Remote large-scale sensing detection system based on optical fiber laser sensor
阅读说明：本技术 一种基于光纤激光传感器的远距离大规模传感探测系统 (Remote large-scale sensing detection system based on optical fiber laser sensor ) 是由 *** 孙志慧 刘小会 李淑娟 闵力 王蒙 李明 张绪成 张琳 倪家升 王昌 于 2019-09-25 设计创作，主要内容包括：本发明涉及传感探测技术领域,特别涉及一种基于光纤激光传感器的远距离大规模传感探测系统,包括复合光路结构、泵浦源、传输光缆和光纤激光传感器,其特征在于：所述复合光路结构由两个波分复用器WDM和一个隔离器ISO组成,所述两个波分复用器WDM型号为980/1550nm、包括WDM2和WDM3；所述泵浦源为980nm泵浦源,980nm泵浦源的输出端连接WDM1的980端口,WDM1的Com端连接传输光缆的一端,传输光缆的另一端连接复合光路结构的WDM2的Com端。本发明的有益效果为：有效减小由于远距离传输引起的瑞利散射对光纤激光传感器的影响,抑制其相干坍塌的产生,保证传感器正常工作。(The invention relates to the technical field of sensing detection, in particular to a long-distance large-scale sensing detection system based on an optical fiber laser sensor, which comprises a composite optical path structure, a pumping source, a transmission optical cable and the optical fiber laser sensor, and is characterized in that: the composite optical path structure consists of two Wavelength Division Multiplexers (WDM) and an Isolator (ISO), wherein the two Wavelength Division Multiplexers (WDM) are 980/1550nm in type and comprise WDM2 and WDM 3; the pump source is a 980nm pump source, the output end of the 980nm pump source is connected with the 980 port of the WDM1, the Com end of the WDM1 is connected with one end of the transmission optical cable, and the other end of the transmission optical cable is connected with the Com end of the WDM2 of the composite optical path structure. The invention has the beneficial effects that: the influence of Rayleigh scattering caused by long-distance transmission on the fiber laser sensor is effectively reduced, the generation of coherent collapse of the fiber laser sensor is inhibited, and the normal work of the sensor is ensured.)
1. The utility model provides a long-range large-scale sensing detecting system based on fiber laser sensor, includes compound light path structure, pumping source, transmission optical cable and fiber laser sensor, its characterized in that:
the composite optical path structure consists of two wavelength division multiplexers WDM and an isolator ISO, wherein the two wavelength division multiplexers WDM are 980/1550nm in type and comprise WDM2 and WDM3, the 980 end of the WDM2 is connected with the 980 end of the WD3, the com end of the WDM3 is connected with a DFB detector, the 155 end of the WDM3 is connected with the input end of the isolator ISO, the output end of the isolator ISO is connected with the 1550 end of the WDM2, and the WDM2, the WDM3 and the isolator ISO form a closed loop;
the pump source is a 980nm pump source, the output end of the 980nm pump source is connected with the 980 port of the WDM1, the Com end of the WDM1 is connected with one end of the transmission optical cable, and the other end of the transmission optical cable is connected with the Com end of the WDM2 of the composite optical path structure.
2. The remote large-scale sensing detection system based on the fiber laser sensor according to claim 1, characterized in that: the 1550 end of the WDM1 is connected with the input end of the Michelson interferometer through another isolator, the output end of the Michelson interferometer is connected with a wavelength division multiplexer, and the wavelength division multiplexer is connected with a demodulation system.
3. The remote large-scale sensing detection system based on the fiber laser sensor according to claim 1, characterized in that: when the pump source is changed to a 1480nm pump source, 980/1550nmWDM is changed to 1480/1550nmWDM, and ports of the WDM are connected with each other corresponding to the original connection mode.
