High-sensitivity micro-pressure sensing device based on double-end fabry-perot cavity cascade coupling

Abstract

The utility model discloses a high sensitivity micro pressure sensing device based on double end fabry -perot cavity cascade coupling belongs to optical fiber sensing technical field. The device includes the broadband light source, optical fiber isolator, 2*2 optical fiber coupler and with coupler output respectively connected detection end fabry -perro cavity and reference end fabry -perro cavity that connect in proper order, and the second input of coupler connects spectrometer, and spectrometer is connected with host computer. In which detection end is the pressure sensitive cavity that corrugated diaphragm and single mode optical fiber end face constitute, and reference end is the fixed cavity that fused quartz substrate and single mode optical fiber end face constitute, and two cavity initial cavity length error is less than or equal to 1%. The host computer is passed through fast fourier transform and differential algorithm to extract phase information and eliminate common mode noise to realize subnanometer level phase resolution through the real -time capture cascade interference spectrum of spectrometer and transmits to host computer, realizes pressure signal amplification through double cavity cascade coupling and solves the technical problem of low sensitivity, poor signal -to -noise ratio of traditional sensor.

Description

Technical Field

[0001] This utility model relates to the field of fiber optic sensing technology, specifically to a high-sensitivity micro-pressure sensing device that uses a double-ended Fabry-Perot cavity cascade coupling, suitable for dynamic micro-pressure monitoring of industrial pipelines, high-precision pressure detection in medical implantation devices and fluid mechanics experiments. Background Technology

[0002] Traditional single-resonant-cavity Fabry-Perot cavity pressure sensors rely solely on changes in optical path difference, making it difficult to effectively extract weak pressure signals and resulting in generally low sensitivity. Random offsets in cavity length caused by environmental coupling interference such as thermal drift and mechanical vibration can lead to significant measurement errors, particularly in dynamic pressure monitoring of industrial pipelines and implantable detection scenarios. Furthermore, multiple factors, including light source fluctuations, optical path losses, and air gap scattering, can degrade interference signal quality, affecting signal detection. Existing technologies such as dual-wavelength demodulation can partially improve sensitivity, but suffer from high demodulation system complexity and increased costs. While microelectromechanical system (MEMS) packaging can enhance anti-interference capabilities, it degrades the sensor's dynamic response characteristics. Therefore, there is an urgent need to develop a novel pressure sensing architecture that combines high sensitivity, excellent environmental robustness, and long-term stability. To address these issues, this invention presents a novel pressure sensing device that combines high sensitivity, strong anti-interference capabilities, and long-term stability to meet the stringent requirements for micro-pressure detection in industrial and medical fields. Summary of the Invention

[0003] This invention provides a high-sensitivity micro-pressure sensing device based on a dual-ended Fabry-Perot cavity cascade coupling. It addresses the low sensitivity and poor anti-interference capabilities of traditional sensors by utilizing vernier effect interference spectrum amplification technology, achieving an order-of-magnitude improvement in pressure sensitivity. The output light from the broadband light source, after being deflected by an isolator, enters the coupler, where a 2×2 coupler splits the light to the detection and reference cavities. The detection cavity consists of a corrugated diaphragm (316L stainless steel plated with a 50 nm gold film) and a single-mode fiber end face, with a cavity length of 50–300 μm. External pressure causes diaphragm deformation, resulting in changes in cavity length. The reference cavity is a fixed cavity formed by a fused silica substrate and a single-mode fiber end face, with both cavity length errors ≤1%. The reflected light from the two cavities is superimposed through interference to form a cascaded interference spectrum. By matching the FSR difference between the two cavities, the pressure signal can be amplified. The sensitivity is improved by up to 20 times compared to a single-cavity instrument. The spectrometer captures the interference spectrum in real time, and the host computer extracts spectral features through fast Fourier transform, combined with a differential noise suppression algorithm to effectively eliminate common-mode interference.

