Sensing system integrating OFDR and DAS

Abstract

The utility model relates to the field of optical fiber sensing, in particular to an OFDR and DAS integrated sensing system, which comprises a narrow linewidth laser, a first coupler, an OFDR module, a DAS module, a signal switching module, a circulator, a second coupler, a first photoelectric conversion module, a second photoelectric conversion module, a signal acquisition unit and a signal processing unit. The output end of the narrow linewidth laser is connected with the input end of the first coupler, the output end of the first coupler is connected with the input end of the OFDR module, and the output end of the first coupler is connected with the input end of the DAS module; the output end of the OFDR module is connected with the input end of the first photoelectric conversion module, and the output end of the first photoelectric conversion module is connected with the first input end of the signal acquisition unit; the output end of the DAS module is connected with the input end of the second photoelectric conversion module, and the output end of the second photoelectric conversion module is connected with the input end of the signal acquisition unit; and the OFDR module and the DAS module are switched through the signal switching module. According to the utility model, one set of system can realize high-precision test and long-distance test.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of optical fiber sensing technology, more particularly to a kind of sensing system and equipment of fusion OFDR and DAS. BACKGROUND

[0002] In the field of optical fiber sensing technology, Fiber-optic Distributed Acoustic Sensor (DAS) and Optical Frequency Domain Refractometer (OFDR) are two commonly used measurement techniques, each has unique advantages and application scenarios.DAS is usually used for long-distance measurement, and its spatial resolution is generally above meter level, suitable for occasions with low spatial resolution requirements.In contrast, OFDR can provide micron-level spatial resolution, suitable for short-distance, high-precision measurement requirements.It can be seen that OFDR and DAS are used as independent systems, each has advantages and disadvantages, and the prior art lacks a solution that can simultaneously meet long-distance and high-precision measurement requirements. SUMMARY

[0003] The utility model aims at overcoming at least one defect (deficiency) of the above prior art, and provides a sensing system that combines OFDR and DAS, to meet the sensing and detection requirements of long distance and high precision.

[0004] The utility model takes the technical scheme that a kind of sensing system that combines OFDR and DAS is presented, the sensing system includes narrow line width laser, first coupler, OFDR module, DAS module, signal switching module, circulator, second coupler, first photoelectric conversion module, second photoelectric conversion module, signal acquisition unit and signal processing unit;

[0005] The output end of the narrow line width laser is connected to the input end of the first coupler, the first output end of the first coupler is connected to the first input end of the OFDR module, and the second output end of the first coupler is connected to the first input end of the DAS module.

[0006] The first output end of the OFDR module is connected to the first input end of the signal switching module, the first output end of the DAS module is connected to the second input end of the signal switching module, and the output end of the signal switching module is connected to the first connection end of the circulator.

[0007] The second connecting end of the circulator is used for connecting a fiber to be tested, the third connecting end of the circulator is connected to the input end of the second coupler, the first output end of the second coupler is connected to the first input end of the first photoelectric conversion module, and the second output end of the second coupler is connected to the first input end of the second photoelectric conversion module.

[0008] The second output end of the DAS module is connected to the second input end of the first photoelectric conversion module, and the output end of the first photoelectric conversion module is connected to the first input end of the signal acquisition unit.

[0009] The second output end of the OFDR module is connected to the second input end of the second photoelectric conversion module, and the output end of the second photoelectric conversion module is connected to the second input end of the signal acquisition unit.

[0010] The output end of the signal acquisition unit is connected to the input end of the signal processing unit, the first output end of the signal processing unit is connected to the third input end of the signal switching module, the second output end of the signal processing unit is connected to the second input end of the OFDR module, and the third output end of the signal processing unit is connected to the second input end of the DAS module.

[0011] In the scheme, the OFDR module and the DAS module are fused in one sensing system, and the switching of the OFDR module and the DAS module is performed through the signal switching module, so that not only the switching of the two detection modes can be realized, but also the long-distance and high-precision sensing detection requirements can be realized by combining the two. DAS is suitable for measuring long distances, and OFDR is suitable for measuring short distances. Therefore, DAS and OFDR are combined into one system, which can be applied to occasions requiring high precision for measuring short distances and can also be applied to long-distance occasions. When high-precision measurement is required, DAS is used for rough measurement, and then OFDR is used for fine measurement, so that the flexibility of solving detection problems is improved, and multi-functional detection is provided.

[0012] Further, the OFDR module comprises an electro-optical modulation circuit and a fifth coupler.

[0013] The first output end of the first coupler is connected to the first input end of the electro-optical modulation circuit, the output end of the electro-optical modulation circuit is connected to the input end of the fifth coupler, the first output end of the fifth coupler is connected to the first input end of the signal switching module, the second output end of the fifth coupler is connected to the second input end of the second photoelectric conversion module, and the second output end of the signal processing unit is connected to the second input end of the electro-optical modulation circuit.