4. The utility model provides a long-range large-scale sensing detecting system based on fiber laser sensor, includes wavelength division multiplexer WDM, pump source, transmission cable and fiber laser sensor, its characterized in that:
the type of wavelength division multiplexer WDM is 980/1550nm, 980 isolators are connected to 980 end of WDM, 980 isolators are connected to 980nm pumping source through one optical fiber of transmission cable, DFB detector is connected to the Com end of WDM, 1550 isolators are connected to 1550 end of WDM, 1550 isolators are connected to input end of Michelson interferometer through another transmission optical fiber, output end of Michelson interferometer is connected to wavelength division multiplexer, wavelength division multiplexer is connected to demodulation system.
5. The fiber laser sensor-based remote large-scale sensing detection system according to claim 4, wherein: when the pumping source is replaced by a 1480nm pumping source, 980/1550nmWDM is replaced by 1480/1550nmWDM, a 980 isolator is replaced by a 1480 isolator, and the ports of the WDM and the isolator are connected corresponding to the original connection mode.
Technical Field
The invention relates to the technical field of sensing detection, in particular to a remote large-scale sensing detection system based on an optical fiber laser sensor.
Background
In order to relieve the current situation of insufficient oil and gas supply in China, further search for oil and gas resources becomes urgent. In order to find oil and gas field resources buried in the ground by thousands of meters, people absorb and quote the technologies and theories of other subjects through continuous experiments and summarization for years, and a complete oil and gas resource exploration method and a complete oil and gas resource exploration technical system are established. However, with the continuous deepening of oil and gas exploration, most of structured oil and gas fields which are shallow in burial and simple in surface geological conditions are discovered and exploited, so that exploration targets are more and more concealed and more complex, the difficulty of exploration tasks is increasingly increased, and the improvement of exploration technologies is urgently needed.
The distributed feedback fiber laser (DFB-FL) has the advantages of stable single-mode operation, narrow line width, long coherence length, small size, easy networking, wavelength division multiplexing, stable structure and the like, so the fiber laser geophone based on the distributed feedback fiber laser (DFB-FL) technology has extremely high sensitivity and natural wavelength division multiplexing characteristics, is expected to reduce the volume of a sensor and simplify the array structure. Large-scale long-distance fiber laser sensor arrays are the main development trend of fiber laser sensors.
In the downhole oil exploration, the well depth can reach thousands of meters, and the temperature can reach more than 150 ℃, which means that a transmission optical cable with a few kilometers in front of the fiber laser sensor is needed. At present, a plurality of patents about fiber laser sensors are available, the invention patent with the application number of 200910087349.2 discloses a fiber laser sensor used on land and under water, the invention patent with the application number of 201010231239.1 discloses a fiber laser downhole detector, and the fiber laser downhole detector is used for solving the problems that the connection strength of thousands of meters of transmission cables is required to be ensured and the underground slurry environment is severe in the underground petroleum exploration.
However, a problem still exists at present in that the detection depth which can be realized by the fiber laser sensor is that the long-distance large-scale sensing cannot be realized in the prior art because the rayleigh scattering in the long-distance transmission fiber influences the fiber laser sensor, and the existing fiber laser sensor cannot realize long-distance transmission and large-scale detection.
The fiber laser sensor array usually adopts a remote pumping mode, and the length of transmission fibers in the array is further increased. Because the rayleigh scattering of the transmission fiber can generate extra-cavity feedback light, the feedback intensity is accumulated continuously along with the increase of the length of the fiber, the length of the coherent collapse threshold value of the transmission fiber determines the maximum array length of the fiber laser sensor array for stable work, and the rayleigh scattering of the transmission fiber becomes the main factor for limiting the multiplexing capacity of the array at present. The Rayleigh scattering intensity of the conventional single-mode fiber SM28 is about-72 d B/m, and the threshold length of the transmission fiber of the symmetrical-structure DFB fiber laser, which is subjected to coherent collapse when only the Rayleigh scattering of a single transmission fiber is considered, is 130 m. Assuming that the length of the transmission fiber between the pump end in the array and the first laser element in the array is 100m, and the distance between adjacent elements is 1m, the maximum multiplexing capacity of the array is only 30. As the cell pitch increases, the multiplexing capacity of the array will further decrease.
