Distributed optical fiber sensing and transmission method and system based on optical grouping

Abstract

A distributed optical fiber sensing and transmission method and system based on optical grouping integrates signal frame and signal element concepts in the communication field to the sensing field, each measurement signal frame comprises a plurality of measurement signal elements, all-optical fiber scanning is achieved, each measurement signal element comprises a pair of time-coded pump light pulses and rectangular square wave detection light, and all-optical fiber scanning is achieved. The probe light and the pump light are injected into the optical fiber in the same direction, the probe light is reflected at the tail end of the optical fiber and then encounters oppositely with the pump light to generate scattering signals, and encounter points can be measured by analyzing the signals. Because the time intervals of the pulse square waves in each measurement signal element are different, the formed measurement signal frame can cover all measurement points on the optical fiber, thereby achieving the target of all-optical-fiber distributed measurement. According to the method, the pump light evacuation effect and the non-local effect are avoided, all points can be measured at a time on the premise that the resolution (the spatial resolution and the measurement precision) is guaranteed, and the resolution and the time efficiency are both considered.

Description

Technical Field

[0001] The present invention relates to distributed optical fiber sensing, and in particular to a distributed optical fiber sensing and transmission method and system based on optical grouping. Background Art

[0002] Sensing technology is widely used in the measurement of various physical quantities, such as strain, temperature, pressure, etc. Among them, optical fiber sensing technology is becoming increasingly important in intelligent monitoring systems due to its advantages such as high sensitivity and strong anti-electromagnetic interference ability. Optical fiber sensing technology is mainly divided into two categories: point sensing and distributed sensing, each with different application advantages.

[0003] Point sensing technology, such as fiber Bragg grating sensing, has the advantages of high precision and high sensitivity, but its measurement points are discrete, making it difficult to achieve continuous spatial distribution measurement. In addition, when large-scale deployment is required, the complexity and cost of point sensing systems will increase significantly.

[0004] In contrast, distributed fiber optic sensing technology uses the entire optical fiber as a sensing element to achieve continuous spatial distribution measurement of the measured parameter within the length of the optical fiber. However, the current distributed fiber optic sensing technology still faces the contradiction between resolution and time efficiency. Specifically, in order to improve the spatial resolution, it is usually necessary to compress the pulse width, but this will cause the system signal-to-noise ratio to decrease, which in turn leads to a decrease in measurement accuracy. In order to maintain sufficient measurement accuracy, the number of repeated measurements has to be increased, which inevitably sacrifices the system's time efficiency.

[0005] The academic community has also conducted in-depth research on this issue. For example, in 2016, Bergman et al. published an article titled "High spatial resolution, low-noise Brillouin dynamic gratings reflectometry based on digital pulse compression" in "Optics Letters" and in 2017, Wang et al. published an article titled "Enhancing the performance of BOTDR based on the combination of FFT technique and complementary coding" in "Optics Express". They both mentioned that although shortening the pulse width can effectively improve the spatial resolution, this will significantly reduce the signal-to-noise ratio, and thus increase the number of repeated measurements to obtain acceptable measurement accuracy, which greatly reduces the time efficiency of the system. In response to this problem, patent CN101852627A (Coding technology and its use for improving the detection performance of distributed optical fiber sensors) uses coding technology to improve the signal-to-noise ratio, thereby reducing the number of repeated measurements and shortening the measurement time. However, when the coding order is too high, the effect of this method in shortening the system measurement time is also limited, and further technological innovation is still needed to break through the current limitations. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a distributed optical fiber sensing and transmission method based on optical grouping, which uses the idea of ​​improving network bandwidth utilization through signal frames and signal elements in the communication field, and introduces the concepts of measurement signal frames and measurement signal elements in the sensing field to improve sensing efficiency. Among them, each measurement signal frame is constructed as a composite unit containing several measurement signal elements, and these signal elements work together to realize all-fiber distributed scanning measurement. Each measurement signal element is a pair of pulse square wave combinations, including a pump light pulse encoded at a specific time and a detection light in the form of a rectangular square wave. At each measurement point, when the pump light and the detection light meet at a certain position of the optical fiber, stimulated Brillouin scattering effect can be induced. By analyzing the scattered signal, the sensing information of the point can be obtained to realize single-point measurement. Since the pulse square wave time intervals in each measurement signal element are different, the constructed measurement signal frame can cover all measurement points on the optical fiber, thereby realizing all-fiber distributed high-precision measurement.

