Sensing equipment and sensing system
By introducing an amplification unit and simplifying the light source structure in distributed fiber sensors, the problem of signal-to-noise ratio reduction in long-distance sensing is solved by using phase-sensitive amplification technology, and accurate sensing at a longer distance is achieved.
Patent Information
- Application Number
- CN202310790660.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-29
- Publication Date
- 2024-12-31
AI Technical Summary
In the case of long-distance sensing, the increase in noise in distributed fiber sensors leads to a decrease in signal-to-noise ratio, and the accurate sensing signal cannot be obtained, limiting the sensing distance.
By introducing an amplification unit into the sensing device, phase-sensitive amplification is achieved using idle frequency light and pump light, the amplification of the stimulated detection light, the sensitivity to detection of changes in the physical quantity of the sensing optical fiber is enhanced, and the optical frequency comb and non- Linear media simplifies the light source structure and reduces system complexity and cost.
Improved signal-to-noise ratio in long-distance sensing, ensured the accuracy of the sensing signal, extended the sensing distance, and reduced system costs.
Smart Images
Figure CN119223337A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present application relate to the field of sensing, and in particular, to a sensing device and a sensing system. Background Art
[0002] Distributed fiber optic sensors can obtain continuous distribution information of the measured field in time and space along the fiber path, and distributed fiber optic sensors have good anti-electromagnetic interference and good chemical stability. Therefore, distributed fiber optic sensing technology is widely used in sensing of different scenarios.
[0003] Fiber-optic distributed sensing technology includes distributed temperature / strain sensing technology (distributed temperature strain sensing, DTSS) based on Brillouin scattering. This technology obtains temperature or strain information distributed along the optical fiber by detecting the frequency shift and intensity of Brillouin scattered light from the sensing optical fiber. Since the attenuation and dispersion of the optical signal are small near the working wavelength of Brillouin scattering, DTSS has the advantages of high measurement accuracy, large measurement range, and high spatial resolution compared to other distributed fiber-optic sensing technologies.
[0004] However, with the upgrading of sensing requirements, the sensing distance is getting longer and longer, and the sensing fiber is getting longer and longer. The increase in the length of the sensing fiber makes the noise in the DTSS larger and larger, thereby reducing the signal-to-noise ratio of the DTSS. As a result, in the case of long-distance sensing, it is impossible to obtain accurate sensing signals, which limits the sensing distance. Summary of the invention
[0005] The embodiments of the present application provide a sensing device and a sensing system for improving detection sensitivity and sensing distance.
[0006] In a first aspect, an embodiment of the present application provides a sensing device. The device includes: a light source, a sensing unit, and an amplifying unit. The light source is used to obtain idle light λ1, detection light λ2, and pump light λp, so that the idle light λ1 and the pump light λp meet the first condition for phase-sensitive amplification of the detection light λ2, and output the detection light λ2 to the sensing unit, and output the pump light λp and the idle light λ1 to the amplifying unit. The sensing unit is used to connect to the sensing optical fiber, and output the detection light λ2 to the sensing optical fiber, and output the stimulated detection light λ2' to the amplifying unit. Among them, the stimulated detection light λ2' is obtained by the stimulated Brillouin action of the detection light λ2 in the sensing optical fiber. The amplifying unit includes an amplifying module and a detecting module. The amplifying module is used to perform phase-sensitive amplification on the stimulated detection light λ2' according to the idle light λ1 and the pump light λp, and obtain the target detection light λ2". The detecting module is used to detect the target detection light λ2", and obtain the sensing signal of the sensing optical fiber.
[0007] In an embodiment of the present application, an amplification unit is added to the sensing device, and phase-sensitive amplification of stimulated detection light λ2' is achieved on the amplification unit through idle light λ1 and pump light λp. Since phase-sensitive amplification can achieve low-noise amplification of a certain frequency signal, when the signal-to-noise ratio is reduced due to long-distance transmission, the stimulated detection light λ2' coupled to the change in the physical quantity of the sensing optical fiber can be amplified separately, thereby improving the detection sensitivity of the change in the physical quantity of the sensing optical fiber. Accurate sensing signals can also be obtained in the case of long-distance sensing, thereby achieving the expansion of the sensing distance.
[0008] In an optional implementation, the light source is specifically used to obtain idle light λ1, detection light λ2 and pump light λp with frequencies ω1, ω2 and ωp respectively, so that the frequencies of the idle light λ1, detection light λ2 and pump light λp satisfy a first condition, and the first condition includes: 2ωp=ω1+ω2.
[0009] In the embodiment of the present application, the two photons involved in amplification are both from one pump light, so the amount of pump light can be reduced, thereby achieving system simplification and cost reduction.
