WO2023169442A1

WO2023169442A1 - Doped optical fiber, optical fiber amplifier and preparation method for doped optical fiber

Info

Publication number: WO2023169442A1
Application number: PCT/CN2023/080167
Authority: WO
Inventors: 童朝阳; 顾劭忆; 任军江; 严洒洒
Original assignee: 华为技术有限公司; 上海传输线研究所（中国电子科技集团公司第二十三研究所）
Priority date: 2022-03-08
Filing date: 2023-03-07
Publication date: 2023-09-14
Also published as: CN116768464A

Abstract

Provided in the embodiments of the present application are a doped optical fiber, an optical fiber amplifier and a preparation method for the doped optical fiber. A fiber core of the doped optical fiber contains doping ions which comprise at least one of ytterbium ions and lanthanum ions, and erbium ions, phosphorus ions and aluminum ions, and a small amount of germanium ions or fluorine ions. At least one of ytterbium ions and lanthanum ions is used to co-dope the fiber core together with erbium ions, thus effectively increasing the doping concentration and light-emitting efficiency of erbium ions, and further improving the gain performance and gain bandwidth of the doped optical fiber. In addition, broadband gain of the doped optical fiber in an extended C waveband and an extended L waveband can be realized by means of high doping of aluminum ions and phosphorus ions, so that the problem of a relatively narrow gain bandwidth of an existing doped optical fiber is solved.

Description

Preparation method of doped optical fiber, optical fiber amplifier and doped optical fiber

This application requires the priority of the Chinese patent application submitted to the China Patent Office on March 8, 2022, with the application number 202210227638.3 and the application title "A doped optical fiber, optical fiber amplifier and preparation method of doped optical fiber", all of which The contents are incorporated into this application by reference.

Technical field

The present application relates to the technical field of optical fiber communication, and in particular to a doped optical fiber, an optical fiber amplifier and a preparation method of the doped optical fiber.

Background technique

Optical fiber communication has become the technical pillar of backbone high-speed communication networks. Among them, optical fiber amplifier (Optical Fiber Amplifier; OFA) is an all-optical amplifier used in optical fiber communication systems to amplify optical signals to achieve high gain and wide bandwidth. , low-noise full amplification function, is an indispensable key component in the new generation of optical fiber communication systems.

Currently, with the increase in transmission capacity, higher requirements have been placed on the operating bandwidth of amplifier fibers. Among them, doped fiber amplifiers have received widespread attention due to their low noise, high gain, and wide frequency bandwidth. The key core of doped optical fiber amplifiers is doped optical fiber. The common one is Erbium ion-doped fiber amplifier (Erbium Doped Fiber Amplifier; EDFA). The gain bandwidth band of erbium ions is about 1530nm-1560nm, which is consistent with the lowest loss band of optical fiber. , so erbium-doped optical fiber is widely used. Specifically, during the process of making the optical fiber, a certain concentration of erbium ions is doped into the core layer deposition of the optical fiber, thereby forming an optical fiber including an Er ion component system in the core layer of the optical fiber.

However, the gain bandwidth of the above-mentioned doped optical fibers is narrow and cannot meet the amplification performance requirements of fiber amplifiers in a wider bandwidth range.

Contents of the invention

Embodiments of the present application provide a doped fiber, a fiber amplifier and a method for preparing the doped fiber, which solves the problem that the existing doped fiber has a narrow gain bandwidth and affects the broadband amplification performance of the fiber amplifier.

On the one hand, embodiments of the present application provide a doped optical fiber, including a fiber core containing doping ions;

The doping ions include at least: at least one of ytterbium ions and lanthanum ions, erbium ions, phosphorus ions, aluminum ions, and doping ions A, wherein the doping ions A are germanium ions or fluorine ions;

The doping concentration of the aluminum ions is 0.5wt%-12wt%.

By doping erbium ions in the optical fiber, the main luminescence center of the erbium ions is near 1530nm, and the gain bandwidth covers 1530nm-1560nm. This is consistent with the minimum loss band of the optical fiber, that is, the commonly used C-band, and is conducive to exerting its gain. Effect. Furthermore, at least one of lanthanum ions and ytterbium ions is used as a co-doped ion of erbium ions. In other words, at least one of lanthanum ions and ytterbium ions is co-doped with erbium ions in the core, The presence of at least one ion among lanthanum ions and ytterbium ions can increase the distance between erbium ions, improve the dispersion of erbium ions, and reduce the The probability of concentration quenching due to clusters helps to increase the doping concentration of erbium ions in the fiber core, thereby improving the gain performance and gain bandwidth of the doped optical fiber. At the same time, ytterbium ions can effectively increase the absorption cross section of pump light and transfer energy to erbium ions, thereby improving the luminescence characteristics of erbium ions and further improving the gain performance and gain bandwidth of doped optical fibers.

In addition, aluminum ions and phosphorus ions can change the coordination environment of erbium ions, thereby promoting the energy level splitting of erbium ions and expanding the gain bandwidth of doped optical fibers. For example, extending the bandwidth to the L-band can further effectively improve the gain of doped optical fibers. bandwidth. In addition, a higher concentration of aluminum ions is achieved. The increase in the doping concentration of aluminum ions makes it have a stronger effect on the erbium ion coordination field, further expanding the gain bandwidth of the doped optical fiber and realizing the extended doping of the doped optical fiber. The broad-spectrum gain of the C-band also improves the gain flatness of doped optical fibers.

In a possible implementation, the doping concentration of the phosphorus ions is 0.5wt%-15wt%.

In this way, a higher concentration of phosphorus ion doping is achieved. Through the high concentration doping of phosphorus ions, its effect on the coordination field of erbium ions can be further enhanced, further expanding the gain bandwidth of the doped optical fiber, making its gain bandwidth Expand to the L-band and achieve the wide-spectrum gain of the doped fiber in the extended L-band, and also help to improve the gain flatness of the doped fiber.