Chenzhihao et al, in Long distance (2.1km) DFB fiber laser hydrophon system, teach that the maximum length of the conductive fiber of a DFB fiber laser is 40 ~ 50m when pumping with a 980nm laser and up to 135 ~ 250m when pumping with a 1480nm laser.a method is proposed in this article to bend a section of the fiber on the side close to the DFB laser to increase the attenuation so that the reflection into the laser cavity is reduced and therefore very weak without affecting.
In 2013, r, Bouffaron et al in france reported a DFB fiber laser underwater detection system with full fiber, dual channels and 12 elements, and by suppressing the effect of rayleigh scattering in a remote pump transmission fiber, the array length exceeded 4 km, but the optical path structure thereof was not explained in detail.
Therefore, a system which can solve coherent collapse caused by rayleigh scattering in a long-distance transmission optical fiber, can effectively increase the underground detection depth of the optical fiber laser sensor and meets the requirement of deeper detection is needed to be designed.
Disclosure of Invention
The invention provides a remote large-scale sensing detection system based on an optical fiber laser sensor, aiming at overcoming the defect that the optical fiber laser sensor cannot work normally due to the influence of Rayleigh scattering in the prior art.
The invention is realized by the following technical scheme:
the utility model provides a long-range large-scale sensing detecting system based on fiber laser sensor, includes compound light path structure, pumping source, transmission optical cable and fiber laser sensor, its characterized in that:
the composite optical path structure consists of two wavelength division multiplexers WDM and an isolator ISO, wherein the two wavelength division multiplexers WDM are 980/1550nm in type and comprise WDM2 and WDM3, the 980 end of the WDM2 is connected with the 980 end of the WD3, the Com end of the WDM3 is connected with a DFB detector, the 1550 end of the WDM3 is connected with the input end of the isolator ISO, the output end of the isolator ISO is connected with the 1550 end of the WDM2, and the WDM2, the WDM3 and the isolator ISO form a closed loop;
the pump source is a 980nm pump source, the output end of the 980nm pump source is connected with the 980 port of the WDM1, the Com end of the WDM1 is connected with one end of the transmission optical cable, and the other end of the transmission optical cable is connected with the Com end of the WDM2 of the composite optical path structure.
Further, in order to better implement the present invention, the 1550 end of the WDM1 is connected to the input end of the Michelson interferometer through another isolator, the output end of the Michelson interferometer is connected to the wavelength division multiplexer, and the wavelength division multiplexer is connected to the demodulation system.
Further, in order to better implement the present invention, when the pump source is replaced with a 1480nm pump source, 980/1550nmWDM is replaced with 1480/1550nmWDM, and ports of the WDM are connected to each other corresponding to the original connection mode.
Increase a long-range large-scale sensing detection system based on fiber laser sensor after transmission fiber and change the light path structure, including wavelength division multiplexer WDM, pump source, transmission optical cable and fiber laser sensor, its characterized in that:
the type of wavelength division multiplexer WDM is 980/1550nm, 980 isolators are connected to 980 end of WDM, 980 isolators are connected to 980nm pumping source through one optical fiber of transmission cable, the Com end of WDM is connected to optical fiber laser sensor, 1550 isolator is connected to 1550 end of WDM, 1550 isolator is connected to input end of Michelson interferometer through another transmission optical fiber, output end of Michelson interferometer is connected to wavelength division multiplexer, wavelength division multiplexer is connected to demodulation system.
Further, in order to better implement the present invention, when the pump source is replaced with a 1480nm pump source, 980/1550nmWDM is replaced with 1480/1550nmWDM, 980 isolator is replaced with 1480 isolator, and WDM and isolator ports are connected according to the original connection mode.