[0007] The technical solutions adopted by the present invention are as follows:

[0008] A distributed optical fiber sensing and transmission method based on optical grouping is characterized in that a measurement signal frame is used to realize scanning measurement of the entire optical fiber, wherein each measurement signal frame contains a plurality of measurement signal elements, each measurement signal element is used to sense a specific measurement point in the optical fiber; the measurement signal element includes a pump light and a detection light, and there is a specific time delay relationship between the pump light and the detection light, which is used to generate a nonlinear scattering effect at a predetermined measurement point in the optical fiber.

[0009] Measuring principle:

[0010] 1) Optical signal injection: High-power pump light and rectangular square wave detection light are injected into the optical fiber in the same direction but not at the same time. The detection light is reflected by the fiber Bragg grating at the end of the optical fiber and becomes the reverse detection light.

[0011] 2) SBS generation: When the reverse probe light and the forward pump pulse light meet in the optical fiber and meet the phase matching condition, a reverse Brillouin scattering pulse is generated.

[0012] 3) Signal detection: The generated Brillouin scattering signal is captured and processed by the detection system, thereby achieving measurement of specific locations along the optical fiber.

[0013] On the one hand, the present invention provides a distributed optical fiber sensing and transmission method based on optical grouping, which is characterized in that a measurement signal frame is used to realize scanning measurement of the entire optical fiber, wherein each measurement signal frame contains a plurality of measurement signal elements, and each measurement signal element is used to sense a specific measurement point in the optical fiber; the measurement signal element includes a pump light and a detection light, and there is a specific time delay relationship between the pump light and the detection light, which is used to generate a nonlinear scattering effect at a predetermined measurement point in the optical fiber.

[0014] Furthermore, the pump light is a high-power, narrow-pulse-width pulse, and the detection light is a rectangular square wave signal.

[0015] Furthermore, the pump light and the probe light are injected into the optical fiber in the same direction but not at the same time. The probe light is reflected by the fiber Bragg grating at the end of the optical fiber to become reverse probe light, propagates in the opposite direction of the pump light, and meets a predetermined measurement point in the optical fiber to generate nonlinear scattering, including Brillouin scattering or Raman scattering.

[0016] Furthermore, the time delay intervals of the pump light pulse and the detection light signal in each measurement signal element are different, so that the constructed measurement signal frame can cover all measurement points on the optical fiber, realizing all-fiber distributed measurement.

[0017] Furthermore, the relationship between the duration T0 of the measurement signal frame and the duration τ0 of the measurement signal element is determined by the following formula:

[0018] T0=m*τ0;

[0019] Where m is the number of measurement points in the optical fiber.

[0020] Furthermore, the number of measurement points m in the optical fiber satisfies the following relationship with the total length L0 of the optical fiber and the spatial resolution l0:

[0021]

[0022] Furthermore, the duration τ0 of the measurement signal element is related to the total length L0 of the optical fiber and the group velocity v g The following relationship is satisfied:

[0023]

[0024] Furthermore, the time delay τ between the pump light and the probe light is i With the measured point P i The distance L i The following relations are satisfied:

[0025]

[0026] Among them, L i From the fiber entrance to the measured point P i distance.

[0027] Furthermore, the distributed optical fiber sensing and transmission method based on optical packetization comprises the following steps:

[0028] Generate stable, high-quality continuous light and divide it into pump light path and detection light path;

[0029] Modulating the pump light and the detection light to generate a measurement signal element including a high-power pump pulse and a rectangular square wave detection light;

[0030] Control the time delay between pump light and probe light;

[0031] Power amplification and polarization optimization of pump and probe light;

[0032] Combine the pump light and the detection light and inject them into the single-mode single-core optical fiber;

[0033] At the fiber Bragg grating at the end of the optical fiber, the probe light is reflected and propagates in the opposite direction to the pump light, and they meet at a predetermined position in the optical fiber and undergo stimulated Brillouin scattering effect;

[0034] The signal acquisition and processing module is used to acquire and process the reverse propagating Brillouin scattering signal to obtain the sensing quantity of the measuring point in the optical fiber.