[0014] In the scheme, the electro-optical modulation circuit is used for modulating the passing laser, so as to realize the detection of the OFDR module.

[0015] Further, the electro-optical modulation circuit comprises an electro-optical modulator and an electro-optical modulator driving circuit.

[0016] The first output end of the first coupler is connected to the first input end of the electro-optical modulator, the output end of the electro-optical modulator is connected to the input end of the fifth coupler, the second output end of the signal processing unit is connected to the input end of the electro-optical modulator driving circuit, and the output end of the electro-optical modulator driving circuit is connected to the second input end of the electro-optical modulator.

[0017] In the scheme, the electro-optical modulator driving circuit receives the signal from the signal processing unit, the electro-optical modulator driving circuit receiving the modulation signal drives the electro-optical modulator, and the electro-optical modulator modulates the passing laser, thereby realizing the sensing detection of the OFDR module.

[0018] Further, the electro-optical modulator driving circuit is a linear sweep frequency circuit.

[0019] In the scheme, the electro-optical modulator driving circuit is a linear sweep frequency circuit, and the linear sweep frequency circuit drives the electro-optical modulator to change the passing laser into linear sweep frequency laser.

[0020] Further, the OFDR module further comprises a first erbium-doped fiber amplifier, the first output end of the fifth coupler is connected to the input end of the first erbium-doped fiber amplifier, and the output end of the first erbium-doped fiber amplifier is connected to the first input end of the signal switching module.

[0021] In the scheme, the first erbium-doped fiber amplifier is used for optical signal amplification of the passing laser, and the amplified optical signal is transmitted to the signal switching module.

[0022] Further, the DAS module comprises a sixth coupler and an acousto-optic modulation circuit.

[0023] The second output end of the first coupler is connected to the input end of the sixth coupler, the first output end of the sixth coupler is connected to the first input end of the acousto-optic modulation circuit, the output end of the acousto-optic modulation circuit is connected to the second input end of the signal switching module, the second output end of the sixth coupler is connected to the second input end of the first photoelectric conversion module, and the third output end of the signal processing unit is connected to the second input end of the acousto-optic modulation circuit.

[0024] In the scheme, the acousto-optic modulation circuit is used for modulating the passing laser into pulsed laser, thereby realizing the sensing detection of the DAS module.

[0025] Further, the acousto-optic modulation circuit comprises an acousto-optic modulator and an acousto-optic modulator driving circuit; a first output end of the sixth coupler is connected to a first input end of the acousto-optic modulator, and an output end of the acousto-optic modulator is connected to a second input end of the signal switching module;

[0026] A third output end of the signal processing unit is connected to an input end of the acousto-optic modulator driving circuit, and an output end of the acousto-optic modulator driving circuit is connected to a second input end of the acousto-optic modulator.

[0027] In the scheme, the acousto-optic modulator driving circuit receives a modulation signal from the signal processing unit, the processing signal comprises the width of the pulse, etc., the acousto-optic modulator driving circuit receiving the modulation signal drives the acousto-optic modulator, and the acousto-optic modulator modulates the passing laser into pulsed laser, thereby realizing sensing detection of the DAS module.

[0028] Further, the DAS module further comprises a second erbium-doped fiber amplifier; an output end of the acousto-optic modulation circuit is connected to an input end of the second erbium-doped fiber amplifier, and an output end of the second erbium-doped fiber amplifier is connected to a second input end of the signal switching module.

[0029] In the scheme, the second erbium-doped fiber amplifier is used for optical signal amplification of the passing pulsed laser, and the amplified optical signal is transmitted to the signal switching module and then enters the circulator to reach the to-be-detected optical fiber, so as to complete sensing detection.

[0030] Further, the fusion OFDR and DAS sensing system further comprises a third erbium-doped fiber amplifier; a third connection end of the circulator is connected to an input end of the third erbium-doped fiber amplifier, and an output end of the third erbium-doped fiber amplifier is connected to an input end of the second coupler.

[0031] In the scheme, the third erbium-doped fiber amplifier is used for optical signal amplification of the laser after completing detection, thereby improving the efficiency of detection result collection.

[0032] Further, the signal switching module is an optical switch;

[0033] And / or, the first photoelectric conversion module comprises a first photoelectric converter and a third coupler; a first output end of the second coupler is connected to a first input end of the third coupler, a second output end of the DAS module is connected to a second input end of the third coupler, an output end of the third coupler is connected to an input end of the first photoelectric converter, and an output end of the first photoelectric converter is connected to a first input end of the signal acquisition unit.

