A method for preparing a fiber-optic Mach-Zehnder interferometer based on light induction technology

Abstract

The application belongs to the technical field of optical fiber sensing, and particularly relates to a preparation method of a fiber Mach-Zehnder interferometer based on light induction technology, which comprises the following steps: firstly, cutting a certain length of three groups of hollow optical fibers and two groups of single-mode optical fibers by using an optical fiber cutter; and alternately splicing; then, drilling holes in the side walls of the hollow optical fibers by using a carbon dioxide laser, dropping a light-polymerizable solution into the holes, inputting the solution into a transmission optical fiber, and performing laser irradiation to obtain a first light polymer column; flushing the un-solidified light-polymerizable solution with alcohol; finally, filling PDMS into the hollow optical fiber of a second light polymer column by using the side holes of the hollow optical fiber and a vacuum suction device, and keeping constant temperature for solidification to obtain a second light polymer column filled with PDMS hollow optical fiber, and finally obtaining the fiber Mach-Zehnder interferometer. The application has the advantages of compact structure, good stability, low manufacturing cost, and temperature sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing technology, specifically relating to a method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology. Background Technology

[0002] High-sensitivity fiber optic temperature sensors play an indispensable role in fields such as biomedicine, aerospace, power systems, and marine development. Compared to electronic sensors, fiber optic sensors have advantages such as small size, high sensitivity, strong resistance to electromagnetic interference, and long transmission distance. In recent years, various fiber optic temperature sensors have been developed to improve detection sensitivity. The working principles of these devices are mainly based on fiber Bragg gratings (FBG), long-period fiber gratings (LFPG), Fabry-Poirot interferometers (FPI), and Mach-Zehnder interferometers (MZI).

[0003] Due to the significant advantages of MZI-based sensors, such as simple fabrication, low cost, and high sensitivity, they have attracted considerable research interest in the field of fiber optic sensing. However, temperature sensitivity sensors based on all-fiber MZI are still limited by the low thermo-optic coefficient (TOC) and thermal expansion coefficient (TEC) of silica fibers. Therefore, the temperature detection sensitivity of existing fiber optic Mach-Zehnder interferometers needs to be improved, while the manufacturing cost is slightly high. To overcome this limitation and improve temperature detection sensitivity while reducing manufacturing costs, polydimethylsiloxane (PDMS) is selected to improve temperature sensitivity. This is because PDMS is a transparent polymer with siloxane chains as the main chain and methyl groups as side chains. Cured PDMS has advantages such as high TOC and TEC, non-toxicity, high chemical inertness, and easy integration with microstructures. At the same time, fiber-to-the-end photopolymerization (FEP) technology can be used to grow photopolymer pillars at the ends of optical fibers. A photopolymerizable solution is selected, stimulated by a fiber semiconductor laser, and then cured. This technology has broad application prospects in biomimetic fiber optic sensors and fiber optic sensors for measuring physical parameters. Summary of the Invention

[0004] The purpose of this invention is to provide a method for fabricating a fiber optic Mach-Zehnder interferometer based on optically induced technology. The method involves sequentially fusing the various optical fibers using a fiber optic fusion splicer and a fiber optic cleaver, drilling holes in the sidewalls of the hollow optical fibers using a carbon dioxide laser, dripping in a photopolymerizable solution, and then curing it using a fiber semiconductor laser with a center wavelength of 520 nm. The cross-sectional diameter of the photopolymerized column is adjusted by both the laser power and the exposure time, and is mainly modulated by the power of the fiber semiconductor laser when growing a photopolymerized column of a fixed length. As is well known, the output energy field of optical fiber has a Gaussian-like distribution, with energy gradually decreasing from the center to the edge. Although higher-order modes exist in standard communication SMFs, an approximate Gaussian emission field was still obtained through mechanical frequency scrambling, and a photopolymerizable column was solidified. The uncured photopolymerizable solution was rinsed with alcohol, and PDMS was filled into a 150µm long hollow optical fiber using a vacuum suction device and cured at 60°C for 3 hours. The PDMS filled in the hollow optical fiber using the vacuum suction device has no air cavity. When the ambient temperature changes, the high TOC of PDMS causes a significant change in the effective RI of the mode, improving temperature detection sensitivity. The fiber Mach-Zehnder interferometer obtained by the provided method has a compact structure, good stability, low manufacturing cost, and high temperature sensitivity, making it more competitive than traditional all-fiber MZ interferometers in the future.

