Bismuth-doped optical fiber and preparation method and application thereof

Abstract

The invention provides a bismuth-doped optical fiber and a preparation method and application thereof, the bismuth-doped optical fiber realizes C + L full-band positive gain through cooperation of Bi, Ge, La and Y and component proportion optimization: Bi is a core active component to form a BACS to generate near-infrared gain; la and Y improve the BACS concentration, inhibit non-radiation loss and enhance the gain efficiency; and the Ge adjusts the refractive index of the fiber core to guarantee stable optical transmission. According to the optimization, the problem of negative gain of the traditional BDF in the C + L wave band (especially 1524nm) is solved, the noise is reduced, and the practical value of broadband communication is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber, and particularly relates to a bismuth-doped optical fiber and a preparation method and application thereof. BACKGROUND

[0002] Since the breakthrough of low-loss silica-based optical fiber in the 1970s and the Erbium-Doped Fiber Amplifier (EDFA) in the 1980s, the global communication network has achieved a leap-forward development. The current emerging technologies such as artificial intelligence and Internet of Things accelerate the evolution, and promote the global data annual compound growth rate to break through 40%, and the existing communication system has been difficult to meet the rapidly growing data demand. Limited by the Shannon limit and nonlinear effects of fiber communication capacity, the path of improving the capacity by increasing the single-channel transmission rate and reducing the channel spacing has reached the limit. The current mainstream communication system relies on EDFA technology, mainly applying C-band (1525~1565nm) and L-band (1565~1620nm); although the L-band EDFA expands the available bandwidth from 40nm to 95nm, compared with the 1200~1700nm low-loss window (minimum loss 0.16dB / km) covered by the modern ultra-low-loss fiber (ULL—G.625), the existing system only uses about 19% of the available spectrum resources, and it is estimated that the bandwidth will soon be exhausted again. Expanding the bandwidth of fiber communication and increasing the number of channels is an effective solution to continue to improve the communication capacity. In addition to C-band and L-band, O-band (1260~1360nm), E-band (1360~1460nm), S-band (1460~1530nm) and U-band (1625~1675nm) all belong to the low-loss transmission window, and fully utilizing these bandwidth resources is an important way to solve the future fiber "capacity crisis" and is also an inevitable development trend in the field of optical communication. The key to achieving this goal lies in the development of active optical fibers with high gain performance in O, E, S and U bands.

[0003] Bismuth-doped fiber (BDF), with its unique near-infrared ultra-wideband emission characteristics, has become an important candidate active medium for overcoming the bandwidth limitations of existing optical fibers and improving data transmission capabilities. Its gain band can cover key bands such as O, E, S, and U. To date, the gain performance of BDF has been significantly improved, achieving many outstanding results in amplifiers, lasers, and transmission systems, fully demonstrating its enormous application potential. However, the current concentration of bismuth-related active centers (BACS) in BDF is relatively low, resulting in low gain efficiency. Especially in broadband amplification applications in the C+L band, a negative gain phenomenon exists at 1524 nm, and the fiber noise is higher than that of EDFA. These problems severely limit the practical application of BDF in the C+L band.

[0004] Therefore, there is an urgent need for a bismuth-doped optical fiber, its preparation method, and its application to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a bismuth-doped optical fiber, its preparation method, and its application, in order to solve the technical problems of low gain efficiency and negative gain and high noise at 1524nm in the C+L band in existing bismuth-doped optical fibers due to the low concentration of bismuth-related active centers.

[0006] To address the aforementioned technical problems, this invention first provides a method for preparing bismuth-doped optical fibers, comprising the following steps: S10, a loose layer of silica is deposited on the inner wall of a quartz tube to obtain a reaction tube; S20, immerse the reaction tube in a solution containing Bi 3+ La 3+ and Y 3+ The first doped quartz tube was obtained by drying the solution containing Bi in an inert drying atmosphere. 3+ The concentration for preparation is 5~100g / L, La 3+ The concentration for preparation is 0.1~15g / L, Y 3+ The concentration for preparation is 0.1~15g / L; S30, the first doped quartz tube is baked in a dry gas atmosphere to obtain the second doped quartz tube; S40, deposit a germanium dioxide doped layer on the inner wall of the second doped quartz tube to obtain the third doped quartz tube; S50, the third doped quartz tube is baked a second time in an oxygen atmosphere to obtain the fourth doped quartz tube; S60 involves scalding the fourth doped quartz tube into a quartz preform, inserting it into a quartz sleeve, and drawing it into a bismuth-doped optical fiber in a drawing tower.

