Optical frequency domain reflection system far-end sensing device and method without expansion module

Abstract

The invention relates to a far-end sensing device and method for an optical frequency domain reflection system, and belongs to the technical field of optical fiber sensing. According to the device, an optical fiber ring used for length matching is additionally arranged on a reference arm, meanwhile, a transmission optical fiber with the same length as the optical fiber ring is connected to an optical fiber output port of equipment, and the length of the transmission optical fiber is L6; the zero point of the arm length difference between the measuring arm and the reference arm is located at the middle point L6 / 2 of the transmission optical fiber, and the length of the arm length difference corresponding to the starting point of the sensing optical fiber is L6 / 2, that is, the transmission optical fiber with the length of L6 is realized by sacrificing the length of the original sensing optical fiber L6 / 2; although the length of the original sensing optical fiber L6 / 2 is sacrificed, the effect of adding the transmission optical fiber with the length of L6 between equipment and the sensing optical fiber is achieved, the application range of the optical frequency domain reflection system is expanded while the basic functions of the system are maintained, and the optical frequency domain reflection system is more suitable for application scenes with harsh environments and narrow spaces.

Description

Technical Field

[0001] This invention relates to a remote sensing device and method for an optical frequency domain reflection system, and particularly to a remote sensing device and method for an optical frequency domain reflection system without an extension module, belonging to the field of fiber optic sensing technology. Background Technology

[0002] Optical frequency domain reflection (OFDR) technology enables high spatial resolution fiber optic link testing and distributed fiber optic sensing. Based on heterodyne interferometry, the measurement length depends on the linewidth of the swept laser. OFDR systems typically place the zero-arm length difference position at the fiber optic output port of the device, with the sensing fiber connected to the output port, generally achieving measurement distances from tens to hundreds of meters. However, in practical engineering measurements, a transmission fiber is often needed between the sensing fiber and the device, occupying a portion of the sensing fiber's length and shortening the usable length. To address this issue, Zhang Xiaolei et al. proposed a remote transmission device including an extension module. The transmission fiber connects the device host and the extension module, while the sensing fiber connects to the extension module's output interface (Zhang Xiaolei, A Device and Method for Remote Sensing in Optical Frequency Domain Reflectometry, ZL201910688210.7). However, in practical engineering measurements, the extension module is difficult to install on the structure where the sensing fiber is laid, further complicating practical applications, especially in harsh environments and confined spaces. Summary of the Invention

[0003] The technical problem solved by this invention is to address the shortcomings of existing remote sensing schemes for optical frequency domain reflection systems. This invention proposes a remote sensing device and method for an optical frequency domain reflection system without an extension module. The device adds a fiber optic loop for length matching to the reference arm, and simultaneously connects a transmission fiber of equal length to the fiber optic loop to the fiber optic output port of the device. L 6. Ensure that the zero point of the arm length difference between the measuring arm and the reference arm is located at the midpoint of the transmission optical fiber. L At position 6 / 2, the length difference between the starting point of the sensing fiber and the arm length is... L 6 / 2, meaning by sacrificing the original sensing fiber L A length of 6 / 2, to achieve L A 6-length transmission fiber.

[0004] The technical solution provided by this invention is as follows: A remote sensing device for an optical frequency domain reflective system without an extension module includes a semiconductor tunable laser, a first fiber coupler, a second fiber coupler, a fiber circulator, a fiber ring, a balanced photodetector, a data acquisition and processing module, and a connecting fiber, wherein the connecting fiber includes a transmission fiber and a sensing fiber. The laser output from the semiconductor tunable laser is split into two paths by the first fiber coupler, referred to as the first laser path and the second laser path, respectively. The first laser beam enters the measuring arm, specifically the first output port of the first fiber coupler outputs the first laser beam, which enters the sensing fiber through the fiber circulator and the transmission fiber. The back Rayleigh scattered light from the sensing fiber enters the second fiber coupler through the transmission fiber and the fiber circulator. The second laser enters the reference arm, specifically the second laser output from the second output port of the first fiber coupler enters the second fiber coupler through the fiber ring; the two input lasers of the second fiber coupler form a beat frequency interference signal, which enters the balanced photodetector (6) through the two output ports; the balanced photodetector performs photoelectric conversion on the beat frequency interference signal and outputs it to the data acquisition and processing module; The data acquisition and processing module processes the beat frequency interference signal after photoelectric conversion to obtain the backscattered signal of the sensing fiber; The length of the fiber optic ring L 5. Length of the transmission fiber L 6. Satisfy: .

