Er / bi co-doped broadband luminescence optical fiber with multilayer composite structure and preparation method thereof

Abstract

A multilayer composite Er / Bi co-doped broadband light-emitting fiber and its fabrication method are disclosed. The fiber core comprises an Er-doped layer, an isolation layer, and a Bi-doped layer from the outside to the inside, and is fabricated using a modified chemical vapor deposition (MCVD) combined with a solution immersion process. The Er-doped layer is composed of Er / Al / Ge / Si elements, the isolation layer is composed of Ge / Si elements, and the Bi-doped layer is composed of Bi / Ge / Si elements. This invention provides a simple fiber structure. By designing the Ge / Si co-doped isolation layer, the doping sequence of luminescent ions and the thickness ratio of the isolation layer to the doped region are controlled, thus regulating the coordination environment of the luminescent ions. This improves the luminescence efficiency of erbium ions while avoiding the formation of short-wavelength bismuth luminescence centers (BAC-Al) in the bismuth-doped region. Furthermore, the light emission flatness is improved by micro-doping Er ions and adjusting the core refractive index, resulting in an fiber with advantages such as strong fluorescence intensity and a wide gain spectrum in the 1250–1600 nm range.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber technology, specifically relating to a multilayer composite Er / Bi co-doped broadband light-emitting optical fiber and its preparation method. Technical Background

[0002] The commercialization of 5G communication systems has spurred the development of a series of 5G+ industries and propelled my country into the era of an intelligent society. Against this backdrop, the demand for data communication is experiencing explosive growth, urgently requiring the expansion of the single-fiber transmission bandwidth of fiber amplifiers in dense wavelength division multiplexing (DWDM) systems. The gain bandwidth of traditional Er-doped fiber amplifiers is limited by the 4f energy level transition characteristics of rare-earth ions, currently only covering the C–L+ band, severely restricting the development of optical communication systems.

[0003] Bi, a main group element, forms the following active centers (BACs) in different matrices: BAC-Al, BAC-P, BAC-Si, and BAC-Ge, with emission peaks at ~1100 nm, ~1300 nm, ~1400 nm, and ~1700 nm, respectively. Therefore, when Bi ions are excited by pump sources of different wavelengths, they can produce ultra-wideband emission in the 1000–1800 nm band. Co-doping bismuth and erbium into quartz glass can achieve fluorescence output covering the entire wavelength range. Bismuth-erbium co-doped quartz fiber has potential value in realizing the commercial application of ultra-wideband amplification. Literature (Journal of Applied Physics, 2021, Vol. 129, 053104) indicates that the coordination environment of Al ions can significantly extend the fluorescence bandwidth of Er ions in the C-band; therefore, Al ions are commonly used co-dopers in Er-doped fibers. In 2015, Chinese patent 201510941655.3 proposed using atomic layer deposition (ALD) technology to deposit Bi and Er ions, or Bi, Er, and Al ions alternately, into the fiber core to prepare a Bi / Er or Bi / Er / Al co-doped silica fiber, but no fiber performance was reported. In 2020, Chinese patent 202010073619.0 proposed a Bi / Er / La / Al co-doped silica fiber, but this fiber only exhibited broadband fluorescence in the 1530–1625 nm range. In 2022, Chinese patent 202210725906.4 proposed combining MCVD and ALD processes to prepare an Er / Bi co-doped silica fiber with a reduced C+ band noise figure. Its Er ion doping concentration was greater than 5000 ppm. Because the luminescence intensity of rare-earth Er ions is much higher than that of main group Bi ions, the amplifier's L+ band noise figure is high. Furthermore, these patents primarily utilize alternating deposition of doped ions. However, the low deposition efficiency of ALD leads to high costs, and the single-layer deposition thickness is on the nanometer scale. Al and Bi elements still form short-wavelength luminescent centers (BAC-Al), severely hindering the formation of long-wavelength luminescent centers for bismuth ions. Therefore, there is an urgent need to develop low-loss, high-efficiency, and gain-flat Er / Bi co-doped silica fibers from the perspective of fiber structure and fabrication technology. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a multilayer composite Er / Bi co-doped broadband light-emitting fiber and its fabrication method.