In a possible implementation, the component system of the fiber core includes: at least one of ytterbium trioxide and lanthanum trioxide, erbium trioxide, silicon dioxide, phosphorus pentoxide, Alumina and component B, which is germanium dioxide or fluoride ions.

That is to say, the doping ions doped into the fiber core will exist in a relatively stable form, which is easy to implement and helps ensure the stability of the fiber core.

In a possible implementation, the doping concentration of the aluminum ions is greater than or equal to 8 wt%.

In this way, high-concentration doping of aluminum ions is achieved, which further ensures that the fiber core has a wide gain bandwidth and achieves broad-spectrum gain of the doped fiber in the extended C-band 1522nm-1572nm.

In a possible implementation, the doping concentration of the phosphorus ions is greater than or equal to 10 wt%.

In this way, high-concentration doping of phosphorus ions is achieved, which further ensures that the fiber core has a wide gain bandwidth and achieves broad-spectrum gain of the doped fiber in the extended L-band 1575nm-1627nm.

In a possible implementation, the gain bandwidth of the doped optical fiber in the C-band is greater than or equal to 50 nm, and the C-band includes 1522nm-1572nm.

This enables the doped optical fiber to have a wider gain bandwidth in the extended C-band, effectively improving the gain bandwidth of the doped optical fiber and realizing a wide-spectrum gain of the doped optical fiber in the extended C-band.

In a possible implementation, the gain bandwidth of the doped optical fiber in the L-band is greater than or equal to 52 nm, and the L-band covers at least 1575nm-1627nm.

In this way, the gain bandwidth of the doped fiber is extended to the L-band, and has a wider gain bandwidth in the extended L-band, which effectively improves the gain bandwidth of the doped fiber and achieves a wide spectrum of the doped fiber in the extended L-band. gain.

In a possible implementation, the doping concentration of the erbium ions is 200 ppm-2000 ppm.

It achieves higher concentration doping of erbium ions, increases the doping concentration of erbium ions, and ensures the improvement of the gain performance and gain bandwidth of the doped optical fiber. Moreover, while ensuring a high doping concentration of erbium ions, it can also reduce or avoid concentration quenching caused by excessively high erbium ion concentration, which affects the amplification performance of the doped optical fiber.

In a possible implementation, the doping concentration of the ytterbium ions is 200 ppm-4000 ppm.

Making the doping concentration of ytterbium ions co-doped with erbium ions within the above range can more effectively reduce the clusters of erbium ions, thereby increasing the doping concentration of erbium ions in the fiber core.

In a possible implementation, the doping concentration of the lanthanum ions is 0.5wt%-7wt%.

Setting the doping concentration of lanthanum ions in the fiber core co-doped with lanthanum ions, erbium ions, etc. to the above range can further reduce the clusters of erbium ions and help increase the doping concentration of erbium ions in the fiber core.

In a possible implementation, the doping concentration of the doping ions A is 0.1wt%-1wt%.

This ensures that the refractive index of the doped optical fiber can be effectively enhanced while reducing or avoiding the impact of too high a doping concentration of germanium ions or fluorine ions on the doping of erbium ions and the local coordination field.

In a possible implementation, it also includes a cladding layer, a first coating layer and a second coating layer, the cladding layer wraps the outer periphery of the fiber core, and the first coating layer wraps the outer periphery of the cladding layer, The second coating wraps around the periphery of the first coating.

When the signal light and pump light meet the guided wave transmission conditions and are incident into the doped fiber, total reflection will occur between the fiber core and the cladding and propagate in the doped fiber. In this process, based on the energy level structure Matching, the pump light energy will be transferred to the signal light, thereby achieving the amplification of the signal light. The first coating and the second coating located outside the core and cladding can protect the core and cladding to reduce or avoid damage to the core or cladding caused by factors such as dust, moisture, and mechanical external forces. The performance degradation or damage of the layer is ensured to ensure the life of the doped optical fiber. In addition, the doped optical fiber has two coating layers, a first coating layer and a second coating layer, which can enhance the protection of the fiber core and cladding.

In addition, the first coating and the second coating can be elastic coatings, which can give the doped optical fiber higher bending resistance and reduce the loss caused by bending of the doped optical fiber.

On the other hand, embodiments of the present application provide a method for preparing doped optical fibers, which method at least includes:

Tubular prefabricated parts are available;

A mixed gas is passed into the preform to deposit and form a doped core layer. The mixed gas includes at least one of ytterbium ions and lanthanum ions, erbium ions, silicon ions, phosphorus ions, aluminum ions, and doped core layers. Miscellaneous ions A, the doping A ions are germanium ions or fluorine ions;

Prepare a preform, and draw the preform to form a doped optical fiber, the doped core layer forms the core of the doped optical fiber, and the doping concentration of the aluminum ions in the core 0.5wt%-12wt%.

The doped core layer is formed by introducing a mixed gas into the preform for reactive deposition. In other words, during the process of depositing and forming the core layer, a mixed gas containing the above-mentioned doping ions is introduced for reactive deposition, so that the doped core layer is formed during the deposition. Doping is achieved during the core layer process. On the one hand, it helps to improve the uniformity of the distribution of the doped core layer and improve the performance of the fiber core. On the other hand, doping ions enter the fiber core layer system in the form of gas and achieve doping, which can effectively improve the uniformity of the distribution of the above-mentioned doping ions in the fiber core layer, help to further increase the doping concentration, and improve Gain performance and gain bandwidth of doped fibers.

In a possible implementation, the introducing a mixed gas into the preform to deposit and form the doped core layer includes: depositing the doped core layer into the preform by a chemical vapor deposition method. Core layer.