[0005] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the first fiber coupler includes a first input port, a first output port, and a second output port, with fiber lengths of respectively for each port. L 21 , L 22 , L 23 The second fiber optic coupler includes a first input port, a second input port, a first output port, and a second output port, with fiber lengths of [missing information]. L 31 , L 32 , L 33 , L 34 The fiber optic circulator includes a first port, a second port, and a third port, with fiber lengths of [missing information]. L 41 , L 42 , L 43 ,satisfy: .

[0006] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the measuring arm includes the first output port optical fiber of the first optical fiber coupler; the first port optical fiber, the second port optical fiber, and the third port optical fiber of the optical fiber circulator; the connecting optical fiber; and the first input port optical fiber of the second optical fiber coupler.

[0007] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the reference arm includes the second output port optical fiber of the first optical fiber coupler, an optical fiber ring, and the second input port optical fiber of the second optical fiber coupler.

[0008] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the data acquisition and processing module is for data larger than... L The signal from the connecting fiber in section 6 / 2 is demodulated by the optical frequency domain reflection system to obtain the backscattered signal from the sensing fiber.

[0009] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the data acquisition and processing module processes the beat frequency interference signal after photoelectric conversion to obtain the backscattered signal of the sensing fiber, including: (1) Obtain the beat frequency signal measured by the optical frequency domain reflection system based on the beat frequency interference signal after photoelectric conversion. I ( t ); (2) Beat frequency signal I ( t Perform an FFT to obtain the spectrum signal. I ( n b Based on the length matching relationship between the measuring arm and the reference arm, the beat frequency... n b The zero point corresponds to the L6 / 2 position of the connecting optical fiber, thus obtaining the beat frequency. n b With connection fiber length L Relationship; (3) Due to I ( n b )and I (- n b The corresponding connecting optical fibers overlap in the spectrum. L 6 / 2~0 and 0~ L 6 / 2 overlaps on the spectral signal, defined as - L 6 / 2~ L 6 / 2 is used as the transmission fiber, and the connecting fiber is larger than L At 6 / 2, I ( n b No negative frequency signal, defined as greater than L6 / 2 of the fiber is used as the sensing fiber; (4) For those greater than L The signal from the connecting fiber in section 6 / 2 is demodulated by the optical frequency domain reflection system to obtain the backscattered signal from the sensing fiber.

[0010] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the beat frequency signal in step (1) I ( t ) is represented as:

[0011] in, n b Beat frequency, t Sampling time.

[0012] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the beat frequency in step (2) n b With connection fiber length L The relationship is:

[0013] in, z The difference in length between the reference arm and the measuring arm. c The laser sweep rate, c denoted as the sensing rate of light in a vacuum.

[0014] In the aforementioned remote sensing device of the optical frequency domain reflection system without an extension module, the sensing rate of light in vacuum c The value is 3×10 8 m / s.

[0015] A remote sensing method for an optical frequency domain reflection system without an extension module, applied to the aforementioned sensing device, includes: The output laser of the semiconductor tunable laser is split into two paths by the first fiber coupler, referred to as the first laser path and the second laser path, respectively. The first output port of the first fiber coupler outputs a first laser beam that passes through the fiber circulator and the transmission fiber to enter the sensing fiber. The back Rayleigh scattered light from the sensing fiber passes through the transmission fiber and the fiber circulator to enter the second fiber coupler. The second output port of the first fiber coupler outputs a second laser beam, which enters the second fiber coupler through the fiber optic loop. The two input lasers of the second fiber coupler form a beat frequency interference signal, which enters the balanced photodetector through the two output ports. The balanced photodetector performs photoelectric conversion on the beat frequency interference signal and outputs it to the data acquisition and processing module. The data acquisition and processing module processes the beat frequency interference signal after photoelectric conversion to obtain the backscattered signal of the sensing fiber; The length of the fiber optic ring L 5. Length of the transmission fiber L 6. Satisfy: .

