Methods for processing reverse cladding light in sleeving fiber combiners and fiber combiners

Abstract

This invention discloses a method for processing reverse cladding light in a sleeve-type fiber optic combiner and the fiber optic combiner itself. Before the fiber bundle is inserted into the fluorinated quartz tube, the edge of the fiber bundle insertion port of the fluorinated quartz tube is machined into a tooth shape. This process disrupts the flatness of the quartz tube opening, thereby disrupting the transmission path of the reverse cladding light. This allows the reverse cladding light to diverge out at the fiber bundle insertion port and be converted into heat and carried away upon contact with the heat dissipation enclosure. This prevents the reverse cladding light from propagating along the fluorinated quartz tube to the coating layer at the end of the fiber bundle, thus preventing a rapid temperature rise at the fiber bundle end and reducing the risk of device burnout. This invention features a simple process, convenient operation, and low operator requirements, which is beneficial for mass production. Furthermore, the fluorinated quartz tube is processed during the pre-production stage, without affecting the cleanliness of the product, ensuring product quality.

Description

Technical Field

[0001] This invention relates to a method for processing reverse cladding light in a sleeve-type fiber optic combiner, and also to a fiber optic combiner using this processing method. Background Technology

[0002] Fiber lasers have attracted increasing attention due to their excellent performance and broad application prospects. Compared with traditional solid-state lasers, they have advantages such as high conversion efficiency, good beam quality, and convenient thermal management, and have been widely used in industrial manufacturing, laser medicine, aerospace, and national defense. As the output power requirements of fiber lasers continue to increase, high power has become an important direction for fiber laser development. A key component in high-power fiber lasers is the pump signal fiber combiner, whose power handling capacity directly determines the laser's output power level. Based on the coupling method of the pump light, combiners are divided into side-pumped combiners and end-pumped combiners. End-pumping is a common coupling method. The advantage of end-pumping is that its structure is easy to implement and it is relatively easy to achieve high coupling efficiency. Currently, most high-power fiber lasers adopt end-pumping.

[0003] There are two main methods for fabricating end-pumped fiber combiners: the knotting method and the sleeve method. High-power end-pumped fiber combiners fabricated using the sleeve method are increasingly used because they can maintain both signal beam quality and withstand high power. Compared to the knotting method, the sleeve method adds a low-refractive-index fluorine-doped silica tube to the fiber bundle. Unabsorbed pump light and core-loss signal light (referred to as reverse cladding light) from the laser path enter the fluorine-doped silica tube and continue propagating along it to the end coating of the fiber bundle. This causes a rapid increase in temperature at the end, posing a risk of device burn-out.

[0004] Currently, there is no specific method for handling reverse cladding light. Moreover, if the main body of the combiner has already been manufactured, adding special processing for reverse cladding light will cause the following problems: (1) It may easily affect the cleanliness of the product and even cause the device to be scrapped; (2) It is inconvenient to operate and requires high skill from the operators; (3) The reverse cladding light handling capacity of a typical combiner is about 300W, which is relatively low. Summary of the Invention

[0005] The first objective of this invention is to provide a simple process for processing the reverse cladding light of a sleeve-type fiber optic combiner, which does not affect product quality and reduces the risk of product burnout.

[0006] The first objective of this invention is achieved by the following technical measures: a method for processing reverse cladding light in a sleeve-type fiber combiner, characterized in that, before the fiber bundle is inserted into the fluorine-doped quartz tube, the edge of the fiber bundle insertion port of the fluorine-doped quartz tube is processed into a tooth shape.

[0007] This invention pre-treats the fluorine-doped quartz tube by machining the edge of the fiber insertion port into a serrated shape before the fiber bundle is inserted. This disrupts the flatness of the tube opening and thus disrupts the transmission path of the reverse cladding light. This allows the reverse cladding light to diverge out from the fiber insertion port and be converted into heat and carried away upon contact with the heat dissipation enclosure. This prevents the reverse cladding light from propagating along the fluorine-doped quartz tube to the coating layer at the fiber bundle end, thereby preventing a rapid temperature rise at the fiber bundle end and reducing the risk of device burnout. Furthermore, this invention is simple to process, easy to operate, and requires less skilled operators, making it suitable for mass production. Since the fluorine-doped quartz tube is treated during the pre-production stage, it does not affect the cleanliness of the product, ensuring product quality.

[0008] The present invention processes the sharp edges of the toothed edge into an arc shape, which can prevent the reverse cladding light from accumulating at the sharp part and forming a heat concentration point.