[0035] On the other hand, the present invention also provides a distributed optical fiber sensing and transmission system based on optical grouping, which is characterized by comprising:

[0036] Laser and optical signal generation module, used to generate stable, high-quality continuous light and divide it into pump light path and detection light path;

[0037] An optical signal modulation and control module, which is used to modulate the pump light and the detection light to generate a measurement signal element including a high-power pump pulse and a rectangular square wave detection light; it includes a ns pulse generator and a coding module for pulse modulation of the pump light, and a 10 GHz microwave source and a coding module for modulating the detection light;

[0038] A central control module, used to control the time delay between the pump light and the probe light so as to achieve the encounter at a predetermined position in the optical fiber and generate a stimulated Brillouin scattering effect;

[0039] An optical signal amplification and optimization control module, including an erbium-doped fiber amplifier and a polarization controller, is used to amplify the power and optimize the polarization of the pump light and the detection light;

[0040] Optical signal combining and injection fiber module, including 2*1 coupler and circulator, used to combine pump light and detection light and inject them into single-mode single-core fiber;

[0041] The fiber sensing and stimulated Brillouin scattering module includes a fiber Bragg grating at the end of the optical fiber, which is used to reflect the probe light and make it propagate in the opposite direction of the pump light;

[0042] The signal acquisition and processing module includes an optoelectronic processing module and a data server, which is used to acquire and process the reverse-propagating Brillouin scattering signal to obtain the sensing quantity of the measuring point in the optical fiber;

[0043] The measurement signal elements are arranged sequentially in the time domain to form a measurement signal frame covering the entire length of the optical fiber. By adjusting the time delay between the pump light and the detection light, their encounter at a certain position in the optical fiber can be controlled.

[0044] Compared with the prior art, the present invention has the following advantages:

[0045] 1) By adjusting the pulse width and amplitude, the spatial resolution and signal-to-noise ratio are optimized, and under the premise of ensuring the resolution, the measurement of all measuring points of the optical fiber is completed at one time, taking into account both the resolution and the time efficiency; the present invention significantly improves the measurement time efficiency while taking into account the high resolution, and provides strong support for fast and accurate distributed optical fiber perception.

[0046] 2) In traditional fiber optic sensing technology, pump light depletion effect and non-local effect often have an adverse effect on the measurement results. The present invention successfully avoids these effects by optimizing pulse parameters and signal encoding methods, thereby ensuring the accuracy and reliability of the measurement results.

[0047] 3) Through the single-ended injection method, the arrangement of the light source at the other end of the optical fiber is avoided, the hardware cost is reduced, and in practical applications, since the other end of the optical fiber can be freely arranged, the system can be used in scenarios with complex environments or inaccessible optical fiber ends (such as submarine optical cable monitoring, earthquake monitoring, etc.).

[0048] 4) The present invention allows users to accurately control the spatial resolution and measurement accuracy of the measurement points by flexibly adjusting pulse parameters (such as pulse width, time interval, etc.) according to actual needs. This feature enables the present invention to achieve high-resolution and high-precision measurement tasks in different application scenarios. At the same time, completing the measurement tasks of all points on the optical fiber at one time also further improves the measurement efficiency and meets the diverse and complex measurement needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of a measurement signal frame provided by an embodiment of the present invention.

[0050] Figure 2 A schematic diagram of a measurement signal element provided in an embodiment of the present invention.

[0051] Figure 3 A schematic diagram of the application of a distributed optical fiber sensing and transmission method based on optical grouping provided in an embodiment of the present invention.

[0052] Figure 4 is the i-th measured signal element τ i Schematic diagram of the measurement timing.