[0010] In an optional implementation, the pump light λp includes a first pump light λp1 and a second pump light λp2. The light source is specifically used to: obtain an idle light λ1, a detection light λ2, a first pump light λp1, and a second pump light λp2 with frequencies ω1, ω2, ωp1, and ωp2, respectively, so that the frequencies of the idle light λ1, the detection light λ2, and the pump light λp meet a first condition, and the first condition includes: ωp1+ωp2=ω1+ω2.
[0011] In the embodiment of the present application, since two pump lights with independent frequencies are used, the spectral width of phase-sensitive amplification can be expanded, thereby achieving amplification of signals within a wider signal bandwidth.
[0012] In an optional implementation, the light source includes: a laser light source, used to emit a detection light λ2, and output the detection light λ2 to a first nonlinear medium; a pump light source, used to emit a pump light λp, and output the pump light λp to the first nonlinear medium; the first nonlinear medium, used to generate an idler light λ1 according to the pump light λp and the detection light λ2, so that the frequencies of the idler light λ1, the detection light λ2 and the pump light λp meet a first condition.
[0013] In the embodiment of the present application, the idle light λ1 is the light generated by the pump light λp and the probe light λ2 in the first nonlinear medium. Since the three lights mentioned above will undergo three-wave mixing (or four-wave mixing) in the first nonlinear medium, the frequencies of the three lights (or four lights, if the pump light λp includes the first pump light λp1 and the second pump light λp2) naturally satisfy the relationship of the first condition. Therefore, the first condition mentioned above can be satisfied without additionally controlling the frequencies of the three lights (or four lights, as above), so that the structure of the light source is simple and the manufacturing difficulty is low.
[0014] In an optional implementation, the light source includes: an optical frequency comb for acquiring pump light λp, idler light λ1 and probe light λ2, so that the frequencies of the idler light λ1, the probe light λ2 and the pump light λp meet a first condition.
[0015] In the embodiment of the present application, since the optical frequency comb has good frequency and phase correlation, optical signals of different frequencies can be produced by one light source, thereby reducing system complexity and cost and improving integration.
[0016] In an optional implementation, the amplification module includes a phase locker and a second nonlinear medium, and the sensing unit is specifically used to output the stimulated detection light λ2' to the second nonlinear medium. The detection module is also used to detect the phase of the stimulated detection light λ2'. The phase shifter is used to adjust the phase φp of the pump light λp and / or the phase φ1 of the idler light λ1 based on the change of the phase of the stimulated detection light λ2', and output the adjusted pump light λp' and idler light λ1' to the second nonlinear medium, so that the phases φp', φ1' and φ2' of the pump light λp', idler light λ1' and stimulated detection light λ2' input into the second nonlinear medium meet the second condition. The second nonlinear medium is used for phase-sensitively amplifying the stimulated detection light λ2' according to the adjusted pump light λp' and idler light λ1' to obtain the target detection light λ2". If the frequency of the pump light λp is ωp, the second condition includes: 2φp'=φ1'+φ2'; if the pump light λp includes a first pump light λp1 and a second pump light λp2 with different frequencies, and the pump light λp' input into the second nonlinear medium after adjustment includes the first pump light λp1' and the second pump light λp2', the second condition includes: φp1'+φp2'=φ1'+φ2'.
[0017] In an embodiment of the present application, if a frequency shift occurs during the transmission of the detection light λ2 or the stimulated detection light λ2' in the sensing optical fiber or the sensing device, the frequency shift of the idle light λ1 and the pump light λp can be achieved by a phase shifter, so that the phase on the second nonlinear medium always satisfies the second condition, thereby ensuring phase-sensitive amplification of the stimulated detection light λ2' regardless of any changes in the system.
[0018] In an optional implementation, the sensing unit is specifically used to: output the detection light λ2 and the third pump light λp3 to the sensing optical fiber, so that the frequency difference between the detection light λ2 and the third pump light λp3 is the Brillouin frequency of the sensing optical fiber; output the stimulated detection light λ2' to the amplification unit, and the stimulated detection light λ2' is the light obtained by the stimulated Brillouin action of the detection light λ2 and the third pump light λp3 on the sensing optical fiber.
[0019] In the embodiment of the present application, the frequency of the detection light beam is moved by a frequency shifter, so that the frequency difference between the generated third pump light λp3 and the detection light λ2 can be fixed to the Brillouin frequency of the sensing optical fiber. It can be ensured that in any case (including the slow frequency shift of the detection light λ2, the sudden appearance of large noise in the system, etc.), the frequency difference between the detection light λ2 and the third pump light λp3 is constant, thereby ensuring that in any case, the detection light λ2 can generate the Brillouin effect on the sensing optical fiber based on the excitation of the third pump light λp3, thereby ensuring the performance stability of the sensing device.
[0020] In an optional implementation, the sensing unit also includes: a first modulation module, used to modulate at least one of the intensity, phase, frequency, and polarization of the first target light to obtain a third pump light λp3, where the first target light is obtained by splitting the detection light λ2, or comes from a target pump light source.