[0034] And / or, the second photoelectric conversion module comprises a second photoelectric converter and a fourth coupler; a second output end of the second coupler is connected with a first input end of the fourth coupler, a second output end of the OFDR module is connected with a second input end of the fourth coupler, an output end of the fourth coupler is connected with an input end of the second photoelectric converter, and an output end of the second photoelectric converter is connected with a second input end of the signal acquisition unit.

[0035] In the scheme, the signal switching module is an optical switch, which is a key part of the system and is used for switching the OFDR module and the DAS module.

[0036] Compared with the prior art, the utility model has the advantages that:

[0037] The DAS module and the OFDR module are integrated in one system, so that the long-distance and high-precision measurement requirements can be met. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The utility model discloses a structure diagram.

[0039] Figure 2 The utility model discloses a circuit diagram of electro-optical modulation circuit in the utility model.

[0040] Figure 3 The utility model discloses a circuit diagram of acoustooptic modulation circuit in the utility model.

[0041] 1, narrow line width laser, 2, first coupler, 3, OFDR module, 4, DAS module, 5, signal switching module, 6, circulator, 7, to be measured optical fiber, 8, third erbium-doped fiber amplifier, 9, second coupler, 10, signal acquisition unit, 11, signal processing unit, 31, third coupler, 32, first photoelectric converter, 41, fourth coupler, 42, second photoelectric converter, 310, electro-optical modulation circuit, 311, fifth coupler, 312, first erbium-doped fiber amplifier, 410, sixth coupler, 411, acoustooptic modulation circuit, 412, second erbium-doped fiber amplifier, 3101, electro-optical modulator drive circuit, 3102, electro-optical modulator, 4101, acoustooptic modulator drive circuit, 4102, acoustooptic modulator. Detailed Implementation

[0042] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this invention. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0043] Example 1

[0044] like Figure 1 As shown, this embodiment provides a sensing system that integrates OFDR and DAS. The sensing system includes a narrow linewidth laser 1, a first coupler 2, an OFDR module 3, a DAS module 4, a signal switching module 5, a circulator 6, a fiber under test 7, a second coupler 9, a first photoelectric conversion module, a second photoelectric conversion module, a signal acquisition unit 10, and a signal processing unit 11.

[0045] The output terminal of the narrow linewidth laser 1 is connected to the input terminal of the first coupler 2, the first output terminal of the first coupler 2 is connected to the first input terminal of the OFDR module 3, and the second output terminal of the first coupler 2 is connected to the first input terminal of the DAS module 4.

[0046] The first output terminal of the OFDR module 3 is connected to the first input terminal of the signal switching module 5, the first output terminal of the DAS module 4 is connected to the second input terminal of the signal switching module 5, and the output terminal of the signal switching module 5 is connected to the first connection terminal of the circulator 6.

[0047] The second connection end of the circulator 6 is used to connect to the optical fiber 7 under test, the third connection end of the circulator 6 is connected to the input end of the second coupler 9, the first output end of the second coupler 9 is connected to the first input end of the first photoelectric conversion module, and the second output end of the second coupler 9 is connected to the first input end of the second photoelectric conversion module.

[0048] The second output terminal of the DAS module 4 is connected to the second input terminal of the first photoelectric conversion module, and the output terminal of the first photoelectric conversion module is connected to the first input terminal of the signal acquisition unit 10.

[0049] The second output terminal of the OFDR module 3 is connected to the second input terminal of the second photoelectric conversion module, and the output terminal of the second photoelectric conversion module is connected to the second input terminal of the signal acquisition unit 10.

[0050] The output end of the signal collection unit 10 is connected to the input end of the signal processing unit 11, the first output end of the signal processing unit 11 is connected to the third input end of the signal switching module 5, the second output end of the signal processing unit 11 is connected to the second input end of the OFDR module 3, and the third output end of the signal processing unit 11 is connected to the second input end of the DAS module 4.

[0051] In specific implementation, the narrow linewidth laser 1 emits laser into the first coupler 2, the first coupler 2 divides the laser into two beams respectively, and the two beams respectively pass through the OFDR module 3 and the DAS module 4, and the signal switching module 5 is used to make any one of the two beams entering the OFDR module 3 and the DAS module 4 to enter the circulator 6 and then enter the to-be-measured optical fiber 7 to refract, if the laser entering the OFDR module 3 enters the circulator 6, the OFDR function is used for sensing detection, if the laser entering the DAS module 3 enters the circulator 6, the DAS function is used for sensing detection, the laser enters the to-be-measured optical fiber 7 through the circulator 6, scattering occurs in the to-be-measured optical fiber 7 and Rayleigh scattering light is generated, the generated Rayleigh scattering light is used as sensing light and is reflected to the second coupler 9 through the circulator 6, then the second photoelectric conversion module or the first photoelectric conversion module is used for photoelectric signal conversion, the obtained electric signal reaches the signal collection unit 10 and the signal processing unit 11 to complete collection and processing, and after the signal processing is completed, the OFDR function or the DAS function is realized. The signal switching module is used to switch the laser output by the OFDR module and the DAS module, so that the OFDR function and the DAS function can be compatible in one set of system, so that the application can meet the measurement requirements of long distance and high precision.

