A tunable optical fiber based on optofluidics and a manufacturing method thereof

Abstract

The application discloses a tunable optical fiber based on optical flow control and a manufacturing method, and belongs to the optical fiber communication field. The tunable optical fiber based on optical flow control comprises an optical fiber main body, the optical fiber main body comprises a fiber core and a cladding, the optical fiber main body is divided into an input section and an output section, and a tuning section is arranged between the input section and the output section; a first micropore penetrating through the optical fiber main body and parallel to the optical fiber main body is arranged in the cladding of the input section and the output section, a second micropore penetrating through the optical fiber main body and parallel to the axial direction of the optical fiber main body is arranged on the tuning section, the tuning section is fused to the input section and the output section at two ends respectively, the second micropore is located between the fiber cores of the input section and the output section and is used for constituting a Fabry-Perot cavity, different refractive index liquid media are injected into the second micropore, the optical length of the Fabry-Perot cavity between the input section and the tuning section is changed, and the output wavelength is tuned.

Description

Technical Field

[0001] This invention relates to the field of optical fiber communication, and more specifically, to a tunable optical fiber based on optical fluid control and its manufacturing method. Background Technology

[0002] Tunable fiber optic devices, as core functional components of modern photonic systems, directly impact the transmission capacity of optical communication networks, the detection accuracy of fiber optic sensing systems, and the performance of spectral analysis instruments due to their flexible wavelength control capabilities. In the field of fiber lasers, tunable fiber not only determines the wavelength range and stability of the output laser but is also crucial for achieving narrow-linewidth, low-noise laser output.

[0003] For example, thermo-optical tuning mechanisms utilize the thermo-optical effect of doped or polymer optical fibers, changing the core refractive index through external temperature control to achieve Bragg wavelength shift. While these devices have a simple structure, their tuning response is limited by the thermal diffusion process, typically on the order of hundreds of milliseconds. They also suffer from poor thermal stability, high power consumption, and susceptibility to thermal drift during long-term operation, making them unsuitable for high-speed dynamic tuning applications.

[0004] Existing tunable fiber technology struggles to achieve optimal performance across key performance indicators such as response speed, tuning range, insertion loss, long-term stability, and system integration. In particular, it lacks effective technical solutions for achieving controllable micropore connectivity at fiber fusion splices and constructing tunable structures with integrated optical-fluidic architectures. Therefore, we propose a tunable fiber based on optofluidic control and its manufacturing method. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] The purpose of this invention is to provide a tunable optical fiber based on optofluidics and its manufacturing method, so as to solve the problems mentioned in the background art.

[0007] 2. Technical Solution

[0008] This invention is achieved through the following technical solution:

[0009] A tunable optical fiber based on optofluidics includes an optical fiber body, the optical fiber body including a core and a cladding, the optical fiber body being divided into an input segment and an output segment, and a tuning segment being provided between the input segment and the output segment;

[0010] The input and output segments have a first micro-hole that penetrates through and is parallel to the fiber core. The tuning segment has a second micro-hole that penetrates through and is parallel to the fiber core axis. The two ends of the tuning segment are fused to the input and output segments, respectively. The second micro-hole is located between the fiber cores of the input and output segments to form a Fabry-Perot cavity.

[0011] The first micropore is connected to the second micropore, and the first micropore and the second micropore are the same size and both are cylindrical. The central axes of the first micropore and the second micropore are offset from each other by a first distance, which satisfies the following constraint:

[0012] D / 3 ≤ ΔL ≤ D / 2, and L / 40 ≤ ΔL ≤ L / 20;

[0013] In the formula, D is the diameter of the first or second micropore, ΔL is the first distance, and L is the length of the second micropore.