[0005] In a first aspect, this invention provides a multilayer composite Er / Bi co-doped broadband light-emitting optical fiber. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with a maximum Er ion doping concentration of 500 ppm. The isolation layer is composed of Ge / Si elements. The Bi-doped layer is composed of Bi / Ge / Si elements, with a maximum Bi ion doping concentration of 2000 ppm. The refractive indices of the fiber cladding, Er-doped layer, isolation layer, and Bi-doped layer are respectively n 包层 n1, n2 and n3.

[0006] Preferably, the thickness ratio of the isolation layer to the Er-doped layer is 6 to 10.

[0007] The refractive index relationship is n 包层 <(n1,n2)≤n3, │n1-n2│≤0.001.

[0008] The molar ratio of Al ions to Er ions in the Er-doped layer is 10 to 100.

[0009] The GeO2 doping content in the Bi-doped layer is no higher than 15 mol%.

[0010] A second aspect of the present invention provides a method for fabricating Er / Bi co-doped broadband light-emitting optical fiber with a multilayer composite structure. Based on MCVD combined with a solution immersion process, in another preferred embodiment, the fabrication of the optical fiber includes the following steps:

[0011] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0012] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 6-10.

[0013] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0014] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0015] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0016] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0017] A third aspect of the present invention provides a multilayer composite Er / Bi co-doped broadband light-emitting optical fiber, which is prepared by at least the preparation method described in the second aspect of the present invention. The fiber core includes at least an Er-doped layer, an isolation layer, and a Bi-doped layer. The background loss of the optical fiber is as low as 7.7 dB / km@1100 nm, and it can achieve ultra-wideband light emission of 1250–1600 nm with a 6 dB bandwidth of 235 nm.

[0018] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention introduces Er and Bi ions in layers, ensuring that Er ions are located in a coordination environment containing Al ions, while Bi ions form BAC-Si active centers. An isolation layer is deposited between the Er-doped layer and the Bi-doped layer. By controlling the thickness ratio of the isolation layer to the Er-doped layer, Al ions are prevented from diffusing into the Bi-doped layer, thus eliminating the formation of short-wavelength luminescent centers, BAC-Al.

[0021] 2. This invention avoids gain unevenness caused by the large difference in intrinsic luminescence intensity between rare earth ions Er and main group ions Bi by using low Er doping content; at the same time, by adjusting the refractive index of the pure quartz cladding, the Er-doped core layer and the isolation layer, and the Bi-doped layer, the pump efficiency of the Bi-doped layer is effectively improved, which can further reduce the noise figure of the corresponding fiber amplifier.

[0022] 3. This invention uses BiCl3 as the Bi source precursor. Compared to organic bismuth raw materials, BiCl3 is non-toxic and environmentally friendly, and does not cause fiber optic loss or increase hydroxyl content due to the introduction of C and H elements.

[0023] 4. This invention can be completed using an MCVD device, with simple steps, high operability, and high efficiency. In contrast, ALD devices have low deposition efficiency and require combination with MCVD, making operation complex.

[0024] 5. The Er / Bi co-doped broadband light-emitting fiber with a multilayer composite structure described in this invention has a background loss as low as 7.7 dB / km @ 1100 nm. Under co-excitation at 808 nm and 980 nm, the fiber described in this invention can achieve ultra-wideband light emission of 1250–1600 nm, with a 6 dB bandwidth of 235 nm. It has significant application value in the field of ultra-wideband optical communication for fiber amplifiers and tunable light sources. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the Er / Bi co-doped broadband light-emitting fiber with a multilayer composite structure according to the present invention.

[0026] Figure 2 The fluorescence spectra of single-doped Er fiber, single-doped Bi fiber, and Er / Bi co-doped broadband light-emitting fiber of the multilayer composite structure of the present invention are shown under co-excitation at 808 nm and 980 nm, respectively.