[0021] In an embodiment of the present application, by modulating the intensity, phase, frequency, polarization, etc. of the first target light λ3 through the first modulation module, different types of Brillouin analysis can be realized. For example, frequency modulation can realize BOCDA or BOFDA analysis, and pulse modulation can realize BOTDA analysis.
[0022] In an optional implementation, the light source further includes: a second modulation module, which is used to modulate at least one of the intensity, phase, frequency and polarization of the second target light to obtain the detection light λ2, and the second target light comes from the laser light source.
[0023] In an embodiment of the present application, the second target light can be modulated in terms of light intensity, phase, frequency, polarization, etc. by a second modulation module in the light source, thereby obtaining different types of detection light λ2 to realize different types of Brillouin analysis. For example, frequency modulation can realize BOCDA or BOFDA analysis, and pulse modulation can realize BOTDA analysis.
[0024] In an optional implementation, the sensing device further includes a processing unit. The detection module is further used to detect the phase and polarization of the target detection light λ2″. The processing unit is used to implement coherent detection of the sensing optical fiber according to the phase and polarization of the target detection light λ2″.
[0025] In the embodiments of the present application, the signal-to-noise ratio of the sensing device can be improved through coherent detection, thereby further improving the detection sensitivity and further extending the sensing distance.
[0026] In a second aspect, an embodiment of the present application provides a sensing system, the sensing system comprising the sensing device and a sensing optical fiber as described in the first aspect. The sensing optical fiber is connected to a sensing unit of the sensing device. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 A schematic diagram of a distributed optical fiber sensing system of the present application;
[0028] Figure 2 A schematic diagram of the structure of a sensor device provided in an embodiment of the present application;
[0029] Figure 3a A schematic structural diagram of a light source including a nonlinear medium provided in an embodiment of the present application;
[0030] Figure 3b A structural schematic diagram of a light source including a light source comb provided in an embodiment of the present application;
[0031] Figure 4a Another structural schematic diagram of a light source including a nonlinear medium provided in an embodiment of the present application;
[0032] Figure 4b Another structural schematic diagram of a light source including a light source comb provided in an embodiment of the present application;
[0033] Figure 5 A schematic diagram of the structure of an amplification unit provided in an embodiment of the present application;
[0034] Figure 6 A structural schematic diagram of a sensor unit provided in an embodiment of the present application;
[0035] Figure 7 Another schematic diagram of the structure of the sensor device provided in an embodiment of the present application. DETAILED DESCRIPTION
[0036] The embodiments of the present application are described below in conjunction with the accompanying drawings. Those skilled in the art will appreciate that, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.
[0037] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged in appropriate circumstances, which is only to describe the distinction mode adopted by the objects of the same attribute in the embodiments of the present application when describing. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment containing a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment. In addition, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or", describes the association relationship of associated objects, indicating that three relationships can exist, for example, A and / or B, can represent: A exists alone, A and B exist simultaneously, and B exists alone, wherein A, B can be singular or plural. The character " / " generally represents that the associated objects before and after are a kind of "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.
[0038] like Figure 1 As shown, the distributed temperature / strain sensing DTSS system includes a measured field and a distributed optical fiber sensor. The distributed optical fiber sensor includes a light source, a sensing optical fiber, a detection unit, a computing unit, and the like.
[0039] Among them, the light source is used to emit detection light and input the detection light into the sensing fiber. The sensing fiber is distributed along the measured field, and the detection light undergoes stimulated Brillouin action in the sensing fiber to obtain stimulated detection light, thereby coupling the temperature, strain and other information in the measured field to the stimulated detection light. The stimulated detection light is transmitted to the detection unit through the sensing fiber. The detection unit is used to detect the phase, intensity, etc. of the target detection light, and the calculation unit obtains the temperature, strain and other information of the measured field based on the above phase, intensity, etc.
[0040] The measured field may be an oil and gas pipeline, a power line, a communication optical cable, a mine tunnel, a railroad track, etc., and this application does not limit this. For example, if the measured field is an oil and gas pipeline, the sensing optical fiber is laid along the extension direction of the pipeline. The sensing optical fiber can transmit information such as temperature and strain on the pipeline to the computing unit through stimulated detection light.
[0041] As the demand increases, the length of the measured field (the distance in the extension direction) becomes longer and longer, which makes the length of the sensing fiber longer and longer. The increase in the length of the sensing fiber will introduce more noise into the DTSS system. As a result, the signal-to-noise ratio in the stimulated detection light becomes lower and lower. The reduction in the signal-to-noise ratio makes it impossible for the computing unit to obtain accurate sensing signals. Due to the above reasons, the sensing distance of DTSS is limited.
