Diaphragm type EFPI optical fiber sonic sensor with sensibilization structure

Abstract

The invention discloses a diaphragm type EFPI optical fiber sonic sensor with a sensibilization structure, and relates to the field of optical fiber sensing and underwater acoustic signal communication. The sensor is composed of an optical fiber unit, a threaded sleeve and a sensitization shell which are connected in sequence. The single-mode optical fiber is embedded into the optical fiber ceramic ferrule as a first reflecting surface and inserted into the threaded sleeve in a combined manner, and the chromium-gold composite film is attached to the outer side of the threaded sleeve as a second reflecting surface through epoxy resin glue; the sensitization shell is combined with the threaded sleeve in a screwed mode, the chromium-gold composite film is protected, sound signals are gathered, and the sensitization effect is achieved. The invention has the following advantages and positive effects: (1) the FZP sensitization structure improves the minimum detectable sound pressure of the hydrophone and enhances the capability of identifying weak small signals; (2) the designed water pressure balance hole contributes to the water pressure in the F-P cavity and the outside, and can be suitable for deepwater operation; and (3) the nano-scale transduction film of the film type EFPI sensor can be protected to a certain extent, and the film type EFPI sensor can be suitable for changing environments.

Description

Technical Field

[0001] The invention relates to the field of optical fiber sensing and underwater acoustic signal communication, and in particular to a diaphragm-type EFPI optical fiber acoustic wave sensor with a sensitivity enhancement structure, which is a highly sensitive and reliable diaphragm-type EFPI optical fiber sensor. Background Art

[0002] In recent years, as my country vigorously promotes the strategy of building a strong maritime nation, integrated communications in the air, space, sea and land have become the main direction of future development in the field of electronic communications. Fiber-optic hydrophones have received great attention in the field of underwater acoustic communication and sensing. Compared with traditional electrical hydrophones, fiber-optic hydrophones have the characteristics of anti-electromagnetic interference, corrosion resistance, high sensitivity, and easy miniaturization. They are widely used in the field of underwater acoustic signal detection; but at the same time, due to their excessive sensitivity, they are also easily interfered by factors such as environmental noise, resulting in the inability to guarantee stable recognition capabilities under special environments. For EFPI-type thin-film fiber-optic hydrophones, the interference between the two reflecting surfaces is equivalent to double-beam interference. After the acoustic signal acts on the transducer film, the optical path difference changes, resulting in a change in the phase of the interference light, which in turn leads to a periodic change in the intensity of the interference light, thereby using the change in the intensity of the reflected interference light to identify the acoustic signal. However, due to the large loss of the detection light as reflected light, its ability to identify weak signals is relatively general compared to other types of optical fiber sensors. In order to overcome this problem, scholars from various countries have conducted research on new demodulation methods, high-precision noise reduction algorithms, and sensor probe sensitivity enhancement structures for EFPI-type sensors in recent years. Summary of the invention

[0003] The purpose of the present invention is to provide a diaphragm-type EFPI optical fiber acoustic wave sensor with a sensitivity enhancement structure, which aims to reduce the problems of poor intensity demodulation effect, serious signal distortion, difficulty in identifying weak signals, etc. caused by noise interference in complex environments and underwater communications, and to a certain extent solve the problem of small and weak signals being difficult to identify underwater, and improve the system detection sensitivity, reliability and practicality. It provides an effective and applicable system example for the field of underwater acoustic communication, which is helpful to further enrich my country's marine defense science and technology products and promote the construction of a strong maritime nation.

[0004] Existing diaphragm-type EFPI optical fiber acoustic wave sensors are as follows: Figure 1 shown.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] That is, a sensitivity enhancement structure is added on the basis of the existing diaphragm-type EFPI optical fiber acoustic wave sensor.

[0007] Specifically:

[0008] It consists of an optical fiber unit, a threaded sleeve and a sensitivity-enhancing housing connected in sequence;

[0009] The optical fiber unit includes a single-mode optical fiber and an optical fiber ceramic ferrule;

[0010] The threaded sleeve includes an inner ceramic insert embedding groove, a balanced air pressure hole at the edge of the embedding groove, a balanced air pressure hole on the side of the thread, a chrome-gold composite film, an FP cavity, and a screw thread;

[0011] The sensitivity-enhancing housing includes a screw thread, a balanced air pressure hole on the side of the threaded housing, and a fourth-order FZP sensitivity-enhancing structure;

[0012] The connection relationship is:

[0013] The single-mode optical fiber is embedded in the optical fiber ceramic ferrule as the first reflection surface, and the combination is inserted into the threaded sleeve. The chrome-gold composite film is attached to the outside of the threaded sleeve by epoxy resin glue as the second reflection surface; the sensitivity-enhancing shell is threadedly combined with the threaded sleeve to protect the chrome-gold composite film and gather sound signals, thereby playing a sensitivity-enhancing role.

