Vibration Sensing Phase Modulation Method Based on Distributed Feedback Laser

Abstract

The present invention discloses a vibration sensing phase modulation method based on a distributed feedback laser. In the method, the distributed feedback laser is used as a vibration sensor for measuring vibration to obtain an optical signal. The optical signal and the pump light of the first wavelength enter a wavelength division multiplexer to generate a light beam of the second wavelength. The light beam of the second wavelength enters a 3×3 coupler after passing through a Michelson interferometer. Among them, the optical fiber of one arm of the fiber Michelson interferometer is wound around a piezoelectric ceramic PZT. A voltage is applied to the piezoelectric ceramic PZT to adjust the arm length of one arm of the Michelson interferometer to balance the intensity of the three output optical signals of the 3×3 coupler. A photodetector is connected to the 3×3 coupler to obtain three optical signals, and phase modulation is performed based on the three optical signals.

Description

Technical Field

[0001] The present invention belongs to the technical field of vibration monitoring, and particularly relates to a vibration sensing phase modulation method based on a distributed feedback laser. Background Art

[0002] The detection of vibration signals has important practical significance in the fields of oil exploration, mechanical industrial production, aerospace, geological monitoring, etc. By detecting vibration signals, oil exploration can be carried out more efficiently, thereby increasing the oil recovery rate. Since mechanical vibration is one of the main reasons for mechanical equipment failures, most equipment failures can be avoided by detecting vibration signals, thus ensuring the normal operation of the equipment. Aerospace equipment is all precision equipment, so even minor vibrations may lead to inaccurate data and may cause huge economic losses. And these situations can be avoided by detecting vibration signals.

[0003] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention proposes a vibration sensing phase modulation method based on a distributed feedback laser, which reduces the requirements for the detection lower limit of the detector and the difficulty of signal demodulation.

[0005] The object of the present invention is achieved through the following technical solutions. A vibration sensing phase modulation method based on a distributed feedback laser includes:

[0006] A distributed feedback laser is used as a vibration sensor for measuring vibration to obtain an optical signal. The optical signal and a pump light of a first wavelength enter a wavelength division multiplexer to generate a light beam of a second wavelength;

[0007] The light beam of the second wavelength enters a 3×3 coupler after passing through a Michelson interferometer. Among them, the optical fiber of one arm of the fiber Michelson interferometer is wound around a piezoelectric ceramic PZT. A voltage is applied to the piezoelectric ceramic PZT to adjust the arm length of one arm of the Michelson interferometer to balance the intensity of the three output optical signals of the 3×3 coupler;

[0008] A photodetector is connected to the 3×3 coupler to obtain three optical signals;

[0009] ,

[0010] Wherein, the coefficients A1, A2, and A3 are the DC components output by the 3×3 coupler, the coefficients B1, B2, and B3 are the AC components, C is the amplitude of the measured optical signal, is the frequency of the optical signal, and t is the time;

[0011] Perform phase modulation based on the three optical signals.

[0012] In the vibration sensing phase modulation method based on a distributed feedback laser, the first wavelength is 980 nm and the second wavelength is 1550 nm.

[0013] In the vibration sensing phase modulation method based on a distributed feedback laser, the photodetector is connected to an upper computer via a 14-bit AD converter to perform phase modulation based on the three optical signals.

[0014] In the vibration sensing phase modulation method based on a distributed feedback laser, the piezoelectric ceramic PZT is connected to a Faraday mirror.

[0015] In the vibration sensing phase modulation method based on a distributed feedback laser, the phase difference between each of the three optical signals is 120 o .

[0016] Compared with the prior art, the present invention has the following advantages: The distributed feedback (DFB) laser of the present invention has the advantages of narrow linewidth, small size, and high sensitivity. It converts the vibration signal into an optical signal, and then demodulates the optical signal to obtain the vibration information. One arm of the fiber optic Michelson interferometer is partially wound around the PZT, and a voltage is applied to the PZT so that the arm length of one arm of the Michelson interferometer can be adjusted, thereby making the intensities of the three output optical signals of the 3*3 coupler more balanced and reducing the difficulty of demodulating the vibration signal. This method adjusts the initial phase difference of the three signals so that the outputs of the three signals are at a relatively consistent level, reducing the requirements for the detection lower limit of the detector and the difficulty of signal demodulation, and having the advantages of being real-time, stable, and non-contact. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the following detailed description of the preferred specific embodiments, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Obviously, the following described drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0018] In the drawings:

[0019] Figure 1 is a layout schematic diagram of a vibration sensing phase modulation method based on a distributed feedback laser provided by an embodiment of the present invention.

[0020] The present invention will be further explained below with reference to the drawings and embodiments. Detailed Embodiments

[0021] Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although specific embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0022] It should be noted that in the description of the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The description in this specification and claims does not use the difference in terms as a way to distinguish components, but uses the difference in the functions of components as the criterion for distinction. As used throughout the specification and claims, the term "comprising" or "including" is an open-ended term and should be interpreted as "including but not limited to". The subsequent description of the specification is for the purpose of describing the preferred embodiments of implementing the present invention, but the description is for the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined by the appended claims.

