Optical fiber FP pressure sensing probe based on multi-arm suspended membrane structure

Abstract

The invention relates to the field of Fabry-Perot interference sensors, and discloses an optical fiber FP pressure sensing probe based on a multi-arm suspension type membrane structure, which comprises a probe, the probe comprises an FP cavity and a pressure sensing membrane, the pressure sensing membrane is arranged opposite to the top end of a sensing optical fiber, so that the FP cavity is formed between the end surface of the sensing optical fiber and the pressure sensing membrane, and the FP cavity is communicated with the pressure sensing membrane. The FP cavity is connected with the end face of the sensing optical fiber, and the tip part of the sensing optical fiber is a bare fiber without a coating layer; the pressure sensing diaphragm is connected with the top end of the probe through a plurality of cantilevers, and the pressure sensing diaphragm is arranged opposite to the flat end surface of the tip of the sensing optical fiber, so that an FP (Fabry-Perot) cavity is formed. Compared with a complete closed pressure sensing diaphragm, the multi-arm suspension type pressure sensing diaphragm enables the device to have high sensitivity when detecting small pressure, meanwhile, the optical microcavity is communicated with the outside, and when external static pressure changes, the difference between the internal pressure and the external pressure of the optical microcavity does not change.

Description

Technical Field

[0001] The invention relates to the technical field of Fabry-Perot interference sensors, in particular to an optical fiber FP pressure sensing probe based on a multi-arm suspended membrane structure. Background Art

[0002] Fabry-Perot (FP) interferometric fiber sensors are widely used in metrology, atomic spectroscopy, astronomy, light scattering, and plasma diagnostics, and can be divided into intrinsic and extrinsic types. Compared with the intrinsic fiber FP resonant cavity, the extrinsic fiber FP resonant cavity has high precision, short cavity length (can be as short as a few microns), wide free spectrum range, and a very wide wavelength adjustment range (up to several hundred nanometers), which is more suitable for high-precision pressure sensing.

[0003] Blood pressure belongs to fluid dynamic pressure. When it is necessary to endoscopically and invasively measure the blood pressure inside the blood vessel, the pressure-sensitive diaphragm of the sensor is deformed, causing the length of the optical microcavity to change, thereby causing the interference fringes to change and achieve the measurement purpose. Traditional pressure-sensitive diaphragms mostly use a complete diaphragm structure with peripheral fixed supports. The membrane structure has a large stiffness and cannot cause the pressure-sensitive diaphragm to deform or deform slightly when subjected to pulsating micropressure, resulting in the measurement process not producing effective results or poor linearity of the measurement results. There is an urgent need for a fiber optic probe with low deformation stiffness, high sensitivity, and high stability. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a fiber optic FP pressure sensing probe based on a multi-arm suspended membrane structure, which solves the problem of high rigidity and non-deformation of the membrane structure caused by the peripheral fixing of the traditional full membrane structure, and improves the pressure sensing sensitivity of the pressure-sensitive membrane structure.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: an optical fiber FP pressure sensing probe based on a multi-arm suspended membrane structure, comprising a probe, the probe comprising an FP cavity and a pressure-sensitive diaphragm, the pressure-sensitive diaphragm is arranged opposite to the top of the sensing optical fiber, so that an FP cavity is formed between the end face of the sensing optical fiber and the pressure-sensitive diaphragm, the FP cavity is connected to the end face of the sensing optical fiber, and the sensing optical fiber is composed of a coated layer and an uncoated bare fiber part.

[0006] Preferably, the central reflection area of ​​the pressure-sensitive diaphragm is connected to the top of the probe through a plurality of cantilevers, and the central reflection area of ​​the pressure-sensitive diaphragm and the end face of the sensing optical fiber form an FP cavity.

[0007] Preferably, the central reflection area of ​​the pressure-sensitive diaphragm and the end face of the sensing optical fiber are arranged opposite to each other.

[0008] Preferably, the sensing optical fiber includes but is not limited to single-mode optical fiber, multi-mode optical fiber or photonic crystal.