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention provides a remote sensing device and method for an optical frequency domain reflection system without an extension module. The device adds a fiber optic loop for length matching to the reference arm, and connects a transmission fiber of equal length to the fiber optic loop to the fiber optic output port of the device. The length of the transmission fiber is... L 6. Ensure that the zero point of the arm length difference between the measuring arm and the reference arm is located at the midpoint of the transmission optical fiber. L At position 6 / 2, the length difference between the starting point of the sensing fiber and the arm length is... L 6 / 2, meaning by sacrificing the original sensing fiber L A length of 6 / 2, to achieve L A 6-length transmission fiber.

[0017] (2) This invention provides a remote sensing device and method for an optical frequency domain reflection system without an extension module. By matching the arm length difference between the optical path measurement arm and the reference arm of the optical frequency domain reflection system, the zero point of the arm length difference is moved to the midpoint of the transmission optical fiber, although the original sensing optical fiber is sacrificed. L It has a length of 6 / 2, but it achieves the goal of increasing the length between the device and the sensing fiber by [missing information]. L The effect of 6-speed transmission fiber, this compromise solution expands the application range of optical frequency domain reflection system while maintaining the basic functions of the system, and is more suitable for application scenarios with harsh environment and limited space; (3) The present invention provides a remote sensing device and method for an optical frequency domain reflection system without an extension module. In the existing optical frequency domain reflection system architecture, by matching the arm length difference between the optical path measurement arm and the reference arm of the optical frequency domain reflection system, a transmission fiber is directly added between the demodulator of the optical frequency domain reflection system and the sensing fiber, without the need for an additional remote optical module, which simplifies the system structure and reduces cost and complexity. Attached Figure Description

[0018] Figure 1 A schematic diagram of a remote sensing device for an optical frequency domain reflection system without an extension module provided in an embodiment of the present invention; Figure 2 This invention provides a spectrum signal obtained by demodulating a remote sensing device in an optical frequency domain reflection system without an extension module, as provided in an embodiment of the invention. 1-Semiconductor tunable laser, 2-First fiber coupler, 3-Second fiber coupler, 4-Fiber circulator, 5-Fiber ring, 6-Balanced photodetector, 7-Data acquisition and processing module, 8-Connecting fiber, 81-Transmission fiber, 82-Sensing fiber. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments: This invention discloses a remote sensing device for an optical frequency domain reflection system without an extension module, such as... Figure 1 As shown, it includes a semiconductor tunable laser 1, a first fiber coupler 2, a second fiber coupler 3, a fiber optic circulator 4, a fiber optic ring 5, a balanced photodetector 6, a data acquisition and processing module 7, and a connecting fiber 8, wherein the connecting fiber includes a transmission fiber 81 and a sensing fiber 82.

[0020] The laser output from the semiconductor tunable laser 1 is split into two paths by the first fiber coupler 2, referred to as the first laser path and the second laser path, respectively.

[0021] The first laser beam enters the measuring arm. Specifically, the laser beam output from the first output port of the first fiber coupler 2 enters the sensing fiber 82 through the fiber circulator 4 and the transmission fiber 81. The backscattered Rayleigh light from the sensing fiber 82 enters the second fiber coupler 3 through the transmission fiber 81 and the fiber circulator 4. The second laser enters the reference arm, specifically the laser output from the second output port of the first fiber coupler 2 enters the second fiber coupler 3 through the fiber ring 5; the two input lasers of the second fiber coupler 3 form a beat frequency interference signal, which enters the balanced photodetector 6 through the two output ports; The balanced photodetector 6 performs photoelectric conversion on the beat frequency interference signal of the fiber optic measurement module and outputs it to the data acquisition and processing module 7; The data acquisition and processing module 7 processes the beat frequency interference signal after photoelectric conversion to obtain the backscattering signal of the sensing fiber 82.