[0027] Figure 3 The image shows the core loss spectrum of the Er / Bi co-doped broadband light-emitting fiber with the multilayer composite structure of this invention. The inset is a cross-sectional view of the fiber. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0029] Example 1: (Table 1)

[0030] A multilayer composite Er / Bi co-doped broadband light-emitting fiber is disclosed. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with an Er ion doping concentration of 50 ppm, an Al₂O₃ doping concentration of 0.096 mol%, and a refractive index of 1.4590. The isolation layer is composed of Ge / Si elements, with a refractive index of 1.4600. The Bi-doped layer is composed of Bi / Ge / Si elements, with a Bi ion doping concentration of 1000 ppm, a GeO₂ doping concentration of 15 mol%, and a refractive index of 1.4695. The thickness ratio of the isolation layer to the Er-doped layer is 3. This embodiment of the Er / Bi co-doped fiber is prepared using the MCVD method combined with solution doping technology. The method includes the following steps:

[0031] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0032] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 3;

[0033] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0034] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0035] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0036] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0037] Using semiconductor lasers with operating wavelengths of 808nm and 980nm as pump sources, the optical fiber can achieve ultra-wideband emission in the 1250–1600nm band.

[0038] Example 2: (Table 1, Table 2, ...) Figure 2 and Figure 3 )

[0039] A multilayer composite Er / Bi co-doped broadband light-emitting fiber is disclosed. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with an Er ion doping concentration of 50 ppm, an Al₂O₃ doping concentration of 0.096 mol%, and a refractive index of 1.4590. The isolation layer is composed of Ge / Si elements, with a refractive index of 1.4600. The Bi-doped layer is composed of Bi / Ge / Si elements, with a Bi ion doping concentration of 1000 ppm, a GeO₂ doping concentration of 15 mol%, and a refractive index of 1.4695. The thickness ratio of the isolation layer to the Er-doped layer is 6. This embodiment of the Er / Bi co-doped fiber is prepared using the MCVD method combined with solution doping technology. The method includes the following steps:

[0040] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0041] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 6;

[0042] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0043] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0044] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0045] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0046] The optical fiber has a loss of 7.7 dB / km at a wavelength of 1100 nm. Using semiconductor lasers with operating wavelengths of 808 nm and 980 nm as pump sources, the optical fiber can achieve ultra-wideband emission in the 1250–1600 nm band, with a 6 dB bandwidth of 235 nm. Figure 2 As shown.

[0047] Example 3: (Table 1)

[0048] A multilayer composite Er / Bi co-doped broadband light-emitting fiber is disclosed. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with an Er ion doping concentration of 50 ppm, an Al₂O₃ doping concentration of 0.096 mol%, and a refractive index of 1.4590. The isolation layer is composed of Ge / Si elements, with a refractive index of 1.4600. The Bi-doped layer is composed of Bi / Ge / Si elements, with a Bi ion doping concentration of 1000 ppm, a GeO₂ doping concentration of 15 mol%, and a refractive index of 1.4695. The thickness ratio of the isolation layer to the Er-doped layer is 10. This embodiment of the Er / Bi co-doped fiber is prepared using the MCVD method combined with solution doping technology. The method includes the following steps:

[0049] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0050] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 10.

[0051] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0052] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0053] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0054] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0055] Using semiconductor lasers with operating wavelengths of 808nm and 980nm as pump sources, the optical fiber can achieve ultra-wideband emission in the 1250–1600nm band.

[0056] Example 4: (Table 1)

[0057] A multilayer composite Er / Bi co-doped broadband light-emitting fiber is disclosed. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with an Er ion doping concentration of 500 ppm, an Al₂O₃ doping concentration of 0.95 mol%, and a refractive index of 1.4592. The isolation layer is composed of Ge / Si elements, with a refractive index of 1.4600. The Bi-doped layer is composed of Bi / Ge / Si elements, with a Bi ion doping concentration of 1000 ppm, a GeO₂ doping concentration of 15 mol%, and a refractive index of 1.4695. The thickness ratio of the isolation layer to the Er-doped layer is 6. This embodiment of the Er / Bi co-doped fiber is prepared using the MCVD method combined with solution doping technology. The method includes the following steps:

[0058] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0059] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 6;

[0060] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0061] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0062] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0063] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0064] Using semiconductor lasers with operating wavelengths of 808nm and 980nm as pump sources, the optical fiber can achieve ultra-wideband emission in the 1250–1600nm band.