[0007] Preferably, step S10 specifically includes: introducing silicon tetrachloride and oxygen into a quartz tube at 1530~1710°C to obtain a reaction tube.

[0008] Preferably, in step S20, the soaking time is 2~10h, the soaking temperature is 20~60℃, and the reaction tube is rotated at a speed of 10r / min~50r / min during the soaking process.

[0009] Preferably, in step S30, the drying atmosphere is nitrogen or chlorine, and the baking temperature for the first baking treatment is 1100~1300℃.

[0010] Preferably, step S40 specifically includes: introducing germanium tetrachloride and oxygen into the second doped quartz tube at 1400~1500℃ to obtain the third doped quartz tube.

[0011] Preferably, the germanium dioxide doped layer has a doping mass percentage of 20% to 60%.

[0012] Preferably, in step S50, the baking temperature for the second baking treatment is 1950℃~2100℃.

[0013] Preferably, in step S60, the temperature at which the fourth doped quartz tube is sintered is 1900~2200℃, and the pressure inside the fourth doped quartz tube during sintering is 75~200Pa.

[0014] Accordingly, the present invention also provides a bismuth-doped optical fiber, which is prepared by any of the above-described methods for preparing bismuth-doped optical fibers.

[0015] Accordingly, the present invention also provides an amplification application of the bismuth-doped optical fiber as described in any of the above claims in the C+L band.

[0016] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides a bismuth-doped optical fiber, its preparation method, and its application. The method includes: first, depositing a porous silica layer on the inner wall of a quartz tube to obtain a reaction tube; second, immersing the reaction tube in a solution containing Bi... 3+ La 3+ and Y 3+The first doped quartz tube is obtained by drying it in an inert dry atmosphere in a doping solution. Then, the first doped quartz tube is baked for the first time in a dry gas atmosphere to obtain a second doped quartz tube. Next, a germanium dioxide doped layer is deposited on the inner wall of the second doped quartz tube to obtain a third doped quartz tube. Next, the third doped quartz tube is baked for the second time in an oxygen atmosphere to obtain a fourth doped quartz tube. Finally, the fourth doped quartz tube is sintered into a quartz preform and inserted into a quartz sleeve, and then drawn into a bismuth-doped optical fiber in a drawing tower. The bismuth-doped optical fiber prepared by this invention achieves positive gain output across the entire C+L band through the synergistic effect of Bi, Ge, La, and Y and optimization of component ratios. Bi, as the core active component, forms the basis for bismuth-associated active centers (BACS) and generates near-infrared gain. La and Y, as co-doped elements, significantly increase the concentration of BACS and suppress its non-radiative transition loss, effectively enhancing the fiber's gain efficiency. Ge is used to adjust the core refractive index, ensuring stable transmission of optical signals within the core and providing good waveguide conditions for gain output. Furthermore, by rationally adjusting the component ratios of Bi, Ge, La, and Y, the activity of BACS, refractive index matching, and gain bandwidth coverage can be further synergistically optimized. This solves the negative gain problem of traditional bismuth-doped optical fibers in the C+L band (especially at 1524 nm) and reduces fiber noise, ultimately achieving stable positive gain across the entire band and enhancing the practical value of bismuth-doped optical fibers in broadband communication systems. Attached Figure Description

[0017] Figure 1 A flowchart illustrating the method for preparing bismuth-doped optical fiber according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the optical fiber testing device provided in Embodiment 1. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] To address the shortcomings of existing technologies, the bismuth-doped optical fiber prepared in this invention introduces original elements such as lanthanum (La), yttrium (Y), and germanium (Ge), while optimizing the composition ratio of Bi, Ge, La, and Y, achieving positive gain output across the entire C+L band. This solves the problems of low gain and high noise in bismuth-doped optical fibers at 1524nm.