[0052] It can be understood that the narrow linewidth laser 1 and the first coupler 2, the first coupler 2 and the OFDR module 3, and the first coupler 2 and the DAS module 4 are optically connected;

[0053] The OFDR module 3 and the signal switching module 5, the DAS module 4 and the signal switching module 5, and the signal switching module 5 and the circulator 6 are optically connected;

[0054] The circulator 6 and the second coupler 9, the second coupler 9 and the first photoelectric conversion module, and the second coupler 9 and the second photoelectric conversion module are optically connected;

[0055] The DAS module 4 and the first photoelectric conversion module are optically connected, and the first photoelectric conversion module and the signal collection unit 10 are electrically connected;

[0056] The OFDR module 3 is connected with the second photoelectric conversion module by optical path, and the second photoelectric conversion module is connected with the signal acquisition unit 10 by electrical connection.

[0057] The signal acquisition unit 10 is connected with the signal processing unit 11, the signal processing unit 11 is connected with the signal switching module 5, the signal processing unit 11 is connected with the OFDR module 3, and the signal processing unit 11 is connected with the DAS module 4 by electrical connection.

[0058] Optionally, as shown in the figure, the OFDR module 3 comprises an electro-optical modulation circuit 310, a fifth coupler 311; Figure 2

[0059] The first output end of the first coupler 2 is connected with the first input end of the electro-optical modulation circuit 310, the output end of the electro-optical modulation circuit 310 is connected with the input end of the fifth coupler 311, the first output end of the fifth coupler 311 is connected with the first input end of the signal switching module 5, the second output end of the fifth coupler 5 is connected with the second input end of the second photoelectric conversion module, and the second output end of the signal processing unit is connected with the second input end of the electro-optical modulation circuit.

[0060] In specific implementation, the electro-optical modulation circuit 310 modulates the entering laser into modulated light, the modulated light enters the fifth coupler 311 and is divided into two beams of laser, one of which is used as signal light and the other is used as local oscillation light, the modulated signal light reaches the circulator 6, enters the to-be-measured optical fiber 7 through the circulator 6, and occurs Rayleigh scattering in the to-be-measured optical fiber 7 and generates Rayleigh scattering light, the generated Rayleigh scattering light is used as sensing light and enters the second coupler 9 through the circulator 6, the sensing light output by the first output end of the second coupler 9 and the local oscillation light occur coherent mixing in the second photoelectric conversion module, generate beat frequency signals and are further converted into electrical signals, and by analyzing the frequency and intensity of the electrical signals corresponding to the beat frequency signals, the scattering characteristics of different positions in the optical fiber can be determined, so that sensing and detection are realized.

[0061] It can be understood that the first coupler 2 is connected with the electro-optical modulation circuit 310, the electro-optical modulation circuit 310 is connected with the fifth coupler 311, the fifth coupler is connected with the signal switching module 5, and the fifth coupler 5 is connected with the second photoelectric conversion module by optical path, and the signal processing unit is connected with the electro-optical modulation circuit by electrical connection.

[0062] Optionally, the electro-optical modulation circuit 310 comprises an electro-optical modulator driving circuit 3101 and an electro-optical modulator 3102.

[0063] ​The first output end of the first coupler 2 is connected to the first input end of the electro-optical modulator 3102, the output end of the electro-optical modulator 3102 is connected to the input end of the fifth coupler 311, the second output end of the signal processing unit 11 is connected to the input end of the electro-optical modulator driving circuit 3101, and the output end of the electro-optical modulator driving circuit 3101 is connected to the second input end of the electro-optical modulator 3102.

[0064] In specific implementation, the input end of the electro-optical modulator driving circuit 3101 is connected to the second output end of the signal processing unit 11, the signal processing unit 11 sends a driving signal to the electro-optical modulator driving circuit 3101, the electro-optical modulator driving circuit 3101 drives the electro-optical modulator 3102 according to the driving signal, so that the electro-optical modulator 3102 modulates the incoming laser and then the laser reaches the fifth coupler 311.

[0065] It can be understood that the first coupler 2 and the electro-optical modulator 3102 are connected by an optical path, the electro-optical modulator 3102 and the fifth coupler 311 are connected by an optical path, the signal processing unit 11 and the electro-optical modulator driving circuit are connected by an electrical connection, and the electro-optical modulator driving circuit 3101 and the electro-optical modulator 3102 are connected by an electrical connection.