[0005] The specific technical solution adopted by this invention is as follows:

[0006] A method for fabricating a fiber optic Mach-Zehnder interferometer based on optically induced technology includes the following steps:

[0007] S1: Use a fiber optic cleaver to cut a certain length of first hollow fiber, second hollow fiber, third hollow fiber, first single-mode fiber, and second single-mode fiber.

[0008] S2: Use a fiber optic fusion splicer to alternately splice three sets of hollow optical fibers with two sets of single-mode optical fibers;

[0009] S3: Use a fiber optic fusion splicer to splice the input transmission fiber at the end of the first hollow fiber; and splice the output transmission fiber at the end of the third hollow fiber;

[0010] S4: Using a carbon dioxide laser, a hole is drilled in the sidewall of the first hollow fiber. A photopolymerizable solution is dropped into the input transmission fiber and irradiated with laser light. The photopolymerizable solution grows from the core of the input transmission fiber and bonds to the first single-mode fiber, resulting in a first photopolymer column. The uncured photopolymerizable solution is rinsed with alcohol. Step S4 is repeated to grow corresponding second and third photopolymer columns on the other two sets of hollow fibers, resulting in first photopolymer column hollow fibers, second photopolymer column hollow fibers, and third photopolymer column hollow fibers.

[0011] S5: Using the hollow fiber side hole and vacuum suction device in step 4, PDMS is filled into the second optical polymer cylinder hollow fiber and cured at a constant temperature to obtain the second optical polymer cylinder filled with PDMS hollow fiber 5, and finally the fiber Mach-Zehnder interferometer is obtained.

[0012] In step S1, the lengths of the first hollow fiber and the third hollow fiber are 30 μm; the length of the second hollow fiber is 150 μm; and the lengths of the first single-mode fiber and the second single-mode fiber are 200-600 μm.

[0013] The splicing sequence in step S2 is: first hollow fiber, first single-mode fiber, second hollow fiber, second single-mode fiber, and third hollow fiber.

[0014] In step S4, a broadband light source is connected to the other end of the input transmission fiber, and a spectrometer is connected to the other end of the output transmission fiber.

[0015] In step S4, the broadband light source acts as a fiber semiconductor laser, injecting a 520nm wavelength fiber semiconductor laser into the input transmission fiber to assist in laser irradiation.

[0016] In step S4, after filling the hollow optical fiber of the second optical polymer column with PDMS, it is cured at a constant temperature of 60°C for three hours.

[0017] Both the input transmission fiber and the output transmission fiber are single-mode fibers.

[0018] The inner diameter of the input transmission fiber, the first single-mode fiber, the second single-mode fiber, and the output transmission fiber is 9 μm, and the outer diameter of the fiber is 125 μm.

[0019] The inner diameter of the first optical polymer cylindrical hollow optical fiber, the second optical polymer cylindrical filled PDMS hollow optical fiber, and the third optical polymer cylindrical hollow optical fiber is 75 μm, and the outer diameter of the optical fiber is 125 μm.

[0020] The technical effects achieved by this invention are as follows:

[0021] The present invention discloses a method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology. The method involves sequentially fusing the various optical fibers using an optical fiber fusion splicer and an optical fiber cleaver, drilling holes in the sidewalls of the hollow optical fibers using a carbon dioxide laser, dripping in a photopolymerizable solution, and then curing it using a fiber semiconductor laser with a center wavelength of 520 nm. The cross-sectional diameter of the photopolymerized column is adjusted by both the laser power and the exposure time, and is mainly modulated by the power of the fiber semiconductor laser when growing a photopolymerized column of a fixed length. As is well known, the output energy field of optical fiber has a Gaussian-like distribution, with energy gradually decreasing from the center to the edge. Although higher-order modes exist in standard communication SMF, an approximate Gaussian emission field was still obtained through mechanical frequency scrambling, and a solidified photopolymerizable column was achieved. The uncured photopolymerizable solution was rinsed with alcohol, and PDMS was filled into a 150µm hollow optical fiber using a vacuum suction device and cured at 60°C for 3 hours. The PDMS filled in the hollow optical fiber using the vacuum suction device has no air cavity. When the ambient temperature changes, the effective RI of the mode changes greatly due to the high TOC of PDMS, thus improving the temperature detection sensitivity. The fiber MZ interferometer obtained by the provided preparation method has a compact structure, good stability, low manufacturing cost, and high temperature sensitivity, making it more competitive than traditional all-fiber MZ interferometers in the future. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the fiber optic Mach-Zehnder interferometer in this invention;

