor unit (7) after a time of (Δx / c). Here “c” represents the speed of light. This phase difference, caused by the time difference, causes the perceived signal to attenuate. This causes a shift in their frequencies. When the phase of the light is followed, the perceived light, Due to strain, it will have the phase xn(1+αε+γε2)2πν / c instead of xn2πν / c. This In the formulas, ν represents the frequency of light. The difference between the two phases is xnαε2πν / c This is the case. In this calculation, the effect of second-order strain is quantitatively equivalent to that of first-order strain. It is neglected because it is much less than the effect of strain. In summary, photo The traces of the spectrum measured in the sensor unit (7) are shifted by an amount of αεν. For example; 1.550 The spectral traces of light with a wavelength of nm are shifted by a ratio of “κ = αν = 151” MHz / με. After measuring the frequency shift, the strain is obtained by dividing the frequency by the quantity κ. Information is obtained. Thanks to this invention, light sources and standard telecommunication fibers 25 This enables measurements to be made with nano-strain sensitivity. The scattering in the optical fiber can occur anywhere in the fiber line (10) fiber optic It enables the distributed use of sensors and each one in the optical fiber This means that the point can be evaluated as a sensor. Fiber line (10) The low power loss in signal transmission (approximately 0.2 dB / km) is measured over a long fiber optic line. This enables measurements to be made using the method described in the invention. Strain information can be obtained along the fiber line (10). 9 Figure 2 shows the steps for obtaining strain information in the DGS device (100) which is the subject of the invention. An example flowchart is given. The subject of the invention is frequency selective damping. The distributed strain measurement method basically involves the following steps: - In the DGS device, light synthesized from (1) light source (100) is high-power optical After being amplified by the amplifier (2), the frequencies are changed with the optical modulator (3) to 5 An optical signal is generated by converting the pulses into a series of consecutive pulse pairs. - Frequency difference (Δf) and delay time between pulse pairs are determined by the optical modulator (3) is determined by the transmitted modulation signal (9). - The aforementioned optical signal is transmitted to the fiber used as a sensor with the help of an optical router (4). injected into line (10). 10 - The optical signal scattered from the fiber line (10) is collected by the optical encoder (4) and optical power is amplified by high gain optical amplifier (5) and optical bandpass filter (6) It is filtered and measured with a photodetector unit (7). - Scatter data is recorded with the data collection card (8). - The spectrum of the detected scattering data (optical signal) is obtained using the numerical Fourier transform. 15 - The resulting spectrum is divided by the κ value, and then the values obtained from successive measurements are calculated. The results show that the regions in the spectrum undergoing frequency-selective fading shift. The amount of change and the direction of slip are measured, and - From these measurement results, the strain is calculated in units of με. In Figure-3, the 20 taken from a region of the fiber line (10) with the DGS device (100) which is the subject of the invention. The change of the scattering data spectrum over time in the absence of strain. There are only negligible changes in the spectrum over time. It is observed. However, in Figure-4, the DGS device (100) is the subject of the invention and the fiber The scattering data spectrum taken from a region of the line (10) at a frequency of 0.1 Hz and 0.2 με This shows the change over time when strain is applied at a certain amplitude. 25 Due to the applied strain, a change in the spectrum over time is observed. In Figure 5, the subject of the invention, the DGS device (100), is taken from a region of the fiber line (10). Strain information obtained from the scattering data spectrum by dividing the spectrum by the quantity κ When a strain of 0.03 με is applied at a frequency of 200 Hz, the change over time... The change is shown. When the amplitude of the sine wave observed in Figure 5 is examined, it is 30 The given strain is summarized in Figure 2 and the invention described in detail above. this can be accurately obtained using the distributed strain measurement method described within the scope. This conclusion is reached. When the sine wave observed in Figure 5 is examined, the strain is... The resulting altered spectrum is clearly distinguishable from the spectrum shown in Figure 3; When compared with Figure 4, it is also evident that high-frequency strain variations are significant. It has been observed that the strain can be distinguished in this way. The invention relates to the determination of strain variation with two consecutive measurements. This invention enables the calculation of covariance to be reduced by 5%. By preventing this, strain changes at the Nyquist frequency are obtained, and nano-strains are achieved. a method that enables measurement with high precision to the relevant technical field is being provided.