[0066] Optionally, the electro-optical modulator driving circuit 3101 is a linear sweep frequency circuit.

[0067] In specific implementation, the electro-optical modulator driving circuit 3101 is a linear sweep frequency circuit, which can modulate the laser into a linear sweep frequency laser by driving the electro-optical modulator 3102, and the bandwidth of the sweep frequency is controlled and set by the signal processing unit 11.

[0068] Optionally, the OFDR module 3 further comprises a first erbium-doped fiber amplifier 312, the first output end of the fifth coupler 311 is connected to the input end of the first erbium-doped fiber amplifier 312, and the output end of the first erbium-doped fiber amplifier 312 is connected to the first input end of the signal switching module 5.

[0069] In specific implementation, the signal light output from the fifth coupler 311 enters the first erbium-doped fiber amplifier 312, the first erbium-doped fiber amplifier 312 amplifies the incoming signal light, so that the signal light can better propagate into the circulator 6.

[0070] It can be understood that the fifth coupler 311 and the first erbium-doped fiber amplifier are connected by an optical path, and the first erbium-doped fiber amplifier 312 and the signal switching module 5 are connected by an optical path.

[0071] Optionally, as shown in FIG. 1, the OFDR module 3 further comprises a second erbium-doped fiber amplifier 313, the second input end of the signal switching module 5 is connected to the input end of the second erbium-doped fiber amplifier 313, and the output end of the second erbium-doped fiber amplifier 313 is connected to the input end of the second coupler 4.Figure 3 As shown, the DAS module 4 includes a sixth coupler 410, an acousto-optic modulation circuit 411;

[0072] The second output end of the first coupler 2 is connected to the input end of the sixth coupler 410, the first output end of the sixth coupler 410 is connected to the first input end of the acousto-optic modulation circuit 411, the output end of the acousto-optic modulation circuit 411 is connected to the second input end of the signal switching module 5, and the second output end of the sixth coupler 410 is connected to the second input end of the first photoelectric conversion module; the third output end of the signal processing unit 11 is connected to the second input end of the acousto-optic modulation circuit 411.

[0073] In particular implementation, the laser entering the DAS module 4 is divided into two beams by the sixth coupler 410, one of which is used as the local light and directly enters the first photoelectric conversion module, and the other enters the acousto-optic modulation circuit 411 to obtain pulsed light, the pulsed light enters the signal switching module 5, then enters the circulator 6, and finally occurs Rayleigh scattering in the to-be-measured optical fiber 7 to generate Rayleigh scattering light, the generated Rayleigh scattering light is used as the sensing light and enters the second coupler 9 through the circulator 6, then enters the first photoelectric conversion module through the second coupler 9, and coherent interference occurs between the corresponding local light and the Rayleigh scattering light to obtain an electrical signal through photoelectric conversion, and the electrical signal passes through the signal acquisition unit 10 and the signal processing unit 11 to realize the DAS function.

[0074] It can be understood that the first coupler 2 and the sixth coupler 410, the sixth coupler 410 and the acousto-optic modulation circuit 411, the acousto-optic modulation circuit 411 and the signal switching module 5, and the sixth coupler 410 and the first photoelectric conversion module are all optically connected, and the signal processing unit 11 and the acousto-optic modulation circuit 411 are electrically connected.

[0075] Optionally, the acousto-optic modulation circuit 411 includes an acousto-optic modulator 4102 and an acousto-optic modulator driving circuit 4101; the first output end of the sixth coupler 410 is connected to the first input end of the acousto-optic modulator 4102, and the output end of the acousto-optic modulator 4102 is connected to the second input end of the signal switching module 5;

[0076] The third output end of the signal processing unit 11 is connected to the input end of the acousto-optic modulator driving circuit 4101, and the output end of the acousto-optic modulator driving circuit 4101 is connected to the second input end of the acousto-optic modulator 4102.

[0077] In particular implementation, the input end of the acousto-optic modulator drive circuit 4101 is connected with the third output end of the signal processing unit 11, the signal processing unit 11 sends a driving signal to the acousto-optic modulator drive circuit 4101, the acousto-optic modulator drive circuit 4101 drives the acousto-optic modulator 4102 according to the corresponding driving signal, so that the acousto-optic modulator 4102 converts the incoming laser into the pulse light, and finally inputs into the signal switching module 5.

[0078] It can be understood that the sixth coupler 410 and the acousto-optic modulator 4102, the acousto-optic modulator 4102 and the signal switching module 5 are optically connected, and the signal processing unit 11 and the acousto-optic modulator drive circuit 4101, the acousto-optic modulator drive circuit 4101 and the acousto-optic modulator 4102 are electrically connected.