Forming the doped core layer through chemical vapor deposition can help improve the uniformity of the distribution of the doped core layer, thereby improving the performance of the core. At the same time, the process is relatively mature and has good practicality.

An embodiment of the present application provides an optical fiber amplifier, which at least includes a housing and any of the above-mentioned doped optical fibers, and the doped optical fiber is disposed in the housing.

By including a doped optical fiber containing at least one of ytterbium ions and lanthanum ions, erbium ions, aluminum ions, phosphorus ions and doping ions A, the doped optical fiber has higher gain performance and higher The wide gain bandwidth and good gain flatness can achieve wide spectrum gain of doped optical fiber in the extended C-band and extended L-band.

Description of the drawings

Figure 1 is a schematic cross-sectional structural diagram of a doped optical fiber provided by an embodiment of the present application;

Figure 2 is a single-stage full-wave amplification gain spectrum diagram of a doped optical fiber in the extended C-band provided by an embodiment of the present application;

Figure 3 is a single-stage full-wave amplification gain spectrum diagram of a doped optical fiber in the extended L-band provided by an embodiment of the present application;

Figure 4 is a flow chart of a method for preparing a doped optical fiber provided by an embodiment of the present application.

Explanation of reference symbols:

100-doped optical fiber;

101-fiber core;

102-cladding;

103-First coating;

104-Second coating.

Detailed ways

The terms used in the embodiments of the present application are only used to explain specific embodiments of the present application and are not intended to limit the present application.

To facilitate understanding, the relevant technical terms involved in the embodiments of this application are first explained and described.

Gain, in dB, refers to the difference in optical power (in dBm) between the output end and the input end of the optical amplifier, and is used to indicate the optical amplifier's ability to amplify/amplify the input power.

Gain bandwidth refers to the band range of gain.

The conventional C-band range is 1530nm-1565nm. Quartz-based optical fiber shows the lowest loss in the C-band, which is the conventional use band of optical fiber. In order to make better use of the low-loss transmission window of optical fiber and achieve larger-capacity wavelength division multiplexing, the application of conventional C-band has been broadened from 1530nm-1565nm to a wider range of 1524nm-1572nm, and even the 1522nm-1572nm band range, becoming Critical Path.

L-band, ranging from 1565nm-1625nm, is the second lowest loss band of quartz-based fiber. When the C-band is not enough to meet the transmission capacity/bandwidth requirements, the L-band is added for multiplexing on the same fiber to double the transmission capacity. At the same time, in order to comprehensively utilize the band allocation, it is necessary to red-shift the L-band.

As described in the background art above, doped optical fiber amplifiers are one of the commonly used devices in optical links. The increase in demand for transmission capacity has put forward higher requirements for the operating bandwidth of optical fibers. As an amplifier in an optical link, taking the commonly used erbium-doped fiber amplifier (EDFA) as an example, its gain bandwidth requirements have also gradually changed from the traditional 35nm to Upgrade to 48nm or 52nm, or wider. Fiber amplifiers use the principle of traveling wave amplification. When signal light passes through the core of the optical fiber, the doped ions that are pumped are in an excited state. The particles in the excited state produce stimulated radiation under the action of external signal light. Superimposed on the external signal light, the signal light is amplified. Therefore, in order to improve the gain bandwidth and gain performance of the erbium-doped fiber amplifier, the gain performance and gain bandwidth of the erbium-doped fiber need to be improved simultaneously.

For example, the doping concentration, doping distribution and local coordination field of erbium ions in the optical fiber can be changed by changing the components and preparation processes of the optical fiber, thereby optimizing the gain performance and gain bandwidth of the erbium-doped optical fiber. For example, by adjusting the doping concentration of erbium ions in the core of the optical fiber and co-doping at least one of the doping ions such as ytterbium ions and lanthanum ions, the luminescence characteristics of the erbium-doped optical fiber can be improved to a certain extent. to achieve improvements in gain performance and gain bandwidth.

However, the gain bandwidth of the above-mentioned doped fiber is still narrow and the gain flatness is poor.

Based on this, embodiments of the present application provide a doped optical fiber that can effectively improve the gain bandwidth of the doped optical fiber and the gain flatness of the doped optical fiber, and can realize the extended C-band and extended L-band operation of the doped optical fiber. gain.

The doped optical fiber can be applied in an amplifier, or the doped optical fiber can also be applied in other optical fiber signal equipment.

The doped optical fiber provided in the embodiment of the present application will be described in detail below with reference to the accompanying drawings.

Figure 1 is a schematic cross-sectional structural diagram of a doped optical fiber provided by an embodiment of the present application.

As shown in FIG. 1 , a doped optical fiber 100 includes a core 101 , and a cladding 102 is wrapped around the periphery of the core 101 . The molding material of the core 101 and the cladding 102 can be the same. For example, in the embodiment of the present application, the molding substrates of the core 101 and the cladding 102 can both be silica, such as quartz glass. Alternatively, the molding materials of the core 101 and the cladding 102 may also be different.

The refractive index of the core 101 is different from the refractive index of the cladding 102. For example, the refractive index of the core 101 can be greater than the refractive index of the cladding 102. The signal light is incident into the doped optical fiber 100 at a specific incident angle. Total reflection occurs between the core 101 and the cladding 102 so that propagation can be achieved within the doped optical fiber 100 .

The doped optical fiber 100 may also include a coating layer. Specifically, the coating layer may include a first coating layer 103 and a second coating layer 104, wherein the first coating layer 103 may wrap the outer periphery of the cladding layer 102. The second coating layer 104 can wrap the outer periphery of the first coating layer 103 . That is to say, with the core 101 as the center point, the core 101, the cladding 102, the first coating 103 and the second coating 104 are in order outward.