[0053] 1: Measurement signal frame

[0054] 2: Measurement signal element

[0055] 3: High power pump pulse

[0056] 4: Rectangular square wave detection light

[0057] 5: Single-mode single-core optical fiber

[0058] 6: 1*2 coupler

[0059] 7: Modulator

[0060] 8: Erbium-doped Optical Fiber Amplifier (EDFA)

[0061] 9: Polarization controller (PC)

[0062] 10: 2*1 coupler

[0063] 11: Circulator

[0064] 12: Fiber Bragg Grating

[0065] 13: Narrow linewidth wavelength tunable laser

[0066] 14: ns pulse generator and encoding module

[0067] 15: 10GHz microwave source and encoding module

[0068] 16: Optical power balance control module

[0069] 17: Polarization adjustment and optimization control module

[0070] 18: Photoelectric processing module

[0071] 19: Central control module

[0072] 20: Data Server DETAILED DESCRIPTION

[0073] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0074] Please read first Figure 1 , Figure 1 This is a schematic diagram of a measurement signal frame of an embodiment of the present invention. As shown in the figure, the structure of the measurement signal frame 1, a complete measurement signal frame 1 covers the measurement process of the entire length of the optical fiber, and the duration is T0. Within a measurement signal frame 1, there are several measurement signal elements 2, these measurement signal elements 2 are arranged in sequence in the time domain, and there are different time intervals between the internal pulse square waves. Through this time division multiplexing method, the scanning measurement of the fully distributed optical fiber can be effectively realized.

[0075] Figure 2 Schematic diagram of the measurement signal element of the embodiment of the present invention. A measurement signal element 2 contains a high-power pump light 3 and a rectangular square wave detection light 4. The pump light and the detection light are modulated by a specific time code, injected into the optical fiber with different delay times, and meet at a certain position of the optical fiber. These delay times are defined as τ i , is the relative time position of the pump light and the probe light in each measurement signal element 2 in the measurement signal frame 1, by adjusting the delay time τ i, their meeting at a certain position in the optical fiber can be precisely controlled. The pump light and the probe light in the measurement signal element 2 can be ensured to meet at the desired position through this time encoding method, so that the stimulated Brillouin scattering effect occurs at the meeting point, and the energy is transferred from the pump light to the probe light, generating Brillouin scattered light. By collecting and analyzing the scattered light, the measurement of the desired position can be completed.

[0076] In order to more clearly express the measurement process in the optical fiber, it is assumed that the duration of a measurement signal frame is T0, which is composed of m measurement signal elements τ0, that is:

[0077] T0=m*τ0

[0078] Among them, m is the number of measuring points in the optical fiber, which is related to the total length L0 of the optical fiber and the spatial resolution l0, that is:

[0079]

[0080] τ0 is the measurement signal element, which is related to the total length of the optical fiber L0 and the group velocity v of the light. g Relevant, namely:

[0081]

[0082] Where, the group velocity v g 2×10 8 m / s.

[0083] Here are two calculation examples: 1. In the case of long-distance demodulation, assuming that the total length of the optical fiber L0 is 12 kilometers and the spatial resolution l0 is set to 0.01m, then the number of measurement points m is 1.2×10 5 , the length of the measured signal element τ0 is 120μs, and the length of the measured signal frame T0 is 14.4s; 2. In the case of short-distance demodulation, assuming that the length of the optical fiber L0 used for shape sensing on the intelligent robot arm is 20m, and the spatial resolution l0 is set to 0.002m, then the number of measurement points m is 1×10 4 , the length of the measurement signal element τ0 is 200ns, and the length of the measurement signal frame T0 is 2ms.

[0084] Furthermore, with the i-th measurement element τ i Complete the P i The measurement at point τ0 is explained as follows: the measurement signal element τ0 composed of the high-power pump pulse and the rectangular square wave probe light occupies one measurement signal element in the time domain, such as 120μs in the previous example. The two signals occupy two different frequencies in the frequency domain, and the pump light frequency is assumed to be f0 or represented by λ0. The probe light frequency is lower than the pump light frequency by one fiber Brillouin scattering Stokes frequency v B , which can be expressed as f s=f0-v B From the time domain, the phase difference between the pump light and the probe light is τ i , the τ i The range is [0,τ0], and the specific size is related to the position of the measurement point. It is the detection light signal from the measured point forward to the end of the optical fiber, and then through the end FBG (the center frequency of FBG is the same as f s consistent) reflection, back to the measured point P i The time required. Assuming that the time from fiber entry to the measured point P i The distance is L i , then τ i It can be expressed as:

[0085]

[0086] Specifically, the sequence of events from the detection light of the measurement signal element entering the fiber to the measured point, the pump light and the detection light generating the Brillouin scattering signal, and then returning to the fiber entrance can be briefly described as follows:

[0087] a) The detection light reaches the fiber entrance;

[0088] b) The probe light travels τ in the optical fiber i , the pump light reaches the fiber entrance and moves in the same direction;

[0089] c) The detection light and the pump light travel in the same direction toward the measured point in the optical fiber;

[0090] d) The probe light and the pump light travel in the same direction until the probe light reaches the measured point P i ;

[0091] e) The probe light and the pump light continue to move forward until the probe light reaches the FBG at the end of the optical fiber and is reflected, completing the transmission process of the probe light traveling a complete length of the optical fiber, and the time is τ0 / 2;

[0092] f) The probe light is reflected by the FBG and travels in the opposite direction to the pump light;

[0093] g) The probe light meets the pump light at the measured point P i , and assuming that the power of the pump light is greater than the Brillouin threshold in the optical fiber, the generated Brillouin scattering gain energy is transferred to the detection light, forming a signal light carrying Brillouin scattering information;

[0094] h) The signal light carrying the Brillouin scattering information continues to travel in the reverse direction, and the pump light continues to move forward until it passes through

[0095] FBG, and leaves the sensing fiber;

[0096] i) The signal light carrying the Brillouin scattering information reaches the fiber entrance, completing a complete measurement process of the signal element.

[0097] In summary:

[0098] In order to more effectively describe and implement the measurement of optical fiber, the present invention introduces the concepts of "measurement signal frame" and "measurement signal element". A measurement signal frame represents the scanning process of all points in the entire length of the optical fiber, while a measurement signal element represents a sensing unit for measuring a single point, which internally defines the delay time of the pump light and the detection light for a certain measurement point of the optical fiber. By reasonably adjusting the duration of the measurement signal frame and the pulse square wave time interval within each measurement signal element, each measurement point in the optical fiber can be accurately scanned.

[0099] In each measurement signal element, the pump light and the probe light are injected into the optical fiber through a specific pulse coding method. There is a certain time delay between the pump light and the probe light. The pulse coding can accurately control the meeting point of the two in the optical fiber, and then energy transfer occurs. This energy transfer is based on stimulated Brillouin scattering. By detecting the frequency shift change of the signal after energy transfer, the change of the external signal can be accurately sensed.

[0100] On the basis of single-point measurement, the present invention realizes the perception of multiple positions of the optical fiber by successively changing the time delay between the pump light and the detection light. The pulse square wave pair in each measurement signal element transfers energy at different positions of the optical fiber, and finally the full optical fiber scanning can be realized through the measurement signal frame composed of continuous measurement signal elements.

[0101] Finally, the present invention allows further optimization of measurement performance by adjusting the width and amplitude of the pulse. The adjustment of the pulse width directly affects the spatial resolution, while the pulse amplitude affects the signal strength and signal-to-noise ratio. According to the requirements of different application scenarios, the present invention can achieve higher spatial resolution or maintain higher measurement accuracy over a longer measurement range through flexible pulse adjustment.

[0102] Figure 3 This is a schematic diagram of an application of a distributed optical fiber sensing and transmission method based on optical packetization according to an embodiment of the present invention. Figure 3 It can be seen that each module is connected through a single-mode single-core optical fiber 5. The narrow linewidth wavelength tunable laser 13 generates high-quality continuous light that enters the 1*2 coupler 6 and is divided into two optical paths, one of which is the pump light, which is modulated by the modulator 7 controlled by the ns pulse generator and the encoding module 14, and the other is the detection light, which is modulated by the modulator 7 controlled by the 10GHz microwave source and the encoding module 15. The time delay τ between the pump light and the detection light iThe size is controlled by the central control module 19. The two optical paths are then amplified and polarized by the erbium-doped fiber amplifier 8 controlled by the optical power balance control module 16 and the polarization controller 9 controlled by the polarization adjustment and optimization control module 17. Finally, they are converged into one optical path through the 2*1 coupler 10, and injected into the single-mode single-core optical fiber 5 with a fiber Bragg grating 12 engraved at the end through the circulator 11 for measurement. The generated reverse propagating signal light is collected and processed by the optoelectronic processing module 18, and then enters the data server 20 through the central control module 19 for calculation and processing to obtain the size of the sensor. Traverse all τ i , the complete scanning of the entire optical fiber can be achieved.

