A narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system and method

Abstract

The present invention discloses a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system and method, the system includes an optical fiber line part, an optical emission part, an optical processing part and a terminal part; the output end of the optical emission part is parallel to the output end of the optical processing part, and the distance from the output end of the optical emission part to the terminal part is equal to the distance from the output end of the optical processing part to the terminal part; the optical fiber line part includes a long-distance vibration optical fiber and a positioning optical fiber; the refractive index of the long-distance vibration optical fiber and the positioning optical fiber is the same; the optical emission part is used to input two light sources with specified narrow linewidth values ​​and specified low frequency values ​​to the terminal part through the long-distance vibration optical fiber; the optical processing part is used to input one light source with specified narrow linewidth values ​​and specified low frequency values ​​to the terminal part through the positioning optical fiber. The present invention can achieve 100-meter coherent positioning.

Description

Technical Field

[0001] The present invention relates to the field of coherent positioning technology, and more specifically, to a narrow-linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system and method. Background Art

[0002] The basic working principle of fiber optic vibration sensing positioning is to couple the optical signal from the laser into the optical fiber. The optical fiber is affected by the light in the disturbed area, which changes the measured parameters. The optical properties of the light (such as light intensity, wavelength, frequency, phase, polarization state, etc.) change and become a modulated signal source. After being sent to the optical detector through the optical fiber, the measured parameters are obtained after demodulation. Generally, bidirectional PD is used to extract the parameters of intensity change over time, that is, the time difference to reach the maximum intensity, and then the time difference is multiplied by the speed of light to obtain the distance information of the event.

[0003] The lasers used for optical fiber vibration sensing positioning are mainly used in the following ways:

[0004] Distributed Feedback Laser (DFB laser for short), Externally Modulated Laser (EML laser for short) and Fiber Laser (FL laser for short) are the main three types, and other lasers are rarely used.

[0005] DFB lasers are cheap and easy to produce. The biggest feature of DFB lasers is that they have very good monochromaticity. Their spectral width is generally within 10nm, and they have a very high side mode suppression ratio. In addition, the wavelengths they emit, 1310nm and 1550nm, are both communication wavelengths, and the transmission loss in optical fibers is low, making them very suitable for long-distance transmission.

[0006] An externally modulated laser adds a modulator module outside the laser to change the parameters of the output laser, such as intensity and frequency. When the laser output power is constant, the higher the modulation frequency, the weaker the output light intensity. Under the condition of a certain fiber loss, the shorter the detection distance and the higher the positioning accuracy. Conversely, the stronger the light intensity, the lower the positioning accuracy. The entire external modulation is more expensive, which adds additional costs and also increases the space occupied.

[0007] Fiber lasers refer to lasers that use rare earth-doped glass optical fibers as gain media, but their spectrum is relatively wide, and most of the output wavelengths of 1064nm are for industrial use, which is not suitable for vibration sensing.

[0008] However, in pursuit of low cost, environmental adaptability and efficient early warning, the use of DFB lasers has high environmental requirements and requires a stable temperature of 25 degrees Celsius. Therefore, it is not practical in the field where the temperature difference is large; the use of externally modulated lasers will inevitably increase additional costs; the use of fiber lasers cannot meet the requirements of efficient early warning. Therefore, the existing technology cannot meet the existing needs of low cost, strong environmental adaptability and efficient early warning.

[0009] Most of the existing optical positioning methods use Mach-Zehnder (MZ) interferometry technology, which has the characteristics of high response sensitivity and response frequency from a few hertz to megahertz. Therefore, it uses two-way delay difference to demodulate the signal for positioning, so it is widely used in the detection and positioning of distributed vibration sensor modules. As for the two-way delay difference for signal demodulation positioning, there are few two-way depolarization technology to remove noise and improve accuracy. This is because the light after interference from the distributed vibration sensor equipment is divided into DC and AC parts. The AC part contains time-related information, so it is difficult to process and cannot achieve 100-meter coherent positioning. Summary of the invention

[0010] The purpose of the present invention is to provide a narrow-linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system and method, which solves the problem that the background technology cannot meet the existing needs of low cost, strong environmental adaptability and high-efficiency early warning. The use of narrow-linewidth polarization-maintaining laser is not only conducive to bidirectional depolarization and noise reduction, but also can increase the signal-to-noise ratio, which is more conducive to rapid and accurate positioning, and can achieve 100-meter bidirectional noise reduction and rapid coherent positioning.