[0020] As used in this article, "MCVD" refers to "modified chemical vapor deposition". The process involves using oxygen as a carrier gas to carry the reactants into the base tube from the inlet end of the base tube. The base tube is heated by a burner on the outside, which indirectly heats the reactants inside the base tube to produce a glassy substance, which is then deposited on the inner wall of the base tube.

[0021] As used in this article, "quartz tube" refers to Heraeus' F300 high-purity quartz reaction tube.

[0022] Please see Figure 1 , Figure 1 This is a flowchart illustrating the fabrication method of bismuth-doped optical fiber provided in an embodiment of the present invention; the bismuth-doped optical fiber includes the following steps: S10: A loose layer of silica is deposited on the inner wall of a quartz tube to obtain a reaction tube.

[0023] Specifically, step S10 also includes: Using the MCVD process, silicon tetrachloride and oxygen are introduced into a pure quartz glass tube (high-purity quartz tube, Heraeus F300 model), and a loose, porous silica layer is deposited at a temperature of 1530~1710℃ to obtain the reaction tube. The main chemical reaction equations involved in step S10 are as follows: .

[0024] Furthermore, step S10 utilizes the MCVD process to ensure the uniformity and high purity of the deposited layer, relies on high-purity quartz tubes to reduce interference from substrate impurities, and controls the porous structure of the layer through specific temperature control, thus preparing the substrate for the subsequent Bi deposition in step S20. 3+ La 3+ and Y 3+ The effective adsorption creates conditions, and the chemical reaction can generate high-purity silicon dioxide, laying a solid foundation for the subsequent preparation of high-performance bismuth-doped optical fibers.

[0025] S20, immerse the reaction tube in a solution containing Bi 3+ La 3+ and Y 3+ The first doped quartz tube was obtained by drying the solution containing Bi in an inert drying atmosphere. 3+ The concentration for preparation is 5~100g / L, La 3+ The concentration for preparation is 0.1~15g / L, Y 3+ The concentration for preparation is 0.1~15g / L.

[0026] Specifically, step S20 also includes: First, immerse the reaction tube in a solution containing Bi. 3+ La 3+ and Y 3+In the doped solution, Bi 3+ La 3+ and Y 3+ The doping solution is incorporated into the reaction tube through the pores of the porous silica layer; the solvent of the doping solution is deionized water or anhydrous ethanol, and the solute contains Er. 3+ Yb 3+ La 3+ and Y 3+ The chloride ion solution is used; the soaking time of the reaction tube in the doped solution is 2~10h, and the soaking temperature is 20~60℃; during the soaking process, the reaction tube is kept rotating at a speed of 10r / min~50r / min. Keeping the reaction tube rotating at a uniform speed and the soaking temperature of 20~60℃ can make the solute adsorbed evenly on the loose layer as much as possible (the porous structure of the silica loose layer will adsorb ions in the solution, and heating and rotation will promote the absorption of ions by the porous structure).

[0027] Next, the doped solution is taken out from the reaction tube and dried with nitrogen gas to obtain a first doped quartz tube containing ErCl3, YbCl3, LaCl3 and YCl3.

[0028] In this embodiment, the doping solution contains: Bi 3+ The concentration for preparation is 5~100g / L, La 3+ The concentration for preparation is 0.1~15g / L, Y 3+ The concentration for preparation is 0.1~15g / L; among which, Bi 3+ The concentration range ensures the formation of sufficient bismuth-associated active centers (BACS), providing a basis for gain performance; La 3+ and Y 3+ The concentration can effectively promote the formation and stability of BACS, suppress non-radiative losses to enhance gain efficiency, and avoid ion aggregation or performance degradation caused by excessive concentration. The synergistic matching of the three concentrations lays a key foundation for the doping ratio in the subsequent preparation of high-performance bismuth-doped optical fibers.

[0029] Furthermore, Bi 3+ At concentrations too low (<5 g / L), it is difficult to form sufficient bismuth-associated active centers (BACS), resulting in insufficient fiber gain and inability to meet the amplification requirements of the C+L band; Bi 3+ Excessive concentration (>100g / L) can easily trigger Bi 3+ Aggregation reduces BACS activity and increases non-radiative transition loss, leading to increased fiber noise and consequently degrading gain performance.