The first coating 103 and the second coating 104 can protect the core 101 and the cladding 102 to reduce or avoid contamination of the core 101 or the cladding 102 caused by factors such as dust, moisture, and mechanical external forces. and damage, ensuring the life of the fiber 100. In addition, the doped optical fiber 100 has two coating layers: a first coating 103 and a second coating 104, which can enhance the protection of the core 101 and the cladding 102.

The molding material of the first coating layer 103 and the second coating layer 104 can be an elastic coating. For example, the first coating layer 103 and the second coating layer 104 can both be UV-cured acrylic resin. The first coating 103 and the second coating 104 can provide the doped optical fiber 100 with higher bending resistance and reduce the loss caused by bending of the doped optical fiber 100 .

Of course, in some examples, the molding materials of the first coating layer 103 and the second coating layer 104 can also be other materials, or the molding materials of the first coating layer 103 and the second coating layer 104 can also be different.

In the embodiment of the present application, the fiber core 101 contains doping ions, that is, doping ions are doped into the fiber core 101 to change the composition system of the fiber core 101 . For example, in the process of forming the fiber core 101, a compound containing doping ions is added, so that the formed fiber core 101 contains doping ions.

Specifically, the doping ions include at least one of ytterbium ions (such as Yb ³⁺ ) and lanthanum ions (such as La ³⁺ ), erbium ions (such as Er ³⁺ ), phosphorus ions (such as P ⁵⁺ ), Aluminum ions (such as Al ³⁺ ), and a small amount of other doping ions A (such as Ge ⁴⁺ or F ^- ). It should be noted that the doping ions include at least one of ytterbium ions and lanthanum ions, that is, they may only include ytterbium ions, or they may only include lanthanum ions, or they may also include both ytterbium ions. The ions also include lanthanum ions.

Erbium ions, ytterbium ions and lanthanum ions are all ions formed by doping rare earth elements in the fiber core 101, and the rare earth elements can generate photons when excited. Therefore, when the optical signal passes through the fiber core 101, the erbium ions generate higher stimulated radiation in cooperation with at least one doping ion of ytterbium ions and lanthanum ions, thereby achieving amplification efficiency for the signal light, thereby achieving optical fiber amplification. Core 101 gain performance improvement.

Among them, the gain bandwidth of erbium ions is 1530nm-1560nm, which is consistent with the minimum loss band of optical fiber, that is, the commonly used C-band, thus helping to exert the gain effect of the doped optical fiber 100. Furthermore, at least one of lanthanum ions and ytterbium ions is used as a co-doped ion of erbium ions. In other words, at least one of ytterbium ions and lanthanum ions and erbium ions are co-doped in the core 101 , the presence of at least one ion among ytterbium ions and lanthanum ions can increase the distance between erbium ions, improve the dispersion of erbium ion distribution, and reduce the concentration quenching effect caused by clusters of erbium ions, thus helping to improve erbium ions. The doping concentration of ions further improves the gain performance and gain bandwidth of the doped optical fiber 100 .

Correspondingly, the co-doping of aluminum ions, phosphorus ions and doping ions A in the fiber core 101 also helps to increase the doping concentration of erbium ions, thereby improving the gain performance and gain bandwidth of the doped optical fiber 100 . Moreover, aluminum ions and phosphorus ions can change the coordination environment of erbium ions, thereby promoting the energy level splitting of erbium ions, expanding the gain bandwidth of the doped optical fiber 100, and further effectively increasing the gain bandwidth of the doped optical fiber 100.

Wherein, the doping ion A may be a germanium ion, such as Ge ⁴⁺ . Alternatively, the doping ion A may be a fluoride ion, for example, F ^- . Both germanium ions and fluorine ions can adjust the refractive index of the doped optical fiber 100 and further improve the gain performance of the doped optical fiber 100 .

It should be understood that the doping ions doped into the fiber core 101 will exist in a relatively stable form. For example, taking the doping ions including ytterbium ions and lanthanum ions as an example, the molding base material of the fiber core 101 is SiO ₂ . The doping ions in the fiber core 101 are Er ³⁺ , Yb ³⁺ , La ³⁺ , P ⁵⁺ , Al ³⁺ , and the doping ion A (Ge ⁴⁺ or F ^- ), then the final fiber core 101 is formed The component system of is: SiO ₂ -Er ₂ O ₃ -Yb ₂ O ₃ -La ₂ O ₃ -P ₂ O ₅ -Al ₂ O ₃ -B, that is, the component system of the core 101 includes: silica (SiO ₂ ), erbium trioxide (Er ₂ O ₃ ), ytterbium trioxide (Yb ₂ O ₃ ), lanthanum trioxide (La ₂ O ₃ ), phosphorus pentoxide (P ₂ O ₅ ), trioxide Aluminum oxide (Al ₂ O ₃ ) and component B, wherein component B can be germanium dioxide (GeO ₂ ) or fluoride ions (F ^- ). It is easy to implement and helps ensure the stability of the fiber core 101.

Taking the doping ion A as a germanium ion as an example, in the process of passing gas containing silicon tetrachloride (SiCl ₄ ) to form the SiO ₂ core 101, erbium trichloride (ErCl ₃ ) and trichloride can be mixed and added. Ytterbium (YbCl ₃ ), lanthanum trichloride (LaCl ₃ ), phosphorus oxychloride (POCl ₃ ), aluminum trichloride (AlCl ₃ ), germanium tetrachloride (GeCl ₄ ), thus making the SiO ₂ core 101 Doped with Er ³⁺ , Yb ³⁺ , La ³⁺ , P ⁵⁺ , Al ³⁺ , and Ge ⁴⁺ , the component system of the core 101 is SiO ₂ -Er ₂ O ₃ -Yb ₂ O ₃ - La ₂ O ₃ -P ₂ O ₅ -Al ₂ O ₃ -GeO ₂ .