[0065] Example 5: (Table 1)

[0066] A multilayer composite Er / Bi co-doped broadband light-emitting fiber is disclosed. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with an Er ion doping concentration of 50 ppm, an Al₂O₃ doping concentration of 0.096 mol%, and a refractive index of 1.4590. The isolation layer is composed of Ge / Si elements, with a refractive index of 1.4600. The Bi-doped layer is composed of Bi / Ge / Si elements, with a Bi ion doping concentration of 2000 ppm, a GeO₂ doping concentration of 15 mol%, and a refractive index of 1.4698. The thickness ratio of the isolation layer to the Er-doped layer is 6. This embodiment of the Er / Bi co-doped fiber is prepared using the MCVD method combined with solution doping technology. The method includes the following steps:

[0067] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0068] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 6;

[0069] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0070] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0071] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0072] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0073] Using semiconductor lasers with operating wavelengths of 808nm and 980nm as pump sources, the optical fiber can achieve ultra-wideband emission in the 1250–1600nm band.

[0074] Example 6: (Table 1)

[0075] A multilayer composite Er / Bi co-doped broadband light-emitting fiber is disclosed. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with an Er ion doping concentration of 50 ppm, an Al₂O₃ doping concentration of 0.0096 mol%, and a refractive index of 1.4590. The isolation layer is composed of Ge / Si elements, with a refractive index of 1.4600. The Bi-doped layer is composed of Bi / Ge / Si elements, with a Bi ion doping concentration of 1000 ppm, a GeO₂ doping concentration of 15 mol%, and a refractive index of 1.4695. The thickness ratio of the isolation layer to the Er-doped layer is 6. This embodiment of the Er / Bi co-doped fiber is prepared using the MCVD method combined with solution doping technology. The method includes the following steps:

[0076] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0077] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 6;

[0078] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0079] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0080] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0081] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0082] Using semiconductor lasers with operating wavelengths of 808nm and 980nm as pump sources, the optical fiber can achieve ultra-wideband emission in the 1250–1600nm band.

[0083] Example 7: (Table 1)

[0084] A multilayer composite Er / Bi co-doped broadband light-emitting fiber is disclosed. The fiber core comprises, from the outside to the inside, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with an Er ion doping concentration of 50 ppm, an Al₂O₃ doping concentration of 0.095 mol%, and a refractive index of 1.4570. The isolation layer is composed of Ge / Si elements, with a refractive index of 1.4560. The Bi-doped layer is composed of Bi / Ge / Si elements, with a Bi ion doping concentration of 1000 ppm, a GeO₂ doping concentration of 5 mol%, and a refractive index of 1.4565. The thickness ratio of the isolation layer to the Er-doped layer is 6. This embodiment of the Er / Bi co-doped fiber is prepared using the MCVD method combined with solution doping technology. The method includes the following steps:

[0085] Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification.

[0086] Step 2) Preparation of core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃ until the thickness ratio of the isolation layer to the Er-doped layer is 6;

[0087] Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification.

[0088] Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod;

[0089] Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

[0090] The dehydration refers to introducing chlorine gas into the deposition tube and heating the deposition tube to 800-1000°C; the vitrification refers to introducing oxygen into the deposition tube and heating the deposition tube to 1800-2000°C.

[0091] Using semiconductor lasers with operating wavelengths of 808nm and 980nm as pump sources, the optical fiber can achieve ultra-wideband emission in the 1250–1600nm band.

[0092] Table 1 shows the influence of the multilayer composite structure composition, refractive index of each layer, and thickness ratio of the insulating layer to the Er-doped layer on the optical fiber performance in Examples 1-7.