[0011] In order to achieve the above-mentioned purpose, a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system is provided, which includes an optical fiber line part, an optical transmission part, an optical processing part and a terminal part;

[0012] The output end of the light emitting part and the output end of the light processing part are parallel to each other, and the distance from the output end of the light emitting part to the terminal part is equal to the distance from the output end of the light processing part to the terminal part;

[0013] The optical fiber line part includes a long-distance vibration optical fiber and a positioning optical fiber; the long-distance vibration optical fiber is composed of two vibration optical fibers that are parallel to each other and have the same length, and is used to sense the vibration signal of a certain point on the vibration optical fiber; the two ends of the long-distance vibration optical fiber are respectively connected to the light emitting part and the terminal part; the two ends of the positioning optical fiber are respectively connected to the light processing part and the terminal part; the refractive index of the long-distance vibration optical fiber and the positioning optical fiber is the same;

[0014] The light emitting part is used to input two light sources with specified narrow line width values ​​and specified low frequency values ​​to the terminal part through a long-distance vibration optical fiber, and the two light sources form a mixed light with a small difference frequency, and the mixed light has strong coherence; the light emitting part is also used to obtain the optical path of the light emitted by the terminal part from the point of the vibration signal to the light emitting part;

[0015] The terminal part is used to receive the light of the light emitting part through the long-distance vibration optical fiber to interfere with the light to form a path of interference light with a specified narrow line width value and a specified low frequency value, and then input it to the light processing part; the terminal part is used to receive the light emitted by the light processing part through the positioning optical fiber to interfere with the light to form two paths of interference light with a specified narrow line width value and a specified low frequency value, and then input it to the light emitting part;

[0016] The optical processing part is used to input a light source with a specified narrow line width value and a specified low frequency value to the terminal part through the positioning optical fiber; the optical processing part is also used to obtain the optical path of the light emitted by the light emitting part from the point of the vibration signal to the optical processing part.

[0017] In particular, the light emitting part includes a first demodulation module, a first photoelectric conversion module, a first polarization-maintaining interferometer and a first narrow linewidth polarization-maintaining light source; the first photoelectric conversion module is used to convert the optical signal into an electrical signal, and then output it to the demodulation module; the first demodulation module is used to demodulate, analyze and extract the vibration signal.

[0018] In particular, the optical processing part includes a second demodulation module, a second photoelectric conversion module, a second narrow linewidth polarization-maintaining light source, and a circulator; the circulator is used to isolate the crosstalk of light transmitted in different directions in the optical path; the second demodulation module is used to demodulate, analyze and extract the vibration signal.

[0019] Particularly, the first narrow linewidth polarization-maintaining light source adopts a drift laser.

[0020] Particularly, the second narrow linewidth polarization-maintaining light source adopts a drift laser.

[0021] Particularly, the terminal part includes a second polarization-maintaining interferometer and a polarization combiner.

[0022] Particularly, the terminal part is installed in a terminal box.

[0023] The positioning method using the above narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system includes the following steps:

[0024] (1) The light emitting part inputs two light sources with specified narrow line width and specified low frequency to the terminal part through a long-distance vibrating optical fiber, and the two light sources form a mixed light with a small difference frequency, and the mixed light has strong coherence; the light processing part inputs one light source with specified narrow line width and specified low frequency to the terminal part through a positioning optical fiber;

[0025] (2) Measure the distance between the output end of the light emitting part and the light processing part as L;

[0026] (3) Obtaining the refractive index n of the long-distance vibration optical fiber and the positioning optical fiber;

[0027] (4) When an intrusion event acts on the long-distance vibration optical fiber, the long-distance vibration optical fiber senses a vibration signal at a certain point; the terminal part receives the light from the light emitting part through the long-distance vibration optical fiber, interferes to form a path of interference light with a specified narrow line width value and a specified low frequency value, and then inputs it to the light processing part; the terminal part receives the light emitted by the light processing part through the positioning optical fiber, interferes to form two paths of interference light with a specified narrow line width value and a specified low frequency value, and then inputs it to the light emitting part;

[0028] (5) The optical path of the light emitted by the optical processing part from the point of the vibration signal to the optical emitting part is nL1, and the time from the point of the vibration signal to the optical emitting part is t1; wherein L1 is set to be the physical distance from the point on the long-distance vibration optical fiber corresponding to the vibration signal to the optical emitting part;