[0042] In order to solve the above problems, the embodiments of the present application provide a sensing device and a sensing system. The sensing device and system improve the sensitivity of detection through phase-sensitive amplification, so that when the signal-to-noise ratio is low due to long-distance sensing, the influence of noise is reduced through high-sensitivity detection, and accurate sensing signals are obtained, so that the sensing distance of DTSS can be extended.
[0043] like Figure 2 As shown, the sensing device 2000 provided in the embodiment of the present application includes: a light source 2100 , a sensing unit 2200 and an amplifying unit 2300 .
[0044] Among them, the light source 2100 is used to obtain the idle light λ1, the detection light λ2 and the pump light λp, and make the idle light λ1 and the pump light λp meet the condition of phase-sensitive amplification of the detection light λ2, which is referred to as the first condition in this application. Since the phase-sensitive amplification needs to meet the corresponding relationship in frequency, the light source 2100 mainly limits the frequencies ω1, ω2 and ωp of the idle light λ1, the detection light λ2 and the pump light λp to meet the first condition. The light source 2100 is also used to output the detection light λ2 to the sensing unit 2200, and output the idle light λ1 and the pump light λp to the amplification unit 2300.
[0045] The frequency ω2 of the detection light λ2 is the frequency of the Brillouin effect on the sensing fiber. That is, the physical quantity change of the sensing fiber can be coupled to the light with the frequency ω2. For example, the detection light λ2 input to the sensing unit 2200 is used to couple the physical quantity changes such as temperature and strain of the measured field to obtain the stimulated detection light λ2'.
[0046] In the embodiment of the present application, the sensing unit 2200 is used to connect to the sensing optical fiber. After the detection light λ2 with a frequency of ω2 is input to the sensing unit 2200, it is output to the sensing optical fiber through the sensing unit 2200. The detection light λ2 undergoes stimulated Brillouin action in the sensing optical fiber to obtain stimulated detection light λ2'. The stimulated detection light λ2' is output to the amplification unit through the sensing unit 2200.
[0047] Since the sensing fiber extends along the measured field, changes in physical quantities (such as temperature, stress, etc.) at a certain point in the measured field will cause changes in physical quantities at the corresponding position on the sensing fiber. These changes in physical quantities are coupled to the stimulated detection light λ2' with a frequency of ω2 through the Brillouin action of the sensing fiber. Therefore, the stimulated detection light λ2' can reflect changes in physical quantities in the measured field.
[0048] The amplification unit 2300 includes an amplification module 2310 and a detection module 2320 . The stimulated detection light λ2 ′ is input to the amplification module 2310 via the sensor unit 2200 , and the idler light λ1 and the pump light λp are input to the amplification module 2310 via the light source 2100 .
[0049] From the above description of the light source 2100, it can be seen that the idler light λ1 and the pump light λp meet the first condition for phase-sensitive amplification of the detection light λ2. Since the frequency of the stimulated detection light λ2' is the same as the frequency of the detection light λ2, both are ω2, and phase-sensitive amplification mainly limits the frequency relationship between light beams, the idler light λ1 and the pump light λp that meet the first condition can achieve phase-sensitive amplification of the stimulated detection light λ2'.
[0050] Therefore, the amplification module 2310 can perform phase-sensitive amplification on the stimulated detection light λ2' through the idler light λ1 and the pump light λp to obtain the target detection light λ2". The detection module 2320 is used to detect the phase change of the target detection light λ2" to obtain the sensing signal of the sensing optical fiber, that is, the sensing signal of the measured field.
[0051] In the embodiment of the present application, the idle light λ1 and the pump light λp are input into the amplification unit 2300. The idle light λ1 and the pump light λp satisfy the first condition for phase-sensitive amplification of the detection light λ2 with a frequency of ω2, and also satisfy the condition for phase-sensitive amplification of the stimulated detection light λ2' with a frequency of ω2 (i.e., the light coupled with the change of the physical quantity of the sensing optical fiber). Since phase-sensitive amplification can achieve low-noise amplification of a certain frequency signal, the stimulated detection light λ2' coupled with the change of the physical quantity of the sensing optical fiber can be amplified separately when the signal-to-noise ratio is reduced due to long-distance transmission, thereby improving the detection sensitivity of the change of the physical quantity of the sensing optical fiber. Accurate sensing signals can also be obtained in the case of long-distance sensing, thereby achieving the extension of the sensing distance.
[0052] Optionally, the first condition may be different according to the frequency distribution of the pump light λp, which will be described in detail below.
[0053] Optionally, if the frequency distribution of the pump light λp is approximately Gaussian, that is, the pump light λp has only one center frequency, the first condition is that the frequencies ω1, ω2, ωp of the idle light λ1, the detection light λ2 and the pump light λp satisfy 2ωp=ω1+ω2.