[0004] This utility model is achieved through the following technical solution: a high-sensitivity micro-pressure sensing device based on dual-end Fabry-Perot cavity cascade coupling, the device including a broadband light source, an optical fiber unidirectional isolator, a detection end Fabry-Perot cavity, a reference end Fabry-Perot cavity, a spectrometer and a host computer;

[0005] The broadband light source (1) described in this utility model has a working wavelength range of 1550~1650 nm;

[0006] The fiber optic unidirectional isolator (2) of this utility model suppresses back reflection light to protect the light source, and is connected to the output end of the broadband light source (1);

[0007] The 2×2 fiber coupler (3) of this utility model has a splitting ratio of 50:50 and an insertion loss of ≤0.2 dB. The first input end is connected to a fiber optic unidirectional isolator, the second input end is connected to a spectrometer, and the two output ends are respectively connected to the detection end (4) and the reference end (5) Fabry-Perot cavity.

[0008] The detection end Fabry-Perot cavity (4) of this utility model is composed of a corrugated diaphragm (406) and a metal film (405) plated on its surface, and a single-mode fiber end face (403) to form a pressure-sensitive cavity with a cavity length of 50~300 μm;

[0009] The reference end Fabry-Perot cavity (5) of this invention is a fixed cavity formed by a fused silica substrate (505) and the end face of a single-mode optical fiber (503), and the cavity length has an error of ≤1% compared with the initial cavity length of the detection end;

[0010] The spectrometer (6) of this invention has a resolution of ≤0.01 nm and is connected to the second input end of the fiber optic coupler, which can capture cascaded interference spectra in real time.

[0011] The host computer (7) of this utility model is connected to the spectrometer and is an industrial control computer with a built-in phase demodulation unit. It demodulates the pressure signal through fast Fourier transform and differential algorithm and outputs a high-precision pressure value.

[0012] The output light of the broadband light source (1) enters the coupler (3) through the fiber optic unidirectional isolator (2), and after being split, it enters the detection end (4) and reference end (5) cavities respectively. Both cavities interfere with each other, and the free spectral ranges are FSR1 and FSR2 respectively. When the external pressure causes the cavity length of the detection end to change, the interference of the detection end undergoes phase modulation. The reference end fixed cavity isolates temperature and vibration interference. The host computer (7) eliminates noise through fast Fourier transform and differential algorithm and outputs a high-precision pressure value.

[0013] The beneficial effects of this invention are as follows: the dual-cavity cascaded interference amplification effect amplifies the pressure sensitivity; the vernier effect converts the minute optical path change caused by pressure into a significant spectral shift, achieving a sensitivity of 0.8 nm / kPa; the reference cavity synchronously compensates for interferences such as temperature and vibration; the all-fiber passive design avoids electromagnetic interference; and the use of a gold-plated corrugated diaphragm and quartz substrate improves long-term stability; there are no discrete components, making it suitable for confined spaces (such as medical catheters or embedded in industrial pipes); in addition, the fused silica substrate and metal coating design delay material aging and adapt to high humidity and high temperature environments. Attached Figure Description

[0014] Figure 1 : Schematic diagram of the overall structure of the device, showing the connection relationship between the broadband light source (1), the fiber optic unidirectional isolator (2), the 2×2 coupler (3), the detection end Fabry-Perot cavity (4), the reference end Fabry-Perot cavity (5), the spectrometer (6), and the host computer (7);

[0015] Figure 2 : Detailed diagram of the detection end cavity, including single-mode fiber (401), metal sleeve (402), fiber end face (403), Fabry-Perot cavity (404), metal coating layer (405) and corrugated diaphragm (406).

[0016] Figure 3 : Referring to the detailed diagram of the end cavity, the single-mode fiber (501), the metal sleeve (502), the fiber end face (503), the Fabry-Perot cavity (504), and the corrugated diaphragm (505).