[0079] Optionally, the DAS module 4 further comprises a second erbium-doped fiber amplifier 412; the output end of the acousto-optic modulation circuit 411 is connected with the input end of the second erbium-doped fiber amplifier 412, and the output end of the second erbium-doped fiber amplifier 412 is connected with the second input end of the signal switching module 5.

[0080] In a preferred embodiment, the output end of the acousto-optic modulator 4102 of the acousto-optic modulation circuit 411 is connected with the input end of the second erbium-doped fiber amplifier 412, and the output end of the second erbium-doped fiber amplifier 412 is connected with the second input end of the signal switching module 5.

[0081] It can be understood that the acousto-optic modulator 4102 of the acousto-optic modulation circuit 411 and the second erbium-doped fiber amplifier 412, the second erbium-doped fiber amplifier 412 and the signal switching module 5 are optically connected.

[0082] In particular implementation, the second erbium-doped fiber amplifier 412 performs optical signal amplification on the incoming pulse light, so that the pulse light can be better propagated into the circulator 6.

[0083] Optionally, the sensing system of the fusion of OFDR 3 and DAS 4 further comprises a third erbium-doped fiber amplifier 8; the third connection end of the circulator 6 is connected with the input end of the third erbium-doped fiber amplifier 8, and the output end of the third erbium-doped fiber amplifier 8 is connected with the input end of the second coupler 9.

[0084] In particular implementation, the third erbium-doped fiber amplifier 8 performs optical signal amplification on the incoming optical signal, so that the generated Rayleigh scattering light can be better propagated into the subsequent circuit for signal collection and processing.

[0085] It can be understood that the circulator 6 and the third erbium-doped fiber amplifier 8 are connected by an optical path, and the third erbium-doped fiber amplifier 8 and the second coupler 9 are connected by an optical path.

[0086] Optionally, the signal switching module 5 is an optical switch, and the connections of the optical switch with the OFDR module 3, the DAS module 4 and the circulator 6 are all optical path connections.

[0087] In specific implementation, the signal switching module 5 is an optical switch, and the function of the optical switch is to switch the OFDR module and the DAS module. A switching signal is generated by using a signal processing unit 11, and the optical switch is controlled to connect the OFDR module or the DAS module according to the switching signal, so that the OFDR module is connected when the OFDR function is needed, and the DAS module is connected when the DAS function is needed. The OFDR module and the DAS module are integrated by using an optical switch, so that the application has the OFDR function and the DAS function, and various measurements of the to-be-measured optical fiber 7 are realized, the diversity of detection is improved, and the cost of production is reduced.

[0088] Optionally, the first photoelectric conversion module includes a first photoelectric converter 21 and a third coupler 31; the first output end of the second coupler 9 is connected to the first input end of the third coupler 31, the second output end (i.e., the second output end of the sixth coupler 410) of the DAS module is connected to the second input end of the third coupler 31, the output end of the third coupler 31 is connected to the input end of the first photoelectric converter 32, and the output end of the first photoelectric converter 32 is connected to the first input end of the signal acquisition unit 10.

[0089] In specific implementation, when the signal switching module 5 connects the DAS module, Rayleigh scattering light generated by Rayleigh scattering in the to-be-measured optical fiber 7 enters the second coupler 9 through the circulator 6, the first output end of the second coupler 9 inputs the Rayleigh scattering light into the third coupler 31, and the second output end (i.e., the second output end of the sixth coupler 410) of the DAS module also inputs the local oscillator light into the third coupler 31, the two are coherently interfered, and then input into the first photoelectric converter 32, so that the corresponding optical signal is photoelectrically converted to obtain an electrical signal, the electrical signal is input into the signal acquisition unit 10 and the signal processing unit 11, and the DAS function is realized.

[0090] It can be understood that the second coupler 9 and the third coupler 31, the second output end (i.e., the second output end of the sixth coupler 410) of the DAS module and the third coupler 31, and the third coupler 31 and the first photoelectric converter 32 are all connected by an optical path, and the first photoelectric converter 32 and the signal acquisition unit are connected by an electrical connection.

[0091] Optionally, the second photoelectric conversion module comprises a second photoelectric converter 42 and a fourth coupler 41; the second output end of the second coupler 9 is connected to the first input end of the fourth coupler 41, the second output end of the OFDR module (i.e. the second output end of the fifth coupler) is connected to the second input end of the fourth coupler 41, the output end of the fourth coupler 41 is connected to the input end of the second photoelectric converter 42, and the output end of the second photoelectric converter 42 is connected to the second input end of the signal acquisition unit 10.