Claims
11 REQUESTS 1. Dual pulse phase optical in fiber optic based distributed strain sensor (DGS) device (100) using time domain reflectometer (OZAR) on a long optical fiber line (10) Performing nano-strain-sensitive measurements using frequency-selective damping. It is a distributed strain measurement method that provides; 5 - generation of optical signals, - the frequency difference (Δf) and delay time between the pulse pair, to the optical modulator (3) determined by the transmitted modulation signal (9), - the aforementioned optical signal is used as a sensor with the help of an optical circulator (4) sequentially injecting into the fiber line (10), 10 - the paths taken by successive pulses in the optical signal within the fiber line (10) are different, Reflection by Rayleigh scattering, - Measurement of the aforementioned Rayleigh scatterings with the photodetector unit (7), - processing and recording of the measured scattering data via the data collection card (8), - reducing the frequency of the aforementioned Rayleigh scattering to radio frequency, 15 - optical signal detected in the photodetector unit (7) by numerical Fourier transform obtaining the spectrum, - Change in refractive index (Δn) after voltage is applied and the light path on the fiber optic cable (10) Change in the path it follows (Δx) effect of light to the photodetector unit (7) (Δx / c) arriving late by the specified time, 20 - due to the phase difference caused by this time difference, in the photodetector unit (7) shift in extinction frequencies in the measured optical signal spectrum, - the aforementioned Rayleigh scattering undergoes frequency-selective damping and the amount of slip and the direction of slip at the frequencies where damping occurs measuring the change, and 25 - Obtaining the strain value in units of με from these measurement results. It is characterized by including the steps involved in the process.
2. It is a distributed strain measurement method as in Claim 1, and its feature is the aforementioned DGS (100) In the device, light is sent in the form of (10) pulses on the fiber line, and this light is sent on the fiber line (10) It is the process of being scattered and returning to the place from which it was sent. 30 3. A distributed strain measurement method as in Claim 1, characterized by its use of the aforementioned optical... the signal; light synthesized from a supplied light source (1), high-power optical After being amplified by the amplifier (2), the optical modulator (3) produces sequential signals with different frequencies. It is created by converting it into a pair of pulses. 12 4. A distributed strain measurement method as in Claim 1, characterized by its use of the aforementioned optical... the signal is shaped by the modulation signal (9) sent to the optical modulator (3) It is the change of frequency.
5. A distributed strain measurement method as in Claim 1, characterized by the aforementioned Rayleigh method. their scattering is collected by optical entanglement (4) and optical power is high gain optical 5 amplified by amplifier (5) and filtered by optical band-pass filter (6) photodetector It is measured through the unit (7).
6. A distributed strain measurement method as in Claim 1 or 5, characterized by the aforementioned optical... spontaneous output produced by the optical amplifier through the band-pass filter (6) It prevents the emission from being transmitted forward in the optical system. 10 7. A distributed strain measurement method as in Claim 1, characterized by the aforementioned refractive index. Calculation of the change in index (Δn) according to the formula Δn=-0.5n3{P12-ζ(P11 + P12)}ε where “Δn” represents the change in the refractive index, “P11 and P12” are the Pockel coefficients, and “ζ” is the Poisson coefficient. where "ε" represents the coefficient and "ε" represents the strain amount.
8. A distributed strain measurement method as in Claim 1, characterized by the fact that the strain is measured 15 minutes after application. then the path that the light takes in the fiber line (10) changes by “xn(1+αε+γε2)” (Δx).
9. A distributed strain measurement method such as in Claim 1 or 8, and its feature is; fiber line (10) The change in the path (Δx) of the light in the photodetector unit (7) is Δx / c (c: speed of light) It means arriving late by the specified amount of time.
10. A distributed strain measurement method as in Claim 1, whose characteristic is that “ε” is the strain amount, 20 “ν” is the frequency of the light and “α” is a coefficient depending on the material properties of the fiber line (10). This shows that the frequency shift in the optical signal spectrum is approximately "αεν". It is the fact that.
11. A distributed strain measurement method as in Claim 1, characterized by the following: the aforementioned strain its value; by comparing the results obtained from measurements in terms of the change in the spectrum 25 It is obtained by calculating in units of "με".