[0017] Figure 4 : Spectral shift of the Fabry-Perot cavity (4) before and after pressure application at the detection end;

[0018] Figure 5 Compare the spectral shift interferograms of the cascaded system before and after the change in pressure. Detailed Implementation

[0019] The overall structure of the device is as follows: Figure 1 As shown, it includes a broadband light source, a fiber optic unidirectional isolator, a 2×2 fiber optic coupler, a Fabry-Perot cavity at the detection end, a Fabry-Perot cavity at the reference end, a spectrometer, and a data processing host computer, and demonstrates the connection relationships of each optical component.

[0020] The broadband light source described in this invention operates in the wavelength range of 1550 to 1650 nm, providing a continuous spectral width and stable power input light source to ensure the stability of the interference signal.

[0021] The light in this invention enters a 2×2 fiber coupler after passing through a fiber optic unidirectional isolator. The coupler has a splitting ratio of 50:50 and an insertion loss of no more than 0.2 dB, ensuring that the optical power is distributed to the two interference cavities at the detection end and the reference end to the maximum possible and even distribution.

[0022] The fabrication of the Fabry-Perot cavity at the detection end described in this invention is as follows: Figure 2 As shown, the pressure-sensitive cavity is composed of a highly elastic corrugated diaphragm and a precision-ground single-mode fiber end face. The diaphragm is made of 316L medical-grade stainless steel with a thickness of 50nm, which has good mechanical response characteristics and corrosion resistance. The diaphragm surface is coated with a metal film with a reflectivity of 99.5% to enhance reflection efficiency and improve interference contrast. The surface roughness is <1.5 angstroms, and the cavity length is precisely controlled at 300 μm to ensure the formation of a stable optical path difference.

[0023] The present invention is as follows: Figure 3 The reference end Fabry-Perot cavity shown uses a fused silica substrate and a single-mode fiber end face to form a fixed cavity. The cavity length is set to 300 μm, with the cavity length error controlled within 0.7%. The coefficient of thermal expansion of the silica substrate is 0.3 × 10⁻⁶. -6 With a temperature of ℃, a reflectivity of 99.998%, and a surface roughness of <1 angstrom, it possesses excellent temperature stability and is used to compensate for the effects of external temperature fluctuations and mechanical vibrations on the interference phase.

[0024] During optical path operation, broadband light enters the coupler via an isolator and is then directed into the detection and reference cavities respectively. Reflected interference light is generated in each cavity, and the interference light is then superimposed and returned via the coupler. Finally, the interference spectrum signal is acquired by a high-resolution spectrometer. The slight difference in cavity length between the two cavities results in slightly different Free Speed ​​Reductions (FSRs), denoted as FSR1 and FSR2 respectively. When FSR1 and FSR2 are close in size, a distinct interference envelope structure can be formed. For example... Figure 5 As shown, under external pressure, the length of the detection cavity changes slightly, causing a measurable phase shift in the interference spectrum, while the reference cavity remains stable, achieving a differential compensation effect and effectively suppressing the influence of non-target signals such as temperature drift and mechanical disturbance on the interference spectrum.

[0025] The interference spectrum described in this invention is acquired by a spectrometer and input to a host computer system. The host computer system is an industrial control computer with a built-in phase demodulation unit. Based on the Fast Fourier Transform algorithm, it performs frequency domain analysis on the interference spectrum, extracts the phase information of the interference fringes, and combines a differential algorithm to perform real-time comparison between the signals at the detection end and the reference end, filtering out system noise and background interference, thereby achieving high-precision pressure signal demodulation. In the test environment of this embodiment, the pressure variation range is 0~100 kPa, and the system sensitivity can reach 0.8 nm / kPa, far exceeding the performance of traditional single-cavity structure sensors. The system signal-to-noise ratio is improved by 22 dB, and the temperature drift is controlled within 0.012% FS, demonstrating excellent anti-disturbance capability and environmental adaptability.

[0026] Furthermore, the sensing device described in this invention adopts an all-fiber structure, eliminating the need for external power supplies or electronic components for signal conversion, thus avoiding the influence of electromagnetic interference and making it suitable for applications with complex electromagnetic environments. Simultaneously, the air gap-free design eliminates the unnecessary reflections and optical losses caused by air gaps in traditional fiber optic sensors, improving the system's steady-state response and long-term stability. The device has a compact overall structure, facilitating miniaturization, packaging, and modular integration, making it particularly suitable for pressure sensing tasks in confined spaces such as industrial pipe embedding and medical catheter implantation.