[0103] Below is Figure 3 More detailed explanation:

[0104] 1. Laser and optical signal generation module:

[0105] 1) Narrow linewidth wavelength tunable laser 13: This is the core light source of the system, responsible for providing stable, high-quality continuous light. Due to the narrow linewidth characteristics of the laser, it can generate a relatively pure single-wavelength optical signal, avoiding the noise interference caused by the wide-spectrum light source. At the same time, after sideband modulation, it can generate detection light with relatively accurate frequency deviation, which is crucial for subsequent Brillouin scattering measurements. This light source is Figure 1 The measurement signal frame 1 shown provides a basic light signal.

[0106] 2) 1*2 coupler 6: Splits the continuous light output by the laser into two paths, one for generating pump light and the other for generating detection light. This split allows the system to generate two optical signals with different functions at the same time. The two optical signals will be further modulated into Figure 2 The structure of the measurement signal element 2 is shown.

[0107] 2. Optical signal modulation and control module

[0108] 1) ns pulse generator and encoding module 14: The pump light is pulse modulated by the modulator 7, and its pulse width is controlled by the ns pulse generator and encoding module 14 to generate a pump pulse 3 with a higher peak power, so as to produce a more obvious energy transfer phenomenon in the subsequent interaction process. The modulated pump light will be further optimized by the erbium-doped fiber amplifier 8 and the polarization controller 9. This module is responsible for generating Figure 2 The high-power pump pulse 3 shown in FIG. 1 is a key part of the measurement signal element 2 .

[0109] 2) 10 GHz microwave source and encoding module 15: The detection light path is modulated by the 10 GHz microwave source and encoding module 15 to form a rectangular square wave signal with a sideband of about 10 GHz, i.e., the detection light signal. The modulation of the detection light is also controlled by the encoding module to ensure that its time delay relationship with the pump light is accurately controlled during the measurement. This module is responsible for generating Figure 2 The rectangular square wave detection light 4 shown in the figure, together with the high-power pump pulse 3, constitutes a complete measurement signal element 2.

[0110] 3) Central control module 19: This module is responsible for controlling the time delay between the pump light and the detection light. By adjusting the time interval between the two optical signals, the measurement of different points of the optical fiber can be achieved. This dynamic delay control ensures Figure 1 The measurement signal frame 1 structure shown can be realized so that the system can complete a comprehensive scan of the entire optical fiber within one cycle T0.

[0111] 3. Optical signal amplification and optimization control

[0112] 1) Erbium-doped fiber amplifier 8: used to amplify the power of pump light and probe light to compensate for signal attenuation generated during long-distance fiber transmission.

[0113] The optical power balance control module 16 adjusts the gain of the amplifier in real time to ensure that the power of the pump light and the detection light in each measurement signal element 2 is kept within a suitable range, thereby avoiding measurement errors caused by power imbalance.

[0114] 2) Polarization controller 9: used to adjust the polarization state of the optical signal. Since the scattering process in the optical fiber is easily affected by the polarization state of the optical signal, the polarization adjustment and optimization control module 17 can more accurately control the polarization state of the two signals in each measurement signal element 2 through the polarization controller 9 to maximize the signal quality.

[0115] 4. Optical signal combining and injection into optical fiber

[0116] 1) 2*1 coupler 10: The amplified and polarization-optimized pump light and detection light are re-converged into one optical signal to form a complete measurement signal element 2.

[0117] 2) Circulator 11: This device is a three-port passive optical device, which is responsible for injecting the combined measurement signal element 2 into the single-mode single-core optical fiber 5, and can transmit the reverse propagating signal light to the optoelectronic processing module 18 for subsequent processing.