[0009] A method for manufacturing an optical fiber FP pressure sensing probe based on a multi-arm suspension membrane structure, according to an optical fiber FP pressure sensing probe based on a multi-arm suspension membrane structure, comprising the following manufacturing steps:

[0010] S1: Strip off a portion of the coating layer at the tip of the sensing optical fiber, and cut the end face of the sensing optical fiber with the help of an optical microscope and a fiber cleaver, leaving a bare fiber with a length of 500 microns;

[0011] S2: Place the optical fiber vertically, keep its end face horizontal, use the optical fiber end face as the substrate, and use two-photon polymerization micro-nano 3D printing technology to align the printed probe on the optical fiber end face;

[0012] S3: Soak the prepared probe in alcohol to remove excess photoresist in the FP cavity.

[0013] The present invention provides an optical fiber FP pressure sensing probe based on a multi-arm suspension membrane structure. It has the following beneficial effects:

[0014] The present invention prints a sensing probe on the flat end face of the sensing optical fiber, and a multi-arm suspended pressure-sensitive diaphragm enables the device to have high sensitivity when detecting a relatively small pressure. At the same time, the optical microcavity is connected to the outside world. When the external static pressure changes, the internal and external pressure difference of the optical microcavity does not change, thereby ensuring that the working point of the present invention is stable and the performance of the present invention is not affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a cross-sectional schematic diagram of the present invention.

[0016] Figure 2 It is a schematic diagram of the overall structure of the present invention.

[0017] Figure 3 It is a schematic diagram of the multi-arm suspended membrane structure of the present invention.

[0018] Among them, 1. optical fiber; 2. coating layer; 3. fiber core; 4. probe; 5. pressure-sensitive diaphragm; 6. FP cavity; 7. central reflection area; 8. cantilever. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Example:

[0021] Reference Figure 1-3The present invention provides an optical fiber FP pressure sensing probe based on a multi-arm suspended membrane structure, comprising: a probe 4, an FP cavity 6 inside the probe 4, a pressure-sensitive membrane 5 at the top of the probe 4; a sensing optical fiber 1, a tip of the sensing optical fiber 1 being a part of a core 3 with a 500um coating layer 2 stripped off, a central circular reflection area 7 of the pressure-sensitive membrane 5 being arranged opposite to the end face of the sensing optical fiber 1, and a FP cavity 6 being formed between the end face of the sensing optical fiber 1 and the pressure-sensitive membrane 5.

[0022] The FP cavity 6 is used to form an interference light signal. The FP cavity 6 is connected to the outside world. When the sensing probe is placed in different static pressure environments, the pressure difference between the inside of the FP cavity 6 and the external environment remains unchanged. Therefore, no matter how the background static pressure of the environment changes, the interference fringes will not move, thereby ensuring that the working point of the probe is stable at the initial position. When the environmental dynamic pressure acts on the pressure-sensitive diaphragm 5, the pressure-sensitive diaphragm 5 is deformed, causing the length of the FP cavity 6 to change, so that the interference fringes of the optical fiber FP cavity 6 can effectively reflect the change information of the external dynamic pressure.

[0023] According to a further optimized solution, the probe 4 includes an FP cavity 6 which is connected to the end face of the sensing optical fiber 1 .

[0024] According to a further optimized solution, the end face of the sensing optical fiber 1 is used as a substrate, and the sensing probe 4 is printed on the end face of the sensing optical fiber 1 .

[0025] According to a further optimized solution, the pressure-sensitive membrane 5 includes a central reflection area 7 and a cantilever 8 . The pressure-sensitive membrane 5 is perpendicular to the axis of the probe 4 . The pressure-sensitive membrane 5 is arranged opposite to the end face of the sensing optical fiber 1 .

[0026] According to a further optimized solution, the pressure-sensitive diaphragm 5 and the sensing probe 4 are integrated into one.

[0027] A method for manufacturing the multi-arm suspension membrane structure optical fiber FP pressure sensing probe comprises the following steps:

[0028] S1: strip a portion of the coating layer 2 at the front end of the sensing optical fiber 1, and cut the end face of the sensing optical fiber 1 where the coating layer 2 is stripped flat, leaving a length of 500 um.

[0029] S2: Place the sensing optical fiber 1 vertically to ensure that its end face remains horizontal, use the end face of the sensing optical fiber 1 as a substrate, and use two-photon polymerization micro-nano 3D printing technology to align and print the sensing probe 4 on the end face of the sensing optical fiber 1.

[0030] S3: Soak the prepared sensor probe 4 in alcohol to remove excess photoresist in the FP cavity 6 .