[0014] The present invention has the following advantages and positive effects:

[0015] ① The FZP sensitivity enhancement structure increases the minimum detectable sound pressure of the hydrophone and enhances its ability to identify weak signals;

[0016] ②The designed water pressure balance hole helps to balance the water pressure inside the FP cavity with the outside world, which can be used for deep-water operations;

[0017] ③ It has a certain protective effect on the nano-scale transducer film of the thin-film EFPI sensor and can be used in changing environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of an existing thin-film EFPI optical fiber sensor;

[0019] Figure 2 This is the working principle diagram of the fourth-order Fresnel zone plate FZP;

[0020] Figure 3 It is a schematic diagram of the structure of a thin-film EFPI optical fiber sensor with a sensitivity enhancement structure;

[0021] Figure 4 It is an application system diagram of the present invention.

[0022] In the figure:

[0023] A—A membrane-type EFPI optical fiber sensor with a sensitivity enhancement structure,

[0024] 1—Fiber optic unit,

[0025] 1-1—single-mode optical fiber, 1-2 optical fiber ceramic ferrule;

[0026] 2—threaded sleeve,

[0027] 2-1—Inner ceramic sleeve embedded in the groove,

[0028] 2-2—Balanced air pressure hole on the edge of the embedded groove,

[0029] 2-3—Balance air pressure hole on the threaded side,

[0030] 2-4—Chrome-gold composite film,

[0031] 2-5—FP cavity,

[0032] 2-6—screw thread;

[0033] 3—Sensitivity-enhanced shell

[0034] 3-1—Screw thread,

[0035] 3-2—Balance air pressure hole on the side of the threaded housing,

[0036] 3-3—Fourth-order FZP sensitization shell structure;

[0037] B—DFB laser;

[0038] C—fiber circulator;

[0039] D—photoelectric detector;

[0040] E—high-speed data acquisition module;

[0041] F—control and signal processing module;

[0042] G—Standard microphone.

[0043] English to Chinese

[0044] 1. EFPI: Extrinsic Fabry-Perot Interferometric, external cavity Fabry-Perot interferometer.

[0045] 2. FZP: Fresnel-Zone-Plate, Fresnel zone plate. DETAILED DESCRIPTION

[0046] The following is a detailed description with reference to the embodiments and drawings:

[0047] Diaphragm-type EFPI optical fiber sensor with enhanced sensitivity structure

[0048] I. Overall

[0049] like Figure 3 , consisting of an optical fiber unit 1, a threaded sleeve 2 and a sensitivity-enhancing housing 3 connected in sequence;

[0050] The optical fiber unit 1 includes a single-mode optical fiber 1-1 and an optical fiber ceramic ferrule 1-2;

[0051] The threaded sleeve 2 includes an inner ceramic insert embedding groove 2-1, a balanced air pressure hole 2-2 at the edge of the embedding groove, a balanced air pressure hole 2-3 on the side of the thread, a chrome-gold composite film 2-4, an FP cavity 2-5, and a screw thread 2-6;

[0052] The sensitivity-enhancing housing 3 includes a screw thread 3-1, a balanced air pressure hole 3-2 on the side of the threaded housing, and a fourth-order FZP sensitivity-enhancing structure 3-3;

[0053] The connection relationship is:

[0054] The single-mode optical fiber 1-1 is embedded in the optical fiber ceramic ferrule 1-2 as the first reflection surface, and the combination is inserted into the threaded sleeve 2. The chrome-gold composite film 2-4 is attached to the outside of the threaded sleeve 2 by epoxy resin glue as the second reflection surface; the sensitivity-enhancing shell 3 is threadedly combined with the threaded sleeve 2 to protect the chrome-gold composite film 2-4 and gather sound signals, thereby playing a sensitivity-enhancing role.

[0055] 2. Functional Unit

[0056] 1. Fiber optic unit 1

[0057] The optical fiber unit 1 includes a single-mode optical fiber 1-1 and an optical fiber ceramic ferrule 1-2;

[0058] The position and connection relationship thereof is that the optical fiber ceramic ferrule 1-2 is embedded with the single-mode optical fiber 1-1.

