Fiber mode matcher preparation method based on femtosecond laser direct writing system

Abstract

The invention provides an optical fiber mode matcher preparation method based on a femtosecond laser direct writing system, and belongs to the technical field of optical fiber mode matching. The femtosecond laser direct writing system comprises a three-dimensional translation table, an optical fiber clamp, a controller, a femtosecond laser and a microscope objective, and the preparation method comprises the following steps that the three-dimensional translation table drives an optical fiber to be processed to move according to motion data; and the femtosecond laser generates femtosecond pulse laser, controls laser emission according to shutter data, focuses the laser onto the to-be-processed optical fiber through the microscope objective, and cooperates with the movement of the optical fiber to prepare the optical fiber mode matcher. The problem that the welding loss of the existing single-mode optical fiber and dispersion compensation optical fiber is large is solved.

Description

Technical Field

[0001] The present application belongs to the field of optical fiber processing technology, and specifically relates to a method for preparing an optical fiber mode matcher based on a femtosecond laser direct writing system. Background Art

[0002] With the continuous development of optical devices and system technology, as well as people's endless pursuit of bandwidth technology, optical networks are facing constant challenges. Optical fibers will carry more wavelengths, higher optical power, higher transmission rates, and longer distances. As the transmission rate increases, people begin to realize the importance of solving the problem of optical fiber dispersion.

[0003] One of the most commonly used dispersion compensation methods is to use dispersion compensating fiber for compensation, but it has a mode field mismatch with ordinary single-mode fiber, resulting in fusion loss. Therefore, achieving mode field matching between single-mode fiber and dispersion compensating fiber and reducing fiber fusion loss are of great significance to all-fiber structure fiber lasers.

[0004] At present, the fiber taper method and the heating core expansion method are commonly used methods for making mode field adapters. The fiber fusion taper technology can easily destroy the uniform symmetry of the fiber waveguide structure during the taper process, has high precision requirements, and is not suitable for fiber fusion splicing with small cladding differences. Heating core expansion usually uses micro-flame heating, resistance heating, and laser heating to heat the optical fiber, which takes a long time to make and requires complex equipment. How to find a balance between simplifying the preparation process and reducing losses in the mode field matching of single-mode optical fiber and dispersion-compensating optical fiber is a technical problem that urgently needs to be improved in the field of optical fiber mode matching technology. Summary of the invention

[0005] In view of this, the purpose of the embodiments of the present application is to provide a method for preparing an optical fiber mode matcher based on a femtosecond laser direct writing system, which is simple to operate and has a short preparation time, and can realize an optical fiber mode matcher that can withstand high power.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing an optical fiber mode matcher based on a femtosecond laser direct writing system, wherein the femtosecond laser direct writing system comprises: a three-dimensional translation stage, an optical fiber clamp, a controller, a femtosecond laser, and a microscope objective lens, wherein the optical fiber to be processed is placed on the optical fiber clamp, the three-dimensional translation stage and the femtosecond laser are both connected to the controller, and the femtosecond laser is focused on the optical fiber to be processed through the microscope objective lens, wherein the preparation method comprises the following steps:

[0007] Generate motion data of the three-dimensional translation stage and shutter control data of the femtosecond laser through the controller, send the motion data to the three-dimensional translation stage, and send the shutter control data to the femtosecond laser;

[0008] The three-dimensional translation stage moves according to the motion data to drive the optical fiber to be processed fixed thereon by the optical fiber fixture to move.

[0009] The femtosecond laser generates femtosecond pulsed laser, controls the laser output according to the shutter control data, and focuses the output laser onto the optical fiber to be processed through the microscope objective. At the same time, the three-dimensional translation stage drives the optical fiber to be processed to move according to the controller motion data to generate an optical fiber mode matcher.

[0010] Furthermore, the femtosecond laser direct writing system further includes: a glass slide and a coverslip, which are located on the optical fiber fixture; before clamping and rotating the optical fiber to be processed by the optical fiber fixture, the method further includes: placing the optical fiber to be processed on the glass slide, adding a refractive index matching liquid in the area to be processed, and covering the coverslip after the addition of the refractive index matching liquid is completed.

[0011] Furthermore, the output wavelength of the femtosecond laser generating the femtosecond pulsed laser is 1030 nm, and the repetition frequency is 300 kHz.

[0012] Furthermore, the optical fiber to be processed includes a first single-mode optical fiber, a dispersion compensation optical fiber, and a second single-mode optical fiber; before clamping and rotating the optical fiber to be processed by the optical fiber fixture, the method further includes: removing the coating layers at both ends of one end of the dispersion compensation optical fiber and the first single-mode optical fiber, cutting the optical fiber flat after wiping with alcohol, placing it in a fusion splicer for fusion splicing, and performing discharging and fusion splicing in a core alignment manner; fusing the other end of the dispersion compensation optical fiber with the second single-mode optical fiber.