[0027] Regarding long-term operational stability, the device described in this invention, through the use of a fused silica substrate and metal coating, significantly suppresses the impact of material aging and environmental corrosion on optical parameters, ensuring that the sensor maintains excellent performance even under high humidity, high temperature, and vibration conditions. The system supports online calibration and remote data transmission, and can seamlessly interface with industrial control systems or medical monitoring platforms via fiber optic communication, possessing good scalability and secondary development capabilities. Under different environmental conditions, the sensor sensitivity and measurement range can be flexibly adjusted by modifying the initial cavity length of the detection chamber, the diaphragm thickness, and the coating material, thereby further expanding its application prospects in high-precision fluid dynamics experiments, aerospace micro-pressure measurement, and bio-implantable sensing.

[0028] In summary, this embodiment constructs a fiber optic pressure sensing system with high sensitivity, strong anti-interference capability, and good stability by combining a double-ended Fabry-Perot cavity structure with the vernier interference effect. This system not only achieves miniaturization and integration in its structural design but also breaks through the limitations of traditional single-cavity structures in terms of performance indicators, demonstrating broad application potential in modern high-precision measurement scenarios. Its technical solution fully embodies the innovative value of integrating novel fiber optic sensing technology in the industrial and medical fields, possessing significant practicality and promotional value.

[0029] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A high-sensitivity micro-pressure sensing device based on a dual-ended Fabry-Perot cavity cascade coupling, characterized in that, include: A broadband light source is used to provide broadband continuous light input, with an operating wavelength range of 1550~1650 nm; a fiber optic unidirectional isolator is connected to the output end of the broadband light source to suppress back-reflected light and protect the light source; the first input end of the 2×2 fiber optic coupler is connected to the fiber optic unidirectional isolator, the second input end is connected to the spectrometer, and the two output ends are respectively connected to the detection end Fabry-Perot cavity and the reference end Fabry-Perot cavity; The Fabry-Perot cavity at the detection end consists of a corrugated diaphragm and a single-mode fiber end face forming a pressure-sensitive cavity with a length of 300~500 μm; the Fabry-Perot cavity at the reference end consists of a fused silica substrate and a single-mode fiber end face forming a fixed cavity with a length error of ≤1% compared to the initial cavity length at the detection end; the spectrometer is connected to the second input end of the fiber coupler to capture cascaded interference spectra; the host computer is connected to the spectrometer and outputs pressure values ​​through a phase demodulation algorithm.

2. The apparatus according to claim 1, characterized in that: The corrugated diaphragm material of the Fabry-Perot cavity at the detection end is 316L stainless steel, with a thickness of 10~50 μm, and its surface is coated with a high-reflectivity metal film with a reflectivity ≥98%; the coefficient of thermal expansion of the fused silica substrate of the Fabry-Perot cavity at the reference end is ≤0.5×10⁻⁶. -6 / ℃.

3. The apparatus according to claim 1, characterized in that: The 2×2 fiber coupler has a splitting ratio of 50:50 and an insertion loss of ≤0.2 dB.

4. The apparatus according to claim 1, characterized in that: The spectrometer has a resolution of ≤0.01 nm and supports real-time acquisition frequency of ≥1 kHz.

5. The apparatus according to claim 1, characterized in that: The sensitivity of the cavity length variation of the detection end Fabry-Perot cavity is 0.5~1.2 nm / kPa; the temperature drift compensation accuracy of the reference end Fabry-Perot cavity is ≤0.015% FS.

6. The apparatus according to claim 1, characterized in that: The host computer is an industrial control computer with a built-in phase demodulation unit. It demodulates the pressure signal through fast Fourier transform and differential algorithm to output a high-precision pressure value.

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