[0092] In particular implementation, when the signal switching module 5 is connected to the OFDR module, the Rayleigh scattering light generated by Rayleigh scattering in the to-be-detected optical fiber 7 enters the second coupler 9 through the circulator 6, the first output end of the second coupler 9 inputs the Rayleigh scattering light to the fourth coupler 41, the local oscillator light output by the second output end of the OFDR module (i.e. the second output end of the fifth coupler) also enters the fourth coupler 41, and the two are coherently interfered and then input to the second photoelectric converter 42, so that the corresponding optical signal is photoelectrically converted to obtain an electrical signal, the electrical signal is input to the signal acquisition unit 10 and the signal processing unit 11, and the OFDR function is realized.

[0093] It can be understood that the second coupler 9 and the fourth coupler 41, the second output end of the OFDR module (i.e. the second output end of the fifth coupler) and the fourth coupler 41, and the fourth coupler 41 and the second photoelectric converter 42 are all optically connected, and the second photoelectric converter 42 and the signal acquisition unit 10 are electrically connected.

[0094] Further, the utility model scheme content is explained, in this scheme, the narrow line width laser 1 emits laser into the first coupler 2, the first coupler 2 divides laser into two laser respectively, passes through OFDR module 3 and DAS module 4 respectively, passes through signal switching module 5, that is, optical switch makes any one optical signal that enters OFDR module 3 and DAS module 4 reach circulator 6 and then enter to-be-detected optical fiber 7 and occur Rayleigh scattering, if the laser that enters OFDR module 3 finally enters circulator 6, then it is the detection of OFDR function, if the laser that enters DAS module 4 finally enters circulator 6, then it is the detection of DAS function, and the sensing light that occurs Rayleigh scattering enters second coupler 9 again, and then meets corresponding local oscillator light again to complete detection through the specified structure.

[0095] The laser entering the OFDR module 3 is modulated as modulated light by the electro-optical modulation circuit 310, the modulated light is divided into two beams of laser by the fifth coupler 311, one beam is used as signal light, and the other beam is used as local light, the modulated signal light reaches the circulator 6, enters the to-be-measured optical fiber 7 through the circulator 6, Rayleigh scattering occurs in the to-be-measured optical fiber 7 and Rayleigh scattering light is generated, the generated Rayleigh scattering light is used as sensing light, enters the second coupler 9 through the circulator 6, and finally the light signal and the corresponding local light output through the second coupler 9 are subjected to coherent mixing in the fourth coupler 41, a beat frequency signal is generated, and by analyzing the frequency and intensity of the beat frequency signal, the scattering characteristics of different positions in the optical fiber can be determined, so that detection is realized.

[0096] The laser entering the DAS module 4 is divided into two beams of laser by the sixth coupler 410, one beam is used as local light and directly enters the third coupler 31, and the other beam of laser enters the acousto-optic modulation circuit 411 to obtain pulsed light, the pulsed light enters the signal switching module 5, then enters the circulator 6, finally Rayleigh scattering occurs in the to-be-measured optical fiber 7 and Rayleigh scattering light is generated, the generated Rayleigh scattering light is used as sensing light, enters the second coupler 9 through the circulator 6, then enters the third coupler 31 through the second coupler 9, and coherent interference with the corresponding local light is completed to realize detection, and the detection result is subjected to signal acquisition by the signal acquisition unit 10 and signal processing by the signal processing unit 11 to obtain the final detection result analysis.

[0097] Since the DAS is suitable for measuring long distances and is not high in spatial resolution, and the OFDR is suitable for short distances and is high in spatial resolution, the DAS can be used for rough measurement and the OFDR can be used for fine measurement according to actual detection requirements, high-precision measurement is realized, and the system can realize high-precision testing and long-distance testing.

[0098] Obviously, the above embodiments of the utility model are only examples for clearly illustrating the technical scheme of the utility model, and are not a limitation on the specific embodiments of the utility model. Any modification, equivalent replacement and improvement made within the spirit and principle of the utility model claim should be included in the protection scope of the utility model claim.

Claims

1. A sensing system that fuses OFDR and DAS, characterized in that, The sensing system comprises a narrow linewidth laser, a first coupler, an OFDR module, a DAS module, a signal switching module, a circulator, a second coupler, a first photoelectric conversion module, a second photoelectric conversion module, a signal acquisition unit and a signal processing unit. An output end of the narrow linewidth laser is connected to an input end of the first coupler, a first output end of the first coupler is connected to a first input end of the OFDR module, and a second output end of the first coupler is connected to a first input end of the DAS module. A first output end of the OFDR module is connected to a first input end of the signal switching module, a first output end of the DAS module is connected to a second input end of the signal switching module, and an output end of the signal switching module is connected to a first connecting end of the circulator. A second connecting end of the circulator is used for connecting a fiber to be measured, a third connecting end of the circulator is connected to an input end of the second coupler, a first output end of the second coupler is connected to a first input end of the first photoelectric conversion module, and a second output end of the second coupler is connected to a first input end of the second photoelectric conversion module. A second output end of the DAS module is connected to a second input end of the first photoelectric conversion module, and an output end of the first photoelectric conversion module is connected to a first input end of the signal acquisition unit. A second output end of the OFDR module is connected to a second input end of the second photoelectric conversion module, and an output end of the second photoelectric conversion module is connected to a second input end of the signal acquisition unit. An output end of the signal acquisition unit is connected to an input end of the signal processing unit, a first output end of the signal processing unit is connected to a third input end of the signal switching module, a second output end of the signal processing unit is connected to a second input end of the OFDR module, and a third output end of the signal processing unit is connected to a second input end of the DAS module.