Figure 2 is a single-stage full-wave amplification gain spectrum diagram in the extended C-band of a doped optical fiber provided by an embodiment of the present application.

Among them, the doping concentration of aluminum ions is 0.5wt%-12wt%. It should be noted that wt% refers to the mass percentage, that is, the mass percentage of doped aluminum ions in the fiber core 101 is 0.5%-12% (including 0.5% and 12%), the doping concentration of Al ₂ O ₃ in the component system of the fiber core 101 is also about 0.5wt%-12wt%. A higher concentration of aluminum ions is achieved. The increase in the doping concentration of aluminum ions makes the effect on the coordination field of erbium ions stronger, further expanding the gain bandwidth of the doped optical fiber 100 and realizing the extended C of the doped optical fiber 100. Broadband gain.

For example, as shown in Figure 2, a doped optical fiber 100 with an aluminum ion doping concentration within the above range has a large gain in the extended C-band 1522nm-1572nm, a strong gain performance, and a gain bandwidth greater than or equal to 50nm, effectively increasing the gain bandwidth of the doped optical fiber 100 and realizing the wide spectrum gain of the doped optical fiber 100 in the extended C-band.

As shown in Figure 2, when the doped fiber 100 is doped with a higher concentration of aluminum ions, its gain spectrum curve has little fluctuation in the extended C-band range of 1522nm-1572nm and tends to be flat, that is, a higher concentration of aluminum is achieved. The doping of ions can effectively improve the gain flatness of the doped optical fiber 100 in the extended C-band and improve the performance of the amplifier.

Among them, the doping concentration of aluminum ions can be greater than or equal to 8wt%. For example, the mass percentage of aluminum ions doped in the fiber core 101 is greater than or equal to 8%, achieving high concentration doping of aluminum ions, further ensuring that the fiber core 101 has a relatively high increase in width The gain bandwidth realizes the broad spectrum gain of the doped optical fiber 100 in the extended C-band 1522nm-1572nm.

Figure 3 is a single-stage full-wave amplification gain spectrum diagram in the extended L-band of a doped optical fiber provided by an embodiment of the present application.

In the embodiment of the present application, the doping concentration of phosphorus ions is 0.5wt%-15wt%, that is, the mass percentage of doped phosphorus ions in the fiber core 101 is 0.5%-15% (including 0.5% and 15%) , the doping concentration of P ₂ O ₅ in the component system of the fiber core 101 is also about 0.5wt%-15wt%. A higher concentration of doping of phosphorus ions is achieved. The increase in the doping concentration of phosphorus ions can further enhance its effect on the coordination field of erbium ions and further expand the gain bandwidth of the doped optical fiber 100 to the L-band. , and achieve broad spectrum gain of the doped optical fiber 100 in the extended L-band.

For example, as shown in Figure 3, when the doping concentration of phosphorus ions in the doped optical fiber 100 is in the range of 0.5wt%-15wt%, the doped optical fiber 100 has a large gain in the extended L-band 1575nm-1627nm. The performance is strong, and its gain bandwidth is greater than or equal to 52 nm, which further effectively increases the gain bandwidth of the doped optical fiber 100 and realizes the wide spectrum gain of the doped optical fiber 100 in the extended L-band.

In addition, as shown in Figure 3, when the doping concentration of phosphorus ions in the doped optical fiber 100 is relatively high, its gain spectrum curve is relatively gentle in the extended L-band range of 1575nm-1627nm, that is, the doping of higher concentrations of phosphorus ions is achieved. The hybridization helps to improve the gain flatness of the doped optical fiber 100 in the extended L-band and improves the performance of the amplifier.

Among them, the doping concentration of phosphorus ions can be greater than or equal to 10wt%, that is, the mass percentage of phosphorus ions doped in the fiber core 101 is greater than or equal to 10%, achieving high-concentration doping of phosphorus ions, further ensuring that the fiber core 101 has a relatively high The wide gain bandwidth enables the doped optical fiber 100 to achieve broad spectrum gain in the extended L-band 1575nm-1627nm.

In the embodiment of the present application, the doping concentration of erbium ions may be 200 ppm-2000 ppm, where ppm refers to parts per million of mass, that is, the mass percentage of erbium ions doped in the fiber core 101 is in parts per million. In the range of 200 to 2000 parts per million (including 200 parts per million and 2000 parts per million), the doping concentration of Er ₂ O ₃ in the component system of the core 101 is also about 200 ppm-2000 ppm. Due to the doping of at least one of ytterbium ions and lanthanum ions, the doping concentration of erbium ions is increased, making the doping concentration of erbium ions greater than or equal to 200 ppm, achieving a higher concentration doping of erbium ions and ensuring doping Improvement of gain performance and gain bandwidth of optical fiber 100.

Among them, the doping concentration of erbium ions is between 200ppm and 2000ppm, which can reduce or avoid concentration quenching caused by excessive erbium ion concentration and thus affecting the doped fiber while ensuring a high doping concentration of erbium ions. 100 gain performance.

Among them, the doping concentration of ytterbium ions is 200 ppm-4000 ppm, that is, the mass percentage of ytterbium ions doped in the fiber core 101 is in the range of 200 parts per million to 4000 parts per million (including 200 parts per million and 100 parts per million). 4000 parts per 10,000), the doping concentration of Yb ₂ O ₃ in the component system of the fiber core 101 is also about 200ppm-4000ppm. Making the doping concentration of ytterbium ions co-doped with erbium ions within the above range can more effectively reduce the clusters of erbium ions, thereby increasing the doping concentration of erbium ions in the fiber core 101 .