[0118] 5. Fiber Optic Sensing and Stimulated Brillouin Scattering

[0119] 1) Fiber Bragg grating 12: A fiber Bragg grating 12 is engraved at the end of the optical fiber. Its function is to reflect only the detection light and allow other signals to pass through, so that the detection light and the pump light can propagate in opposite directions and finally meet at a certain position of the optical fiber to produce stimulated Brillouin scattering effect. In this way, it is ensured that the pump light and the detection light in each measurement signal element 2 can interact at the expected position to produce a scattered signal.

[0120] 2) Stimulated Brillouin scattering effect: Stimulated Brillouin scattering effect is the detection mechanism of this system. It relies on the change of optical properties caused by local strain or temperature change in the optical fiber, which affects the frequency shift of the scattered light. By accurately measuring the frequency shift of the scattered light, the strain or temperature change at the location where stimulated Brillouin scattering occurs in the optical fiber can be obtained.

[0121] 6. Signal acquisition and processing

[0122] 1) Optoelectronic processing module 18: The reverse propagating Brillouin scattering signal enters the optoelectronic processing module 18 through the circulator 11. This module converts the optical signal into an electrical signal and performs a series of processing such as filtering, amplification, and demodulation. It can process the signal of each measurement signal element 2 in turn according to the structure of the measurement signal frame 1.

[0123] 2) Data server 20: The processed signal is transmitted to the data server 20 through the central control module 19. The server processes the signal through a pre-set algorithm to obtain the sensing quantity such as strain or temperature of the measurement point, and then corresponds each measurement signal element 2 in the measurement signal frame 1 to the specific position on the optical fiber, so as to realize the distributed parameter perception of the full optical fiber.

[0124] 7. Interconnection and collaboration of system modules

[0125] Collaboration between the central control module 19 and various functional modules: The central control module 19 not only controls the core processes such as encoding, pulse delay, and signal acquisition and processing, but also interacts with the narrow linewidth wavelength tunable laser 13, ns pulse generator and encoding module 14, 10GHz microwave source and encoding module 15, optical power balance control module 16, polarization adjustment and optimization control module 17, and optoelectronic processing module 18 for digital signals. Its core role is to coordinate the work of various modules, ensure that the structure of the measurement signal frame 1 and the measurement signal element 2 is accurately implemented, and make the operation of the entire system reach the optimal state.

[0126] In summary, the distributed optical fiber sensing and transmission method based on optical grouping proposed in the present invention avoids the pumping light hollowing effect and non-local effect, and improves the measurement accuracy; the spatial resolution and measurement accuracy of the measuring point can be flexibly controlled by adjusting the pulse parameters, and the measurement of all points on the optical fiber can be completed at one time under the premise of ensuring the resolution, taking into account both the resolution and time efficiency; the single-ended injection method is adopted, which not only reduces the hardware cost of arranging the light source at the other end of the optical fiber, but also makes the system more adaptable, especially in scenes where the optical fiber end is difficult to approach or the environment is complex; in addition, the present invention is not only applicable to the single-core optical fiber mentioned in the text, but also to multi-core optical fibers, providing a basis for vector sensing.

[0127] The above is a description of the specific embodiments of the present invention. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which will not affect the essence of the present invention.

Claims

1. A distributed optical fiber sensing and transmission method based on optical packetization, characterized in that: A measurement signal frame is used to implement scanning measurement of the entire optical fiber, wherein each measurement signal frame contains a plurality of measurement signal elements, each measurement signal element is used to sense a specific measurement point in the optical fiber; the measurement signal element includes a pump light and a probe light, and there is a specific time delay relationship between the pump light and the probe light, which is used to generate a nonlinear scattering effect at a predetermined measurement point in the optical fiber.

2. The distributed optical fiber sensing and transmission method based on optical packetization according to claim 1, characterized in that: The pump light is a pulse with high power and narrow pulse width, and the detection light is a rectangular square wave signal.