[0030] Furthermore, La 3+ and Y 3+When the concentration of La is too low (<0.1 g / L), it cannot effectively promote the formation and stability of BACS, making it difficult to suppress non-radiative losses and resulting in limited improvement in gain efficiency; 3+ and Y 3+ Excessively high concentrations (>15 g / L) may enhance interionic interactions, induce lattice distortion, disrupt fiber optic uniformity, increase light scattering loss, and may also interact with Bi. 3+ Competing for doping sites actually reduces the effective concentration of BACS.

[0031] S30, the first doped quartz tube is baked in a dry gas atmosphere to obtain the second doped quartz tube.

[0032] Specifically, step S30 also includes: The first doped quartz tube is heated to 1100~1300℃ (preferably 1200℃) in a chlorine or nitrogen atmosphere to remove moisture and hydroxyl groups from the first doped quartz tube.

[0033] S40, deposit a germanium dioxide doped layer on the inner wall of the second doped quartz tube to obtain the third doped quartz tube.

[0034] Specifically, step S40 also includes: Germanium tetrachloride and oxygen are introduced into the second-doped quartz tube at 1400~1500℃ to obtain the third-doped quartz tube; the doping mass percentage of the germanium dioxide doped layer is controlled to be 20%~60% by adjusting the reaction temperature and gas flow rate; the main chemical reaction equations involved in step S40 are as follows: .

[0035] Furthermore, the temperature conditions of 1400~1500℃ ensure that germanium tetrachloride reacts fully with oxygen, efficiently forming a uniform germanium dioxide doped layer. By adjusting the reaction temperature and gas flow rate, the doping mass percentage can be controlled between 20% and 60%, which can precisely control the refractive index of the fiber core, making it higher than that of the outer cladding. This ensures stable total internal reflection transmission of optical signals within the fiber core and provides excellent waveguide conditions for gain output. At the same time, this ratio range can be matched with doping elements such as Bi, La, and Y, avoiding the impact of refractive index imbalance on the overall optical performance of the fiber, and improving process controllability and product stability.

[0036] S50, the third-doped quartz tube is baked a second time in an oxygen atmosphere to obtain the fourth-doped quartz tube.

[0037] Specifically, step S50 also includes: Oxygen is introduced into the third-doped quartz tube, and under conditions of 1950℃~2100℃, the third-doped quartz tube containing BiCl3, LaCl3, and YCl3 is transformed into a transparent glassy state containing Yb2O3, La2O3, and Y2O3; the S50 step mainly involves the following chemical reactions: 4BiCl 3+ 3O2→2Bi2O 3+ 6Cl2↑; 4LaCl 3+ 3O2→2La2O 3+ 6Cl2↑;4YCl 3+ 3O2→2Y2O 3+ 6Cl2↑.

[0038] Furthermore, the high temperature of 1950℃~2100℃ combined with an oxygen atmosphere ensures that BiCl3, LaCl3, and Ycl3 are completely converted into Bi2O3, La2O3, and Y2O3, resulting in a full and thorough chemical reaction. The generated oxides are the core carriers of bismuth-associated active centers (BACS) in optical fibers, with Bi2O3 providing the foundation for gain performance and La2O3 and Y2O3 enhancing the activity and stability of BACS. At the same time, the Cl2 gas generated in the reaction is discharged to avoid impurity residue, and the transparent glassy state formed after the conversion can reduce light scattering loss and ensure the optical uniformity of the optical fiber, laying the material and structural foundation for subsequent processes and the high gain performance of the final optical fiber.

[0039] S60 involves scalding the fourth doped quartz tube into a quartz preform, inserting it into a quartz sleeve, and drawing it into a bismuth-doped optical fiber in a drawing tower.

[0040] Specifically, step S60 also includes: First, the fourth-doped quartz tube is sintered at 1900~2200℃ with the internal pressure adjusted to 75pa~200pa to shrink it into a transparent quartz preform. Then, the quartz preform is inserted into a quartz sleeve (tube-rod method) and drawn in a drawing tower to form a bismuth-doped optical fiber with a size of 4 / 125 (core diameter of 4μm and cladding diameter of 125μm).