[0023] Figure 2 This is a top view of the fiber optic Mach-Zehnder interferometer in this invention.

[0024] Figure 3 This is a schematic diagram of the orthographic structure of the fiber optic Mach-Zehnder interferometer in this invention;

[0025] Figure 4 This is a schematic diagram of the cross-sectional structure of the optical fiber in this invention, which consists of three sets of hollow optical fibers and two sets of single-mode optical fibers, spliced ​​alternately.

[0026] Figure 5 This is a flowchart of a method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to the present invention.

[0027] The attached diagram lists the components represented by each number as follows:

[0028] 1. Broadband light source; 2. Input transmission fiber; 3. First optical polymer cylindrical hollow fiber; 4. First single-mode fiber; 5. Second optical polymer cylindrical PDMS-filled hollow fiber; 6. Second single-mode fiber; 7. Third optical polymer cylindrical hollow fiber; 8. Output transmission fiber; 9. Spectrometer; 10. Drilling holes in the sidewall of the first hollow fiber; 11. Drilling holes in the sidewall of the second hollow fiber; 12. Drilling holes in the sidewall of the third hollow fiber; 13. First optical polymer cylinder; 14. Second optical polymer cylinder; 15. Third optical polymer cylinder; 16. PDMS. Detailed Implementation

[0029] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0030] like Figure 1-5 As shown, a method for fabricating a fiber optic Mach-Zehnder interferometer based on optically induced technology includes the following steps:

[0031] S1: Use a fiber optic cleaver to cut a certain length of the first hollow fiber, the second hollow fiber, the third hollow fiber, the first single-mode fiber 4, and the second single-mode fiber 6.

[0032] S2: Use a fiber optic fusion splicer to alternately splice three sets of hollow optical fibers with two sets of single-mode optical fibers;

[0033] S3: Use a fiber optic fusion splicer to splice the input transmission fiber 2 at the end of the first hollow fiber; and splice the output transmission fiber 8 at the end of the third hollow fiber;

[0034] like Figure 4 As shown, S4: A hole is drilled in the sidewall of the first hollow fiber using a carbon dioxide laser, and a photopolymerizable solution is dropped into it. The solution is then irradiated with laser through the input transmission fiber 2. The photopolymerizable solution grows from the core of the input transmission fiber 2 and adheres to the first single-mode fiber 4, resulting in a first photopolymer column 13. The uncured photopolymerizable solution is rinsed with alcohol. Step S4 is repeated to grow corresponding second photopolymer columns 14 and third photopolymer columns 15 on the other two sets of hollow fibers, resulting in first photopolymer column hollow fiber 3, second photopolymer column hollow fiber, and third photopolymer column hollow fiber 7.