[0059] 1) Single-mode fiber 1-1

[0060] The common communication single-mode optical fiber G.652 is used, and after removing the cladding, a ceramic ferrule 1-2 is embedded as a reflection surface of the interferometer.

[0061] 2) Optical fiber ceramic ferrule 1-2

[0062] A common FC type ceramic ferrule is used, with an outer aperture of 2.5 mm and an inner aperture of 125 μm, for embedding the single-mode optical fiber 1 - 1 , playing a role of alignment and fixation, and is inserted into the threaded sleeve 2 in combination.

[0063] 2. Threaded sleeve 2

[0064] The threaded sleeve 2 is a cylindrical body made of stainless steel, with a height of 8 mm and a cross section of 7 mm, including an inner ceramic insert embedding groove 2-1, a balanced air pressure hole 2-2 at the edge of the embedding groove, a balanced air pressure hole 2-3 on the side of the thread, a chrome-gold composite film 2-4, an FP cavity 2-5 and a screw thread 2-6;

[0065] Its location and connection relationship are:

[0066] The inner ceramic insert embedding groove 2-1 is placed at the center of the threaded sleeve 2, the balancing air pressure hole 2-2 on the edge of the embedding groove is on the groove wall of the inner ceramic insert embedding groove 2-1, the front end of the threaded sleeve 2 is designed as a threaded thread 2-6, the balancing air pressure hole 2-3 on the side of the thread is on the side of the threaded thread 2-6, and the chrome-gold composite film 2-4 is connected to the front end opening of the threaded sleeve 2.

[0067] 1) Inner ceramic ferrule embedded in groove 2-1

[0068] The threaded sleeve 2 has a 2.5mm center hole diameter, which facilitates the embedding of the optical fiber unit.

[0069] 2) Balance air pressure hole 2-2 on the edge of the embedded groove

[0070] The inner ceramic insert is embedded in the groove wall of the groove 2-1 and has a pore of about 1 mm.

[0071] 3) 2-3 threaded side balance air pressure holes

[0072] There is a 1mm pressure balancing hole on the thread side, which is used to balance the pressure inside the FP cavity and the outside world.

[0073] 4) Chrome-gold composite film 2-4

[0074] A 110nm chromium-gold composite film was prepared by electron beam evaporation, with chromium and gold being 10nm and 100nm respectively, and was transferred to the central aperture of the threaded sleeve 2 by a sacrificial layer wet transfer method. The film size is a circle with a radius of 2.5mm.

[0075] 5) FP cavity 2-5

[0076] A multi-beam interference is formed between the single-mode optical fiber 1-1 and the chrome-gold composite film 2-4. The change of the FP cavity length will affect the change of the optical path difference of the photoacoustic signal, thereby realizing the sensing function.

[0077] 6) Screw thread 2-6

[0078] It is used to screw the sensitization shell 3 to connect and fix it. The hole diameter is 6mm, and the outer ring can be used to fix the chrome-gold composite film 2-4.

[0079] 3. Sensitization shell 3

[0080] The threaded shell 3 is made of stainless steel, including a screw thread 3-1, a balanced air pressure hole 3-2 on the side of the threaded shell, and a fourth-order FZP sensitivity enhancement structure 3-3.

[0081] Its location and connection relationship are:

[0082] The screw thread 3-1 is placed inside the center of the threaded shell 3, and the balanced air pressure hole 3-2 on the side of the threaded shell opens out of the sensitivity-enhancing shell 3 from the inside of the screw thread 3-1. The fourth-order FZP sensitivity-enhancing structure 3-3 is designed at the outer center aperture of the threaded shell 3.

[0083] 1) Screw thread 3-1

[0084] It is used for screwing the threaded sleeve 2, and the hole diameter complements the screw thread 2-6, so as to play the role of connection and fixing.

[0085] 2) Balance air pressure hole 3-2 on the side of threaded housing

[0086] It is placed parallel to the balanced air pressure hole 2-3 on the threaded side. After the threaded sleeve 2 and the sensitizing housing 3 are screwed together, the air pressure of the external environment and the FP cavity are kept consistent to ensure the normal operation of the balanced air pressure hole 2-3 on the threaded side.