The invention has the beneficial effects that:
the optical path structure can effectively reduce the influence of Rayleigh scattering noise in the long-distance transmission optical fiber on the output optical signal of the optical fiber laser sensor, because in the long-distance transmission optical fiber, although the optical signal carrying sensing information generates Rayleigh scattering and multiple reflection in the optical fiber, after the WDM2, the WDM3 and the isolator ISO are added, the combined structure only allows the pump light to enter the optical fiber laser sensor, and the Rayleigh scattering light in the transmission optical fiber is isolated by the ISO and cannot enter the optical fiber laser sensor, thereby eliminating the influence of Rayleigh scattering light.
Meanwhile, the structure can be used for realizing long-distance large-scale detector array detection. Because the fiber laser sensor has extremely high sensitivity and wavelength division multiplexing characteristics, space division multiplexing and time division multiplexing can be added to form hybrid multiplexing, and after large-scale array formation, the transmission fiber in the sensing array also has Rayleigh scattering, and after the influence of the transmission fiber is eliminated through the structure, the array scale cannot be influenced by the length of the transmission fiber, so that the number of the sensing array or the distance between the transmission arrays can be increased on a large scale, and detection in a larger range on a larger scale is realized.
On the premise of adopting the structure, the low Rayleigh scattering optical fiber can be adopted, and the influence of Rayleigh scattering is reduced to a greater extent.
Drawings
FIG. 1 is a schematic diagram of a first transmission optical path structure of a remote large-scale sensing detection system based on a fiber laser sensor according to the present invention;
FIG. 2 is a schematic diagram of a second transmission optical path structure of the remote large-scale sensing detection system based on the fiber laser sensor according to the present invention;
FIG. 3 is an image of interference fringes measured using the optical path structure of the present invention;
FIG. 4 is an image of interference fringes measured without using the optical path structure of the present invention;
FIG. 5 is a plot of output phase noise of a remote sensing system as measured using an optical circuit configuration of the present invention and an optical circuit configuration not in accordance with the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present invention, it should be noted that the terms "middle", "upper", "lower", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on orientations or positional relationships shown in the drawings or orientations or positional relationships conventionally laid out when products of the present invention are used, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.
Furthermore, the terms "horizontal", "vertical" and the like do not imply that the components are required to be absolutely horizontal or pendant, but rather may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the present invention, it should be noted that the terms "disposed," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected unless otherwise explicitly stated or limited. Either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Some embodiments of the invention are described in detail below with reference to the accompanying drawings. The embodiments described below and the features of the embodiments can be combined with each other without conflict.
Since the rayleigh scattering of the transmission fiber is proportional to the fiber length, the longer the transmission fiber, the greater the accumulated rayleigh scattering, and the more likely it is for coherent collapse of the fiber laser. The rayleigh scattering of the transmission fiber cannot be eliminated by some means, and therefore, the influence on the performance of the fiber laser sensor cannot be ignored, and the longer the length of the transmission fiber, the greater the accumulated rayleigh scattering intensity, and therefore, the phase noise of the fiber laser sensor increases with the increase in the length of the fiber. In order to ensure the normal operation of the fiber laser sensor, the influence of rayleigh scattering on the sensor and coherent collapse caused by rayleigh scattering must be eliminated.
Fig. 1 shows a first embodiment of the present invention, which is a remote large-scale sensing detection system based on a fiber laser sensor, and the remote detection of a detector is realized by using a composite optical path structure composed of two wavelength division multiplexers WDM (980/1550 or 1480/1550) and an isolator ISO at a position close to the fiber laser sensor at the far end of a transmission fiber. Taking a 980 pump source as an example, the output of the 980 pump source is connected with a 980 port of the WDM1, a Com end of the 980 pump source is connected with one end of a transmission optical cable, the other end of the transmission optical cable is connected with a Com end of the WDM2, a 980 end of the transmission optical cable is connected with a 980 end of the WDM3, a Com end of the WDM3 is connected with a DFB detector, a 1550 end of the WDM3 is connected with the input end of an isolator, and the output end of the isolator is connected with a 1550 end of the WDM2, so that a closed loop is formed.