[0022] In this embodiment of the invention, the first fiber optic coupler 2 includes a first input port, a first output port, and a second output port, with fiber lengths of respectively for each port. L 21 , L 22 , L 23 The second fiber optic coupler 3 includes a first input port, a second input port, a first output port, and a second output port, with fiber lengths of respectively for each port. L 31 , L32 , L 33 , L 34 The fiber optic circulator 4 includes a first port, a second port, and a third port, with fiber lengths of [missing information]. L 41 , L 42 , L 43 ,satisfy: .

[0023] In this embodiment of the invention, the length of the fiber optic ring 5 is... L 5; The length of the transmission fiber optic cable 81 is L 6. Satisfies:

[0024] In this embodiment of the invention, the measuring arm includes a first output port optical fiber of a first optical fiber coupler 2; a first port optical fiber, a second port optical fiber, and a third port optical fiber of an optical fiber circulator 4; a connecting optical fiber 8; and a first input port optical fiber of a second optical fiber coupler 3.

[0025] In this embodiment of the invention, the reference arm includes the second output port fiber of the first fiber coupler 2, the fiber ring 5, and the second input port fiber of the second fiber coupler 3.

[0026] The data acquisition and processing module 7 processes the beat frequency interference signal after photoelectric conversion to obtain the backscattered signal of the sensing fiber 82, specifically including the following steps: (1) Obtain the beat frequency signal measured by the optical frequency domain reflection system based on the beat frequency interference signal after photoelectric conversion. I ( t ), represented as:

[0027] in, n b Beat frequency, t Sampling time.

[0028] (2) Beat frequency signal I ( t Perform an FFT to obtain its spectral signal. I ( n b Based on the matching relationship between the measuring arm and the reference arm, the beat frequency... n b Point 0 corresponds to position L6 / 2 of fiber optic cable 8, beat frequency. n b With connecting fiber optic cable length 8L The relationship is:

[0029] in, z The difference in length between the reference arm and the measuring arm. c The laser sweep rate, c The sensing rate of light in a vacuum is 3 × 10⁻⁶. 8 m / s.

[0030] (3) Due to I ( n b )and I (- n b The corresponding connecting optical fibers overlap in the spectrum. L 6 / 2~0 and 0~ L 6 / 2 overlaps on the spectral signal, defined as - L 6 / 2~ L 6 / 2 serves as the transmission fiber 81, and the connecting fiber 8 is greater than L At 6 / 2, I ( n b No negative frequency signal, defined as greater than L 6 / 2 of the fiber is used as sensing fiber 82.

[0031] (4) For those greater than L The signal from the connecting fiber 8 in section 6 / 2 is demodulated by the optical frequency domain reflection system to obtain the backscattered signal from the sensing fiber 82.

[0032] like Figure 2 The image shows the spectral signal demodulated by a remote sensing device in an optical frequency domain reflection system without an extension module, according to an embodiment of the present invention.

[0033] This invention also provides a remote sensing method for an optical frequency domain reflection system without an extension module, specifically including the following steps: (a) The output laser of the semiconductor tunable laser 1 is split into two paths by the first fiber coupler 2, which are referred to as the first laser path and the second laser path, respectively. (ii) The first output port of the first fiber coupler 2 outputs the first laser beam, which enters the sensing fiber 82 through the fiber circulator 4 and the transmission fiber 81. The back Rayleigh scattered light of the sensing fiber 82 enters the second fiber coupler 3 through the transmission fiber 81 and the fiber circulator 4. (iii) The second laser output from the second output port of the first fiber coupler 2 enters the second fiber coupler 3 through the fiber ring 5; (iv) The two input lasers of the second fiber coupler 3 form a beat frequency interference signal, which enters the balanced photodetector 6 through the two output ports; (v) The balanced photodetector 6 performs photoelectric conversion on the beat frequency interference signal and outputs it to the data acquisition and processing module 7; (vi) The data acquisition and processing module 7 processes the beat frequency interference signal after photoelectric conversion to obtain the backscattered signal of the sensing fiber 82. The specific method includes the following steps: (6.1) Obtain the beat frequency signal measured by the optical frequency domain reflection system based on the beat frequency interference signal after photoelectric conversion. I ( t ), represented as:

[0034] in, n b Beat frequency, t Sampling time.