[0087] 3) Fourth-order FZP sensitization structure 3-3

[0088] The outermost part of the sensitivity enhancement housing 3, as the front end of the sensor, directly contacts the sound signal and is made by laser etching, which plays the role of gathering the sound signal and improving the sensitivity. The central circle aperture of the zone plate is 2mm, the circle of each order of the zone plate is 1mm, and the spacing of each order is 0.5mm. The aperture of the entire fourth-order FZP sensitivity enhancement structure 3-3 is 15mm.

[0089] like Figure 3 The thin-film EFPI optical fiber sensor with a sensitivity enhancement structure is mainly composed of a thin-film EFPI optical fiber sensor head as the main body, a sensing optical fiber unit and a FZP structure threaded sleeve with acoustic signal amplification and sensitivity enhancement functions as a protective shell, thereby realizing the convergence and amplification of weak acoustic signals and improving the sensitivity of the optical fiber sensor.

[0090] like Figure 2 The FZP structure threaded sleeve is nested in the center of the film and is designed as a fourth-order Fresnel zone wave plate structure. The film is a chrome-gold composite structure.

[0091] The working mechanism is:

[0092] When the EFPI fiber optic sensor probe is working, the chrome-gold film converts the acoustic wave signal into mechanical vibration. Due to the introduction of the FZP structure, the acoustic wave is focused on Figure 3 At the center of the chromium-gold film, the film will obtain a higher amplitude of mechanical vibration, causing the FP cavity length to change, causing the phase of the interference light to change, and then converting it into a periodic change in the intensity of the interference light, thereby realizing the amplification and recognition of weak sound signals and improving the detection sensitivity of the optical fiber sensor.

[0093] That is, the present invention introduces a FZP sensitivity enhancement structure in the center of the EFPI fiber optic sensor probe diaphragm, and achieves targeted recognition enhancement of signals of different frequencies by changing the FZP order. Generally speaking, the higher the FZP order, the stronger the ability to converge sound wave signals and the better the sensitivity enhancement effect, but at the same time the structure volume is also larger. Compared with other diaphragm sensitivity enhancement structures, this scheme amplifies and converges the sound signal at the sound source, that is, before the weak sound wave acts on the film, the FZP structure will first amplify the signal, causing a greater deformation of the diaphragm, so that the change in the cavity length of the EFPI fiber optic sensor probe produces a more obvious change in light intensity, thereby detecting weak and wider-range audio signals.

[0094] A manufacturing process of a membrane-type EFPI optical fiber acoustic wave sensor with a sensitivity enhancement structure:

[0095] ① The inner diameter of the inner ceramic insert embedding groove 2-1 is 2.5±0.01mm, and the side is designed with an embedding groove edge balance air pressure hole 2-2 with an outer diameter of 1mm extending from the embedding groove to the FP cavity 2-5, and the cavity length L is about 200μm; the threaded side balance air pressure hole 2-3 with a diameter of 1mm set in the FP cavity 2-5 in the threaded sleeve 2 is screwed through the threaded shell 3, and the threaded shell 3 side balance air pressure hole 3-2 and the threaded side balance air pressure hole 2-3 are tightly combined at the connection;

[0096] ②The fourth-order FZP sensitization shell structure 3-3 was prepared by laser etching and had a diameter of 15 mm;

[0097] ③ A 110nm protective chromium-gold composite film 2-4 was prepared by electron beam evaporation, and the film was separated by a sacrificial layer wet transfer method. The film was then fixed on the threaded thread 2-6 of the stainless steel threaded sleeve body 2 with epoxy resin glue as an acoustic-optical transducer film with an outer diameter of 5mm.

[0098] 2. Sensing System

[0099] 1. Overall

[0100] like Figure 4 ,This sensing system includes a membrane-type EFPI optical fiber sensor A with FZP sensitivity enhancement structure, a DFB laser B, an optical fiber circulator C, a photoelectric detector D, a high-speed data acquisition module E, a control and signal processing module F and a standard microphone G;

[0101] The connection relationship is:

[0102] The diaphragm EFPI optical fiber sensor A of the FZP sensitivity enhancement structure and the DFB laser B are respectively connected to the optical fiber circulator C; the optical fiber circulator C, the photoelectric detector D, the control and signal processing module F and the standard microphone G are connected in sequence;

[0103] The high-speed data acquisition module E is connected to the control and signal processing module F.

[0104] Working mechanism:

[0105] The narrow-linewidth DFB laser B emits monochromatic light and enters the fiber circulator C. After passing through the diaphragm-type EFPI fiber optic sensor A with an FZP sensitivity enhancement structure, the reflected light received by the sensor information is output from the fiber circulator C. The interference light signal carrying the frequency information passes through the photodetector D and then undergoes secondary noise reduction and optimized demodulation by the signal processing module F. Finally, the detection results are recorded by the high-speed acquisition module E.