[0035] like Figure 4As shown, specifically, firstly, a hole 10 is drilled in the sidewall of the first hollow fiber using a carbon dioxide laser. Then, a photopolymerizable solution is dripped into the interior of the first hollow fiber through the hole 10. Next, a broadband light source 1, acting as a fiber semiconductor laser, injects a 520nm wavelength fiber semiconductor laser into the input transmission fiber 2. Through the input transmission fiber 2, laser irradiation causes the photopolymerizable solution to grow from the core of the input transmission fiber 2 and bond to the first single-mode fiber 4, resulting in a first photopolymer column 13. The uncured photopolymerizable solution is then rinsed with alcohol to obtain the first photopolymer column hollow fiber 3. Finally, a hole 11 is drilled in the sidewall of the second hollow fiber using a carbon dioxide laser, and similarly, holes are drilled in the sidewall of the second hollow fiber. 11. A photopolymerizable solution is dripped into the interior of the second hollow fiber, and then laser irradiation is performed. The photopolymerizable solution grows from the core of the first single-mode fiber 4 and adheres to the second single-mode fiber 6, resulting in a second photopolymer column 14. The uncured photopolymerizable solution is rinsed with alcohol, resulting in a second photopolymer column hollow fiber. Finally, a hole 12 is drilled in the sidewall of the third hollow fiber using a carbon dioxide laser. A photopolymerizable solution is dripped into the interior of the third hollow fiber through the hole 12, and then laser irradiation is performed. The photopolymerizable solution grows from the core of the second single-mode fiber 6 and adheres to the output transmission fiber 8, resulting in a third photopolymer column 15. The uncured photopolymerizable solution is rinsed with alcohol, resulting in a third photopolymer column hollow fiber 7.

[0036] like Figure 4 As shown, S5: Using the hollow fiber side hole and vacuum suction equipment in step 4, PDMS16 is filled into the hollow fiber of the second optical polymer cylinder and cured at a constant temperature to obtain the second optical polymer cylinder filled with PDMS hollow fiber 5, and finally the fiber Mach-Zehnder interferometer is obtained.

[0037] like Figure 4 As shown, it is worth mentioning that when the ambient temperature changes, the high TOC of PDMS causes a significant change in the effective RI of the mode, thus improving the temperature detection sensitivity. The fiber MZ interferometer obtained by the provided fabrication method has a compact structure, good stability, low manufacturing cost, and high temperature sensitivity, making it more competitive than traditional all-fiber MZ interferometers in the future.

[0038] In step S1, the lengths of the first hollow fiber and the third hollow fiber are 30 μm; the length of the second hollow fiber is 150 μm; and the lengths of the first single-mode fiber 4 and the second single-mode fiber 6 are 200-600 μm.

[0039] like Figure 3As shown, the splicing order in step S2 is: first hollow fiber, first single-mode fiber 4, second hollow fiber, second single-mode fiber 6, and third hollow fiber.

[0040] like Figure 3 As shown, in step S4, a broadband light source 1 is connected to the other end of the input transmission fiber 2, and a spectrum analyzer 9 is connected to the other end of the output transmission fiber 8.

[0041] like Figure 3 As shown, in step S4, the broadband light source 1 acts as a fiber semiconductor laser, injecting a 520nm wavelength fiber semiconductor laser into the input transmission fiber 2 to assist in laser irradiation.

[0042] like Figure 4 As shown, in step S4, after filling the hollow optical fiber of the second optical polymer column with PDMS16, it is cured at a constant temperature of 60°C for three hours.

[0043] like Figure 4 As shown, it should be added that when PDMS16 is filled into a second hollow optical fiber with a length of 150um using a vacuum suction device and cured at a temperature of 60℃ for 3 hours, the PDMS16 filled in the hollow optical fiber using the vacuum suction device has no air cavity; when the ambient temperature changes, the effective RI of the mode changes greatly due to the high TOC of PDMS, thus improving the temperature detection sensitivity.

[0044] like Figure 2 As shown, both the input transmission fiber 2 and the output transmission fiber 8 are single-mode fibers.

[0045] like Figure 4 As shown, the inner diameter of the input transmission fiber 2, the first single-mode fiber 4, the second single-mode fiber 6, and the output transmission fiber 8 is 9 μm, and the outer diameter of the fiber is 125 μm; the inner diameter of the first optical polymer cylindrical hollow fiber 3, the second optical polymer cylindrical filled PDMS hollow fiber 5, and the third optical polymer cylindrical hollow fiber 7 is 75 μm, and the outer diameter of the fiber is 125 μm.