[0029] (6) The optical path of the light emitted by the light emitting part from the point of the vibration signal to the light processing part obtained by the light processing part is n(L2+L), and the time from the point of the vibration signal to the light processing part is t2; wherein L2 is set to be the physical distance from the point on the long-distance vibration optical fiber corresponding to the vibration signal to the light processing part;

[0030] (7) The time delay between the bidirectional waveforms of the light emitted by the optical emitting part and the light emitted by the optical processing part is calculated by demodulation as dt=t2-t1;

[0031] (8) Based on the time delay dt=(nL+ nL2-nL1) / c=2n(L-L1) / c, the physical distance from the point on the long-distance vibrating optical fiber corresponding to the vibration signal to the light emitting part is calculated as L1=Lc*dt / 2n.

[0032] The beneficial effects of the present invention are as follows:

[0033] Vibration sensing and positioning requires light interference. The three important conditions for light interference are: consistent vibration direction, same frequency, and constant phase difference. The narrow linewidth polarization-maintaining laser itself outputs a very narrow light width, du≤500kHz, and the spectral line width is between one thousandth and one tenth of a nanometer, ensuring the same output frequency. The coherence length d=c / du, c is the speed of light, and du is the narrow line width. The coherence length is over 100 meters, which greatly improves the degree of light interference, thereby ensuring that the light interference phase difference over a large range is also constant, and indirectly improves the detection sensitivity. The output light itself is also polarization-maintaining, ensuring the consistency of the vibration direction. Even if the optical cable line is long and the line is squeezed to a certain extent, the vibration direction of the light changes slightly during its travel, which will greatly reduce the impact of polarization fading in the polarization-maintaining interferometer. This patent adopts the narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent technology. Due to the extrusion and deformation of the optical fiber, the direction of the polarized light changes slightly. After passing through the polarization-maintaining interferometer, the amplitude of the signal changes in the collected signals of the first photoelectric conversion module and the second photoelectric conversion module, so that the vibration information can be analyzed to achieve dual MZ positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 Schematic diagram of the working principle of the system according to the embodiment of the present invention. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0037] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0038] It should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, or are the orientation or positional relationship in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0039] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0040] like Figure 1 As shown, a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system according to an embodiment of the present invention includes an optical fiber line part, an optical emission part, an optical processing part and a terminal part.

[0041] The output end of the light emitting part and the output end of the light processing part are parallel to each other, and the distance from the output end of the light emitting part to the terminal part is equal to the distance from the output end of the light processing part to the terminal part;

[0042] The optical fiber line part includes a long-distance vibration optical fiber and a positioning optical fiber; the long-distance vibration optical fiber is composed of two vibration optical fibers that are parallel to each other and have the same length, and is used to sense the vibration signal of a certain point on the vibration optical fiber. The two ends of the long-distance vibration optical fiber are respectively connected to the light emitting part and the terminal part. The two ends of the positioning optical fiber are respectively connected to the light processing part and the terminal part. The refractive index of the long-distance vibration optical fiber and the positioning optical fiber is the same.

[0043] The light emitting part is used to input two light sources with specified narrow line width and specified low frequency to the terminal part through a long-distance vibration optical fiber. The two light sources form a mixed light with a small difference frequency, and the mixed light has strong coherence. The light emitting part is also used to obtain the optical path of the light emitted by the terminal part from the point of the vibration signal to the light emitting part.

[0044] The terminal part is used to receive the light emitted by the light emitting part through the long-distance vibrating optical fiber to interfere and form one interference light with a specified narrow line width value and a specified low frequency value, and then input it to the light processing part. The terminal part is used to receive the light emitted by the light processing part through the positioning optical fiber to interfere and form two interference lights with specified narrow line width values ​​and a specified low frequency value, and then input them to the light emitting part;

[0045] The optical processing part is used to input a light source with a specified narrow line width value and a specified low frequency value to the terminal part through the positioning optical fiber; the optical processing part is also used to obtain the optical path of the light emitted by the light emitting part from the point of the vibration signal to the optical processing part.

[0046] The optical emission part includes a first demodulation module, a first photoelectric conversion module PD1, a first polarization-maintaining interferometer and a first narrow-linewidth polarization-maintaining light source; the first photoelectric conversion module is used to convert the optical signal into an electrical signal, and then output it to the demodulation module; the first demodulation module is used to demodulate, analyze and extract the vibration signal.