[0106] 2. Functional Unit

[0107] 1) Diaphragm-type EFPI optical fiber sensor A with FZP sensitivity enhancement structure

[0108] As the main body of the sensing system, it gathers, amplifies and detects external sound pressure signals.

[0109] 2) DFB laser B

[0110] Provides a monochromatic light source for sensing. Usually a narrow linewidth laser is used. This application uses the DFB-B14-1533-SM / 9 / 125-01 DFB laser. Connect to the C1 port of the fiber circulator.

[0111] 3) Fiber Optic Circulator C

[0112] It uses common communication band optical fiber circulator, with ports 1, 2, and 3, 1 in and 2 out, and 2 in and 3 out.

[0113] 4) Photodetector D

[0114] The KG-APR-500M photoelectric detector D with high sampling rate is used to convert optical signals into electrical signals.

[0115] 5) High-speed data acquisition module E

[0116] The high sampling rate NIPCIe-6920-250M data acquisition card is used to quickly and accurately acquire the electrical signal after D conversion of the photodetector.

[0117] 6) Control and signal processing module F

[0118] It is used to perform secondary optimization processing on the signals collected by the high-speed data acquisition module E, and to drive and collect information from the standard microphone G. This module is written on LABVIEW and is connected to the high-speed data acquisition module E for use.

[0119] 7) Standard microphone G

[0120] The model is BK4231, which is used to collect acoustic signals and to calibrate the data of the highly sensitive and reliable diaphragm-type EFPI optical fiber sensor A.

[0121] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A diaphragm-type EFPI optical fiber acoustic wave sensor with a sensitivity enhancement structure, characterized in that: It consists of an optical fiber unit (1), a threaded sleeve (2) and a sensitivity-enhancing housing (3) which are connected in sequence; The connection relationship is: The single-mode optical fiber (1-1) is embedded in the optical fiber ceramic ferrule (1-2) as a first reflection surface, and the combination is inserted into the threaded sleeve (2); the chrome-gold composite film (2-4) is attached to the outer side of the threaded sleeve (2) by epoxy resin glue as a second reflection surface; the sensitivity enhancement housing (3) is screwed together with the threaded sleeve (2) to protect the chrome-gold composite film (2-4) and gather sound signals, thereby playing a sensitivity enhancement role.

2. The manufacturing process of the diaphragm-type EFPI optical fiber acoustic wave sensor with a sensitivity enhancement structure according to claim 1, characterized in that: ① The inner diameter of the inner ceramic insert embedding groove (2-1) is 2.5±0.01 mm, and a 1 mm outer diameter embedding groove edge balance air pressure hole (2-2) is designed on the side, extending from the embedding groove to the FP cavity (2-5), and the cavity length L is about 200 μm; the threaded side balance air pressure hole (2-3) with a diameter of 1 mm is arranged in the FP cavity (2-5) in the threaded sleeve (2), and after being screwed with the threaded outer shell (3), the threaded outer shell (3) side balance air pressure hole (3-2) and the threaded side balance air pressure hole (2-3) are tightly combined at the connection; ② The fourth-order FZP sensitization shell structure (3-3) was prepared by laser etching with a diameter of 15 mm; ③ A 110nm protective chromium-gold composite film (2-4) was prepared by electron beam evaporation, and the film was separated by a sacrificial layer wet transfer method. The film was then fixed on the threaded thread (2-6) of the stainless steel threaded sleeve body (2) with epoxy resin glue as an acoustic-optical transducer film with an outer diameter of 5mm.

3. A sensing system based on the diaphragm-type EFPI optical fiber acoustic wave sensor with a sensitivity enhancement structure according to claim 1 or 2, characterized in that: It includes a membrane-type EFPI optical fiber sensor with FZP sensitivity enhancement structure (A), a DFB laser (B), an optical fiber circulator (C), a photodetector (D), a high-speed data acquisition module (E), a control and signal processing module (F) and a standard microphone (G); The connection relationship is: The diaphragm EFPI optical fiber sensor (A) and the DFB laser (B) of the FZP sensitivity enhancement structure are connected to the optical fiber circulator (C) respectively; the optical fiber circulator (C), the photoelectric detector (D), the control and signal processing module (F) and the standard microphone (G) are connected in sequence; The high-speed data acquisition module (E) is connected to the control and signal processing module (F).

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