Among them, the doping concentration of lanthanum ions is 0.5wt%-7wt%, that is, the mass percentage of lanthanum ions doped in the fiber core 101 is in the range of 0.5%-7% (including 0.5% and 7%). The fiber core 101 The doping concentration of La ₂ O ₃ in the component system is also about 0.5wt%-7wt%. Setting the doping concentration of lanthanum ions co-doped with erbium ions to the above range can further reduce the clusters of erbium ions, which helps to increase the doping concentration of erbium ions in the fiber core 101 .

The concentration of the doping ions A may be 0.1wt%-1wt%, that is, the mass percentage of the doping ions A doped in the fiber core 101 is 0.1%-1% (including 0.1% and 1%), so as to dope the ions A is germanium ion, for example. The doping concentration of GeO ₂ in the component system of the fiber core 101 is also about 0.1wt%-1wt%. On the premise of ensuring that the refractive index of the doped optical fiber 100 can be effectively adjusted, the deterioration of the doping and luminescence characteristics of erbium ions caused by too high a doping concentration of germanium ions or fluorine ions is reduced or avoided.

Embodiments of the present application also provide a method for preparing doped optical fibers, as shown in Figure 4. The method includes:

S101: Tubular prefabricated parts available.

The preform can be used to form the cladding 102 in subsequent steps. Therefore, the molding material of the preform can be the same as the molding material of the cladding 102 . For example, the molding material of the prefabricated part can be silica, the prefabricated part can be a glass tube, or the prefabricated part can also be a quartz tube. Of course, in some other examples, the prefabricated part can also be made of other materials. Tubular structure.

In the embodiment of the present application, the tube wall of the prefabricated part may be thin. For example, the prefabricated part may be a thin-walled quartz tube, and its wall thickness may be 1.5 mm to 3 mm.

Step S101 may also include: cleaning the preform.

The preform is cleaned to remove impurities on the preform to avoid adverse effects on the subsequently formed doped optical fiber. Specifically, the cleaning method can be to use chemical agents to clean the preform. For example, hydrofluoric acid can be used to clean the quartz tube.

Of course, in some other examples, the prefabricated parts can also be cleaned in other ways.

After cleaning the preform, step S101 may also include polishing the preform.

Specifically, the preform can be polished at high temperature, and the polishing gas can be sulfur hexafluoride (SF ₆ ). Of course, in some other examples, the polishing gas can also be other gases.

S102: Pour mixed gas into the preform to deposit and form a doped core layer. The mixed gas includes at least one of ytterbium ions and lanthanum ions, erbium ions, silicon ions, phosphorus ions, aluminum ions and doping ions. A.

That is to say, while the core layer is deposited and formed, the above-mentioned doping ions are doped into the core layer. The mixed gas includes main component ions used to form the fiber core layer, such as silicon ions, so that at least one of ytterbium ions and lanthanum ions, erbium ions, phosphorus ions, and aluminum are incorporated while depositing to form the fiber core layer. ions and doping ions A, eventually forming a doped core layer on the inner wall of the preform.

For example, if the doping ions include ytterbium ions and lanthanum ions, the mixed gas may include silicon tetrachloride (SiCl ₄ ) to form the SiO ₂ core layer. The mixed gas may also include compounds with the above-mentioned doping ions. For example, taking the doping ion A as a germanium ion, the mixed gas may include erbium trichloride (ErCl ₃ ), ytterbium trichloride (YbCl ₃ ), Lanthanum trichloride (LaCl ₃ ), phosphorus oxychloride (POCl ₃ ), aluminum trichloride (AlCl ₃ ), and germanium tetrachloride (GeCl ₄ ) are used to form the SiO ₂ core layer during deposition. The SiO ₂ core layer is doped with Er ³⁺ , Yb ³⁺ , La ³⁺ , P ⁵⁺ , Al ³⁺ , and Ge ⁴⁺ to obtain a doped core layer, thereby making the final core system The composition is SiO ₂ -Er ₂ O ₃ -Yb ₂ O ₃ -La ₂ O ₃ -P ₂ O ₅ -Al ₂ O ₃ -GeO ₂ , where the doping concentration of Al ³⁺ can be 0.5wt%-12wt %.

The doped core layer is formed by passing a mixed gas into the preform. In other words, during the process of passing in a gas containing silicon tetrachloride (SiCl ₄ ) to deposit the SiO ₂ core, the doped core layer can be mixed and passed into the preform. At least one of the above Yb ³⁺ and La ³⁺ , Er ³⁺ , P ⁵⁺ , Al ³⁺ , and a mixed gas of doping ions such as doping ion A, thereby forming the core layer during deposition Achieving doping will, on the one hand, help improve the uniformity of the doped core layer distribution and improve the performance of the core. On the other hand, doping ions enter the fiber core layer system in the form of gas and achieve doping, which can effectively improve the uniformity of the distribution of the above-mentioned doping ions in the fiber core layer, further increase the doping concentration, and help Improvement of gain performance and gain bandwidth of doped optical fiber.

Specifically, a mixed gas can be passed into the preform, and a doped core layer can be deposited in the preform through modified chemical vapor deposition (MCVD). The chemical vapor deposition method The technology is relatively mature and has good practicality.

For example, a mixed gas can be introduced into the cleaned and polished preform, and the mixed gas can include: oxygen-carrying silicon tetrachloride, oxygen-carrying phosphorus oxychloride, oxygen-carrying germanium tetrachloride, and inert gas carrying trichloride. At least one of ytterbium and lanthanum trichloride, erbium trichloride carried by the inert gas, and aluminum trichloride carried by the inert gas, then undergo a chemical reaction under high temperature conditions, and deposit on the inner wall of the preform to form an oxide containing doped ions. The core layer of the object.