[0013] Furthermore, the mode field diameters of the first single-mode optical fiber, the dispersion compensation optical fiber, and the second single-mode optical fiber are 10 μm, 4 μm, and 10 μm respectively, and the cladding diameters are all 125 μm.

[0014] Compared with the prior art, the beneficial effects of the present application are:

[0015] 1. The method for manufacturing the optical fiber mode matcher provided by the present invention is simple to operate, has a short preparation time, does not require fiber tapering, greatly reduces the complexity of the entire process flow, and the preparation method is simple and efficient, and can be mass-produced in an engineering manner.

[0016] 2. The method for manufacturing the optical fiber mode matcher provided by the present invention uses femtosecond processing technology, and the product can withstand high power and can effectively improve the coupling efficiency and stability.

[0017] To make the above objects, features, and advantages of the present application more obvious and understandable, specific embodiments are hereinafter given, and detailed descriptions are provided in conjunction with the accompanying drawings as follows. Description of the Drawings

[0018] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0019] Figure 1 Schematic diagram of an apparatus for preparing an optical fiber mode matcher of a femtosecond laser direct writing system provided in an embodiment of the present application.

[0020] Figure 2 Schematic diagram of optical fiber fusion splicing provided in an embodiment of the present application.

[0021] Figure 3 Schematic diagram of processing provided in an embodiment of the present application.

[0022] Figure 4 Experimental result diagram provided in an embodiment of the present application. Detailed Embodiments

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Usually, the components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application provided in the drawings below is not intended to limit the scope of the present application claimed, but only represents the selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0024] It should be noted that like reference numerals and letters refer to like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. The terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising the element. The terms "first", "second", etc. are used only for descriptive distinction and should not be construed as indicating or implying relative importance.

[0025] Term definition: DCF: Dispersion Compensating Fiber, SMF: Single Mode Fiber.

[0026] In view of this, an embodiment of the present application provides a schematic diagram of an apparatus for preparing an optical fiber mode matcher of a femtosecond laser direct writing system, as Figure 1 described, comprising: a femtosecond laser (1), a 50x microscope objective (2), a three-dimensional translation stage (3), an optical fiber fixture (4), a refractive index matching liquid (5) and a controller (6). The femtosecond laser (1) and the three-dimensional translation stage (3) are connected to the controller (6), and the controller (6) controls the scanning processes of the femtosecond laser (1) and the three-dimensional translation stage (3) through connections with each device.

[0027] The light output by the femtosecond laser (1) has a wavelength of 1030 nm, a repetition frequency of 300 kHz, and a pulse width of 400 fs. The femtosecond pulsed laser passes through a beam splitter. A part of the laser passes through the 50x (NA = 0.42) focusing objective (2) and is focused on the optical fiber to be processed, and the other part is reflected by a mirror and passes through a CCD camera. The optical fiber to be processed is placed on a glass slide and fixed by the optical fiber fixture (4). A refractive index matching liquid (5) is added to the area to be processed to reduce the spherical aberration problem caused by the cylindrical surface or refractive index mismatch of the optical fiber. After the refractive index matching liquid is added, covering with a 0.5-mm thick cover glass is beneficial to increasing the length of the refractive index modification area. The processing process and state of the optical fiber can be observed and fed back in real time on a computer through the CCD camera. The accuracy of the three-dimensional translation stage is 1 μm, and the controller (6) makes the three-dimensional translation stage (3) perform a circular motion from left to right at a speed of 0.05 mm / s. When the laser is focused on the optical fiber to be processed, pulse energy is continuously injected into the focal area and then converted into heat energy through phonon-electron coupling. At this time, Si ions migrate from the laser focus to the peripheral area with a lower temperature.

[0028] AsFigure 2 As shown in the figure, the schematic diagram of optical fiber fusion splicing provided by the embodiment of the present application includes the following steps: Remove the coating layers from one end of the dispersion compensation optical fiber and both ends of the first single-mode optical fiber, cut the optical fibers flat after wiping with alcohol, place them in a fusion splicer for fusion splicing, and perform discharging and fusion splicing in a core alignment manner; fuse the other end of the dispersion compensation optical fiber with the second single-mode optical fiber.