[0054] In order to obtain the idle light λ1, the probe light λ2 and the pump light λp that meet the first condition, the internal structure of the light source 2100 can be as follows: Figure 3a The light source 2100 includes a laser light source 2110 , a pump light source 2120 and a first nonlinear medium 2130 .
[0055] The laser light source 2110 is used to emit a detection light λ2 with a wavelength of ω2, and output the detection light λ2 to the first nonlinear medium 2130. The pump light source 2120 is used to emit a pump light λp with a frequency of ωp, and output the pump light λp to the first nonlinear medium 2130. The first nonlinear medium 2130 is used to generate an idler light λ1 with a frequency of ω1 according to the pump light λp and the detection light λ2, so that 2ωp=ω1+ω2.
[0056] In the embodiment of the present application, the idle light λ1 is the light generated by the pump light λp and the probe light λ2 in the first nonlinear medium 2130. Since the three lights will undergo three-wave mixing in the first nonlinear medium 2130, the frequencies of the three lights naturally satisfy the relationship 2ωp=ω1+ω2. Therefore, the first condition can be met without additionally controlling the frequencies of the three lights, so that the structure of the light source 2100 is simple and the manufacturing difficulty is low.
[0057] Optionally, the internal structure of the light source 2100 may also be as follows: Figure 3b As shown, it includes an optical frequency comb 2140 (also referred to as light source comb 2140 in this application). The optical frequency comb 2140 is used to obtain pump light λp, idler light λ1 and probe light λ2, so that the frequencies ω1, ω2 and ωp of the idler light λ1, probe light λ2 and pump light λp satisfy 2ωp=ω1+ω2.
[0058] In the embodiment of the present application, since lasers of different frequencies come from one light source in the optical frequency comb scheme, the idle light λ1, the detection light λ2 and the pump light λp have good frequency correlation and fewer components, the system can be simplified to achieve higher integration and lower cost.
[0059] Optionally, if the pump light λp has two center frequencies, that is, the pump light λp includes a first pump light λp1 and a second pump light λp2, then the first condition is: the frequencies ω1, ω2, ωp1, ωp2 of the idle light λ1, the detection light λ2, the first pump light λp1 and the second pump light λp2 satisfy ωp1+ωp2=ω1+ω2.
[0060] In order to obtain the idle light λ1, the probe light λ2, the first pump light λp1 and the second pump light λp2 that meet the first condition, the internal structure of the light source 2100 can be as follows: Figure 4aThe light source 2100 includes a laser light source 2110 , a pump light source (including a first pump light source 2121 and a second pump light source 2122 ) and a first nonlinear medium 2130 .
[0061] The laser light source 2110 is used to emit a detection light λ2 with a wavelength of ω2, and output the detection light λ2 to the first nonlinear medium 2130. The first pump light source 2121 is used to emit a first pump light λp1 with a frequency of ωp1, and output the first pump light λp1 to the first nonlinear medium 2130. The second pump light source 2122 is used to emit a second pump light λp2 with a frequency of ωp2, and output the second pump light λp2 to the first nonlinear medium 2130. The first nonlinear medium 2130 is used to generate an idler light λ1 with a frequency of ω1 according to the first pump light λp1, the second pump light λp2 and the detection light λ2, so that ωp1+ωp2=ω1+ω2.
[0062] In the embodiment of the present application, the idle light λ1 is the light generated by the first pump light λp1, the second pump light λp2 and the detection light λ2 on the first nonlinear medium 2130. Since the above four lights will undergo four-wave mixing on the first nonlinear medium 2130, the frequencies of the four lights naturally satisfy the relationship ωp1+ωp2=ω1+ω2. Therefore, the above first condition can be met without additionally controlling the frequencies of the four lights, so that the structure of the light source 2100 is simple and the manufacturing difficulty is low.
[0063] Optionally, the internal structure of the light source 2100 may also be as follows: Figure 4b As shown, an optical frequency comb 2140 (also referred to as a light source comb 2140 in this application) is included. The optical frequency comb 2140 is used to obtain a first pump light λp1, a second pump light λp2, an idler light λ1, and a probe light λ2, so that the frequencies ω1, ω2, ωp1, and ωp2 of the idler light λ1, the probe light λ2, the first pump light λp1, and the second pump light λp2 satisfy ωp1+ωp2=ω1+ω2.
[0064] In the embodiments of the present application, lasers of different frequencies come from one light source, have good frequency correlation, and have fewer components, thus simplifying the system and achieving higher integration and lower cost.
[0065] In the embodiment of the present application, in order to detect the change of physical quantity at various locations in the sensing optical fiber, it is necessary to perform a slow frequency drift on λ2 (i.e., it is necessary to perform a slow change on ω2) so as to obtain the sensing signal of the full frequency within the predetermined range. Through the light source 2100 of any structure described above, the idle light λ1 and the pump light λp can be changed with the frequency change of the detection light λ2, so that the idle light λ1 and the pump light λp meet the first condition for phase-sensitive amplification of the detection light λ2.