[0041] Accordingly, the present invention also provides a bismuth-doped optical fiber, which is prepared by any of the above-described methods for preparing bismuth-doped optical fibers.

[0042] Accordingly, the present invention also provides an amplification application of the bismuth-doped optical fiber as described in any of the above claims in the C+L full-band.

[0043] The technical solution of this application will now be described in conjunction with specific embodiments.

[0044] Example 1: Embodiment 1 of the present invention provides a bismuth-doped optical fiber, which includes the following steps: Step 1: Silicon tetrachloride and oxygen are introduced into a pure quartz glass tube by vapor deposition, and a loose and porous silica layer is deposited at a high temperature of 1600℃ to obtain the reaction tube. Step two, immerse the above reaction tube in a solution containing Bi. 3+ La 3+ and Y 3+ The solution was soaked in a doped solution for 8 hours before being removed; among which, Bi 3+ The concentration for preparation is 45~46 g / L, La 3+ The concentration for preparation is 0.5~0.6 g / L, Y 3+ The concentration of the solution is 0.7~0.8 g / L, and the immersion temperature is 40℃; the quartz reaction tube is kept rotating during immersion at a speed of 30 r / min. Step 3: The above doped solution is taken out from the reaction tube and dried with nitrogen gas to obtain a first doped quartz tube containing BiCl3, LaCl3 and YCl3. Step 4: Heat the first doped quartz tube to 1200℃ in a chlorine atmosphere to obtain the second doped quartz tube; Step 5: Germanium tetrachloride and oxygen are introduced into the second-doped quartz tube, and a germanium dioxide doped layer is deposited at a temperature of 1400~1500℃ to obtain the third-doped quartz tube; wherein, the doping mass percentage of the germanium dioxide doped layer is controlled to be 50% by adjusting the reaction temperature and gas flow rate. Step six: Pass oxygen through the third doped quartz tube and bake it at 2000℃ to convert the third doped quartz tube containing BiCl3, LaCl3 and YCl3 into a transparent glassy state containing Yb2O3, La2O3 and Y2O3, thus obtaining the fourth doped quartz tube.

[0045] Step 7: Heat the fourth doped quartz tube to 2100℃, adjust the pressure inside the tube to 75pa~200pa, and scald it into a transparent quartz preform. Step 8: The quartz preform is drawn into a bismuth-doped optical fiber with a size of 4 / 125 in a drawing tower using the tube-rod method.

[0046] Example 2: This embodiment 2 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the Bi content of the doping solution used in step three is different. 3+ and La 3+ The concentration of Y is the same as in Example 1. 3+ The concentration for preparation is 1.6~1.7 g / L.

[0047] Example 3: This embodiment 3 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the Bi content of the doping solution used in step 3 is different. 3+ and La 3+ The concentration of Y is the same as in Example 1. 3+ The concentration for preparation is 7.8~7.9 g / L.

[0048] Example 4: This embodiment 4 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the Bi content of the doping solution used in step three is different. 3+ and Y 3+ The concentration of La was the same as in Example 1. 3+ The concentration for preparation is 2.2~2.3 g / L.

[0049] Example 5: This embodiment 5 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the doping solution used in step three contains only Bi. 3+ The concentration of La was the same as in Example 1. 3+ The concentration for preparation is 2.2~2.3 g / L, Y 3+ The concentration for preparation is 1.6~1.7 g / L.

[0050] Example 6: This embodiment 6 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the doping solution used in step three contains only Bi. 3+ The concentration of La was the same as in Example 1. 3+ The concentration for preparation is 2.2~2.3 g / L, Y 3+ The concentration for preparation is 7.8~7.9 g / L.

[0051] Example 7: This embodiment 7 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the Bi content of the doping solution used in step three is different. 3+ and Y 3+ The concentration of La was the same as in Example 1. 3+ The concentration for preparation is 10.6~10.7 g / L.