[0029] The mode field diameters of one end of the dispersion compensation optical fiber and the first single-mode optical fiber are 8μm and 4μm respectively. For the connection loss caused by different optical fiber mode field diameters, the fusion splicing loss can be calculated by the formula α = 20lg[(ω1 / 2ω2)+(ω2 / 2ω1)], where ω1 and ω2 are the mode field diameters of the dispersion compensation optical fiber and the single-mode optical fiber respectively. Theoretically, the fusion splicing loss is 3dB, and the fusion splicing loss of 2 ports is 6dB.

[0030] As Figure 3 shown in the figure, the processing schematic diagram provided by the embodiment of the present application is as follows: The femtosecond laser output by the femtosecond laser (1) is focused onto the interface between the first single-mode optical fiber and the dispersion compensation optical fiber through a 50-fold focusing objective lens (2). Corresponding motion parameters are input into the controller (6). In order to match and expand the mode field diameter of the DCF, the shape of femtosecond direct writing is a tight annular structure with a radius of 4μm. By controlling the pulse energy and processing length, the mode field diameter of the DCF can be further increased to make the mode field diameters of the SMF and DCF match.

[0031] As Figure 4 shown in the figure, the experimental result diagram provided by the embodiment of the present application is as follows: When the femtosecond laser is performing writing, it is necessary to observe the output spectrum of the spectrometer to monitor the processing effect of the optical fiber mode matcher in real time. Use a broadband light source and a spectral analyzer to measure the fusion splicing loss of SMF-DCF-SMF in the wavelength range of 1530 - 1600nm. In the processing experiment of the embodiment of the present application, 1.6m of dispersion compensation optical fiber is fused with 2m of single-mode optical fiber, and the fusion splicing loss before processing is 6.2dB. By processing an annulus at both ends of the fusion splicing point through the femtosecond laser direct writing system, the mode field diameters of the dispersion compensation optical fiber and the single-mode optical fiber are made to match, and the total insertion loss is less than 1.8dB. Figure 3 In summary, the method for preparing an optical fiber mode matcher based on a femtosecond laser direct writing system provided by the present application simplifies the preparation process and improves the efficiency, meeting the application requirements.

[0032] In this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0033]

[0034] ​The above are only the embodiments of the present application and are not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A preparation method of an optical fiber mode matcher based on a femtosecond laser direct writing system, characterized in that The method includes: a three-dimensional translation stage, an optical fiber fixture, a controller, a femtosecond laser, and a microscope objective. The optical fiber to be processed is placed on the optical fiber fixture. The three-dimensional translation stage and the femtosecond laser are both connected to the controller. The femtosecond laser is focused on the optical fiber to be processed through the microscope objective. Among them, the preparation method includes the following steps: Generate the motion data of the three-dimensional translation stage and the shutter control data of the femtosecond laser through the controller, send the motion data to the three-dimensional translation stage, and send the shutter control data to the femtosecond laser; The three-dimensional translation stage moves according to the motion data to drive the optical fiber to be processed fixed on it through the optical fiber fixture; The femtosecond laser generates femtosecond pulsed laser, controls the laser output according to the shutter control data, and focuses the output laser on the optical fiber to be processed through the microscope objective. At the same time, the three-dimensional translation stage drives the optical fiber to be processed to move according to the controller motion data to generate an optical fiber mode matcher.

2. The method according to claim 1, wherein The femtosecond laser direct writing system includes: a glass slide and a coverslip. The glass slide and the coverslip are located on the optical fiber fixture; when clamping and rotating the optical fiber to be processed through the optical fiber fixture, before the optical fiber fixture is clamped and rotated, the method further includes: placing the optical fiber to be processed on the glass slide, adding a refractive index matching liquid in the processing area, and covering the coverslip after the refractive index matching liquid is added.

3. The method according to claim 1, characterized in that, Among them, The output wavelength of the femtosecond laser that generates femtosecond pulsed laser is 1030 nm, and the repetition frequency is 300 kHz.

4. The method according to claim 1, wherein The optical fiber to be processed includes a first single-mode fiber, a dispersion compensation fiber, and a second single-mode fiber; when clamping and rotating the optical fiber to be processed through the optical fiber fixture, before the optical fiber fixture is clamped and rotated, the method further includes: removing the coating layers at both ends of one end of the dispersion compensation fiber and the first single-mode fiber, cutting the optical fiber flat after wiping with alcohol, placing it in a fusion splicer for fusion splicing, and discharging and fusing in a core alignment manner; fusing the other end of the dispersion compensation fiber with the second single-mode fiber.

5. The method according to claim 4, wherein Among them, The mode field diameters of the first single-mode fiber, the dispersion compensation fiber, and the second single-mode fiber are 10 μm, 4 μm, and 10 μm respectively, and the cladding diameters are all 125 μm.

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