[0093]

[0094]

[0095] Table 2. Fiber performance in Example 2 and Comparative Example

[0096]

[0097] The optical fiber structure of this invention is simple. By designing a Ge / Si co-doped isolation layer, the doping sequence of luminescent ions and the thickness ratio of the isolation layer to the doped region are controlled, precisely regulating the coordination environment of the luminescent ions. This improves the luminescence efficiency of erbium ions while effectively preventing the formation of short-wavelength bismuth luminescence centers (BAC-Al) in the bismuth-doped region. Simultaneously, the luminescence flatness is improved by micro-doping with Er ions and adjusting the core refractive index, resulting in an optical fiber with strong fluorescence intensity and a wide gain spectrum in the 1250–1600 nm range. Furthermore, the low-loss ultrawideband Er / Bi co-doped optical fiber can be fabricated using only an MCVD device. The fabrication process is simple, highly operable, and efficient, while also being cost-effective. This makes it of significant application value in fiber amplifiers and tunable light sources in the field of ultrawideband optical communication.

[0098] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it will be readily understood by those skilled in the art that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A multilayer composite Er / Bi co-doped broadband light-emitting optical fiber, characterized in that, The fiber core comprises, from the outside in, an Er-doped layer, an isolation layer, and a Bi-doped layer. The Er-doped layer is composed of Er / Al / Ge / Si elements, with a maximum Er ion doping concentration of 500 ppm. The isolation layer is composed of Ge / Si elements. The Bi-doped layer is composed of Bi / Ge / Si elements, with a maximum Bi ion doping concentration of 2000 ppm. The thickness ratio of the isolation layer to the Er-doped layer does not exceed 10. The refractive indices of the cladding, Er-doped layer, isolation layer, and Bi-doped layer of the fiber are respectively n 包层 The refractive index relationship between n1, n2, and n3 is n 包层 <(n1,n2)≤n3, │n1-n2│≤0.

001.

2. The Er / Bi co-doped broadband light-emitting optical fiber with a multilayer composite structure according to claim 1, characterized in that, The molar ratio of Al ions to Er ions in the Er-doped layer is 10 to 100.

3. The multilayer composite Er / Bi co-doped broadband light-emitting optical fiber according to claim 1, characterized in that, The GeO2 doping content in the Bi-doped layer is no higher than 15 mol%.

4. The Er / Bi co-doped broadband light-emitting optical fiber with a multilayer composite structure according to claim 1, characterized in that, The optical fiber has a background loss as low as 7.7dB / km@1100nm, enabling ultra-wideband emission of 1250–1600nm, with a 6dB bandwidth of 235nm.

5. A method for fabricating a multilayer composite Er / Bi co-doped broadband light-emitting optical fiber, characterized in that... It includes the following steps: Step 1) Preparation of Er-doped core: After etching with SF6, SiO2 and GeO2 porous material is deposited in the deposition tube, and the deposition tube is immersed in an ethanol solution containing Al and Er elements for dehydration and vitrification. Step 2) Preparation of the fiber core isolation layer: SiO2 and GeO2 layers are deposited on the vitrified Er-doped layer at a temperature of 1800-2000℃; Step 3) Preparation of Bi-doped core layer: SiO2 and GeO2 porous material are deposited on the vitrified isolation layer, and the deposition tube is immersed in BiCl3 ethanol solution for dehydration and vitrification. Step 4) Collapse: Heat the deposition tube to above 2200℃ to cause the deposition tube to collapse into a solid rod; Step 5) Fiber drawing: The fiber preform is placed into the fiber drawing tower to form an optical fiber. The fiber is coated with adhesive and cured to obtain the desired optical fiber.

6. The method for fabricating a multilayer composite Er / Bi co-doped broadband light-emitting optical fiber according to claim 5, characterized in that, The dehydration process involves introducing chlorine gas into the deposition tube and heating the deposition tube to 800–1000°C.

7. The method for fabricating a multilayer composite Er / Bi co-doped broadband light-emitting optical fiber according to claim 5, characterized in that, Vitrification refers to the process of introducing oxygen into the deposition tube and heating the deposition tube to 1800–2000°C.

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