[0046] like Figure 1-5As shown, the working principle of this invention is as follows: When using a fiber optic Mach-Zehnder interferometer based on optical induction technology, the light emitted by the broadband light source 1 propagates along the fiber as the basic mode through the input transmission fiber 2 and enters the first optical polymer cylindrical hollow fiber 3. At this time, the light is split into two parts. One beam of light continues to propagate along the fiber core, while the other beam of light leaks into the cladding of the first single-mode fiber 4 due to the mode field mismatch between the input transmission fiber 2 and the first optical polymer cylindrical hollow fiber 3. The first optical polymer cylindrical hollow fiber 3 and the second optical polymer cylindrical PDMS-filled hollow fiber 5 act as a beam splitter and a beam combiner. When the light enters the second optical polymer cylindrical PDMS-filled hollow fiber 5, the optical polymer cylinder grown by FEP technology serves as a reference arm, and the filled PDMS16 serves as a sensing arm. When the light simultaneously enters the third optical polymer cylindrical hollow fiber 7, the light passing through the reference arm and the sensing arm converges. Due to the difference in refractive index between the reference arm and the sensing arm, a refractive index difference is generated, which in turn generates an optical path difference, forming interference. Finally, the interference spectrum is observed on the spectrometer 9 after passing through the output transmission fiber 8.

[0047] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology, characterized in that: Includes the following steps: S1: Use a fiber optic cleaver to cut a certain length of the first hollow fiber, the second hollow fiber, the third hollow fiber, the first single-mode fiber (4), and the second single-mode fiber (6). S2: Use a fiber optic fusion splicer to alternately splice three sets of hollow optical fibers with two sets of single-mode optical fibers; S3: Use a fiber optic fusion splicer to splice the input transmission fiber (2) at the end of the first hollow fiber; and splice the output transmission fiber (8) at the end of the third hollow fiber. S4: Using a carbon dioxide laser, a hole is drilled in the sidewall of the first hollow fiber, and a photopolymerizable solution is dropped into it. The solution is then irradiated with laser through the input transmission fiber (2). The photopolymerizable solution grows from the core of the input transmission fiber (2) and adheres to the first single-mode fiber (4) to obtain a first photopolymer column (13). Step S4 is repeated to grow corresponding second photopolymer columns (14) and third photopolymer columns (15) on the other two sets of hollow fibers in sequence to obtain the first photopolymer column hollow fiber (3), the second photopolymer column hollow fiber, and the third photopolymer column hollow fiber (7). S5: Using the hollow fiber side hole and vacuum suction device in step S4, PDMS (16) is filled into the second optical polymer cylinder hollow fiber and cured at a constant temperature to obtain the second optical polymer cylinder filled with PDMS hollow fiber (5), and finally the fiber Mach-Zehnder interferometer is obtained.

2. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to claim 1, characterized in that: In step S1, the lengths of the first hollow fiber and the third hollow fiber are 30 μm; the length of the second hollow fiber is 150 μm; and the lengths of the first single-mode fiber (4) and the second single-mode fiber (6) are 200-600 μm.

3. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to claim 1, characterized in that: The splicing sequence in step S2 is: first hollow fiber, first single-mode fiber (4), second hollow fiber, second single-mode fiber (6), and third hollow fiber.

4. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to claim 1, characterized in that: In step S4, a broadband light source (1) is connected to the other end of the input transmission fiber (2), and a spectrum analyzer (9) is connected to the other end of the output transmission fiber (8).

5. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optically induced technology according to claim 4, characterized in that: In step S4, the broadband light source (1) acts as a fiber semiconductor laser, injecting a 520nm wavelength fiber semiconductor laser into the input transmission fiber (2) to assist in laser irradiation.

6. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to claim 1, characterized in that: In step S4, after filling the hollow optical fiber of the second optical polymer column with PDMS (16), it is cured at a constant temperature of 60°C for three hours.

7. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to claim 1, characterized in that: Both the input transmission fiber (2) and the output transmission fiber (8) are single-mode fibers.

8. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to claim 2, characterized in that: The inner diameter of the input transmission fiber (2), the first single-mode fiber (4), the second single-mode fiber (6), and the output transmission fiber (8) is 9 μm, and the outer diameter of the fiber is 125 μm.

9. The method for fabricating a fiber optic Mach-Zehnder interferometer based on optical induction technology according to claim 1, characterized in that: The inner diameter of the first optical polymer cylindrical hollow fiber (3), the second optical polymer cylindrical filled PDMS hollow fiber (5), and the third optical polymer cylindrical hollow fiber (7) is 75 μm, and the outer diameter of the fiber is 125 μm.

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