[0035] (6.2) Beat frequency signal I ( t Perform an FFT to obtain its spectral signal. I ( n b Based on the matching relationship between the measuring arm and the reference arm, the beat frequency... n b Point 0 corresponds to position L6 / 2 of fiber optic cable 8, beat frequency. n b With connecting fiber optic cable length 8 L The relationship is:

[0036] in, z The difference in length between the reference arm and the measuring arm. c The laser sweep rate, c The sensing rate of light in a vacuum is 3 × 10⁻⁶. 8 m / s.

[0037] (6.3) Due to I ( n b )and I (- n b The corresponding connecting optical fibers overlap in the spectrum. L 6 / 2~0 and 0~ L 6 / 2 overlaps on the spectral signal, defined as - L 6 / 2~ L 6 / 2 serves as the transmission fiber 81, and the connecting fiber 8 is greater than L At 6 / 2,I ( n b No negative frequency signal, defined as greater than L 6 / 2 of the fiber is used as sensing fiber 82.

[0038] (6.4) For those greater than L The signal from the connecting fiber 8 in section 6 / 2 is demodulated by the optical frequency domain reflection system to obtain the backscattered signal from the sensing fiber 82.

[0039] This invention moves the zero point of the arm length difference to the midpoint of the transmission fiber by matching the arm length difference between the measurement arm and the reference arm of the optical path in the optical frequency domain reflection system, although sacrificing the original sensing fiber. L It has a length of 6 / 2, but it achieves the goal of increasing the length between the device and the sensing fiber by [missing information]. L The 6-inch transmission fiber eliminates the need for additional remote optical modules, making it more suitable for applications in harsh environments and confined spaces.

[0040] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0041] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A remote sensing device for an optical frequency domain reflection system without an extension module, characterized in that, It includes a semiconductor tunable laser (1), a first fiber coupler (2), a second fiber coupler (3), a fiber circulator (4), a fiber ring (5), a balanced photodetector (6), a data acquisition and processing module (7), and a connecting fiber (8), wherein the connecting fiber includes a transmission fiber (81) and a sensing fiber (82). The laser output from the semiconductor tunable laser (1) is split into two paths by the first fiber coupler (2), which are referred to as the first laser and the second laser, respectively. The first laser enters the measuring arm, specifically the first output port of the first fiber coupler (2) outputs the first laser through the fiber circulator (4) and the transmission fiber (81) into the sensing fiber (82), and the back Rayleigh scattered light of the sensing fiber (82) enters the second fiber coupler (3) through the transmission fiber (81) and the fiber circulator (4). The second laser enters the reference arm, specifically the second output port of the first fiber coupler (2) outputs the second laser and enters the second fiber coupler (3) through the fiber ring (5); the two input lasers of the second fiber coupler (3) form a beat frequency interference signal, which enters the balanced photodetector (6) through the two output ports; the balanced photodetector (6) performs photoelectric conversion on the beat frequency interference signal and outputs it to the data acquisition and processing module (7). The data acquisition and processing module (7) processes the beat frequency interference signal after photoelectric conversion to obtain the backscattering signal of the sensing fiber (82); The length of the fiber optic ring (5) L 5. Length of transmission optical fiber (81) L 6. Satisfy: .

2. The remote sensing device for the optical frequency domain reflection system without an extension module according to claim 1, characterized in that, The first fiber optic coupler (2) includes a first input port, a first output port, and a second output port, with fiber lengths of respectively for each port. L 21 , L 22 , L 23 The second fiber optic coupler (3) includes a first input port, a second input port, a first output port, and a second output port, with fiber lengths of respectively for each port. L 31 , L 32 , L 33 , L 34 The fiber optic circulator (4) includes a first port, a second port, and a third port, with fiber lengths of respectively for each port. L 41 , L 42 , L 43 ,satisfy: 。 3. The remote sensing device for the optical frequency domain reflection system without an extension module according to claim 1, characterized in that, The measuring arm includes the first output port fiber of the first fiber coupler (2); the first port fiber, the second port fiber and the third port fiber of the fiber circulator (4); the connecting fiber (8); and the first input port fiber of the second fiber coupler (3).