[0052] Example 8: This embodiment 8 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the doping solution used in step three contains only Bi. 3+ The concentration of La was the same as in Example 1. 3+ The concentration for preparation is 10.6~10.7 g / L, Y 3+ The concentration for preparation is 1.6~1.7 g / L.

[0053] Example 9: This embodiment 9 provides a bismuth-doped optical fiber. The other steps are the same as in embodiment 1, except that the doping solution used in step three contains only Bi. 3+ The concentration of La was the same as in Example 1. 3+ The concentration for preparation is 10.6~10.7 g / L, Y 3+ The concentration for preparation is 7.8~7.9 g / L.

[0054] Comparative Example 1: Comparative Example 1 provides a bismuth-doped optical fiber, with other steps being the same as in Example 1, except that the doping solution used in step three contains only Bi. 3+ The concentration of La was the same as in Example 1. 3+ The concentration of Y is 0. 3+ The concentration of the solution is 0.

[0055] Evaluation Test: The bismuth-doped optical fibers prepared in Examples 1-9 and Comparative Example 1 were respectively connected to... Figure 2 Gain and noise spectrum tests are performed using the fiber optic testing apparatus shown. The fiber optic testing apparatus, along the signal propagation direction, includes a signal source, a first optical isolator (ISO), a first wavelength division multiplexer (WDM), a bismuth-doped fiber, a second wavelength division multiplexer, a second optical isolator, and an optical spectrometer (OSA) connected sequentially. The pump end of the first wavelength division multiplexer is connected to a first pump laser diode (Pump LD), and the pump end of the second wavelength division multiplexer is connected to a second pump laser diode.

[0056] Specifically, the signal source outputs signal light at 1524~1626nm with a 120-wavelength beam and an output power of -6dBm; both the first and second pump laser diodes output 1480nm pump light with a fixed pump power of 612mW; a spectrometer was used to test the gain and noise spectra of the bismuth-doped fibers prepared in Examples 1-9 and Comparative Example 1, and the test results are shown in Table 1 below: Table 1 Test Results

[0057] As shown in Table 1, compared to the absence of La... 3+ and Y 3+ Comparative Example 1 (gain -2.3dB, noise 8.2dB at 1524nm), all with added La...3+ and Y 3+ Examples 1-9 all showed significantly better gain and noise performance at 1524 nm, indicating that La 3+ and Y 3+ The introduction of [a specific element] can effectively improve the negative gain problem of bismuth-doped fiber at 1524nm and reduce noise; furthermore, by adjusting La... 3+ (0.5~10.7g / L) and Y 3+ At concentrations of (0.7~7.9 g / L), the gain at 1524 nm in Examples 2~9 all turned positive (0.2~1.4 dB), with Example 5 (La) showing the highest gain. 3+ The concentration for preparation is 2.2~2.3 g / L, Y 3+ The formulation with a concentration of 1.6~1.7 g / L showed the best overall performance in terms of gain (1.2 dB) and noise (6.6 dB), indicating that La 3+ and Y 3+ Concentration synergistic optimization can further improve fiber gain and reduce noise, confirming the effectiveness of Bi³⁺ and La. 3+ Y 3+ The component ratio matching plays a key role in solving the negative gain problem in the C+L band (especially at 1524nm) of bismuth-doped optical fibers and improving their optical performance.