[0023] For ease of understanding of the embodiments of the present invention, specific embodiments will be further explained below with reference to the accompanying drawings as examples, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0024] For better understanding, as Figure 1 shown, the vibration sensing phase modulation method based on a distributed feedback laser includes

[0025] A distributed feedback laser is used as a vibration sensor for measuring vibration to obtain an optical signal, and the optical signal and pump light of a first wavelength enter a wavelength division multiplexer to generate a light beam of a second wavelength;

[0026] The light beam of the second wavelength enters a 3×3 coupler via a Michelson interferometer. Among them, the optical fiber of one arm of the fiber Michelson interferometer is wound around a piezoelectric ceramic PZT, and a voltage is applied to the piezoelectric ceramic PZT to adjust the arm length of one arm of the Michelson interferometer to equalize the intensity of the three output optical signals of the 3×3 coupler;

[0027] A photodetector is connected to the 3×3 coupler to obtain three optical signals;

[0028] ,

[0029] wherein, coefficients A1, A2, and A3 are the DC components output by the 3×3 coupler, coefficients B1, B2, and B3 are the AC components, and C is the amplitude of the measured optical signal. is the frequency of the optical signal, t is the time, and u1, u2, and u3 are the optical signals received by three photodetectors connected to a 3×3 coupler;

[0030] Phase modulation is performed based on the three optical signals.

[0031] In a preferred embodiment of the vibration sensing phase modulation method based on a distributed feedback laser, the first wavelength is 980 nm and the second wavelength is 1550 nm.

[0032] In a preferred embodiment of the vibration sensing phase modulation method based on a distributed feedback laser, the photodetectors are connected to a host computer via a 14-bit AD converter to perform phase modulation based on the three optical signals.

[0033] In a preferred embodiment of the vibration sensing phase modulation method based on a distributed feedback laser, the piezoelectric ceramic PZT is connected to a Faraday mirror.

[0034] In a preferred embodiment of the vibration sensing phase modulation method based on a distributed feedback laser, each of the three optical signals has a phase difference of 120 o .

[0035] In one embodiment, when the arm length difference of the Michelson interferometer is fixed, the phase difference of the three signals is non-adjustable, which easily causes the output value of one signal to be large, while the output values of the other two signals are near zero and are difficult to detect, making the demodulation of the vibration signal difficult. In this method, a part of the optical fiber of one arm of the fiber optic Michelson interferometer is wound around the PZT, and a voltage is applied to the PZT, so that the arm length of one arm of the Michelson interferometer can be adjusted, thereby making the three output optical signals of the 3×3 coupler more balanced and reducing the difficulty of demodulating the vibration signal.

[0036] Example 1:

[0037] In this method, the 980-nm pump light enters the DFB vibration monitoring sensor head through a wavelength division multiplexer. After the 1550-nm backward light passes through the Michelson interferometer, it passes through a 3×3 coupler and a photodetector to detect the intensity signal carrying the vibration signal. The phase of the interferometer is adjusted to achieve the purpose of balancing the output of the 3×3 coupler. The specific scheme is that a part of the optical fiber of one arm of the fiber optic Michelson interferometer is wound around the PZT, and a voltage is applied to the PZT, so that the arm length of one arm of the Michelson interferometer can be adjusted, thereby making the intensities of the three output optical signals of the 3×3 coupler more balanced and reducing the difficulty of demodulating the vibration signal. The initial phase difference of the three signals can be adjusted to make the outputs of the three signals at a relatively consistent level, reducing the requirements for the detection lower limit of the detector and the difficulty of signal demodulation.

[0038] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art can also make many forms under the inspiration of this specification and without departing from the scope protected by the claims of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A vibration sensing phase modulation method based on a distributed feedback laser, characterized in that, It includes the following steps: A distributed feedback laser is used as a vibration sensor for measuring vibration to obtain an optical signal. The optical signal and pump light with a first wavelength enter a wavelength division multiplexer to generate a light beam with a second wavelength. The light beam with the second wavelength enters a 3×3 coupler after passing through a Michelson interferometer. Among them, the optical fiber of one arm of the fiber Michelson interferometer is wound around a piezoelectric ceramic PZT. A voltage is applied to the piezoelectric ceramic PZT to adjust the arm length of one arm of the Michelson interferometer to balance the intensity of the three-way output optical signals of the 3×3 coupler. A photodetector is connected to the 3×3 coupler to obtain three-way optical signals. ， Among them, A1, A2, and A3 are the DC components output by the 3×3 coupler, B1, B2, and B3 are the AC components, and C is the amplitude of the optical signal to be measured. is the frequency of the optical signal, and t is the time. Phase modulation is performed based on the three-way optical signals.

2. The vibration sensing phase modulation method based on a distributed feedback laser according to claim 1, characterized in that The first wavelength is 980 nm and the second wavelength is 1550 nm.

3. The vibration sensing phase modulation method based on a distributed feedback laser according to claim 1, wherein The photodetector is connected to a host computer via a 14-bit AD converter to perform phase modulation based on the three-way optical signals.

4. The vibration sensing phase modulation method based on a distributed feedback laser according to claim 1, wherein The piezoelectric ceramic PZT is connected to a Faraday mirror.

5. The vibration sensing phase modulation method based on a distributed feedback laser according to claim 1, characterized in that The phase difference between each of the three optical signals is 120 o .

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