[0009] A key technical indicator in pump signal fiber optic combiners is the ability to withstand reverse cladding light. The higher the reverse cladding light power it can withstand, the better the performance. In this invention, after the fiber bundle is inserted into the fluorine-doped quartz tube, the distance L between the fiber bundle insertion port of the fluorine-doped quartz tube and the stripping step of the fiber bundle coating is set to more than 20mm. Maintaining a sufficient distance ensures that the diverging light does not affect the coating of the fiber bundle, thereby further improving the reverse cladding light handling capability of the product, which can reach more than 500W.

[0010] Preferably, the present invention uses tweezers or a gem cutting pen to insert the fiber bundle of the fluorine-doped quartz tube into the edge of the port and process it into a tooth shape.

[0011] Preferably, the present invention performs a discharge treatment on the sharp edges of the toothed edge to make it arc-shaped.

[0012] A second objective of this invention is to provide an optical fiber combiner that uses the above-described method for processing reverse cladding light using a sleeve-type optical fiber combiner.

[0013] The second objective of this invention is achieved through the following technical measures: an optical fiber combiner using the above-mentioned sleeve-type optical fiber combiner reverse cladding light processing method, comprising a fluorine-doped quartz tube with a tapered structure and an optical fiber bundle, wherein the optical fiber bundle is inserted into the fluorine-doped quartz tube and then encapsulated after being fused and tapered to form an optical fiber combiner, characterized in that the edge of the fiber bundle insertion port of the fluorine-doped quartz tube is processed into a tooth shape.

[0014] Compared with the prior art, the present invention has the following significant effects:

[0015] (1) The present invention processes the edge of the fiber bundle insertion port of the quartz tube into a tooth shape, which destroys the flatness of the quartz tube opening and thus destroys the transmission path of the reverse cladding light. This allows the reverse cladding light to diverge out of the fiber bundle insertion port and be converted into heat and carried away after contacting the heat dissipation package. This prevents the reverse cladding light from being transmitted along the fluorine-doped quartz tube to the position of the fiber bundle tail coating, thereby preventing the temperature of the fiber bundle tail from rising sharply and reducing the risk of the device being burned out.

[0016] (2) The present invention processes the fluorine-doped quartz tube in the preparation process, which does not affect the cleanliness of the product and ensures product quality.

[0017] (3) The present invention processes the sharp edge of the toothed edge into an arc shape, which can prevent the reverse cladding light from accumulating at the sharp part and forming a heat concentration point.

[0018] (4) The present invention maintains a sufficient distance between the fiber bundle insertion port of the fluorine-doped quartz tube and the stripping step of the coating layer of the optical fiber bundle, so that the diverging light does not affect the coating layer of the optical fiber bundle, thereby further improving the reverse cladding light carrying capacity of the product to more than 500W.

[0019] (5) The process of this invention is simple, easy to operate, and requires less skill from operators, which is conducive to mass production. Attached Figure Description

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 This is a flowchart of the manufacturing process of an optical fiber combiner using the processing method of the present invention.

[0022] Figure 2 This is a schematic diagram of a fluorine-doped quartz tube structure using the processing method of this invention;

[0023] Figure 3 This is a schematic diagram of an optical fiber combiner structure using the processing method of the present invention. Detailed Implementation

[0024] like Figures 1-3The diagram illustrates a method for processing reverse cladding light in a sleeve-type fiber optic combiner according to the present invention. In the pre-fabrication process, the fluorinated quartz tube is treated. Specifically, before the fiber bundle 1 is inserted into the fluorinated quartz tube 2, tweezers or a gemstone cutting pen are used to process the edge of the fiber bundle insertion port 3 (the quartz tube opening near the long fiber end of the fiber bundle) of the fluorinated quartz tube 2 into a toothed shape, creating an uneven opening. This allows the reverse cladding light A to diverge out from the fiber bundle insertion port, reducing the risk of device burn-out. Furthermore, the fiber bundle insertion port 3 of the fluorinated quartz tube 2 is placed on a fiber optic fusion splicer for discharge treatment. This discharge process shapes the sharp edges of the toothed edge into an arc shape, preventing the reverse cladding light from concentrating and forming a heat-generating concentration point.

[0025] After the fiber bundle 1 is inserted into the fluorine-doped quartz tube 2, the distance L between the fiber bundle insertion port 3 of the fluorine-doped quartz tube 2 and the stripping step of the coating layer 4 of the fiber bundle 1 is set to more than 20mm. Maintaining a sufficient distance can prevent the diffused light from affecting the coating layer of the fiber bundle, thereby further improving the reverse cladding light carrying capacity of the product, which can reach more than 500W.

[0026] An optical fiber combiner using the above-mentioned sleeve-type optical fiber combiner reverse cladding light processing method, the optical fiber combiner includes a fluorine-doped quartz tube 2 with a tapered structure and an optical fiber bundle 1. The optical fiber bundle 1 is inserted into the fluorine-doped quartz tube 2 and encapsulated after being fused and tapered to form the optical fiber combiner. The edge of the fiber bundle insertion port 3 of the fluorine-doped quartz tube 2 is processed into a tooth shape.