Among them, chemical vapor deposition is used to form a doped core layer on the inner wall of the preform. The specific conditions of the deposition process can be selected and set according to actual needs. Specifically, for example, the deposition temperature can be 1600°C-2050°C, and the number of deposited layers can be 2-5 layers, etc.

In addition, in some examples, in the above-mentioned step S102, high-purity helium can be introduced during the entire process of depositing and forming the doped core layer to quickly equalize the temperature field and provide inert gas protection.

S103: Form a preform and draw the preform to form a doped optical fiber. The doped core layer forms the core of the doped optical fiber, and the doping concentration of aluminum ions in the core can be 0.5wt%-12wt%. .

Specifically, forming the preform in step S103 may include:

The shrink rod is the above-mentioned preform with a doped fiber core layer deposited on it. In other words, the preform obtained after step S102 is subjected to high temperature treatment to melt and shrink it into a core rod or preform rod at high temperature. Specifically, the melting temperature range can be 1800°C to 2300°C.

For the core rod or preform that does not meet the final fiber core-to-cladding ratio, an outer tube of appropriate size is set outside the cylinder and melted at high temperature to form the finished preform, so that it can meet the final requirement after subsequent wire drawing. The target fiber core-to-cladding ratio. The temperature range of melting in this step may be 2000°C to 2300°C.

The outer tube wall of the outer tube and the tube wall of the prefabricated part are jointly used to form the cladding 102. The molding material of the outer tube and the prefabricated part can be the same, for example, both can be quartz tubes.

In step S103, before drawing the preform to form a doped optical fiber, the method may further include:

Attach the handle bar to the preform and flame polish it.

Among them, the prefabricated rod is connected to the handle rod for easy operation for subsequent polishing processing.

The specific conditions for polishing the preform can be selected and set according to actual needs. For example, the polishing temperature may be 1800°C to 1900°C.

In step S103, the preform is drawn to form a doped optical fiber. Specifically, the preform is drawn into a doped optical fiber in a high-temperature melted state, and the core layer located in the preform forms the core 101 of the doped optical fiber. The tube wall of the sheathed outer tube and the tube wall of the preform form the cladding 102 of the optical fiber.

Among them, the specific conditions of the drawing operation can be selected and set according to actual needs. For example, the drawing temperature can be 2050°C-2150°C, and the drawing speed can be 60m/min-100m/min.

After completing the above step S103, the method may also include:

A first coating layer is applied to the outer periphery of the cladding layer, and a second coating layer is applied to the outer periphery of the first coating layer.

The first coating layer 103 and the second coating layer 104 may be made of the same molding material. For example, the first coating layer 103 and the second coating layer 104 may both be UV-cured acrylic resin.

The doped optical fiber 100 can be formed through the above steps. This method has mature technology and high practicability, and helps to improve the uniformity of doping ions in the doped optical fiber, and helps to further improve the performance of the doped optical fiber. . The gain bandwidth of the doped optical fiber formed by this method covers 1530nm-1560nm, which is consistent with the commonly used C-band of optical fiber, so that the gain characteristics of the doped optical fiber can be effectively utilized. Moreover, ytterbium ions and lanthanum ions At least one co-doping ion as erbium ions can reduce the clustering of erbium ions and increase the solubility of erbium ions, thereby helping to increase the doping concentration of erbium ions and further improving the gain performance and gain bandwidth of doped optical fibers. .

Moreover, aluminum ions and phosphorus ions can change the coordination environment of erbium ions, thereby promoting the energy level splitting of erbium ions, expanding the gain bandwidth of doped optical fibers, and improving the gain bandwidth of doped optical fibers.

At the same time, the doping concentration of aluminum ions is 0.5wt%-12wt%, which achieves high-concentration doping of aluminum ions, which helps to further expand the gain bandwidth of doped optical fibers and achieves a wide range of doped optical fibers in the extended C-band. Spectral gain. In addition, the doping concentration of phosphorus ions can be 0.5wt%-15wt%, achieving high-concentration doping of phosphorus ions, which can further expand the gain bandwidth and achieve broad-spectrum gain of the doped optical fiber in the extended L-band.

The preparation method of a doped optical fiber provided in the embodiment of the present application is described in detail below with specific examples.

Example 1

Taking the preform as a quartz tube and the doping ions in the doped fiber core as erbium ions, ytterbium ions, lanthanum ions, phosphorus ions, aluminum ions and germanium ions as an example, the specific preparation method of the doped fiber core is as follows:

Clean the quartz tube and perform high-temperature polishing on the quartz tube.

A mixed gas is introduced into the quartz tube. The mixed gas includes: oxygen carries SiCl ₄ , POCl ₃ , GeCl ₄ , and inert gas carries ErCl 3 , YbCl ₃ , LaCl ₃ , and AlCl ₃ , and is deposited at high temperature to form a doped core layer. .

The rod is shrunk at high temperature to form a core rod or preform, and a quartz tube of appropriate size is placed outside the core rod according to the target core-to-pack ratio, and is melted and shrunk at high temperature to form the finished preform.

Connect the handle rod to the preform, polish the preform, and then draw the preform at high temperature to form a doped optical fiber. The doped core layer forms the core of the optical fiber, and the quartz tube wall forms the envelope of the optical fiber. layer. The system components of the fiber core are: SiO ₂ -Er ₂ O ₃ -Yb ₂ O ₃ -La ₂ O ₃ -P ₂ O ₅ -Al ₂ O ₃ -GeO ₂ , where the doping of Er ³⁺ in the core The doping concentration is 200ppm-2000ppm, the doping concentration of Yb ³⁺ is 200ppm-2000ppm, the doping concentration of La ³⁺ is 0.5wt%-7wt%, the doping concentration of Al ³⁺ is 8wt%-12wt%, P ⁵ The doping concentration of ^Ge 4+ is 0.5wt%-10wt%, and the doping concentration of Ge ⁴⁺ is 0.1wt%-1wt%.