2. The fusion OFDR and DAS sensing system of claim 1, wherein, The OFDR module comprises an electro-optical modulation circuit and a fifth coupler. A first output end of the first coupler is connected to a first input end of the electro-optical modulation circuit, an output end of the electro-optical modulation circuit is connected to an input end of the fifth coupler, a first output end of the fifth coupler is connected to a first input end of the signal switching module, a second output end of the fifth coupler is connected to a second input end of the second photoelectric conversion module, and a second output end of the signal processing unit is connected to a second input end of the electro-optical modulation circuit.

3. The fusion OFDR and DAS sensing system of claim 2, wherein, The electro-optical modulation circuit comprises an electro-optical modulator and an electro-optical modulator driving circuit. A first output end of the first coupler is connected to a first input end of the electro-optical modulator, an output end of the electro-optical modulator is connected to an input end of the fifth coupler, a second output end of the signal processing unit is connected to an input end of the electro-optical modulator driving circuit, and an output end of the electro-optical modulator driving circuit is connected to a second input end of the electro-optical modulator.

4. The fusion OFDR and DAS sensing system of claim 3, wherein, The electro-optical modulator driving circuit is a linear sweep circuit.

5. The fusion OFDR and DAS sensing system according to any one of claims 2-4, wherein, The OFDR module further comprises a first erbium-doped fiber amplifier; a first output end of the fifth coupler is connected to an input end of the first erbium-doped fiber amplifier, and an output end of the first erbium-doped fiber amplifier is connected to a first input end of the signal switching module.

6. The fusion OFDR and DAS sensing system according to any one of claims 1 to 4, wherein, The DAS module comprises a sixth coupler and an acousto-optic modulation circuit; a second output end of the first coupler is connected to an input end of the sixth coupler, a first output end of the sixth coupler is connected to a first input end of the acousto-optic modulation circuit, an output end of the acousto-optic modulation circuit is connected to a second input end of the signal switching module, a second output end of the sixth coupler is connected to a second input end of the first photoelectric conversion module; and a third output end of the signal processing unit is connected to a second input end of the acousto-optic modulation circuit.

7. The fusion OFDR and DAS sensing system of claim 6, wherein, The acousto-optic modulation circuit comprises an acousto-optic modulator and an acousto-optic modulator driving circuit; a first output end of the sixth coupler is connected to a first input end of the acousto-optic modulator, and an output end of the acousto-optic modulator is connected to a second input end of the signal switching module; a third output end of the signal processing unit is connected to an input end of the acousto-optic modulator driving circuit, and an output end of the acousto-optic modulator driving circuit is connected to a second input end of the acousto-optic modulator.

8. The fusion OFDR and DAS sensing system of claim 6, wherein, The DAS module further comprises a second erbium-doped fiber amplifier; an output end of the acousto-optic modulation circuit is connected to an input end of the second erbium-doped fiber amplifier, and an output end of the second erbium-doped fiber amplifier is connected to a second input end of the signal switching module.

9. The fusion OFDR and DAS sensing system according to any one of claims 1 to 4, wherein, Further comprising a third erbium-doped fiber amplifier; a third connection end of the circulator is connected to an input end of the third erbium-doped fiber amplifier, and an output end of the third erbium-doped fiber amplifier is connected to an input end of the second coupler.

10. The fusion OFDR and DAS sensing system according to any one of claims 1 to 4, wherein, The signal switching module is an optical switch; And / or, the first photoelectric conversion module comprises a first photoelectric converter and a third coupler; a first output end of the second coupler is connected to a first input end of the third coupler, a second output end of the DAS module is connected to a second input end of the third coupler, an output end of the third coupler is connected to an input end of the first photoelectric converter, and an output end of the first photoelectric converter is connected to a first input end of the signal acquisition unit; And / or, the second photoelectric conversion module comprises a second photoelectric converter and a fourth coupler; a second output end of the second coupler is connected to a first input end of the fourth coupler, a second output end of the OFDR module is connected to a second input end of the fourth coupler, an output end of the fourth coupler is connected to an input end of the second photoelectric converter, and an output end of the second photoelectric converter is connected to a second input end of the signal acquisition unit.

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