[0066] Optionally, the internal structure of the amplification unit 2300 may be as follows: Figure 5 The amplification unit 2300 includes an amplification module 2310 and a detection module 2320 . The amplification module 2310 includes a phase locker 2311 , a phase lock controller 2312 and a second nonlinear medium 2313 .
[0067] The stimulated detection light λ2 ′ is outputted by the sensing unit 2200 to the second nonlinear medium 2313 . The detection module 2320 connected to the second nonlinear medium 2313 can be used to detect the phase of the stimulated detection light λ2 ′ in the second nonlinear medium 2313 .
[0068] The detection module 2320 can transmit the phase of the stimulated detection light λ2' to the phase shift controller 2312. The phase shift controller 2312 can control the phase shifter 2311 to adjust the phase φp of the pump light λp and / or the phase φ1 of the idler light λ1 based on the change of the phase of the stimulated detection light λ2', obtain the pump light λp' and the idler light λ1', and output the adjusted pump light λp' and idler light λ1' to the second nonlinear medium 2313. Under the control of the phase shift controller 2312, the phase shifter 2311 makes the phases φp', φ1' and φ2' of the pump light λp', the idler light λ1' and the stimulated detection light λ2' input into the second nonlinear medium 2313 meet the phase condition of phase-sensitive amplification, which is referred to as the second condition in this application.
[0069] On the second nonlinear medium 2313, if the phase satisfies the second condition, the second nonlinear medium 2313 can perform phase-sensitive amplification on the stimulated detection light λ2' according to the pump light λp' and the idler light λ1' to obtain the target detection light λ2".
[0070] Optional, Figure 5 This is an example of a structure in which the phase shifter 2311 adjusts both the phase φp of the pump light λp and the phase φ1 of the idler light λ1. If only one of them is adjusted, the structure will be adjusted accordingly, and examples will not be given one by one here.
[0071] Optionally, the second condition may be different depending on the frequency distribution of the pump light λp, which will be described in detail below.
[0072] Optionally, if the frequency distribution of the pump light λp is approximately Gaussian distribution, that is, the pump light λp has only one central frequency, then the second condition is: 2φp'=φ1'+φ2'.
[0073] If the pump light λp includes a first pump light λp1 and a second pump light λp2 with different frequencies, the phase shifter 2311 can adjust at least one of the phase φp1 of the first pump light λp1, the phase φp12 of the second pump light λp2, and the phase φ1 of the idler light λ1. After adjustment, the pump light λp' input into the second nonlinear medium 2313 includes the first pump light λp1' and the second pump light λp2', and the second condition includes: φp1'+φp2'=φ1'+φ2'.
[0074] In the embodiment of the present application, if the frequency offset occurs during the transmission of the detection light λ2 or the stimulated detection light λ2' in the sensing optical fiber or the sensing device 2000, the frequency shift of the idle light λ1 and the pump light λp can be achieved by the phase shifter 2311, so that the phase on the second nonlinear medium 2313 always satisfies the second condition, thereby ensuring phase-sensitive amplification of the stimulated detection light λ2' regardless of any changes in the system.
[0075] Optional, Figure 2 The sensing unit 2200 in the embodiment of the present application can have different structures. In the embodiment of the present application, different types of stimulated detection light λ2' are obtained by different structures of the sensing unit 2200, so as to realize different types of Brillouin sensing detection. For example, Brillouin optical time domain analysis (BOTDA), Brillouin optical frequency domain analysis (BOFDA), Brillouin optical correlation domain analysis (BOCDA), etc. can be realized, which will be described separately below.
[0076] like Figure 6 As shown, the sensing unit 2200 may include a coupler, a frequency shifter, a first modulation module, an optical amplifier, an optical circulator, an isolator, etc. The coupler is used to receive the detection light λ2 from the light source 2100 and split the detection light λ2 into two beams. One beam is input to the frequency shifter to generate the third pump light λp3. The other beam is input to the isolator to realize the input of the detection light λ2 to the sensing optical fiber.
[0077] Among them, in the path of generating the third pump light λp3, the detection light λ2 is frequency-shifted by the frequency shifter to generate the first target light λ3. Specifically, the frequency shifter can shift the frequency of the detection light λ2 according to the Brillouin frequency of the sensing optical fiber. The first target light λ3 is modulated by the first modulation module to generate the third pump light λp3. After being amplified by the optical amplifier, the third pump light λp3 enters the sensing optical fiber through the optical circulator.
