A kind of cascaded MZI double-parameter sensing device based on vernier effect and preparation method

Abstract

This invention discloses a cascaded MZI dual-parameter sensing device and its fabrication method based on the vernier effect, belonging to the field of fiber optic sensor technology. The device is constructed by sequentially fusing a first single-mode fiber, a first tapered few-mode fiber, a second single-mode fiber, a second tapered few-mode fiber, and a third single-mode fiber. A Mach-Zehnder interferometer is constructed by tapering the few-mode fibers, and a dual-interferometer structure is formed through cascading, utilizing the vernier effect to amplify the spectral response. This structure effectively enhances the effect of the measured parameters, significantly improves the detection sensitivity for temperature and stress, while reducing size and cost. This invention has a simple and reliable structure, is easy to deploy in complex environments, and can be widely applied in fields such as geological monitoring and structural safety inspection, possessing good prospects for technological transformation and social benefits.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensor technology, and in particular to a cascaded MZI dual-parameter sensing device based on the vernier effect and its fabrication method. Background Technology

[0002] With the rapid development of science and technology, fiber optic sensing technology has transitioned from theoretical foundation to practical application. Fiber optic sensors based on an all-fiber structure have advantages such as small size, high sensitivity, low cost, corrosion resistance, and resistance to electromagnetic interference, thus possessing significant practical application value in various fields such as geological monitoring, environmental management, and chemical production.

[0003] In real-world testing environments, fiber optic sensing signals are often influenced by multiple physical parameters, with temperature and stress being the two most common. Especially in fields such as geological monitoring and structural safety inspection, detecting a single variable often fails to meet the demands of complex environments. Therefore, sensors capable of simultaneously detecting both temperature and stress have become a research hotspot.

[0004] Currently, the Mach-Zehnder interferometer (MZI) is one of the most commonly used interferometric structures in fiber optic sensing systems. Traditional MZI sensors are typically constructed using coaxial fusion splicing or by fabricating miniature sensing devices on ordinary single-mode optical fibers using tapering operations. These sensors are relatively simple to fabricate and can improve the detection sensitivity for temperature and stress to some extent. However, existing traditional MZI sensors based on single-mode optical fibers still have the following shortcomings: Limited sensitivity: The sensitivity of a single interferometer is limited, making it difficult to meet the requirements of high-precision measurement; Intermodal coupling problem: Ordinary optical fibers are prone to unstable intermodal coupling when exciting higher-order modes, which affects the stability of sensing signals; Demodulation difficulties: The interference spectrum generated by the traditional structure has a small period, is not significant enough to respond to small changes in the external environment, and is easily affected by noise. Summary of the Invention

[0005] The purpose of this invention is to provide a cascaded MZI dual-parameter sensing device based on the vernier effect and its preparation method, aiming to solve or improve at least one of the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following solution: A cascaded MZI dual-parameter sensing device based on the vernier effect, comprising: The first single-mode fiber, the first tapered few-mode fiber, the second single-mode fiber, the second tapered few-mode fiber, and the third single-mode fiber are sequentially connected by fusion splicing.

[0007] Furthermore, the first tapered few-mode fiber and the second tapered few-mode fiber are obtained by tapering the central region of the few-mode fiber (FMF).

[0008] Furthermore, the length of the few-mode fiber (FMF) is 3 cm.

[0009] Furthermore, the diameters of the first tapered few-mode fiber and the second tapered few-mode fiber are 5 μm and 4.8 μm, respectively.

[0010] A method for manufacturing the above-mentioned sensing device includes: S1, the two ends of the few-mode fiber (FMF) are fused with the single-mode fiber (SMF) using a fiber fusion splicer to generate an SMF-FMF-SMF fiber structure; S2, Taper the central region of the few-mode fiber FMF in the SMF-FMF-SMF fiber structure to obtain a tapered few-mode fiber, thus obtaining the STFS fiber structure; S3. The single-mode fibers (SMFs) at both ends of two STFS fiber structures are fused together by the discharge operation of a fusion splicer to prepare a cascaded MZI dual-parameter sensing device.

[0011] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention discloses a cascaded MZI dual-parameter sensing device based on the vernier effect and its fabrication method. The device utilizes a tapering method to construct a sensor based on an MZI interferometer structure from few-mode optical fibers, and then cascades these fibers to create a dual-interferometer structure. The tapering of the few-mode fiber effectively enhances the effect of the measured parameter, and the dual-interferometer structure further amplifies this effect, significantly improving the response sensitivity. The dual-interferometer structure effectively reduces the size of the sensing device and lowers its manufacturing cost. The overall structure is simple, reliable, and easy to deploy in complex environments.

[0012] This invention can easily and conveniently detect two parameters, temperature and stress, and has a good foundation for technological transformation. It is expected to be widely used in practical applications such as geological monitoring and structural safety inspection. This invention can promote the application of fiber optic misalignment devices and achieve broad social benefits. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the sensing device of the present invention; Figure 2 This is a schematic diagram of the working process of the sensing device in this embodiment; Figure 3 This is a schematic diagram of the temperature sensing effect of the sensing device in this embodiment; Figure 4 This is a schematic diagram of the stress sensing effect of the sensing device in this embodiment; In the figure, 1 is the first single-mode fiber; 2 is the first tapered few-mode fiber; 3 is the second single-mode fiber; 4 is the second tapered few-mode fiber; 5 is the third single-mode fiber; 6 is the supercontinuum light source; and 7 is the spectrometer. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The purpose of this invention is to provide a cascaded MZI dual-parameter sensing device based on the vernier effect and its preparation method, aiming to solve or improve at least one of the above-mentioned technical problems.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, the present invention provides a cascaded MZI dual-parameter sensing device based on the vernier effect, comprising: a first single-mode fiber 1, a first tapered few-mode fiber 2, a second single-mode fiber 3, a second tapered few-mode fiber 4, and a third single-mode fiber 5 connected sequentially by fusion splicing.