[0027] This embodiment employs the processing method of the present invention. The input signal fiber of the combiner is a double-clad 50 / 250um (0.11 / 0.46NA) fiber, the pump fiber is a 220 / 242um (0.22NA) fiber, and the output signal fiber is a double-clad 20 / 400um (0.65 / 0.46NA) fiber. See [link to documentation]. Figure 1 The complete manufacturing process for fiber optic combiners is as follows (compared to existing processes, an additional step of treating the fluorine-doped quartz tube tip is added):

[0028] 1. Select a 100mm long fluorine-doped quartz tube with inner and outer diameters of 1250 / 1650µm. Clean its surface with alcohol and pre-tighten it into a tapered shape. Figure 2 The cone structure shown has an inner and outer diameter of 757.6 / 1000um for the waist region 5 and a length of 30mm. The two tapered regions 6, which gradually change in length, are 5mm long.

[0029] 2. Select one end as the fiber bundle insertion port for the 6 pump fibers and 1 signal fiber of the fiber combiner. Use tweezers or a gem cutter to break the fiber bundle insertion port into a jagged, uneven tube opening, such as... Figure 2 As shown.

[0030] 3. Place the serrated end of the fluorine-doped quartz tube on the clamp of the fiber optic fusion splicer and fix it. Select an appropriate discharge power to discharge, so that the sharp part of the tube end becomes arc-shaped.

[0031] 4. Remove a 120mm long section of coating from one end of the 6 pump fibers and 1 signal fiber. For the cladding portion of the input signal fiber, use a certain concentration of hydrofluoric acid to etch the cladding diameter from 250um to 240um. Then, clean the bare fiber portion with the coating removed using alcohol. Insert the fiber through the jagged, uneven tube opening. The input signal fiber should be in the middle of the 6 pump fibers, forming a hexagonal shape. The stripping step of the coating should be at least 20mm away from the tube opening.

[0032] 5. Using appropriate parameters, fused and tapered the fiber bundle after it has been inserted into the tube, with a minimum diameter of 380-400µm. Cut it at the thinnest point with a cleaver and fusion splice it to the output fiber at a 20 / 400µm diameter. Figure 3 As shown, the fiber optic combiner is then encapsulated to complete its fabrication.

[0033] This fiber optic combiner underwent reverse cladding light testing: The fiber optic combiner was connected to the test optical path. The six pump fibers and one signal fiber at the input end were cut flat using a fiber optic cleaver and placed at the power meter port. 0.46NA of reverse cladding light was injected from the output fiber (20 / 400), and temperature was measured using a thermal imager. When the reverse cladding light increased to 500W, the temperature at the fiber bundle tip of the fiber optic combiner did not exceed 50°C, indicating a sufficient safety range from the temperature tolerance of the fiber coating.

Claims

1. A method for processing reverse cladding light in a sleeve-type fiber combiner, characterized in that: Before the optical fiber bundle is inserted into the fluorinated quartz tube, the edge of the fiber bundle insertion port of the fluorinated quartz tube is processed into a tooth shape; after the optical fiber bundle is inserted into the fluorinated quartz tube, the distance L between the fiber bundle insertion port of the fluorinated quartz tube and the stripping step of the coating layer of the optical fiber bundle is set to more than 20 mm.

2. The method for processing reverse cladding light in a sleeve-type fiber combiner according to claim 1, characterized in that: The sharp edges of the toothed edge are machined into a curved shape.

3. The method for processing reverse cladding light in a sleeve-type fiber combiner according to claim 2, characterized in that: Use tweezers or a gem-cutting pen to thread the fiber bundle of the fluorine-doped quartz tube through the edge of the port and process it into a tooth shape.

4. The method for processing reverse cladding light in a sleeve-type fiber combiner according to claim 3, characterized in that: The sharp edges of the toothed edge are subjected to electrical discharge treatment to make them arc-shaped.

5. An optical fiber combiner using the reverse cladding light processing method of the sleeve-type optical fiber combiner according to claim 1, comprising a fluorine-doped quartz tube with a tapered structure and an optical fiber bundle, wherein the optical fiber bundle is inserted into the fluorine-doped quartz tube and then encapsulated after fused tapering to form the optical fiber combiner, characterized in that: The fiber bundles of the fluorine-doped quartz tube are toothed at the edge of the insertion port.

6. The fiber optic combiner according to claim 5, characterized in that: The top of the protrusion of the toothed edge is arc-shaped.

7. The fiber optic combiner according to claim 6, characterized in that: The distance between the fiber bundle insertion port of the fluorine-doped quartz tube and the stripping step of the coating layer of the optical fiber bundle is more than 20 mm.

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