[0078] Due to the effect of the frequency shifter, the frequency difference between the first target light λ3 and the detection light λ2 is the Brillouin frequency of the sensing fiber, which means that the frequency difference between the detection light λ2 and the third pump light λp3 on the sensing fiber is the Brillouin frequency of the sensing fiber. Thus, the detection light λ2 can be stimulated by the third pump light λp3 to produce a Brillouin effect on the sensing fiber, thereby obtaining the above-mentioned stimulated detection light λ2'. The stimulated detection light λ2' can be output to the amplification unit 2300 via the optical circulator.
[0079] In the embodiment of the present application, the frequency of the detection light beam is moved by a frequency shifter, so that the frequency difference between the generated third pump light λp3 and the detection light λ2 can be fixed to the Brillouin frequency of the sensing fiber. It can be ensured that in any case (including the slow frequency shift of the detection light λ2, the sudden appearance of large noise in the system, etc.), the frequency difference between the detection light λ2 and the third pump light λp3 is constant, thereby ensuring that in any case, the detection light λ2 can generate the Brillouin effect on the sensing fiber based on the excitation of the third pump light λp3, thereby ensuring the performance stability of the sensing device 2000.
[0080] Optionally, the first modulation module can be as follows Figure 6 As shown, the first target light λ3 is pulse modulated to obtain the third pump light λp3. In addition, the first modulation module can also perform other types of modulation on the first target light λ3, such as frequency modulation, light intensity modulation, phase modulation, polarization modulation, etc.
[0081] Optional, if Figure 7 As shown, the first modulation module ( Figure 7 If the first target light λ3 is pulse modulated (shown as pulse modulation in the figure), then in the processing unit, based on the sensing signal obtained by the detection module 2320, the sensing optical fiber can be subjected to BOTDA analysis to obtain sensing information such as temperature and stress of the sensing optical fiber, that is, sensing information such as temperature and stress of the measured field.
[0082] Optionally, if the first modulation module performs frequency modulation on the first target light λ3, then in the processing unit, based on the sensing signal acquired by the detection module 2320, BOCDA or BOFDA analysis can be performed on the sensing optical fiber to obtain sensing information such as temperature and stress of the sensing optical fiber, that is, sensing information such as temperature and stress of the measured field.
[0083] In an embodiment of the present application, by modulating the intensity, phase, frequency, polarization, etc. of the first target light λ3 through the first modulation module, different types of Brillouin analysis can be realized. For example, frequency modulation can realize BOCDA or BOFDA analysis, and pulse modulation can realize BOTDA analysis.
[0084] Optionally, the first target light λ3 may be Figure 6The detection light λ2 is obtained by frequency shifting, and can also be obtained by other means. For example, the sensor unit 2200 can also include a target pump light source to obtain the first target light λ3, which is not limited in the present application.
[0085] Corresponding to the first modulation unit, the light source 2100 may also include a second modulation module. The second modulation module is used to modulate at least one of the intensity, phase, frequency, and polarization of the second target light to obtain the detection light λ2. Optionally, the second target light may come from Figure 3a or Figure 4a The laser source 2110 in the Figure 3b or Figure 4b The optical frequency comb 2140 (which can also be seen as a laser light source) in the image.
[0086] In an embodiment of the present application, the second target light can be modulated in terms of light intensity, phase, frequency, polarization, etc. by a second modulation module in the light source 2100, thereby obtaining different types of detection light λ2 to realize different types of Brillouin analysis. For example, frequency modulation can realize BOCDA or BOFDA analysis, and pulse modulation can realize BOTDA analysis.
[0087] Optionally, the detection module 2320 may also be used to detect the phase and polarization of the target detection light λ2″. Then the processing unit (eg Figure 7 As shown in FIG. 1 , the optical fiber sensor can be used to realize coherent detection of the sensing optical fiber according to the phase and polarization of the target detection light λ2″.
[0088] In the embodiment of the present application, the signal-to-noise ratio of the sensing device 2000 can be improved through coherent detection, thereby further improving the detection sensitivity and further extending the sensing distance.
[0089] The present application also provides a sensor system. The sensor system includes Figures 2 to 7 The sensing device 2000 and the sensing optical fiber described in any embodiment of the present invention are connected to the sensing unit 2200 of the sensing device 2000. The sensing system can be regarded as Figure 1 Distributed fiber optic sensors in the DTSS system shown.
[0090] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.
[0091] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.
[0092] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
[0093] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.
[0094] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk and other media that can store program code.
Claims
1. A sensing device, characterized in that: include: A light source, used for acquiring idle light λ1, detection light λ2 and pump light λp, so that the idle light λ1 and the pump light λp satisfy a first condition for phase-sensitive amplification of the detection light λ2, and outputting the detection light λ2 to a sensing unit, and outputting the pump light λp and the idle light λ1 to an amplifying unit; The sensing unit is used to connect to the sensing optical fiber, output the detection light λ2 to the sensing optical fiber, and output the stimulated detection light λ2' to the amplification unit, wherein the stimulated detection light λ2' is obtained by the stimulated Brillouin effect of the detection light λ2 in the sensing optical fiber; The amplification unit includes an amplification module and a detection module. The amplification module is used to perform phase-sensitive amplification on the stimulated detection light λ2' according to the idle light λ1 and the pump light λp to obtain the target detection light λ2", and the detection module is used to detect the target detection light λ2", to obtain the sensing signal of the sensing optical fiber.