According to the optical path structure, pumping light reaches the Com end of WDM2 through a transmission optical cable, then is output through the 980 end of WDM2 and enters the 980 end of WDM3, then enters the fiber laser sensor through the Com end of WDM3, generated signal light carrying sensing information reaches the 1550 end of WDM3 through the Com end of WDM3, then passes through an isolator ISO, enters the 1550 end of WDM2 and is output from the Com of WDM2 to the transmission optical cable, passes through the transmission optical cable and reaches the Com end of WDM1, then is output from the 1550 end and enters the Michelson interferometer through the isolator ISO, and then output signals of the Michelson interferometer are subjected to wavelength division multiplexing and demodulation and signal analysis processing.
The structure is also suitable for the situation of 1480 light source pumping, namely 980/1550 WDM is replaced by 1480/1550 WDM, and corresponding ports are connected with each other.
The structure can effectively reduce the influence of Rayleigh scattering noise in the long-distance transmission optical fiber on the output optical signal of the DFB detector, because in the long-distance transmission optical fiber, although the optical signal carrying the sensing information generates Rayleigh scattering and multiple reflection in the optical fiber, after the WDM2, the WDM3 and the isolator ISO are added, the combined structure only allows the pump light to enter the detector, and the Rayleigh scattering light in the transmission optical fiber is isolated by the ISO and cannot enter the optical fiber laser sensor, thereby eliminating the influence of Rayleigh scattering light.
Meanwhile, the structure can be used for realizing long-distance large-scale detector array detection. Because the DFB detector has extremely high sensitivity and wavelength division multiplexing characteristics, and can be added with space division multiplexing and time division multiplexing to form hybrid multiplexing, and after large-scale array formation, the transmission optical fiber in the sensing array also has Rayleigh scattering, and after the influence of the transmission optical fiber is eliminated through the structure, the array scale cannot be influenced due to the length of the transmission optical fiber, so that the number of the sensing array can be increased on a large scale or the distance of the transmission array can be increased, and larger-scale and larger-range detection can be realized.
In the
Fig. 2 is a second embodiment of the present invention, which takes a 980nm pump source as an example, the pump source light is transmitted to a far end through a transmission fiber, enters 980 end of 980/1550 WDM through 980 isolator, then enters the fiber laser sensor excitation signal light through Com end output, the optical signal carrying the sensing information returns to Com end of WDM, then is output from 1550 end, passes through 1550 isolator, and is transmitted to Michelson interferometer through transmission fiber, the output signal of Michelson interferometer is demodulated after being split by wavelength division multiplexer, and is processed by signal analysis. The
Also, the structure is suitable for the case of 1480 pump light source, pump is 1480 pump light, device is 1480 isolator, 1480/1550 WDM, 1550 isolator is unchanged.
Fig. 3, 4 and 5 are graphs of comparative experimental data measured in example 1, with a transmission fiber length of 5km, and examining interference fringes and phase noise output from the system in both cases, respectively, using the composite optical path structure mentioned in example 1 and the sensing system not using the optical path structure mentioned in example 1.
As can be seen from the test results in fig. 3 and fig. 4, after passing through about 5km of transmission fiber, the interference fringes are smooth and stable, and the sensor works normally after the composite optical path structure mentioned in this
Also in the case of transmitting 5km, as can be seen from the test result of fig. 5, with the composite optical path structure mentioned in this
Therefore, the multiplex optical path can effectively reduce the influence of Rayleigh scattering caused by long-distance transmission on the fiber laser sensor, inhibit the generation of coherent collapse of the fiber laser sensor and ensure the normal work of the sensor.
The coastline of China is vast, and the ocean is an important strategic space for sustainable development of the social economy of China and also an important barrier for national safety. The embodiment can also be applied to a remote transmission system of the fiber laser hydrophone, effectively increases the offshore distance detected by the hydrophone, and can strive for more sufficient maneuvering time for defense and warning.
Finally, the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting, and other modifications or equivalent substitutions made by the technical solutions of the present invention by those of ordinary skill in the art should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.
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