A first coating layer and a second coating layer are applied sequentially on the outer periphery of the cladding.

The doped optical fiber obtained by the above method can achieve wide-spectrum gain in the extended C-band, and has higher gain performance and wider gain bandwidth.

Example 2

A mixed gas is introduced into the quartz tube. The mixed gas includes: oxygen carrier SiCl ₄ , POCl ₃ , GeCl ₄ , inert gas carrier ErCl ₃ , YbCl ₃ , LaCl ₃ , and AlCl ₃ , and is deposited at high temperature to form doped fibers. core layer.

Connect the handle rod to the preform, polish the preform, and then draw the preform at high temperature to form a doped optical fiber. The doped core layer forms the core of the optical fiber, and the quartz tube wall forms the envelope of the optical fiber. layer. The system components of the fiber core are: SiO ₂ -Er ₂ O ₃ -Yb ₂ O ₃ -La ₂ O ₃ -P ₂ O ₅ -Al ₂ O ₃ -GeO ₂ , where the doping of Er ³⁺ in the core The impurity concentration is 200 ppm-2000ppm, the doping concentration of Yb ³⁺ is 200ppm-2000ppm, the doping concentration of La ³⁺ is 0.5wt%-7wt%, the doping concentration of Al ³⁺ is 0.5wt%-8wt%, the doping concentration of P ⁵⁺ The doping concentration is 10wt%-15wt%, and the doping concentration of Ge ⁴⁺ is 0.1wt%-1wt%.

The doped optical fiber obtained by the above method can achieve wide-spectrum gain in the extended L-band, and has higher gain performance and wider gain bandwidth.

It should be noted that the numerical values and numerical ranges involved in the embodiments of this application are approximate values. Affected by the manufacturing process, there may be a certain range of errors. Those skilled in the art can consider these errors to be negligible.

An embodiment of the present application also provides an optical fiber amplifier. Specifically, the optical fiber amplifier may include a casing and any of the above-mentioned doped optical fibers, wherein the doped optical fiber is disposed in the casing.

Of course, in some other examples, the fiber amplifier may also include other functional devices, such as pump laser devices, optical passive devices, control units, optical isolation devices, optical fiber connection devices, etc.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, but not to limit them; although the embodiments of the present application have been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art It should be understood that the technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the embodiments of the present application. The scope of the technical solutions of each embodiment.

Claims

A doped optical fiber, characterized in that it includes a fiber core containing doped ions;

The doping ions include at least: at least one of ytterbium ions and lanthanum ions, erbium ions, phosphorus ions, aluminum ions, and doping ions A, wherein the doping ions A are germanium ions or fluorine ions;

The doping concentration of the aluminum ions is 0.5wt%-12wt%.
The doped optical fiber according to claim 1, characterized in that the doping concentration of the phosphorus ions is 0.5wt%-15wt%.
The doped optical fiber according to claim 1 or 2, characterized in that the component system of the core includes: at least one of ytterbium trioxide and lanthanum trioxide, erbium trioxide, silicon dioxide , phosphorus pentoxide, aluminum oxide and component B, the component B is germanium dioxide or fluoride ions.
The doped optical fiber according to any one of claims 1 to 3, characterized in that the doping concentration of the aluminum ions is greater than or equal to 8 wt%.
The doped optical fiber according to any one of claims 1 to 4, characterized in that the doping concentration of the phosphorus ions is greater than or equal to 10 wt%.
The doped optical fiber according to any one of claims 1 to 5, characterized in that the gain bandwidth of the doped optical fiber in the C-band is greater than or equal to 50 nm, and the C-band includes 1522nm-1572nm.
The doped optical fiber according to claim 2, characterized in that the gain bandwidth of the doped optical fiber in the L-band is greater than or equal to 52 nm, and the L-band includes 1575nm-1627nm.
The doped optical fiber according to any one of claims 1 to 7, characterized in that the doping concentration of the erbium ions is 200 ppm-2000 ppm.
The doped optical fiber according to any one of claims 1 to 8, characterized in that the doping concentration of the ytterbium ions is 200 ppm-4000 ppm.
The doped optical fiber according to any one of claims 1 to 9, characterized in that the doping concentration of the lanthanum ions is 0.5wt%-7wt%.
The doped optical fiber according to any one of claims 1 to 10, characterized in that the doping concentration of the doping ions A is 0.1wt%-1wt%.
The doped optical fiber according to any one of claims 1 to 11, further comprising a cladding, a first coating and a second coating, the cladding wrapping the outer periphery of the core, the first The coating wraps the outer periphery of the cladding layer, and the second coating wraps the outer periphery of the first coating.
A method for preparing doped optical fiber, characterized in that the method includes:

Tubular prefabricated parts are available;

A mixed gas is passed into the preform to deposit and form a doped core layer. The mixed gas includes at least one of ytterbium ions and lanthanum ions, erbium ions, silicon ions, phosphorus ions, aluminum ions, and doped core layers. Doping ion A, the doping ion A is germanium ion or fluoride ion;

Forming a preform and drawing the preform to form a doped optical fiber, the doped core layer forming the core of the doped optical fiber, and the doping concentration of the aluminum ions in the core 0.5wt%-12wt%.
The preparation method according to claim 13, characterized in that, introducing a mixed gas into the preform to deposit and form a doped core layer includes: forming the doped core layer in the preform by a chemical vapor deposition method. The doped fiber core layer.
An optical fiber amplifier, characterized in that it includes at least a casing and the doped optical fiber according to any one of claims 1 to 12, and the doped optical fiber is arranged in the casing.