[0014] As an optional embodiment of the technical solution in this application, the optical fiber body further includes an injection segment, which is fused to the end of the output segment away from the tuning segment. The end of the injection segment near the output segment has a grinding bevel. The first micro-hole is aligned with the air profile formed by the grinding bevel. The angle between the grinding bevel and the axial direction of the optical fiber body satisfies the following constraints:

[0015] θ = arctan(14ΔL / L);

[0016] In the formula, ΔL is the first distance, and L is the length of the second micropore.

[0017] As an optional solution to the technical solution in this application, the angle between the grinding bevel and the optical fiber body axis is 20°-35°.

[0018] As an optional solution to the technical solution in this application, the first distance is 9-15 micrometers.

[0019] As an optional solution to the technical solution in this application, the length of the second micropore is 300-350 micrometers.

[0020] As an optional solution to the technical solution in this application, a quartz capillary tube perpendicular to the axis of the optical fiber body is connected to the grinding bevel, and the other end of the quartz capillary tube is connected to a needle tube controlled by a microfluidic pump.

[0021] As an optional solution to the technical solution of this application, a 30-50nm gold film is provided at the opposite end of the input segment and the output segment.

[0022] A method for manufacturing tunable optical fiber based on optofluidics includes the following steps:

[0023] S1. A first micro-hole and a second micro-hole, symmetrical about the fiber core, are formed in the cladding of the optical fiber body; the distance between the central axis of the first micro-hole and the second micro-hole and the central axis of the fiber core is 25 micrometers;

[0024] S2. Divide the main body of the optical fiber into three segments, namely: input segment, tuning segment and output segment;

[0025] S3. Deposit a 30-50nm gold film on the end faces of the input and output sections;

[0026] S4. Move the tuning section along the direction from the second micro-hole to the first micro-hole, while keeping the input and output sections stationary, so that the central axis of the second micro-hole on the tuning section moves to a position 9-15 micrometers below the central axis of the first micro-hole on the input and output sections.

[0027] S5. Weld the end faces of the gold-plated films of the input and output sections to both ends of the tuning section respectively.

[0028] S6. Weld an injection section with a ground bevel to the end of the output section away from the tuning section;

[0029] S7. A quartz capillary is vertically fused at the grinding bevel of the injection section, so that the quartz capillary is connected to the first micropore on the output section.

[0030] 3. Beneficial effects

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1) This application sets a second micropore between the fiber cores of the input and output segments and injects liquid media with different refractive indices (such as glycerol-water mixture) into the second micropore, thereby changing the optical length of the Fabry-Perot cavity between the input and tuning segments, and achieving continuous tuning of the output wavelength based on λ=2nL / m. Experiments show that this structure can achieve a wide tuning range of ≥40 nm, the liquid replacement time is about 4-5 minutes, the reflectivity of the fusion splice surface is stable at about 40%, the interference fringes are clear, the tuning response speed is better than the traditional thermo-optical tuning mechanism, and the all-fiber fusion splice structure ensures low insertion loss (≤0.5dB) and long-term working stability.

[0033] 2) This application can prevent liquid from entering the core area of ​​the optical path and reduce bubble interference by fusing a quartz capillary perpendicular to the injection section at the grinding bevel of the injection section; and improve the packaging density.

[0034] 3) This application can be manufactured by using an optical fiber body with a first micro-hole and a second micro-hole, which is split and spliced ​​in a staggered manner. It can be directly processed using a standard optical fiber cleaver and a fusion splicer without the need for customized fixtures or complex calibration, which greatly reduces the difficulty and cost of preparation. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of a tunable optical fiber based on optical fluidization.

[0036] Figure 2 This is a wavelength-reflectivity diagram of a tunable optical fiber based on optofluidics.

[0037] In the figure: 1. Fiber body; 101. Fiber core; 102. Cladding; 103. First micropore; 104. Second micropore; 10. Input segment; 11. Tuning segment; 12. Output segment; 13. Injection segment. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0039] Example 1:

[0040] Please see Figure 1 This embodiment provides a tunable optical fiber based on optofluidics, including an optical fiber body 1, which includes a fiber core 101 and a cladding 102. The optical fiber body 1 is divided into an input segment 10 and an output segment 12, and a tuning segment 11 is provided between the input segment 10 and the output segment 12.