[0019] In one embodiment, the first tapered few-mode fiber 2 and the second tapered few-mode fiber 4 are obtained by tapering the central region of the few-mode fiber FMF. Furthermore, the length of the few-mode fiber FMF is 3 cm.

[0020] In one embodiment, the diameters of the first tapered few-mode fiber 2 and the second tapered few-mode fiber 4 are 5 μm and 4.8 μm, respectively.

[0021] In one embodiment, the present invention provides a method for manufacturing the above-mentioned sensor device, comprising: S1, the two ends of the few-mode fiber (FMF) are fused with the single-mode fiber (SMF) using a fiber fusion splicer to generate an SMF-FMF-SMF fiber structure; S2, Taper the central region of the few-mode fiber FMF in the SMF-FMF-SMF fiber structure to obtain a tapered few-mode fiber, thus obtaining the STFS fiber structure; S3. The single-mode fibers (SMFs) at both ends of two STFS fiber structures are fused together by the discharge operation of a fusion splicer to prepare a cascaded MZI dual-parameter sensing device.

[0022] In the above-mentioned preparation method, tapering was performed, which led to the reorganization of the mode distribution inside the fiber, thereby exciting higher-order modes. The higher-order modes accumulated optical path difference as they passed through the waist region and were recoupled in the subsequent non-tapered region, thus forming a complete Mach-Zehnder interferometer.

[0023] Due to the precise control of the cone diameter, the FSR of the interference spectra produced by the two interferometers are very similar but not exactly the same. At this time, the two interference spectra are superimposed to achieve the optical vernier effect, which can greatly improve the detection sensitivity of temperature and stress dual parameters.

[0024] like Figure 2 As shown, the working process of the cascaded MZI dual-parameter sensor is as follows: The light emitted by the supercontinuum light source 6 is input through the first single-mode fiber 1, passes sequentially through the first tapered few-mode fiber 2 and the single-mode fiber 3 which serves as an intermediate connecting arm, and enters the second tapered few-mode fiber 4. During this process, the comb-shaped spectra generated are superimposed to form a vernier effect envelope spectrum. Finally, the modulated light signal carrying external environmental parameter information is exported through the third single-mode fiber 5 and coupled to the spectrometer 7 for demodulation analysis.

[0025] During the sensing process, the first tapered few-mode fiber 2 serves as a reference arm and is not used for sensing; the second tapered few-mode fiber 4 serves as the sensing part and is used for the detection of temperature and stress dual parameters.

[0026] Because quartz optical fiber itself has temperature-sensitive properties, temperature changes cause a shift in the sensing spectrum. Temperature detection can be achieved by analyzing the relationship between temperature changes and spectral shifts. For example... Figure 3 As shown in the figure, the temperature sensing effect of the sensing device is 3.362 nm / ℃, which is 8 times higher than that of single-peak measurement.

[0027] Meanwhile, few-mode fiber (FMF) becomes extremely thin after tapering, altering the internal stress and enhancing the photoelastic effect. When external stress changes, the stress difference between the internal and external fibers causes a change in the optical path difference, leading to a shift in the interference spectrum. For example... Figure 4 As shown in the figure, the stress sensing effect of the sensing device reaches 262.7 pm / με, which is 6 times higher than that of single-peak measurement.

[0028] By measuring the transmission spectrum under arbitrary temperature and stress conditions, the vernier spectral envelope can be used to improve the sensing sensitivity. At the same time, a dual-parameter transmission matrix can be constructed using the multi-point sensitivity parameters of the spectral envelope to achieve real-time detection of temperature and stress.

[0029] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0030] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A cascaded MZI dual-parameter sensing device based on Vernier effect, characterized in that, include: The first single-mode fiber (1), the first tapered few-mode fiber (2), the second single-mode fiber (3), the second tapered few-mode fiber (4), and the third single-mode fiber (5) are sequentially connected by fusion splicing.

2. The cascaded MZI dual-parameter sensing device based on the vernier effect according to claim 1, characterized in that, The first tapered few-mode fiber (2) and the second tapered few-mode fiber (4) are obtained by tapering the central region of the few-mode fiber (FMF).

3. The cascaded MZI dual-parameter sensing device based on the vernier effect according to claim 1, characterized in that, The length of the few-mode fiber (FMF) is 3 cm.

4. The cascaded MZI dual-parameter sensing device based on the vernier effect according to claim 1, characterized in that, The diameters of the first tapered few-mode fiber (2) and the second tapered few-mode fiber (4) are 5 μm and 4.8 μm, respectively.

5. A method for manufacturing the sensing device according to any one of claims 1-4, characterized in that, include: S1, the two ends of the few-mode fiber (FMF) are fused with the single-mode fiber (SMF) using a fiber fusion splicer to generate an SMF-FMF-SMF fiber structure; S2, Taper the central region of the few-mode fiber FMF in the SMF-FMF-SMF fiber structure to obtain a tapered few-mode fiber, thus obtaining the STFS fiber structure; S3. The single-mode fibers (SMFs) at both ends of two STFS fiber structures are fused together by the discharge operation of a fusion splicer to prepare a cascaded MZI dual-parameter sensing device.

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