[0047] The optical processing part includes a second demodulation module, a second photoelectric conversion module PD2, a second narrow linewidth polarization-maintaining light source, and a circulator; the circulator is used to isolate the crosstalk of light transmitted in different directions in the optical path; the second demodulation module is used to demodulate, analyze and extract the vibration signal.

[0048] The first narrow linewidth polarization-maintaining light source adopts a drift laser.

[0049] The second narrow linewidth polarization-maintaining light source adopts a drift laser.

[0050] The terminal part includes a second polarization-maintaining interferometer and a polarization combiner PBC.

[0051] The terminal part is installed in the terminal box.

[0052] The positioning method using the above narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system includes the following steps:

[0053] (1) The light emitting part inputs two light sources with specified narrow line width and specified low frequency to the terminal part through a long-distance vibrating optical fiber, and the two light sources form a mixed light with a small difference frequency, and the mixed light has strong coherence; the light processing part inputs one light source with specified narrow line width and specified low frequency to the terminal part through a positioning optical fiber;

[0054] (2) Measure the distance between the output end of the light emitting part and the light processing part as L;

[0055] (3) Obtaining the refractive index n of the long-distance vibration optical fiber and the positioning optical fiber;

[0056] (4) When an intrusion event acts on the long-distance vibration optical fiber, the long-distance vibration optical fiber senses a vibration signal at a certain point; the terminal part receives the light from the light emitting part through the long-distance vibration optical fiber, interferes to form a path of interference light with a specified narrow line width value and a specified low frequency value, and then inputs it to the light processing part; the terminal part receives the light emitted by the light processing part through the positioning optical fiber, interferes to form two paths of interference light with a specified narrow line width value and a specified low frequency value, and then inputs it to the light emitting part;

[0057] (5) The optical path of the light emitted by the optical processing part from the point of the vibration signal to the optical emitting part is nL1, and the time from the point of the vibration signal to the optical emitting part is t1; wherein L1 is set to be the physical distance from the point on the long-distance vibration optical fiber corresponding to the vibration signal to the optical emitting part;

[0058] To be precise, for the light from the second narrow linewidth polarization-maintaining light source, the optical path from the vibration signal point (external force excitation point) to the first polarization-maintaining interferometer is nL1, and the time is t1; wherein L1 is set as the physical distance from the point on the vibrating optical fiber corresponding to the vibration signal to the first polarization-maintaining interferometer.

[0059] (6) The optical path of the light emitted by the light emitting part from the point of the vibration signal to the light processing part obtained by the light processing part is n(L2+L), and the time from the point of the vibration signal to the light processing part is t2; wherein L2 is set to be the physical distance from the point on the long-distance vibration optical fiber corresponding to the vibration signal to the light processing part;

[0060] To be precise, for the light of the first narrow linewidth polarization-maintaining light source, the optical path from the vibration signal point (external force excitation point) to the circulator is n (L2+L), and the time is t2; wherein L2 is set as the physical distance from the point on the vibration optical fiber corresponding to the vibration signal to the second polarization-maintaining interferometer; and L is the total length.

[0061] (7) The time delay between the bidirectional waveforms of the light emitted by the optical emitting part and the light emitted by the optical processing part is calculated by demodulation as dt=t2-t1;

[0062] (8) Based on the time delay dt=(nL+ nL2-nL1) / c=2n(L-L1) / c, the physical distance from the point on the long-distance vibrating optical fiber corresponding to the vibration signal to the light emitting part is calculated as L1=Lc*dt / 2n.

[0063] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, the patent owner may make various variations or modifications within the scope of the appended claims. As long as they do not exceed the protection scope described in the claims of the present invention, they should be within the protection scope of the present invention.