[0041] Preferably, the outer diameter of the fiber body 1 is 125 micrometers, the diameter of the fiber core 101 is 9 micrometers, the length of the input section 10 is 1 cm, which facilitates splicing and encapsulation with standard optical fibers, while reserving sufficient operating space for fluid injection; the length of the tuning section 11 is 300-350 micrometers, which can ensure stable mode selection in a wide tuning range of ≥40nm, and effectively suppress longitudinal mode competition and avoid mode skipping; the length of the output section 12 is 300-350 micrometers, which facilitates splicing with the injection section 13.

[0042] A first micro-hole 103 is formed in the cladding 102 of the input segment 10 and the output segment 12, penetrating and parallel to the optical fiber body 1. A second micro-hole 104 is formed in the tuning segment 11, penetrating and parallel to the axial direction of the optical fiber body 1. The two ends of the tuning segment 11 are fused to the input segment 10 and the output segment 12 respectively. The second micro-hole 104 is located between the fiber core 101 of the input segment 10 and the output segment 12, and is used to form a Fabry-Perot cavity.

[0043] The first micro-hole 103 and the second micro-hole 104 are connected. The first micro-hole 103 and the second micro-hole 104 have the same size and are both cylindrical. The central axes of the first micro-hole 103 and the second micro-hole 104 are offset from each other by a first distance. The first distance satisfies the following constraint:

[0044] D / 3 ≤ ΔL ≤ D / 2, and L / 40 ≤ ΔL ≤ L / 20;

[0045] In the formula, D is the diameter of the first micropore 103 or the second micropore 104, ΔL is the first distance, and L is the length of the second micropore 104.

[0046] Provided that sufficient cladding thickness is maintained between the first micro-hole 103, the second micro-hole 104 and the fiber core 101, the diameters of the first micro-hole 103 and the second micro-hole 104 are typically 25-30 μm. The first micro-hole 103 and the second micro-hole 104 are kept at an appropriate distance from the fiber core 101 so that the injected liquid can sufficiently overlap with the guided wave field in the fiber core 101, thereby significantly changing the optical length of the Fabry-Perot cavity. If D is too small (e.g., <20 μm), the overlap between the fluid and the light field is insufficient, reducing the tuning efficiency; if D is too large (e.g., >40 μm), it may damage the waveguide structure of the fiber core and increase scattering loss. In this application, D=30 μm is preferred.

[0047] By injecting liquid media with different refractive indices into the second micro-hole 104 through the first micro-hole 103, the optical length of the Fabry-Perot cavity between the input section 10 and the tuning section 11 is changed, thereby achieving the tuning of the output wavelength.

[0048] Preferably, the first distance is 9–15 micrometers. Within this range, the time it takes for the liquid to flow from the microfluidic pump into the output section 12 and out of the tuning section 11 is approximately 4 minutes. Combined with the 40% reflectivity of the welded surface, stable interference fringes can be formed, such as... Figure 2 As shown, when the first distance is less than 9 micrometers, the first micropore 103 and the second micropore 104 are almost perfectly aligned, and an effective Fabry-Perot interference cannot be formed; when the first distance is greater than 15 micrometers, although the reflectivity continues to increase, the liquid flow time increases significantly, and the micropore connectivity decreases, affecting the tuning response speed.

[0049] Table 1: Performance Parameter Comparison Table

[0050]

[0051] As a preferred embodiment of the application, the optical fiber body 1 further includes an injection segment 13, which is fused to the end of the output segment 12 away from the tuning segment 11. The end of the injection segment 13 near the output segment 12 has a polishing bevel, and the first micro-hole 103 is aligned with the air profile formed by the polishing bevel. The angle between the polishing bevel and the axial direction of the optical fiber body 1 satisfies the following constraints:

[0052] θ = arctan(14ΔL / L);

[0053] In the formula, ΔL is the first distance, and L is the length of the second micropore 104.