2. The sensing device according to claim 1, characterized in that The light source is specifically used for: The idle light λ1, the probe light λ2 and the pump light λp having frequencies ω1, ω2 and ωp respectively are acquired so that the frequencies of the idle light λ1, the probe light λ2 and the pump light λp satisfy the first condition, wherein the first condition includes: 2ωp=ω1+ω2.
3. The sensing device according to claim 1, characterized in that The pump light λp includes a first pump light λp1 and a second pump light λp2, and the light source is specifically used for: The idle light λ1, the detection light λ2, the first pump light λp1 and the second pump light λp2 with frequencies ω1, ω2, ωp1 and ωp2 respectively are acquired so that the frequencies of the idle light λ1, the detection light λ2 and the pump light λp1 meet the first condition, and the first condition includes: ωp1+ωp2=ω1+ω2.
4. The sensing device according to claim 2 or 3, characterized in that: The light source comprises: A laser light source, used for emitting the detection light λ2, and outputting the detection light λ2 to the first nonlinear medium; A pump light source, used for emitting the pump light λp and outputting the pump light λp to the first nonlinear medium; The first nonlinear medium is used to generate the idler light λ1 according to the pump light λp and the probe light λ2, so that the frequencies of the idler light λ1, the probe light λ2 and the pump light λp meet the first condition.
5. The sensing device according to claim 2 or 3, characterized in that: The light source comprises: An optical frequency comb is used to obtain the pump light λp, the idler light λ1 and the probe light λ2, so that the frequencies of the idler light λ1, the probe light λ2 and the pump light λp meet the first condition.
6. The sensor device according to any one of claims 1 to 5, characterized in that The amplification module includes a phase lock and a second nonlinear medium, and the sensing unit is specifically used to output the stimulated detection light λ2' to the second nonlinear medium; The detection module is further used to detect the phase of the stimulated detection light λ2'; The phase shifter is used to adjust the phase φp of the pump light λp and / or the phase φ1 of the idler light λ1 based on the change of the phase of the stimulated detection light λ2', and output the adjusted pump light λp' and idler light λ1' to the second nonlinear medium, so that the phases φp', φ1' and φ2' of the pump light λp', the idler light λ1' and the stimulated detection light λ2' input into the second nonlinear medium meet the second condition; The second nonlinear medium is used to perform phase-sensitive amplification on the stimulated detection light λ2' according to the adjusted pump light λp' and idler light λ1' to obtain the target detection light λ2"; If the frequency of the pump light λp is ωp, the second condition includes: 2φp'=φ1'+φ2'; If the pump light λp includes a first pump light λp1 and a second pump light λp2 with different frequencies, and the pump light λp' input into the second nonlinear medium after adjustment includes a first pump light λp1' and a second pump light λp2', then the second condition includes: φp1'+φp2'=φ1'+φ2'.
7. The sensor device according to any one of claims 1 to 6, characterized in that The sensing unit is specifically used for: Outputting the detection light λ2 and the third pump light λp3 to the sensing optical fiber, so that the frequency difference between the detection light λ2 and the third pump light λp3 is the Brillouin frequency of the sensing optical fiber; The stimulated detection light λ2 ′ is output to the amplification unit, where the stimulated detection light λ2 ′ is light obtained by stimulated Brillouin action of the detection light λ2 and the third pump light λp3 on the sensing optical fiber.
8. The sensor device according to any one of claims 1 to 7, characterized in that The sensing unit also includes: The first modulation module is used to modulate at least one of the intensity, phase, frequency and polarization of the first target light to obtain the third pump light λp3, wherein the first target light is obtained by splitting the detection light λ2 or comes from a target pump light source.
9. The sensor device according to any one of claims 1 to 8, characterized in that The light source also includes: The second modulation module is used to modulate at least one of the intensity, phase, frequency and polarization of the second target light to obtain the detection light λ2, where the second target light comes from a laser light source.
10. The sensor device according to any one of claims 1 to 9, characterized in that Also includes a processing unit; The detection module is further used to detect the phase and polarization of the target detection light λ2″; The processing unit is used to realize coherent detection of the sensing optical fiber according to the phase and polarization of the target detection light λ2″.
11. A sensing system, characterized in that: A sensing device and a sensing optical fiber comprising any one of claims 1 to 10; The sensing optical fiber is connected to the sensing unit of the sensing device.