Claims

1. A narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system, comprising an optical fiber line part, an optical transmission part, an optical processing part and a terminal part; characterized in that: The output end of the light emitting part and the output end of the light processing part are parallel to each other, and the distance from the output end of the light emitting part to the terminal part is equal to the distance from the output end of the light processing part to the terminal part; The optical fiber line part includes a long-distance vibration optical fiber and a positioning optical fiber; the long-distance vibration optical fiber is composed of two vibration optical fibers that are parallel to each other and have the same length, and is used to sense the vibration signal of a certain point on the vibration optical fiber; the two ends of the long-distance vibration optical fiber are respectively connected to the light emitting part and the terminal part; the two ends of the positioning optical fiber are respectively connected to the light processing part and the terminal part; the refractive index of the long-distance vibration optical fiber and the positioning optical fiber is the same; The light emitting part is used to input two light sources with specified narrow line width values ​​and specified low frequency values ​​to the terminal part through a long-distance vibration optical fiber, and the two light sources form a mixed light with a small difference frequency, and the mixed light has strong coherence; the light emitting part is also used to obtain the optical path of the light emitted by the terminal part from the point of the vibration signal to the light emitting part; The terminal part is used to receive the light of the light emitting part through the long-distance vibration optical fiber to interfere with the light to form a path of interference light with a specified narrow line width value and a specified low frequency value, and then input it to the light processing part; the terminal part is used to receive the light emitted by the light processing part through the positioning optical fiber to interfere with the light to form two paths of interference light with a specified narrow line width value and a specified low frequency value, and then input it to the light emitting part; The optical processing part is used to input a light source with a specified narrow line width value and a specified low frequency value to the terminal part through the positioning optical fiber; the optical processing part is also used to obtain the optical path of the light emitted by the light emitting part from the point of the vibration signal to the optical processing part.

2. According to claim 1, a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system is characterized by: The light emitting part includes a first demodulation module, a first photoelectric conversion module, a first polarization-maintaining interferometer and a first narrow-linewidth polarization-maintaining light source; the first photoelectric conversion module is used to convert the optical signal into an electrical signal, and then output it to the demodulation module; the first demodulation module is used to demodulate, analyze and extract the vibration signal.

3. According to claim 1, a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system is characterized by: The optical processing part includes a second demodulation module, a second photoelectric conversion module, a second narrow linewidth polarization-maintaining light source, and a circulator; the circulator is used to isolate the crosstalk of light transmitted in different directions in the optical path; the second demodulation module is used to demodulate, analyze and extract the vibration signal.

4. According to claim 2, a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system is characterized by: The first narrow linewidth polarization-maintaining light source adopts a drift laser.

5. According to claim 3, a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system is characterized by: The second narrow linewidth polarization-maintaining light source adopts a drift laser.

6. The narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system according to claim 1, characterized in that: The terminal part includes a second polarization-maintaining interferometer and a polarization combiner.

7. The narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system according to claim 1, characterized in that: The terminal part is installed in the terminal box.

8. A positioning method using any one of claims 1 to 7 of a narrow linewidth polarization-maintaining laser dual MZ 100-meter coherent positioning system, comprising the following steps: (1) The light emitting part inputs two light sources with specified narrow line width and specified low frequency to the terminal part through a long-distance vibrating optical fiber, and the two light sources form a mixed light with a small difference frequency, and the mixed light has strong coherence; the light processing part inputs one light source with specified narrow line width and specified low frequency to the terminal part through a positioning optical fiber; (2) Measure the distance between the output end of the light emitting part and the light processing part as L; (3) Obtaining the refractive index n of the long-distance vibration optical fiber and the positioning optical fiber; (4) When an intrusion event acts on the long-distance vibration optical fiber, the long-distance vibration optical fiber senses a vibration signal at a certain point; the terminal part receives the light from the light emitting part through the long-distance vibration optical fiber, interferes to form a path of interference light with a specified narrow line width value and a specified low frequency value, and then inputs it to the light processing part; the terminal part receives the light emitted by the light processing part through the positioning optical fiber, interferes to form two paths of interference light with a specified narrow line width value and a specified low frequency value, and then inputs it to the light emitting part; (5) The optical path of the light emitted by the optical processing part from the point of the vibration signal to the optical emitting part is nL1, and the time from the point of the vibration signal to the optical emitting part is t1; wherein L1 is set to be the physical distance from the point on the long-distance vibration optical fiber corresponding to the vibration signal to the optical emitting part; (6) The optical path of the light emitted by the light emitting part from the point of the vibration signal to the light processing part obtained by the light processing part is n(L2+L), and the time from the point of the vibration signal to the light processing part is t2; wherein L2 is set to be the physical distance from the point on the long-distance vibration optical fiber corresponding to the vibration signal to the light processing part; (7) The time delay between the bidirectional waveforms of the light emitted by the optical emitting part and the light emitted by the optical processing part is calculated by demodulation as dt=t2-t1; (8) Based on the time delay dt=(nL+ nL2-nL1) / c=2n(L-L1) / c, the physical distance from the point on the long-distance vibrating optical fiber corresponding to the vibration signal to the light emitting part is calculated as L1=Lc*dt / 2n.

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