[0058] In summary, unlike existing technologies, this invention provides a bismuth-doped optical fiber, its preparation method, and its application. The method includes: first, depositing a porous silica layer on the inner wall of a quartz tube to obtain a reaction tube; second, immersing the reaction tube in a solution containing Bi... 3+ La 3+ and Y 3+The first doped quartz tube is obtained by drying it in an inert dry atmosphere in a doping solution. Then, the first doped quartz tube is baked for the first time in a dry gas atmosphere to obtain a second doped quartz tube. Next, a germanium dioxide doped layer is deposited on the inner wall of the second doped quartz tube to obtain a third doped quartz tube. Next, the third doped quartz tube is baked for the second time in an oxygen atmosphere to obtain a fourth doped quartz tube. Finally, the fourth doped quartz tube is sintered into a quartz preform and inserted into a quartz sleeve, and then drawn into a bismuth-doped optical fiber in a drawing tower. The bismuth-doped optical fiber prepared by this invention achieves positive gain output across the entire C+L band through the synergistic effect of Bi, Ge, La, and Y and optimization of component ratios. Bi, as the core active component, forms the basis for bismuth-associated active centers (BACS) and generates near-infrared gain. La and Y, as co-doped elements, significantly increase the concentration of BACS and suppress its non-radiative transition loss, effectively enhancing the fiber's gain efficiency. Ge is used to adjust the core refractive index, ensuring stable transmission of optical signals within the core and providing good waveguide conditions for gain output. Furthermore, by rationally adjusting the component ratios of Bi, Ge, La, and Y, the activity of BACS, refractive index matching, and gain bandwidth coverage can be further synergistically optimized. This solves the negative gain problem of traditional bismuth-doped optical fibers in the C+L band (especially at 1524 nm) and reduces fiber noise, ultimately achieving stable positive gain across the entire band and enhancing the practical value of bismuth-doped optical fibers in broadband communication systems.

[0059] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0060] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method of making a bismuth-doped optical fiber, comprising: The preparation method comprises the following steps: S10, depositing a loose silica layer on the inner wall of a quartz tube to obtain a reaction tube; S20, soaking the reaction tube in a doping solution containing Bi 3+ , La 3+ and Y 3+ , and drying under an inert dry atmosphere to obtain a first doped quartz tube; the prepared concentration of Bi 3+ in the doping solution is 5-100 g / L, the prepared concentration of La 3+ is 0.1-15 g / L, and the prepared concentration of Y 3+ is 0.1-15 g / L; S30, performing first baking treatment on the first doped quartz tube in a dry gas atmosphere to obtain a second doped quartz tube; S40, depositing a germanium dioxide doped layer on the inner wall of the second doped quartz tube to obtain a third doped quartz tube; S50, performing second baking treatment on the third doped quartz tube in an oxygen atmosphere to obtain a fourth doped quartz tube; S60, inserting the fourth doped quartz tube into a quartz sleeve after being shrunk into a quartz preform rod, and drawing the fourth doped quartz tube into a bismuth-doped optical fiber in a drawing tower.

2. The method of claim 1, wherein the bismuth-doped optical fiber is prepared by the steps of: The S10 step specifically comprises: introducing silicon tetrachloride and oxygen into the quartz tube at 1530-1710 DEG C to obtain the reaction tube.

3. The method of claim 1, wherein the bismuth-doped optical fiber is prepared by the steps of: In the S20 step, the soaking time is 2-10 h, the soaking temperature is 20-60 DEG C, and the reaction tube is kept rotating at a speed of 10 r / min-50 r / min during the soaking process.

4. The method of claim 1, wherein the bismuth-doped optical fiber is prepared by the steps of: In the S30 step, the dry atmosphere is nitrogen or chlorine, and the baking temperature of the first baking treatment is 1100-1300 DEG C.

5. The method of claim 1, wherein the bismuth-doped optical fiber is prepared by the steps of: The S40 step specifically comprises: introducing germanium tetrachloride and oxygen into the second doped quartz tube at 1400-1500 DEG C to obtain the third doped quartz tube.

6. The method of making a bismuth-doped optical fiber according to claim 5, wherein, The doping mass percentage of the germanium dioxide doped layer is 20%-60%.

7. The method of claim 1, wherein the bismuth-doped optical fiber is prepared by the steps of: In the S50 step, the baking temperature of the second baking treatment is 1950 DEG C-2100 DEG C. ​ 8. The method of claim 1, wherein the bismuth-doped optical fiber is prepared by the steps of: In the S60 step, the temperature for shrinking the fourth doped quartz tube is 1900-2200 DEG C, and the tube internal pressure of the fourth doped quartz tube during the shrinking is 75-200 Pa. ​ 9. A bismuth-doped optical fiber, characterized by, The bismuth-doped optical fiber is prepared by the preparation method of the bismuth-doped optical fiber according to any one of claims 1-8.

10. The bismuth-doped optical fiber according to claim 9 is applied to amplification in a C+L wave band.

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