4. The remote sensing device for an optical frequency domain reflection system without an extension module according to claim 1, characterized in that, The reference arm includes the second output port fiber of the first fiber coupler (2), the fiber ring (5), and the second input port fiber of the second fiber coupler (3).

5. The remote sensing device for an optical frequency domain reflection system without an extension module according to claim 1, characterized in that, The data acquisition and processing module (7) is for data larger than L The signal of the connecting fiber (8) in part 6 / 2 is demodulated by the optical frequency domain reflection system to obtain the backscattered signal of the sensing fiber (82).

6. The remote sensing device for an optical frequency domain reflection system without an extension module according to claim 1, characterized in that, The data acquisition and processing module (7) processes the beat frequency interference signal after photoelectric conversion to obtain the backscattered signal of the sensing fiber (82), including: (1) Obtain the beat frequency signal measured by the optical frequency domain reflection system based on the beat frequency interference signal after photoelectric conversion. I ( t ); (2) Beat frequency signal I ( t Perform an FFT to obtain the spectrum signal. I ( ν b Based on the length matching relationship between the measuring arm and the reference arm, the beat frequency... ν b The 0 point corresponds to the L6 / 2 position of the connecting optical fiber (8), and the beat frequency is obtained. ν b Length of connecting optical fiber (8) L Relationship; (3) Due to I ( ν b )and I (- ν b The corresponding connecting fibers (8) overlap in the spectrum. L 6 / 2~0 and 0~ L 6 / 2 overlaps on the spectral signal, defined as - L 6 / 2~ L 6 / 2 is used as the transmission fiber (81), and the connecting fiber (8) is greater than L At 6 / 2, I ( ν b No negative frequency signal, defined as greater than L 6 / 2 of the portion is used as the sensing fiber (82); (4) For those greater than L The signal of the connecting fiber (8) in part 6 / 2 is demodulated by the optical frequency domain reflection system to obtain the backscattered signal of the sensing fiber (82).

7. The remote sensing device for an optical frequency domain reflection system without an extension module according to claim 6, characterized in that, In step (1), the beat frequency signal I ( t ) is represented as: in, ν b Beat frequency, t Sampling time.

8. The remote sensing device for an optical frequency domain reflection system without an extension module according to claim 6, characterized in that, The beat frequency in step (2) ν b Length of connecting optical fiber (8) L The relationship is: in, z The difference in length between the reference arm and the measuring arm. γ The laser sweep rate, c denoted as the sensing rate of light in a vacuum.

9. The remote sensing device for an optical frequency domain reflection system without an extension module according to claim 8, characterized in that, Sensing rate of light in a vacuum c The value is 3×10 8 m / s.

10. A remote sensing method for an optical frequency domain reflection system without an extension module, characterized in that, The sensing device according to any one of claims 1 to 9 comprises: The output laser of the semiconductor tunable laser (1) is split into two paths by the first fiber coupler (2), which are referred to as the first laser and the second laser respectively. The first output port of the first fiber coupler (2) outputs the first laser beam, which enters the sensing fiber (82) through the fiber circulator (4) and the transmission fiber (81). The back Rayleigh scattered light of the sensing fiber (82) enters the second fiber coupler (3) through the transmission fiber (81) and the fiber circulator (4). The second output port of the first fiber coupler (2) outputs a second laser beam that enters the second fiber coupler (3) through the fiber ring (5); The two input lasers of the second fiber coupler (3) form a beat frequency interference signal, which enters the balanced photodetector (6) through the two output ports. The balanced photodetector (6) performs photoelectric conversion on the beat frequency interference signal and outputs it to the data acquisition and processing module (7). The data acquisition and processing module (7) processes the beat frequency interference signal after photoelectric conversion to obtain the backscattering signal of the sensing fiber (82); The length of the fiber optic ring (5) L 5. Length of transmission optical fiber (81) L 6. Satisfy: .

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