3. The distributed optical fiber sensing and transmission method based on optical packetization according to claim 2, characterized in that: The pump light and the probe light are injected into the optical fiber in the same direction but not at the same time. The probe light is reflected by the fiber Bragg grating (FBG) at the end of the optical fiber to become reverse probe light, propagates in the opposite direction of the pump light, and meets a predetermined measurement point in the optical fiber to cause nonlinear scattering, including Brillouin scattering or Raman scattering.

4. The distributed optical fiber sensing and transmission method based on optical packetization according to claim 3 is characterized in that: The time delay intervals of the pump light pulse and the detection light signal inside each measurement signal element are different, so that the constructed measurement signal frame can cover all measurement points on the optical fiber, realizing all-fiber distributed measurement.

5. The distributed optical fiber sensing and transmission method based on optical packetization according to any one of claims 1 to 4, characterized in that: The relationship between the duration T0 of the measurement signal frame and the duration τ0 of the measurement signal element is determined by the following formula: T0=m*τ0; Where m is the number of measurement points in the optical fiber.

6. The distributed optical fiber sensing and transmission method based on optical packetization according to claim 5, characterized in that: The number of measurement points m in the optical fiber satisfies the following relationship with the total length L0 of the optical fiber and the spatial resolution l0:

7. The distributed optical fiber sensing and transmission method based on optical packetization according to claim 5 or 6, characterized in that: The duration τ0 of the measurement signal element is related to the total length L0 of the optical fiber and the group velocity v of the light. g The following relationship is satisfied:

8. The distributed optical fiber sensing and transmission method based on optical packetization according to claim 5 or 6, characterized in that: The time delay τ between the pump light and the detection light i With the measured point P i The distance L i The following relations are satisfied: Among them, L i From the fiber entrance to the measured point P i distance.

9. The distributed optical fiber sensing and transmission method based on optical packetization according to claim 1, characterized in that: The following steps are involved: Generate stable, high-quality continuous light and divide it into pump light path and detection light path; Modulating the pump light and the detection light to generate a measurement signal element including a high-power pump pulse and a rectangular square wave detection light; Control the time delay between pump light and probe light; Power amplification and polarization optimization of pump and probe light; Combine the pump light and the detection light and inject them into the single-mode single-core optical fiber; At the fiber Bragg grating at the end of the optical fiber, the probe light is reflected and propagates in the opposite direction to the pump light, and they meet at a predetermined position in the optical fiber and produce stimulated Brillouin scattering (SBS) effect. The signal acquisition and processing module is used to acquire and process the reverse propagating Brillouin scattering signal to obtain the sensing quantity of the measuring point in the optical fiber.

10. A distributed optical fiber sensing and transmission system based on optical packetization, characterized in that: include: Laser and optical signal generation module, used to generate stable, high-quality continuous light and divide it into pump light path and detection light path; An optical signal modulation and control module, which is used to modulate the pump light and the detection light to generate a measurement signal element including a high-power pump pulse and a rectangular square wave detection light; it includes a ns pulse generator and a coding module for pulse modulation of the pump light, and a 10 GHz microwave source and a coding module for modulating the detection light; A central control module, used to control the time delay between the pump light and the probe light so as to achieve the encounter at a predetermined position in the optical fiber and generate a stimulated Brillouin scattering effect; An optical signal amplification and optimization control module, including an erbium-doped fiber amplifier and a polarization controller, is used to amplify the power and optimize the polarization of the pump light and the detection light; Optical signal combining and injection fiber module, including 2*1 coupler and circulator, used to combine pump light and detection light and inject them into single-mode single-core fiber; The fiber sensing and stimulated Brillouin scattering module includes a fiber Bragg grating at the end of the optical fiber, which is used to reflect the probe light and make it propagate in the opposite direction of the pump light; The signal acquisition and processing module includes an optoelectronic processing module and a data server, which is used to acquire and process the reverse-propagating Brillouin scattering signal to obtain the sensing quantity of the measuring point in the optical fiber; The measurement signal elements are arranged sequentially in the time domain to form a measurement signal frame covering the entire length of the optical fiber. By adjusting the time delay between the pump light and the detection light, their encounter at a certain position in the optical fiber can be controlled.

Images