[0031] The sensing probe 4 is 250 um long and 100 um in diameter, and the FP cavity 6 is 80 um in diameter.

[0032] The thickness of the pressure-sensitive membrane 5 is 5 um, the width of the cantilever 8 of the pressure-sensitive membrane is 20 um, the length is 80 um, the diameter of the middle emission area is 40 um, and the material of the sensing probe 4 is preferably photoresist.

[0033] The sensing optical fiber 1 is a single-mode optical fiber, a multi-mode optical fiber or a photonic crystal.

[0034] like Figure 1 As shown, the sensing optical fiber 1 is placed in a through hole coaxial with the collimating sleeve, and the end face of the sensing optical fiber 1 is aligned with the center of the pressure-sensitive diaphragm 5. Figure 3 As shown, the central reflection area 7 of the pressure-sensitive diaphragm 5 is connected to the top of the sensing probe 4 through a plurality of cantilevers 8, and the optical fiber FP cavity 6 is connected to the outside world, so that when the probe is placed in different static pressure environments for use, the pressure difference between the optical fiber FP cavity 6 and the external environment remains unchanged. Therefore, no matter how the static pressure of the external environment changes, the interference fringes will not move, thereby ensuring that the working point of the sensor is stable at the initial position; when the environmental dynamic pressure acts on the pressure-sensitive diaphragm 5, the interference fringes of the optical fiber FP cavity 6 change accordingly, thereby reflecting the dynamic pressure information. The pressure-sensitive diaphragm 5 adopts a multi-arm suspension structure, and its structure can also be deformed when the external dynamic pressure is small, thereby improving the sensitivity of the pressure sensor, that is, when the external pressure is small, the cavity length of the optical fiber FP cavity 6 of the pressure sensor can also change, so that the interference fringes of the optical fiber FP cavity 6 can effectively reflect the change information of the external dynamic pressure.

[0035] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An optical fiber FP pressure sensing probe based on a multi-arm suspension membrane structure, characterized in that: The invention comprises a probe (4), wherein the probe (4) comprises an FP cavity (6) and a pressure-sensitive membrane (5), wherein the pressure-sensitive membrane (5) is arranged opposite to the top end of a sensing optical fiber (1), so that an FP cavity (6) is formed between the end face of the sensing optical fiber (1) and the pressure-sensitive membrane (5), and the FP cavity (6) is connected to the end face of the sensing optical fiber (1), wherein the sensing optical fiber (1) is sequentially composed of a portion with a coating layer (2) and a bare fiber portion (3) with the coating layer removed.

2. The optical fiber FP pressure sensing probe based on a multi-arm suspended membrane structure according to claim 1, characterized in that: The pressure-sensitive diaphragm (5) is connected to the top of the probe (4) through a plurality of cantilevers (8), and the pressure-sensitive diaphragm (5) is arranged opposite to the end face of the bare fiber (3) of the sensing optical fiber (1), thereby forming an FP cavity (6).

3. The optical fiber FP pressure sensing probe based on a multi-arm suspension membrane structure according to claim 1, characterized in that: The pressure-sensitive diaphragm (5) is connected to a central reflection area (7) via a plurality of cantilevers (8), and the central reflection area (7) is arranged opposite to the end face of the bare fiber (3) of the sensing optical fiber (1).

4. The optical fiber FP pressure sensing probe based on a multi-arm suspended membrane structure according to claim 1, characterized in that: The sensing optical fiber (1) includes but is not limited to single-mode optical fiber, multi-mode optical fiber or photonic crystal.

5. A method for manufacturing an optical fiber FP pressure sensing probe based on a multi-arm suspended membrane structure, according to any one of claims 1 to 4, characterized in that: The manufacturing steps include: S1: stripping off a portion of the coating layer (2) at the tip of the sensing optical fiber (1), and flattening the end face of the sensing optical fiber with the aid of an optical microscope and an optical fiber cutter, leaving a bare fiber (3) with a length of 500 microns; S2: Place the optical fiber (1) vertically, keep its end face horizontal, and use the end face of the optical fiber (1) as a substrate, and use two-photon polymerization micro-nano 3D printing technology to align the printed probe (4) on the end face of the optical fiber (1); S3: Soak the prepared probe (4) in alcohol to remove excess photoresist in the FP cavity (6).

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