[0054] Preferably, the angle between the grinding bevel and the axial direction of the optical fiber body 1 is 20°-35°.

[0055] Table 2: Comparison of Grinding Angle Parameters

[0056]

[0057] A quartz capillary tube perpendicular to the axis of the optical fiber body 1 is connected to the grinding bevel, and the other end of the quartz capillary tube is connected to a needle tube controlled by a microfluidic pump. This structure has the following advantages: It facilitates fluid integration: the fluid pipeline can be connected perpendicularly to the optical path, avoiding liquid from entering the core area of ​​the optical path and reducing bubble interference; it increases packaging density: it is easy to integrate with microfluidic chips or pump valve systems and is suitable for modular packaging.

[0058] To improve end-face reflectivity, a 30-50nm gold film is provided at the opposite end of both the input section 10 and the output section 12. The 30-50nm gold film thickness scheme achieves the best balance between reflectivity improvement, process feasibility, and photothermal performance: compared to a thin gold film of 10-20nm with a reflectivity of only 15%-30% and excessively high transmittance that prevents the formation of an effective high-reflectivity interface, a 30-50nm thickness can increase reflectivity from 4% to 40%-55%, truly leveraging the wavelength selective enhancement effect of the metal mirror; compared to a thick gold film of 60nm or more, although the reflectivity can exceed 80%, the absorption loss increases dramatically and the thermal stress of the film layer is large, making it more prone to peeling or diffusion under high welding temperatures, a 30-50nm thickness ensures high reflectivity while controlling the absorption loss at a relatively low level of 12%~40%, effectively reducing the risk of thermal effects. It possesses both metal reflective characteristics and retains a certain welding process window, making it the preferred solution that balances optical performance and engineering feasibility.

[0059] Preferably, the liquid inside the second micropore 104 can be a temperature-sensitive liquid such as temperature-controlled silicone oil, a refractive index-adjustable solution such as a glycerol-water mixture, or an electronically controlled fluid such as liquid crystal.

[0060] Example 2:

[0061] This embodiment provides a method for manufacturing a tunable optical fiber based on optofluidization, applied to a tunable optical fiber based on optofluidization described in Embodiment 1, and includes the following steps:

[0062] S1. A first micro-hole 103 and a second micro-hole 104 symmetrical about the fiber core 101 are formed in the cladding 102 of the optical fiber body 1; the distance between the central axis of the first micro-hole 103 and the second micro-hole 104 and the central axis of the fiber core 101 is 25 micrometers.

[0063] S2. Divide the optical fiber body 1 into three segments, namely: input segment 10, tuning segment 11 and output segment 12.

[0064] S3. Deposit a 30-50nm gold film on the end faces of the input segment 10 and the output segment 12;

[0065] S4. Move the tuning section 11 along the direction from the second micro-hole 104 to the first micro-hole 103, while keeping the input section 10 and the output section 12 stationary, so that the central axis of the second micro-hole 104 on the tuning section 11 moves to a position 9-15 micrometers below the central axis of the first micro-hole 103 on the input section 10 and the output section 12.

[0066] S5. The end faces of the gold-plated films of the input segment 10 and the output segment 12 are respectively welded to the two ends of the tuning segment 11.

[0067] S6. Weld an injection section 13 with a ground bevel to the end of the output section 12 away from the tuning section 11;

[0068] S7. A quartz capillary is vertically fused at the grinding bevel of the injection section 13, so that the quartz capillary is connected to the first micro-hole 103 on the output section 12.

[0069] By adopting the above method, standard fiber optic cleavers and fusion splicers can be used directly for processing, without the need for customized fixtures or complex calibration, which greatly reduces the difficulty and cost of preparation.

Claims

1. A tunable optical fiber based on optofluidics, characterized in that: The optical fiber body (1) includes a fiber core (101) and a cladding (102). The optical fiber body (1) is divided into an input segment (10) and an output segment (12). A tuning segment (11) is provided between the input segment (10) and the output segment (12). A first micro-hole (103) penetrating and parallel to the optical fiber body (1) is formed in the cladding (102) of the input segment (10) and the output segment (12). A second micro-hole (104) penetrating and parallel to the axial direction of the optical fiber body (1) is formed on the tuning segment (11). The two ends of the tuning segment (11) are fused to the input segment (10) and the output segment (12) respectively. The second micro-hole (104) is located between the fiber core (101) of the input segment (10) and the output segment (12) to form a Fabry-Perot cavity. The first micropore (103) is connected to the second micropore (104). The first micropore (103) and the second micropore (104) are the same size and are both cylindrical. The central axes of the first micropore (103) and the second micropore (104) are offset from each other by a first distance. The first distance satisfies the following constraint: D / 3 ≤ ΔL ≤ D / 2, and L / 40 ≤ ΔL ≤ L / 20; In the formula, D is the diameter of the first micropore (103) or the second micropore (104), ΔL is the first distance, and L is the length of the second micropore (104); The optical fiber body (1) further includes an injection segment (13), which is fused to the end of the output segment (12) away from the tuning segment (11). The end of the injection segment (13) near the output segment (12) has a grinding bevel. The first micro-hole (103) is aligned with the air profile formed by the grinding bevel. The angle between the grinding bevel and the axial direction of the optical fiber body (1) satisfies the following constraints: θ = arctan(14ΔL / L); In the formula, ΔL is the first distance, and L is the length of the second micropore (104); A quartz capillary tube perpendicular to the axis of the optical fiber body (1) is connected to the grinding bevel, and the other end of the quartz capillary tube is connected to a needle tube controlled by a microfluidic pump.

2. The tunable optical fiber based on optofluidization according to claim 1, characterized in that: The angle between the grinding bevel and the axial direction of the optical fiber body (1) is 20°-35°.

3. The tunable optical fiber based on optofluidization according to claim 1, characterized in that: The first distance is 9-15 micrometers.

4. The tunable optical fiber based on optofluidization according to claim 1, characterized in that: The length of the second micropore (104) is 300-350 micrometers.

5. A tunable optical fiber based on optofluidization according to claim 1, characterized in that: The input segment (10) and the output segment (12) are each provided with a 30-50nm gold film at the opposite end.

6. A method for manufacturing a tunable optical fiber based on optofluidization, applied to the tunable optical fiber based on optofluidization as described in any one of claims 1-5, characterized in that: Includes the following steps: S1. A first micro-hole (103) and a second micro-hole (104) symmetrical about the fiber core (101) are opened in the cladding (102) of the optical fiber body (1); the distance between the central axis of the first micro-hole (103) and the second micro-hole (104) and the central axis of the fiber core (101) is 25 micrometers; S2. Divide the main body of the optical fiber (1) into three segments, namely: input segment (10), tuning segment (11) and output segment (12). S3. Deposit a 30-50nm gold film on the end faces of the input segment (10) and the output segment (12); S4. Move the tuning segment (11) along the direction from the second micro-hole (104) to the first micro-hole (103), while keeping the input segment (10) and the output segment (12) stationary, so that the central axis of the second micro-hole (104) on the tuning segment (11) moves to a position 9-15 micrometers below the central axis of the first micro-hole (103) on the input segment (10) and the output segment (12); S5. The end faces of the gold-plated films of the input segment (10) and the output segment (12) are respectively welded to the two ends of the tuning segment (11); S6. Weld an injection section (13) with a ground bevel to the end of the output section (12) away from the tuning section (11). S7. A quartz capillary is vertically welded to the grinding slope of the injection section (13) so that the quartz capillary is connected to the first micro-hole (103) on the output section (12).

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